New Interface Module Installed - SMART

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737-800 OEM flaps gauge. A new interface module was designed to incorporate the 400 hertz needed to power the gauge

The installation of an OEM flaps gauge to the simulator was the catalyst to the design and development of an additional interface module. 

The module, called SMART is a platform to primarily accommodate the various components necessary to configure and drive the flaps gauge.

SMART has also been used to accommodate the interface cards needed to operate the following;

The SMART module has been discussed in a separate section as a subset to the Interface Module section.

10 Mile ARC to VOR 30 Approach - Hobart, Tasmania Australia (YMHB)

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Approach chart depicting VOR 30 Approach to YMHB.  Important points to note are: initial approach courses to intercept the arc (295 & 334), the D10 HB arc, the altitude increments of 4000, 3000 and at 7 miles, 2400, and the Initial Approach Fix (IAF) and speed of 210 kias

Recently, I flew from Brisbane to Hobart and the pilot flying made a different style of approach to what normally is made at this airport.  After landing, I approached the pilots and queried the approach.  The Captain stated that he had decided to fly a semi-automated VOR approach along an arc to land at runway 30. 

The reason being, that Air Traffic Control (ATC) had warned them of turbulent conditions near the airport.  He commented that in such conditions, he felt more confident using the older style arc approach using LNAV/VNAV with Speed Intervention (SPD INTV) engaged, with a transition to Vertical Speed and VOR once on final.

The First Officer stated that this was the first time he had seen an arc being used to set-up for a VOR approach.  He said that usually they use ILS into RWY 12 or RNAV into RWY 30.  He commented that the only time he had made a VOR approach was during simulator training, and then he would probably only use such an approach, if the ILS was inoperative or there was an issue with RNAV.

The use of this approach is a prime example of the variation offered to pilots in relation to how they fly and land the Boeing 737. 

Screen Images

Several screen captures from the Instructor Station, CDU and Navigation Display (ND) which I hope will make it easier to understand this post.  The avionics suite used is ProSim737 distributed by ProSim-AR.  Note that some of the mages are not sequential as I captured the images over two simulator sessions.

How To Set-Up An Arc

To set-up an approach using an arc is very easy.  

The following example is for Hobart, Tasmania Australia (YMHB).  The instructions assume that you are conversant with operating the CDU and have a basic understanding of its use.  

Essentially, an arc is using a Place/Bearing/Waypoint to define an arc around a point at a set distance.  The distance between each of the generated waypoints along the arc, is at the discretion of the flight crew.

Approach Charts

To determine the correct distance to create the arc, the approach chart for the airport should be consulted.  The chart, in addition to providing this information, will also aid you in decided where to place the final waypoint (if wanted) along the approach course.

In this example, the YMHB VOR 30 approach states that the aircraft must fly an arc 10 miles from the airport between an altitude of 4000 and 3000 feet before descending to be at 2400 feet 7 miles from the runway  threshold.

The approach chart depicted is provided by Lufthansa Systems (LIDO/FMS) distributed by Navigraph. 

CDU Instructions

(i)    Open the FIX page and type in the scratchpad the airport code (YMHB).  After uploading, type the distance (/10 miles).  This will create a green-dotted citcle around YMHB with a radius of 10 miles.

(ii)    Open the LEGS page and type into the scratchpad the airport code (YMHB).  Immediately following YMHB, type the required radial1 (in degrees) from the airport that you wish the initial waypoint to be generated.  Follow this with a slash and type in the distance from the airport (YMHB340/10).  

This will generate a waypoint 10 miles from YMHB on the 340 radial.  This is the waypoint from which you will begin to build your arc.  

Obviously, the radial you use to define the location of your first waypoint will depend upon the bearing that you are flying toward the airport.

(iii)    To Generate the ARC you must repeat the above process (ii) changing the radial by 10 degrees (or whatever you believe is needed) to generate the required waypoints around the arc at 10 miles from the airport.  As an example: YMHB320/10, YMHB340/10, YMHB000/10 and so forth until the arc is built.

As you upload each of the radials you will note that the name for the waypoint is changed to a sequential number specific to each waypoint.  As an example; the above waypoints will each be named YMH01, YMH02 and YMH03.

If you make a mistake, you can delete a waypoint and start again; however, realize that the sequential numbers will not be in order.  This is not an issue (it is only a number) but it is something be aware of.

In our example, the VOR approach is for runway 30.  Therefore; your final waypoint on the arc will be YMHB121/10.  Prior to reaching this waypoint, if flying manually, begin the right hand turn to intercept the approach on the 121 radial (bearing 300 degrees).

A Note About /-+

The more observant will note that the distances in the example above do not utilise the /+ key before the distance (YMHB340/+10).  When entering the distance it can be with or without the + key.  

Variation

Before going further, there are many ways to fly the B737.  The method selected is at the discretion of the pilot in command and is dependent upon airline preferences, environmental conditions, and pilot experience.  This statement was stressed to me when I spoke with the Captain of the aircraft.

Often an approach will incorporate a number of automated systems including VNAV, LNAV, Vertical Speed, Level Change, VOR Localizer and old fashioned manual VFR flying.  In most cases the particular approach will be programmed into the CDU, at the very least for situational awareness.  However, the CDU does not have to be used and often a step down approach is a good way to maintain flying skills and airmanship.

Handy Hints

The following hints will assist with situational awareness and in allowing the aircraft to be guided by the autopilot to a point to which manual flight can commence.

If you carefully study the approach chart for YMHB VOR 30, you will note that the altitude the aircraft should be at when at 7 miles from the threshold should be 2000 feet.  The chart also depicts the letter D at this point meaning that a continuous descent can be made this point.

Hint One - visual descent point (VDP)

To make the transition from the arc to the approach easier, create a waypoint at the 7 mile point from the airport along the radial used for the approach (YMHB121/7).  Using a waypoint allows the aircraft’s Lateral Navigation (LNAV) to be used.  This type of waypoint is usually referred to as a Visual Descent Point (VDP).

When the waypoint at 7 miles from the threshold is reached, a transition to manual flying can commence, or Vertical Speed can be used to maintain a 3 degree glidepath (GP) while following the VOR.  Remember to change the EFIS from MAP to VOR so you can use the VOR indicator during the approach.

Hint Two - extend runway line

Assuming you have not inserted an approach into the CDU, an aid to increase situational awareness is to select the correct runway from the CDU and enter a distance that the runway line is to be extended from the threshold.

To do this, select runway 30 from the ARRIVALS (ARR) page in the CDU (RWY30) and type the numeral 7 (or whatever distance you require) into the scratchpad and upload.  This will extend the green line from the runway threshold to the previously generated waypoint at 7 miles.  Ensure you clean up any discontinuity (if observed) in the LEGS page.

This enables three things:

  1. The generation of a 3 degree glidepath (GP) from the distance entered (example is 7 miles) to the runway threshold.

  2. It enables LNAV (even if the autopilot is not engaged) to continue to provide the Flight Director (FD) with heading information during the approach, and 

  3. It enables the Navigation Performance Scales (NPL) on the Pilots Flight Display (PFD) to provide glidepath (GP) guidance (assuming that the correct runway or approach is selected in the CDU and NPL is enabled within the ProSim737 avionics suite).

UPPER LEFT: Screen capture from the instructor station PFD and ND for the approach into YMHB.  The aircraft, after turning right from the 10 mile arc, is aligned with the 121 radial approaching the waypoint YMH07 (the WP entered at the 7 mile point).  LNAV is engaged and the aircraft is being controlled by the autopilot.  As RWY 30 was inserted into the route, the Navigation Performance Scales (NPS) show Glidepath (GP) data in the Primary Flight Display (PFD).  Note that the EFIS is still on MAP and is yet to be turned to VOR.  In real life, VOR would have been selected earlier (click to enlarge).

LOWER LEFT:  The transition from LNAV to VOR has occurred and the autopilot and autothrottle are not controlling the aircraft. The aircraft is on short final with gear down, flaps 30 and the airspeed is slowly decaying to VREF+5. 

The EFIS has been changed from MAP to VOR to allow manual tracking using the VOR needle. The NPS show good vertical alignment with a lateral left offset; the VOR indicator confirms this.  The Flight Mode Annunciator (FMA) displays LNAV (although the autopilot is disengaged) and the Flight Director (FD) and NPS show glidepath (GP) data.  The Flight Path Vector (FPV) symbol shows a continuous descent at roughly 3 degrees.  The altitude window and heading on the MCP has been set to the appropriate missed approach (4200/300).  Click image to enlarge.

Do Not Alter Constraints

As alluded earlier, there are many ways to accomplish the same task.  However, DO NOT alter any constraints indicated in the CDU if an approach is selected and executed.  CDU generated approaches have been standardised for a reason.

Finding the Correct Radial/Bearing to Build Your Arc

Finding the correct bearing to use on the arc can be challenging for those less mathematically inclined.  An easy method is to use one of the two MCP course selector knobs.  

Rotate the knob until the green dotted line on he Navigation Display (ND) lies over the area of the arc that you wish the waypoint to be created.  Consult the MCP course selector window - this is the figure you place in the CDU.  Next, rotate the knob a set number of degrees and repeat the process.  You can also consult the data displayed along the course indicator line on the Navigation Display (ND). 

When you build the arc, ensure you have set the EFIS to PLN (plan).  PLN provides more real estate to visualize the approach on the Navigation Display (ND).  You can use STEP in the LEGS page to cycle through the waypoints to ensure you have an appropriate view of the surrounding area.

Important Points

  • Always double check the Place/Bearing/Waypoint entries in the CDU and in the ND (PLN) before executing.  It is amazing how easy discrepancies can occur.

  • Always check the approach plate for the approach type you are intending to make.  Once again, mistakes are easy to make.

  • If using VNAV, double check all speed and altitude constraints to ensure compliance with the approach chart and situation (some airlines promote the use of the speed intervention button (SPD INTV) to ensure that appropriate speeds are maintained).

  • If need be, select the approach (ARR) in the CDU to provide added situational awareness.

Images

The following are screen captures from the instructor station CDU and Navigation Display (ND).  Ignore altitude and speed constraints as these were not set-up for the example. Click each images to enlarge.

LEFT: Circular FIX ring has been generated around YMHB at 10 mile point.  The arc waypoints will be constructed along this line.

LEFT:  Various waypoints have been generated along the 10 mile fix line creating an arc.  The arc ends at the intersection with the 212 radial for the VOR 30 approach into YMHB.  The route is in plan (PLN) view and is yet to be executed.

LEFT:  The constructed arc as seen in MAP view.  From this view it is easy to establish that the aircraft is approaching TTR and once reaching the 10 mile limit  defined by the 10 mile FIX (green-coloured dotted circle), the aircraft will turn to the left to follow the arc waypoints until it intersects with the 121 radial.

LEFT:  This image depicts the waypoint generated at 7 mile from the threshold (YMHB121/7).  This waypoint marks the point at which the aircraft should be on the 121 radial to VOR 30 and at 2400 feet altitude (according to the VOR 30 approach plate.

LEFT:  RWY 30 has been selected from the arrivals (ARR) page.  This displays the guidepath (GP) assistance. it also generates a runway line extending from the threshold to 7 miles out; the same distance out from the threshold that the final waypoint was generated.

The course line is coloured pink indicating that LNAV is enabled and the aircraft is following the programmed route. 

At the final waypoint (YM10) the autopilot (if used) will be disengaged and the aircraft will be flown manually to the runways using the VOR approach instrumentation and visual flight rules (VFR).  The EFIS will be changed from MAP to VOR.  LNAV will remain engaged on the MCP to ensure that the NPL indications are shown on the PFD.  The NDL indicators provide glidepath (GP) guidance that is otherwise lacking on a VOR approach.

Final Call

I rarely use automated systems during landing, unless environmental conditions otherwise dictate.  I prefer to hand fly the aircraft where possible during the approach phase, and often disengage the autopilot at 5000 feet.  If flying a STAR and when VNAV/LNAV is used, I always disengage the autopilot no later than 1500 feet.  This enables a safe envelope in which to transition from automated flight to manual flight.

Using an arc to fly a VOR approach is enjoyable, with the added advantage that it provides a good refresher for using the Place/Bearing/Waypoint functionality of the CDU.

Additional articles that address similar subjects are:

Glossary

  • CDU – Control Display Unit (aka Flight Management Computer (FMC).

  • EFIS – Electronic Flight Instrument System.

  • LNAV – Lateral navigation.

  • RADIAL/BEARING – A radial radiates FROM a point such as a VOR, whilst a bearing is the bearing in degrees TO a point.  The bearing is the direction that the nose of the aircraft is pointing.

  • VNAV – Vertical Navigation.

Throttle Quadrant Rebuild - Four Speed Stab Trim and Stab Trim Indicator Tabs

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Captain-side stab trim wheel with manual trim handle extended.  The white line on the trim wheel is an aid to indicate that the trim wheels are rotating

This post will document several changes that have been made to enable the stab trim wheels to utilise four speeds.  I will also discuss several problems that were encountered and their solution.  Finally, I will provide some possible reasons for the erratic behavior of the stab trim indicator tabs.

In the previous throttle unit, the power to rotate the trim wheels was from a inexpensive 12 Volt pump motor, and the forward and aft rotation speed of the stab trim wheels was controlled by an I/O card.  The system worked well, but the single speed was far from realistic.

The upgrade to the throttle quadrant enables the stab trim wheels to rotate at four speeds which are identical to the speeds observed in a Boeing aircraft.  The speed is controlled by three adjustable speed controller cards, five relays and a Phidget 0/0/8 interface card – all of which are mounted within the Throttle Interface Module (TIM).  

To generate the torque required to rotate the trim wheels at varying speeds, the pump motor was replaced with an encoder capable 12 volt dual polarity brush motor.  The replacement motor is mounted on a customized bracket attached to the inside frame of the throttle unit.  This style of motor is often used in the robotics industry.

Boeing Rotation Speed

The speed at which the trim wheels rotate is identical to the Boeing specification for the NG series airframe.  Simply written, it is:

(i)     Manual trim  - speed without flaps (slow speed);

(ii)    Manual trim  - speed with flaps extended (very fast speed);

(iii)   Autopilot trim  - speed without flaps extended (very slow speed); and,

(iv)   Autopilot trim - speed with flaps extended (faster speed than iii but not as fast as ii).

To determine the correct number of revolutions, each trim wheel cycle was measured using an electronic tachometer.  Electronic tachometers are often used in the automobile industry to time an engine by measuring the number of revolutions made by the flywheel.

It is important to understand that it is not the rotation speed of the trim wheels which is important, but more the speed at which the aircraft is trimmed.  With flaps extended, the time taken to trim the aircraft is much quicker than the time taken if the flaps were retracted.

Electric stab trim switch on Captain-side yoke.  Whenever the trim is engaged the stab trim wheels will rotate with a corresponding movement in the stab trim indicator tabs

Is There a Noticeable Difference Between the Four Speeds

There is definitely a noticeable difference between the speed that the trim wheels rotate at their slowest speed and fastest speed; however, the difference is subtle when comparing the intermediate speeds.

Design and Perils of Stab Trim

If you speak to any real-world pilot that flies Boeing style aircraft, they all agree upon a dislike for the spinning of the trim wheels.  The wheels as they rotate are noisy, are a distraction, and in some instances can be quite dangerous, especially if your hand is resting on the wheel and the trim is engaged automatically by the autopilot.  This is not to mention the side handle used to manually rotate the trim wheels, which if left extended, can easily damage your knee, during an automatic trimming operation.

If you look at the Airbus which is the primary rival of Boeing, the trim wheels pale by comparison; they are quiet, rotate less often, and are in no way obtrusive.  So why is this case?

Boeing when they deigned the classic and NG series aircraft did not design the throttle unit anew.  Rather, they elected to build upon existing technology which had changed little since the introduction of the Boeing 707.  This saved the company considerable expense.

Airbus, on the other hand, designed their throttle system from the ground-up and incorporated smaller and less obtrusive trim wheels from the onset.

Interestingly, Boeing in their design of the Dreamliner have revamped the design of the stab trim wheels and the new design incorporates smaller, quieter and less obtrusive trim wheels than in the earlier Boeing airframes – no doubt the use of automated and computer controlled systems has removed the need for such a loud and visually orientated system.

Problems Encountered (Teething Issues)

Three problems were encountered when the trim wheels were converted to use four speeds.  They were:

(i)      Excessive vibration when the trim wheels rotate at the fastest speed;

(ii)     Inconsistency with two of the speeds caused when CMD A/B is engaged; and,

(iii)    Fluttering (spiking) of the stab trim indicator tabs when the electric stab trim switch was engaged in the down position.

Point (i) is discussed immediately below while points (ii) and (iii), which are interrelated, have been discussed together.

(i)    Excessive vibration

When the trim wheels rotate at their highest speed there is considerable vibration generated, which causes the throttle quadrant to shake slightly on its mounts.

Stab trim wheel cog and mechanism (before cleaned) from the First Officer side.  The picture shows some of the internal parts that move (and vibrate) when the trim wheels rotate at very high speeds.  The high and narrow shape of the throttle unit is easily noted

One of the reasons for the excessive vibration becomes obvious when you compare the mounting points for the throttle quadrant in a homemade simulator to those found in a real aircraft – the later has several solid attachment points between the throttle unit, the center pedestal, the main instrument panel (CDU Bay), and the rigid floor of the flight deck. 

In a simulator, replicating these attachment points can be difficult.   Also, the throttle is a relatively high yet narrow structure and any vibration will be exacerbated higher in the structure.

Another reason for the cause of the vibrations is the material used to produce the center pedestal.  In the classic airframe the material used was aluminum; however, in the NG carbon fiber is used, which is far more flexible than aluminum.  Any vibration caused by the rotation of the trim wheels has a tendency to become amplified as it travels to the less rigid center pedestal and then to the floor of the flight deck.

Solution

Solving the vibration issue is uncomplicated – provide stronger, additional, and more secure mounting points for the throttle quadrant and the attached center pedestal, or slow the rotation of the trim wheels to a more acceptable speed.  Another option is to replace the platform’s floor with a heavier grade of steel or aluminum.  This would enable the throttle quadrant and center pedestal to be attached to the floor structure more securely.  However, this would add significant weight to the structure.  In my opinion, a heavy steel floor is excessive.

By far the simplest solution, is to reduce the fastest speed at which the trim wheels rotate.  The rotation speed can be altered, by the turn of the screwdriver, on one of three speed controller cards mounted within the Throttle Interface Module (TIM).

For those individuals using a full flight deck including a shell, the excessive vibration is probably not going to be an issue as the shell provides additional holding points in which to secure the throttle quadrant, MIP and floor structure.

(ii)    Inconsistency with two of the speeds caused when CMA A/B is engaged

When the autopilot (CMD A/B) was selected and engaged on the MCP, the rotation of the trim wheels would rotate at an unacceptable very high speed (similar to run-away trim).  

The mechanics of this issue was that when the autopilot was engaged, the electronics was not activating the relay that is responsible for engaging the speed controller card.

(iii)       Fluttering of the stab trim indicators

When the electric stab trim switch was depressed to the down position, it was observed that the stab trim indicator tabs would often flutter.  Although the fluttering was mechanical and had no bearing on the trim accuracy, or speed at which the aircraft was trimmed, it was visually distracting.

A possible cause for the run-away trim was electromagnetic interference (RF) generated by the high torque of the trim motor.  The higher than normal values of RF were being  ‘picked up’ by the relay card, which were causing the relay to not activate when the autopilot was engaged.  Similarly, the fluttering of the stab trim indicator tabs, was thought to have been caused by RF interfering with the servo motor.

There were several possibilities for RF leakage.

(i)     The high torque of the motor was generating and releasing too much RF;

(ii)    The wire lumen that accommodates the cabling for the throttle is mounted proximal to the servo motor.  If the lumen was leaking RF, then this may have interfered with the operation of the servo motor;

(iii)    The servo motor was not digital and did not have an RF shield attached;

(iv)   The straight-through cable from the Throttle Communication Module (TCM) to the Throttle Interface Module (TIM) did not have RF interference nodules attached to the cable.

Solution

To counter the unwanted RF energy several modifications were made:

(i)     Three non-polarized ceramic capacitors were placed across the connections of the trim wheel motor;

(ii)    The analogue servo motor was replaced with a higher-end digital servo with an RF shield;

(iii)   The straight-through cable between the TIM and TCM was replaced with a cable that included high quality RF nodes; and,

(iv)   The wires from the servo motor were re-routed and shielded to ensure they were not lying alongside the wire lumen.

Manual Trimming

Manual trimming (turning the trim wheels by hand) is not implemented in the throttle quadrant, but a future upgrade may incorporate this feature.

Stab trim cut out switches with spring-loaded cover open on main and closed on autopilot

Cut-out Stab Trim Button (throttle mounted)

In the earlier conversion, the stab trim cut-out toggle was not functional and the toggle had been programmed to switch off the circuit that powers the rotation of the trim wheels.  Having the ability to disconnect the rotation of the trim wheels is paramount when flying at night, as the noisy trim wheels kept family members awake.

The new conversion does not incorporate this feature as the trim cut-out toggle is fully functional.  Rather, a push-to-engage, green-coloured LED button has been installed to the forward side of the Throttle Interface Module (TIM).  The button is connected to a relay, which will either open or close the 12 volt circuit responsible for directing power to the trim motor.

Stab trim indicator tabs (Captain side).  The throttle is from  B737-500.  The indicator tabs on the NG airframe are slightly different - they are more slender and pointed

Stab Trim Indicator Tabs

The method used to convert the stab trim indicators has not been altered, with the exception of replacing the analogue servo with a RF protected digital servo (to stop RF interference).  

LEFT:  Stab trim indicator tabs (Captain side).  The throttle is from  B737-500.  The indicator tabs on the NG airframe are slightly different - they are more slender and pointed (click to enlarge).

To review, a servo motor and a Phidget advanced servo card have been used to enable the stab trim tab indicators to move in synchronization to the revolution and position of the stab trim wheels.  The servo card is mounted within the Throttle Interface Module (TIM) and the servo motor is mounted on the Captain-side of the throttle unit adjacent to the trim wheel.  There is nothing exceptional about the conversion of the stab trim indicator tabs and the conversion is, more or less, a stock standard.

Is Variable Rotation Speed Important to Simulate

As discussed earlier, it is not the actual rotation of the trim wheels that is important, but more the speed at which the aircraft is trimmed.   In other words, the speed at which the trim wheels rotate dictates the time that is taken for the aircraft to be trimmed.  

If the trim wheels are rotating slowly, the movement of the stab trim indicator tabs will be slow, and it will take longer for the aircraft to be trimmed.  Conversely, if the rotation is faster the stab trim indicator tabs will move faster and the aircraft will be trimmed much more quickly.

Stab Trim Wheel Braking

The amperage of the motor is controlled by a motor controller card; a lower amperage ensures the trim wheel rotates slowly while a high amperage causes the trim wheel to rotate faster.  A brake has not been used to stop the rotation of the trim wheel and the wheel rotation stops by inertia or by pushing the electric trim switch (forward or reverse). 

A future upgrade may look at using a dynaclutch system or magnetic braking.  Another method to install braking is to use software rather than a mechanical system.  A motor controller card with a H-Bridge circuit (not available at the time of conversion) could also possibly be used as a brake to stop the trim wheel rotation when the electric trim switch is relesed.

Final Call - is Four-speed Trim Worthwhile

Most throttle conversions implement only one speed for the forward and aft rotation of the trim wheels with the conversion being relatively straightforward.

Converting the throttle unit to use four speeds has not been without problems, with the main issue being the excessive vibration caused by the faster rotation speed.  Nevertheless, it is only in rare instances, such as when the stab trim is engaged for longer than a few seconds at a time, and at the fastest rotation speed, that the vibration becomes an issue.  If the rotation for the fastest speed is reduced, any vibration issues are alleviated – the downside to this being the fastest speed does not replicate the correct Boeing rotation speed.

For enthusiasts wishing to replicate real aircraft systems, there is little excuse for not implementing four-speed trim, however, for the majority of flight deck builders I believe that two-speed trim, is more than adequate.

Video

Below is a short video, which demonstrates the smooth movement of the stab trim indicator tabs from the fully forward to fully aft position.  The video is only intended to present the functionality of the unit and is not to represent in-flight settings.

 

737 Throttle Quadrant trim tab indicator movement

 

Below is short video that demonstrates two of the four rotation speeds used.  In the example, manual trim is has been engaged, beginning with flaps UP, flaps extended, and then flaps UP again.  The rotation speed of the trim wheels with flaps extended (in this case to flaps 1) is faster than the rotation speed with flaps UP.  The video does not reflect in-flight operations and is only to present the functionality of the unit in question.

 

737 Throttle Quadrant variable speed of trim wheels

 

Glossary

  • Electromagnetic Interference (RF) – RF is a disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation  emitted from an external source (see Wikipedia definition).

  • MCP – Mode Control Panel.

  • MIP – Main Instrument Panel.

  • Stab Trim Indicator Tabs – The two metal pointed indicators located on the throttle unit immediately adjacent to the %CG light plate.  If not using a workable throttle unit, then these tabs maybe located in the lower EICAS as a custom user option.

  • Servo Motor – Refers to the motor that powers the stab trim indicator tabs.

  • Trim Motor – Refers to the motor that powers the stab trim wheels.

Book Review - Touch and Go Landings by Jonathan Fyfe

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I read Jonathan Fyfe’s initial on-line tutorial Flying the Circuit in the 737 some time ago.  I was impressed with Fyfe’s writing style which is succinct and easy to read.  As a result I was keen to review his latest publication ‘Touch and Go Landings in the 737 NGX which is a follows on from his original tutorial.

Overview

The book (here on referred to as a guide) is paperback A5 in size, is 135 pages in length and has been printed in colour.  The guide is printed on quality paper and has a glossy-style plastic cover.

As the title of the text eludes, the guide examines in-depth all the aspects needed by a flight crew to successfully fly the Boeing 737 in a standard circuit, including crosswind approaches, missed approaches, engine out operations and rejected takeoffs.   Although the title of the guide may not appear substantive, the guide addresses nearly everything required to conduct a manual/part automated takeoff and landing.

Detail

I was surprised at the volume of information that Fyfe has managed to place in the guide; initially I thought the content appeared rather thin; however, closer examination revealed a wealth of information covering both systems and procedures.  This is in addition, to pictures that demonstrate correct landing technique and diagrams that are well-presented and clear. 

Derated takeoffs, assumed temperature thrust reduction, descent profiles, runway markings, drift calculations and aircraft systems data, which include: spoiler use, flap schedules, flight deck warnings, use the autothrottle and controlled wheel steering – too mention a few, are explained.

Well-written Framwork

Fyfe’s ability as a flight instructor and educator comes to bear in the nature of how he explains the various procedures.  He does not ‘parrot’ procedures, the FCOM or FCTM, but rather adds to this information by his ability to be able to shape the material into a parcel that is easily understood.

Many of the more complicated aspects, such as crosswind approaches, the effects of wind and the balanced field length are explained more clearly by the use of coloured diagrams.  This translates to a guide that is very easy to comprehend allowing the reader to easily apply the information when flying their simulated aircraft. 

Breakdown

The guide is divided into three primary lessons which encompass: standard circuits, missed approach and crosswind circuits and engine out/asymmetrics. 

Each section has three sub-sections.

  • Groundwork;

  • Systems; and,

  • Air Work.  

In groundwork, the theory and methodology for the upcoming lesson is primarily discussed, along with a lesson briefing.  In Systems, the focus is towards pertinent information that relates to the lesson; for example, flap positions, warning horns, autothrottle, N1 calculations and FMA annunciations.  In Air Work, a tutorial-style lesson is presented, in which Fyfe explains the necessary procedures to complete the lesson.   The student (you) can set-up their simulator to mimic the same conditions that Fyfe is flying.  This allows the student to self-evaluate their ability. 

All the sub-sections, but especially so in air work, are augmented by several screenshots depicting aircraft positions and instrument readings.

The lessons revolve around the use of the Boeing 737 NGX produced by Precision Manuals Development Group (PMDG) and Flight Simulator 10 (FSX); however, the information can easily be applied to any simulated B737 that is using a professional avionics suite, such as ProSim737, Sim Avionics, Project Magenta, I-Fly, etc. 

Some enthusiasts may find the guide lacking in that it does not attempt to explain or demonstrate the various automated-style approaches that the B737 is capable of (ILS, VOR, IAN, RNAV, etc.).  Nor does it cover off on climbing to altitude, descent or cruise. Although this knowledge is important, it is not relevant to touch and go takeoffs and landings.

Peer Review

The amount of information, especially on the Internet concerning flying the Boeing 737 aircraft is voluminous; however, a  caveat must be issued in that much of this information has not been peer reviewed and in many instances is not correct.  Although there are numerous monographs available that deal with the Boeing aircraft, these texts are usually very expensive and have not been written with the lay person in mind; often they are technical and assume an inherent level of prior knowledge.  Likewise, the FCOM, FCTM are certainly very helpful documents; however, they have been written for trained flight crews and their method of explanation is often clouded without prior knowledge and experience in aircraft systems. 

In this guide, Fyfe has succeeded in translating much of this information in a concise way that is easy to read and comprehend.

Fly Dubai - steep climb out after touch and go (photograph copyright Mohammadreza Farhadi Aref)

Why Touch and Go - Why Are They Important

Some enthusiasts may wonder why knowing how to accomplish a touch and go landing is important.  After all, surely it is more important to understand the intricacies of a full stop landing using one of the several approach types that the B737 is certified to carry out, and be able tom land the aircraft following the procedure outlined in the approach chart.

Flying circuits and performing touch and go landings will vastly improve your airmanship, as a good majority of what is required during touch and go landings can be applied to other aspects of flying the B737.  Additionally, the touch and go procedures are consolidated into a time-dependent envelope in which everything occurs relatively quickly.  If a virtual flyer is competent in carrying out a touch and go landing, then it is a very easy transition to use one of the more advanced approach formats.

Final Call and Score

‘Touch and Go Landings’ is aimed at the novice to intermediate virtual pilot who wishes to learn the correct procedures first time around; advanced users will also benefit by not second guessing procedures they are presently using.   This said, there are many ways to fly the Boeing 737 aircraft, and often the method chosen depends on the flight crew, environmental constraints and the airline policy. 

It is important to realise that the guide is not a glorified tutorial written by an aviation enthusiast, but rather is a thoroughly researched and well written and easy to read text, that provides a pallet of information and comprehensive procedures that are relevant to flying the B737.  The guide not only provides a framework of what to do, but it also explains the how and why.

To read more about the guide or to purchase a copy, navigate to the author's website at www.jf737ngx.wordpress.com. Otherwise, copies can be purchaed directly from Amazon.

The current retail price is $24.95. 

Introductory discount coupons are available, for a limited time, at Jonathan Fyfe’s website.

I have given the guide a score of 9/10.

Transparancy

I have not received remuneration for this review; however, I was provided a guide ‘gratis’ to read.  The review is my opinion. 

Glossary and Acronyms

  • FCOM – Flight Crew Operations Manual (Boeing airline specific document)

  • FCTM – Flight Crew Training Manual (Boeing airline specific document)

  • FMA – Flight Mode Annunciations

B737 Original Equipment Manufacture RMI Knobs Fully Functional

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oem rmi knobs mounted to the potentiometers that control the rmi

In two previous posts, I documented the installation of two bespoke reproduction RMI knobs and aN OEM ADF/VOR switch assembly mounted in the center pedestal.  The purpose of the switch assembly, which originally was used in a Boeing 727 airframe, was to provide an easy method to switch between ADF and VOR as the two knobs mounted on the RMI were non-functional.

With the acquisition of OEM RMI knobs, the next step was to implement the functionality of these knobs by installing micro-rotary switches to the RMI frame behind each knob.  The non Next Generation compliant RMI Switch Assembly panel would then be superfluous and removed from the center pedestal.

Installing the Micro-rotary Switches to the RMI Frame

The first step was to remove the RMI frame from the MIP and enlarge the holes that the RMI knobs reside.  This is to allow the installation of the two micro-rotary switches. To do this, a Dremel rotary tool was used.   

To enable the wires from the rotary switches to be routed neatly behind the RMI frame, a very narrow trench was cut into the rear of the plastic frame.  It is very important that this task is done with due diligence as the RMI frame produced by Flight Deck Solutions (FDS) is manufactured from ABS plastic and not metal – if the cut is too deep or too much pressure is applied to the Dremel, then the frame will be damaged.

The wires from the the RMI knobs are then laid inside the earlier cut trench and aluminum-based tape is  applied over the wires.  This ensures the wires are secure and do not dislodge from the RMI frame.

The micro-rotary switches used in this conversion are 1 cm in length (depth); therefore, to use these rotaries successfully you will need to have a certain amount of airspace between the rear of the RMI frame and front of the computer screen (central display unit).  Whether there is enough room to facilitate the installation of the rotary switch, will depend upon the manufacturer of the MIP and RMI frame – some manufacturers have allowed a centimeter or so of space behind the RMI frame while others have the frame more or less flush to the center display unit screen.  If the air space is minimal, the rear of the rotary may rub against the display unit.

RMI frame and OEM knobs connected to small rotary potentiometers.  Note the metal sleeve and grub screw in the knob.

There are several methods that can be used to secure the rotaries to the RMI frame.  By far the easiest is to enlarge the hole in the RMI frame to a diameter that the rotary can be firmly pushed through the hole and not work its way loose.  Another method, more permanent, is to glue the rotary inside the hole.  No matter which method used, the rotary must be secured inside the hole otherwise when the RMI knob is turned the rotary will swivel within the hole.

Once the rotaries are installed to the frame, the OEM knobs are carefully pushed over the rotaries and the metal grub screws on the knob tightened.  One of the benefits of using OEM knobs is that the inside of the knob has a metal sleeve which ensures that the knob will not wear out and slip with continual use – reproduction knobs rarely are manufactured with an inside metal sleeve.

Interface Card and Configuration

To enable functionality, the wires from the rotaries are carefully threaded through the MIP wall and routed to an interface card; A PoKeys card, mounted in the System Interface Module (SIM), has been used.  It is not necessary to use a large gauge wire to connect the rotaries to the interface card.  This is because the electrical impulse that travels through the wire is only when the RMI knob is turned, and then it is only for a scone or so.  

The functionality for the RMI knobs is configured within the ProSim737 avionics suite in the configuration/switches area of the software.

Micro-rotary Switches

There are several micro-rotary switches available in the market.  This conversion uses A6A sealed rotary DIP switches; they are compact and inexpensive.

When selecting a rotary, bear in mind that many rotaries are either two, three or four clicks in design.  This means that for a 90 degree turn, such as required when altering the RMI from VOR to ADF, the rotary will need to travel through a number of clicks to correspond with the visual position of the switch.

The A6A type mentioned above are a two click type.  The first click will change the designation (VOR to ADF or back again), however, for realism two clicks are made (90 degree turn).  At the time of the conversion it was not possible to find a small enough rotary that was one click.  Despite this shortcoming, the physical clicks are not very noticeable.

This conversion is very simple and is probably one of the easiest conversions that can be done to implement the use of OEM knobs.  There is minimal technical skill needed, but a steady hand and a good eye is needed to ensure the RMI frame is not damaged when preparing the frame for the installation of the two rotary switches.

oem rmi knobs in original plastic bag. note metal inner sleeve and grub screw

OEM RMI Gauge

This  conversion uses two OEM RMI knobs and rotaries to interface with the standard virtual RMI gauge provided within the ProSim737 avionics suite.  Converting an OEM RMI gauge for standalone operation is possible and has been accomplished by other enthusiasts; however, whether a full RMI conversion can be done very much depends upon your particular simulation set-up.

If a OEM RMI gauge is installed, there may be a spacing issue with the other alternate gauges.  In particular, the Integrated Standby Flight Display (ISFD) will require a smaller dedicated display screen.  Likewise, the EICAS display screen will need to be smaller so as to fit between the RMI gauge and the landing gear assembly.  Also, an extra display port will be required for the computer to read the ISFD display screen. 

Certainly, a complete conversion of a RMI gauge is the best way to proceed, if you already own a OEM RMI unit, and if the set-up problems are not too difficult to overcome.

Acronyms

  • MIP – Main Instrument Panel

  • OEM – Original Equipment Manufacturer

  • RMI – Radio Magnetic Indicator

Boeing Nut Cracker - Loosening Stab Trim Wheel Nuts

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Boeing Nut Cracker - two raised lugs fit firmly into their opposite number to enable the stab trim wheel nut to be easily loosened or tightened

Any industry has tools that have been designed for a specific task – whether it is for automotive, construction or aviation.  

Specialist tools enable a particular job to be accomplished quickly and effectively with the minimum of fuss.  More importantly, damage to a part is less likely when using a specialised tool. 

A person who makes tools usually has a trade certificate and those who are gifted in this area are called boiler makers; a gifted boiler maker can literally make anything.

Captain-side stab trim wheel nut showing recessed indentations on the nut.  The screwed rod (tip showing in photograph) is ~40 cm in length and is inserted through one of the  trim wheels, through the throttle quadrant, and is then secured by the unique nut on the opposite trim wheel

Stab Trim Wheel Nut

The stab trim wheels have two nuts that hold the trim wheels in place - one on each side of the throttle quadrant.  When attempting to remove the trim wheel nut it is a good idea to use a tool, as the nut can be easily damaged (burred).

The nut has two shallow indentations each side of it to enable it to be firmly tightened. 

Often the nut is over-tightened by the continual rotation of the trim wheels, or by an overzealous technician applying more force than they should.  If the nut has been over tightened, removing the trim wheels can be difficult. 

A common man’s blade screwdriver can be used to loosen the nut, by applying the blade to one side of the two indentations, grasping the trim wheel firmly and turning the driver.  But, do not be surprised if the recessed indents are damaged, the screwdriver slips and scratches something, or worse you end up with the blade of the screwdriver through your hand!

Boeing Specialised Tool

Boeing technicians use a specialised tool to loosen and tighten the nuts that hold the trim wheels in place – no doubt it also has a special name (?).  This tool, like all specialist tools is expensive, and more so because it is used in the aviation industry. 

I explained the problem to a friend of mine who like a ‘genie in a bottle’, designed and made this small tool for me.  It is not fancy or technical, but it does the job it has been designed to do especially well – every time. 

The tool is made from aluminium with two raised indentations that fit into the two recessed indentations on the trim wheel nut.  A simple shaft placed through a drilled hole in the stem of the tool enables the user to apply enough leverage to 'crack' all but the most resistant of trim wheel nuts. 

The heavy duty cog wheel that the trim wheels are secured to.  When removing the trim wheels it is very important not to dislodge the cog as the bearings on the inner side of the cog will fall out of alignment

Caution - Removing the Trim Wheels from the Main Shaft 

Whenever the trim wheels have to be removed from the throttle quadrant, it is very important not to dislodge the cog by pushing or pulling the shaft through the throttle unit.  This is relatively easy to do as often the trim wheels adhere to the cog.

Attached to the cog (inside the throttle unit) are several bearings, which if dislodged, will fall out of alignment.  The bearings are important to the correct functioning of the trim wheels and it is very difficult, if not impossible, to reinstall the bearings after they have fallen out of place.

When removing the trim wheels, carefully 'jiggle' the trim wheel until it works its way loose of the cog - never forcefully pull the trim wheel outwards as the cog and shaft may come out of the throttle unit, allowing the bearings to fall out of alignment.  Furthermore, be mindful that when you remove one of the trim wheels the other may rotate forward or backwards due to centrifugal force.

Before replacing the trim wheels, to help avoid the wheel from sticking to the shaft and cog, apply an amount of grease to the cog teeth.

Update

on 2016-05-26 00:01 by FLAPS 2 APPROACH

This tool has now been replaced with a new design with better engineering.  To read about the new tool:  Trim Wheel Nut Tool - New Design.

Throttle Quadrant Rebuild - Clutch, Motors, and Potentiometers

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Captain-side of throttle quadrant showing an overview of the new design.  The clutch assembly, motors, and  string potentiometer can be seen, in addition to a portion of the revised parking brake mechanism

An earlier article, Throttle Quadrant Rebuild – Evolution Has Led to Major Changes has outlined the main changes that have been made to the throttle quadrant during the rebuild process. 

This article will add detail and explain the decision making process behind the changes and the advantages they provide.  As such, a very brief overview of the earlier system will be made followed by an examination of the replacement system.

Limitation

It is not my intent to become bogged down in infinite detail; this would only serve to make the posts very long, complicated and difficult to understand, as the conversion of a throttle unit is not simplistic.

This said, the provided information should be enough to enable you to assimilate ideas that can be used in your project.  I hope you understand the reasoning for this decision.

The process of documenting the throttle quadrant rebuild will be recorded in a number of articles.  In his article I will discuss the clutch assembly, motors, and potentiometers. 

Why Rebuild The Throttle Quadrant

Put bluntly, the earlier conversion had several problems; there were shortfalls that needed improvement, and when work commenced to rectify these problems, it became apparent that it would be easier to begin again rather than retrofit. Moreover, the alterations spurred the design and development of two additional interface modules that control how the throttle quadrant was to be connected with the simulator.

TIM houses the interface cards responsible for the throttle operation while the TCM provides a communication gateway between TIM and the throttle.

Motor and Clutch Assembly - Poor Design (in previous conversion)

The previous throttle conversion used an inexpensive 12 volt motor to power the thrust lever handles forward and aft.  Prior to being used in the simulator, the motors were used to power electric automobile windows.  To move the thrust lever handles, an automobile fan belt was used to connect to a home-made clutch assembly.

This system was sourly lacking in that the fan belt continually slipped.  Likewise, the nut on the clutch assembly, designed to loosen or tighten the control on the fan belt, was either too tight or too loose - a happy medium was not possible.   Furthermore, the operation of the throttle caused the clutch nut to continually become loose requiring frequent adjustment.

The 12 volt motors, although suitable, were not designed to entertain the precision needed to synchronize the movement of the thrust levers; they were designed to push a window either up or down at a predefined speed on an automobile.

The torque produced from these motors was too great, and the physical backlash when the drive shaft moved was unacceptable.  The backlash transferred to the thrust levers causing the levers to jerk (jump) when the automation took control (google motor backlash).

This system was removed from the throttle.  Its replacement incorporated two commercial motors professionally attached to a clutch system using slipper clutches.

Close up image of the aluminium bar and ninety degree flange attachment.  The long-threaded screw connects with the tail of the respective thrust lever handle. An identical attachment at the end of the screw connects the screw to the large cog wheel that the thrust lever handles are attached

Clutch Assembly, Connection Bars and Slipper Clutches - New Design

Mounted to the floor of the throttle quadrant are two clutch assemblies (mounted beside each other) – one clutch assembly controls the Captain-side thrust lever handle while the other controls the First officer-side. 

Each assembly connects to the drive shaft of a respective motor and includes in its design a slipper clutch.  Each clutch assembly then connects to the respective thrust lever handle.  A wiring lumen connects the clutch assembly with each motor and a dedicated 12 volt power supply (mounted forward of the throttle quadrant).  See above image.

Connection Bars

diagram 1: crossection and a cut-away of a slipper clutch

To connect each clutch assembly to the respective thrust lever handle, two pieces of aluminium bar were engineered to fit over and attach to the shaft of each clutch assembly. 

Each metal bar connects to one of two long-threaded screws, which in turn connect directly with the tail of each thrust lever handle mounted to the main cog wheel in the throttle quadrant. 

Slipper Clutches

close up of slipper clutch showing precision ball bearings

A slipper clutch is a small mechanical device made from tempered steel, brass and aluminum.  The clutch consists of tensioned springs sandwiched between brass plates and interfaced with stainless-steel bearings.  The bearings enable ease of movement and ensure a long trouble-free life.

The adjustable springs are used to maintain constant pressure on the friction plates assuring constant torque is always applied to the clutch.  This controls any intermittent, continuous or overload slip.

A major advantage, other than their small size, is the ease at which the slipper clutches can be sandwiched into a clutch assembly.

Anatomy and Key Advantages of a Slipper Clutch

A number of manufacturers produce slipper clutches that are specific to a particular industry application, and while it's possible that a particular clutch will suit the purpose required, it's probably a better idea to have a slipper clutch engineered that is specific to your application. 

The benefit of having a clutch engineered is that you do not have to redesign the drive mechanism used with the clutch motors.

Key advantages in using slipper clutches are:

  • Variable torque;

  • Long life (on average 30 million cycles with torque applied);

  • Consistent, smooth and reliable operation with no lubrication required;

  • Bi-directional rotation; and,

  • Compact size.

The clutch assembly as seen from the First Officer side of the throttle quadrant.  Note the slipper clutch that is sandwiched between the assembly and the connection rods.  Each thrust lever handle has a dedicated motor, slipper clutch and connection rod.  The motor that powers the F/O side can be seen in the foreground

Clutch Motors

The two 12 Volt commercial-grade motors that provide the torque to drive the clutch assembly and movement of the thrust lever handles, have been specifically designed to be used with drives that incorporate slipper clutches.

In the real world, these motors are used in the railway and marine industry to drive high speed components.  As such, their design and build quality is excellent. The motors are designed and made in South Korea.

Each motor is manufactured from stainless steel parts and has a gearhead actuator that enables the motor to be operated in either forward or reverse.  Although the torque generated by the motor (18Nm stall torque) exceeds that required to move the thrust lever handles forward and aft, the high quality design of the motor removes all the backlash evident when using other commercial-grade motors.  The end result is an extraordinary smooth, and consistent operation when the thrust lever handles move.

A further benefit using this type of motor is its size.  Each motor can easily be mounted to the floor of the throttle quadrant; one motor on the Captain-side and the second motor on the First Officer-side.  This enables a more streamlined build without using the traditional approach of mounting the motors on the forward firewall of the throttle quadrant.

captain-side 12 Volt motor, wiring lumen and dual string potentiometer that control thrust levers

String Potentiometers - Thrust Levers 1/2

Two Bourns dual-string potentiometers have been mounted in the aft section of the throttle unit.  The two potentiometers are used to accurately calibrate the position of each thrust lever handle to a defined %N1 value.  The potentiometers are also used to calibrate differential reverse thrust.

The benefit of using Bourns potentiometers is that they are designed and constructed to military specification, are very durable, and are sealed.  The last point is important as sealed potentiometers will not, unlike a standard potentiometer, ingest dust and dirt.  This translates to zero maintenance.

Traditionally, string potentiometers have been mounted either forward or rear of the throttle quadrant; the downside being that considerable room is needed for the operational of the strings.  

In this build, the potentiometers were mounted on the floor of the throttle housing (adjacent to the motors) and the dual strings connected vertically, rather than horizontally.  This allowed maximum usage of the minimal space available inside the throttle unit.

Automation, Calibration and Movement

The automation of the throttle remains as it was.  However, the use of motors that generate no backlash, and the improved calibration gained from using string potentiometers, has enabled a synchronised movement of both thrust lever handles which is more consistent than previously experienced.

Reverse Thrust 1/2

Micro-buttons were used in the previous conversion to enable enable reverse thrust - reverse thrust was either on or off, and it was not possible to calibrate differential reverse thrust. 

Dual string potentiometer that enables accurate calibration of thrust lever handles and enables differential thrust when reversers are engaged

In the new design, the buttons have been replaced by two string potentiometers (mentioned earlier).  This enables each reverse thrust lever to be accurately calibrated to provide differential reverse thrust.  Additionally, because a string potentiometer has been used, the full range of movement that the reverse thrust is capable of can be used.

The video below demonstrates differential reverse thrust using theProSim737 avionics suite. The first segment displays equal reverse thrust while the second part of the video displays differential thrust.

 

Incremental reverse thrust N1 displayed on eicas (ProSim737) from dual potentiometer

 

Calibration

To correctly position the thrust lever handles in relation to %N1, calibration is done within the ProSim737 avionics software  In calibration/levers, the position of each thrust lever handle is accurately ‘registered’ by moving the tab and selecting minimum and maximum.  Unfortunately, this registration is rather arbitrary in that to obtain a correct setting, to ensure that both thrust lever handles are in the same position with identical %N1 outputs, the tab control must be tweaked left or right (followed by flight testing).

When tweaked correctly, the two thrust lever handles should, when the aircraft is hand-flown (manual flight), read an identical %N1 setting with both thrust levers positioned beside each other.  In automated flight the %N1 is controlled by the interface card settings (Polulu JRK cards or Alpha Quadrant cards).

Have The Changes Been Worthwhile

Comparing the new system with the old is 'chalk and cheese'.  

One of the main reasons for the improvement has been the benefits had from using high-end commercial-grade components.  In the previous conversion, I had used inexpensive potentiometers, unbalanced motors, and hobby-grade material.  Whilst this worked, the finesse needed was not there.

One of the main shortcomings in the previous conversion, was the backlash of the motors on the thrust lever handles.  When the handles were positioned in the aft position and automation was engaged, the handles would jump forward out of sync.  Furthermore, calibration with any degree of accuracy was very difficult, if not impossible. 

The replacement motors have completely removed this backlash, while the use of string potentiometers have enabled the position of each thrust lever handle to be finely calibrated, in so far, as each lever will creep slowly forward or aft in almost perfect harmony with the other.

An additional improvement not anticipated was with the installation of the two slipper clutches.  Previously, when hand-flying there was a binding feeling felt as the thrust lever handles were moved forward or aft.  Traditionally, this binding has been difficult to remove with older-style clutch systems, and in its worst case, has felt as if the thrust lever handles were attached to the ratchet of a bicycle chain.

The use of high-end slipper clutches has removed much of these feeling, and the result is a more or less smooth feeling as the thrust lever handles transition across the throttle arc.

Future Articles

Future articles will address the alterations made to the speedbrake, parking brake lever, and internal wiring, interfacing and calibration.  The rotation of the stab trim wheels and movement of the stab trim indicator tabs will be discussed.

This article is one of several that pertain to the conversion of the OEM throttle quadrant. A summary page with links can be viewed here: OEM Throttle Quadrant. 

Update

on 2018-04-11 01:08 by FLAPS 2 APPROACH

This article was not able to be published at an earlier time because of issues with confidentiality and potential patents.  The article has been re-written (March 2018). 

OEM Annunciators Replace Reproduction Korrys in Main Instrument Panel (MIP)

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There can be little doubt that OEM annunciators shine far brighter than their reproduction counterparts.  The korrys are lit during the lights test. OEM Flaps gauge yet to be installed

A task completed recently has been the replacement of the reproduction annunciators located on the Main Instrument Panel (MIP) with OEM annunciators. 

The reason for changing to OEM annunciators was several-fold.  First, anything OEM is superior to a reproduction item.  Second, I wanted to reproduce the same korry annuciation  lighting observed in the OEM panels in the center pedestal, fire suppression panel, and when fitted, the forward and aft overhead panels.  Additionally, it was also to enable the push-to-test functionality and to provide better illuminance during daylight.  Some reproduction korrys are not that bright when annunciated and are difficult to see during the day.

This post will explain the anatomy of the annunciators that are fitted to the Main Instrument Panel (MIP).  It will also detail how the annunciators are wired and configured in ProSim737, and provide incite into some of the advantages and functionality that can be expected when using OEM annunciators.

The individual indexing can be observed on the top surface of the upper assembly (3 groves).  To separate the two assemblies a hex screw must be used to loosen the hex screw located inside the brass-coloured circular fitting.  Note that this is a new style LED korry which does not support the older incandescent bulbs

Anatomy of a Annunciator (Korry)

An annunciator is a light which is illuminated when a specific function occurs on the aircraft.  Annunciators are often called by the generic name ‘Korry’, as Korry is the registered trademark used by a company called Esterline that manufactures annunciators for the aero and space industry. 

There are two types of annunciators used in the Boeing aircraft, the 318 and the 319 which are either a Type 1 or Type 2 circuit. 

The 318 and 319 Korrys are not interchangeable.  Each Korry has a different style of bulb, differing electrical circuits, and a different method of internal attachment (captive hex screw verses two blade-style screws).  The only similarity between the 318 and 319 korrys is that the hole needed to house the korry in the MIP is identical in size - .440” x .940”.  The 318 Korry replaced the 319 Korry.

The circuit type refers to the electrical circuit used in the Korry.    Both circuit types require a ground-controlled circuit to turn it on, however, Type 1 circuits are ground-seeking while Type 2 circuits are power-seeking.    Visually (when installed to the MIP) the 318 and 319 korrys are indiscernible.

Annunciators have five parts that comprise:

(i)     The lower assembly and terminals (usually four terminals in number);

(ii)    The upper assembly;

(iii)    The outer housing/sleeve which has a lip to allow a firm connection with the MIP;

(iv)    The push-in light plate which includes the bulbs; and,

(v)    The legend, which incorporates a replaceable coloured lens.

The four terminal connections on the rear of each annunciator are specific to the functionality of the unit.  Each will exhibit a differing circuit dependent upon its function.  Likewise, each annunciator is individually indexed to ensure that the upper assembly cannot be inadvertently mated with the incorrect lower assembly.

Annunciators typically are powered by 28 Volts, use two incandescent ‘push-in style’ bulbs, and dependent upon the korry’s function, may have a light plate coloured amber, white red or green.  The legend is the name plate, and legends are usually laser engraved into the light plate to ensure ease of reading.  The engraved letters are in-filled with colour to allow the printing to stand out from the light plate’s lens colour.

Specialised Korry

The Boeing 737 aircraft uses a Korry, a type 318, that is slightly different to the standard Korry. This Korry enables the functionality for the BELOW G/S – P-Inhibit function.  

The Type 318 differs from other korrys used in the MIP in that it has a dry set of momentary contacts which are controlled by pressing the light plate.  Pressing the illuminated light plate extinguishes the annunciator and cancels the aural ‘Below Glideslope’ caution.

Reproduction Verses Original Equipment Manufacture (OEM)

The four biggest differences between reproduction and OEM annunciators are:

(i)     The ability to depress the light plate in the OEM unit for Push-To-Test function;

(ii)    The ability to replicate specific functions, for example the Below G/S P-Inhibit korry;

(iii)    The hue (colour) of the lens and crispness of the legend; and,

(iv)    The brightness of the annunciator when illuminated (5 volts verses 28 volts).

Reproduction Korry Shortfalls

Two areas lacking in reproduction units is the brightness of the annunciator when illuminated, and poorly defined legends.  

For the most part, reproductions use 5 volts to illuminate two LEDS located behind the lens.  Whilst it is true that the use of LED technology minimises power consumption and heat generation, the brightness of the LEDS, especially during the day,  may not be as bright as the two 28 volt incandescent bulbs used in an OEM annunciator.   Moreover, 5 volts does not allow the successful use of DIM functionality.  

It is unfortunate that many lower priced annunciators also lack well defined engraved lens plates making the ability to read the annunciator legend difficult at best.

Shortfalls notwithstanding, most high-end reproduction annunciators are of high quality and do the job very well.  

 

Table 1: quick reference to determine the main differences between OEM and reproduction annunciators. Note that the appearance of the annunciator can alter markedly between different manufacturers of reproduction units

 

Installation, Interfacing and Configuration of OEM Annunciators

Replacing a reproduction annunciator with its OEM counterpart is straightforward if the Main Instrument Panel (MIP) has been produced 1:1; however, reproduction MIPs are rarely exactly 1:1 and in all probability you may need to enlarge the hole that the annunciator resides.  If this is the case, ensure you use a fine-grade aluminum file and gentle abrade the hole to enlarge it.  When enlarging the hole, ensure you continually check the hole size by inserting the korry – if the hole is enlarged too much, the korry will be loose and will require additional methods to secure to the MIP.

korry system 318 type 1

Disassembling a Korry

It is important to understand how to unassemble the annunciator.  

First, the light plate has to be gently pried loose from the upper assembly.  Once this is done, the upper and lower assemblies must be separated to allow the outer/sleeve to be removed.  The Type 318 annunciators have a hex screw, located in the lower assembly unit, which needs to be loosened with a 5/64th hex wrench to allow separation, while the Type 319 annunciators are secured by two standard screws that require a small blade screwdriver.  

Once the two parts are separated, it should be noted that the upper assembly has a flange at the forward end; this flange enables the annunciator to be firmly connected to the MIP.   

Attaching a Korry to the MIP

Is your MIP 1:1 and will it fit OEM korrys without further to do?  Click the diagram to see the dimensions of korrys (with thanks to Mongoose for diagram)

Insert the upper assembly into the MIP flange facing forward.  Next, slide the housing over the rear of the mechanism from the rear of the MIP.  Rejoin the lower section and tighten the hex screw.    If the MIP is 1:1, the annunciator should now be firmly secured to the MIP wall. The light plate can now be pushed into the mechanism.

If the annunciator does not fit firmly into the MIP, it can be secured by using silastic or a glue/metal compound.  (I do not recommend this.  It is best to ensure the hole is the correct size or a tad too small.  This will guarantee that the annunciator will have a firm fit).

Provided the mechanism is not faulty or does not break, the chance that it will need to remove it is very remote.  If the bulbs fail, they are easily replaced as they are contained within the light plate.

Wiring - Procedure

Wiring the MIP annunciators is a convoluted and repetitious process that involves daisy-chaining the various annunciators together.  Because wiring is to and from four terminals, it can be difficult to remember which wire goes where.  As such, it is recommended to use coloured wire, label each wire and keep meticulous notes.  

Each annunciator has four terminals located on the rear of the unit that corresponds to:

(i)      Positive (28 volts);

(ii)     Logic for the function of the korry;

(iii)    Lights test; and,

(iv)    Push-To-Test.  

To crosscheck the above, each Type 2 korry has a circuit diagram stenciled on the side of the assembly.

 

Figure 1: A schematic of the three types of korrys used in the Boeing 737.  The left diagram is from the 318 push to inhibit korry (diagram copyright David C. Allen

 

For the OEM korrys to function correctly, they need to be connected with an interface card (I/O card).  An example of such a card is a Phidget 0/16/16 card.

(i)    Designate the annunciator closest the I/O card and power supply as the lead annunciator (alpha).  

(ii)    Terminal 1 and Terminal 4 are the power terminals for each korry.  Connect to the alpha korry the positive wire from the 28 Volt power supply to terminal 1 and the 28 Volt negative wire to terminal 4.  The wires from these two terminals are then daisy-chained to the identical terminals on the other korrys in the system.

(iii)    Terminal 2 controls the logic behind the function for each korry.  A wire must connect from terminal 2 of each korry to the output side of the I/O card.  To close the loop in the I/O card, a wire is placed from 28 Volts negative to the ground terminal on the card (input).

(iv)    Terminal 3 controls the logic behind the light test toggle.  A wire is daisy-chained from terminal 3 of the alpha korry to all other korrys in the system.  A wire is then extended from the final korry to the lights test toggle switch.  This switch has been discussed in detail in a separate post.

Quite a bit of wire will be needed to connect the thirteen or more annunciators and it is a good idea to try and keep the wire neat and tidy by using a lumen to secure it to the rear of the MIP.

Mounting and Brackets

Every simulator design is different, and what is suitable for one set-up may not be applicable to another.  

The I/O card that is used to control the MIP annunciators is mounted within the System Interface Module (SIM).  To this a straight-through cable is securely attached that connects to a D-Sub connector mounted on an aluminum bracket.  The bracket and two terminal blocks are strategically mounted on the rear of the MIP and enable the various wires from the korrys to connect with the straight-through cable.

Interfacing and Configuration Using ProSim737

To interface the annunciators, follow the directions on how to wire your I/O card.

This article provides information on the Phidget 21 Manager (software) and how a Phidget interface card is used.

If the annunciators have been correctly daisy-chained together, only the wires from terminal 2 of each korry will need to be connected to Phidget card.  When power is applied, the Phidgets software will automatically assign outputs to any device (korry) attached to the 0/16/16 card.  

To determine the digital output number for each annunciator, open the Phidgets 21 Manager, push the light plate on a chosen annunciator and record the allocated output number.  The output numbers are used by ProSim737 to allocate that annunciator to a specific software command line.  

Configuring the MIP annunciators in ProSim737 is a two-step process.  First, the annunciator must be assigned as a switch (for the puhs- to-test function to operate), then as an indicator (for the annunciator to illuminate).  Before commencing, check that Phidgets have been assigned in the driver section of the configuration section of the main ProSim737 menu.  

Open the configuration screen and select switches and scroll downwards until you find the appropriate switch that corresponds to the annunciator.  Assign this switch to the output number assigned by the Phidgets software (If you have multiple Phidget cards installed ensure the correct card is assigned).  

After this has been completed, continue the configuration process by assigning each annunciator to the appropriate indicator in the configuration/indicators section.

Lights Test

A lights test is used to determine whether all the annunciators are operating correctly.  A lights test can be accomplished two ways. 

The first method is to press the light plate of an annunciator which operates a momentary switch that causes the light to illuminate (push-to-test).  This is an ideal way to determine if an individual annunciator is working correctly.

The second method is to use the MIP toggle switch.  Engaging the toggle switch to the on position will illuminate all the annunciators that are connected to the toggle switch.  This is an excellent way to ensure all the annunciators are operational and is standard practice before beginning a flight.

It should be noted that for all the annunciators to illuminate, each korry must be connected to the toggle switch. 

An earlier post explained the conversion and use of a OEM Lights Test Toggle Switch.

The fire suppression panel annunciators are also korrys.  Like their MIP sisters, the korrys are very bright when illuminated as they are powered by 28 volts

Korry Systems

This post has discussed the main annunciators on the MIP which is but one system.  Other systems include the annunciators for the forward and aft overhead annunciators, fire suppression panel and several other panels.

To connect additional systems to the enable a full lights test to be done, an OEM aircraft high amperage relay can be used.  

OEM multi-relay device.  The relay from a Boeing aircraft is not necessary; any aircraft relay will suffice.  It's wise to choose a relay that has multiple connection posts as this will enable different systems to be connected to the relay.  The relay is easily fitted to the rear of the MIP or to the inside of the center pedesta

Depending upon the type of relay device used (there are several types), it may be possible to connect up to three systems to the one relay.  This is made possible by the OEM toggle switches unique multi-segment system, and the ability of the relay to handle high amperage from multiple aircraft systems.

A benefit of using an OEM relay is that it provides a central point for all wires from the various systems to attach, before connecting to the lights test toggle switch.  Note that 28 volts bmust be connected directly to the relay for correct operation.

The relay will, depending upon the throw of the toggle switch (lights test), open or close the circuit of the relay.  Opening rhe relay circuit (when the light test toggle is thrown) enables 28 volts to flow through the relay and illuminate any annunciators connected to the system.

Availability

The Korrys originally were used in British Airways 737-400 Airframe 25843 G-DOCM (copyright Aero icarus)

Fortunately, apart from a few functions, there is little difference between older style annunciators used in the classic series airframes and those used in the Next Generation aircraft - an annunciator is an annunciator no matter from what airframe (100 series, Classic or Next Generation).

Annunciators are relatively common and are often found ion e-Bay.  However, to acquire a complete collection that is NG compliant can be time consuming, unless a complete panel is purchased and the annunciators removed.

Lineage

The annunciators used in the simulator came from a B737-400 airframe.   This aircraft - serial number N843BB and construction number 25843 had a rather interesting lineage. 

It began service life in March 1992 with British Airways as G-DOCM before being transferred to Fly Dubai and Air One in 2004.  Late 2004 the airframe was purchased by Ryan International and the registration changed to N843BB.  Between 2005 and 2010 the aircraft was leased to the Sundowner LCC who at the time was contracted to the US Dept. of Justice.   The aircraft was returned to Ryan International mid 2010 and subsequently scrapped.

Acronyms

New Interface Modules

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My friend and I have not been sitting idle.  Part of the upgrade to the simulator has been additional interface modules.

In early 2014, an Interface Master Module (IMM) was constructed to trial the modular concept.  This module housed most of the interface cards and relays that, at the time, were used in the simulator.  This trail was successful.  The single trial IMM has now been discarded and has been replaced with the:

Information concerning each of these modules, including an introduction to the modular concept, can be found in a new section named Interface Modules.  Interface Modules can be assessed from the main menu tabs located at the top of each website page (the brown banner).

It has taken considerable time to design and construct, and then interface these modules to the simulator.  To some, the process may appear complex and convoluted.  However, in the long term the idea is sound and a centralized area offers considerable advantages.

I hope you enjoy reading about the new modular systems.

Throttle Quadrant Rebuild - Evolution Has Led to Major Alterations

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oem 737-500 thrust levers

Two major changes to the simulator have occurred.  The first concerns the throttle quadrant and the second is the replacement of the trial Interface Master Module with a more permanent modular solution.  The changes will be documented in the near future after final testing is complete.

The throttle quadrant has been completely rebuilt from the ground up.  Although the outside may appear identical to the earlier quadrant, the rebuild has replaced nearly everything inside the quadrant and the end product is far more reliable than its predecessor.

The throttle unit, in its previous revision, worked well, but there were several matters which needed attention.  The automation and functionality was adequate, but could be improved upon.  There were also 'niggling' issues with how the clutch assembly operated - it was somewhat loose which caused several flow-on problems.

Initially, some minor improvements were to be made; however, one thing lead to another and as 'fate would have it' the throttle unit has been rebuilt from the bottom up.

Improvements

The improvements have primarily been to the automation, the autothrottle and the speedbrake system.  However, during the rebuild other functionality have been improved: the synchronised tracking movement of the thrust levers is now more consistent and reliable, and an updated system to operate the parking brake has also been devised.  This system replicates the system used in the real aircraft in which the toe brakes must be depressed before the parking lever can set or disengaged.

Furthermore, the potentiometers controlling the movement of the flaps and thrust levers have been replaced with string potentiometers which increases the throw of the potentiometer and improves accuracy.  The calibration of the flaps and speedbrake is now done within the system, removing the need for 'tricky' calibration in FSUIPC. 

In the previous throttle version there was an issue with the speedbrake not reliably engaging on landing.  This in part was caused by a motor that was not powerful enough to push the lever to the UP position with consistent reliability.  This motor has been replaced with a motor more suitable to the power requirement needed.  The speedbrake is mechanical, mimics the real counterpart in functionality, nd does not require software to operate.

This throttle conversion has maintained the advanced servo card and motor that was used to control the movement of the stab trim tabs (trim indicators); however, the motor that provides the power to rotate the trim wheels has been replaced with a more reliable motor with greater power and torque.  The replacement motor, in conjunction with three speed controller interface cards, have enabled the trim wheels to be rotated at four independent speeds.  This replicates the four speeds that the wheels rotate in the real 737 -800 aircraft.

Finally, the automotive fan-belt system/clutch system which was a chapter from the 'Dark Ages' has been replaced with two mechanical clutch assemblies that has been professionally designed to operate within the throttle unit - this will completely remove any of the 'niggles' with the previous clutch assembly becoming loose and the fan belt slipping.  Each thrust lever has a dedicated poly-clutch and separate high powered motor. 

A brief list of improvements and changes is listed below:

  • Next Generation skirt replaced with more accurate skirt (prototype);

  • Reproduction TO/GA buttons replaced with OEM square TO/GA buttons;

  • Fan belt driven clutch system replaced with slipper clutch system;

  • motors replaced that control lever movement and trim wheels;

  • 95% of wiring re-done to incorporate new interface modules;

  • Replacement interface alert system;

  • Flap potentiometers replaced by string potentiometers;

  • Speedbrake potentiometer replaced by linear potentiometer;

  • Thrust levers potentiometers replaced by dual string potentiometers;

  • Internal mechanism altered to stop noise of chain hitting throttle frame;

  • Thrust lever tracking movement accuracy improved;

  • Thrust reversers now have proportional thrust for each lever 1 and 2; and

  • The parking brake mechanism replaced with a more accurate system that reflects that used in the real aircraft

The conversion of the throttle quadrant has been a learning process, and the changes that have been done improve the unit's functionality and longevity - not too mention accuracy, far beyond what it was previously.

Dedicated Interface Modules

The throttle previously interfaced with the Interface Master Module (IMM).  The IMM was developed as a trial module to evaluate the modular concept.

The throttle quadrant will now directly interface with two dedicated modules called the Throttle Interface Module (TIM) and Throttle Communication Module (TCM).  Both of these modules contain only the interface cards, relays and other components required to operate the throttle and automation.  Additionally, the system incorporates a revised Interface Alert System which evolved from the original concept used in the IMM.

To read more concerning the various interface modules, a new website section has been produced named Interface Modules.  This section is found in the main menu tabs at the top of each page.

Flight Testing (March 2015)

The throttle and replacement interface modules are currently being evaluated and minor issues rectified.

Once testing is complete, the alterations undertaken during the rebuild process will be documented in separate posts and, to facilitate ease of searching, links will be added to the flight controls/throttle quadrant section.

It should be noted that the work done to rebuild the throttle was done with the help a friend, who has a through knowledge of electronics and robotics.

Integrated Approach Navigation (IAN) - Review and Procedures

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Japanese airlines nearly always gravitate to new technology.  ANA landing RJAA (Narita, Japan). Maarten Visser from Capelle aan den IJssel, Nederland, JA02AN B737 ANA gold cs landing (7211516992), CC BY-SA 2.0

Increased navigational accuracy obtained from software and hardware improvements have led to several enhanced approach types being developed for the Boeing 737.  These augmented approach types provide a constant rate of descent, follow an approximate 3 degree glide path, and eliminate the traditional step-down style of approach.   

This improves landing capability in adverse weather conditions, in areas of difficult terrain, and on existing difficult to fly approach paths.  Not to mention, the benefits that a stabilized and safer approach bring: greater passenger comfort, less engine wear and tear, and lower fuel usage while bringing less workload for the flight crew. 

In this article, I will discuss the concept of Integrated Approach Navigation (IAN) and explain the procedures recommended by Boeing to successfully implement IAN. 

The Boeing Flight Crew Training Manual (FCTM) has an excellent section addressing IAN, and I recommend you read it to gain a greater understanding of how the IAN system functions.

The Navigation Performance Scales (NPS), which augment IAN, will not be discussed.  NPS will form part of a future article.  Information in this article relates to FMC software U10.8A.

Overview

Integrated Approach Navigation (IAN) derives information from an approach type selected from the Flight Management Computer (FMC) database to generate a 3 degree glide path from the Final Approach Fix to the threshold of the runway.  In so doing, it displays visual cues similar to the Instrument Landing System (ILS).  Flight path guidance is derived from the FMC, navigational radios, or combination of both. 

To use IAN, an approach with a glide path must be selected from the FMC database.  The approach must include a series of waypoints that depict a vertical profile that includes a glide path.  

An IAN approach may be flown with a single autopilot, raw data, or by following the visual cues displayed on the Flight Director (FD).

IAN is an airline option, and although not every airline carrier will have IAN as part of their avionics suite, the technology is becoming more popular as the safety and economic benefits of IAN are understood by airline carriers.

Geometric Path (Glide Path)

An IAN Approach approximates a 3 degree glide path (descent profile) from the Final Approach Fix (FAF) to approximately 50 feet above the runway threshold.  Although, the glide path may not comply with altitude constraints in the FMC prior to the FAF, the generated glide path will always be at or above the altitude constraints between the FAF and the Missed Approach Point (MAP) displayed in the FMC.

Critically, an IAN approach is a Category I Non Precision Approach (NPA) and is not to be confused with an ILS Precision Approach.  Therefore, NPA procedures must be adhered to when initiating an approach using IAN.  

Although the automation provided by IAN will guide an aircraft (in most cases) to the threshold of the runway, IAN has not been designed to do this.  Rather, IAN has been designed to guide the aircraft to the MAP published on the approach chart.  The flight crew will then disengage IAN by disengaging the autopilot and autothrottle and fly the remainder of the approach manually as per NPA protocols.

In some instances, the final approach course (FAC) is offset from the runway center line and manoeuvring the aircraft for direct alignment will be necessary, whilst following the glide path angle.

Although the final approach is very similar to an ILS approach, IAN does not support autoland; if the aircraft is not in a stable configuration and you are not visual with the runway at or beyond the MDA, a missed approach procedure (Go-Around) should be executed.

Consistency in Procedures (eighteen approach types to one)

The introduction of IAN has condensed the number of approach types (and differing procedures) to one consistent procedure; minimising the amount of time an airline needs to train pilots in numerous approach types.  Time is money and utilising advanced technology such as IAN can increase airline productivity and safety.

Approach Types

IAN can be used for the following approach types:

  • RNAV

  • RNAV (RNP) – (provided there are no radius to fix legs)

  • NDB and VOR

  • GPS & GNSS

  • LOC, LOC-BC, TACAN, LDA SDF (or similar style approaches)

Note that if using IAN to execute a Back Course Localiser approach (B/C LOC), the inbound front course must be set in the MCP course window.

During the approach you must monitor raw data and cross check against other navigational cues.  Furthermore, although the use of IAN is recommended only for straight-in approaches, line use suggests that flight crews routinely engage IAN up to, but not exceeding 45 degrees from the runway approach course.

IAN is compatible with several approach types, however, being compatible does not necessarily mean that every approach type in the FMC is suitable. 

Since IAN was introduced, additional approaches have been developed and added to the RNAV family; in particular, RNAV (RNP) approaches, that use ‘radius to fix’ (RF) to generate a curved path that terminates at a location where an approach procedure begins.   These approaches have been designed to optimise airspace and usually have tight separation requirements; to fly these approaches an aircraft is required to have additional on-board navigation performance monitoring and alerting equipment. 

These approach charts are identified by the title RNAV (RNP) RWY XX and the letters AR (Authorisation Required) in the description of the chart. 

These approaches and are not suitable to use with IAN; they should be flown with LNAV/VNAV.

Recommended Approach Types

The best approach to use with IAN are straight-in or near straight-in approaches.  VOR, LOC, NDB, RNAV and RNAV (GNSS) approaches work especially well as these approaches usually provide relatively long straight-in legs. 

IAN can be used on an RNP (AR) approaches as long as there are no RF turns involved (straight-in approach only).  If flying such an approach you should be aware that the legs can be quite short and IAN may arm and engage quite late in the approach profile.

Important Point:

  •    The use of IAN is not authorised for a RNAV (RNP-AR) approach.

Using IAN – General

IAN does not need to be specifically ‘turned on’ for it to function; the functionality, if installed in the aircraft, is always operational.  When the aircraft is within range of the designated approach, the runway data and/or Deviation Pointers will annunciate and be displayed on the PFD.  At any time after this point has been reached, IAN can be armed and or engaged by pressing the APP button on the MCP.

Navigation Radios and Radio Frequencies

For an IAN approach to function, an approach procedure with a glide path must be selected from the FMC database.  Although selection of navigation radios is not mandatory, selection is recommended, as correct tuning of the radios can provide increased visual awareness and redundancy, should a CDU failure occur, or there be a corruption of the data in the FMC. 

Boeing strongly advise to tune the radios to the correct localiser frequency for the approach.  This eliminates the possibility of the radio picking-up another approach from a nearby airport (and providing erroneous data to the crew).  The ILS frequency must never be used with an IAN approach (unless the glideslope is inoperative).  In the case of an inoperative glideslope, the G/S prompt in the CDU must be selected to OFF to ensure that the FMC generated glide path is flown. 

Minimum Descent Altitude (MDA)

As mentioned, an IAN approach is a NPA, and when authorised by the Regulatory Authority non-ILS approaches can be flown to a published VNAV Decision Altitude/Height (DA/H) or to a published MDA (the MDA is used as a decision altitude).  If not authorised to use the MDA as a decision altitude, crews must use the MDA specified for the approach flown.

To comply with the MDA protocols during a constant angle approach where a level off is not planned at the MDA, it is necessary to add +50 feet to the published MDA.  This enables an adequate buffer to prevent incursion below the MDA and adhere to the NPA protocols.

Important Points:

  • IAN uses the FMC database to generate a 3 degree glide path from the FAF to the runway threshold.  IAN does not require the navigation radios to be tuned.  However, it is recommended to tune the radios.

  • Some approaches in the FMC database have a number of glide paths displayed with differing altitudes.  When presented with this scenario, always select the first glide path and altitude.

IAN approach to RJAA ILS X or LOC X Rwy 16L.  The localiser has been captured and the FMA displays FAC in green, while G/P is armed (FMA G/P white).  The vertical Deviation Pointer is displayed as an outlined magenta-coloured diamond (anticipation pointer) while the localiser is displayed as solid magenta (because FAC has been captured).  The source of the runway data is from the FMC (ProSim737 avionics suite)

Using IAN - IAN Annunciations and Displays

IAN can display several visual cues to alert you to the status of the IAN system.  The cues are triggered at various flight phases and are displayed on the attitude display of the Primary Flight Display (PFD) and on the Flight Mode Annunciator (FMA).

Runway Data:   Runway data (runway identifier, approach front course, approach type and distance to threshold) is displayed in the top left area on the PFD when either the localiser or the selected FMC approach is in range of the runway. 

IAN approach to RJAA ILS X or LOC X Rwy 16L.  The localiser and glide path have been captured.  The FMA displays FAC and G/P in green and SINGLE CH is displayed.  The Deviation Pointers, previously in outline (Figure above), are now solid filled.  The aircraft will descent on the glide path to the threshold of the runway (ProSim737 avionics suite)

If the source of the runway data is the navigation radio, then this information will be displayed when the radio is in range of the localiser.  However, if the primary data source is from the FMC (radio not tuned) the runway data will be displayed only after IAN has engaged.   When IAN engages, the runway data will be sourced from the FMC.  This will be evident as the  approach type will be displayed on the PFD.

The approach type (LNAV, FMC, LOC, ILS etc) displayed will depend on what type of approach has been selected from the FMC database. 

Approach Guidance:  Approach guidance (Deviation Pointers) are displayed on the PFD whenever IAN is in range of the runway.  When the Deviation Pointers are displayed, IAN can be used.

Final Approach Course (FAC):  The letters FAC are displayed on the center FMA when IAN is armed.

It stands to reason, that FAC (lateral guidance) usually annunciates prior to G/P (vertical guidance), but depending on the position of the aircraft when APP in pressed, both annunciations may be displayed at the same time.

Glide Path (G/P):  The letters G/P are displayed on the right FMA when IAN is armed.

FMA FAC and G/P Colours:  Two FMA colours are used.  White indicates that the FAC or G/P is armed.  The colour of the FMA display will change from white to green when the aircraft captures either the localiser or glide path. 

Mode Control Panel (MCP):  Arming IAN (pressing the APP button on the MCP) will cause the letters APP on the MCP to be illuminated in green.  The APP light will extinguish when IAN captures the glide path.  

Lateral and Vertical Guidance Deviation Pointers:  Deviation Pointers display the lateral and vertical position of the aircraft relative to the final approach course of the selected runway.  The lateral pointer represents the localiser while the vertical pointer represents the glide path.  The pointers are displayed whenever IAN is in range of the runway. 

The pointers will initially be displayed as either magenta or white-coloured outlined diamonds.  When the aircraft captures either the localiser or glide path, (2 1/2 dots from center) the pointer (s) will change from an outline, to a solid-filed magenta-coloured diamond.

Whether the initial colour of the diamonds is magenta or white depends on which pitch/roll mode has been selected when the aircraft comes into range.

Although the correct name for the pointers is Deviation Pointers, they are often called anticipation pointers, anticipation cues or ghost pointers (ghost pointers being an 'Americanism').

During an IAN approach:

  1. The deviation alerting system will self-test when passing through 1500 feet radio altitude.  The self-test will generate a two-second FAC deviation alerting display on each PFD (the pointers will flash in amber); and,

  2. If the autopilot is engaged, and at low radio altitudes, the scale and Deviation Pointers will turn amber and begin to flash if the deviation from either the localiser or glide path is excessive.

SINGLE CH:  SINGLE CH will be displayed in green, when the aircraft captures the glide path (both the localiser and glide path). At this time, the Deviation Pointers will change from white-coloured outlines to solid magenta-coloured diamonds.  FAC and G/P on the FMA will also be in green.  Additionally, the illuminated APP button on the MCP will extinguish.  At this point, the aircraft will be guided automatically along the glide path.

Flight Mode Annunciations (FMA):  The FMA display will vary depending on the source of the navigation guidance used for the approach.

For localiser-based approaches (LOC, LDS, SDF and ILS (glideslope OUT), the FMA will display VOR/LOC and G/P.  For B/C LOC approaches, the FMA will display B/CRS and G/P.

If lateral course guidance is derived from the FMC (RNAV, GPS, VOR, NDB and TACAN approaches), the FMA will display FAC and G/P.

Ground Proximity Warning System (GWPS) Aural Warnings and Displays:  GWPS warnings will annunciate if at any time the aircraft deviates below the glide path, and failure to disengage IAN at the appropriate altitude will trigger a GPWS aural warning alert ‘autopilot autopilot’ at 100 feet radio altitude.  This is in addition, to the words ‘autopilot’ being displayed on the PFD.

Using IAN – At What Distance Does IAN Work

IAN is not designed to navigate to the airport and its functionality will only be available when the  aircraft is in range of the airport runway; for a straight-in approach, this is at approximately 20 nautical miles.  However, this distance can be considerably less if the aircraft is not on a straight-in course to the runway. 

Important Point:

  • To give you the longest time from which to transition to an IAN approach, try to choose a suitable approach type (from the FMC) that exhibits a ‘more or less’ straight-in approach.

Using IAN – When to Arm and Engage IAN

  1. IAN can be armed at anytime after the Deviation Pointers are displayed on the PFD.  

  2. To arm/select IAN, the flight crew press the APP button on the Mode Control Panel (MCP) similar to performing an ILS approach.

  3. IAN is armed only after clearance for final approach has been received from Air Traffic Control (ATC).  By this time, the aircraft is probably on a straight-in approach.

  4. IAN cannot be used for STARS and is not designed to be engaged when the aircraft is ‘miles’ from the designated runway.  Transition to an IAN approach can be from any of several pitch/roll modes.

  5. IAN (if armed) engages automatically when the either the localiser or glide path is captured.

IAN should only be armed or engaged when:

  1. The guidance to be used for the final approach is tuned and identified on the navigation radio;

  2. An approach has been selected from the FMC database that has a 3 degree glide path;

  3. The appropriate runway heading is set in the course window in the MCP;

  4. The aircraft is on an inbound intercept heading;

  5. ATC clearance for the approach has been received; and,

  6. The approach guidance information is displayed on the PFD along with the lateral and vertical Deviation Pointers.

Disengaging IAN

IAN is either armed, engaged or not engaged. 

If you want to disarm IAN from the arm mode, it is a matter of pressing the APP button on the MCP; the light on the APP button will extinguish and the Deviation Pointers on the PFD will not be visible.

If you want to disengage IAN after it has captured either the localiser or glide path (or both), pressing the APP button on the MCP will do nothing.  In this scenario, to disengage IAN you will need to conduct a Go-Around by selecting TOGA, or change the pitch/roll mode (i.e. Level Change).

Disconnecting the autopilot and flying manually will also disengage IAN; the upside being that the Deviation Pointers will remain displayed on the PFD, until a different pitch/roll mode is selected.

Important Points:

  • If the navigation radio is not tuned to the localiser, the runway data will not be displayed until IAN is engaged, however, the Deviation Pointers will be displayed.

  • IAN can be armed whenever the aircraft is in range of the runway - in other words whenever the Deviation Pointers are displayed on the PFD.

  • When IAN is armed, the FAC and G/P display on the FMA is coloured white.

  • When IAN is engaged (localiser or glide path) the FAC and G/P on the FMA is coloured green.

  • IAN will only engage after capture of either the lateral (FAC) or vertical glide path (G/P).

  • When IAN has captured the glide path, SINGLE CH will be displayed in green in the PFD.

Using IAN - Set-Up and Procedure

The following procedures used for an IAN approach are derived from ILS procedures and are consistent for all approach types. 

  • Select the appropriate approach to use from the FMC database.  Ensure that the selected approach has a glide path.  Do not alter any of the approach constraints. 

  • Set the altitude of the glide path (from the FMC) in the MCP altitude window.

  • Fly the aircraft in whatever pitch/roll mode to the Initial Approach Fix (IAF).  Remember straight-in approaches are best, although offsets between 25 and 45 degrees may be used but not recommended. 

  • Configure the navigation radios to the correct frequency based on the approach type you have selected from the FMC database.  Do not use an ILS frequency.

  • Set the barometric minimums to the altitude published on the approach chart.  Add 50 feet to avoid breaking NPA protocols.

  • Set the correct runway approach course in the MCP course window.

  • Do not select IAN (press the APP button) until the aircraft is in the correct position relative to the approach course. 

  • When approximately 2 miles from the FAF - GEAR DOWN, FLAPS 15, SPEED CHECK.

  • At glide path capture (FAF) – FLAPS 25/30 (landing flaps), SPEED CHECK.

  • At 300 Feet below glide path capture, reset the MCP altitude window to the missed approach altitude.  Failure to wait until the aircraft descends 300 feet will cause the ALT HOLD annunciation to display and the aircraft levelling off.

  • At minima – Disengage autopilot and autothrottle, manually align aircraft to the runway, and follow the Deviation Pointers and Flight Director (FD) cues to the runway threshold.   Maintain the glide path to the flare and do not descend below the displayed glide path. 

Although glide path guidance can be used as a reference once the aircraft descends below the MDA, the primary means of approach guidance is visual.  If not visual at the MDA, execute a Go-Around.  Remember, using IAN is a NPA.

Important Points:

  • When using IAN the aircraft should be configured approximately 2 nautical miles from the FAF (this is one of the fundamental differences between an IAN approach and an ILS approach).

  • Often, the runway may not be aligned with the FMC generated course.  The FCTM states; ‘If the final approach course is offset from the runway centreline, manoeuvring to align with the runway centreline is required.  When suitable visual reference is established, continue following the glide path angle while manoeuvring to align with the runway.

  • Flying an IAN approach is an NPA; it is important to fly visually after passing the MDA.

  • The approach mode (APP on center CTR knob) on the EFIS can be selected when using IAN.  This will display the IAN approach on the Navigation Display as if it is an ILS approach.

Transitioning to an IAN Approach

A flight crew will usually transition to an IAN approach 2 nautical miles prior to the Initial Approach Fix (IAF).  

At this distance from the runway there is not a lot of time to configure the aircraft for landing, and if IAN engages when the aircraft is either above or below the glide path, there is a possibility that the aircraft will abruptly and unexpectedly ascend or descend as the automation attempts to capture the glide path.   Therefore, you must be in diligent that the aircraft’s altitude roughly matches the position of the Deviation Pointers when close to the FAF.

Techniques to Transition Smoothly to an IAN Approach

There are several techniques that can be used to ensure a smooth transition to an IAN approach.

By far the easiest technique to ensure a seamless transition without any abrupt lateral or vertical deviation, is to position the aircraft ‘more or less’ within one dot deviation of the localiser or glide path (Deviation Pointers) prior to selecting IAN. 

In this way you can follow (‘fly’) the Deviation Pointers and engage IAN when the aircraft is more or less aligned with the position of the pointers (similar to how an ILS approach is carried out).

Another technique, is to fly the aircraft until ALT HOLD is displayed in the FMA (assuming that the altitude set in the altitude window in the MCP is approximately 2 nautical miles from the FAF).  Then select IAN.  This should enable the aircraft to smoothly capture the glide path when reaching the FAF.

Importantly, if transitioning to IAN from VNAV, it is prudent to engage SPD INTV to manually control MCP speed.

 

FIGURE 1:  Visual representation of an IAN approach and transition from roll mode. (Copyright Boeing FCTM).

 

Increased Spatial Awareness

Any approach can be busy and it is easy to forget something.  Therefore, it is wize to create a circle at 2 miles from the FAF that can be displayed on the Navigation Display (NP).

One way to accomplish this is by using the FIX page in the CDU. 

In the LEGS page copy to the scratchpad the FAF (click the line on which the FAF is located).   Open the FIX page and upload the FAF (from the scratchpad) to the FIX entry.  To create a dashed circle at 2 nautical miles from the FAF, enter /2 to Line Select Left 1.

Important Points:

  • Maintaining the correct approach speed and altitude is paramount to a successful IAN approach.  If the aircraft is travelling too fast, slowing down after IAN has engaged can be difficult.  Likewise, if the aircraft is too high and IAN engages, the vertical descent can be steep as the aircraft attempts to follow the FMC generated glide path.

  • You must be vigilant and anticipate actions and events before they occur.

Using IAN - Situations To Be Attentive Of

Automation can have its pitfalls and IAN is no different.  However, once potential shortcomings are known, it is straightforward to bypass them.  The most common mistake, especially with virtual pilots, is not following the correct procedure.

Possible 'surprises' associated with an IAN approach are:

1.   Failing to configure the aircraft prior to IAN engaging in FAC and G/P mode.

Unlike an ILS approach, where configuration for landing is initiated when the aircraft captures the glideslope (usually some distance from the runway) during an IAN approach configuration for landing is initiated approximately 2 nautical miles from the FAF.  

If you have not configured the aircraft for landing prior to the capture of the glide path, there may be insufficient time for you to complete recommended actions and checklists.   

If you believe this will occur, there is no reason why configuration cannot occur at an earlier stage.

2.   Forgetting to set the Missed Approach Altitude (MAA) in the MCP.

Failing to wait until the aircraft has descended 300 feet below the glide path capture altitude to reset the MCP altitude to the MAA.  Failure will cause the ALT HOLD annunciation to display and the aircraft leveling off.

3.   Approaching the runway while not on the correct intercept course.

IAN operates flawlessly with straight-in approaches and to a certain extent with approaches up to 45 degrees from the main approach course, however, IAN will not engage if you approach the assigned runway at 90 degrees.  Nor will IAN engage if you are attempting to fly a STAR.

4.   Forgetting to set the initial glide path altitude in the MCP (from the FMC).

A common mistake is not setting the glide path altitude (from the FMC) in the MCP window when configuring the aircraft for an IAN approach.

ProSim737 and IAN

Installing IAN to ProSim-AR Avionics Suite

IAN forms part of the avionics suite, however, for IAN to function it needs to be selected (turned on) in the ProSim-AR IOS (Instructor Operator Station).  The same is for the Navigation Scales (if required).

To turn on IAN, open IOS: Settings/Cockpit Setup Options/Options and place a tick in the appropriate box beside IAN.  A restart of the ProSim-AR main module may be required for the change to take effect.

IAN was introduced to the ProSim737 avionics suite in December 2014.   For the most part, the functionality is reliable and operates as it should (see note 1).

As at writing, known issues are as follows (this may change with Version 3 software updates):

  • ProSim737 does not display the IAN runway data immediately following the engagement of TO/GA during the take-off roll. 

This is incorrect.  In the real aircraft, this information is displayed immediately following the engagement of TO/GA during the take-off roll while.  (further research required)

  • The colour of the approach guidance display (LNAV/VNAV) after TO/GA is engaged is currently white.  This is incorrect.  The colour should be green.

  • At 100 feet AGL, if IAN is engaged and the autopilot remains selected, a flashing AUTOPILOT warning in amber colour will be displayed on the PFD.   This is correct.  However, an audible ‘autopilot’ callout should also be heard.  This is not simulated.

Important Point:

  • ProSim737 users should also note, that for IAN to function within the avionics suite, it must be selected in the cockpit set-up page of the Instructor Station (IOS).

Note 1:   IAN works flawlessly for straight-in approaches (or approaches that are slightly offset).  However, the ProSim software when using some RNAV (RNP) approaches has trouble maintaining the correct vertical profile.

When a RNAV (RNP) approach (not AR) is selected, IAN arms and engages very late in the approach profile (after the FAF).  The altitude that IAN engages is well below the profile used in VNAV; this results in the aircraft diving to capture the IAN glide path.  Once the aircraft is established on the glide path IAN works as it is supposed to. 

The above scenario does not occur with every VNAV (RNP) approach; only those that exhibit a curved radius to fix (RF) profile or short leg profile to the runway threshold.

In the real aircraft (depending on operator and country of operation) IAN can handle all RNAV (RNP) approaches with the exception of RNAV (RNP-AR)  approaches.

In comparison, Precision Manuals Development Team (PMDG) NGX and NGXu can fly the above approaches in IAN.  This has been achieved by artificially replicating the approach using various hidden ‘waypoints’ that their software can read.  In effect, what you are seeing is the aircraft flying over the waypoints that have been overlaid onto the curves in the approach. 

I do not believe ProSim has replicated PMDG’s methodology in their software.

Therefore, if flying an RNAV (RNP) approach using IAN, select only those approaches that are ‘more or less’ straight-in without RF curves or turns; otherwise, use LNAV/VNAV.

BELOW:   Montage of four screen captures of the PFD showing some of the displays generated during an IAN approach (images upper left to right then bottom left to right).  Images 1-3 are sequential. Image 4 is standalone.

Image 1:  Aircraft is LNAV/VNAV approaching the IAF.  The aircraft is too far from the runway for IAN to be in range to operate (RJAA VOR Rwy 16R).

Image 2:  Aircraft is in range of RJAA localiser (tuned in the navigation radio).  Runway data is displayed from localiser and Deviation Pointers are displayed in outlined white-coloured diamonds (anticipation pointers).  The Deviation Pointers will change from white (outline) to magenta (either outline or solid) when either the localiser or glide path is captured.  FAC and G/P are displayed on the FMA in white indicating that IAN has been armed.  Note that if IAN was not armed, only the runway data and Deviation Pointers would be displayed (RJAA VOR Rwy 16R).

Image 3:  IAN has captured the localiser and the lateral Deviation Pointer is displayed as a solid magenta-coloured diamond.  FAC (in green) is displayed on the FMA.  The vertical Deviation Pointer is still in outline and in white (anticipation pointer), as is the G/P on the FMA.   IAN is tracking the localiser (RJAA VOR Rwy 16R).

Image 4:  IAN has engaged.  The runway data is now sourced from the FMC and not the localiser (as in the above examples).  The FMA displays FAC and G/P in green colour, SINGLE CH is displayed, and both Deviation Pointers are solid magenta-coloured diamonds.  IAN has captured the Glide Path (RJAA ILS X or LOC X Rwy 16L).

Montage of four screen captures of the PFD showing some of the displays generated during an IAN approach (images upper left to right then bottom left to right).  Images 1-3 are sequential. image 4 is standalone

Image 1: Aircraft is LNAV/VNAV approaching the IAF.  The aircraft is too far from the runway for IAN to be in range to operate (RJAA VOR Rwy 16R).

Image 2: Aircraft is in range of RJAA localiser (tuned in the navigation radio).  Runway data is displayed from localiser and Deviation Pointers are displayed in outlined white-coloured diamonds (anticipation pointers).  The Deviation Pointers will change from white (outline) to magenta (either outline or solid) when either the localiser or glide path is captured.  FAC and G/P are displayed on the FMA in white indicating that IAN has been armed.  Note that if IAN was not armed, only the runway data and Deviation Pointers would be displayed (RJAA VOR Rwy 16R).

Image 3: IAN has captured the localiser and the lateral Deviation Pointer is displayed as a solid magenta-coloured diamond.  FAC (in green) is displayed on the FMA.  The vertical Deviation Pointer is still in outline and in white (anticipation pointer), as is the G/P on the FMA.   IAN is tracking the localiser (RJAA VOR Rwy 16R).

Image 4: IAN has engaged.  The runway data is now sourced from the FMC and not the localiser (as in the above examples).  The FMA displays FAC and G/P in green colour, SINGLE CH is displayed, and both Deviation Pointers are solid magenta-coloured diamonds.  IAN has captured the Glide Path (RJAA ILS X or LOC X Rwy 16L)

Videos of IAN Approach

 

IAN APPROACH IN SIMULATOR

 
 

IAN APPROACH IN REAL 737-800 AIRCRAFT

 

Final Call

The use of Global Positioning Systems has enabled stabilised approaches at many airports, and the IAN system can take advantage of this technology to provide intuitive displays that support stabilised approaches on a consistent basis. 

Aircraft fitted with IAN are capable of using the APP button located on the MCP to execute an instrument ILS-style approach based on flight path guidance from the FMC.  This makes Non Precision Approaches easier to execute with increased safety.  It also enables a constant descent angle, less engine spooling, wear and tear, and improved passenger comfort.  Furthermore, IAN uses a standardised and consistent procedure, that in addition to improved displays and alerts,  can be used in place of LNAV/VNAV.

Nevertheless, a flight crew must be vigilant when using any automation, especially during the critical approach phase where there is little margin for error.  First and foremost is the innate ability to fly the airliner manually, and although automation such as IAN can enhance safety, it does so at the detriment of manual flying skills.

References

Several sources were used to obtain the information documented in this post, including: personal communication with a B737-800 pilot, the Boeing Flight Crew Training Manual and the Boeing 737 Technical Guide by Chris Brady.

If any discrepancies are noted in this article, please contact me so they can be rectified.

Acronyms and Glossary

  • AGL – Above Ground Level

  • APP – Approach button located on MCP

  • CDU – Control display Unit (glorified keyboard)

  • EFIS – Electronic Flight Instrument Display

  • FAC – Final Approach Course

  • FAF – Final Approach Fix

  • FMA – Flight Mode Annunciator

  • FMC – Flight Mode Computer

  • FMS – Flight Management System

  • G/P – Glide Path (Non Precision Approach / NPA)

  • G/S – Glideslope (Precision Approach / PA)

  • IAF – Initial Approach Fix

  • IAN – Integrated Approach Navigation

  • ILS – Instrument Landing System

  • IMC – Instrument Meteorological Conditions

  • MAP – Missed Approach Point

  • MCP – Mode Control Panel

  • MDA - Minimum Descent Altitude

  • ND – Navigation Display

  • PFD – Primary Flight Display

  • RA – Radio Altitude

  • RF – Radius to fix

  • RNAV (RNP-AR) Approach - RNP-AR is a subset of an RNAV approach that requites authorization (RA) to fly

  • Select – To select , arm or engage something

  • STAR  -  Standard Terminal Arrival Route

Review and Updates

  • 25 August 2017 - Review and content updated.

  • 03 December 2019 - Review and content updated.

  • 29 October 2019 - Review and content updated.

  • 28 April 2021 - Review and content updated.  Release of .pdf.

  • 21 December 2022 - Updated to latest procedure changes.

How To Calibrate Flight Controls in Flight Simulator Using FSX, Prepar3D or FSUIPC

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Imagine for a brief moment that you are driving an automobile with a wheel alignment problem; the vehicle will want to travel in the direction of the misalignment causing undue stress on the steering components, excessive tyre wear, and frustration to the driver. 

Similarly, if the main flight controls are not accurately calibrated; roll and pitch will not be correctly simulated causing flight directional problems, frustration and loss of enjoyment.

Flight controls are usually assigned and calibrated in a two-step process, first in Windows, then either by using the internal calibration provided in the FSX, Prepar3D, ProSim737, or using the functionality provided by FSUIPC.

It's often easier to think of calibrating controls as a two-stage process - Primary Calibration (in Windows) and Secondary Calibration (in Prosim737, flight simulator, or FSUIPC).

In this post, the method used to assign and calibrate the main flight controls (ailerons, elevators and rudder pedals) in FSX, Prepar3D and FSUIPC will be discussed.  Internal calibration in ProSim737 will not be discussed.  The common theme will be the calibration of the ailerons, although these methods can calibrate other controls. The calibration of the throttle unit will not be discussed.

Many readers have their controls tweaked to the tenth degree and are pleased with the results, however, there are 'newcomers' that lack this knowledge.  I hope this post will guide them in the 'right direction'.

STEP 1 - Calibrating and Registering Control Devices in Windows (Primary Calibration)

All flight controls use a joystick controller card or drivers to connect to the computer.   This card must be registered and correctly set-up within the Windows operating system before calibration can commence.  

  • Type ‘joy’ into the search bar of the computer to open the ‘game controllers set-up menu’ (set-up USB game controllers).  This menu will indicate the joystick controller cards that are attached to the computer (Figure 1). 

  • Scroll through the list of cards and select the correct card for the flight control device.  Another menu screen will open when the appropriate card is selected.  In this menu, you can visually observe the movements of the yoke, rudder pedals and any yoke buttons that are available for assignment and use.  The movement of the controls will be converted to either a X, Y or Z axis (Figure 1).

  • Follow the on-screen instructions, which usually request that you move the yoke in a circular motion, stopping at various intervals to depress any available button on the device.  The same process is completed for the movement of the control column (forward and aft) and the rudder pedals (left and right).  Once completed, click ‘save’ and the profile will be saved as an .ini file in Windows.

 

FIGURE 1:  Windows Joystick Calibration User Interface or Game Controller Interface in (Primary Calibration of joystick controllers)

 

Registration is a relatively straightforward process, and once completed does not have to be repeated, unless you either change or reinstall the operating system, or recover from a major computer crash, which may have corrupted or deleted the joystick controller’s .ini file. 

STEP 2 - Assigning Flight Control Functionality in FSX and Prepar3D (Secondary Calibration)

  • Open FSX or Prepar3D and select from the menu ‘Options/Settings/Controls’.  The calibration, button key and control axis tab will open (Figure 2).

  • Select the ‘Control Axis’ tab. When the tab opens, two display boxes are shown.  The upper box displays the joystick controller cards connected to the computer while the larger lower box displays the various functions that can be assigned.  The functions that need to be assigned are ailerons, elevators and rudders.

  • Select/highlight the appropriate entry (i.e. ailerons) from the list and click the ‘Change Assignment’ tab.  This will open the ‘change assignment’ tab (Figure 3).  Physically move the yoke left and right to its furthest extent of travel and the correct axis will be assigned.  To save the setting, click the ‘OK’ button. 

  • When you re-open the ‘Control Axis’ tab you will observe that the function now has an axis assigned and this axis is identical to the axis assigned by Windows when the device was registered.  You will also note a small box labelled ‘Reverse’.  This box should be checked (ticked) if and when the movement of the controls is opposite to what is desired (Figure 3). 

  • Save the set-up by clicking the ‘OK’ button.

 

FIGURE 2:  FSX Settings and Controls Tab (Prepar3D menus are similar)

 
 

FIGURE 3:  FSX Change Assignment Menu

 

STEP 3 - Calibrating Flight Controls in FSX and Prepar3D

The flight control functions that have been assigned must now be calibrated to ensure accurate movement.   

  • First, select and open the ‘Calibration’ tab.  Ensure the box labelled Enable Controllers(s)’ is checked (ticked) (Figure 4).

  • The correct joystick controller card must be selected from the list displayed in the box beside the controller type label.

Whether simple or advanced controls are selected is a personal preference.  If advanced controls are selected, the various axis assignments will be shown in the display box.  The axis, sensitivity and null zone can be easily adjusted using the mouse for each of the flight controls (ailerons, elevators and rudders). 

Concerning the sensitivity and null zone settings.  Greater sensitivity causes the controls to respond more aggressively with minimal physical movement, while lesser sensitivity requires more movement to illicit a response.  It is best to experiment and select the setting that meets your requirement.

The null zone creates an area of zero movement around the centre of the axis.  This means that if you create, for example, a small null zone on the ailerons function, then you can move the yoke left and right for a short distance without any movement being registered. 

Creating a null zone can be a good idea if, when the flight controls are released, their ability to self-center is not the best.  Again, it is best to experiment with the setting.  To save the settings click the ‘OK’ button.  

 

FIGURE 4:  FSX Settings and Controls

 

This completes the essential requirements to calibrate the flight controls; however, calibration directly within FSX or Prepar3D is rather rudimentary, and if greater finesse/detail is required then it's recommended to use FSUIPC.  

FSUIPC

FSUIPC pronounced 'FUKPIC' is an acronym for Flight Simulator Universal Inter-Process Communication, a fancy term for a software interface that allows communication to be made within flight simulator.  The program, developed by Peter Dowson, is quite complex and can be downloaded from the website.  FSUIPC allows many things to be accomplished in flight simulator; however, this discussion of FSUIPC, will relate only to the assigning and calibrating of the flight controls.

It's VERY important that if FSUIPC is used, the FSX or Prepar3D ‘Enable Controllers’ box must be unchecked (not ticked) and the joystick axis assignments, that are to be calibrated in FSX or Prepar3D be deleted.  Deleting the assignments in optional, however, recommended.  The flight controls will only function accurately with calibration from one source (FSX, Prepar3D or FSUIPC)

STEP 1 - Assigning Flight Controls Using FSUPIC

  • Open FSX or Prepar3D and from the upper menu on the main screen select Add Ons/FSUIPC’.  This will open the FSUIPC options and settings interface (Figure 5).

  • Navigate to the ‘Axis Assignment’ tab to open the menu to assign the flight controls to FSUIPC for direct calibration (Figure 6).

  • Move the flight controls to the full extent of their movement.  For example, turn the yoke left and right or push/pull the control column forward and aft to the end of their travel.  You will observe that FSUIPC registers the movement and shows this movement by a series of numbers that increase and decrease as you move the flight controls.  It will also allocate an axis letter.

  • At the left side of the menu (Figure 6) is a label ‘Type of Action Required’; ensure ‘Send Direct to FSUIPC Calibration’ is checked (ticked).  Open the display menu box directly beneath this and select/highlight the flight control functionality (ailerons, elevator or rudder pedals).  Check (tick) the box beside the function.

 

FIGURE 5:  FSUPIC Main Menu

 
 

FIGURE 6:  FSUIPC Axis Assignments

 
 
 

Calibrating Flight Controls Using FSUIPC

  • Select the Joystick Calibration’ tab.  This will open an 11 page menu in which you calibrate the flight controls in addition to other controls, such as multi-engine throttles, steering tiller, etc.  Select page 1/11 'main flight controls' (Figure 7)

  • Open the ‘Aileron, Elevator and Rudder Pedals’ tab (1 of 11 main flight controls).  Note beside the function name there are three boxes labelled ‘set’ that correspond to min, centre and max.  There is also a box labelled ‘rev’ (reverse) which can be checked (ticked) to reverse the directional movement of the axis should this be necessary.  The tab labelled ‘reset’ located immediately below the function name opens the calibration tool.  The ‘profile specific’ box is checked (ticked) when you want the calibration to only be for a specific aircraft; otherwise, the calibration will be for all aircraft (global).  The box labelled filter is used to remove spurious inputs if they are noted and for the most part should be left unchecked (not ticked).  The tab labelled ‘slope’ will be discussed shortly.

  • Click the ‘reset’ tab for the ailerons and open the calibration tool.  Move the yoke to the left hand down position to its furthest point of travel and click ‘set’ beneath max.  Release the yoke and allow it to center.  Next, move the yoke to the right hand down position to its furthest point of travel and click ‘set’ beneath min.  Release the yoke and allow it to center.  If a null zone is not required, click the ‘set’ beneath centre.

If a problem occurs during the calibration, the software will beep indicating the need to restart the calibration process.  The basic calibration of the yoke is now complete.  However, to achieve greater accuracy and finesse it is recommended to use null zones and slope functionality.

 

FIGURE 7:  FSUIPC Joystick Calibration (ailerons, elevator and rudder)

 

Null Zones

The null zone concept has been discussed earlier in this article.

If a null zone is required either side of the yoke center position, move the yoke to the left a short distance (1 cm works well) and click ‘set’ beneath centre.  Next, move the yoke 1 cm to the right and click ‘set’ beneath centre.  

As you move the yoke you will observe in the side box a series of numbers that increase and decrease; these numbers represent the movement of the potentiometer.  It is not important to understand the meaning of the numbers, or to match them.

Replicate the same procedure to calibrate the elevators and rudder pedals (and any other controller devices)

To save the setting to the FSUIPC.ini file click ‘OK’. 

It is a good idea to save the FSUIPC.ini file as if a problem occurs at a later date, the calibration file can easily be resurrected.  The FSUIPC.ini file is located in the modules folder that resides in the FSX or Prepar3D route folder.  

Slope Functionality

Slope functionality is identical to the sensitivity setting in FSX and Prepar3D.  Decreasing the slope (negative number) causes the controls to be more sensitive when moved, while a positive number reduces the sensitivity. To open the slope calibration, click the ‘slope’ tab.  This will open a display box with an angled line.  Manipulating the shape of this line will increase or decrease the sensitivity.

Slope functionality, like the null zone requires some experimentation to determine what setting is best.  Different flight controls have differing manufacturing variables, and manipulating the slope and null zone allows each unit to be finely tuned to specific user preferences.

Does FSUIPC make a Difference to the Accuracy of the Calibration ?

In a nutshell – yes.  Whilst the direct assignment and calibration in FSX and Prepar3D is good, it's only rudimentary.  FSUIPC enables the flight controls to be more finely adjusted equating to a more stable and predictable response to how the controls react.

Potential Problems

If using FSUIPC for axis assignment and calibration, remember to uncheck (not tick) the ‘enable controller’ box and delete the axis assignments in FSX or Prepar3D – only one program can calibrate and control the flight controls at any one time.  If calibration from both FSX or Prerpar3D and FSUIPC are used at the same time, spurious results will occur when the flight controls are used.

If the calibration accuracy of the flight controls is in doubt (spurious results), it is possible that the simulator software has inadvertently reassigned the axis assignments and enabled calibration.  

There's an intermittent issue in FSX and Prepar3D where the software occasionally enables the controllers and reassigns the axis assignment, despite these settings having been unchecked (not enabled).  If a problem presents itself, it's best to double check that this has not occurred.  This is why I recommend that the settings be deleted, rather than just being unchecked.

Final Call

Many enthusiasts are quick to blame the hardware, avionics suite, or aircraft package, when they find difficulty in being able to control the flight dynamics of their chosen aircraft.  More often than not, the problem has nothing to do with the software or hardware used, but more to do with the calibration of the hardware device.

The above steps demonstrate the basics of how to calibrate the flight controls - in particular the ailerons.  If care is taken and you are precise when it comes to fine-tuning the calibration, you maybe surprised that you are now able to control that 'unwanted pitch' during final approach.

Further Information and Reading

Documents relating to FSUIPC can be found in the modules folder in your root director of flight simulator on your computer.  The below link addresses how to calibrate the steering tiller.

Cost Index (CI) Explained

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Screengrab from CDU screen showing the Cost Index page in PERF INIT

The Cost Index (CI) function of the Flight Management Computer (FMC) is an important and often misunderstood feature of a modern airliner.  Apart from real-world cost savings in fuel, differing CI values alter airspeeds used during the climb, cruise and descent phase of a flight.  Certainly, the CI value is not a pressing issue for a virtual pilot flying a simulator, but to an operating airline in a fuel-expensive environment, differing CI values can equate to thousands of dollars saved.

CDU showing Cost Index.  A CI of 11 will generate significant savings as opposed to a value of 300.  FMC is produced by Flight Deck Solutions (FDS)

Simply explained, the CI alters the airspeed used for economy (ECON) climb, cruise and descent; it is the ratio of the time-related operating costs of the aircraft verses the cost of fuel.  If the CI is 0 the FMC calculates the airspeed for the maximum range and minimum trip fuel (lower airspeed).  Conversely, if the CI is set to the highest number, the FMC will calculate higher airspeeds (Vmo/Mmo) and disregard any cost savings.

In practice, neither of the extreme CI values is used; instead, many operators use values based on their specific cost structure, modified if necessary to the requirements of individual flight routes.  Therefore, the CI values will typically vary between airline operators, airframes, and individual routes.

Access to the CI is on page 1 of 2 in the ‘ACT PERF INIT’ page of the Control Display Unit (CDU) of the Flight Management Computer (FMC).  It is on the left hand side lower screen and displayed ‘COST INDEX’.  The range of the CI is 0-200 units in the Boeing 737 Classics and 0-500 units in the Next Generation airframes.

Fuel Verses Time and Money

There is a definite benefit to an airline’s fuel cost when the CI is used correctly.  Bill Roberson in his excellent article ‘Fuel Conservation Strategies: Cost Index Explained’ states the difference between a CI value of 45 verses a CI value of 12 for a B737-700 can be in the order of $1790 - $1971 USD depending upon the price of fuel; the time gained by selecting the higher CI value (CI-12) is in the area of +3 minutes.  Although these time savings appear minimal, bear in mind that airlines are charged by the minute that they remain at the gate.

Granted fuel savings are important, but so is an airline’s ability to consistently deliver on time, its passengers and cargo. It is a fine line between cost savings and time management, and often the CI will be changed before a flight to cater towards unscheduled delays, a change in routing, short or long haul flights, cost of fuel, aircraft weight, or favourable in-flight weather conditions (i.e. tailwind).

A higher CI value may be used by airlines that are more interested in expediency than fuel cost savings; the extra revenue and savings generated by an airline that consistently meets its schedule with less time spent at the gate may be equal to, or greater than any potential fuel savings.  Boeing realizes that as fuel costs increase, airlines are reticent to only expend what is absolutely necessary; therefore, Boeing works with its clients (airlines) to determine, based upon their operating style, the most appropriate CI value to use.

Changing CI on The Fly'

Although not standard practice, the CI value can be changed during the flight.  Any change in the CI will reflect on climb, descent and cruise speeds, which will be updated in the CDU and can be monitored via the 'progress' page of the CDU. 

 

Figure 1: compares the cost index values against climb, cruise, descent and recommended altitudes for the Boeing 757 air frame.  Although these figures do not relate to the Boeing 737-800 NG, they do provide an insight into the difference in calculated CI values for climb, cruise, descent and recommended altitude

 

Is the Cost Index Modelled in all Avionics Suites

The CI is modelled by the avionics suite, and whether it is functional depends on the suite used.  ProSim737 and Sim Avionics have the CI modelled and functional, as does Project Magenta (PM), Precision Manuals Development Group (PMDG) and I-Fly.  

Airline Cost Index Values

As stated above, the inputted CI value is variable and is rarely used at either of the extreme ranges.  The following airline list of B737-800 carriers is incomplete, but provides guidance to CI values typically used.  Note that the CI is variable and the values below may alter dependent upon airlines operations.  A more detailed list can be found on the AVSIM website (Thanks Dirk (ProSim737 forum) for the link).

  • Air Baltic CI – 28

  • Air Berlin CI – 30

  • Air France CI – 35

  • Air Malta CI – 25

  • Air New Zealand CI – 45

  • Austrian CI – 35

  • Fly GlobesSpan CI – 13-14

  • Fly Niki CI – 35

  • Hamburg International CI – 30

  • KLM CI – 15/30

  • Nord Star CI – 30

  • Norwegian CI – 15

  • QANTAS CI – 40

  • Ryanair CI – 30

  • SAS CI – 45-50

  • South African CI – 50

  • South West CI – 36

  • Thomson Airways CI – 9

  • Ukraine International Airlines CI – 28

  • WestJet CI – 20-25

The CI is an important feature of the avionics suite that should not be dismissed.  Whilst real-world fuel savings are not important during simulator flying, the altered airspeeds that a different CI value generates can have consequences for the distance able to be flown, climb, descent and cruise speeds.

Acronyms

  • CDU – Control Display Unit

  • CI – Cost Index

  • FMC – Flight Management Computer

  • Mmo – Maximum operating speed

  • Vmo – Maximum operating limit speed