Using The Tiller To Taxi The Boeing 737

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oem captain-side steering tiller. (737ng-info, 737controls, CC BY-SA 3.0)

To taxi an aircraft around the airport the pilot uses either the rudder pedals and/or a steering wheel device called a tiller.  The half-moon shaped tiller is mounted to the sidewall of the flight deck.  The number of tillers in an aircraft is not standard; some aircraft have one tiller while some have two.  The tiller controls the lateral movement of the aircraft’s nose wheel, located below and behind the flight deck.

The rudder pedals when pressed do provide some lateral movement, however, nose wheel steering is no more than 7 degrees.  To enable full lateral movement of the nose wheel  requires using the tiller with some forward thrust (called break-away thrust) from the aircraft’s engines.   

If the aircraft is to be moved backwards (for example from the ramp), then a push-back truck and ground controller is required.  The controller will connect a bar from the push-back truck to the main coupling of the nose wheel to lock the nose wheel in the forward position.  Once this is done, the push-back truck will lift the nose wheel enabling the aircraft to be reversed backwards.  A push-back truck can also be used to pull the aircraft forwards.

The ground controller will be in communication with the pilot and will instruct the pilot when it is safe to release the parking brake or start the engines (it is the responsibility of the ground controller, amongst other things, to check that the doors are closed and that personnel are clear of the aircraft).  Prior to the aircraft being moved, the pilot will speak with Air Traffic Control to obtain starting and push-back approval.

After ATC has given clearance, the pilot will:

  1. Check and cross check the taxi route instructions issued by ATC.

  2. Release the parking brake by pressing the upper section of the toe brakes.

  3. Apply forward thrust by advancing both thrust levers to around 32%.  The actual percentage N1 depends on the weight of the aircraft.  The forward thrust should not exceed 40%N1.

  4. Use the tiller to maneuver the aircraft.

  5. To stop the aircraft the thrust levers are brought back to idle, the toe brakes are pressed to stop any forward movement of the aircraft, and the parking brake applied.

Although not recommended, it is possible to aid in the turn by applying appropriate thrust only to one engine.

Important Points:

  • Reverse thrust should not be used to move the aircraft backwards primarily because of the likelihood on ingesting foreign material into the engine.

  • Whenever the aircraft is at a standstill the parking brake should be applied.

Taxi Speeds

Taxi speeds vary.  Generally, in good conditions the maximum permissible speeds are:

  • 10 knots – when doing turns;

  • 30 knots – when traveling in a straight-line along a runway;

  • 50 knots – when back-tracking along a runway; and,

  • If the runway is contaminated (ice, snow, etc) the taxi speeds are reduced to 5 knots.

How To Taxi

The nose wheel is located under and to the rear of the flight deck.  Therefore, to turn onto and follow the taxi lines accurately you must slightly overshoot the line prior to turning.

OEM Tiller

Another article addresses how to convert an OEM tiller and use in ProSim737 -  OEM tiller in ProSim737.

Final Call

With a little practice taxing the aircraft in the flight simulator is straightforward.  Points to consider are turning the nose wheel at the correct time (before crossing the line) and applying the correct amount of thrust based on aircraft weight.

Installing the Navigraph Database to ProSim-AR (ProSim737)

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No matter which avionics suite is used, the navigational database and approach charts will need to be kept up-to-date.  Navigraph (the company) have for many years been the mainstay in supplying accurate navigational data to the flight simulator community.

The navigation database and monthly updates can be downloaded from the Navigraph website, and can either be manually installed to Flight Simulator, or alternatively you can use Navigraph’s FMS Data Manager software to install the files.

This short article will benefit only those using the ProSim-AR (ProSim-737) avionics suite Version 3.  ProSim-AR Version 2 uses a different file structure and navigation path.

Database Files and Installation

Navigraph is the navigation database used by ProSim737.   The database is purchased separately to ProSim-AR and navigation updates (AIRAC cycles) are released monthly.

The correct navigational database for ProSim737 to download from the Navigraph website is: ProSim737 2.24b1 (and above).

When installed the database consists of three files:

  • cycle.json;

  • cycle_info.txt; and,

  • nd.bb3.

Cycle-info.txt is a text file that indicates which navigation database has been installed.  This is the file you need to open if you are unsure of which AIRAC cycle has been installed.  The other two files relate directly to the database.

Once the database is installed or updated, the ProSim737 main module (.exe file) must be run, and the database rebuilt.

To rebuild the database, open the ProSim main module, select Config/Database and Build Database.  The process to rebuild the database will take around 5 minutes.  When completed, the installed database AIRAC cycle number will be displayed.

Database Fails to Update

If the database does not update, there is a possibility that either the downloaded file is corrupt, or more than likely the database has been installed to the incorrect folder structure within ProSim-AR.

In this case, download the required files from Navigraph, uncompress the files to your computer desktop (or anywhere else) and copy the three database files to:

C:/Program Data/Prosim-AR/Navdata.

FMS Database Manager Mapping page.  This is where you select the folder structure to upload the AIRAC cycle to

FMS Data Manager

Navigraph have an installer (FMS Data Manager) which is a standalone program that is free to use.  The Data Manager is quite a powerful program and it’s worth the effort examining what this software can do.

When setup correctly, the installer will download, uncompress, and install the Navigraph files to the correct folder structure with ProSim.  The installer also will create a backup of the existing database (if selected).

Navigraph FMS Data Manager main front page.  This is the page where you select Update to update the navigational database with the latest AIRAC cycle

To ensure that the database is installed to the correct folder on your computer, the Data Manager must be configured correctly.  This can be done a number of ways, however, the easiest and most straightforward way is to setup the folder structure manually.

  • Open the FMS Data Manager and select Addon Mappings.

  • Select the black coloured folder adjacent to the purple coloured box named Manual.

  • Select the correct folder in your computer (C:/Program Data) and save the configuration.

To update the database, navigate back to the front page of the manager and select the check box adjacent to ProSim737 2.24b1 and select update.

ProSim-AR (ProSim737) main menu showing the Config page open with the Build Database page overlaid

Important Points:

  • Whenever you install or update the Navigraph database, rebuild the database and check the AIRAC cycle.

Final Call

Maintaining the navigation database is important if you are to get the most from Flight Simulator.  Navigraph AIRAC cycles are released monthly, and it stands to reason that the FMS Data Manager should be used to streamline the installation process.  Problems, when they do occur, usually relate to the FMS Data Manager trying to install files to the incorrect folder structure.

Reverse Thrust Procedure

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The reverse thrust levers are clearly visible in the first detent position.  OEM throttle quadrant converted for flight simulator use

Pilots tend to be numbers-orientated individuals.  They like concise instructions and do not like ambiguity.  Nor do they like being presented with something that is in ‘shades of grey’ rather than ‘black and white’. 

When, how, and for how long to deploy the reverse thrust (reversers) falls into the 'grey area'.

In this article, I will endeavour to unravel some of the uncertainties as to when and how to use reverse thrust.  I will also briefly discuss the relationship between the use of the autobrake and reverse thrust.

I am not going to delve deeply into every environmental consideration that needs to be analysed prior to the use of reverse thrust; this information is more than readily available from the Flight Crew Operations Manual (FCOM), Flight Crew Training Manual (FCTM) and other specific airline policy documentation.

Reverse Thrust Basics

Reverse thrust (reversers) is used only for ground operations and is used after touchdown to slow the aircraft;  it is used to reduce the stopping distance, minimise brake temperatures and decrease wear and tear.

Reverse thrust comprises four détentes and an interlock position, that are engaged by moving the thrust levers from the stowed down position through to the fully up position.  

  1. No reverse thrust (thrust levers are closed / stowed position).

  2. Detent 1 (idle reverse / thrust levers are at first position).

  3. Detent 2 (thrust levers are at second position).

  4. Full maximum reverse thrust (thrust levers are at fully upward position).

Between detent 1 and full maximum reverse thrust there is scope for the thrust levers to be positioned part way; thereby, altering the amount of thrust generated.

Schematic showing various positions for the thrust reverser levers

The interlock mechanism is felt when the reverse thrust levers are advanced to detent 1. The purpose of the interlock is to restrict movement of the reverse thrust lever until the reverser sleeves have approached the deployed position.

The procedure to use reverse thrust is very straightforward, however, questions arise as to whether to use detent 2 or full maximum reverse thrust, and when to begin reducing thrust and for how long.

Procedure

Following touchdown, without delay, move the reverse thrust levers to the interlock position and hold light pressure until the interlocks release (as the sleeves move rearwards).

For most landings, detent 1 and detent 2 will usually provide adequate reverse thrust (for normal operations).  If additional reverse thrust is needed (wet, slippery or short field landing), full maximum reverse thrust can be selected by raising the thrust levers past detent 2 to full maximum reverse thrust.  

To come out of reverse, the reverse thrust levers are returned to the detent 1 position, the engine allowed to spool down, and the levers then returned to the stow position.

Practically speaking, after touchdown maintain reverse thrust as required up to maximum thrust until the airspeed approaches 60 knots. Reverse thrust is then slowly reduced to detent 1 and then to reverse idle by taxi speed. Wait until the generated reverse thrust has bleed off, then slowly close the reversers and place them in the stow position.

Bringing the reverse thrust levers to detent 1 is important because it prevents engine exhaust re-ingestion and minimises the risk of foreign object debris (FOD) ingestion.  Idle thrust also bleeds off forward thrust from the engines.

The autobrake is disarmed when a safe stop of the aircraft is assured, or when the aircraft reaches taxi speed.

Important Point:

  • If transitioning from using the autobrake to manual braking, use reverse thrust as required until reaching taxi speed and then disarm the autobrake.  

Disarming the autobrake before closing reverse thrust provides a relativity seamless transition which increases passenger comfort (there is no aircraft jolt).

Conditions Required To Engage Reverse Thrust

The reversers can be deployed when either of the following conditions occur:

  1. The radio altimeter senses less than 10 feet altitude;

  2. When the air/ground sensor is in ground mode; and,

  3. When the forward thrust levers are in the idle position.

Until these conditions occur, the movement of the reverse thrust levers is mechanically restricted and the levers cannot be moved into the aft position.

It is important to always deploy reverse thrust as soon as possible following touchdown.  Do not wait for the nose wheel to touch down, but engage reverse thrust when the main wheels are on the runway.  Timely deployment will increase stopping power; thereby, increasing safety and reducing heat build-up in the brake system.  

A study determined that there was roughly a 17 second difference in stopping time when reverse thrust was deployed immediately the landing gear was on the runway as opposed to waiting several seconds for the nose gear to also be on the runway - reverse thrust is most effectual at high airspeeds and its effect decays on a linear scale as forward airspeed decreases.

Important Points:

  • Reverse thrust should always be used with the autobrake, unless the runway is exceptionally long without a possibility of runway overrun (the reason for this will be explained shortly).

  • When closing the reversers, always pause at detent 1.  Monitor the REV thrust output on the Primary Engine Display (center panel) and stow the reversers only after reverse thrust has dissipated.

Call-outs

The pilot monitoring usually makes the following call-outs:

  • ‘60 knots’;

  • ‘Reversers normal’ -  when both REV indications are green;

  • ‘No reverser engine No: 1’ - if no REV indication or colour is amber; or,

  • ‘No reverser engine No: 2’ -  if no REV indication or colour is amber; or,

  • ‘No reversers’ -  if no REV indications or colour is amber.

NOTE:  Annunciators and displays are discussed later in the article.

During landing, the pilot monitoring (PM) should call out 60 knots to advise the pilot flying (PF) in scheduling the reduction of reverse thrust.  

When landings are in conditions that are suboptimal (heavy rain, snow, slush, etc), some operators stipulate that the PM operate and control the reverse thrust .  This enables the PF to concentrate solely on the landing roll out rather than having the extra responsibility of also controlling the reverse thrust.  

This said, although this procedure may lower pilot workload, it can cause problems when the PF is landing on a slippery runway or in marginal crosswind conditions.   At these times, the PF may wish to use the reverse thrust in conjunction with the brakes and there is little time to call out instructions to the PM.

Technical Aspects (basic operation)

Each engine on the Boeing 737 Next Generation is equipped with an hydraulically operated thrust reverser, consisting of left and right translating (moving) sleeves.  Aft movement of the reverser sleeves cause blocker doors to deflect fan discharge air forward, through fixed cascade vanes, producing reverse thrust.  

Hydraulic pressure for the operation of the thrust reversers comes from hydraulic systems A and B, respectively.  If hydraulic system A and/or B fails, alternate operation for the affected thrust reverser is available through the standby hydraulic system.  When the standby hydraulic system is used, the affected thrust reverser deploys and retracts at a slower rate and some thrust symmetry can be anticipated.

When reverse thrust is selected an electro-mechanical lock is released.  This causes the  isolation valve to open which results in the thrust reverser control valve moving to the deploy position, allowing hydraulic pressure to unlock and deploy the reverser system.

The system is designed in such a way that an interlock mechanism restricts movement of the reverse thrust lever until the reverser sleeves are in the deployed position.

Closing the thrust levers past detent 1 to the stow position initiates the command to stow the reverser.  When the lever reaches the full down position, the control valve moves to the stow position allowing hydraulic pressure to stow and lock the reverser sleeves.  After the thrust reverser is stowed, the isolation valve closes and the electro-mechanical lock engages.

Relationship with Flaps

There is an interesting relationship between the use of reverse thrust and flaps 40.

When the aircraft has flaps 40 extended, the drag is greater requiring a higher %N1 to maintain airspeed. This higher N1 takes longer to spool down when the thrust levers are brought to idle during the flare; this enables more energy to be initially transferred to reverse thrust.

Therefore, during a flaps 40 landing more energy is available to be directed to reverse thrust, as opposed to a flaps 30 landing.

Annunciators and Displays

Thrust reverse indicators are displayed in the Primary Engine Display located in the center panel slightly above the No: 1 and No: 2 %N1 indicators.  When reverse thrust is commanded, REV will be displayed initially in amber followed by green dependent upon the position of the thrust reverse levers.

  • Amber:  Thrust reverser has been deployed from the stowed position and both sleeves have travelled ~10-90% to the deployed position.

  • Green:  Thrust reverser has been deployed from the stowed position and both sleeves have travelled greater than 90% to the deployed position.

When either reverser sleeve moves from the stowed position, the amber REV indication annunciator, located on the upper display will illuminate.  As the thrust reverser reaches the deployed position, the REV indication illuminates green and the reverse thrust lever can be raised to detent 2.  

Electronic Engine Control (EEC) panel (AFT overhead). ProSim737 avionics suite virtual display

Additional reverse thrust annunciators are located on the aft overhead panel in the Electronic Engine Control (ECC) panel.  These annunciators are triggered by the retraction of the reverse thrust levers to the stow position.   

The annunciators will illuminate during a normal reverse thrust / stow operation for 10 seconds and then extinguish 10 seconds later when the isolation valve closes.  

A system malfunction has occurred if the reverser (REV) annunciator illuminates at any other time, or illuminates for more than approximately 12 seconds (in the later instance, the master caution and ENG system annunciator will also illuminate).

Possible reasons for a system malfunction are that the isolation valve, thrust reverser control valve, or one or both of the thrust reverser sleeves are not in their correct position.

Autobrake and Reverse Thrust Use (the grey area)

Both the autobrake and timely application of reverse thrust can be used to slow the aircraft, however, both come at a cost.  

Using the autobrake generates considerable heat in the braking system, translating to increased expenditure in maintenance and possible delays in turn around times (waiting for brakes to cool to operational temperature).  Conversely, reverse thrust consumes excess fuel.  Clearly there is a middle point where each will cancel out the other.

The immediate initiation of reverse thrust at main gear touchdown, and use of maximum reverse thrust, enable the autobrake system to reduce brake pressure to the minimum level – this is because the autobrake system senses deceleration and modulates brake pressure accordingly.  Therefore, the proper application of reverse thrust results in reduced braking and less heat generation for a large portion of the landing roll.

Based on this premise, it stands to reason that this is why Boeing recommend to use the autobrake in conjunction with reverse thrust.

Boeing states in the FCTM that: ‘After touchdown, with the thrust levers at idle, rapidly raise the reverse thrust levers up and aft to the interlock position, then to reverse thrust detent 2.  Conditions permitting, limit reverse thrust to detent 2’.

It appears to be Boeing’s intention to use reverse thrust as the major force to stop the aircraft, and as the use of maximum reverse thrust further minimises brake system heating, it would appear to be a preferred choice, despite the FCTM stating detent 2 is the preferred position for normal operations.

The official literature does not satisfactorily address this ‘grey area’   The result being that many 737 pilots use differing techniques when deploying and stowing the reversers.

Various Methods

If you observe how other pilots use the reversers, you will discover that there are several variations that follow the same theme.

1.    A pilot will, when the aircraft passes through 60 knots, close reverse thrust by lowering the reverse thrust levers through detent 1 to the stow position without stopping at detent 1;

2.    Try to locate detent 1 by ‘feel’ resulting in pushing the levers too far towards the stow position, causing forward thrust to unexpectedly occur momentarily;

3.    Deliberately close maximum reverse thrust at the 60 knots by placing the reverse thrust levers into the stow position.

In the above three scenarios, the reverse thrust levers have not been allowed to pause at  the detent 1 position.  Pausing at detent 1 is important as %N1 requires several seconds to reduce to idle thrust after maximum reverse thrust has been used, and it is during this ‘wind down’ period, as the reverse sleeves fully close, that %N1 will transition through 55-60%N1, which is forward thrust.  

By not allowing the reversers to pause momentarily at detent 1, to enable thrust to disparate below 55-60%N1, may cause the aircraft to momentarily accelerate.  This can be rather disconcerting, especially on a short field landing or landing in marginal conditions.

So What Do I do (normal procedure)

  1. At touchdown I engage reverse thrust – either detent 2 or maximum reverse thrust (or part thereof).

  2. Approaching 60 knots I slowly and smoothly retard the reverse thrust levers to detent 1.

  3. I always allow a few seconds at detent 1 to enable %N1 to dissipate.

  4.  Approaching taxi speed I disarm the speedbrake and close the reversers.

  • At no time do, unless in an emergency, do I close the reversers suddenly; I always close the reversers smoothly and slowly. This enables %N1 to dissipate gradually.

Final Call

The procedure to deploy reverse thrust is straightforward and very easy to accomplish, and there is little argument that reverse thrust should be used on all, but the longest runways in optimal environmental conditions.   However, there is confusion and often disagreement to when the reversers are deployed, whether maximum reverse thrust should be used, and for how long the reversers should be left in the open position before retraction and stowing.

It is unfortunate that the information written in the Flight Crew Training Manual (FCTM) and Flight Crew Operations Manual (FCOM) does not provide a more objective ‘black and white’ answer to this procedural dilemma.

Video

The below video shows the REV indicators on the Primary Engine Display (when reverse thrust is commanded) and the REVERSE annunciators on the ECC panel (AFT overhead).  Video taken directly from ProSim-AR 737 avionics suite (virtual software).  Video upload to U-Tube rather than VIMEO).

 
 

Circle-to-Land Approach Procedure

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Although a circle-to-land is a VFR approach, it is recommended to use whatever automation and equipment is available.  This includes the FMC to generate waypoints and radials to increase situational awareness (Petr Beran, Aerosvit Boeing 737-400 on final approach into Tivat Airport, CC BY-SA 4.0)

Landing can be a challenge to new virtual flyers, and this is especially so when there are so many different types of approaches that an airline pilot can use.  Often the approach selected is based on environmental conditions, the type of equipment used in the aircraft, and the type of equipment and technology available at the airport.

This article will explain the technique used in circle-to-land (CTL) approaches.  I have purposely tried to simply the details to cater to all levels of experience.  However, aviation often is not a simple subject; issues can be complex and overlap.

What is a Circle-to-Land

A circle-to-land approach is similar to entering a VFR traffic pattern, but you are following a published approach prior to entering the pattern directly.  A CTL is an hybrid between a standard non-precision visual approach and a precision approach; you use information gleaned from the circle-to-land information block on the chart in a 100% visual environment.   

The initial approach used can be either a precision or non-precision approach. RNAV (GPS), NDB, VOR and ILS approach types are allowed, however, only CAT 1 approaches can be used (CAT 2 & CAT 3 approaches cannot be used).   It is important to realise that if an ILS is used, you do not fly the ILS.  Rather, you fly the Localizer and use Vertical Speed (V/S) to descend at the appropriate rate of descent (following the ILS vertical guidance).

Although the approach is VFR, you still utilise whatever instruments necessary to increase spatial awareness and lower pilot workload.  The autopilot, autothrottle and vertical speed are often used during the approach, however, this is not a hard and fast rule and flying the aircraft manually is allowed.  Boeing recommend the use of the autopilot when intercepting the landing profile.

The approach is usually executed at a low altitude; typically 1000 feet AGL within a defined boundary around the airport (usually a 4.5 nautical mile ‘protection area’).  This is in contrast to a standard visual traffic pattern whereby an altitude of ~1500 feet AGL is used.  

Approach chart for Hobart, Tasmania (YMHB).  Note the circle-to-land information block outlined in red.  Also note the MDA and visibility for a Category C aircraft highlighted in yellow © Navigraph/Jeppesen

MDA and Speed Management

The minimum altitude that the CTL is to be flown is specified by the MDA, while the minimum required visibility and other pertinent points are displayed in the circle-to-land section of the approach chart (see chart diagram).   The general rule is that if something is not prohibited, then it is allowed.  If there is no note on the chart prohibiting a CTL then circling to land is implicit.

The MDA is the lowest altitude that you can descend to when conducting a CTL.  This said, there is absolutely no reason why you must descend to this altitude.  Providing horizontal visibility is within range, often a higher altitude (similar to a pattern altitude) will make the approach easier.  If using a higher altitude than the MDA, ensure you do not exceed the boundary as defined by the 'protected area'.

Speed management and a stabilised approach is paramount, as the aircraft is relatively low to the ground and is in landing configuration.  The aircraft’s speed should not be below Vref+15 (approximately 160 kias) as the aircraft will need to be banked in a standard 25 degree turn when it has reaches the MDA.  The final approach speed and descent occurs during the turn to short final and on final.

NOTE:  I purposely have not discussed ICAO and US TERPS.  If you want to read about the differences between the two protocols, navigate to Skybrary.

Circle-to-Land Procedure

  1. Consult the approach chart to determine the Minimum Descent Altitude (MDA).  Whatever this figure is, round the number up to a even number by adding 100.  For example, if the MDA is 1430 feet round the number to the nearest 100 feet, which is 1500 feet.  Dial this altitude into the altitude window on the MCP (if desired, a higher altitude to the published MDA can be used). 

  2. Fly the Localiser and use V/S to alter your rate of descent.  Speed management is important.  Although not required, it is a good idea to adjust your heading selector on the MCP to read 45 degrees either left or right of the localiser course.  This saves you doing it when the aircraft reaches the MDA.

  3. The landing gear and flaps(flaps 15) are to be extended no later than the MDA.  However, if necessary this can be done prior to the MDA to aid in establishing a stabilised approach (for example, between 10 and 7 nautical miles from the runway).  The speed brake should be armed.

  4. Fly the localiser to the MDA until ALT HOLD (ALT ACQ will be displayed on the FMA) and level off at the MDA.  Set the Missed Approach Altitude (MAA) in the altitude window on the MCP.  If you are not visual by this stage, a Go Around must be executed.  Note that is if VNAV is being used select ALT HOLD on the MCP (this will disable VNAV).

  5. Press Heading Select (HDG SEL) on the MCP.  The aircraft will turn 45 degrees L/R at a 25 degree bank (assuming you preset the HDG SEL as mentioned earlier).  Once the wings are level (more or less by a few degrees) continue to fly this course for 20 seconds.  Use the timer to record the elapsed time.

  6. After 20 seconds has elapsed (some procedures suggest 30 seconds), adjust your heading (HDG SEL) to fly downwind (the original localiser course).  Fly this heading until the aircraft is abeam of the runway threshold (the triangle that represents the aircraft on the ND should align with the end of the runway).  Either look out of the window to gauge your position and/or use the Navigation Display to check the aircraft’s position in relation to the runway.

  7. Start the clock when the aircraft is abeam of the runway and fly outbound for 3 seconds per 100 feet AGL.  For example, if the MDA is 1500 feet, you divide 1500 by 100 and times by 3 to determine the time (t) of the outbound leg – which is 45 seconds  (t=1500/100*3).

  8. When 45 seconds has elapsed, call for landing flaps, adjust the speed, and set the HDG SEL on the MCP to the runway heading.  Begin a descent using V/S at 300 fpm and complete the landing checklist. 

It is recommended to use the position trend vector on the Navigation Display, in conjunction with outside references (runway PAPI, etc), to judge the turn.  The aircraft’s bank should not exceed 25 degrees during the turn.  

The prevailing wind and distance from the runway will determine if the turn is continuous or to base and then final. 

If using the autopilot, remember to adjust the bank angle selector accordingly, otherwise the aircraft’s bank may exceed stipulated parameters.  Intercept the normal visual glide path (final) and disconnect the autopilot and autothrottle.  Verify that the missed approach altitude is set on the MCP and recycle the Flight Director switches (if required).

After disconnecting the autothrottle, an initial 'good' thrust setting is around 55%N1; from this point you can increase or decrease thrust to maintain Vref+5.  Also, as you turn to final, glance at the runway PAPI lights and adjust vertical speed accordingly.  As a  rough guide:

PAPI Lights

4 RED - do nothing (maintain V/S).

3 RED - increase V/S to 500 fpm.

2 RED - increase V/S 800-850 fpm

1 RED - increase V/S 1000 fpm

9. If the MDA is breached or visual references are lost, a Go Around must be executed.  Depending upon the aircraft’s position, climb to the Missed Approach Altitude (MAA) remaining in the ‘protected area’ (fly in circles) 

If a Go Around is executed prior to the final approach, always turn the aircraft in the direction of the runway, as this will ensure the aircraft remains in the ‘protected area’.

Winds

Any tail or crosswind must be taken into consideration.  Failure to do so will place the aircraft in the wrong position relative to the approach.

To correct for wind, you take half the tail component and subtract it from the outbound time.  For example, if the tail component is 5 knots and the outbound time is 24 seconds, you would subtract 5 from 24 giving you an adjusted time of 19 seconds.

Another way to determine this is to press the progress page (page 2) on the CDU (PROG)

and halve the tailwind component displayed.

The Navigation Display showing several aids that have been used to facilitate a circle-to-land on runway 30 at Hobart, Tasmania (YMHB).  A circle ring at 4 mile, a radial (030), and a point/bearing/distance waypoint (RW301).  The heading bug has been preset to a turn of 45 degrees

Aids to Increase Spatial Awareness

Although this is a visual only approach, there is no reason not to use whatever tools are at hand to increase spatial awareness and make the approach a little easier. 

Use the CDU to:

  1. Make a waypoint (Place/Bearing/Distance waypoint) at whatever distance desired that is adjacent to the runway.  This waypoint will act a point in space that the turn to base is made. 

  2. Note that this waypoint/fix is only for added reference and is not a point from which to create a route.

  3. Create a radial 90 degrees from the end of the runway.  This will display a straight line from the runway that will be a visual reminder when the aircraft is abeam of the runway.

  4. Create distance rings.  The rings are displayed on the Navigation Display.  At the very least, a ring should  be used to delineate the 'protected area' around the airport.  Further rings can be used to help show the MDA and other flight specific events.

  5. Use the Vertical Bearing Indicator (VBI).  The VBI provides a defined vertical speed that can be used as a reference to the correct 3 degree glide path.

How to make a distance ring, radial, waypoint, and use the Vertical Bearing Indicator (VBI)

Although this has been mentioned elsewhere on this website, a review is in order.  In the following examples I will use the approach chart YMHB Runway 30 (see chart diagram below).  This is a VOR approach, however, it could equally another approach type.  LSK1L means Line Select 1 Left.

NOTE:  There are differences between avionics suites.  ProSim737 use the acronym RW to define a runway.  PMDG use RWY.

Before continuing, the following functionality overlaps with each other.  Therefore, it is easy to become discombobulated.  When you are in the simulator you will find it makes sense.

Distance Rings

Distance rings are created from the FIX page in the CDU.

  1. Open the FIX page and type into the scratchpad a known waypoint or navaid (For example YMHB or RW30). 

  2. Up-select the identifier to the FIX page (LSK1L).   A dashed-green coloured circle will be displayed around the waypoint in the Navigation Display.

  3. To enlarge the ring to a desired distance around the waypoint, type into the scratchpad the distance (for example /2).  Up-select this to LSK2L.  This will display the ring around the waypoint at a distance of 2 miles.

Creating a Radial to a Specified Waypoint

To create a radial a set distance from a known point (waypoint/navaid).  For example RW30.

  1. Open the FIX page and type into the scratchpad the desired waypoint/navaid, bearing vector and distance. 

  2. Type into the scratchpad the bearing and distance of the radial wanted (for example 030/2).

  3. Up-select this to the appropriate line in the FIX page (LSK2L).  For example, entering RW30030/2 will create a green dashed line along the 030 bearing to intersect with a circle surrounding RW30 at a distance of 2 miles.

  4. If you want the point (where the line insects the circle) to become a waypoint, read the next section.

Creating a Specified Waypoint (Place/Bearing/Distance Waypoint)

There are a few ways to do this.   I have discussed one way (which works with ProSim737).

  1. Type into the scratchpad RW30.  This will create a green coloured circle around RW30 on the Navigation Display (ND).  

  2. Type in the scratchpad the bearing and distance (030/2). 

  3. Up-select this information to the FIX page (LSK2L).  This will place a green-coloured radial at 030 degrees from RW30 that intersects the circle at 2 miles on the ND.

  4. Next, select the 030/2 entry from the FIX page (press LSK2L).  This will copy the information to the scratchpad.  Note the custom-generated name - RW30030/2.

  5. Open the LEGS page and up-select the copied information to the route.  Press EXECUTE. 

  6. RW30030/2 will now have an amended name - RW301.  Note that RW301 will form part of the active route.

  7. Copy RW301 to the scratchpad.

  8. Open a new FIX page (there are 6 FIX pages that can be used). 

  9. Up-select RW301 to the FIX page (LKL1L).  This will create a circle around RW301 on the ND.

  10. To remove the waypoint (RW301) from the route, open the LEGS page and delete the entry. 

  11. Press EXECUTE. 

RW30 will be displayed on the Navigation Display

There is a less convolted way to do this, however, the method is not supported by ProSim737.

VBI

To input a variable into the VBI, an appropriate approach must be selected from the ARRIVALS page.  This approach information can be deleted from the route after the information for the VBI has been generated.

  1. Select the DEP/ARR page in the CDU.

  2. Select ARR and then select RW30. RW30 is shown on the last page.

  3. Choose a desired distance to generate a runway extended line (RWY EXTLSK3R).

  4. Open the LEGS page and close any discontinuity; or,

  5. Delete all entries except RW30 (unless wanting them).  Ensure RW30 is the active leg (LSK1L).  The entry will be coloured magenta. 

  6. Press EXECUTE. 

Open the VBI by pressing DES on the CDU.  RW30 should be displayed in the VBI.

Important Points:

  • A quicker way to do this is to select RW30 to the scratchpad and then up-select to the upper most entry (LSK1L).  This will delete all entries except this one (assuming you do not want other entries).

  • When loading an approach, often a RX-XX will be displayed.  The RX-XX waypoint is not part of the database but is a generated waypoint based on the approach type selected (it will have a different altitude).  Do not use the RX-XX entry (delete it).

 

Diagram 1: representing a circle-to-land approach © Boeing FCOM

 

Go Around

To perform a Go Around using a published missed approach you need to enter the missed approach details into the FMC (the missed approach is displayed in the LEGS page immediately AFTER RW30).

  1. Select DEP/ARR in the CDU and select an approach for Runway 30.  This will display in the LEGS page an appropriate approach, runway and a missed approach.

  2. Open the LEGS page and delete all entries prior to runway 30 (RW30) and clean up any discontinuity.  Check the LEGS page to ensure the runway and missed approach are correct.

Important Points:

  • A circle-to-land approach can only be conducted when the pilot flying is able to see the airport and runway.  If at anytime visual reference is lost, a Go Around must be executed.

  • The aircraft must not descend below the Minimum Descent Altitude (MDA)  stipulated on the approach chart.  Although the aircraft must not descent below the MDA, a higher MDA can be used if desired.

  • The initial approach can be flown using one of several chart types.  If using an ILS approach it is recommended to not engage the ILS mode (if you do, ensure you do not accdently descend past the MDA - change out to V/S prior to reaching the MDA).  If using an RNAV approach make sure that VNAV is disengaged at the MDA.

  • Speed management is critical as you are flying at low altitude in landing configuration.  A stable approach is paramount.

  • Do not construct a route in the CDU to overlay onto the circle-to-land route.  The procedure is designed to be flown using HDG SEL. 

  • The circle-to-land is VFR.  Do not end up 'tail-up' with your head in the CDU.  Look outside!

      To learn why an overlay is not recommended, watch this video by Mentour Pilot.

Recommended Actions:

To aid in spatial awareness the following actions are suggested:

  • If the Captain is flying the aircraft, try and turn right as this will place the airport on the left side of the aircraft enabling the pilot flying better visual reference.  Vice versa if the First Officer is the pilot flying (unless the direction is stipulated otherwise in the approach chart).

  • Use the CDU to create distance rings and a waypoint/radial.  Use the VBI.

Flight Simulation - avionics suite

Unfortunately, not all flight simulation avionics suites are identical to each other.  This is readily apparent when using the CDU to program the FMC.  Users report subtle difference between ProSim737, PMDG and the real aircraft.  If any of the above commands do not function correctly, you will need to try and find a workaround; often this is quite easy, but does require a little lateral thought.  Hopefully, one day all major suites will be identical.

Variability

Many things in aviation can be done multiple ways.  The rules concerning the circle-to-land procedure are for the most part solid.  It would be foolish to descend below the MDA, navigate outside the 'protected area' or to continue landing when viability has obscured the runway. 

Wind, however, is one aspect that can alter the time used to fly the various legs; 30 seconds may be more prudent than 20 seconds, while an initial 40 degree turn may be more effective than a 45 degree turn.

Likewise, the boundary of the 'protected area' and the pilot's ability and confidence will determine the distance from the runway they fly.  One pilot will be confident flying a tight pattern with a continuous descending turn from downwind to final while another may want to extend the distance to enable more time to carry out the landing.  Variably is allowed provided you keep within the parameters discussed earlier.

Airline Operator Policy

In the real world, an operator will often publish their own approved limitations, including those for circling approaches. They are usually based on several factors, including the speed category of the aircraft and also a minimum height to fly at while carrying out any sort of visual approach (this is sometimes referred to as the Approach Ban).

The objective of the exercise is to fly the published procedure safely by remaining clear of cloud, in sight of the surface and keeping as close as possible to the landing runway.  This is best achieved by the pilots flying at a familiar height which is typical of a normal visual circuit.

Video and Discussion Paper

Useful Points:

  • Using the ILS during the initial approach is not recommended as the aircraft can easily descend below the MDA (unless you are vigilant).  Use the localiser and V/S.

  • If the ILS glideslope is used, enter into the altitude window the MDA + 500 feet.  Then, when the altitude horn sounds (750 feet ASL) change the descent mode to V/S with an appropriate descent rate.  This will ensure that the aircraft does not descent below the MDA.

  • As you descend to the MDA dial the offset heading into the heading window (rather than wait until you reach the MDA).  Then, when you reach the MDA and ALT HOLD is displayed on the MDA select the HDG selector.

  • When turning to the offset course, always use a 45 degree turn left or right for roughly 20 seconds (factor in wind).

  • Change the degree of bank selector to 20 degrees (if using the MCP to navigate the aircraft).

  • To aid in spacial awareness, set-up a suitable approach in the FMC so that navigational cues can be followed when turning to final (for example, an IAN Approach will display diamond markers on the PFD.  Using the Vertical Bearing Indicator (VBI) in CDU will display a rate of descent to the runway threshold).

  • When flying downwind, it can be advantageous to fly a little longer than the time calculated.  This enables more time to turn to final and stabilise the aircraft prior to reaching 1000 feet ASL.

  • Select gear down when adjacent to the runway (if not before).  Then, after flying the stipulated downwind time select landing flaps, set speed, and set a 300 feet descent rate using V/S.  Then begin the turn to final.

  • At 300 feet AGL the aircraft wings should be level and the aircraft aligned to the runway.

Final Call

The circle-to-land approach is not difficult, however, depending upon your flight simulator set-up, it can be challenging because you cannot look out of a physical window and see the airport.  By far the most important variables are speed management and a stabilised approach regime.

Review and Updates

Released 27 May 2022. 

Updated 01 June 2022.

Changing the Font Style and Colour in CDU

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OEM 737-800 font style (courtesy Mick.C ©).  An interesting point about this picture is the condition of the flightdeck which is far from the pristine appearance of many simulators

This article will discuss how to change the font style displayed in the Control Display Unit (CDU). Although the ProSim737 avionics suite comes with a default font style, many enthusiasts wish to change the font, colour and size to more closely mimic the font used in the OEM CDU, or so the information can be more easily read (not all of us are 20 years old…)

The font styles displayed in a simulator are linked to the fonts that have been installed in the computer’s operating system.  Any font style can be displayed in the CDU – as long as the font style has been included in the style library used by Windows.

important Parameters

There are two parameters which depict how a font style is displayed:  the actual font style itself and the CDU config file.  

  • The location of the font style library is C:\\Windows\fonts (Windows 10/11).  

Any of the fonts located in this library can be used to display parameters in the CDU.  Likewise, if you have a preferred font that is not in the library then it can easily be added to the library (copy/paste).

  • The location of the config file is the CDU folder of the ProSim737 avionics suite.  

To edit the config file, you must right click the file and select edit, otherwise the file will open in read only (HTML text).  Once the config file is opened, it will become apparent that all the settings related to the CDU: screen location, screen size, font style, display parameters, etc are recorded in the file.  

With a little experience, it is often easier to make setup changes to the CDU by opening and editing the config file, rather than opening the options box from the CDU display window.  If editing the config file directly, always make a back-up copy of the file prior to making and saving any changes.

ProSim737 options box.  The options box is opened by right clicking the CDU screen and selecting config

Selecting a Font Style and Colour

How to initially configure the CDU (line setting, screen position, frame settings, etc) is addressed in the ProSim737 manual (2012 edition) or in the wikipedia manual.

To alter the font style, open the options box by right clicking the CDU screen and selecting config; the options box is linked to the Windows style library discussed earlier.  To change a font style, scroll through the styles available.  Once a style has been selected, you can change the font size by either changing the size variable associated with the font, or by selecting +- in the ProSim options box.

Another way to change the font style is to open the config file and edit the line entry that relates to the small and large font sizes.  If this method is used, ensure you transcribe the font style and size accurately to avoid errors.

To alter the font’s colour, the config file must be opened.  Once opened search for the following two lines:

<smallFontColor>Lime</smallFontColor>

<largeFontColor>White</largeFontColor>

Type the required colour replacing the bolded section above.

ProSim737 CDU config file.  The lines that need to be altered to change the style and colour are in red.  With experience, other attributes can also be altered, however, always make a copy of the file prior to changing anything

OEM

OEM is an acronym for original equipment manufacturer.  It refers to the hardware and software used in the real aircraft.  In the Boeing aircraft the font colours displayed in the CDU can be readily changed. 

The font style is more or less standardised across the Boeing fleet, however, variations to the font style can be found, and in part depend upon the software option selected by the airline when the aircraft was initially purchased, the U version in use, and the manufacturer of the CDU (Smiths, Collins and Honeywell).

Colour Conventions

The FMC software supports 5 colour conventions: green, cyan, magenta, white and amber.   Bill Bulfer examines the text displayed for each colours in the FMC Guide. The information provided is from U10.2.

Final Call

Changing the font style, size and colour can be easily accomplished by editing the config file either directly from the CDU display or by opening the config file itself.  If a specific style is needed, then this can be added to the Windows style library.