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Mission Statement 

The purpose of FLAPS-2-APPROACH is two-fold:  To document the construction of a Boeing 737 flight simulator, and to act as a platform to share aviation-related articles pertaining to the Boeing 737; thereby, providing a source of inspiration and reference to like-minded individuals.

I am not a professional journalist.  Writing for a cross section of readers from differing cultures and languages with varying degrees of technical ability, can at times be challenging. I hope there are not too many spelling and grammatical mistakes.

 

Note:   I have NO affiliation with ANY manufacturer or reseller.  All reviews and content are 'frank and fearless' - I tell it as I see it.  Do not complain if you do not like what you read.

I use the words 'modules & panels' and 'CDU & FMC' interchangeably.  The definition of the acronym 'OEM' is Original Equipment Manufacturer (aka real aicraft part).

 

All funds are used to offset the cost of server and website hosting (Thank You...)

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Journal Archive (Newest First)

Entries in P3D V4 (2)

Monday
May282018

FMC Software and its Relationship with LNAV and VNAV

The procedure to takeoff in a Boeing 737 is a relatively straightforward process, however, the use of automation, in particular pitch and roll modes (Lateral and Vertical Navigation), when to engage it, and what to expect once it has been selected, can befuddle new flyers.  

In this article I will explain some of the differences between versions of software used in the Flight Management Computer (FMC) and how they relate to when you engage  LNAV and VNAV.  I will also discuss the autopilot and Auto Flight Direction System (AFDS) and explain the Flaps Retraction Schedule (FRS).

It’s assumed the reader has a relatively good understanding of the use of LNAV and VNAV, how to engage this functionality, and how they can be used together or independently of each other.

FMC Software Versions

There are a several versions of software used in the FMC; which version is installed is dependent upon the airline, and it’s not unusual for airframes to have different versions of software.

LEFT:  A mundane photograph of the CDU page displaying the U version of software used by the Flight Management Computer.  The page also displays the current NavData version installed in addition to other information (click to enlarge).

The nomenclature for the FMC software is a letter U followed by the version number.  The version of software dictates, amongst other things, the level of automation available.  For the most part, 737 Next Generation airframes will be installed with version U10.6, U10.7 or later.

Boeing released U1 in 1984 and the latest version, used in the 737 Max is U13.

Later versions of FMC software enable greater functionality and a higher level of automation – especially in relation to LNAV and VNAV.

Differences in Simulation Software

The FMC software used by the main avionics suites (Sim Avionics, Project Magenta, PMDG and ProSim-AR) should be identical in functionality if they simulate the same FMC U number.  

As at 2018, ProSim-AR uses U10.8A and Sim Avionics use a hybrid of U10.8, which is primarily U10.8 with some other features taken from U11 and U12.  Precision Manuals Development Group (PMDG) uses U10.8A.  

Therefore, as ProSim-AR and PMDG both use U10.8A, it’s fair to say that everything functional in PMDG should also be operational in ProSim737.  Unfortunately, as of writing, PMDG is the only software that replicates U10.8A with 97+-% success rate.

To check which version is being used by the FMC, press INIT REF/INDEX/IDENT in the CDU.  

Writing about the differences between FMC U version can become confusing.   Therefore, to minimise misunderstanding and increase readability, I have set out the information for VNAV and LNAV using the FMC U number.   

Roll Mode (LNAV)

U10.6 and earlier

(i)    LNAV will not engage below 400 AGL;

(ii)    LNAV cannot be armed prior to takeoff; and,

(iii)    LNAV should only be engaged  when climb is stabilised, but after passing through 400 feet AGL.

U10.7 and later

(i)    If LNAV is selected or armed prior to takeoff, LNAV guidance will become active at 50 feet AGL as long as the active leg in the FMC is within 3 NM and 5 degrees of the runway heading.  

(i)    If the departure procedure or route does not begin at the end of the runway, it’s recommended to use HDG SEL (when above 400 feet AGL) to intercept the desired track for LNAV capture;

(ii)    When an immediate turn after takeoff is necessary, the desired heading should be preset in the MCP prior to takeoff;  and,

(iii)    If the departure procedure is not part of the active flight plan, HDG SEL or VOR LOC should be used until the aircraft is within range of the flight plan track (see (i) above).

Important Point:

•    LNAV (U10.7 and later) can only be armed if the FMC has an active flight plan.

Pitch Mode (VNAV)

U10.7 and earlier

(i)    At Acceleration Height (AH), lower the aircraft’s nose to increase airspeed to flaps UP manoeuvre speed;

(ii)    At Thrust Reduction Altitude (800 - 1500 feet), select or verify that the climb thrust has been set (usually V2+15 or V2+20);

(iii)    Retract flaps as per the Flaps Retraction Schedule (FRS); and,

(iv)    Select VNAV or climb speed in the MCP speed window only after flaps and slats have been retracted.

Important Points:

•    VNAV cannot be armed prior to takeoff.

•    Remember that prior to selecting VNAV, flaps should be retracted, because VNAV does not provide overspeed protection for the leading edge devices when using U10.7 or earlier.

U10.8 and later 

(i)    VNAV can be engaged at anytime because VNAV in U10.8 provides overspeed protection for the leading edge devices;

(ii)    If VNAV is armed prior to takeoff, the Auto Flight Direction System (AFDS) remains in VNAV when the autopilot is engaged.  However, if another pitch mode is selected, the AFDS will remain in that mode;

(iii)    When VNAV is armed prior to takeoff, it will engage automatically at 400 feet.  With VNAV engaged, acceleration and climb out speed is computed by the FMC software and controlled by the AFDS; and,

(iv)    The Flaps should be retracted as per the flaps retraction schedule;

(v)    If VNAV is not armed prior to takeoff, at Acceleration Height set the command speed to the flaps UP manoeuvre speed; and,

(vi)    If VNAV is not armed prior to takeoff, at Acceleration Height set the command speed to the flaps UP manoeuvre speed.

Important Points:

•    VNAV can be armed prior to takeoff or at anytime.

•    At thrust reduction altitude, verify that climb thrust is set at the point selected on the takeoff reference page in the CDU.  If the thrust reference does not change automatically, climb thrust should be manually selected.

•    Although the VNAV profile and acceleration schedule is compatible with most planned departures, it’s prudent to cross check the EICAS display to ensure the display changes from takeoff (TO) to climb or reduced climb (R-CLB).  

Auto Flight Direction System (AFDS) – Operation During Takeoff and Climb

U10.7 and earlier

If the autopilot is engaged prior to the selection of VNAV:

(i)    The AFDS will revert to LVL CHG;

(ii)    The pitch mode displayed on the Flight Mode Annunciator (FMA) will change from TOGA to MCP SPD; and,

(iii)    If a pitch mode other than TOGA is selected after the autopilot is engaged, the AFDS will remain in that mode.

U10.8 and later

(i)    If VAV is armed for takeoff, the AFDS remains in VNAV when the autopilot is engaged; and,   

(ii)    If a pitch mode other than VNAV is selected, the AFDS will remain in that mode.

Preparing for Failure

LNAV and VNAV have their shortcomings, both in the real and simulated environments.

To help counteract any failure, it’s good airmanship to set the heading mode (HDG) on the MCP to indicate the bearing that the aircraft will be flying.  Doing this ensures that, should LNAV fail, the HDG button can be quickly engaged with minimal time delay; thereby, minimising any deviation from the aircraft’s course.

Autopilot Use, Flap Retraction and Eliminating Unwanted Pitch

When the aircraft is in manual flight (hand flying), the trim setting should be set correctly so that forward and back pressure on the control column is not required.  If the autopilot is engaged when the trim is not correct, the aircraft will suffer unwanted pitch movement as the automated system corrects the out of trim condition.

Adhering to the following recommendations will reduce the likelihood of unwanted or unexpected deviations from the desired flight path.

(i)    The autopilot should not be engaged before passing through 400 feet AGL;

(ii)    The flaps should not be retracted before passing through 400 feet AGL; and,

(iii)   The autopilot should not be engaged before flap retraction is complete, and then only engaged when the aircraft is in trim.  

If this procedure is adhered to, the transition from manual to automated flight will be barely discernible.  

Regarding point (iii).  I have used the word ‘should’ as this is generally a preferred option, however, airline policy may dictate otherwise.  

Flap Retraction Schedule (FRS)

The flaps on the Boeing 737 should be retracted per a defined schedule.  Failure to follow the FRS may cause excessive throttle use and possible flight path deviation.

LEFT:  Flap Retraction Schedule from FCOM (click to enlarge).  Copright FCOM.

Selection of the next flap position should be initiated when reaching the manoeuvre speed for the current flap position. 

Therefore, when the new flap position is selected, the airspeed will be below the manoeuvre speed for that flap position.  For this reason, when retracting the flaps to the next position, the airspeed of the aircraft should be increasing.

Said slightly differently, with airspeed increasing, subsequent flap retraction should be initiated when the airspeed reaches the manoeuvre speed for the current flap position.  

The manoeuvre speed for the current flap position is indicated by the green-coloured flap manoeuvre speed bug.  The bug is displayed on the speed tape of the Primary Flight Display (PFD) and is in increments that replicate the flap settings (UP, 1, 2, 5, etc).

Acceleration Height

Flap retraction commences when the aircraft reaches Acceleration Height, which is usually between 1000 and 1500 feet AGL (this is when the nose of the aircraft is lowered to gain airspeed).

However, often there are constraints that affect the height at which flap retraction commences.  Determining factors are: safety, obstacle clearance, airplane performance, and noise abatement requirements.  At some airports, airlines have a standard climb profile that should be followed for their area of operations

White Carrot

Located on the speed tape of the PFD is a white-coloured marker called a carrot (the carrot looks more like a sideways facing arrow).  The position of the carrot indicates V2+15.

LEFT:  Captain-side PFD showing white carrot.  Image from ProSim-AR 737 avionics suite (click to enlarge).

If you look at the Flap Retraction Schedule in the FCTM (see above image from FCOM), you will note the airspeed that is recommended to begin retracting flaps is V2+15 (the position of the carrot).  The white carrot is a very handy reference reminder.

Important Points:

•    The minimum altitude for flap retraction is 400 feet AGL.  

•    Selection of the next flap position should be initiated when reaching the manoeuvre speed for the current flap position.

•    Airspeed should be increasing when retracting the flaps.

•    The white carrot is a handy reference to V2+15.

•    Acceleration Height can differ between airports.

Summary

I realise that some readers, who only wish to learn the most recent software, will not be interested in much of the content of this article.  Notwithstanding this, I am sure many will have discovered something that may have been forgotten or overlooked.

The content of this short ‘function specific’ article came out of a discussion on a pilot’s forum.  If there is doubt, always consult the Flight Crew Training Manual (FCTM) which provides information specific to the software version used at that particular airline.

Glossary

AFDS – Autopilot Flight Director System
CDU – Computer Display Unit
EFIS – Electronic Flight Instrument System
FMA – Flight Mode Annunciator
FMC – Flight Management Computer
LVL CHG – Level Change
LNAV – Lateral Navigation
MCP – Mode Control Panel
ND – Navigation Display
PFD – Primary Flight Display
 VNAV – Vertical Navigation

Wednesday
Dec212016

RAAS Professional By FS2Crew - Review

Runway incursions are a leading cause of aviation fatalities and account for approximately $1 billion annually in aircraft damages. To help prevent such losses, close calls and collisions, the industry requested a safety system that would help maintain situational awareness during taxiing and preparing for takeoff and landing. 

Honeywell stepped in to fill the gap by developing an easy-to-install heads-up advisory system with aural alerts (call-outs) to increase flight crew situational awareness during ground and air operations relative to the runway. 

This system was then further improved upon, with the collaboration of Emirates.

LEFT:  KLAX airport diagram showing the maze that hundreds of aircraft each day must safely navigate.  Given the complexity of many airports, it's amazing there are not more runway incursions (click to enlarge).

I previously used a shareware version of RAAS developed by PlaneMan in South Korea.  This small FS add-on worked well, however, recently it stopped working on my system for an unknown reason.  I wrote a review on FsRAAS by Planeman in 2011.  Searching for a replacement, I came across RAAS Professional developed by FS2 Crew.  

What is RAAS

RAAS is an acronym for Runways Awareness And Advisory System (RAAS).  RAAS was developed by Honeywell Aerospace as a simple to install but effective software addition to the Honeywell Enhanced Ground Proximity Warning System (EGPWS).  Although the base-line RAAS is still in operation, Honeywell has improved the software by integrating additional aural advisory call-outs; in particular, relating to stabilised approaches.  SmartRunway and SmartLanding are the next generation of RAAS.

RAAS Professional replicates the complete aural Honeywell suite (RAAS, SmartRunway and SmartLanding), however, does not simulate the visual advisory displays.

Installation

Installation is via an installer and is straightforward.  The software installs a .ddl file which is loaded automatically when you begin a new simulation flight.  Once installed, a tab (RAAS Professional) will be added to the menu bar in flight simulator; this is where the user interface is opened to configure the program.  I did not experience any issues installing this program.

RAAS uses Simconnect to connect to flight simulator and does not require the use of FSUPIC.

Be aware that problems can occur when attempting to connect any add-on software that uses Simconnect (as opposed to FSUPIC).  If a problem occurs, the easiest way to rectify it is to re-install the Simconnect module of flight Simulator.

Simulator Platforms

RAAS will operate on FS9, FSX and P3D V3 simulation platforms in 32 Bit.  A 64 Bit version of the program caters towards those using P3D V4.

Initial Configuration (Managing the Runway Database)

The most important task to complete prior to configuring RAAS is to download a small standalone program called MakeRunways.  This software has been developed by Peter Dowson and is available gratis from his website.  The MakeRunways utility should be placed in your main flight simulator folder where the Scenery.cfg file is located.    

When run, MakeRunways interrogates the scenery folder and generates several database files that include, amongst other things, the runways found in flight simulator.  The generated files are automatically saved to your main flight simulator folder, for programs such as RAAS, to access and read. 

Whenever you install new scenery you must run the MakeRunways utility to ensure that the database is synchronized and up-to-date, otherwise RAAS will not work with the new add-on airport scenery.

Of importance, is that the 64 Bit version of RAAS requires an additional program to be installed.  The reason for this, is that vP3D V4 use a dedicated addons folder.  The Add-on organizer enables the add-on folder in P3D V4 to be interrogated by the MakeRunways program. 

The Lorby Prepar 3D Addon Organizer can be downloaded gratis at the developers website (see downloads section). 

The installation of these programs is very straightforward and instructions are provided in the supporting documentation.

Advanced Configuration

RAAS, like its real world counterpart, is highly configurable from the User Interface (UI) accessed from the Add-Ons menu bar in flight simulator.

The following aural call-outs (advisory) are available.

Approaching Runway (On Ground): advisory provides the flight crew with an awareness of when a runway is being approached.
Approaching Runway (In Air): advisory provides the flight crew with an awareness of which runway the aircraft is lined-up with during approach.
On Runway: advisory provides the flight crew with an awareness of which runway the aircraft is lined up with on the ground.
Runway End: advisory is used to improve crew awareness of the runway end during low visibility operations.
Taxiway Take-off: advisory alerts pilots to excessive taxi speeds or an inadvertent takeoff on a taxiway.
Insufficient Runway Length (On Ground): provides the crew of an awareness of which runway the aircraft is lined-up with and if the runway length available is less than the defined minimum takeoff length.
Extended Holding on Runway: alerts the crew of an extended holding period on the runway.
Approaching Short Runway (In Air): offers an advisory of which runway the aircraft is lined-up with and if the runway length available is sufficient as defined in the Runways section.
Taxiway Landing: alerts the crew if they are not lined up with a runway at low altitudes.
Takeoff Flap Monitor: alerts the crew if the aircraft's flaps are not in the defined takeoff range.
Landing Distance Remaining: provides the flight crew with an awareness of the runway length remaining during roll-out.
Distance Remaining (Rejected Takeoff): provides the flight crew with an awareness of the runway length remaining during a rejected takeoff.
Landing Flap Monitor: advisory alerts the crew if the landing flaps are not set.
Excessive Approach Speed: is an alert if the aircraft speed become excessive compared to the final approach speed.
Excessive Approach Angle: is an alert if the aircraft's approach angle becomes too steep.
Altimeter Setting (Above Transition): alerts the crew if the altimeter is not set to standard after climbing above the transition altitude.
Altimeter Setting (Below Transition): provides the flight crew with an awareness of improper corrected altitude setting while below the transition altitude.
Long Landing: alerts the flight crew if the aircraft has not touched down within the pre-defined Touchdown Zone Length.
Caution Enabled: adds the phrase ‘Caution’ to select aural calls.

Any of the aural call-outs can be turned on or off and several parameters are configurable from the UI.  Additionally, specific parameters can be changed depending upon aircraft type or airline policy, such as:

•    Aircraft type.
•    Runway takeoff and landing length, runway length and touchdown zone.
•    Hold times (initial hold time and repeats).
•    Flaps configuration (takeoff, landing, upper and lower altitudes).
•    Approach speeds.
•    Transition altitudes.
•    Extended hold times and frequency of the aural call-out.

If you fly different aircraft, any number of user profiles can be created.  The profiles are associated with the aircraft type selected in flight simulator.

Comparison - RAAS Professional to the  Honeywell System

RAAS Professional by Fs2Crew replicates the real Honeywell system surprisingly well.  The aural call-outs are identical and the female voice sounds very similar to the voice used by Honeywell - which provide either a female or male voice.  If you’re keen to compare RAAS to the Honeywell system I recommend you visit the Honeywell website and watch the three (3) videos at the bottom of the web page.

LEFT:  RAAS Professional User Interface (UI).  Click to enlarge.

Turning RAAS On and Off (RAAS Master Switch)

RAAS can be turned on and off ‘on the fly’ from the User Interface (UI), or by assigned a hot-key (key event API) in flight simulator.  By default the on/off function has been assigned to the water rudder (R) function (from within the flight simulator control panel).  It is also possible to assign this functionality to a switch/toggle.

Sound Cards and System Test

RAAS has been designed to be used within multiple speaker environments, and changing the speaker preference is made directly in the User Interface (UI).  With a little tinkering you should be able to dedicate the RAAS aural call-outs to a separate speaker while maintaining engine noise and Air Traffic Control to other speakers and a headset.  A master volume control tab enables the sound levels to be adjusted (if the speaker does not have volume control knob).

The UI has a System Test to determine correct configuration and connection (audio test) and an error log.  The error log can be used during troubleshooting (if necessary).  

Voice Sets and Memory Use

Currently RAAS only supports English in a female voice.  I believe that additional foreign language voice sets may be released in due course.

When RAAS is running, there is no discernable effect on the computer or flight simulator.

Support

A detailed and easy to read manual is supplied with the program.  The manual, in addition to providing detailed installation instructions, also has a very good troubleshooting section in the unlikely event that you have problems during the installation process.

RAAS supports a dedicated support forum and the developer replies to questions when asked.  

Program Shortfalls

At the moment it is not possible to install RAAS on a client computer and run the program across a network.  Although RAAS does not use a lot of computer resources, some users may wish to display the UI (when required) on a client screen in association with the Instructor Station.

Another shortfall is the inconsistent operation of the key event API (that enables you to connect a switch/toggle to the on/off function / RAAS Master Switch).  Sometimes it works and at other times it does not work correctly.

Final Call

If you seek realism, RAAS is a worthwhile addition to flight simulator.   When configured to an appropriate aircraft, the aural call-outs are timely and helpful to situational awareness.  Two features I particularly like are the ability of RAAS to remind you to set the appropriate flaps detente prior to takeoff, and the aural call-out that is generated which identifies the runway you are aligned with during final approach.

I must admit there was one occurrence when I was conducting a VOR approach to a parallel runway in limited visibility.  The aural call-out stated I was aligned to runway 24 Left when I was supposed to landing on runway 24 Right!  But isn’t this the reason RAAS was designed – to stop incursions and provide situation awareness to flight crews.

References and Affiliation

This article was written with reference material obtained from Honeywell Aerospace.  

Please note I have no affiliation with FS2Crew.  I have not been provided with ‘free’ software, nor did I receive a discount in return for a favourable review.  The comments and recommendations I have made are my own.  Further information on RAAS Professional can be obtained directly from the FS2Crew website.

Flight Simulator, in this article, refers to FSX/FS10.  I use the B737 avionics suite developed by ProSim-AR.

Another article relating to a free version of RAAS can be read here -  Runway Awareness and Advisory - FS Add-On.

BELOW:  Honeywell promotional video (courtesy & with permission Honeywell).

BELOW:  RAAS Professional promotional video (courtesy FS2Crew).