Airbus FMGS data

[fredgrav]

Hello everyone !
was just trying to understand if parameters such FLT NUMBER, THS setting and CG inserted into the FMGS do have any utility ... I mean, does the FMGS actively process these kind of data ?

Thanks in advance,
fredgrav

[kijangnim]

Greetings,
We use to have a Takeoff and Landing Card on which data had to be written, and the card had to be in view during these flight phase, the Card is gone and replaced by the MCDU Takeoff and Approach phase....
The Flt number is processed, and used for other applications such as CPDLC Acars messages, THS, and C of G are for display.

[ALK A343]

Hi, this is from the FCTM regarding the C.G. entry. Basically your FM predictions and characteristic speeds will be in error if you enter a wrong zero fuel weight and to a lesser extent a wrong zero fuel weight C.G.. However in flight the FAC will calculate its own gross weight, C.G. and characteristic speeds based on aerodynamic data. Hope it helps.

The GW and CG computation is as follows:

1.The pilot enters the ZFW and ZFWCG in the MCDU INIT B page

2.The FMGC computes the GW and CG from:
• The ZFW, ZFWCG inserted in the MCDU INIT B page
• The fuel quantities from the Fuel Quantity Indicator (FQI)
• The Fuel Flow from the FADEC.

3.This current GW and/or CG is used for:
• FM predictions and speeds
• ECAM (GW only)
• MCDU (GW and CG)

4.The FAC computes its own GW and CG from aerodynamic data.

5.GW and CG FAC computed are used for:
• Minor adjustments on the flight control laws
• Characteristic speeds (VLS, F, S, Green dot) display on PFD.

Note:
1.On ground, FAC uses the GW FM computed.

2. In flight, at low altitude (below 15 000 ft), low speed (below 250 kt) and flight parameters stabilized, GW FAC computed comes from aerodynamic data. If these conditions are not met, GW FAC computed equates to the last memorized GW - fuel used.

3. If the GW FM computed and FAC computed differs from a given threshold, a ”CHECK GW” message appears on the MCDU scratchpad.

[fredgrav]

Thanx a million guys !!!
I know that a TOS (Take-off Securing Function) Pack1 (if implemented) processes INIT B/ PERF data to check for any disagreement between:

• Zero Fuel Weight (ZFW) range
• Take-Off speeds consistency
• Take-Off speeds limitations
• Pitch Trim/MCDU/CG

The check is performed as soon as the TO CONFIG pb is pressed, but it's just a check not a data computation/ elaboration.
At that point I was free to believe that, without an implementation of TOS, these data had no reason for being entered ...

[Dan Winterland]

The flight number is also used by Mode S.

[fredgrav]

The flight number is also used by Mode S.

Hi Dan Winterland,
if the FLT NUMBER is actually used for S mode, why do most pilots simply type the number as, for istance, 3011 and not AF3011 to identify the flight as being operated by Air France ?

[jaideep]

Good Question. But its a fact that the call sign in the mcdu is used for mode S. Don't know about france but we do use this in India.

[OPEN DES]

It is used for mode S. But really there is only one real airline in the world and that is AF! So no need for the airline-prefix.

They probably do it wrong. ATC doesnt't like it when you've mistyped the flight number. Unfortunately the only way to change the flightnumber inflight is to build a new plan from scratch in the secondary fpln.

[ALK A343]

Good one OPEN DES, I guess the gentlemen at AF can't be bothered to add the Airline prefix. In our company we put in the three letter ICAO airline code and the flightnumber as per the ATC flightplan. By the way on the A320s with FMS2 you can access INIT-A in flight and change the flightnumber if required.

[OPEN DES]

Hi there,

By the way on the A320s with FMS2 you can access INIT-A in flight and change the flightnumber if required.

Interesting on ours (FM2) you can't. Only way is to delete the sec fpln and start re-building, too time consuming.

Regards

[K.Whyjelly]

With regards entry of the the flight number this is what my Smiths /Thales 'New FM2+ Pilots Guide has to say on the matter;

Section II-Flight Phases Procedures

As per page 10 of the thales FMS 2 info booklet......................'this information is sent to various applications (as available) e.g ATSU, ACARS Flight Recorder; it must therefore be entered exactly as written in the ATC flight plan.'

[Denti]

Dunno if that is possible on the bus, but on boeings you can preprogram the airline identifier (three letter icao airline code) so all you need to enter is the rest of the callsign. Might be the case for the AF guys to save them one little step. But then it is allways possible to simply re-enter the callsign on boeings at anytime, in flight as well.

ATC usually complains very very fast indeed now if you enter the wrong callsign, in europe they partways use mode-S callsign allocation instead of squawk codes, even in france, so a correct callsign is a must.

[fredgrav]

One of the new features added to both FMGS (Thales, Honeywell) is the FMS Uplink/Auto Initialization, so the FLT number is automatically uplinked on completion after you press INIT REQUEST - LSK 2R !
Air France was just an example ...

[Dan Winterland]

"if the FLT NUMBER is actually used for S mode, why do most pilots simply type the number as, for istance, 3011 and not AF3011 to identify the flight as being operated by Air France ?"'

What you should input is the callsign which appears on the ICAO flightplan as that is what the ATC system is looking for. If pilots are abbreviating their callsign, they are doing it incorrectly.

[fredgrav]

Thanks Dan Winterland !