A320 FMA FD indication

[GIVMI55W]

Hi all,

I dont get the FD indication on the PFD. Normally it shows 1FD2. But there are plenty of possibilities: 2FD2, 2FD, FD1 and so on. Can you please explain?

Thx

[eckhard]

Hi GIVMI,

This is straight out of the FCOM:

X FD Y
White
X and Y give the FD engagement status on PFD1 and PFD2.
X and Y can be 1, 2, or –:
–: No FD is engaged on the corresponding PFD
1: FD 1 is engaged on the corresponding PFD
2: FD 2 is engaged on the corresponding PFD.
The normal status (FD 1 and 2 engaged) is 1 FD 2.

If an FMGC fails, you may see -FD2, or 1FD-, or even 1FD1 or 2FD2

[Skornogr4phy]

You may also see 1FD1 or 2FD2 if the other FMGC takes over from the failed one.

[hph304]

1FD2 means FD1 is supplying LHS PFD and FD2 is supplying RHS PFD.
1FD- means FD1 is supplying LHS and RHS FD is deselected
-FD2 means LHS FD is deselected and FD2 is supplying RHS PFD
1FD1 or 2FD2 means that one of the FMGC's has failed and that one is supplying both FD's.

[vilas]

hph304
FD3? Which airbus is that?

[CaptainMongo]

Originally Posted by vilas

hph304
FD3? Which airbus is that?

On three occasions I have had FMGC failures that were not recognized by the aircraft. 1FD2 displayed - CAPT ND aircraft right on top of the green line, FO ND aircraft diverging from green line. First ECAM on each occasion was CAB PR LDG ELEV FAULT.

(Recommended change submitted to fleet regarding windshear take off precautions, I will let you know the response)

[Check Airman]

Originally Posted by CaptainMongo

On three occasions I have had FMGC failures that were not recognized by the aircraft. 1FD2 displayed - CAPT ND aircraft right on top of the green line, FO ND aircraft diverging from green line. First ECAM on each occasion was CAB PR LDG ELEV FAULT.

(Recommended change submitted to fleet regarding windshear take off precautions, I will let you know the response)

Interesting. What did your tech department have to say about the fmc failure, and why the cabin pressure message was generated?

[eckhard]

Interesting. What did your tech department have to say about the fmc failure, and why the cabin pressure message was generated?

Because the FMGC tells the CPC the landing field elevation, so if the FMGC fails, the route is lost and the CPC doesn't know where you are going to land.

[Check Airman]

Originally Posted by eckhard

Because the FMGC tells the CPC the landing field elevation, so if the FMGC fails, the route is lost and the CPC doesn't know where you are going to land.

I thought about that, but the manual describes a cross link channel which allows CPC 1 and 2 to communicate. I assumed if data was lost from one side, the offside unit would be able to supply the date from the functioning FMC.

From CaptainMongo's description, it seems the FO's FMC retained the route information, and one of the FMC's had a degraded position.

CaptainMongo, what other indications did you get? I'm new to the bus, and I find this information quite interesting.

[vilas]

Double FMGC failure is peculiar I wish airbus had done a better job, in that ECAM doesn't directly tell you what has happened but makes you guess it by the symptoms. ECAM shows CABIN PRESS LDG ELEV FAULT which is understandable but doesn't tell you the cause and NDs show map not available. MCDUs give you a option of BACK UP NAV if installed otherwise I think go blank and off course FMA disappears and you loose all automation AP, FDs, ATHR.

[Uplinker]

eckhard's post explains it, but just to flesh it out a little more:

FD refers to Flight director, obviously.

The grouping of the letters and numbers show which flight director is engaged on which PFD. So the number on the left side of the 'FD' letters shows which flight director is displayed on the left PFD, and the number on the right side of the 'FD' letters show which flight director is displayed on the right PFD.

Normally one sees 1FD2, which means flight director one is displayed on the left PFD and flight director two is displayed on the right PFD.

If there are any FMGC failures, the status of the flight directors can be instantly seen:

2FD2 : Flight director number two is being displayed on both the left and right PFD's (i.e., both PFD's show the same flight director: there is no independant cross check.)

-FD2 : The left flight director is not selected, and flight director two is selected on the right PFD.

1FD- : Number one flight director is displayed on the left PFD, the right PFD has no flight director selected.

1FD1 : Flight director number one is displayed on both PFD's.


.

[hph304]

@vilas a very special Airbus. Should have been 2 obviously

[CaptainMongo]

Check Airman,

We have the following warning in our manual:

In some cases, one FMGC may fail but continue to send invalid guidance targets to the autoflight system. Both the autopilot and flight director may remain engaged, but are invalid. 1FD2 remains on the FMA display but the guidance is erroneous on the side of the failed FMGC. The following messages may display:

• MAP NOT AVAIL

• GPS PRIMARY LOST

• OFFSIDE FM CONTROL

• SET OFFSIDE RNG/MODE

Engage the autopilot on the operative side and disregard the information coming from the failed side. If FMGC 1 failed, do not use AP1 for approach.


On two of the failures, the first indication of a problem was the cabin pressure landing elevation fault ECAM. The second indication was the MCDU message "SET OFF SIDE RANGE". The third failure was indicated initially by a "SET OFFSIDE RANGE" message. On one event I noted my ND on the green line and the FO's diverging. All three displayed 1FD2. FiFi is a wonderful airplane, very smart and "most" of the time she will tell you when she is sick but she still needs constant attention.

[Check Airman]

Thanks.

Appreciate your insight.

[Capn Bloggs]

My head hurts!