A320 family - takeoff fuel flow FDR anomaly (to me)

[ex902]

Hi,

I am examining the flight data records of A319/320/321 and so often see that the fuel flow records of one engine maintain the exactly same FF value for a while: at takeoff and some initial parts of the climb and do not even change slightly (for instance during lift off FF1=2039 kg/h and exaclty same for a while and FF2 is something 3600 kg/h and it changes gradually). And is not this FF1 so low for takeoff moment? and what about the difference in FFs of both engines for the example above?

Could it be a FDR fault (but I have hundreds of the similiar cases) or something related to flat rate (which I didnot know flat rate can provide a reduction in fuel flow at this level). And are the V2500 engines and EEC's accurate that much? Or could it be something with the AP command on fuel flow control procedure?


I have not seen such cases in Boeing 737 or 738.

Thanks a lot in advance.

[Sidestick_n_Rudder]

What is the sampling rate of FF?

[FlightDetent]

Three points:

1) If such a dynamic parameter as FF stays aboslutely constant, I would be suspsicious.
2) Talk to your pilots to see what is the normal value on the FF (for me 3,6 sounds like a TOGA on a hot day for 27,5k engine)
3) FF on the engines should be equal +/- wear and tear. Absolutely not possible to have 1 t difference!!

My best guess is that you have problem with the FAP profile definition.

[Tinwacker]

Guess,
With a ton error at take-off that No.1 fuel flow transmitter is sticking and giving you the wrong comparison readings, while No.2 is fluid and variable.
Change that component and then get fresh readings.

Still a guess but an area I would certainly look at...

[ex902]

Dear all, thank you for the comments and for your time.

@Sidestick_n_Rudder: Excuse me but I could not understand what you mean with sampling rate of FF?
@FlightDetent:
1) Yes I agree 100%, I didnot expect to see absolutely same FF figures for this long time, but since there are many flights like that, I forced myself to think may be in Airbus, the EEC/ECU could have "extremely" precise command function on fuel control unit.
2) I do not have chance to communicate with the pilots, I just wanted to hear the opinions of pilots here.
3) Then I am absolutely sure that there is something wrong with FDR or data acqusition. I do not think that there might be anything wrong with the engine systems.

@Tinwacker: I am not sure that the problem is caused by the transmitter itself, because (as far as I know) this signal is also used for f.used calculation in DMCs, so if anything happens to the transmitter then a serious fault should be come into view. But the FDRs that I am examining belong to regular flights with no fault. Also, it is interesting to me that the trasmitter function only sticks same value at this specific flight phases, because after on it appears to work normally.

Regards

[Cough]

Ref answer 2,

I would suggest that you try and pass a message to one of the the operating pilots for that aircraft soon. During the takeoff roll the actual FF figures don't scan through a pilots head, merely that it looks sensible. I would suggest during the climb the FF would get scanned again but it may at that point be sensible.

So there may be a defect, it just may need a pointer to be recognised...

[FlightDetent]

Sampling rate: how many times per minut/second is the parameter recorded.

Does this "feature" manifest on single airframe, better put: on a single engine, or is it fleet wide? The answer may give you some leads...

As agreed before, if the number is constant, most likely you have a data processing problem. Even a faulty sensor would not give constant data without being noticed by / introducing huge problems to EEC.