A320 FAC Gr dot v FMGC clean speed

[Bearcat]

Folks there is a limit out there in relation to the FAC gr dot speed v the FMGC clean speed provided the loadsheet is correct. I think the max diff is 7 knots before they have to look at the AoA sensors.

Can any of you aces enlighten me where this is referred to?

Thanks

[PantLoad]

Bearcat,


I'm not sure of your question. I'm going to take a guess at this and hope I understand.

If you look at Airbus FCOM 4.06.20 (Irregularities), you'll see under the "CHECK GW MESSAGE" the following:

"CHECK GW MESSAGE" appears on the MCDU when the gross weight computed by the FM and that computed by the FAC disagrees by more than seven tons (16055 LB). When this message appears:

- CALL UP the MCDU FUEL PRED page and CHECK the current GW (=main engine start up from the load sheet-fuel used) and correct if necessary.

- If the current GW on the MCDU is correct. (FM characteristics speed displayed on the MCDU are correct).
DISREGARD the computed FAC characteristics speed (Vls, F, S, Green
Dot) and refer to the given speeds in the QRH.
(FM characteristics speed on the MCDU are correct).

- If the load sheet seems to be the cause of the discrepancy
COMPARE FAC and QRH speeds, and select the most appropriate.


I think this is your question...That's where you got the number 'Seven' in your mind. It's seven tons, not seven knots.

But, are you asking about discrepancy between airspeed indicators?


Safe flying...

PantLoad

[Bearcat]

Thanks a mill pantcat for the effort re your reply.....I went through that scenario but what I am after is there is a max speed difference acceptable to engineering between gr dot on the speed tape and the mcdu clean speed before they have to change the AoA sensors that feed the FAC.
It aint in the fcom's , mmel and I came upon it before.....

[Mäx Reverse]

We had an an aircraft dispatched with ADR2 U/S according to the MEL.

During several sectors it was discovered that ALL characteristic speeds calculated by the FAC where way to low (by up to 20 knots!) because the AOA2-Signal was not used for compensation in this configuration and AOA3 seems to have been a bit 'off'.

While Engineering keeps on telling there wouldn't have been any implications, even in case of a GPWS-Recovery or any other a-floor-condition, afterwards there was a note added to the respective MEL-Chapter saying that 'characteristic speeds may be affected' and to make an entry in the log if differences of 8 knots or more are obeserved.

Regards, MAX reverse