To meet a certain vane angle accuracy requirement, I guess.

At FL410, ISA - 35C, for example.

Thanks for that HazelNuts39.
I didn't know that an A330 was capable of flying with an IAS <60 kts.

At less than 1 g, sure it can do that. Without stalling too.

The point is that the manufacturer of an AoA sensor can guarantee a certain accuracy only within a certain envelope. Outside that envelope any value derived from the sensor must be considered inaccurate and unreliable.

How long can you maintain FL 410 at less than 1 g?
Even though the speed sensor is in error?
Brilliant logic! Best not tell the crew they are stalled then.

You need a bit of hindsight to know that.
There were much more powerful indicators to tell the crew they were stalled. They were all ignored, just as the stall warning itself.

HazelnutsHold the horses!
At the moment we are discussing the inconsistency of the stall warning, right?
Due to an airspeed, which was inconsistent in itself?
And therefore rendered an available AOA indication as unreliable?
And therefore caused the aural stall alert system to tell the crew "end of stall"?

And you think, that is a logic system in itself and not worth improving?

Was it inconsistent?

When did I say that?

Quote:
First due to icing, later due to the high AoA


Quote:
I'm sorry if i misread your posts, but yes, you sound like you do.

Years ago I proposed that, if the AoA signal is lost while stall warning is active, the stall warning should continue until a valid AoA signal indicates that the AoA is less than the stall warning threshold.

However, one needs to be very careful avoid that the cure is worse than the disease. The whole issue is somewhat trivial compared to the need to avoid getting to an AoA of 42,5 degrees in the first place.

- to the best of my knowledge, 447 never 'lost' a valid AoA signal? - agreed. - no - the lack of stall warning when the Captain arrived in the cockpit was non-'trivial'.

The ADIRU determines the vane angle from the sensor 'resolver' values. Possibly it applies a calibration of vane angle vs body angle of attack for the flap/slat configuration. If the airspeed is less than 60 kt CAS, the ADIRU transmits the value NCD (No Computed Data) instead of the AoA value (as I understand it). The stall warning function resides in the FMEGC which uses the AoA values it receives from the ADIRU's.

The stall warning was lost after the captain arrived in the cockpit.

Probably. That sounds suitably over-complicated.

So it never 'lost' a valid AoA SIGNAL as far as we know.

Perhaps some PPRuNers tend to over-simplify?

If you insist on having the last word, I'll leave it at that.

HN, the logic and function of the stallwarning is understood. The question after AF447 is, wether this arrangement to use the speed signal as the only authority to verify the correctnes of an AOA over the total AOA regime is a clever one. I can understand that some input like speeds are necessary to compute the exact angle of attack. But what sense does that make in extreme AOA conditions, where high raw AOA data show the jet in the stalled condition anyway? Why not implement a logic, where an AOA value above the highest stall onset AOA bypasses the above logic and thus keeps the stall warning active? it cant be rocket science to do that.

To clarify my thoughts a simple example out of daily life. I'm wearing glasses like many people do. When i enter a moist room coming from the cold outside the glasses fog up. Instead of closing my eyes and being blind it has itself proved appropriate to remove the fogged up glasses and work with whatever eyesight is left.

I'm not a systems expert and have to leave the reply to your question to them. Considering what modifications are necessary to implement the BUSS, it sounds to me like a major redesign of the the whole system.

ventus45,

even simpler would be providing an AoA indicator that shows a flag when AoA=NCD.

How long after exactly ?

....*sigh*

AoA indicator.
 

AoA indicator was(is?) optional, what are the arguments to NOT opt for the AoA indicator?

@HN39:
Not to be picky but stall warning resides in FWC (Flight Warning Computer) not in FMGEC.

Because to the best of my knowledge nothing in the documentation ever implied that Alpha Prot, or even Alpha Max, were the equivalent of Critical AoA.

I'm not "spreading disinformation", and I challenge you to prove anything I've said recently to be wrong. I have not yet been able to source an English language version of the final report, and thus have to work from extracts.