AF 447 Thread no. 4

[Chris Scott]

Quote from HazelNuts39 (Jun15/1433z):
So I asked myself: how does one recover from a stall without reliable airspeed and without AoA? I would think that the proper action would be a determined nose-down push, maintained until the stall warning stops, and then trying to maintain an AoA on the edge of s/w, gently allowing the nose to raise until s/w occurs, then a small nose-down correction to silence it, etc., until back in approximately level flight at a reasonable pitch attitude.
EDIT:: Can anyone be expected to do that succesfully without being trained for that eventuality?

Quote from PA_18_151 (Jun16/0733z):
Scary stuff,. You don't use the stall warning to calibrate your response, you use your remaining instruments and your knowledge of your aircrafts pitch/power settings. Your solution puts you at an unnacceptable risk of secondary stall and that is another opportunity to enter a spin. If you do not know your aircraft's pitch/power settings for level flight then you are not competent to pilot it/manage its autopilot and take over if/when that autopilot fails.

Think you are missing HN39's point.

This aeroplane should not have stalled. It should not have zoom-climbed 3000ft, trading kinetic energy for potential energy ("speed for height"). But, for whatever reason, it did. Your advice – like that buried in a badly-written QRH procedure, and discussed on these threads for over two years – is spot-on prior to the climb from FL350, and might even have sufficed passing FL375 (AoA +4). Very soon after that, however, the wing stalled, and the AoA started rising rapidly. From then, the PF (perhaps unknowingly, although he did select TOGA thrust) was faced with a very different problem, which is the one that HN39 is addressing. (By the way, TOGA is little more than CLB thrust at high altitude.)

So the aeroplane is already in the stall (becoming a deep one). FPA display has been lost, and with it any chance of obtaining a rough idea of AoA. The VSI is soon off-scale (down), and it's night IMC. I assume you agree with HN39 that "the proper action would be a determined nose-down push", but that this should be sustained until well after the stall warning stops. Yes, there's a great risk of a secondary stall during the flare. But, with no reliable source of IAS, do you risk over-speeding the aircraft or and/or hitting the sea? If you end up very fast, how much height would be lost from an FPA of, say, -30deg**, at the 2.5G limit? With the altimeter racing downwards in a way you've never experienced except during a simulator "reset", at what point do you start pulling?

** (assuming stall recovery was started at, or soon after, the apogee)