Hi safetypee,
Thanks for your thoughtful responses and criticisms. Having been accustomed to them on five jet transports until I flew the A320, I agree that some form of stick-shaker should be considered. Just a few points to clarify.
Quote:
"Chris your argument for a dedicated AoA display makes several assumptions.
First that attitude is proportional to the indicated AoA..."
Presumably you are referring to the amount of pitch-down required for initial recovery? In fact I was careful not to suggest that if the AoA indicator showed the AoA was x degrees above the stall the pilot would simply need to reduce the pitch-attitude by the same amount. This is what I wrote:
"The degree of exceedance of stall AoA could be approximated in a clear graphic on the indicator, giving the pilot a good cue as to what kind of pitch-down may be required to start the recovery."
Clearly I'm not prescribing a technique for stall recovery. But I am suggesting that an AoA indicator would provide: (a) information on the degree of stall, particularly important if the initial warning has been delayed by UAS; and (b) a tool to be used during the recovery to help the pilot avoid a second stall during the pull-up.
On your second point: yes, I am assuming that the pilot "will 'see' the indicator, comprehend its meaning, and act accordingly." In any case, if the pilot isn't looking at the PFD, (s)he has little chance of effecting a recovery... The appearance there of a large AoA indicator, maybe accompanied by a flashing "STALL" caption, should grab the attention. The design would be as simple as possible consistent with showing clearly the degree of exceedance.
The problem with using the existing minimum-speed marker-bugs on the ASI (such as Alpha Max or Vsw) is the enormous variation of Vs with normal G. Any bug allowing for that would go down and up like a yo-yo during the recovery. And with UAS, IAS is not a usable tool.
Perhaps one of our ex-military guys will comment on the practicalities of using an AoA gauge for stall recovery.
Quote:
"Much of what has been discussed and done for safety improvement focuses on a single event which rarely applies across the industry or for future 'unforeseeable' events; we tend to fix the last problem and overlook generic items because it is difficult to agree on the judgement of their projected effectiveness."
That's generally true, but this being an AF447 thread we are bound to consider the combination of a UAS followed by a stall - in which the first stall warning may be inhibited while the stall develops steadily.