Originally Posted by JD-EE #928
...is there a distinct display for the pilots when the plane is actually stalled rather than facing an imminent stall? If not, wouldn't that be a worthwhile addition to the software?
JD-EE;
Couple of points for discussion:
The "stall" isn't as demarcated a break-point as it may seem. A wing, especially complex designs such as the A330 (and most other transports) does not stall "all at once", (this is by design), nor does it necessarily stay in a stall. In fact I don't think this stall could be defined as a "deep" stall in the way that Davies meant it in his book, but that's another rabbit trail.
The PFD [Primary Flight Display...horizon, speeds, altitudes, heading, vertical speeds, autopilot modes, etc] speed scale provides very clear information on those speed regimes approaching the stall, (photo of a PFD "at alpha-max", not yet in the stall, below) and, if the speed is available, provides sufficient information for crews to keep themselves out of that regime.
Many here have advocated an AoA indication be provided among the standard displays, probably on the PFD. I have flown aircraft with AoA (B727) and like the idea and believe a sufficiently detailed discussion about the desirability, technical viability, reliability and certification of such indications is needed. The problem is made quite complex by broader factors and priorities such as the industry's approach to training and standards in re the use-and-abuse of automation, flying and problem-solving skills, etc. The broader question always is, Do we design more fences and interventions? Just because we can, should we?
Some very respectable observers have said in response to the question, "yes, we design more automation". I am not in disagreement with that view.
But it is not easily, nor simply discussed and settled. What is meant by "more"; how is it to be designed, certified, implemented, trained?
Already, the industry is discussing automated responses to TCAS and EGPWS events and tail-strike automation is already a reality on long-body aircraft. Clearly, those two interventions alone are extremely complex but not at all impossible to do.
An automated response to the stall? Again, not impossible - the question absolutely requires much discussion between many interested parties. I'm sure that discussion has been underway in some venues already. For basic starters, one has to define "stall", and when the intervention takes over and when it hands control back to the pilot.
The interesting comment has been made about resisting automation may actually "cause" more automation. I think that's okay. There is no resistance to automation in any of the comments that I've made. I've always advocated training (and getting into the books) to achieve a solid comprehension of one's airplane. (The balance between adhering to SOPs, and diverting from SOPs through one's 'understanding' of the airplane is a perrennial problem...not easily solved...how much "initiative" does the industry give pilots, how much do they stay away from trying things?...big questions, very relevant today).
My strong and consistent resistance is to the idea that we, (and our managements, the regulator, the safety people), can relax because of automation. THAT, to me is the problem.
The problem is driven by money, politics, convenience (of hiring/training) and the industry's spectacularly high level of safety, (which I believe is being taken for granted by newbie managers who have no idea of history and how the industry's safety record was achieved).
To your question, I'm not an aeronautical engineer so cannot explain the two questions you're asking: 1) What are the actual dynamics of the stall in a large transport aircraft?, and 2) How, in practical terms, might "the stall" be displayed to the pilots in such a way as to provide unequivocal guidance, in very bad circumstances, (weather, system failures, etc) for manual pilot recovery.
Perhaps
HN39, or
gums, Graybeard, Machinbird, Chris Scott and others can discuss the questions -
HN39 and I had a great discussion about AoA on the second thread and I learned a LOT about the A330 and high-altitude stalls. Presenting the information swiftly, accurately and in a way that clearly shows trends either way, are fundamental requirements.
It has to be understood and accepted that the design and certification of such a system are monumental tasks, and that the questions are being asked within the context of other possible solutions to the problems outlined and discussed on this thread. Choices would need to be made as to which solution is best. Such decisions are by no means solely informed by the "flight safety" discourse and the moral question.