This stall debate is beside the point. On final approach on a 3 degree glide, those airplanes need variing amounts of power to keep the GS fully configured. What has happened in various accidents was that after a plane came in fast, the throttles would move or be moved to idle or slightly above during the phase where speed needs to bleed off. The dangerous part of that is that at some stage once speed and GS are achieved, the throttles will have to come back up to add power. Normally in this kind of Ops this is done via the Autothrottles. Now if they fall out for some reason, i.e. become not active, it has happened several times that airplanes lost speed, increased ROD. When the AP or the crew then try to get it back on glide, they add elevator and obvioulsy power should be added too. However, if one or both throttles do not advance, either due to the fact that the AT has been inadvertedly de-activated (as in the case of the TK plane in AMS and the Asiana 777 at SFO,) the speed decay continues while the AP will eventually bring up the nose in order to keep on the glide. If this is not addressed, it can lead to a critical loss of speed and therefore a stall. Also rate of descent would increase, quite possibly causing the airplane to hit the ground even without a stall.
In this case however, we also have seen on the video that the plane had a massive roll movement adding large amounts of bank. This could indicate i.e. that one engine did not spool up when commanded to do so or in a go around, which given the locations of the engines, would add a massive Yaw and Roll movement. It is only one of many possible scenarios, but one which would correspond to some of the figure we already know. Particularly in a go around, if one engine would not spool up for whatever reason, this can have massive effects.
Now we know they were not in radio contact and quite possibly this promted them to go around. If they then did not get the thrust they expected or worse an assymetric thrust, an outcome where the plane rolls and hits the ground is quite plausible.
I realise my question was probably off topic. I sort of prefer to use the word “attitude” when referring to stalls rather than “angle of attack” as a stall in a turn and a stall straight and level will be very different. But outside of aerobatics most PPL training AFAIK is that recovery from approach to a stall or a full stall, either with or without power, is to either release back pressure on the stick or yoke or push to a positive nose down attitude (of course if turning put wings level as well). Is all our stall training wrong? Or perhaps there is different training when flying a swept wing aircraft?
A_A I have flown,trained in, and owned T Tail aircraft and have found very little difference in stall characteristics with non T Tail. IMO the difference is a bit of a myth.
Or perhaps there is different training when flying a swept wing aircraft?
The primary thing which is different is that this kind of airpane have stick shakers and pushers, so a very different kind of stall warning. The training is done accordingly. You don’t stall those planes but you start recovery the moment you get a stick shaker. If you donˆt, the stick pusher will take action.
Hence, the reason for that wing drop seen in the videos is very likely not to be attributed to a simple stall but there must have been something else to cause this. On the other hand, the nose down movement seen on the other video might well be the consequent of a stick pusher action.
gallois wrote:
A_A I have flown,trained in, and owned T Tail aircraft and have found very little difference in stall characteristics with non T Tail. IMO the difference is a bit of a myth.
I did not write, or imply, that every T-tail aircraft would be thus affected, or even that it would be common.
But it is not something I’ve imagined. See https://skybrary.aero/articles/deep-stall
Correct, FLC HOLD mode for instance will not provide autothrottle wake-up protection.
gallois wrote:
Or perhaps there is different training when flying a swept wing aircraft?
Gulfstream G650, wing sweep of 33,28deg (“a bit” more than most other commercial jets). Taken from the OEM Operating Manual:
02-03-10: Approach to Stall
At first indication of impending stall or stick shaker:
(a) Disconnect autopilot and autothrottle.
(b) Apply nose down pitch control to reduce AOA.
(c) Apply power.
(d) Roll wings level.
(e) Retract speed brakes.
(f) Return to desired airspeed and altitude.
Looks about the same as the DA42 and without autopilot the same as most PPL training here Nose down to reduce A of A etc. In ULs you tend not to add power until with nose down you reach Vr or even Vy and add the power in the rotation to climbing back up. It all happens quickly in a UL as soon as the nose goes down.
But also you tend to roll level before adding power. That would appear to be the biggest difference AFAICT.
gallois wrote:
I sort of prefer to use the word “attitude” when referring to stalls rather than “angle of attack” as a stall in a turn and a stall straight and level will be very different.
You can use any word you prefer but it’s still AoA rather than attitude.
…T Tail aircraft and have found very little difference in stall characteristics with non T Tail. IMO the difference is a bit of a myth.
No, it’s not, T-tail aircrafts, especially with jet engines, are more prone to getting to deep stall which often can be unrecoverable.
I wasn’t writing about jet engines with T Tails. And you can call it what you want I explained why I prefer to use attitude especially as in a 60° banked turn you don’t need a high A of A to stall probably about 50% of what is required when straight and level. It is also unlikely to stall an aircraft with a negative A of A. What do you mean by a deep stall? Surely when an aircraft stalls it stalls and the word " deep " is superfluous.
I can only speak from my experience that I have noticed very little difference in the stall characteristics of a T Tail eg PA44 and DA42 or DA40 to any other empennage eg the Seneca or Aztec.
YMMV
gallois wrote:
What do you mean by a deep stall?
https://en.wikipedia.org/wiki/Stall_(fluid_dynamics)#Deep_stall
T-tail propeller aircraft are generally resistant to deep stalls, because the prop wash increases airflow over the wing root
