I note Owen Glyndwr's Cm - alpha curves, which suggest that return to normal flight should have been possible. but is it enough just to correct the pitching moment? Don't you have to pitch down to within a few degrees of the actual flight path angle, which in this case, once the full stall (I also don't like calling it a deep stall because that's different) is developed, would mean pushing the nose down about 45 deg? I can't see them having the insight to do that
I agree you have to pitch down enough that the aircraft accelerates. The curves of course only relate to AoA and aircraft trim, but in practice, until the dynamics have sorted themselves out and a new flight path angle stabilised, AoA and pitch move together. I think that when you have pitch down from some steady (stalled) state, the first thing that happens is that the flight path angle becomes more negative at more or less constant AoA, and the aircraft starts to accelerate. This would be a steadily escalating effect I think, so it would not be necessary to pitch all the way down to 45 deg nose down in the first instance. But then I am not a pilot, so perhaps someone else could comment?
Hi Owain,
Very interesting post, but what about engine thrust maintaining high pitch up with barely no airspeed?
The AIAA curves were just tunnel data, so no thrust effects were included. There certainly would be an effect such as you describe, which would depend on altitude as well as airspeed. (Thrust increases with decreasing altitude and decreasing airspeed; the overall aerodynamic moments other than thrust decrease also with airspeed, so the pitch effect from the engines is biggest at SL and low airspeed.
I don't think I agree with the "barely no airspeed" bit. To me it seems that the credibility of the
measured CAS is going steadily south as AoA increases and above about 35 deg AoA you cannot believe a number of it. I say this because it seems to me that the position errors are wholly unknown for any AoA above the flight tested stalling value and that when you are looking at AoAs of 30 deg or more coupled with roll and sideslip excursions the 'measurements' are completely unreliable. Where the measured CAS can be relied upon the recorded ground speed converted from TAS to CAS is in pretty good agreement with the measured value (and yes, I am aware of wind effects, but the AI analysis needed only a 15 kt wind correction and this, I assume, would have been 15 kt TAS, so much less as a CAS). If you carry that process forward to the regions where the recorded CAS is crazy you find that the aircraft was fairly close to 110 kts CAS all the way down.
A back-of-an-envelope sum for 110 kts and FL350 suggests that going from Flight Idle (essentially zero thrust) to TO power would add 8 degrees to the AoA. In the only sequence where power was reduced to idle the pitch changed from +15 to -10 but unfortunately one cannot say what effect that had on AoA because the AoA recording has hit the stops, as has the flight path angle recording. If you were
VERY imaginative and believed the AoA out of the IRS, you might persuade yourself that the AoA was reduced from about 46 deg down to about 39 deg
