Stalls
Lots of talk about stalls:
Any stall that is recovered with normal controls proves there was control in the STALL. Any STALL.
One cannot escape the fact that Autotrim, in this instance, would never be allowed in any aircraft, if it took away the standard dependence on both buffet, and Nose Drop
My proposal is that the THS prevented a STALL, allowing entry into what can best be described as a MUSH.... Whatever you call it, it bore no resemblance to a normal STALL. Further confusing the pilots....
A ballistic STALL is gentle, almost graceful, and there is no "Drastic increase in drag", and no compelling urgency for the Nose to drop. Buffet is likewise attenuated, and as in this case, less likely to cause alarm, or alert.
A 727-200, after leaving JFK was involved in a stall accident when the pitot tubes iced over. Responding inappropriately to the erroneous Air Data information, showing an increasing airspeed, altitude, and rate-of-climb, the co-pilot, who was flying the airplane, continued to raise the nose until the warning went off at FL230. The stick shaker then activated at 420 kts (as recorded on the FDR.) The F/O then misinterpreted the buffet as Mach buffet, as the airspeed was likewise erroneously increasing, and applied yet more back force to the controls. The stall warning continued as the F/O said “There’s that Mach buffet, guess we’ll have to pull it up,” followed by the Capt’s response “Pull it up.” Two seconds later, the aircraft began descending (in a stall) at 15,000 fpm. 43 seconds later, the crew transmitted a Mayday - we’re descending through 12. Five seconds later, the final CVR dialog was spoken by the co-pilot “Pull now....Pull; that’s it.”
So - was this a Deep Stall accident? The answer is decidedly
No, if you define a Deep Stall as an airplane attitude and flight condition from which the pilot is unable to recover using pitch and thrust. During flight tests, the airplane was stalled at AOAs of 25 degrees and recovered by relaxing the pull force on the control column. With the use of thrust during recovery, altitude lost was limited to about 2000 ft. Data shows that the AOA can be decreased and stall recovery effected by pushing on the column.
The answer is
Yes if you eliminate the “unable to recover” aspect of a “true” Deep Stall. This airplane entered a
pilot induced Deep Stall condition and remained in that condition
from inducement by the F/O until impact. The crew fixated on the Air Data indications and ignored their Attitude references, which, at 30 degrees nose up, showed an attitude about 25 degrees greater than normal. The co-pilot maintained, with the Capt’s concurrence, heavy back pressure from before entering the stall, through the entire 25,000 ft descent, until impact with the ground. The whole event took 83 seconds. They could have recovered, according to the NTSB report, for up to 40 seconds after entering the stall, by merely - as a minimum - relaxing back pressure on the control column.
Does this sound similar to AF447 except for the altitude and the absence of FBW electronics and sidesticks in the 727?
The F-104 had considerable gyroscopic effect from the single rotating engine. This, combined with the anhedral in the wings, caused a rather violent lateral oscillation in the deep-stall region which eventually resulted in a nose slice bringing the AOA down and allowing recovery.
Chuck Yeager's later flight in the NF-104A (1967 with the rocket) demonstrated the true deep stall characteristics of the F-104 configuration. On this zoom mission, where the engine was shut down at high altitude, the RPM had dropped to almost zero thus negating the lateral oscillation normally associated with an F-104 at high AOA. The airplane stabilized in a deep stall and stayed there all the way down. (Chuck ejected at 7,000 ft.)
I think
Gums pointed this out: The F-16 exhibits a deep stall characteristic, probably related to its aft cg (about 6% unstable subsonically) since it does not have a T-tail. Spin tests showed that it could be recovered from the deep stall by rocking the airplane fore and aft with the stick.
The latest in stall recovery: The current fighters (F-22, F-35) "enter and leave" the deep stall region routinely using engine thrust vectoring.