As SLF I thought there were parallels in the following incident with 447 ie time taken to recognise the aircraft was stalled and the height lost.
AEROMEXICO DC-10-30, NOVEMBER 11, 1979
The flight recorder data for this incident showed a constant rate of climb with continually decreasing airspeed before buffet onset and sustained aircraft stall.
According to the crew, while climbing through 27,500 ft, they felt a vibration which, within seconds, increased in intensity. The crew suspected an abnormal vibration in engine No. 3 and elected to reduce its power and then to shut it down. The crew also stated that, upon reducing power on engine No. 3, the aircraft assumed a pitch down attitude, the AP became disengaged, and the aircraft rolled to the right and then to the left and started to lose altitude.
The Digital Flight Data Recorder (DFDR) revealed that, after the No. 3 engine power was reduced, the aircraft decelerated into speeds that were below the stall buffet speed and the design flight envelope. Shortly thereafter, the nose dropped and the aircraft entered into a stall while at 29,800 ft and an IAS of 226 kns.
The calculated stall speed for the flight a t the time of the occurrence was 222 kns. The calculated buffet onset speed was about 241 kns. The DFDR showed a constant rate of climb until the stall and loss of altitude occurred. It also showed that the airplane noseup elevator was held between 9° and 18.2° throughout most of the recovery maneuver until the elevator was gradually relaxed with recovery from the stall starting at about 24,500 ft.
The DFDR readout showed the recovery started at 23,900 ft. At that time, the airspeed increased to a value above the calculated stall speed. The vertical acceleration reached a maximum of 1.68 g's during the recovery process which ended at an altitude of 18,900 ft, and the crew regained full control of the aircraft about 18,000 ft. According to the crew, when aircraft control was lost, the first officer declared an emergency. During that period, the DFDR showed that the aircraft was responding in a normal manner to crew control inputs.
It was found that about 4 ft of each outboard elevator tip, including the corresponding counterweights and the aircrafts tail area lower access door were missing. Numerous cabin ceiling panels, light fixtures, and an oxygen mask had been dislodged; however, most of these had been reinstalled by the cabin crew.
21:40:56 to 21:41:16
Aircraft IAS decreased from 247 to 226 kns while in a steady climb profile from 29,510 to 29,834 ft.
Aircraft pitch attitude increased from 8° to 11° noseup. Roll attitude went from wings level to 14° right wing down.
The horizontal stabilizer was deflected from 4.2° to 6.0° noseup. The aircraft heading changed from 264° to 271° and the aircraft entered into a buffet onset speed and later into a prolonged stall.
21:41:16 to 21:41:26
IAS decreased from 226 to 208 and then to 197 kns as the aircraft descended through 29,600 f t while still in a stalled condition. Aircraft pitch attitude increased from 11.0° to 17.4° noseup. The spoilers were deployed and stayed deployed for 75 seconds. The left inboard elevator sensor indicated that the elevators started an excursion from l° up to 12° up and then to 10° up.
The horizontal stabilizer deflected from 6.0° to 6.6° noseup. Although the aircraft was in a stalled condition, the elevators were commanding noseup, and the horizontal stabilizer was trimming for the noseup command. The aircraft heading changed from 271° to 283° and then to 272.7° while the No. 2 engine N rpm decreased to about 90 percent and then began to fluctuate at 100+-5 percent which continued for about 45 seconds.
21:41:26 to 21:41:36
Aircraft IAS decreased to 178 kns as it descended through 28,900 ft in a stall. Aircraft pitch attitude decreased from 17.3° noseup to 14.8° noseup.
The lower rudder sensor indicated that the rudders were deflected from 1.4° right to 11° left, which was beyond the 5° authority of the yaw damper.
Vertical acceleration remained about .9-g loads. The elevators continued in an excursion from 10° up to 8° up and then to 19° up.
The horizontal stabilizer deflected from 6.69° noseup to 8.33° noseup.
The aircraft heading changed from 272' to 274' and then to 272'. The rate of descent was reduced from about 4,200 to about 600 ft per minute.
21:41:36 to 21:41:56
The aircraft IAS decreased from 178 to 175 kns and then increased to 217 kns as the aircraft continued to descend through 25,600 ft at about 10,156 ft per minute.
The aircraft pitch attitude decreased from 14.8 noseup to 10.9° nosedown and then to about 6.6° nosedown.
The roll attitude continued an excursion from 3° left wing low to 23.5° left wing low to 25° right wing low to 3° right wing low to 13° right wing low and then to 5° left wing low. The rudder deflected from 12° left to 3° left.
Vertical acceleration changed from .9 to 0.65 to 1.0 g.
The elevators oscillated from 17° up to 9° up and then to 16° up.
The horizontal stabilizer deflected from 8.33° noseup to 9.46° noseup and then to 6.48° noseup.
The aircraft heading changed from 272° to 264° and then to 278°
21:41:56 to 21:42:06
The aircraft IAS continued to increase from 217 to 248 kns as the vertical speed continued to increase to 15,000 ft per minute rate of descent at 23,300 ft. The aircraft vertical acceleration changed from 1.0 to 1.4 g.
o The elevators deflected from 13.7° up to 8.4° up as the stabilizer deflected from 6.48° noseup to 9.56° noseup. The heading changed from 278° to 276°.
21:42:06 to 21:42:16
The aircraft IAS increased to 267.5 kns as the vertical speed slowed to about 11,988 ft per minute while descending through 21,600 ft.
The aircraft pitch attitude started an excursion between 5.2° nosedown to 5.7° noseup. The roll attitude went from wings level to about 5.7° left wing down.
The vertical acceleration oscillated between 1.4 to 1.1 to 1.68 g (the highest g load experienced during the occurrence). The elevators changed from 8.4° noseup to near neutral as the horizontal stabilizer increased to 9.87° noseup. The aircraft heading remained nearly constant at about 276°.
21:42:16 to 21:44:08
The aircraft IAS decreased as recovery became evident through a decreasing rate of descent and coordinated maneuvers which started about 21,600 ft and ended in a level controlled flight about 18,900 ft. The sequence of events was appropriate for a stall recovery in contrast with the sequence of events preceding 21:42:16 during which it appeared that the aircraft control inputs were correcting in the wrong direction for a stall recovery.
The theoretical stall speed of the aircraft for its climb weight was determined to be 203 kn and the buffet onset speed according to the Aircraft Flight Manual was approximately 234 kn. According to the DFDR, the aircraft was operated below 234 kn for over 40 seconds while climbing between 26,000 ft and 32,000 ft. During half of this period, the airspeed was below 203 kn. That the aircraft pitch attitude decreased from over 14° noseup to over 10° nosedown while nearly full noseup elevator deflection was held clearly indicates that the aircraft was in a fully stalled condition. Although the crew failed to recognize the approach and entry to the stall, they did, after approximately 1 minute, recognize the aircraft's stalled condition and responded with proper control to recover. A full minute for stall recognition is excessive. However, the DC-10's stall warning system consists only of a stickshaker, the operation of which might be misinterpreted by an inattentive or distracted flightcrew, particularly when the aircraft is controlled by the autopilot rather than a pilot. Although the flightcrew on this incident was not attentive to the aircraft's condition, a more explicit stall warning device might have alerted them sooner to the aircraft's true condition during its approach to the stall. We note that some transport aircraft, in addition to a stickshaker, have both visual and aural stall warning devices. We believe that either of the latter would have more quickly resolved the flightcrew's stall recognition problem and might have prevented damage to the aircraft. Consequently, since stall problems can be encountered by a legitimately distracted flightcrew, we believe that the stall warning system in the DC-10 should be improved to include either a visual or aural warning device, or both.
The flighcrew misinterpreted the stall buffet or the stall warning stickshaker or a combination of both as a No. 3 engine vibration.
Stall recovery procedures were implemented approximately 1 minute after stall entry and a successful recovery was effected.
The total altitude loss from stall to complete recovery was approximately 11,000 ft. The aircraft did not exceed VmoIMmo and neither aerodynamic load limits or acceleration limits were exceeded.
The stall buffet which was encountered as the aircraft approached and entered the stall produced a dynamic load on the elevator balance weights which resulted in structural overload and failure of the outboard elevator tips.