Originally Posted by jcjeant
I dunno if the STS played a role in this crash
MAk knows and has confirmed it did induce nose down trim. How big and how long? Wait and see.
Originally Posted by ManAdaSystem
STS works AFTER TAKE OFF.
Originally Posted by Aluminium Shuffler
STS is, like mentioned, active only briefly after TO - it is not active at any other stage other than if the SMYD detects an approach to the stall, in which case the STS trims nose down at the same time as the Elevator Feel Shift Module adds pressure to increase control column loading, in combination behaving like an old fashioned stick pusher to make the effort on the column to pull the ac into a stall at least twice what is needed without the systems fighting the pilot
Not active; activated, or better to say: armed.
Originally Posted by Boeing
The speed trim system (STS) designed to improve flight characteristics during operations with a low gross weight, aft center of gravity and high thrust. It monitors inputs of stabilizer position, thrust lever position, airspeed and vertical speed and then trims the stabilizer using the autopilot stabilizer trim. It operates most frequently during takeoffs, climb and go-arounds. Conditions for speed trim operation are listed below:
• Flaps up or down (737-400/500)
• Airspeed 100-300 KIAS
• 10 seconds after takeoff
• 5 seconds following release of trim switches
• N1 above 60%
• Autopilot not engaged
• Sensing of trim requirement
NG has quite similar, though not quite the same conditions for operation, point being STS does operate whenever needed, not just at T/O.
Vertically they vere flying in alt hold at 1000 ft QFE, which makes it about 1400 QNH. While it was below 2800 ft MSA, highest obstacle around localizer is a bit shy of 700 QNH so they had a good chance of missing everything despite descending without being established on final. Whether they were aware of legal requirements, proper flying and navigation techniques, illusions in flight etc. boils down to pilot selection and training in Tatarstan. First info does indicate these were severely lacking in quality.
Originally Posted by Aluminium Shuffler
FDR reportedly suggests no malfunction.
Yes.