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Old 7th Nov 2018, 07:34
  #706 (permalink)  
Join Date: Mar 2001
Location: I wouldn't know.
Posts: 4,293
Originally Posted by Derfred View Post
Thatís interesting, Iím pretty sure the NG does no such thing. Can anyone post how this works on the Max?
Actually, the NG does:

The EFS module increases hydraulic system A pressure to the elevator feel and
centering unit during a stall. This increases forward control column force to
approximately four times normal feel pressure. The EFS module is armed
whenever an inhibit condition is not present. Inhibit conditions are: on the ground,
radio altitude less than 100 feet and autopilot engaged. However, if EFS is active
when descending through 100 feet RA, it remains active until AOA is reduced
below approximately stickshaker threshold. There are no flight deck indications
that the system is properly armed or activated.
As airspeed decreases towards stall speed, the speed trim system trims the
stabilizer nose down and enables trim above stickshaker AOA. With this trim
schedule the pilot must pull more aft column to stall the airplane. With the column
aft, the amount of column force increase with the onset of EFS module is more
That is from a by now pretty old NG FCOM, i haven't been typed for the last three years on the 737.

That said, we had a few AoA malfunction on our 737 fleet, thank god the only serious thing that happened was a runway overrun without injuries due to different speed indications during take off (abort close to indicated V1, but probably way above V1). In flight the problems caused by the AoA were actually quite severe, indications for IAS, Altitude, VS, flight path vector, wind indication and ground speed all became unreliable on the affected side. Comparator warnings were not always generated, so it was usually detected by pilots saying "this doesn't look right" and then comparing indications across the flight deck. Most problems happened in mid to high altitudes though, so there was plenty of space to recover. And it might or might not have any relevance to the current case.
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