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The B737 has an interesting stabilizer trim system, which operates at four different speeds.
Main Electric Trim
Flaps Up: .2 units per second
Flaps Down: .4 units per second
Autopilot Trim
Flaps Up: .09 units per second
Flaps Down: .27 units per second
On the -300 and later models, there is a system called Speed Trim, which provides trim inputs during low speed operations with low gross weight, and aft center of gravity. It is most frequently observed during takeoffs and go-arounds. Conditions for the system to operate are:
Airspeed 100-300 KIAS
10 seconds after liftoff
5 seconds following release of trim switches
N1 above 60%
Autopilot not on
Sensing of trim requirement
By Captain George Nolly4.6
136136 ratings
The B737 has an interesting stabilizer trim system, which operates at four different speeds.
Main Electric Trim
Flaps Up: .2 units per second
Flaps Down: .4 units per second
Autopilot Trim
Flaps Up: .09 units per second
Flaps Down: .27 units per second
On the -300 and later models, there is a system called Speed Trim, which provides trim inputs during low speed operations with low gross weight, and aft center of gravity. It is most frequently observed during takeoffs and go-arounds. Conditions for the system to operate are:
Airspeed 100-300 KIAS
10 seconds after liftoff
5 seconds following release of trim switches
N1 above 60%
Autopilot not on
Sensing of trim requirement

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