Originally Posted by
Homebrew1
The 737 does a trim after liftoff. This is what I'm asking about. You don't have to be a dick about it. I was just asking a question re the new Gen 737's as the function of this trim may have or may not have been an issue. I haven't flown a 737 for 6 years.
Homebrew1 you are correct and the system you are describing is the STS (Speed Trim System) that is a speed stability augmentation system installed on 737MAX airplanes. It operates automatically and during operations of low gross weight, an aft CoG, high thrust and autopilot not engaged. It is common for STS to operate during takeoff, climb and go-arounds.
From the FCOM the conditions for STS to operate is:
- Autopilot disengaged
- 10 seconds after takeoff
- between 100kts and M0.68
- 5 seconds after a manual trim
- STS senses a trim requirement
The purpose of STS is to return the airplane to a trimmed speed by commanding the stabiliser in a direction opposite to the speed change.