Re: Hva er disse i cockpiten på 737-8JP ?
STS prøver å trimme for å gi speed stability, altså at den prøver å hjelpe pilotene å holde hastigheten ved å trimme slik at man må bruke en forholdsvis stor kraft for å heve eller senke nesen. Den fungerer ikke bare ved takeoff, men under alle faser av flygingen under M0.5. STS trimmer ofte motsatt vei av det som er naturlig for pilotene, fordi piloter prøver å trimme vekk stick forces, mens STS prøver å gjøre det tungt å hale nesen opp for å hindre at man trekker for mye slik at farten synker.
FCOM 9.20.9:
Speed Trim System
The speed trim system (STS) is a speed stability augmentation system designed to improve flight characteristics during operations with a low gross weight, aft center of gravity and high thrust when the autopilot is not engaged. The purpose of the STS is to return the airplane to a trimmed speed by commanding the stabilizer in a direction opposite the speed change. The STS monitors inputs of stabilizer position, thrust lever position, airspeed and vertical speed and then trims the stabilizer using the autopilot stabilizer trim. As the airplane speed increases or decreases from the trimmed speed, the stabilizer is commanded in the direction to return the airplane to the trimmed speed. This increases control column forces to force the airplane to return to the trimmed speed. As the airplane returns to the trimmed speed, the STS commanded stabilizer movement is removed.
STS operates most frequently during takeoffs, climb and go-arounds.
Conditions
for speed trim operation are listed below:
• Airspeed between 100 KIAS and Mach 0.5
• 10 seconds after takeoff
• 5 seconds following release of trim switches
• Autopilot not engaged
• Sensing of trim requirement
