B737 Autopilot and Autothrottle Indicators

Autopilot (A/P) Disengage Light

Illuminated (red) –
- flashes and tone sounds when autopilot has disengaged
- flashes and tone sounds when an autopilot engage attempt is made and is unsuccessful
- reset by pushing either disengage light or either A/P disengage switch
- steady for any of following conditions:
  - stabilizer out of trim below 800 feet RA on dual channel approach
  - ALT ACQ mode inhibited during A/P go–around if stabilizer not trimmed for single A/P operation
  - disengage light test switch held in position 2
  - automatic ground system tests fail.
Illuminated (amber) –
- steady – disengage light test switch held in position 1
- flashing – A/P automatically reverts to CWS pitch or roll while in CMD. Resets by pushing either light or selecting another mode

Illuminated (red) –
- flashing – autothrottle has disengaged
- steady – disengage light test switch held in position 2.
Illuminated (amber) –
steady – disengage light test switch held in position 1
flashing – indicates A/T airspeed error under following conditions:
- inflight
- flaps not up
- airspeed differs from commanded value by +10 or -5 knots and is not approaching commanded value.

TEST 1 – illuminates autopilot/autothrottle disengage and FMC alert lights steady amber.
TEST 2 – illuminates autopilot/autothrottle disengage lights steady red and FMC alert light steady amber.
Spring–loaded to center position.

Illuminated (amber) –
In-flight
- autopilot is not properly trimming the stabilizer
- partial failure of a Flight Control Computer
- illuminates only with autopilot engaged. Remains extinguished when the autopilot is not engaged.
On the ground
- partial failure of a Flight Control Computer
- illuminates after landing when groundspeed is less than 30 knots.