1. Primary control of the stabilizer is from 2 pitch trim switches on each control wheel.
- Each set of 2 switches makes arm and control signals: - The outboard switch makes the arm signal
- The inboard switch makes the control signal.
- Both switches must move in the same direction to move the stabilizer.
- Switch contacts have interface with the ACES in the FCE.
5. The switches are on the outboard grips of the captain and first officer control wheels.
1. Alternate pitch trim switches control stabilizer movement for either of these conditions:
- Failure of the interface between the flight control electronics (FCE) and the horizontal stabilizer trim actuator (HSTA )
- The HSTA fails to respond to an FCE command.
2. There are 2 alternate pitch trim switches - ARM and CONTROL. - Outboard switch - ARM
- Inboard switch - CONTROL.
3. Both switches must be moved in the same direction to make a command signal.
4. Alternate pitch trim switch signals go directly to the electric motor control units (EMCU) - not through the FCEs.
5. The alternate pitch trim switches are on the aisle stand adjacent to the parking brake lever.
Flight Crew Operations manual (FCOM)
Alternate pitch trim is controlled by the dual pitch trim switches on the control stand. Both switches must be moved to command trim changes. The switches are linked electrically to the horizontal stabilizer trim actuator and then mechanically to the stabilizer. Alternate pitch trim switches have priority over primary pitch trim commands in all flight modes. Alternate pitch trim switches are inhibited when the autopilot is engaged. Pitch trim does not move the control column.