Factual Information 2015:Appendix 1.6E/1.6E.3
This page contains an extract from MH370/01/15 Factual Information which accompanied the (first) Interim Statement released by The Malaysian ICAO Annex 13 Safety Investigation Team for MH370 on 8th March 2015.
1.6E.3 Autothrottle (Thrust Management Computing Function – TMCF)
The autothrottle (A/T) commands the thrust levers to achieve an engine thrust setting, or a selected airspeed. The A/T is armed by the operation of two toggle switches and engaged by the operation of a pushbutton switch on the MCP (Figure 1.6DE below).
During normal flight operations, the flight crew uses the TMCF to perform several routine or normal operations and tasks. These operations or tasks relate to autothrottle modes. The autothrottle (A/T) modes operate in these flight phases:
- Take-off (TO)
- Climb (CLB)
- Cruise (CRZ)
- Descent (DES)
- Approach (APP)
- Go-around (GA)
Autothrottle functions that relate to flight phases are flare retard during autoland and autothrottle disconnect. Autothrottle thrust mode annunciations relate to pitch mode annunciations on the Primary Flight Display (PFD).
1.6E.3.1 Autothrottle Modes
- a) Take-off (TO)
- In TO, the autothrottle controls thrust to the take-off thrust limit. The autothrottle mode annunciation on the PFD is thrust reference (THR REF). At a threshold air speed, the autothrottle mode annunciation on the PFD changes to HOLD.
- b) Climb (CLB)
i. These are the three autothrottle mode selections in climb:
ii. These are the autothrottle mode annunciations for these modes:
- THR REF when VNAV engages
- THR when FLCH engages
- SPD or THR REF when autothrottle mode engages.
The autothrottle speed mode only engages when VNAV, FLCH, and TO/GO are not active and the aircraft is in the air.
- c) Cruise (CRZ)
i. These are the two autothrottle modes in cruise:
- VNAV
- Autothrottle speed mode.
ii. These are the autothrottle mode annunciations in cruise:
- d) Descent (DES)
i. These are the three autothrottle modes in descent:
- VNAV
- FLCH
- Autothrottle speed mode.
ii. These are the autothrottle mode annunciations in descent:
- IDLE, THR, or HOLD shows for VNAV
- THR, or HOLD shows for FLCH
- SPD.
- e. Approach (APP)
SPD is normal mode in approach with glideslope active or in a manual approach.
i. Go-Around (GA)
A GA mode request causes the autothrottle mode to change to THR. A second GA request causes the autothrottle mode to change to THR REF. The TO/GA lever must be pushed to request GA.
ii. Flare Retard
Flare retard occurs when a specified altitude threshold has been achieved during approach with a command from the autopilot flight director system (AFDS). The autothrottle mode changes to IDLE during a flare retard.
1.6E.3.2 Autothrottle Disconnect
The autothrottle disconnects when there is a manual autothrottle disconnect or when there is thrust reverser application. This occurs after initial touchdown during rollout.
Source: Malaysian ICAO Annex 13 Safety Investigation Team for MH370, 8 March 2015, Factual Information MH370/01/15
The Factual Information was updated in 2018 by the Safety Investigation Report MH370/01/2018 which added new content but did not include all of the previous data.