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Autothrottle Computer

Technical Information

Catalogue No: C0201
Category: Engine Control
Object Type: Signal/Data Processor
Object Name: Autothrottle Computer
Part No: 42-007-04
Serial No: 0181077
Manufacturer: Marconi-Elliott Avionics
Division: Unknown
Platform(s): Boeing 747 
Year of Manufacture: circa 1980
Width (mm):
Height (mm):
Depth (mm):
Weight (g):
Location: Archive Object Store

Marconi-Elliott Avionics
Vendor Code K0656
Autothrottle Computer
Part No 42-007-04
Boeing P/N 60B80099-155
Serial No 0181077
Modification Record -


This Computer Unit is part of the Autothrottle system designed for the Boeing 747. The system comprises the Autothrottle Computer and the Pilot’s Mode Select Panel and it is available for all Boeing 747 variants. The equipment was designed to optimise speed control and throttle activity from take-off, through cruise to approach and landing. The objective was to reduce pilot workload, improve the fuel economy and enhance engine life.

This system operates in three main modes:-
● EPR Mode (Engine Pressure Ratio) is used in take-off, climb maximum continuous thrust and go-around). This ensures that the engine with the highest EPR indication acquires and maintains the limit value (less any selected decrement). All four engines are compared and that with the highest EPR is chosen as the controlling unit. The flight crew can balance the thrust controls to equalize the EPR for all the engines.
● Mach Hold Mode is used during cruise and maintains the Mach number existing at the time of mode engagement.
● Speed Select maintains the selected airspeed and is used for descent, holding approach and landing. A bias function compensates for gusts during the approach.

There are secondary modes such as Minimum speed protection, Flap speed limit protection and EPR limit protection.

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