US 4,718,229 AGranted

Failsafe electronic control systems

AssigneeROLLS-ROYCE plc

InventorPaul H. Riley

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Abstract

For flight safety reasons in gas turbine aeroengines it is desireable that in the event of malfunction of an electronic control system--such as a fuel control system--caused, for example, by overheating due to fire, the control system should protect the engine and the aircraft against the consequences of such a malfunction. In the present invention this is achieved by arranging that the control system is provided with a failsafe unit which monitors the condition of the control system and puts the engine into a failsafe control mode if a control system condition signal generated by the failsafe unit varies beyond a predetermined limit. Thus, to ensure safety under overheating conditions, the control system condition signal is representative of the temperature experienced by the fuel control system and the failsafe control mode is a speed-limiting control mode. Specific control mode sequences and corresponding control unit takeover ranges and constructions are disclosed which are effective to ensure that any control system failures have safe predictable results.

Claims9

Dependent claims

A fuel control system for a gas turbine aeroengine, including:

(a) means for sensing the rotational speed of the engine and producing a speed signal representative thereof,
(b) fuel flow metering means for metering the fuel flow to the engine,
(c) first, electronic, control means operative in conjunction with the fuel flow metering means to exercise a first and normal control mode over fuel flow to the engine, and
(d) second, electronic, control means operative in conjunction with the fuel flow metering means to exercise a second and speed limiting control mode over fuel flow to the engine in response to said speed signal, the arrangement being such that the second control means takes over control of fuel flow from the first control means whenever the speed signal exceeds a predetermined value indicating overspeed and retains such control until the speed signal falls below the predetermined value;
wherein the fuel control system is adapted to prevent overspeed of the engine due to failure of electronic components when the fuel control system is subjected to higher than normal operating temperatures, the control system further including means for sensing the temperature of the control system and producing a temperature signal representative thereof, and third control means operative to exercise a third and speed limiting failsafe control mode over fuel flow to the engine in response to said temperature signal, the third control means being adapted to irreversibly take over control of fuel flow from the first and second control means if the temperature of the control system exceeds a predetermined value indicative of likely failure of the first and second control means.

2 more elements

A fuel control system for a gas turbine aeroengine, including

(a) first, electronic, control means for generating a first fuel flow control signal for maintaning a normal control mode of the engine,
(b) second, electronic, control means for generating a second fuel flow control signal for preventing overspeed of the engine when said first fuel flow control signal fails to prevent such overspeed, and
(c) fuel flow metering means for metering the fuel flow to the engine in response to the first and second fuel flow control signals;
wherein the fuel control system further includes third speed-limiting failsafe control means adapted to monitor the temperature of the control system and take over control of fuel flow from the first and second electronic control means if the temperature exceeds a predetermined dangerous value.

1 more element

Dependencies are inferred from the claim text.