Fuel control system for gas turbine aeroengine overspeed

摘要

The fuel control system (10) aeroengine includes an overspeed limiter unit (24) operative to limit fuel flow (12) when engine speed (NH) exceeds a predetermined safe value. It is conventional for such overspeed limiters to be activated only in the event of an overspeed, so to obviate the possibility that the limiter unit (24) may fail unnoticed whilst the unit is dormant, the invention utilises the limiter unit as an active part of the fuel control system on a continuous basis. The overspeed limiter unit (24) is used to control the pressure drop ( DELTA P) across a fuel metering unit (18) as a function of engine speed (NH), except when it is actually performing its overspeed limiting task. In this way, any failure in the limiter unit (24) will be immediately apparent due to its effect on the functioning of the system. …IMAGE…