AVM Powerplant Practice Test

What is the purpose of the dump valve used on aircraft gas turbine engines?

The valve controls compressor stall by dumping compressor bleed air from the compressor discharge port under certain conditions Maintains minimum fuel pressure to the engine fuel control unit inlet and dumps excessive fuel back to the inlet of the engine-drive fuel pump The fuel is quickly cut off to nozzles and the manifolds are drained preventing fuel boiling off as result engine heat The valve acts as a relief valve for fuel lines during overheating

Correct Answer:

The fuel is quickly cut off to nozzles and the manifolds are drained preventing fuel boiling off as result engine heat

Explanation:

The key idea is to purge fuel from the hot fuel lines and manifolds so fuel doesn’t boil after shutdown. When the engine is being shut down, the dump valve opens and quickly cuts fuel to the nozzles while draining the fuel from the manifolds. This return or purge prevents liquid fuel from sitting in heated passages and boiling, which could cause vapor formation or a difficult restart later. In practice, this valve is used during shutdown or purge operations, not during normal running. The other descriptions refer to bleed-air control, fuel-pressure management, or a simple relief function, which aren’t the purge-and-drain purpose of the dump valve.

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