If a variable bleed valve fails to operate properly, what is a likely consequence?

• A. Improved compressor efficiency at high speed.
• B. Increased exhaust temperature only.
• C. Compressor surge due to inability to bleed air at high speeds.
• D. Immediate engine flameout.

Answer: (C)

Bleed air management keeps the high‑pressure compressor stable by diverting some air away when the engine is at high speed or under light load. This reduces the surge risk and helps maintain smooth flow through the compressor.

If the variable bleed valve doesn’t operate, the engine can’t relieve excess pressure in the compressor at high speeds. That reduces the surge margin and makes the compressor prone to surge—an unstable flow condition with strong pressure fluctuations, rough operation, and potential damage to the compressor and engine.

So, the likely consequence is compressor surge due to the inability to bleed air at high speeds. An improvement in efficiency wouldn’t come from a failed bleed system, exhaust temperature isn’t the direct outcome, and flameout isn’t an immediate result of this fault.