Which bleed valves fail in the closed position?

• A. Engine PRSOV, APU LCV and Engine HP bleed valve
• B. All bleed valves
• C. Only the 10th stage bleed valve
• D. None fail closed

Answer: (A)

Bleed air valves are designed to control and isolate air taken from the engine or APU to power packs, start systems, and other pneumatic needs. When a valve is stuck or its actuator binds, it can fail in the closed position, cutting off bleed air even though a command to open was issued. The engine PRSOV (Pressure Regulating Shutoff Valve) is a prime example: it acts as the shutoff that must open to allow bleed air through and regulate downstream pressure. If it sticks closed, no bleed air reaches the packs or other bleed-powered systems. The APU LCV (APU bleed load/valve control) serves a similar isolating role for APU bleed air, so a failure closed here also stops bleed air from the APU path. The engine high-pressure bleed valve is another path for bleed air from the engine; a closed fault here blocks the supply and can prevent starting air or pack operation.

The 10th stage bleed valve, while part of the bleed system, does not share this typical closed-fault tendency in the same way and is not the one commonly seen stuck shut. That’s why the combination of valves that fail closed includes the PRSOV, the APU bleed valve, and the HP bleed valve, but not the 10th stage bleed valve.