A mechanic discovers that the pressurization valve on a turbine engine's oil tank is stuck in the closed position, preventing bleed air from pressurizing the tank. What is the most likely operational effect of this defect?
- AOil temperature will decrease significantly, causing thickened oil and reduced flow
- BReduced oil tank pressure may allow the oil pump to cavitate, resulting in inadequate lubrication, especially at altitude or high power
- CThe oil tank will overpressurize and rupture during high-power operation
- DEngine oil consumption will decrease because less oil escapes through the vent system
Show answer & explanationAnswer & explanation
Correct answer: B. Reduced oil tank pressure may allow the oil pump to cavitate, resulting in inadequate lubrication, especially at altitude or high power
Turbine engine oil tanks are often pressurized with bleed air to ensure a positive head of pressure at the oil pump inlet, preventing pump cavitation and foaming, especially during high-altitude or high-power operation. If the pressurization valve fails closed, the tank pressure drops, increasing the risk of pump cavitation and inadequate lubrication.
Why the other options are wrong
- A. Loss of pressurization does not directly cause a temperature drop.
- C. A failed-closed pressurization valve prevents pressure buildup, so overpressurization and rupture would not occur.
- D. Oil consumption is unrelated to tank pressurization status in this way.
Turbine Oil Tank Pressurization
A system using engine bleed air to pressurize the oil tank, ensuring positive oil pump inlet pressure and preventing cavitation at altitude.
- Uses bleed air through a pressurization valve
- Prevents pump cavitation and foaming
- Tank relief valve limits maximum pressure
Memory trick: Pressurized tank = 'pushing' oil steadily into the pump so it never runs dry-mouthed (cavitates).