FAA Aviation Mechanic Powerplant (AMP)Fuel, Induction and LubricationHard
A technician is inspecting a turbine engine's oil tank pressurization system. If the pressurization valve is found to be stuck open, what effect would this most likely have on the oil system operation at high altitudes?
- AIncreased oil pressure due to over-pressurization.
- BDecreased oil temperature due to enhanced cooling.
- CNo significant effect, as the system is primarily for ground operations.
- DReduced oil scavenging efficiency and potential foaming.
Show answer & explanationAnswer & explanation
Correct answer: D. Reduced oil scavenging efficiency and potential foaming.
A turbine engine's oil tank is pressurized to ensure proper oil scavenging from the bearing sumps and to prevent oil foaming at high altitudes where ambient pressure is low. If the pressurization valve is stuck open, the tank pressure will drop, leading to reduced pressure differential for scavenging and increased foaming due to dissolved gases coming out of solution.
Why the other options are wrong
- A. A stuck-open pressurization valve would lead to under-pressurization, not over-pressurization, thus reducing oil pressure, not increasing it.
- B. Oil temperature is primarily controlled by the oil cooler and fuel-oil heat exchanger, not directly by tank pressurization.
- C. The pressurization system is critical for high-altitude operation to maintain scavenge efficiency and prevent foaming, so a malfunction would have significant effects.
Turbine Oil Tank Pressurization
Turbine engine oil tanks are pressurized to maintain a positive pressure differential for efficient oil scavenging and to suppress oil foaming, especially at high altitudes.
- Prevents cavitation in scavenge pumps.
- Reduces oil foaming by keeping dissolved gases in solution.
- Ensures adequate oil flow to bearings in varying atmospheric pressures.
Memory trick: Pressurization Prevents Problems