FAA Aviation Mechanic Airframe (AMA)Fuel, Cabin and Ice Control SystemsMedium
A technician inspects the internal baffles of a wing fuel tank on a transport-category aircraft and finds one-way flapper check valves installed within the baffle openings. What is the primary function of these check valves?
- ATo regulate the rate of fuel vapor venting to the surge tank
- BTo control fuel transfer between the main tank and the auxiliary tank
- CTo prevent fuel from entering the vent system during a tank overfill
- DTo allow fuel to flow toward the boost pump area while preventing it from surging back during maneuvers
Show answer & explanationAnswer & explanation
Correct answer: D. To allow fuel to flow toward the boost pump area while preventing it from surging back during maneuvers
Baffle check valves (flapper valves) allow fuel to flow one way toward the boost pump sump area while restricting fuel from surging away from it during rapid attitude changes, helping to keep the pump inlet submerged.
Why the other options are wrong
- A. Venting rate is controlled by vent lines and flame arrestors, not baffle checks.
- B. Tank-to-tank transfer is controlled by transfer valves, not baffle check valves.
- C. Overfill protection is provided by vent float valves, not baffle checks.
Fuel Tank Baffle Check Valve
A one-way flapper valve located in internal wing tank baffles that allows fuel to flow toward the boost pump sump while limiting reverse surge.
- Keeps fuel pooled around the boost pump inlet
- Opens one direction, closes to prevent surge-away flow
- Reduces risk of pump cavitation during maneuvers
Memory trick: Flapper lets fuel in toward the pump but blocks it from running away.