FAA Aviation Mechanic Airframe (AMA)Hydraulic and Pneumatic SystemsMedium
A hydraulic system accumulator is used to dampen pressure surges and provide emergency power for landing gear extension. What is the primary function of the air/nitrogen precharge in a piston-type accumulator?
- ATo filter contaminants from the fluid before it reaches the pump
- BTo cool the hydraulic fluid as it passes through the accumulator
- CTo pre-load the piston so fluid can be stored and instantly available under pressure
- DTo act as the primary source of hydraulic pressure for the entire system
Show answer & explanationAnswer & explanation
Correct answer: C. To pre-load the piston so fluid can be stored and instantly available under pressure
The nitrogen precharge pushes the piston against the fluid side, so when system pressure drops or a surge occurs, stored fluid under precharge pressure is instantly available. It does not filter, cool, or serve as the primary pressure source.
Why the other options are wrong
- A. Filtration is performed by dedicated filters, not accumulators.
- B. Accumulators do not function as heat exchangers.
- D. The pump, not the accumulator, is the primary pressure source.
Accumulator Precharge
Nitrogen gas charge on one side of an accumulator piston/diaphragm that preloads stored hydraulic fluid for instant release.
- Precharge is typically about 1/3 of system operating pressure
- Dampens pressure surges and stores emergency power
- Piston, diaphragm, or bladder type accumulators
Memory trick: Nitrogen is the spring that pushes fluid out fast.