Generic Aircraft hydraulics (LOW SYS PX, VIBRATONS THROUGHT AIRFRAME) 1

[jayhoyte]

I have a scenario:
"pilot reports No1 Hyd sys showing low px. vibration experience throughout airframe. px indication fluctuates between 100 & 1000 psi"

I have put this down to pump cavitation or air trapped in the system. As I forestated this is a generic a/c hyd sys but can anyone advance on my fault diagnosis?

thanks for your attention

merry christmas

 

[MikeHalloran]

Check the hydraulic system accumulator for, e.g., bladder failure, no/wrong nitrogen precharge, stuff like that.



Mike Halloran
Pembroke Pines, FL, USA

 

[jayhoyte]

Thanks for your input

merry christmas

 

[bsmith123]

Not sure what kind of system you are working on---G/A, military etc but here's some food for thought.

I work on 60 GPM 3000 psi systems so bear that in mind

Airframe vibes sounds pretty drastic--how is the pump driven? Check the pump, accessory drive or gearbox that drives it for problems. Sounds like something could be getting ready to come apart

air could account for flux in pressure but generally speaking should go away as air bubbles are broken down and go into solution unless you have a massive amount in the system---this would then manifest itself as low reservoir volume---maybe then you keep running low on hydro hence the pressure flux. Operate the system and look for reservoir level drop. Another symptom is servicing a low system just after operation then hi reservoir levels or dumping overboard just after shut down. The major airframe vibes don't seem consistent with this though.

obvious to have checked the filters and part number of the filters

you could look for bypasses---hydraulic equivalent of a short circuit. fluid passing from a pressure line into return or sometimes another system (fluid transfer between system). This can result in hot--really hot components (the ones that are bypassing. For your problem you would most likely have to have one hell of a massive bypass from pressure to return. The constant unlimited demand for flow would have an effect on pressure throughout the system---hook up a gage to return (on the servicing port QD) while looking for big return pressures. a bypass can overpressurize return while normal movement will give you a modest rise and fall from static return pressures. looking at the flowmeter on a hyd test stand will also help. You could also test suspect components by pressurizing them and reading return pressures on a gage


hope that helps--be great to hear what you find