A330 hyd. pressure fluctuating on gnd w/elec. pumps
 

Anybody ever come across an elec. hyd. pump pressure fluctuation on ground, with all 3 hyd. systems pressurized, going from 3000 to 1700psi and back to 3000 in a matter of a second or two. In my case it was the blue hydraulic system. Note that no flight controls were being moved at that time, so technically no demands on the hydraulics. It is not the first time I came across this issue with the A330. Just wondering if it's a common issue with the A330, or else maybe I have a pump or hyd. components issues.

Thanks!

Ruptured accumulator, not uncommon.

if all 3 elec pumps were doing it I'd hazard a guess at the electrical source being the cause.

I'd say the accumulator is a good shout, have seen it a few times on the single aisle bus.

sounds more than just the blue?

if it is just the blue, have a look at the accumulator charge pressure, normally around 1800psi, if it is 0 then a fair bet the bladder has gone. There are checks in the MM to do. However that is unlikely to cause fluctuating pressure. Sounds more like a pump problem or one of the valves in the braking system shuttling? Or the age old problem of air in the system and a proper bleed is needed.

AME343,


If blue sys hydraulic quantity was full, then that would/should rule out pump cavitation. Perhaps a dirty pressure sensor cannon plug connector for the blue sys?


McHale.

The accumulator is the most likely place to start, or an electrical phase gone on the pump. I'd also check the system is not overfull. I've seen it with the reservoir indicating over the top of the full indication box on ECAM causing pressure fluctuations, theory being that the physical reservoir is so full it cannot pressurize properly as the head pressure keeps dropping off and then recovering so causing varying fluid supply pressure to the system.

While you may not be commanding Flight Control surfaces to move, pull up the Flight Control page and look at what your Ailerons,Elevators and even Spoilers are doing. You'll soon see why your AC pump pressures are fluctuating.
Remember, AC pumps on a 330/340 are low flow, high pressure. As you attempt to fair the drooping surfaces, you run out of flow and subsequently, pressure. Over and over.
Try it.
SF

AME343,


What was the fix in the end?


McHale.

A330 hydraulic fluctuations
 

AME343
Ive been away along time so might have missed something..
During the Blue Hyd pressurisation you say no flight controls were operated but in fact the ailerons were, as they were lifted from the droop position.
It is common to see the HYD pressure cycling when pumps are first switched on as the accumulaters become charged, as you noted, approx 3000 down to 1700 and back, me normally with shaking of the aircraft. You mentioned this occurred within a couple of seconds, did the pressure then finally stabilise at 3000??
The AMM will guide you to keep the pump running to charge the brake system for a few minutes. As already mentioned the Airbus accumulators are a likely fault in the system and do suffer from rupturing.
If you were concerned about the pump, switch the B leak measurement valve closed, does the pressure now hold at 3000psi???
You must have an answer by now but some more food for thought..

TW