Hydraulic Systems

[Saint Jack]

Bell JetRanger Series:

1. Improperly connected quick-disconnect coupling (self-sealing) popped off on short finals resulted in very heavy control loads but no control feed-back as fluid was trapped in the irreversible valves.

2. Flexible hose to/from hydraulic pump chaffed through adjacent hydraulic rigid tube (all JetRanger engineers know this problem) and all fluid was lost resulting in very heavy control loads plus control feed-back due to the lack of fluid in the irreversible valves.

[Non-PC Plod]

I cant help thinking that the potential fire risk with hydraulic failures tends to get a good ignoring in RFMs. A highly-inflammable liquid being atomised at 3000 psi in the event of a leak becomes an extremely highly inflammable cloud. Going back to the Sea-King incident - didnt they end up deliberately rolling the aircraft into the Sea to put the fire out, because the whole cabin & cockpit was a big fireball from the internal hydraulic leak?

[MightyGem]

I also think that the "land as soon as practicable" we may get in RFM when dealing with hydraulic malfunctions should rather be considered as "land as soon as possible"

Yes, that was always the case in my previous life as a Lynx pilot. It's "practicable" for our 135. I'm still not sure what I would do in the event of a Hyd Fail caption.

[drop lead]

Hydraulic fluid fire

Geoffers; also refer to the thread "MHS Puma off radar screen today", I believe the incident lead to Eurocopter requiring operators to use MIL-H-83282 "fire resistant" spec hydraulic fluid rather than the older spec MIL-H-5606, why anyone would still be using 5606 beats me!

[oldbeefer]

Early days of the Puma - returning to Odious one night. Hit the 'down' switch. Big bang, hydraulics lost which led to loss of AP. Two greens only - no nose green. Managed to get the AP back in by pulling the emergency lowering handle, which shut off the leak and restored the pressure (this action was subsequently added to the FRCs). Came to hover near dispersal. Nose leg way forward of the vertical - when the gear went down, the front of the jack blew off. No procedure then for gear malfunctions. Short of fuel so carried out a rotors turning refuel in the hover while the engineers tried to find some sandbags. They did - piled them up under the nose, shut down and didn't use rotor break. Off to the bar for a beer! Eurocopter subsequently added a restrictor to the line to reduce the pressure to that jack.

[Geoffersincornwall]

Thanks

Some really interesting stuff coming to light. In view of JimL's unhappy experience with his S55 I wonder what effect spilling a cup of coffee on the AW139 Hyd Control Panel would have. It might be worth asking the question if it is physically possible to short-out that control panel. Is it really a good idea to put the ability to switch OFF both hydraulic systems into one box? Is there a requirement for that 1-OFF/2-OFF switch to be absolutely bomb-proof?
Anybody out there got any inside knowledge?

G.

[rick1128]

A few years ago, when I was at Evergreen, they had a 212 doing training, when the Chief Pilot turned off the #1 HYD system. They started having problems and he turned the #1 system and they couldn't regain control. They did a hovering auto and spread the rear crossover tube and did other damage. What happened, was somewhere in this process the tail rotor HYD actuator failed. What the exact failure was I don't know. What I do know is that they did all the HYD system test during the pre-takeoff checks and everything worked within limits. And that another pilot some days before this event had turned the #1 system off in flight, had problems, turned it back on and regained control. Then he didn't tell anyone what had happened.