91100 100 set
to the book
- Joined
- Dec 28, 2003
- Posts
- 694
The other day, we had a #1 Hydraulic System lose all (or most) of it's quantity. "E1 HYD PUMP FAIL" and "HYD 1 LOW QUAN" (or similar, you get the idea) were presented. The hydraulic page showed the quantity carrat pegged to the left, in the amber, with the electric pump ON. No other EICAS messages. Did the QRH, basically no actions required, just some info and references to other procedures should the system fail entirely, but we did slow to 250 in case the system dumped completed and opened the nose doors, and we also lowered the gear early in case it didn't and we needed to deal with that. The gear came down normally, but with some pressure flucuations between 2000 and 2900 (I might have seen it as low as 1600 while the gear was coming down). But it apparently wasn't enough to trip a failure message. We briefed the checklist for it and discussed declaring and bracing the people for landing, but we (he) decided not to. I figured we get it on landing, but I'm not the boss and thats not what this thread is about. So we land and get the failure, with the loss of the outboard brakes and steering. Long, dry, wide runway with negligable wind, so we lucked out with that, but we were disabled on the runway and had to get towed in. ATC, CFR and company ops were a little off-guard, wanting to know why we landed with a hydraulic failure without declaring, and the captain had to field a few phone calls, but again, not what this thread is about. Turns out, the pressure line out of the engine pump was sliced by a clamp and apparently dumped the contents in short order when we got the first two EICAS messages. I know that little to no demand is placed on the hydraulic system during cruise flight, and I wasn't surprised that we lost it on landing with the demand from the brakes, spoilers, and reverser. So there was just enough fluid left in the system to keep the pressure at 2900 (from the electric pump) with no load. But my question has to do with lowering the gear. I understand that some systems simply use hydraulic pressure to keep the gear from "banging" down hard from gravity, and there is little "pumping down" actually involved, which is suspect is the case here (after the fact), explaining why lowering the gear didn't trip a failure message. Anybody have any similar experiences? I learned quite a bit from this little misadventure, and I'm worried that the company's QRH doesn't quite cover all the bases in this situation.