PPRuNe Forums - Hydraulics failure- helicopters

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Quote:

Originally Posted by ShyTorque (Post 10272351)

Failure of the collective pitch boost system on a Blackhawk can result in a very heavy collective. IIRC, it can push up with the equivalent force of 80lbs of weight. It was certainly enough to lift me out of my seat, even with the leg straps done as tight as I could bear them, it's really a two pilot job to fly it in that condition.

Can’t it be turned off? The S92 has a control boost system on al 3 controls, but has an ON/OFF switch on the overhead panel.

212Man,

Are you asking if each Hydraulic System can be turned off individually by a Control Switch?

I cannot imagine this day and time the Blackhawk would have the old S-58T/S-61 AUX/Primary Hydraulic set up as I cannot imagine the US Army not spec'ing a dual/equal system with the ability to shut off a malfunctioning system.

Quote:

Originally Posted by SASless (Post 10289639)

The UH-1C/M, AH-1G/S had a dual hydraulic system with no provision for turning off a malfunctioning system. There was a Test Switch that was spring loaded to BOTH, you could momentarily turning off a single system to do run-up checks. The AH-64 series has dual hydraulics with no HYD control switches at all. The AH-64 series have no hydraulics off capability, the flight controls simply move an input lever on the servo which moves the spool valve, the servo is bolted to the deck and cannot be manually moved.

Memory serves me the 540 rotor system Charlie Model had accumulators too.....for the Collective system was it?

It was designed to allow for two full cycles of the Collective....meaning from full up to fully down twice.

As it was only fifty years ago I flew the B and C model Hueys......the recollection of those days is getting a bit dim.

Quote:

Originally Posted by SASless (Post 10289731)

The 540 system had an accumulator charged by the #1 system for the collective in the event of a dual system failure. On shutdown you would "bleed" the accumulator by making slow strokes of the collective. For this test you were supposed to get four full strokes (full up, down, up, down). In the event of an actual failure there was no guarantee of the movement allowed and I can tell you that without hydraulics the collective was not movable, you would bend the lever before the blades moved. The AH-1G and AH-1S(MOD)/(PROD) had the same system. The AH-1S(ECAS)/(MC) had an electric pump emergency hydraulic system for the collective.