"Andrew Gideon" wrote in message
online.com...
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I've been reading the POH for my club's 182RG, and I find myself
surprised.
The manual gear extension replies upon the same hydrolic pressure system
as
the powered mechanism.

Isn't that insufficiently redundant?

I'm not sure what I expected - perhaps something purely mechanical. But I
didn't expect a lone pressure system to be a single point of failure.

Is this normal?

The Cessna 172RG is similar.

Hydraulic pressure is used to hold the gear up. The pump runs every few
minutes to maintain hydraulic pressure. Unfortunately, if the pump or
another part of the hydraulic system fails, the gear will come down only
part way, streaming behind the airplane like a duck with broken legs.

The manual system is just another pump, only it is only capable of lowering
the gear. If you lose hydraulic pressure the manual system will provide
enough pressure to lower the gear and lock it in place if there is any fluid
in the system at all. You would have to spring a leak at the bottom of the
sump to lose all your hydraulic fluid.

If someone absolutely cannot get the gear down and locked it is nearly
always because of some fracture at the pivot point. No backup system would
salvage that -- the landing gear is physically broken.

I personally have seen the gear system work with no hydraulic fluid left in
the reservoir -- just a little bit left in the lines. The emergency
extension lever was not even needed.

The landing gear system is not all that critical anyway. If more redundancy
is required, the weight penalty is better applied to other systems.