Backup for dropping the gear

The hand pump gives redundancy to the hydrolic system only in the event that
the electric power pack fails. In the event of an electrical failure, the
hydrolic system itself would still be intact, but the hand pump is a one way
pump, only allowing you to pump the gear down, not up. The 182RG's gear
system is a closed hydrolic system, as it only operates the gear. To have a
complete hydrolic system (gear) failure such as a blown hydrolic line or
fitting causing the system to loose it's entire quantity of hydraulic fluid
would be quite rare I would think. I'd much rather have a backup system to
an electrical system malfunction than have a back up to an hydrolic system.

Jim

(Paul Tomblin) writes:

The P32R Lance that I'm currently checking out in uses hydraulic pressure
to hold the gear *up* against springs and gravity - lose the hydraulic
pressure and the gear goes down.

Cool! So if you lose your engine the plane helps you get back to the
ground quickly by extending the air brakes? Is there an override (for
those who fly over inhospitable terrain/water)?

Is there a placard that says "Do not lose engine power in excess of max.
gear extension speed."?

--kyler

"Kyler Laird" wrote in message
...
(Paul Tomblin) writes:

The P32R Lance that I'm currently checking out in uses hydraulic pressure
to hold the gear *up* against springs and gravity - lose the hydraulic
pressure and the gear goes down.

Cool! So if you lose your engine the plane helps you get back to the
ground quickly by extending the air brakes? Is there an override (for
those who fly over inhospitable terrain/water)?

The hydraulic pressure is probably provided by an electric pump (I don't
know for sure, not being familiar with that specific airplane).
Furthermore, loss of pressure should only happen if there's a leak in the
system somewhere; theoretically, once the system has pressurized with the
gear up, the hydraulic pump wouldn't need to operate at all. Even if there
was a slightly leaky o-ring or valve somewhere, requiring the occasional
operation of the pump, it seems likely that the battery could handle the
load for the brief period of time it would take to glide to a landing.

Bottom line: there's no reason an engine failure would cause the gear to
extend.

Is there a placard that says "Do not lose engine power in excess of max.
gear extension speed."?

There would be no need for such a placard.

Pete

"C J Campbell" wrote in message
...
I suppose you could also run the brakes off the same hydraulic system as
the
gear, too. After all, if the gear fails you won't be needing any brakes.
:-)

Well, actually...the brakes do use the same reservoir for their hydraulic
fluid. But all pressure for the brakes comes from the master brake
cylinders, not the hydraulic pump used for the other three systems. Only a
leak in the hydraulic line between the master and slave cylinders for the
brakes would cause any trouble with the brakes (by emptying out the brake
lines, along with the rest of the hydraulic system).

Again speaking only of light planes, I doubt there are any that use a
hydraulic pump to operate the brakes.

As for whether you'd need the brakes, I guess that depends on whether the
gear fails in the up position, or down.

Pete

"C J Campbell" wrote in message
...
Hydraulic pressure is used to hold the gear up. The pump runs every few
minutes to maintain hydraulic pressure.

Assuming the 172RG gear system is similar to the 182RG and 177RG systems, if
the pump is running on a regular basis, you have a leak somewhere. Not
necessarily one venting fluid, but one allowing fluid from the pressurized
side of the system to the non-pressurized side.

(The pressurized side changes, of course, depending on whether you're
raising or lowering the gear)

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.

A leak on the pressurized side of the system would allow the hand-pump (or
the electric pump) to pump all the fluid out of the system. You don't need
to spring a leak at the bottom of the sump to lose all your fluid.

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

True without a doubt!

Pete

Mark Astley wrote:
Yet other planes have an emergency
tank for blowing the gear down (beech maybe?).

Bonanza's: 50 turns of the little crank, located behind the little door
on the back of the main spar below the copilot's seat. The crank is
attached to a gear that meshes with another gear on the shaft attached
to the gear motor and landing gear.

"Peter Duniho" wrote in message
...

A leak on the pressurized side of the system would allow the hand-pump (or
the electric pump) to pump all the fluid out of the system. You don't
need
to spring a leak at the bottom of the sump to lose all your fluid.


It actually does not pump it all out, as the intake for the pump is high
enough to leave a small reservoir to be used by the emergency extension
lever.

"C J Campbell" wrote in message
...
It actually does not pump it all out, as the intake for the pump is high
enough to leave a small reservoir to be used by the emergency extension
lever.

Fine. However, as soon as you start using the manual pump, you will still
wind up pumping the fluid out.

My main point is that it is not necessary to have a leak at the bottom of
the sump in order to lose all the hydraulic fluid.

Pete

"Mark Astley" wrote in message ...
snip
There are
various anecdotes about pilots reaching out the door with the towbar to pull
the gear all the way down.


I read one in a flying mag several years ago. Under the direction
of a ground based A&P, the passnger accessed the empty hydraulic
reservoir from inside the cabin and replenished it with a biologically
manufactured fluid. It was enough to get the gear locked and they
landed safely.

I'll bet the A&P that had to work on that system was ****ed :-)

John Galban=====N4BQ (PA28-180)

"C J Campbell" wrote
The Cessna 172RG is similar.

All the Cessna retract singles have the same basic gear design. Only
difference is some of the earlier 210's had an engine driven hydraulic
pump.

Hydraulic pressure is used to hold the gear up. The pump runs every few
minutes to maintain hydraulic pressure.

If the pump is running every few minutes, there's a leak somewhere.

You would have to spring a leak at the bottom of the
sump to lose all your hydraulic fluid.

That's absolutely not correct. All you have to do is blow a high
pressure hose and you will pump all the hydraulic fluid overboard, and
completely lose any ability to lower the gear. Know more than one
person who has had it happen.

Michael