Backup for dropping the gear

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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?

- Andrew

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In a previous article, Andrew Gideon said:
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?

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. As a matter of fact, sometimes in
turbulence you get a gear unsafe light and you have to quickly cycle the
gear lever to repressurize the hydraulics.


--
Paul Tomblin http://xcski.com/blogs/pt/
"Maybe if your vcr is still blinking 12:00 you shouldn't be using Linux."
-- Slashdot poster

Piper gear PIREP

The nose gear on the Seminole and many other similar Pipers has a coaxial
pair of springs.
In my case the inner spring failed, jamming the outer spring and resulting
in a nose idiot light not coming on.
Expecting a collapse, I landed the Seminole like a tail dragger and walked
away.

The springs are a few dollars. Replace them periodically.
My Seminole was on leaseback,
I was scheduled between two renters.
Better me than them.

Old pilots have paid attention to detail.
So said one.

Blue skies.
H.



"Paul Tomblin" wrote in message
...
In a previous article, Andrew Gideon said:
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?

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. As a matter of fact, sometimes in
turbulence you get a gear unsafe light and you have to quickly cycle the
gear lever to repressurize the hydraulics.


--
Paul Tomblin http://xcski.com/blogs/pt/
"Maybe if your vcr is still blinking 12:00 you shouldn't be using Linux."
-- Slashdot poster

(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

Peter,

You have got to expand your horizons g. In a number of the Piper
singles the gear does come down if the engine takes the day off. The
automatic extension system, if not disconnected or overridden, will
extend the gear if the engine quits. It's why I override the system
on takeoff as I have no burning desire for the gear to extend should
the engine quit.

It's also a fun system when you are descending at high speed through a
layer of stratus clouds full of rime ice and the pitot heat decides
that it doesn't want to heat the little pitot tube on the left side of
the fuselage that provides the input for the automatic gear system, it
freezes up and extends the gear suddenly when you are whistling along
in the yellow arc. Doesn't do anything to improve your outlook on
life at all.

All the best,
Rick

"Peter Duniho" wrote in message ...
"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

"Rick Durden" wrote in message
m...
You have got to expand your horizons g.

That's always been true.

In a number of the Piper
singles the gear does come down if the engine takes the day off.

But not because of the failure of the hydraulic system. Kyler's comment
clearly was based on an assumption that without engine power, there would be
no hydraulic pressure, and that without pressure, the gear would drop (the
first assumption being the incorrect one, but the second is incorrect in
other airplanes as well).

And actually, while I haven't flown the Pipers you're referring to, my
understanding is that the gear extension was based on airspeed, not engine
power. Your comment about the behavior of such systems in icing conditions
would seem to reinforce this understanding. Perhaps you could elaborate on
why it is you say that engine failure alone will result in the gear
extending.

Or perhaps you meant that the drop in airspeed that normally results after
an engine failure (to achieve best glide) is enough to cause the gear to
extend. In which case I'd argue that it wasn't the engine failure, but the
airspeed change that caused the gear to extend (I'd also wonder why the
system was designed such that the activation airspeed was at or above best
glide...seems pretty non-optimal to me).

Pete

"Peter Duniho" writes:

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

Ah...that makes a difference.

Furthermore, loss of pressure should only happen if there's a leak in the
system somewhere;

I can buy that (although my gear commonly "droops" after many checks) with
the emphasis on "should". (On farm equipment, the typical culprit is the
controlling valve.)

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.

Yeah, it looks like it would need to be "Do not leak hydraulic fluid in
excess of max. gear extension speed."

--kyler

In a previous article, Kyler Laird said:
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.

Yeah, it looks like it would need to be "Do not leak hydraulic fluid in
excess of max. gear extension speed."

On the Lance (which is the only plane I have any experience with), even if
you lost hydraulic fluid, air pressure would hold the gear up against the
springs until you dropped down to max gear extension speed. I suspect
you'd get a bit more drag from the gear drooping slightly into the
airstream, though.



--
Paul Tomblin http://xcski.com/blogs/pt/
You can be jailed for lying about being good in bed.
-- Lionel, paraphrasing the Criminal Code of Canada, 159(3)(b)(i)

"Andrew Gideon" wrote in message
online.com...
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.

I'm not sure there's enough standardization in gear retraction/extension
systems to say what's "normal". However, certainly the lack of redundancy
is common enough on light planes. In fact, not only is the gear on my
airplane designed similarly, the flaps and elevator trim use the same
hydraulic system. A failure in the hydraulic system that takes out certain
lines, and/or results in a loss of fluid would affect all three systems
simultaneously.

Occasionally you might find a "fail safe" system like the one on the Lance
that Paul mentions, but as he even points out, those systems come with their
own issues. Aircraft designers often come to the conclusion that the extra
complexity, cost, and weight isn't worth the marginal increase in safety.

Especially when one considers just how dangerous a gear-up landing *isn't*,
it's not hard to see why that conclusion is reached so often. As far as I
know, such "insufficiently redundant" systems are more common than
"sufficiently redundant" ones.

Pete