Backup for dropping the gear

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

snip

Safety features sometimes spawn new hazards while eliminating old ones. The
automatic gear extension system is a good example. "At high density
altitudes," relates one owner, "the gear sometimes drops after it has been
retracted. This, of course, nullifies any climb!" Indeed, there have been
incidents in which the airplane might have been able to climb out safely had
the gear not dropped at the wrong moment, causing a stall/mush into the
terrain.

Then there are Arrow pilots who lose their engines and decide to ditch with
the gear up. Unfortunately, some forget to override the automatic extension
system. The gear plops out seconds before splash down-sending the Arrow head
over heels.

Such mishaps are rare-we only counted a few (none fatal) in our five-year
survey. But in mid-1987 Piper, then owned by Lear-Siegler, ordered the
system deactivated because of concern over liability suits. It sold kits to
do so, and told customers it wouldn't provide parts to repair the existing
system. Piper sold 1,400 kits.

One year later, Piper-then owned by M. Stuart Millar-withdrew its order to
deactivate the automatic extension system, provided that pilots "take the
necessary actions to assure that any pilot flying these aircraft are fully
advised of the system and its proper operation." In part, Piper was
responding to the complaints of irate owners who believed the system worked
often enough to be desirable.

snip

***************************************

Throttle coming back to a certain point actuates a microswitch and/or the
airspeed dropping to 95 knots drops the gear... There was an override, but
you had to remember to actuate it... Every Arrow that I was involved with
had the autoextension deactivated, period... Can't have the airplane killing
me, I can do a fine job of that all on my own...

denny

In a previous article, "Dennis O'Connor" said:
Then there are Arrow pilots who lose their engines and decide to ditch with
the gear up. Unfortunately, some forget to override the automatic extension
system. The gear plops out seconds before splash down-sending the Arrow head
over heels.

First item in the emergency checklist is to put the gear override on.


--
Paul Tomblin http://xcski.com/blogs/pt/
Microsoft - Where quality is job 1.0.1

In a previous article, "Peter Duniho" said:
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

The POH for the Lance isn't 100% clear on this, but my understanding is
that with the emergency gear extension, the gear will come down if you go
below a certain manifold pressure at one speed, or will come down
regardless of the manifold pressure at a lower speed.

The POH says "Some aircraft also incorporate a pressure sensing device in
the system which lowers the gear regardless of gear selector position,
depending upon airspeed and engine power (propellor slipstream). Gear
extension is designed to occur, even if the selector is in the up
position, at airspeeds below approximately 103 KIAS with power off. The
extension speeds will vary from approximately 91 kts to approximately 103
KIAS depending on power settings and altitude."

Actually, reading that again, it's possible that what is happening isn't
that it comes on at a lower speed if you have power on, but that the
propellor slipstream holds the gear up against the springs if you have
power on.

Sometimes I learn more answering other people's questions than I do
getting answers to my own.

--
Paul Tomblin http://xcski.com/blogs/pt/
If you're not part of the solution, you're part of the precipitate.

"Paul Tomblin" wrote in message
...
The POH for the Lance isn't 100% clear on this, but my understanding is
that with the emergency gear extension, the gear will come down if you go
below a certain manifold pressure at one speed, or will come down
regardless of the manifold pressure at a lower speed.

Well, if it's manifold pressure based, then an engine failure would only
cause the gear to come down if the failure was caused by a blocked air
intake, or if the pilot later pulled the throttle to idle. Again, an engine
failure would not, in and of itself, necessarily cause the gear to extend.

[...]
Actually, reading that again, it's possible that what is happening isn't
that it comes on at a lower speed if you have power on, but that the
propellor slipstream holds the gear up against the springs if you have
power on.

I don't know how the "propeller slipstream" could hold the gear up. The
only "propeller slipstream" I'm aware of is the helical movement of the air
around the fuselage, and compared to the other forces involved I doubt it's
all that strong.

I think it's interesting that the POH puts "propeller slipstream" in
parentheses after "engine power", because to me it's not at all clear what
they mean. The two aren't exactly equivalent, so it's odd they would use
them as if they were. The parenthetical comment ought to add information,
but to me it just confuses things.

Pete