Arrow auto gear extension oddness

[Roy Smith]

I was on a training flight a few days ago in a 180 HP Arrow. I was
demonstrating pitch stability. We were trimmed for straight and level
cruise (something like 23 inches and 2300 RPM at 3500 feet) when I
pushed us over into a dive, letting the airspeed climb well up into the
yellow arc.

Here's the strange part; the yellow "Gear in Transit" light came on
during the dive, as if the auto extension system thought we were trying
to land. The gear didn't actually extend, but the light came on and
(IIRC) the warning alarm when off too. I don't remember the exact speed
this happened at, but it was certainly well above Vlo.

Anybody have any idea what might have caused this? The auto extension
system relies on a combination of airspeed and throttle setting, but
both were well outside the normal operating conditions to trigger a gear
extension.

[BTIZ]

I'm guessing that the excess airspeed on the "doors" caused one of the doors
to pop open a bit and the micro switch thinks the door had come open.

I used to run into this all the time with a miss rigged nose gear door, bump
through some turbulence and the "gear in transit" would light up, only way
to clear it was to slow down and cycle the gear to get it to re latch.

BTW, I'm not sure about the older 180HP arrows, but most of the newer Arrows
have the auto extend mechanism disabled by either an AD or a Service
Bulletin.

Try a power off stall and see if the gear extends, it should not.

BT

"Roy Smith" > wrote in message
...
> I was on a training flight a few days ago in a 180 HP Arrow. I was
> demonstrating pitch stability. We were trimmed for straight and level
> cruise (something like 23 inches and 2300 RPM at 3500 feet) when I
> pushed us over into a dive, letting the airspeed climb well up into the
> yellow arc.
>
> Here's the strange part; the yellow "Gear in Transit" light came on
> during the dive, as if the auto extension system thought we were trying
> to land. The gear didn't actually extend, but the light came on and
> (IIRC) the warning alarm when off too. I don't remember the exact speed
> this happened at, but it was certainly well above Vlo.
>
> Anybody have any idea what might have caused this? The auto extension
> system relies on a combination of airspeed and throttle setting, but
> both were well outside the normal operating conditions to trigger a gear
> extension.

[Aaron Coolidge]

Roy Smith > wrote:
<snip>
: Here's the strange part; the yellow "Gear in Transit" light came on
: during the dive, as if the auto extension system thought we were trying
: to land. The gear didn't actually extend, but the light came on and
: (IIRC) the warning alarm when off too. I don't remember the exact speed
: this happened at, but it was certainly well above Vlo.

: Anybody have any idea what might have caused this? The auto extension
: system relies on a combination of airspeed and throttle setting, but
: both were well outside the normal operating conditions to trigger a gear
: extension.

I just checked the service manual. The "Gear in transit" light is connected
to the "up limit" switches. Recall that the Arrow gear is held up with
hydraulic pressure - there are no gear uplocks. If there is a leaky
hydraulic actuating cylinder or control valve, the gear will gradually
sag until one of the "up limit" switches opens. The "Gear in transit" light
comes on, as does the hydraulic pump, and the gear goes back up, closing
the "up limit" switch. I see this occasionally on an Arrow one of my friends
flies. There is also a pressure switch on the hydraulic system, to shut the
pump off when the gear is fully extended or retracted.

I don't think the auto extender is the culprit. If you are concerned,
have a mechanic put it on jacks, retract the gear, shut off the master,
and go to lunch (or home for the night). Then check which gear has sagged.
There's a nice flowchart in the service manual, as well.
--
Aaron Coolidge (N9376J)

[Roy Smith]

In article <bwc1c.12546$id3.4348@fed1read01>,
"BTIZ" > wrote:

> BTW, I'm not sure about the older 180HP arrows, but most of the newer Arrows
> have the auto extend mechanism disabled by either an AD or a Service
> Bulletin.

Why would you want to disable it?

[James M. Knox]

Aaron Coolidge > wrote in
:

> I don't think the auto extender is the culprit. If you are concerned,
> have a mechanic put it on jacks, retract the gear, shut off the
> master, and go to lunch (or home for the night). Then check which gear
> has sagged. There's a nice flowchart in the service manual, as well.

I think you are most likely correct - the auto extender is not involved.

It doesn't take MUCH movement of the gear door to be enough to let one of
those little microswitches come on (they are notorious for not going off
even with the gear up - and get adjusted and adjusted, until they break).
That far back (where the gear doors are) is probably a lower pressure area
(try to close the cabin door in flight some time <G>) and the extra speed
pulled it out a few millimeters.

Another likely factor... this is an older Arrow 180. They came with 1400
PSI switches. The 1400 PSI system was marginal. Newer ones came with 1700
PSI, which held the gear doors shut better (and for longer periods of
time). Many (but not all) have been upgraded, but we don't know if this
one has.

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

[Dave Butler]

Roy Smith wrote:
> In article <bwc1c.12546$id3.4348@fed1read01>,
> "BTIZ" > wrote:
>
>
>>BTW, I'm not sure about the older 180HP arrows, but most of the newer Arrows
>>have the auto extend mechanism disabled by either an AD or a Service
>>Bulletin.
>
>
> Why would you want to disable it?

So you can practice maneuvers near minimum airspeed without the gear dropping,
so the gear doesn't drop when the gear extension pitot gets iced over (it's not
heated). Of course, here we are talking about disabling it with the cockpit
control, not by AD.

IIRC from my Piper-flying days, there was an AD to disable the auto-extension,
then the AD was rescinded. While the AD was in effect, it was disabled on some
airplanes and never re-enabled. So there's a mix of airplanes out there with and
without the auto gear extension enabled.

[Aaron Coolidge]

James M. Knox > wrote:
<snip>

: It doesn't take MUCH movement of the gear door to be enough to let one of
: those little microswitches come on (they are notorious for not going off
: even with the gear up - and get adjusted and adjusted, until they break).
: That far back (where the gear doors are) is probably a lower pressure area
: (try to close the cabin door in flight some time <G>) and the extra speed
: pulled it out a few millimeters.

The landing gear doors aren't directly actuated by the hydraulic system;
there is a mechanical linkage to the nose gear. The last couple inches of
travel pulls the nose gear doors closed. As you say, a very small amount
of downward creep of the nose gear will cause the gear doors to open a
considerable amount. Add the low pressure area trying to pull the doors open
to a tiny leak in the actuating clyinder and you'll see just this phenomenon.

: Another likely factor... this is an older Arrow 180. They came with 1400
: PSI switches. The 1400 PSI system was marginal. Newer ones came with 1700
: PSI, which held the gear doors shut better (and for longer periods of
: time). Many (but not all) have been upgraded, but we don't know if this
: one has.

Ah, I did not realize that.

--
Aaron Coolidge (N9376J)

[BTIZ]

I did not realize the AD was rescinded.. actually I think the gist of the AD
was that Piper did not want to be responsible for aging equipment and have
to take the responsibility for a gear up landing because the "auto extender"
failed to protect the pilot who forgot/neglected/ it always worked before..
to personally extend the gear.

BT

"Dave Butler" > wrote in message
...
> Roy Smith wrote:
> > In article <bwc1c.12546$id3.4348@fed1read01>,
> > "BTIZ" > wrote:
> >
> >
> >>BTW, I'm not sure about the older 180HP arrows, but most of the newer
Arrows
> >>have the auto extend mechanism disabled by either an AD or a Service
> >>Bulletin.
> >
> >
> > Why would you want to disable it?
>
> So you can practice maneuvers near minimum airspeed without the gear
dropping,
> so the gear doesn't drop when the gear extension pitot gets iced over
(it's not
> heated). Of course, here we are talking about disabling it with the
cockpit
> control, not by AD.
>
> IIRC from my Piper-flying days, there was an AD to disable the
auto-extension,
> then the AD was rescinded. While the AD was in effect, it was disabled on
some
> airplanes and never re-enabled. So there's a mix of airplanes out there
with and
> without the auto gear extension enabled.
>

[[email protected]]

On 3-Mar-2004, Dave Butler > wrote:

> > Why would you want to disable it?
>
> So you can practice maneuvers near minimum airspeed without the gear
> dropping, so the gear doesn't drop when the gear extension pitot gets iced
> over
> (it's not heated). Of course, here we are talking about disabling it with
> the
> cockpit control, not by AD.
>
> IIRC from my Piper-flying days, there was an AD to disable the
> auto-extension, then the AD was rescinded. While the AD was in effect, it
> was disabled on
> some airplanes and never re-enabled. So there's a mix of airplanes out
> there
> with and without the auto gear extension enabled.


The gear extension pitot in our Arrow IV is heated. That aside, I don't
like the auto extension system for a number of reasons. I just leave it in
the override position for most operations.
--
-Elliott Drucker

[Dave S]

A used plane reference book that I have indicated that the "auto-extend"
mechanism got a less than stellar pilot into trouble and he sued.

Apparently when he suffered an engine failure, he didnt 1) keep his
speed up or 2) engage the "override lock" feature (a slide pin on the
override lever). The gear came down, and the plane came down much
quicker than "planned". Of course, the gear system functioned EXACTLY as
it was designed.


With regards to the original poster in the thread, I have had a
gear-in-transit light illuminate when making yellow-arc descents in
200hp Arrows (both with and without the "auto-extend" feature). My CFI
at the time attributed it to the slipstream pulling/sucking against the
recessed (but not enclosed) main gear just enough to open/close the
switch connected to the gear unsafe light.


Dave

Roy Smith wrote:
> In article <bwc1c.12546$id3.4348@fed1read01>,
> "BTIZ" > wrote:
>
>
>>BTW, I'm not sure about the older 180HP arrows, but most of the newer Arrows
>>have the auto extend mechanism disabled by either an AD or a Service
>>Bulletin.
>
>
> Why would you want to disable it?

[Jeff]

I have mine manually disabled, I do it because I dont like the gear comming down
untill I am ready and I like putting it up when I am ready.

Roy Smith wrote:

> In article <bwc1c.12546$id3.4348@fed1read01>,
> "BTIZ" > wrote:
>
> > BTW, I'm not sure about the older 180HP arrows, but most of the newer Arrows
> > have the auto extend mechanism disabled by either an AD or a Service
> > Bulletin.
>
> Why would you want to disable it?