Dual Trim Switches?

Definitely outside my experience. As I recall, we could push the trim switch
fore and aft to run the trim motor, and push down on it to disengage the
autopilot.

Looking at your picture, I was thinking back to the days when pilots had no
way to exchange experiences at all...now we can send pictures to illustrate
points.

Bob

"tjd" wrote in message
ups.com...
On Sep 28, 7:52 pm, "Bob Gardner" wrote:
My memory isn't what it used to be, and though I flew a lot of planes
with
trim switches I don't remember there being two. I must have a "two
separate
actions" thing going on in my thinking machine.

In the G1000 172SP I flew, the natural thing is for your thumb to move
both switches simultaneously; moving them individually (during
preflight) takes conscious effort. Kind of like a split master
switch, it's much easier to turn both sides on than either one by
itself. You can see the arrangement pretty well in this pictu

http://www.aeroclub-tsl.gr/files/depanel.jpg

Like I said, I'm not sure how often a stuck switch is the cause of
runaway trim but this design all but eliminates that possibility at
very little cost. Of course it's almost twice as likely for a switch
to fail open and leave you with no electric trim, but I'd much rather
have that happen than having the trim run away and having to fight it
or pull a breaker at an inopportune moment.

todd.

"R. Gardner" wrote in message
.. .
"Robert M. Gary" wrote in message
ups.com...
On Sep 28, 9:26 am, Bertie the Bunyip wrote:


There's 13 places where water gets stuck in that system.

I seriously doubt that.

-Robert, CFI

That is exactly what I was taught learning the Mooney M20C meny years ago!

Ron Gardner


Drains cost money and add points of failure, weight, and (nearly always)
drag. They are *only* placed where the manufacturer is convinced that water
might otherwise be trapped.

Peter

P.S.: Nevertheless, when this thread began, I really was tempted to suggest
that the multitude of drains was to collect enough fuel to run a
lawnmower--since we no longer throw it on the ground and most pilots don't
put it back in the aircraft. :-)

Peter

Using drained fuel for lawn mower.

When using 115-145 fuel I always filled up my Zippo when preflighting
and draining water out of tanks. We didn't have the plastic jars to
drain into so let fall to ground under bird (in old days). Had to be
careful and shake excess out of lighter (Zippo) or first couple of
times when lit, would get a 6 inch flame and could singe your eye
brows lighting your cigarette or pipe. )

Of course we never worried about the lead (TEL) in the gas (lots in
the high octane fuel) and inhaling it when lighting the tobacco (
Probably part of the cause of my lung problems today.

Big John

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


----clip----

P.S.: Nevertheless, when this thread began, I really was tempted to
suggest that the multitude of drains was to collect enough fuel to run
a lawnmower--since we no longer throw it on the ground and most pilots
don't put it back in the aircraft. :-)

Help

I flew a 'Top Hat' four way trim switch for thousands of hours and
never saw a second one. Anyone know where it was located?

Our emergency procedure for run away trim was to pull the circuit
breaker(s).

Big John

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


On Fri, 28 Sep 2007 09:43:28 -0700, "Robert M. Gary"
wrote:

On Sep 28, 9:15 am, Christopher Brian Colohan
wrote:
After flying Tomahawks and Citabrias, I took my first lesson in a
Cessna 172 last night. I asked many questions, but I had one question
which nobody in my flying club (including the chief pilot) knew the
answer to when I was the Why does the electric elevator trim have
two switches (both of which must be depressed) on the yoke instead of
one?

I assume this is a recent model 172. To avoid a stuck switch (or
shorted switch) from running the trim. In the preflight checklist that
Cessna provides one of the tests under the "trim test" section is to
ensure that the trim does not move with either of the switches is
moved by itself. Additionally you should ensure that the electric trim
does not work at all when the auto-pilot cut-off is held down.

The best theory I could come up with was "to avoid runaway trim if one
switch stuck", but that is not very satisfying...

Anyone know why?

Chris

Big John wrote in
:

Help

I flew a 'Top Hat' four way trim switch for thousands of hours and
never saw a second one. Anyone know where it was located?

Our emergency procedure for run away trim was to pull the circuit
breaker(s).



Switches like that are illegal now. You have to have passive fail systems
on trims and autopiots nowadays.



Bertie

Big John writes:

Of course we never worried about the lead (TEL) in the gas (lots in
the high octane fuel) and inhaling it when lighting the tobacco (
Probably part of the cause of my lung problems today.

Tetraethyl lead wouldn't cause lung disease so much as systemic lead
poisoning, but it's debatable whether or not you ingested enough to be at
risk. Much more dangerous is the practice of smoking itself, enough that it
probably eclipses the risk from inhaling tiny amounts of lead.

Mxsmanic wrote in
:

Big John writes:

Of course we never worried about the lead (TEL) in the gas (lots in
the high octane fuel) and inhaling it when lighting the tobacco (
Probably part of the cause of my lung problems today.

Tetraethyl lead wouldn't cause lung disease so much as systemic lead
poisoning, but it's debatable whether or not you ingested enough to be
at risk. Much more dangerous is the practice of smoking itself,
enough that it probably eclipses the risk from inhaling tiny amounts
of lead.



What, like you did chewing on the door jambs?


Bertie

Bertie

I'm going to the "Wings over Houston" Air Show at Ellington this week
end. Besides getting some cockpit time in the P-40 and P-51, I'll talk
to some of the current Heavy Iron drivers, with birds on display,
about what the trim is on the birds newer than I flew. From past shows
expect to see at least the F-15, F-16, F-117 and also Navy jets, Blue
Angels, etc. Probably some Chinese Migs that were kept at Ellington.

Its 62 years since I flew the P-40 and 58 years since I flew the P-51
so need the cockpit time to refresh where all the controls, etc.,
were/are )

Big John
************************************************** *****88

On Sun, 30 Sep 2007 07:47:28 +0000 (UTC), Bertie the Bunyip
wrote:

Big John wrote in
:

Help

I flew a 'Top Hat' four way trim switch for thousands of hours and

----clip----

Switches like that are illegal now. You have to have passive fail
systems on trims and autopilots nowadays.

Bertie

Big John wrote in
:

Bertie

I'm going to the "Wings over Houston" Air Show at Ellington this week
end. Besides getting some cockpit time in the P-40 and P-51, I'll talk
to some of the current Heavy Iron drivers, with birds on display,
about what the trim is on the birds newer than I flew. From past shows
expect to see at least the F-15, F-16, F-117 and also Navy jets, Blue
Angels, etc. Probably some Chinese Migs that were kept at Ellington.

Its 62 years since I flew the P-40 and 58 years since I flew the P-51
so need the cockpit time to refresh where all the controls, etc.,
were/are )


Have fun!

Ask 'em if they have any LeBlond valve springs while you're there.

Bertie

Bertie

Have you contacted Old Rinebeck Aerodrome on the Hudson north of NYC.
They have lots of WWI birds that fly and other old airplanes and
engines. They might have the springs or know where you can get
original or aftermarket?

Also I saw someplace in my wanderings in some publication that there
is a outfit that will make springs to your specs. Ask around and look
on Internet and you may find the company.

Want to say they specialized in springs for race car engines????? so
you might follow that trail.

I'm assuming you are not worried about getting a certified engine that
old. Aren't there some waivers for parts that are no longer available
and that you can make?

I'll ask this week end if it looks like anyone can give good info and
advise.

Wonder if our 51 driver from up north is going to get gas money and
come to Ellington?


The best

Big John

************************************************** ***********
On Sun, 30 Sep 2007 18:43:38 +0000 (UTC), Bertie the Bunyip
wrote:

Big John wrote in
:

Bertie

I'm going to the "Wings over Houston" Air Show at Ellington this week
end. Besides getting some cockpit time in the P-40 and P-51, I'll talk
to some of the current Heavy Iron drivers, with birds on display,
about what the trim is on the birds newer than I flew. From past shows
expect to see at least the F-15, F-16, F-117 and also Navy jets, Blue
Angels, etc. Probably some Chinese Migs that were kept at Ellington.

Its 62 years since I flew the P-40 and 58 years since I flew the P-51
so need the cockpit time to refresh where all the controls, etc.,
were/are )


Have fun!

Ask 'em if they have any LeBlond valve springs while you're there.

Bertie