Dual Trim Switches?

[Christopher Brian Colohan]

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 there: Why does the electric elevator trim have
two switches (both of which must be depressed) on the yoke instead of
one?

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

(Another question: 13 fuel drains? What were they thinking??? But I
am pretty sure the answer is "the lawyers designed that part, not the
engineers.")

[Bertie the Bunyip[_19_]]

Christopher Brian Colohan > wrote in
:

> 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 there: Why does the electric elevator trim have
> two switches (both of which must be depressed) on the yoke instead of
> one?
>
> The best theory I could come up with was "to avoid runaway trim if one
> switch stuck", but that is not very satisfying...

That's it. It's the one and only reason.



>
> Anyone know why?
>
> Chris
>
> (Another question: 13 fuel drains? What were they thinking??? But I
> am pretty sure the answer is "the lawyers designed that part, not the
> engineers.")
>

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

Bertie

[karl gruber[_1_]]

"Christopher Brian Colohan" > wrote in message
...
>
> (Another question: 13 fuel drains? What were they thinking??? But I
> am pretty sure the answer is "the lawyers designed that part, not the
> engineers.")

Cessna was offered the Monarch fuel tanks when the went back into
production. But, according to Bill Barton, Cessna never even acknowledged
the offer.

There are 13 drains because they NEED them. The Monarchs need only one, ALL
water is drainable, and they never leak. Cessna has particularly poor fuel
tank engineering.
http://www.sumpthis.com/imagescourtesyfaa/aircraftnumber17274599.htm

You should always test the trim switches according to the POH to prevent
runaway trim.

KG

[Robert M. Gary]

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 there: 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
>
> (Another question: 13 fuel drains? What were they thinking??? But I
> am pretty sure the answer is "the lawyers designed that part, not the
> engineers.")

No one really knows. Some believe that there is one for every lawsuit
someone brought against Cessna because they forgot to drain the tanks.
Few actually believe that Cessna designed the tanks to collect water
at that many points. In anycase, we just drain them all.

-Robert, CFII

[Robert M. Gary]

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

[Bertie the Bunyip[_19_]]

"Robert M. Gary" > wrote in news:1190997921.453348.284760@
22g2000hsm.googlegroups.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.
>

Kay.

Bertie

[Bob Gardner]

If the switches are in parallel and one of them develops an internal short
circuit, you will still have trim runway; if they are in series, both must
be closed simultaneously. Sounds like a dumb idea to me, but check with a
mechanic or radio shop for a knowledgeable answer...I'm not sure that I
would expect the Chief Pilot to be the expert on electrical questions.

Bob Gardner

"Christopher Brian Colohan" > wrote in message
...
> 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 there: Why does the electric elevator trim have
> two switches (both of which must be depressed) on the yoke instead of
> one?
>
> 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
>
> (Another question: 13 fuel drains? What were they thinking??? But I
> am pretty sure the answer is "the lawyers designed that part, not the
> engineers.")

[tjd]

On Sep 28, 1:30 pm, "Bob Gardner" > wrote:
> If the switches are in parallel and one of them develops an internal short
> circuit, you will still have trim runway; if they are in series, both must
> be closed simultaneously. Sounds like a dumb idea to me, but check with a
> mechanic or radio shop for a knowledgeable answer...I'm not sure that I
> would expect the Chief Pilot to be the expert on electrical questions.

Bob, I'm curious why you think it's a dumb idea? As far as I know
they are in series and it seems like a fairly clever idea to me since
it greatly reduces the possibility of a malfunctioning switch causing
runaway trim. I'm not sure if it's a solution looking for a problem
or if that's a legitimate concern, but given how simple and cheap it
is to implement, why not?

[gwengler]

On Sep 28, 1:30 pm, "Bob Gardner" > wrote:
> If the switches are in parallel and one of them develops an internal short
> circuit, you will still have trim runway; if they are in series, both must
> be closed simultaneously.

Bob,

I note that you say "If the switches..." and "if they are...", so you
are not really saying that they are. I always thought one switch
engages the trim motor and the other engages a clutch to actually have
the motor move the trim cable. Either swith alone will not do
anything.

Gerd
T182T

[Judah]

"Bob Gardner" > wrote in
:

> If the switches are in parallel and one of them develops an internal short
> circuit, you will still have trim runway; if they are in series, both must
> be closed simultaneously. Sounds like a dumb idea to me, but check with a
> mechanic or radio shop for a knowledgeable answer...I'm not sure that I
> would expect the Chief Pilot to be the expert on electrical questions.
>
> Bob Gardner

Although it's been a while since I flew a 172SP, IIRC, they're just series
switches. I don't even think it is the "one controls the clutch, the other
controls the motor" theory that a few people have responded with.

On the Arrows and Bo's in our club, the Electric Trim is a single toggle on
the yoke, and there is a cutoff switch on the panel to deal with runaway
trim...

It's not unusual for one to push the trim switch up or down and nothing
happens, but I can't recall a situation where the button got stuck in a
movement position. Still, I can see where there might be advantages to either
approach to this safety feature.

[Bertie the Bunyip[_19_]]

Bob Moore > wrote in
46.128:

> Bob Gardner wrote
>> If the switches are in parallel and one of them develops an internal
>> short circuit, you will still have trim runway; if they are in series,
>> both must be closed simultaneously. Sounds like a dumb idea to me, but
>> check with a mechanic or radio shop for a knowledgeable answer...I'm
>> not sure that I would expect the Chief Pilot to be the expert on
>> electrical questions.
>
> Bob...if they are anything like I flew in the Boeings, one switch
> powers the trim motor, and the second engages a drive clutch.

They're not the same. Actually, if you remember, if you got an out of
sequence operation of the two pickle switches (never flew the 70-, but the
others are lke this) you got the trim wheel brake to engage with a clatter.

Bertie

[Morgans[_2_]]

"Robert M. Gary" > wrote

> No one really knows. Some believe that there is one for every lawsuit
> someone brought against Cessna because they forgot to drain the tanks.
> Few actually believe that Cessna designed the tanks to collect water
> at that many points. In anycase, we just drain them all.

From the pictures provided (by a link) in an earlier post, it is obvious
(with the help of some added color agent) that there are, or could be, some
very big problems if the tank is not drained at all of the provided drains.

Everyone knows that the airplane is a group of compromises flying in close
formation. It seems as though the tank design is a _big_ compromise, for
some reason.

It is hard for me to understand how Cessna could come up with such a poor
design. I do realize that a wet tank has to have internal structures in
place, with weight and strength being two of the most important design
criteria, but it does seem like it should be possible to leave some pass
through areas to let gas and water flow freely from bay to bay.

It might have cost a little more, but when you are spending, what, over 200
AMU's to buy an airplane, should it not be possible to include some design
improvements that costs a little more, than take the easy way out with
nearly a dozen added (should be) unnecessary drains?

If a tank design like that is Cessna's normal way of dong things, I would
think Columbia's future owners have some genuine concerns.
--
Jim in NC

[Morgans[_2_]]

"Judah" > wrote

> It's not unusual for one to push the trim switch up or down and nothing
> happens, but I can't recall a situation where the button got stuck in a
> movement position.

Usually when a switch fails closed, the movement is not the issue. The
contacts weld themselves together, and it is possible for the switch to
still be moveable in either direction.
--
Jim in NC

[Bob Gardner]

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.

Bob

"tjd" > wrote in message
ups.com...
> On Sep 28, 1:30 pm, "Bob Gardner" > wrote:
>> If the switches are in parallel and one of them develops an internal
>> short
>> circuit, you will still have trim runway; if they are in series, both
>> must
>> be closed simultaneously. Sounds like a dumb idea to me, but check with a
>> mechanic or radio shop for a knowledgeable answer...I'm not sure that I
>> would expect the Chief Pilot to be the expert on electrical questions.
>
> Bob, I'm curious why you think it's a dumb idea? As far as I know
> they are in series and it seems like a fairly clever idea to me since
> it greatly reduces the possibility of a malfunctioning switch causing
> runaway trim. I'm not sure if it's a solution looking for a problem
> or if that's a legitimate concern, but given how simple and cheap it
> is to implement, why not?
>

[Bertie the Bunyip[_19_]]

Bob Moore > wrote in
6.128:

> Bertie the Bunyip wrote
>> They're not the same. Actually, if you remember, if you got an out of
>> sequence operation of the two pickle switches (never flew the 70-, but
>> the others are lke this) you got the trim wheel brake to engage with a
>> clatter.
>
> Nope! To get the brake to engage, the trim had to be moving in one
> direction and you had to be pulling/pushing the yoke in the other
> direction. One was never aware that there were two switches, they
> were mounted side by side in a space that one would normally find
> one larger switch.

That's right, but you could also get the brake to engage if the pickle
switches ****ed up. After all, it was runaway protection.
If you still have access to one, even a sim, if you push one one way and
the other the other way, the brake will engage.

I've stil got my 72/73 manuals lying around somewhere, though of course
they're pilot manuals and not engineering manuals and as you know thye
wrote the flight manuals like they were trying to tell a four year old what
to do (for some obscure reason ;) )

I'll look it up to be sure, though.

The 74, 75 and 76 had a hydraulic motor instead of an electric one so the
protection was a bit different, though it was still based upon both
switches being operated simultaneously, of course. No brake on those.

Bertie

[tjd]

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 picture:

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.

[Peter Clark]

On 28 Sep 2007 18:48:03 GMT, Bob Moore >
wrote:

>Bob Gardner wrote
>> If the switches are in parallel and one of them develops an internal
>> short circuit, you will still have trim runway; if they are in series,
>> both must be closed simultaneously. Sounds like a dumb idea to me, but
>> check with a mechanic or radio shop for a knowledgeable answer...I'm
>> not sure that I would expect the Chief Pilot to be the expert on
>> electrical questions.
>
>Bob...if they are anything like I flew in the Boeings, one switch
>powers the trim motor, and the second engages a drive clutch.
>Either one by itself will not change the trim. Of course, as you
>state, a series connection would also prevent a runaway trim.

Ding ding ding, we have a winner.

[Peter Clark]

On Fri, 28 Sep 2007 19:28:42 GMT, Judah > wrote:

>"Bob Gardner" > wrote in
:
>
>> If the switches are in parallel and one of them develops an internal short
>> circuit, you will still have trim runway; if they are in series, both must
>> be closed simultaneously. Sounds like a dumb idea to me, but check with a
>> mechanic or radio shop for a knowledgeable answer...I'm not sure that I
>> would expect the Chief Pilot to be the expert on electrical questions.
>>
>> Bob Gardner
>
>Although it's been a while since I flew a 172SP, IIRC, they're just series
>switches. I don't even think it is the "one controls the clutch, the other
>controls the motor" theory that a few people have responded with.

Look at the wiring diagram sometime. That's exactly how it's wired.

[R. Gardner]

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

Ron Gardner

"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
>

[Jay Honeck]

> It might have cost a little more, but when you are spending, what, over 200
> AMU's to buy an airplane, should it not be possible to include some design
> improvements that costs a little more, than take the easy way out with
> nearly a dozen added (should be) unnecessary drains?

They're not just unnecessary -- they're dangerous. That is 13
separate points of failure that should not be in that wing.

I've had several quick drains leak over the years -- one quite badly
-- now imagine 13 of them! All plumbing fittings, by their very
nature, will eventually leak. These will, too.

There's really no other way to put it: Cezzzna really screwed the
pooch with their wing design.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Bob Gardner]

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 picture:
>
> 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.
>

[Peter Dohm]

"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. :-)

[Big John]

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. :o)

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 :o(
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. :-)

[Big John]

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 there: 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

[Bertie the Bunyip[_19_]]

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
>
>
>

[Mxsmanic]

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 :o(
> 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.

[Bertie the Bunyip[_19_]]

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 :o(
>> 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

[Big John]

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 :o)

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

[Bertie the Bunyip[_19_]]

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 :o)
>

Have fun!

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

Bertie
>
>

[Big John]

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 :o)
>>
>
>Have fun!
>
>Ask 'em if they have any LeBlond valve springs while you're there.
>
>Bertie
>>
>>

[Bertie the Bunyip[_19_]]

Big John > wrote in
:

> 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?

I was only joking!
Actually, there is a guy making replica vale springs. I really ought to
buy some as spares, but they;re over $100 each!

It's one weakness of the LeBLond and attempts to substitue with
everything from O-200 to Chevvy springs were abject failures. One guy
who has a few airplanes with LeBlonds and Ken Royces finally bit the
bullet and had a large batch made.
>
> 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?



HEre's hoping! Surely everyone will throw in a couple of bucks just ot
hear it.

Was at an airshow a fe months ago that had a P-40 N doing a show. Looked
and sounded great and wa a nice change.


Bertie

[Big John]

Bertie

The "N" is what I flew.

If you had to hold on the ground very long even with cowel flaps open
coolent temp got hot no matter the idle RPM.

To prevent so many aborts due to an over temp they put a fire truck at
end of R/W. When you got to #1 if you were hot you motioned to the guy
in truck and he pulled a hose out and walked along leading edge of
wing and stuck hose in front of coolent radiator and turned water on.
You could see the temp go down it dissapated the temp so fast.

When you were in the green you motined him away and took runway and
rolled.

One time I was #1 and over temp. Motioned for water and the guy shook
his head and gave me a thumbs down which I took as no water left.

Was not about to abort so rolled. Just as I broke ground the Allison
quit :o( Pulled throttle back and caught. I must have flown 10 miles
on the deck gettng coolent temp down before I quit shaking and started
to climb.

Looking back, wonder why more of us didn't kill ourselves :o( Luck of
the Irish I guess???

Big John

************************************************** *****************8
Was at an airshow a few months ago that had a P-40 N doing a show.
Looked and sounded great and was a nice change.


Bertie

[B A R R Y]

On Sun, 30 Sep 2007 18:32:10 -0500, Big John >
wrote:
>
>Was not about to abort so rolled. Just as I broke ground the Allison
>quit :o( Pulled throttle back and caught. I must have flown 10 miles
>on the deck gettng coolent temp down before I quit shaking and started
>to climb.

Cool... <G>

Thanks for sharing that!

[Bertie the Bunyip[_19_]]

Big John > wrote in
:

> Bertie
>
> The "N" is what I flew.
>
> If you had to hold on the ground very long even with cowel flaps open
> coolent temp got hot no matter the idle RPM.
>
> To prevent so many aborts due to an over temp they put a fire truck at
> end of R/W. When you got to #1 if you were hot you motioned to the guy
> in truck and he pulled a hose out and walked along leading edge of
> wing and stuck hose in front of coolent radiator and turned water on.
> You could see the temp go down it dissapated the temp so fast.
>
> When you were in the green you motined him away and took runway and
> rolled.
>
> One time I was #1 and over temp. Motioned for water and the guy shook
> his head and gave me a thumbs down which I took as no water left.
>
> Was not about to abort so rolled. Just as I broke ground the Allison
> quit :o( Pulled throttle back and caught. I must have flown 10 miles
> on the deck gettng coolent temp down before I quit shaking and started
> to climb.
>
> Looking back, wonder why more of us didn't kill ourselves :o( Luck of
> the Irish I guess???



Wow!

The intake was the large scoop under th espinner, right? So he had to spray
agains the back of th eprop?

[Big John]

Bertie

They had some kind of a hook shape on end of hose (which looked like a
garden hose) and hooked it on the lip of the scoop so water just went
down scoop. Nothing into prop.

This was of course in the summer time. Cooler Wx it was not needed.

In a prior posting there was comments on checking out in 51. Prior to
the 40 checkout, made 6-8 back seat landings in a T-6. Had to do that
prior to going solo. Probably a good technique for anyone checking out
in 40 or 51 today.

One more tonight. I spent a year as a AF Exchange Pilot with VF-23 a
F2H3 Navy Tail hook Sq.

Sitting in ready room and Exec came in and said who doesn't have their
flying time (4 hours for pay) for the month. I put my hand up and he
said ok you'll fly the Banshee tomorrow. I said is there a Pilots Hand
Book around and he said there must be and a search took place until
one was found. It was late in day so I took home and read after
dinner. Next morning a bird number was posted by my name and I got my
flying gear and went out to line and the crew chief talked me through
the pre flight. I then got in and he talked me through the starting of
both engines.

Took off and flew about an hour and a half feeling bird out (flew like
a T-33) and came in and landed (piece of cake). Taxied in to Sq
parking ramp and line chief met me and started making funny motions
with is arms. I stopped taxiing and he then picked up a chock and ran
up to bird and threw it under the wing. He then gave me the sig to
shut down which I did.

The crew chief came up kick in steps to cockpit and said the gear had
almost collapsed and the chock was in the stiff knee preventing it
from retracting. Got out and looked and strut was cocked abut 30
degrees.

After they inspected it they found that someone had left a wrench in
the wing section and it had shorted out the retract relay. My
introduction to Navy birds :o)


I need to go silent again. Let you and Dudley carry the load :o)

Take care.

Big John
********************************

On Sun, 30 Sep 2007 23:58:01 +0000 (UTC), Bertie the Bunyip >
wrote:

----clip----

Wow!

The intake was the large scoop under th spinner, right? So he had to
spray against the back of th prop?

[Neil Gould]

Recently, Jay Honeck > posted:

>> It might have cost a little more, but when you are spending, what,
>> over 200 AMU's to buy an airplane, should it not be possible to
>> include some design improvements that costs a little more, than take
>> the easy way out with nearly a dozen added (should be) unnecessary
>> drains?
>
> They're not just unnecessary -- they're dangerous. That is 13
> separate points of failure that should not be in that wing.
>
> I've had several quick drains leak over the years -- one quite badly
> -- now imagine 13 of them! All plumbing fittings, by their very
> nature, will eventually leak. These will, too.
>
> There's really no other way to put it: Cezzzna really screwed the
> pooch with their wing design.
>
Our club's 172 SP had those drain points. As I recall, only 10 of them
were in the wing, with the other 3 on the cowling. I can only imagine the
pretzel fuel flow that made that many drains necessary. I agree with the
OP that suggested that Cessna's lawyers designed that aspect of their
planes.

Neil

[Peter Clark]

On Tue, 02 Oct 2007 09:56:00 GMT, "Neil Gould"
> wrote:

>Recently, Jay Honeck > posted:
>
>>> It might have cost a little more, but when you are spending, what,
>>> over 200 AMU's to buy an airplane, should it not be possible to
>>> include some design improvements that costs a little more, than take
>>> the easy way out with nearly a dozen added (should be) unnecessary
>>> drains?
>>
>> They're not just unnecessary -- they're dangerous. That is 13
>> separate points of failure that should not be in that wing.
>>
>> I've had several quick drains leak over the years -- one quite badly
>> -- now imagine 13 of them! All plumbing fittings, by their very
>> nature, will eventually leak. These will, too.
>>
>> There's really no other way to put it: Cezzzna really screwed the
>> pooch with their wing design.
>>
>Our club's 172 SP had those drain points. As I recall, only 10 of them
>were in the wing, with the other 3 on the cowling. I can only imagine the
>pretzel fuel flow that made that many drains necessary. I agree with the
>OP that suggested that Cessna's lawyers designed that aspect of their
>planes.

AIUI, it's because they're bladders and folds on the bottom could
gather water. If it was a wet wing they wouldn't need as many, like
the older models.

[Morgans[_2_]]

"Peter Clark" > wrote

> AIUI, it's because they're bladders and folds on the bottom could
> gather water. If it was a wet wing they wouldn't need as many, like
> the older models.

But they are wet wings, in question, AFAIK. Did you see the picture that
someone posted in a link? Each rib was forming a little damn that could
possibly trap a small amount of water, so a drain was installed to drain any
trapped water, in each bay.
--
Jim in NC

[Maxwell]

For what it's worth.

When I first checked out in an SP, the CFI told me Cessna had been
sucessfully sued when a pilot argued the tanks could not be sumped correctly
unless the aircraft was parked perfectly level.

Now you can drain the lowest point in the tank, no mater how or where you
park your SP.

[Peter Clark]

On Wed, 3 Oct 2007 17:50:35 -0400, "Morgans"
> wrote:

>
>"Peter Clark" > wrote
>
>> AIUI, it's because they're bladders and folds on the bottom could
>> gather water. If it was a wet wing they wouldn't need as many, like
>> the older models.
>
>But they are wet wings, in question, AFAIK. Did you see the picture that
>someone posted in a link? Each rib was forming a little damn that could
>possibly trap a small amount of water, so a drain was installed to drain any
>trapped water, in each bay.

The airfraft in that link is a 1982 172P, not a new (post-restart)
172R/S, 182T, etc with bladders in the wings. It's been a while (and
the only older model 172 I've flown is an M model) but I thought the
pre-restart aircraft only had 2 sumps at the wing root and a stariner
drain pull-thingie in the oil door?

You have the same issue as that 172P with the Malibu. Since they're
wet wings, the only path water has to flow underneath the ribs is the
minute clearance between the ribs and the lower wing skin. At least
the Malibu has some pretty significant dihedral. But if the aircraft
hasn't been sitting for (I'm not going to try and test it) some large
number of hours, unless you're pumping in almost pure water I doubt a
significant sample of water would show up in the 1 sump at the wing
root from fueling during quick (1hr or less) refueling stops during
multi-leg flights.

[JGalban via AviationKB.com]

Maxwell wrote:
>For what it's worth.
>
>When I first checked out in an SP, the CFI told me Cessna had been
>sucessfully sued when a pilot argued the tanks could not be sumped correctly
>unless the aircraft was parked perfectly level.
>
>Now you can drain the lowest point in the tank, no mater how or where you
>park your SP.

I would tend to doubt that version of events. The 13 drain points were
introduced when Cessna restarted production on the redesigned 172R back in
'96. The drains were in the new version from the start, so I doubt Cessna
could have been sued. Also, we probably would have heard about it here.

Previous versions of the 172 ('84/'85) had wing tanks with no obstructions
in the bottoms. The new version had wet wings, which is what prompted the
installation of drains outboard of each rib in the tank area.

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

--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums.aspx/aviation/200710/1

[Morgans[_2_]]

"JGalban> wrote

> Previous versions of the 172 ('84/'85) had wing tanks with no
> obstructions
> in the bottoms. The new version had wet wings, which is what prompted the
> installation of drains outboard of each rib in the tank area.

And all of those extra drains could have easily been eliminated if the
engineers would have done a hours worth of work redesigning the ribs to
enlarge or add crossover points in the ribs, so all of the water could get
to the lowest point in the tank.

This has to be an example of why things are screwed up in the industry,
don't you think?
--
Jim in NC

[Peter Clark]

On Thu, 4 Oct 2007 21:38:15 -0400, "Morgans"
> wrote:

>
>"JGalban> wrote
>
>> Previous versions of the 172 ('84/'85) had wing tanks with no
>> obstructions
>> in the bottoms. The new version had wet wings, which is what prompted the
>> installation of drains outboard of each rib in the tank area.
>
>And all of those extra drains could have easily been eliminated if the
>engineers would have done a hours worth of work redesigning the ribs to
>enlarge or add crossover points in the ribs, so all of the water could get
>to the lowest point in the tank.
>
>This has to be an example of why things are screwed up in the industry,
>don't you think?

The newer (post-restart) aircraft are sealed bladders, not wet wing,
therefore you can't just let the water seep through the ribs.

[Scott Skylane]

Peter Clark wrote:


>
> The newer (post-restart) aircraft are sealed bladders, not wet wing,
> therefore you can't just let the water seep through the ribs.

Peter, your information is incorrect. I'm looking at the Cessna Parts
Catalog for the new 172R, and 182S models. They most definitely employ
wet wing fuel bays, not bladders.

Happy Flying!
Scott Skylane

[Peter Clark]

On Sat, 06 Oct 2007 12:04:50 -0800, Scott Skylane
> wrote:

>Peter Clark wrote:
>
>
>>
>> The newer (post-restart) aircraft are sealed bladders, not wet wing,
>> therefore you can't just let the water seep through the ribs.
>
>Peter, your information is incorrect. I'm looking at the Cessna Parts
>Catalog for the new 172R, and 182S models. They most definitely employ
>wet wing fuel bays, not bladders.

Interesting. I don't have my maintenance manual handy, but a quick
Google pulled this up from Cessna's website:

"The 182E also featured electrically-operated “Para-Lift” flaps,
neoprene rubber fuel bladders holding 65 gallons total, new stronger
main landing gear/fuselage attachment and improved nose wheel
steering."

(
http://www.cessna.com/news/article.chtml?ID=nip1NqeOecOXACXLryEnkWjiv3dgI6rca 8swXLJEsBa4kfBxm4
)

I wonder why they would have gone back to sealed wet-wing when they
had bladders in there years ago. I wonder where I got that the new
ones still had bladders.

[Morgans[_2_]]

"Peter Clark" > wrote

> "The 182E also featured electrically-operated "Para-Lift" flaps,
> neoprene rubber fuel bladders holding 65 gallons total, new stronger
> main landing gear/fuselage attachment and improved nose wheel
> steering."

Looking at the 172R specs on the Cessna web pages, the wing tanks are listed
as Integral fuel tanks, 53 gallons useable, 5 quick drains per wing. No
fuel bladders in this model, it would appear.
--
Jim in NC

[Scott Skylane]

Peter Clark wrote:
/snip/
>
> I wonder why they would have gone back to sealed wet-wing when they
> had bladders in there years ago. I wonder where I got that the new
> ones still had bladders.

Peter,

They didn't "go back" to a wet wing, it was an engineering development
first used in the Cessna singles in the early eighties. Originally,
172's had removable aluminum tanks in the wing bays, and 182's used
bladders.

Integral tanks ("wet wings") are lighter, easier to build/assemble, have
greater fuel capacity, and if done properly, require less mainenance in
the long run.

Happy Flying!
Scott Skylane