limit of trim = limit of travel?

On 2008-04-28, Stealth Pilot wrote:
$300 ????????????

the microswitch in my Tailwind cost $1.25 from Tandy. it is held in
with tape to make a jamb fit.
been working perfectly for 300 hours flying.

That's the difference between a certified aircraft (the Cessna) and an
experimental/amateur built (where you don't have to use approved parts,
just a part fit for purpose).

--
From the sunny Isle of Man.
Yes, the Reply-To email address is valid.

On Apr 28, 9:36 am, Stealth Pilot
wrote:

$300 ????????????

the microswitch in my Tailwind cost $1.25 from Tandy. it is held in
with tape to make a jamb fit.
been working perfectly for 300 hours flying.

Stealth Pilot

Works for a Tailwind, a homebuilt. Ain't legal in a certified
airplane, since the regs demand that the parts as listed in the
manufacturer's parts manual be used, and they know that, so they
charge lots for them.
So that's why my own airplane is a homebuilt.

Dan

"Dylan Smith" wrote in message
...
On 2008-04-28, Stealth Pilot wrote:
$300 ????????????

the microswitch in my Tailwind cost $1.25 from Tandy. it is held in
with tape to make a jamb fit.
been working perfectly for 300 hours flying.

That's the difference between a certified aircraft (the Cessna) and an
experimental/amateur built (where you don't have to use approved parts,
just a part fit for purpose).

--
From the sunny Isle of Man.
Yes, the Reply-To email address is valid.

This is an interesting issue, and the real answer is not necessarily
intuitive. In a type certified aircraft, the switch would need to be have
appropriate paperwork with a chain of custody attesting that it meets the
appropriate standards; and may need to be installed by an airframe mechanic.

I have been away from that industry for about twenty years, so some of the
regulations have changed, and was a radio repairman (rather than a mechanic)
at the time. However, for anyone operating a type certified aircraft, who
really wants to know the "straight and skinny" on this sort of issue, the
place to start in the USA is your local FSDO--before you do anything to the
aircraft. Ask for the Safety Program Manager for Airworthiness and he
should be able to point you to the correct office and/or litterature.

The point is that a common electrical part probably does not need to come
from the airframe manufacturer; but it is not "free stock" either. However,
don't be surprised if the airframe manufacturer turns out to be the best and
most economical source--when I was a radio repairman, the avionics
manufacturers were frequently the best and most economical sources of
standard parts for their equipment.

Peter

On Mon, 28 Apr 2008 11:43:49 -0400, "Peter Dohm"
wrote:

"Stealth Pilot" wrote in message
.. .
On Sat, 26 Apr 2008 10:09:16 -0800, Scott Skylane
wrote:

Stealth Pilot wrote:
/snip/
trim has nothing to do with the movement limits on control surfaces.

/snip/

Stealth,

This is not universally true. On the Douglas DC-6, for instance,
elevator "up" travel is limited by the elevator trim position. Dialing
in the last 5 degrees of nose up trim allows an extra 3 degrees of
elevator "up" travel. This was done to limit elevator "up" movement
with aft CG loading conditions.

Happy Flying!
Scott Skylane

ok you successfully cite the one instance possibly :-) I defer to your
knowledge of the obscure.

stops of the type I mentioned are a mandated requirement in my country
for the environment I play in.

Stealth Pilot

Not nearly so obscure as you sugest. Aircraft with a fully trimming
stabilizer have a result result of adding to the effective elevator
authority--examples are the Piper Cub and all of the "straight tail"
Mooneys.

Peter


ermmmm. trim has nothing to do with the control surface stops. they
are fixed to the airframe and work as their name suggests.

Stealth Pilot

"Stealth Pilot" wrote in message
...
On Mon, 28 Apr 2008 11:43:49 -0400, "Peter Dohm"
wrote:

"Stealth Pilot" wrote in message
. ..
On Sat, 26 Apr 2008 10:09:16 -0800, Scott Skylane
wrote:

Stealth Pilot wrote:
/snip/
trim has nothing to do with the movement limits on control surfaces.

/snip/

Stealth,

This is not universally true. On the Douglas DC-6, for instance,
elevator "up" travel is limited by the elevator trim position. Dialing
in the last 5 degrees of nose up trim allows an extra 3 degrees of
elevator "up" travel. This was done to limit elevator "up" movement
with aft CG loading conditions.

Happy Flying!
Scott Skylane

ok you successfully cite the one instance possibly :-) I defer to your
knowledge of the obscure.

stops of the type I mentioned are a mandated requirement in my country
for the environment I play in.

Stealth Pilot

Not nearly so obscure as you sugest. Aircraft with a fully trimming
stabilizer have a result result of adding to the effective elevator
authority--examples are the Piper Cub and all of the "straight tail"
Mooneys.

Peter


ermmmm. trim has nothing to do with the control surface stops. they
are fixed to the airframe and work as their name suggests.

Stealth Pilot

OK, I was thinking of the effect rather than the mechanism of changing the
limit of travel relative to a fixed stabilizer.

Peter

Peter Dohm writes:

... when I was a radio repairman, the avionics
manufacturers were frequently the best and most economical sources of
standard parts for their equipment.

So how did the other sources (if there were any) stay in business?

On Apr 30, 12:44*am, "Peter Dohm" wrote:
"Stealth Pilot" wrote in message

...





On Mon, 28 Apr 2008 11:43:49 -0400, "Peter Dohm"
wrote:

"Stealth Pilot" wrote in message
. ..
On Sat, 26 Apr 2008 10:09:16 -0800, Scott Skylane
wrote:

Stealth Pilot wrote:
/snip/
trim has nothing to do with the movement limits on control surfaces.

/snip/

Stealth,

This is not universally true. *On the Douglas DC-6, for instance,
elevator "up" travel is limited by the elevator trim position. *Dialing
in the last 5 degrees of nose up trim allows an extra 3 degrees of
elevator "up" travel. *This was done to limit elevator "up" movement
with aft CG loading conditions.

Happy Flying!
Scott Skylane

ok you successfully cite the one instance possibly :-) I defer to your
knowledge of the obscure.

stops of the type I mentioned are a mandated requirement in my country
for the environment I play in.

Stealth Pilot

Not nearly so obscure as you sugest. *Aircraft with a fully trimming
stabilizer have a result result of adding to the effective elevator
authority--examples are the Piper Cub and all of the "straight tail"
Mooneys.

Peter

ermmmm. trim has nothing to do with the control surface stops. they
are fixed to the airframe and work as their name suggests.

Stealth Pilot

OK, I was thinking of the effect rather than the mechanism of changing the
limit of travel relative to a fixed stabilizer.


I don't follow this. The trim surface operates in the opposite
direction to the trimmed surface and takes area away from it. Explain
please?

Cheers

"WingFlaps" wrote in message
...
On Apr 30, 12:44 am, "Peter Dohm" wrote:
"Stealth Pilot" wrote in message

...





On Mon, 28 Apr 2008 11:43:49 -0400, "Peter Dohm"
wrote:

"Stealth Pilot" wrote in message
. ..
On Sat, 26 Apr 2008 10:09:16 -0800, Scott Skylane
wrote:

Stealth Pilot wrote:
/snip/
trim has nothing to do with the movement limits on control surfaces.

/snip/

Stealth,

This is not universally true. On the Douglas DC-6, for instance,
elevator "up" travel is limited by the elevator trim position. Dialing
in the last 5 degrees of nose up trim allows an extra 3 degrees of
elevator "up" travel. This was done to limit elevator "up" movement
with aft CG loading conditions.

Happy Flying!
Scott Skylane

ok you successfully cite the one instance possibly :-) I defer to your
knowledge of the obscure.

stops of the type I mentioned are a mandated requirement in my country
for the environment I play in.

Stealth Pilot

Not nearly so obscure as you sugest. Aircraft with a fully trimming
stabilizer have a result result of adding to the effective elevator
authority--examples are the Piper Cub and all of the "straight tail"
Mooneys.

Peter

ermmmm. trim has nothing to do with the control surface stops. they
are fixed to the airframe and work as their name suggests.

Stealth Pilot

OK, I was thinking of the effect rather than the mechanism of changing the
limit of travel relative to a fixed stabilizer.


I don't follow this. The trim surface operates in the opposite
direction to the trimmed surface and takes area away from it. Explain
please?

Cheers

There was a brief discussion of elevator trim systems, the such that the
elevator trim setting also modified the stop/limit setting of the elevator.
I mentioned the case of the fully trimmng stabilizer, which also has
aerodynamic the effect of modifying the effective limit of the
elevator--even though the mechanical limit relative to the horizontal
stabilizer would typically remain unchanged. However that is a different
type of control system, just as a fully flying stabilizer (a/k/a stabilator)
is a third type.

I presume that there are other aircraft, beside the DC-6/DC-7 already
mentioned, on which the trim setting directly modifies the mechanical limits
of the elevator control; but the issue appears to be beyond the research
that my present curiosity can justify--and, in that regard, it appears that
I am not alone.

Peter

On Apr 29, 2:24 pm, WingFlaps wrote:

I don't follow this. The trim surface operates in the opposite
direction to the trimmed surface and takes area away from it. Explain
please?

Cheers

The trim tab generates a force that moves the trailing edge of
the control surface. So if you trim nose-up, you'll be moving the tab
downward, where it forces the elevator up. Next time you fly an
airplane with an elevator trim tab, like a Cessna, hold the yoke back
so you can see the trim tab, and roll in nose-up trim and see which
direction the tab moves.
See this:

http://en.wikipedia.org/wiki/Trim_tab

An excerpt:
"When a trim tab is employed, it is moved into the slipstream
opposite to the control surface's desired deflection. For example, in
order to trim an elevator to hold the nose down, the elevator's trim
tab will actually rise up into the slipstream. The increased pressure
on top of the trim tab surface caused by raising it will then deflect
the entire elevator slab down slightly, causing the tail to rise and
the aircraft's nose to move down."

Or page 169 of this:
http://books.google.ca/books?id=C8ZU...1vTlVZUY&hl=en

Dan

"WingFlaps" wrote in message
...

I don't follow this. The trim surface operates in the opposite
direction to the trimmed surface and takes area away from it. Explain
please?

Cheers

Sorry, I misread the question and answered mainly based upon the location in
the thread.

You are correct that some effective area is taken away, but the amount of
"lost" area is small and easily taken into account in the design--whereas
the reduction of pilot workload is great. Also, under normal conditions,
the limitation on elevator authority is the setting of the mechanical stop
rather than the area.

Peter