Trim not set... can't take off?

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dallas

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I have an aircraft that when the trim is just left at zero and not set to
take off (+55), it will not leave the ground at any speed - even if you pull
back on the yoke all the way.

Is this possible in real life? Are there aircraft that won't take off if
you don't set the trim first? It just doesn't seem likely to me.


Dallas
 
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Dallas <Cybnorm@spam_me_not.Hotmail.Com> wrote:

> I have an aircraft that when the trim is just left at zero and not set to
> take off (+55), it will not leave the ground at any speed - even if you pull
> back on the yoke all the way.
>
> Is this possible in real life? Are there aircraft that won't take off if
> you don't set the trim first? It just doesn't seem likely to me.

Regarding the smaller aircraft, if you had the trim at the opposite stops,
you would have a difficult time overcoming the force being applied to the
yoke by the elevator-down trim position as the aircraft accelerated.

The scenario is not that you would be able to pull all the way back but
nothing would happen; instead, you would have a difficult time pulling
back, and this would result in a much longer take-off roll. The lack of
real force on the yoke is one of the major limitations of the sim, at least
in my opinion.


--
Peter













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GREGORY

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On Tue, 15 Mar 2005 01:17:35 GMT, "Dallas"
<Cybnorm@spam_me_not.Hotmail.Com> brought the following to our
attention:

>
>I have an aircraft that when the trim is just left at zero and not set to
>take off (+55), it will not leave the ground at any speed - even if you pull
>back on the yoke all the way.
>
>Is this possible in real life? Are there aircraft that won't take off if
>you don't set the trim first? It just doesn't seem likely to me.
>
>

Dallas.. surprised you ask. :)

Isn't there a thing called `elevator authority'?


Have a look at the pic. Which is the elevator and which is
the STAB trim? Now you see!!

http://home.comcast.net/~flightsim/727_tail.jpg


someone else might want to comment with more certainty.


-Gregory
 
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Bob

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pr wrote:

> Dallas <Cybnorm@spam_me_not.Hotmail.Com> wrote:
>
>
>>I have an aircraft that when the trim is just left at zero and not set to
>>take off (+55), it will not leave the ground at any speed - even if you pull
>>back on the yoke all the way.
>>
>>Is this possible in real life? Are there aircraft that won't take off if
>>you don't set the trim first? It just doesn't seem likely to me.
>
>
> Regarding the smaller aircraft, if you had the trim at the opposite stops,
> you would have a difficult time overcoming the force being applied to the
> yoke by the elevator-down trim position as the aircraft accelerated.
>
> The scenario is not that you would be able to pull all the way back but
> nothing would happen; instead, you would have a difficult time pulling
> back, and this would result in a much longer take-off roll. The lack of
> real force on the yoke is one of the major limitations of the sim, at least
> in my opinion.
>
>

I was so lazy back that I rotated and went right to the trim wheel,
spinning it like mad until the pressure on the yoke stabilized. And it
impressed the heck outa the non-pilots on board. They thought it was
quite busy and hard to take-off.

--

boB

U.S. Army Aviation (retired)
Central Texas - 5NM West of Gray Army Airfield (KGRK)
 
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boB <akitaREMOVECAPS77@excite.Icom> wrote:

> I was so lazy back that I rotated and went right to the trim wheel,
> spinning it like mad until the pressure on the yoke stabilized. And it
> impressed the heck outa the non-pilots on board.

Lazy? That's how I was taught. Pitch, power, trim.

--
Peter













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On Tue, 15 Mar 2005 01:17:35 GMT, "Dallas"
<Cybnorm@spam_me_not.Hotmail.Com> wrote:

>
>I have an aircraft that when the trim is just left at zero and not set to
>take off (+55), it will not leave the ground at any speed - even if you pull
>back on the yoke all the way.
>
>Is this possible in real life? Are there aircraft that won't take off if
>you don't set the trim first? It just doesn't seem likely to me.
>
>
>Dallas
>

You get the trim out of whack in the wrong direction ( nose up) and
you may wind up doing a face plant into the runway, after a departure
stall. Nothing to screw around with.

Bob
 
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Bob Cordone <nospam@mindspring.com> wrote:

> You get the trim out of whack in the wrong direction ( nose up) and
> you may wind up doing a face plant into the runway, after a departure
> stall. Nothing to screw around with.

Yep, the most memorable trim accident to me in recent memory was the case
of the new Cessna 182 somewhere in the UK. The pilot and his wife were
taking the aircraft up for a flight when he mistakenly hit the AP engage
switch with his knuckle as he slid the throttle forward for the run-up.

Unbeknownst to him, the AP commanded a maximum elevator up position. When
the aircraft rolled down the runway for takeoff, it lifted off quite
prematurely and climbed at about a 60 degree nose-up attitude for a few
seconds before stalling and nosing over into the runway, killing both
occupants.

--
Peter













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"pr" <nope@nospam.com> wrote in message
news:k89vwz11vcfx$.dlg@ID-259643.user.individual.net...
> Bob Cordone <nospam@mindspring.com> wrote:
>
>> You get the trim out of whack in the wrong direction ( nose up) and
>> you may wind up doing a face plant into the runway, after a departure
>> stall. Nothing to screw around with.
>
> Yep, the most memorable trim accident to me in recent memory was the case
> of the new Cessna 182 somewhere in the UK. The pilot and his wife were
> taking the aircraft up for a flight when he mistakenly hit the AP engage
> switch with his knuckle as he slid the throttle forward for the run-up.
>
> Unbeknownst to him, the AP commanded a maximum elevator up position. When
> the aircraft rolled down the runway for takeoff, it lifted off quite
> prematurely and climbed at about a 60 degree nose-up attitude for a few
> seconds before stalling and nosing over into the runway, killing both
> occupants.
>
> --
> Peter
>

(IIRC) That very situation has initiated an AD on the CAP140 auto pilot.
The change makes you have to hold the engage button on the face for three
seconds before it will activate.

Jay Beckman
PP-ASEL / Sim Pilot Too
Chandler, AZ
 
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Bob

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pr wrote:

> boB <akitaREMOVECAPS77@excite.Icom> wrote:
>
>
>>I was so lazy back that I rotated and went right to the trim wheel,
>>spinning it like mad until the pressure on the yoke stabilized. And it
>>impressed the heck outa the non-pilots on board.
>
>
> Lazy? That's how I was taught. Pitch, power, trim.
>


Maybe that's why I did it that way... :)

--

boB

U.S. Army Aviation (retired)
Central Texas - 5NM West of Gray Army Airfield (KGRK)
 
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dallas

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"pr"
> you would have a difficult time pulling
> back, and this would result in a much longer take-off roll.

I'm still looking for an answer as to the impossibility of taking off with
an improper setting.

The specific aircraft I'm talking about is the Aeroworx King Air... if you
skip the checklist and don't set the trim to "take off" you can find
yourself heading down the runway at 110 kts spinning the trim wheel as fast
as you can with the runway rapidly running out. If you're not fast enough,
you wind up going off road in a three wheeler. :)

I've gotta wonder how realistic that is...

Dallas
 
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GREGORY

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On Tue, 15 Mar 2005 05:38:22 GMT, "Dallas"
<Cybnorm@spam_me_not.Hotmail.Com> brought the following to our
attention:

>
>"Gregory"
>> Isn't there a thing called `elevator authority'?
>
>Yeah, it's a New York City agency. :)
>

doo00-oh! that must be the guys who handle the gold bullion..

No really.. set the trim properly or you could be in for a scary,
even `worm burner' ride.


>
>Dallas
>
 
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On Mon, 14 Mar 2005 21:56:01 -0500, pr <nope@nospam.com> wrote:

>Bob Cordone <nospam@mindspring.com> wrote:
>
>> You get the trim out of whack in the wrong direction ( nose up) and
>> you may wind up doing a face plant into the runway, after a departure
>> stall. Nothing to screw around with.
>
>Yep, the most memorable trim accident to me in recent memory was the case
>of the new Cessna 182 somewhere in the UK. The pilot and his wife were
>taking the aircraft up for a flight when he mistakenly hit the AP engage
>switch with his knuckle as he slid the throttle forward for the run-up.
>
>Unbeknownst to him, the AP commanded a maximum elevator up position. When
>the aircraft rolled down the runway for takeoff, it lifted off quite
>prematurely and climbed at about a 60 degree nose-up attitude for a few
>seconds before stalling and nosing over into the runway, killing both
>occupants.

This is sort of like what I did with my RAS Scout the other day. I
accidentally turned on the AP during preflight , with the altitude set
at zero. I was taking off from a small airfield in Misty Fjords with
a tree line at the end. I got to rotation speed, and pulled the yoke
back, and no rotation( must be what it feels like for people that take
off with the gust lock still in place) . Now I am doing about 90 knots
and I should have been at 100 feet and climbing already, and slammed
into the trees at the end of the runway. From now on ,, I check the AP
to make sure it is not engaged.

Bob
 
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GREGORY

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On Thu, 17 Mar 2005 17:44:39 GMT, "Dallas"
<Cybnorm@spam_me_not.Hotmail.Com> brought the following to attention:

>
>"Gregory"
>> Hey Dallas.. looks like the `authority' is doing it's work today!!
>> http://mywebpages.comcast.net/constitution/MAR17.gif
>
>
>Yeah, the rightpondarians better buy those US add-on now before
>they become expensive again.
>
>Dallas
>

LOL!! ..are we having fun today or what ?

with ALL this going on.. what should Americans stay focus on??

http://mywebpages.comcast.net/constitution/ball_game.gif


the BALL GAME.. of course. :)


and don't forget shopping malls of the ladies!


-G
 
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Dallas <Cybnorm@spam_me_not.Hotmail.Com> wrote:

> I'm still looking for an answer as to the impossibility of taking off with
> an improper setting.

OK, put it this way: I *believe* that a grossly incorrect trim setting
could prevent takeoff.

How I arrive at this conclusion is the following: Adverse trim would
significantly raise the amount of force required to pull back on the
stick/yoke as the aircraft accelerated. How much force? I couldn't say
with certainty but I recall the AP/nose-up C182 crash-on-takeoff
investigative report mentioned that somewhere around 80 lbs of force would
have been required to overcome the fully trimmed nose-up yoke.

If the pilot were unable to overcome the force on the stick/yoke in a fully
nose-down trim setting, then the elevator would remain is a strong
nose-down position. With the downward force on the nose of the aircraft,
the angle of attack would never get high enough to create the lift needed
to overcome gravity, at least with regards to the distance of the average
runway.

As someone else pointed out in this thread, this situation would most
likely be similar to the accidents where pilots failed to remove the gust
lock, which locked the elevator in a nose-down position, and the aircraft
accelerated off the end of the runway while the pilot tried in vain to
remove the gust lock.

In the sim, of course, these forces cannot be realistically applied to your
yoke/joystick so it feels to you that you are pulling it effortlessly back.
This is giving you the illusion that you are indeed applying nose-up
elevator against this trim setting when in fact you are not.

--
Peter













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dallas

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"pr"
> investigative report mentioned that somewhere around 80 lbs of force would
> have been required to overcome the fully trimmed nose-up yoke.

Thanks for the perspective. I guess the answer is that the sim can not
duplicate the real world in this regard so it becomes an apples/oranges
thing. But impressively, the sim won't allow take off so it's not that far
from reality.

Dallas
 
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Of couirse IRL one of the pre-flight checks is to move the stick in all
directions and observe the ailerons ,elevators and rudder so that you can
identify visually as well as by feel that this cannot happen.


Quilly
 
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Quilljar <wykehill-flightsim@yahoo.co.uk> wrote:

> Of couirse IRL one of the pre-flight checks is to move the stick in all
> directions and observe the ailerons ,elevators and rudder so that you can
> identify visually as well as by feel that this cannot happen.

That's certainly true to catch a previously missed gust lock, but that
won't catch an incorrect trim setting.

In the small aircraft, one check is for the pilot to place the trim
wheel(s) in the neutral position, then on the walk-around, observe the trim
tab in relation to the elevator, aileron, and/or rudder, as the case may
be.

--
Peter













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On Sun, 20 Mar 2005 07:51:15 -0000, "Quilljar"
<wykehill-flightsim@yahoo.co.uk> wrote:

>Of couirse IRL one of the pre-flight checks is to move the stick in all
>directions and observe the ailerons ,elevators and rudder so that you can
>identify visually as well as by feel that this cannot happen.
>
>
>Quilly
>

Controls Free and Correct has nothing to do with takeoff trim setting
which is another item on the pre-takeoff checklist

Bob
 
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>
> Controls Free and Correct has nothing to do with takeoff trim setting
> which is another item on the pre-takeoff checklist
>
> Bob


No wonder I kept crashing :-(


--
Cheers,

Quilly
 
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