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chris Sinfield
Joined: 28 Nov 2006
Posts: 270
Location: Sydney Australia
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 Posted: Thu Feb 28, 2008 2:30 am Post subject: what if? elevator trim tab runaway |
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Q. for those out flying their XL's.
With the large elevator trim tab, if it was deflected full one way up or down, is it still controllable? I am fitting the Ray Allen Trim system and thinking about if one switches sticks.
I may fit a CB to the trim power line and pull it to stop the trim run away if required, rather than hide it with a fuse. What do others think?
Chris
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DaveG601XL
Joined: 27 Oct 2006
Posts: 351
Location: Cincinnati, Oh
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| Posted: Thu Feb 28, 2008 3:39 am Post subject: Re: what if? elevator trim tab runaway |
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Chris,
That is what I did. I have few CB's and trim is one of them for the very reason that I could pull it if desired.
Good luck,
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David Gallagher
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davgray(at)sbcglobal.net
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| Posted: Thu Feb 28, 2008 4:22 am Post subject: what if? elevator trim tab runaway |
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Chris
I have the full span left side elevator trim tab. When I get ham handed I
sometimes inadvertently activate the trim switches on the top of the control
stick. It will get your attention but it is still controllable. Same for
the aileron trim.
I have been at full deflection. The first time it happened it took 10
seconds to diagnose what was causing it.
At normal flight speed it has the most authority. At pattern speeds I need
to increase the trim setting on the aileron.
Time for full deflection is about 3 seconds. By the time you notice it, it
will be at full deployment so pulling a fuse wouldn't help. It will take
power to reverse the setting. I think if it happened it would be an
irritation. The controls are normally very light.
Gary Ray 601XL, 64 hrs TT
davgray(at)sbcglobal.net
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Al Hays
Joined: 01 Oct 2007
Posts: 42
Location: Gore, VA
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| Posted: Thu Feb 28, 2008 5:14 am Post subject: what if? elevator trim tab runaway |
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Listers,
FWTW, it seems to me that what might be no more than an irritation
under most conditions could easily become one distraction too many in
a busy airport environment or when dealing with other more
challenging situations. I'm putting in an order for the "Safety-
Trim" system from TCW to use with Ray Allen servos in my ZenVair
601XL (unfinished). Still haven't heard about anyone else having used
it other than Tim Olson's RV-10. TCW's website is: www.tcwtech.com
Al
On Feb 28, 2008, at 7:11 AM, Gary Ray wrote:
[quote]
Chris
I have the full span left side elevator trim tab. When I get ham
handed I
sometimes inadvertently activate the trim switches on the top of
the control
stick. It will get your attention but it is still controllable.
Same for
the aileron trim.
I have been at full deflection. The first time it happened it took 10
seconds to diagnose what was causing it.
At normal flight speed it has the most authority. At pattern
speeds I need
to increase the trim setting on the aileron.
Time for full deflection is about 3 seconds. By the time you
notice it, it
will be at full deployment so pulling a fuse wouldn't help. It
will take
power to reverse the setting. I think if it happened it would be an
irritation. The controls are normally very light.
Gary Ray 601XL, 64 hrs TT
davgray(at)sbcglobal.net
---
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dredmoody(at)cox.net
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| Posted: Fri Feb 29, 2008 4:24 pm Post subject: what if? elevator trim tab runaway |
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I second Dave Gallagher's advice regarding a CB for the trim. The RAC instructions advise a 2amp fuse or breaker so buy a breaker that can be shut off if the problem arises. That's what I did as well.
Dred
[quote][b]
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psm(at)att.net
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| Posted: Sat Mar 01, 2008 10:32 pm Post subject: what if? elevator trim tab runaway |
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I don't see how a circuit breaker or fuse would help at all if you have run-away trim. By the time you turn off the power to the trim servo, the trim will already be crashed into one end of the travel or the other. Turning off the power just guarantees it will stay there.
Fortunately, I have heard reports that it doesn't take super-human strength to overcome full limit trim.
Paul
XL fuselage
At 10:59 AM 2/29/2008, you wrote:
[quote]I second Dave Gallagher's advice regarding a CB for the trim. The RAC instructions advise a 2amp fuse or breaker so buy a breaker that can be shut off if the problem arises. That's what I did as well.
Dred
[b]
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tski0403(at)yahoo.com
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| Posted: Sun Mar 02, 2008 5:52 am Post subject: what if? elevator trim tab runaway |
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I have talked with some of the guys in my EAA group. most are RV's, and they said that a runaway does not happen that often, but they do run it to the limit and fly. They say it is not that difficult to control, just slow down and fly the plane. A breaker would be good to stop the servo from driving and burning out. Good luck Tom, saving for wings.
Paul Mulwitz <psm(at)att.net> wrote: [quote]I don't see how a circuit breaker or fuse would help at all if you have run-away trim. By the time you turn off the power to the trim servo, the trim will already be crashed into one end of the travel or the other. Turning off the power just guarantees it will stay there.
Fortunately, I have heard reports that it doesn't take super-human strength to overcome full limit trim.
Paul
XL fuselage
At 10:59 AM 2/29/2008, you wrote:
[quote][b]
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ifly4fun2(at)sbcglobal.ne
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| Posted: Mon Mar 03, 2008 6:41 pm Post subject: what if? elevator trim tab runaway |
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On some of the larger airplanes a "trim clacker" aural alert is sounded if the pitch trim is
manually or automatically activated for more then say three seconds to make the crew member aware
of this potential failure mode. Time to install the aural warning box and an EICAS. Just kidding
about the last part...
do not archive
Art
--- Paul Mulwitz <psm(at)att.net> wrote:
| Quote: | I don't see how a circuit breaker or fuse would help at all if you
have run-away trim. By the time you turn off the power to the trim
servo, the trim will already be crashed into one end of the travel or
the other. Turning off the power just guarantees it will stay there.
Fortunately, I have heard reports that it doesn't take super-human
strength to overcome full limit trim.
Paul
XL fuselage
At 10:59 AM 2/29/2008, you wrote:
>I second Dave Gallagher's advice regarding a CB for the trim. The
>RAC instructions advise a 2amp fuse or breaker so buy a breaker that
>can be shut off if the problem arises. That's what I did as well.
>
>Dred
>
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