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rcsfca
Joined: 22 Feb 2008
Posts: 10
Location: San Francisco Bay Area
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 Posted: Mon May 18, 2009 9:05 pm Post subject: Runaway plane - serious mishap - throttle cable |
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My Model IV - 1200 Rotax 912UL suffered major wing and prop damage today after striking the corner and face of a concrete hangar due to a throttle cable malfunction.
After a normal start this morning at my own hangar, I taxied across the airport (CCR) to the local avionics FBO for some radio and GPS work. Following a 15 minute inspection of the proposed panel changes, the techs asked me to move the plane to an adjacent hangar. I started the engine, which roared to life at full throttle (6000 rpm?) in a heartbeat, and the plane snapped forward into a circular move even though I was firm on the brakes. (It swung in a circle because I had some left rudder into it, which was lucky because I had other aircraft parked in front of me on the ramp.)
Thinking that somehow the throttle had been pushed in (which it hadn't because I had double-checked it for an idle setting before cranking the starter), I pulled back on the throttle and it came out of its housing and into my hand. Three seconds later, the plane hit the building, caving in the right wing and shearing the IVO composite prop. Turning off the magnetos was too late.
There was no fire and I was not injured, and there was plenty of help around to handle the leaking gasoline from the wing tank. But the wing, flaperon, and prop are finished. The balance of the plane, interestingly enough, was undamaged. The steel frame will have to be checked for squareness but the wind spar and wood absorbed the impact.
The problem with the throttle is as follows:
My plane, built in 1994, has the bellcrank-style throttle control, which divides the forward and reverse motion of the throttle handle between the two carbs. The throttle handle is attached to the bellcrank by a stiff steel 1/16" rod that runs from the backend of the throttle handle to a hole in the bellcrank mechanism where it is secured by a set screw retainer.
What happened in my case was that - unknown to me - the rod was completely straight and ran through the retainer hole with neither a secondary safety retainer on the other side of the hole nor a 90+ degree bend in the rod on the other side of the hole to keep the rod from being pulled out in the event the primary retainer set screw let loose.
So this morning the (single) set screw let go, the throttles on the carbs went to their default full-power position (WOT), and when I pulled back on the handle, the steel rod slid out of its bellcrank retainer and the whole throttle handle ended up in my hand.
An important suggestion to any of the owners out there who have this type of throttle control:
- Immediately check your rod-to-bellcrank retention screw for tightness.
- Get a secondary retainer on the rod.
- Put a bend into the rod after the secondary retainer to allow the rod to hook the bellcrank in case of retainer failure.
- Purchase the Kitfox Aircraft replacement throttle cable ($219) that does not use the bellcrank at all - it is a twin-cable style control of a completely different design.
Hope this has been complete enough - maybe there's been something AD-related already published or a prior thread. It has been a long hard day but I don't want any members of the community to not know about the incident in case their throttle equipment is the same as mine.
Rich Cunningham
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Dick Maddux
Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl
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| Posted: Tue May 19, 2009 4:21 am Post subject: Runaway plane - serious mishap - throttle cable |
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I am sure sorry to hear about your accident but thank god you were not hurt !!! I had a similar one when I hand propped a homebuilt and it started far above idle and the prop was trying to eat me. I got out of the way and ended up grabbing the wingtip. (low wing) Can you picture a guy going round and round at the airplane wash rack at Reid Hillview airport (years ago) holding onto the wing tip ? I know it looked funny but it wasn't .Finally I made a wild leap at the cockpit and was able to shut the engine down. After cleaning my shorts,I vowed not to do that again.
I have the same type of bellcrank that you have but I do have secondary bug stops. After hearing what happened ,I am sure going to recheck everything. Thanks for sharing and I hope you can get it fixed soon!
Dick Maddux
Milton,Fl
An Excellent Credit Score is651/aol?redir=http://www.freecreditreport.com/pm/default.aspx?sc=668072%26hmpgID=62%26bcd=MayExcfooter51609NO62>See Yours in Just 2 Easy Steps!
[quote][b]
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PMorel
Joined: 09 Jul 2007
Posts: 62
Location: Locust Grove, GA USA
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| Posted: Tue May 19, 2009 5:19 am Post subject: Runaway plane - serious mishap - throttle cable |
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That's scary. Something like that is always in the back of my mind with the carbs set to their default of full-power. What are your thoughts on adding a counter balance spring to the Vernier throttle control to reduce the immediate full throttle? I'm not saying to eliminate the full throttle default, but to reduce much of the tension.
Paul Morel
Model IV Speedster 912
From: rcsfca <r66rc-matronics(at)yahoo.com>
To: kitfox-list(at)matronics.com
Sent: Tuesday, May 19, 2009 1:05:31 AM
Subject: Runaway plane - serious mishap - throttle cable
--> Kitfox-List message posted by: "rcsfca" <r66rc-matronics(at)yahoo.com (r66rc-matronics(at)yahoo.com)>
My Model IV - 1200 Rotax 912UL suffered major wing and prop damage today after striking the corner and face of a concrete hangar due to a throttle cable malfunction.
After a normal start this morning at my own hangar, I taxied across the airport (CCR) to the local avionics FBO for some radio and GPS work. Following a 15 minute inspection of the proposed panel changes, the techs asked me to move the plane to an adjacent hangar. I started the engine, which roared to life at full throttle (6000 rpm?) in a heartbeat, and the plane snapped forward into a circular move even though I was firm on the brakes. (It swung in a circle because I had some left rudder into it, which was lucky because I had other aircraft parked in front of me on the ramp.)
Thinking that somehow the throttle had been pushed in (which it hadn't because I had double-checked it for an idle setting before cranking the starter), I pulled back on the throttle and it came out of its housing and into my hand. Three seconds later, the plane hit the building, caving in the right wing and shearing the IVO composite prop. Turning off the magnetos was too late.
There was no fire and I was not injured, and there was plenty of help around to handle the leaking gasoline from the wing tank. But the wing, flaperon, and prop are finished. The balance of the plane, interestingly enough, was undamaged. The steel frame will have to be checked for squareness but the wind spar and wood absorbed the impact.
The problem with the throttle is as follows:
My plane, built in 1994, has the bellcrank-style throttle control, which divides the forward and reverse motion of the throttle handle between the two carbs. The throttle handle is attached to the bellcrank by a stiff steel 1/16" rod that runs from the backend of the throttle handle to a hole in the bellcrank mechanism where it is secured by a set screw retainer.
What happened in my case was that - unknown to me - the rod was completely straight and ran through the retainer hole with neither a secondary safety retainer on the other side of the hole nor a 90+ degree bend in the rod on the other side of the hole to keep the rod from being pulled out in the event the primary retainer set screw let loose.
So this morning the (single) set screw let go, the throttles on the carbs went to their default full-power position (WOT), and when I pulled back on the handle, the steel rod slid out of its bellcrank retainer and the whole throttle handle ended up in my hand.
An important suggestion to any of the owners out there who have this type of throttle control:
- Immediately check your rod-to-bellcrank retention screw for tightness.
- Get a secondary retainer on the rod.
- Put a bend into the rod after the secondary retainer to allow the rod to hook the bellcrank in case of retainer failure.
- Purchase the Kitfox Aircraft replacement throttle cable ($219) that does not use the bellcrank at all - it is a twin-cable style control of a completely different design.
Hope this has been complete enough - maybe there's been something AD-related already published or a prior thread. It has been a long hard day but I don't want any members of the community to not know about the incident in case their throttle equipment is the same as mine.
Read this topic online here:
http://forums.matroninbsp; =======================
[quote][b]
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_________________
Paul Morel
912 Speedster
Locust Grove, GA
www.WingsAirPhotos.com |
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lcfitt(at)sbcglobal.net
Guest
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| Posted: Tue May 19, 2009 6:53 am Post subject: Runaway plane - serious mishap - throttle cable |
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I too am sorry you had that experience. I trained at CCR years ago with Lou
Ellis. I think this makes your experience a bit more personal to me. I am
at Cameron Park. I don't know how I might help in the repairs, but if you
think of something let me know.
Lowell Fitt
Cameron Park, CA
Model IV-1200 R-912 UL
prepping the fuselage for covering.
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lcfitt(at)sbcglobal.net
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| Posted: Tue May 19, 2009 7:11 am Post subject: Runaway plane - serious mishap - throttle cable |
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Paul, I did exactly that. I ran a counteracting spring from the head of
the bugnut in the center arm of the bellcrank to the cross tube behind the
lower instrument panel. I had almost perfect ballance with the throttle. I
did it mostly to prevent the throttle jump if I inadvertently brushed the
button. As Dick suggests, I also had a second bugnut on the throttle rod.
Lowell
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