Throttle Cable Failure in Flight

[GraemeSmith]

360 hours on the cable.

Failed at the "nip" on the bottom of the red throttle arm.

Pivot all correctly lubed and motion free.

A very fair lead to the sleeve.

--

Was able to get hold of the end of the wire with a small pair of vice grips and operate throttle to a landing. Though the lowest I could get it to idle was 1,400rpom. So having made the runway I had to chop the mags to stop the engine to finish the landing.

Guess I'm going to make that an item I replace regularly.

[GordonTurner]

Actually sounds like an unlikely failure with everything moving freely. Wonder what happened. I suppose as the throttle opens and closes the angle to the fixed point must change a little so maybe it work hardened?

Glad you made it no problem.

Good excuse for a cold (or warm...) beer. Cheers, Gordon

[Sonex1517]

Graeme

Can you post a photo so we all know what to look for?

Thanks

[WesRagle]

Hey Graeme

Can you post a photo so we all know what to look for?

While you're at it, please explain how you just happen to have some vice grips handy :-)

Wes

[fastj22]

During my second or third test flight back in 2013, I had the Bowden clamp on my throttle cable liberate the cable sheath at the carb at full throttle. This relieved me from the burden of power management as I could not regulate engine speed. I was only able to return to earthly endeavors by pulling the mixture to starve the engine of nutrients. 2000 ft agl above the runway I tested my ability to restart the engine by giving it fuel. Then I attempted my first landing, full power into the pattern, pull the mixture on base and try to dead stick it. First attempt, too fast, push in the mixture and go around. Second basically the same. Third I got it right. I ended up replacing the stock Bowden cable with a push pull threaded ends. 450 hours later and no repeat.

[GraemeSmith]

Right There

It's all apart in the aircraft right now - but basically right there against the wire clamp. This is a factory stock picture. Leaving a clean "tail" of wire I could just reach and move back and forth. My wire clamp is a drilled post, two washers and a nylock nut - as described in the AeroInjector Manual Rev D 3/13 Page 10

Break Point

Like here. The post was lubed freely moving in the arm - so I can't say the wire was being flexed to work harden and break it.

The wire is/was 1x7 wire.

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Inspection is tough - because the act of inspecting is as likely to damage the wire. I think I will just go with the solid spring wire option per the manual and replace it every 100 hours or so.

While you're at it, please explain how you just happen to have some vice grips handy :-)

When out on a X-Country I have a 7lb weight penalty in the baggage compartment with wrenches, sockets and the like - specific to my plane that would allow for field repairs or allow me to hand a mechanic the right size of something they might not have to hand. And of course there are vice grips to cover anything you might not have.

[Rynoth]

Prior to first flight I had a throttle cable failure on the ground at full throttle position due to a sticky residue at the carb. Basically the exposed cable at the throttle lever bent and bowed, losing its rigidity and ability to "push" the throttle closed. I ended up replacing it with 0.075" piano wire (it fits in the same sheath as the stock Aeroinjector cable) which seems to have a much more positive push/pull authority with less likelihood of kinking.

http://www.rynoth.com/wordpress/waiex/2 ... le-issues/

I suppose the silver lining is that the pull-open design of the Aeroinjector makes it more likely for this type of failure to result in an open, rather than closed, throttle position.

[GraemeSmith]

Actually sounds like an unlikely failure with everything moving freely.

It's a relatively common failure on solid wire mixture cables. (Like I've seen it about 5 times on 10 years). The person pulls up to the fuel farm, pulls the mixture to shut down the engine and pulls armfuls of wire into the cockpit while looking bemused. The work hardened (but probably 20+ year old) wire failing at the nip point on the clamp on the mixture arm on the carb. But that failure is relatively safe. The sprung arm puts the engine full rich and you can stop it with the fuel tank control or the mags.

I'm in two minds about the replacement cable. 1x7 wire should be less prone to fatigue failure. Solid wire is a lot cheaper to replace often. I'm thinking of making this a replacement item to be carried out at each condition inspection. (I fly about 120 hours a year).

[builderflyer]

It's a relatively common failure on solid wire mixture cables. (Like I've seen it about 5 times on 10 years). The person pulls up to the fuel farm, pulls the mixture to shut down the engine and pulls armfuls of wire into the cockpit while looking bemused.

I must lead a charmed life. I've yet to personally observe this phenomenon on one of my airplanes or anyone else's in my over 55 years of flying. But I don't question that it can happen, just not in my presence.

Art,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,Jabiru 3300 #261

[9GT]

I would not use one of those lawn mower cables again on a plane. We used one on the Cozy MKIV we built and installed a spring on the fuel servo throttle lever to pull it full open in case of a break. It happened once! It will at least give you full throttle to land the plane if it breaks during flight.