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throttle return spring replace at 100hr?

seagull

Well Known Member
The latest service schedule rev 9.4, says to replace the throttle return springs at 100hr. I remember the previous expansion springs had a problem breaking and required periodic replacement regardless of they were broken. Since then the springs have been upgraded to the "clock spring" type that go around the throttle shaft. I thought that solved the breakage problem. Is this replacement requirement left over from the old springs or is it still required?
 
Seagull
If no one her can answer this, perhaps an email to Van?s Support would get a reply?
If so, please post the info here.
 
Probably less stress on the return springs if you store your plane with the throttle all the way in, when in the hangar, and only pulled near all the way out, when you start up.
 
Scott,
What is your opinion on this?

When the new spring was introduced there was no intent to set a life limit so I think it was an oversight and should have been removed from the Service Schedule.
I will look into it tomorrow.
 
My opinion?. torsion springs, properly designed and applied in a simple application such as throttle shaft, should last a very long time. Coil ends on a torsion spring are a non-event unlike the old style extension springs. I would check for wear on the hook ends and corrosion at Annual Condition Inspection.
 
Just wondering if there is an answer to the OP question yet?

A revision of the Maintenance Manual is planned at the next revision cycle, to remove the 100 hr requirement as long as the tension springs have been replaced with the torsion springs.
 
It was trial and error. The first set from HF broke. I bought several from Home Depot and cut the spring to length that seemed to give the best tension.
 
Check the brass throttle arms where the springs rub. The steel spring wears a groove into the brass, which eventually causes it to catch, leading to uneven throttle opening.
both my -12s had to have replacements at around 800 hours.
 
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