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Securing RPM Drive Cap

P

PatrickN

Member
Hello All,
I have an IO-390 and bought the RPM drive cap from Vans - part "IE RC-1". The cap is knurled and doesn't have a way of safetying it in place. The knurling gives the impression it's supposed to be finger tight. How are people securing this cap? Is finger tight ok and/or how do you toque it properly?
 
it's really just a dust cover. There is a seal that seals engine oil from leaking around the unused tach shaft, so no issues there. In the certified world the tach cable hooks up there and none of them have a safety feature. Tighten enough to keep it from loosening on its own, maybe an 1/8 of a turn with water pump pliers past finger tight should do it.
Good Luck,
Mahlon
 
I “infamously”lost one one time that I thought was tight - now I only get the ones that have a safety wire hole, and I tether it to something convenient nearby. Like Mahlon says, it’s not a big deal (for the engine) if it comes off, but its a shame to loose it overboard somewhere....
 
The plastic cap can be easily broken even when finger tight. Mine failed on the run-in stand, not on the airplane. Definitely use the metal one.
 
mahlon_r said:
it's really just a dust cover. There is a seal that seals engine oil from leaking around the unused tach shaft, so no issues there. In the certified world the tach cable hooks up there and none of them have a safety feature. Tighten enough to keep it from loosening on its own, maybe an 1/8 of a turn with water pump pliers past finger tight should do it.
Good Luck,
Mahlon
Click to expand...

Ditto. 500hrs, mine hasn’t budged. Wouldn’t really matter even if it did.
 
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