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Has anyone else experienced this?
Finishing up my annual condition inspection and the A&P and I were checking connections and nuts on FWF. Everything was tight and secure except when we got to the fuel injector throttle body. Only one of the four nuts securing it to the engine was tight. Two were so loose you could spin them with your fingers and one was totally gone. The engine still ran smoothly.
Replaced all star lock washers, replaced the missing nut and tightened all to torque. We then added four nylon end nuts on top of the existing nuts and secured them - there was just enough room on the studs. My A&P said this was the first time he?s ever seen nuts loosened like this - especially if no one?s worked on the item. He distinctly remembers checking the throttle body last year and every thing appeared secure then. Our question: My engine is the Superior XP IO-360 B1AA2, has anyone else found they?ve had to tighten these nuts due to them becoming loose? This could have really ruined my day later this year if not discovered! |
Jim
I have the same exact engine on my RV7. I have found mine tight at all times. I have never found them to be loose. Stay safe & good luck. Darren Kerns RV7 N599DT |
Nylon end nuts?
It's not a good idea to use AN364, AN365 nuts in hi temp environments (i.e. firewall forward). The "nylon" will degrade quickly and fail, allowing the nut to loosen, turn, fall off... |
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A quote from Vic S. on this exact topic.
"While doing a prebuy on Friday on an RV-8 I noticed a nut missing from the aft fuel servo mounting stud. This is not the first one of these I have discovered missing on an airplane. I know standard practice has been to use a nut, a lock washer, and washer, but for many years now I have been using AN363 all metal stop nuts with a washer in these locations and I have never seen one come loose. You might consider it on your airplane." Here's the thread: http://www.vansairforce.com/communit...ttle+body+nuts |
I agree with Vic/Carlos, if you want to be sure, use metal stop nuts.
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Yes indeed
Whilst I was completing my build another builder at our airfield had this same problem after 25hrs. Only one tight nut! The servo was about to fall off.
😳😳😳😳 I have added different types of metal locknuts. On top of the supplied ones. one type is thin nut due lack of available threads. Dont ask for part numbers as the docs are not handy. |
Loose hardware.
Metal locknuts are not a bad idea. The probability of the correct hardware and gaskets coming loose after being properly torqued is incredibly small. I?ve seen a couple cases where the wrong gasket (thicker & softer) was installed and even though properly torqued, over a week or two would compress and unload the lock washers and allow whatever component to become loose. Extremely important that the mags have the right gaskets. My experience is that fuel servos are not unusually prone to coming loose. Always a great idea at every condition inspection or 100 hrs of operation to check the torque on every fastener you can reach.
Don Broussard A&P/IA/ATP RV9 Rebuild in Progress 57 Pacer |
Same setup on my RV7. No issues after 300 hours. I recommend torque seal here, to make verification easy.
Good luck and keep looking closely at everything...Jim |
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