Landing Gear Bolts- conclusions?

Magman

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Magman
After dealing with loose gear bolts for many years my thought is to document my beliefs.I do not think it conflicts with any mandatory directives for most people. This is an issue that can result in wing or wing spar removal if allowed to progress. That would be another blow to the Cherokee fleet. I did enlist aid from several people in the evaluation and repair process.


The consensus here is that all 4 bolts must accept the loads simultaneously or the spar may be damaged if the bolts are loaded individually. If one bolt is loosened or broken the remaining fasteners overload the spar in bearing and the hole will be elongated. If not promptly addressed it may progress past the allowable oversize published by Piper. Once any hole is elongated it will be difficult to achieve uniform loading again. With the wheel offset to one side of the strut there will be some variation in applied loads.


It’s possible that Piper may have drilled the attaching bolt holes slightly undersize and then reamed to spec as an assembly. This is fine until parts are changed or holes are worn oversize We used a Bore Hole Gage to attempt to get an accurate picture. This was necessary as wear is not uniform throughout. It is disturbing to find that the hole tapers with the spar wearing more than the landing gear “cylinder”. There are more accurate devices but the one we used gives a good “picture”.


Next time will show the tooling for reaming.
 

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4 attach “ cylinder” to lower spar cap. There are 6 others though.

Measuring the hole indicated that 3 first oversize bolts were required on each landing gear. Our goal was to have all the cheese holes lined up when reaming. Removing precious spar metal during a repair would not be good.
The locating fixture was fabricated to assure proper alignment. The Step Pins are standard on one end and first oversize on the other.
Bolting it in place will assure alignment during reaming.

All lower attach bolts are now NAS with one on each side standard diameter. Nuts were torque painted and will be retorqued after 10 hrs.
The length was also recorded. There will be other aircraft next year so
we will record oversize to see if there is a pattern.


In closing I’ll state that the Piper tolerances are close so you should not ignore the consequences of loose bolts.
 

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