Is using dimple washers to 'rectify' an enlarged fastener hole acceptable for aircraft fairings?

Hi! I'm new to the group so please bear with me if i'm asking a stoopid
question...anyway, i have to 'rectify' an enlarge fastener hole on this
aircraft fairing in a non-aerodynamic critical area of the aircraft.
One option would be to install a patch over the enlarged hole, pick up
the hole and to change the fastener to a longer length one. The other
option is to install the fastener with a dimpler washer; the dimple
washer would take up the space in the enlarged hole and to prevent
further enlargement of the hole. Is the latter option an acceptable
aerospace industry practice?
Reply to
F-5 Techie
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"F-5 Techie" wrote in news: snipped-for-privacy@l41g2000cwc.googlegroups.com:
I don't know anything about aerospace industry practice, but I can guarantee that there will be no "acceptable" patch technique that is applicable in all situations. Even if we believe that you are correct that it is a non-aerodynamically critical area, we don't have a clue what structural loads might be present. At a minimum, in order to answer the question any engineer would need to know:
What caused the hole elongation in the first place? What is the material and thickness of the part with the hole? What is the material, heat treatment, diameter, length, and restrictions on length of the bolt? Does the fastener terminate in a threaded hole, or does it have a nut? What are the likely loads on the fastener? Are those loads variable at short time scales (fatigue life)? Did the fastener have a washer, what type? Is the fastener a hex head or something else? Does the plane fly faster than 100 mph (to exclude duct tape:-)? Is the worn hole round, oblong, or irregular? How big is the worn hole?
I'll stop there, I'm sure you get the idea. An engineer is expected to give a professional answer to engineering questions and that cannot be done without all the relevant information and it is difficult to be sure you have all that information without putting your own eyes on a problem.
Reply to
Charly Coughran
Unless washers are specified as a standard repair somewhere in the CMM or as part of a service bulletin, you need to get in touch with the component's manufacturer and talk to their support group. They'll probably want pictures, and they'll definitely want a detailed story as to how and why the hole got elongated in the first place. If they're OK with your proposed repair, they'll give you an NTO. If they're uncomfortable with your proposed repair, they'll give you alternative direction.
If you start jury-rigging unreviewed, unapproved repairs to the aircraft, you're piling up a whole lot of culpability for yourself in the event of a failure. Be careful.
Reply to
Jack C
This is a question better addressed to an A&P /AI who has superior experience for rectifying airframe mantenance wear.
I believe I have seen both remedies in use however.
Brian Whatcott Altus OK
Reply to
Brian Whatcott
This hole must be in sheet meal so you can't install a bushing.
A formed dimpled washer could not carry any significant bolt shear loads. A custom machined washer with a boss area that fits the hole might work.
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Reply to
Jeff Finlayson
Hi Guys,
Thanks for the advise. The reason that i'm thinking of using the dimple washers is becasue it is used as a repair method for another part of the aircraft and that part is more critical i.e. i reaad across the repair scheme. But you have very good points as to what actually caused the damaged. I would look further into the cause of the damage. Thanks!!
Jeff F>
aircraft.
Reply to
arrow_scout

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