Main Spar - Loose rib caused a rub on the spar

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softlanding1
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Main Spar - Loose rib caused a rub on the spar

Post by softlanding1 » Tue Sep 22, 2015 19:07

My Champ is going through an annual inspection, and the mechanic found a loose rib that has rubbed the main spar. He says that it has caused a rub about 1/16" deep. Based on that finding, he's telling me that the spar must be replaced. I don't know if I can argue that point, but I thought I'd throw something out here and see what the rest of you think of this. Seems like a rub wouldn't necessarily cause a compression crack. I was thinking maybe that the area can be sanded and smoothed out. Not a wood and fabric repair guy, so I'm looking for some advice.

N82924 - Bruce Marchionda
Bruce Marchionda
North Texas
Texas AeroSport - X65

jdpflyer
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Re: Main Spar - Loose rib caused a rub on the spar

Post by jdpflyer » Tue Sep 22, 2015 22:48

Best source for the inspection would be AD 2000-25-02 and Service letter 406. You may want to measure it again.

Paul Agaliotis
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Re: Main Spar - Loose rib caused a rub on the spar

Post by Paul Agaliotis » Wed Sep 23, 2015 12:20

Buuce,
Like pointed out, see SL 406. Be sure to measure the spar width, I've found some that were slightly larger than the drawing.
Paul
Mailing Adress : Paul Agaliotis 2060 E. San Martin, San Martin,Calif. 95046

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softlanding1
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Re: Main Spar - Loose rib caused a rub on the spar

Post by softlanding1 » Wed Sep 23, 2015 14:11

Are you saying that if the spar was wider than minimum specs it could be repaired because the good wood would meet the minimums? As in, if the spar was specified at 5 1/2 wide, and this spar is 5 3/4 wide, the spar could still be airworthy? Sorry if I'm asking a dumb question. This will be the difference between scuttling the plane or not.

This is the area of the SL that sems to have caused the rejection:

Inspect for loose or missing rib nails per Service Letter C-139. If loose or missing nails are
found, inspect spar by the rib for damage resulting from the rib rubbing against the spar. If
the friction between the rib and spar has broken the wood grain completely across the spar
and more than 1/16” deep, this is cause for rejection. Also inspect for nail hole elongation.
Rejection must also occur if the nail holes have elongated such that wood grains are broken
more than 1/16”.

My question is if this is a repairable situation, or if it requires complete spar replacement. And, since replacement is a distinct possibility, I'd love to get some idea as to what a reasonable cost might be, so I can keep the mechanic honest.
Bruce Marchionda
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Paul Agaliotis
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Re: Main Spar - Loose rib caused a rub on the spar

Post by Paul Agaliotis » Thu Sep 24, 2015 14:11

Bruce,
On one of the planes I worked on, the spar was almost 1/8" wider than stock. If the rejection criteria is for 1/16" wear on the bottom this would be from the manufacturing dimension. The wear amount would be allowed based on their engineering information. So if the spar was 1/8" over specification you could allow 3/16" wear with this specific condition.
That's what I meant about measuring the spar size.
If the spar needs replacement the spar is about $900,last time I bought one. To replace it about 24hrs labor. And to cover about $3/4000. This doesn't cover the R&R, 337's and such.
Paul
Mailing Adress : Paul Agaliotis 2060 E. San Martin, San Martin,Calif. 95046

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