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Proposed AD for PA-28 wing spars

We completed the AD on our PA28-181 a couple of weeks ago and it was luckily without cracks.
It has around 9000 hrs from private and school flying. Payed about 1300 euro for it.

ESSZ, Sweden

Eddy current tests found indications of a tiny crack in the bolt hole of the wing spar in the location that is of concern in the AD. Each of our aircraft has one bolt hole on one wing that is an issue. The Eddy current picked three indications, two at .030 and one at .010. This means that the cracks are tiny and haven’t spread to the wing spar, so no one was in danger.Quote

Hmmm, the inspection is the spar itself, so if a crack was found, it was found in the spar itself (as stated in the first quoted sentence. It makes the third quoted sentence rather untrue!

Home runway, in central Ontario, Canada, Canada

Archer-181 asks a question

WilliamF21-Jan-21 18:5094
A friend of mine with a maintenance shop did a dozen of these eddy current inspections today. They will be less than €500 of an additional cost to an annual.

Hi WilliamF . Can you report if there were any failures in this dozen inspections. In my case I was one of three Pipers which we did 2 years ago within a few months of the Embry-Riddle accident as it was so shocking. All three of us passed for a cost of less than £ 400 each including spraying the wingbox area with ACF50. (There was myself a PA28-181 with 9,500 hours, an Arrow and another Piper not sure of the details of those)

On the American Piper Forum somebody mentioned an NDT company were experiencing a 4% failure rate. [That was on 102 wings where 4 failed] I just heard of one UK PA28-161 failing. Perhaps the cracks creep out very slowly as with such a huge fleet of PA28’s – many very tatty, old and poorly maintained, catastrophic wing failures are thankfully rare.

Last Edited by Archer-181 at 20 Feb 09:26
United Kingdom

We have one failed in our club, one that was on the way to IFR conversion… Luckily the owner found another wing, but unexpected cost…

LFMD, France

I can see a brisk trade in PA28 wings with owners of aircraft with a right wing failure go looking for aircraft that have had a left wing fail the check.

I however would be interested in late PA28 wings that have failed the inspection.

Why do you think the quailty on the later built models isn’t as good?

No, I don’t see any build quality issues with early wings, Its all about the re-sale value of refurbished wings.

The reason why the AD impacts later wings is that they are longer so the moment of force at the wing root can exceed the calculated “safe” level.

Whilst the spars tend to be basically the same, all models have different amount of extra L shaped reinforcements at the root. There is a very useful video produced by Airframe Components which explains it all



United Kingdom

That’s a very interesting video. It has caused me to re-think the issues around re-sparing these wings and the jigs required to do the job.

The UK CAA have published a proposed AD for this:

http://publicapps.caa.co.uk/docs/33/PAD%201977.pdf
PAD_1977_pdf

In short:

The way you calculate whether an inspection of the spar is required, and hopefully I’ve got this right…

(EFSH means “EASA factored service hours”, TIS = time in service).

1. Calculate the AAU (average annual utilisation) – TIS/years
2. If AAU >= 100, calculate the EFSH (else stop here, no inspection required).

EFSH = (TIS – (100 * years)) + (100 * years) / 15

3. If the EFSH >= 5000, then within 100 hours of reaching the EFSH of 5000 or the issue of the AD, the inspection must be carried out.

(given they’ve not put brackets around the division at the end, it’s assumed that you calculate it following the normal BODMAS operator precedence rules…)

(a simpler formula with the same end result as the EFSH thing above would be (320 * spar_age / 3) + 5000 >= spar_tis means you’ve got to do the eddy current inspection).

Last Edited by alioth at 12 Mar 17:22
Andreas IOM
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