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Proposed AD for PA-28 wing spars

Big jets are supposed to be landed firmly – to achieved the runway performance. If you do a “greaser” landing, you will be using up a few hundred m extra runway, which is OK if you have it, but it isn’t SOP, and autoland won’t do it anyway. Whereas in GA hard landings are not supposed to be done, and I don’t think are necessary even to get into minimal-length runways.

Administrator
Shoreham EGKA, United Kingdom

Rest of Mike Busch’s analysis :

“The eddy current inspection focuses on the inner surface of the two lower outboard bolt holes on
the lower main wing spar cap.
It requires removing these wing attach bolts (which is a bit scary), running an eddy current probe through the bolt holes to detect any cracks, and then installing new bolts and torquing them to spec
If the eddy current inspection detects a crack is found, things get really expensive because the
main wing spar will be required to be replaced with either a new spar or a used/serviceable spar
that has passed the eddy current inspection.
The aircraft cannot be flown until the wing spar is replaced; ferry permits will not be issued for such aircraft.
So it’s important that the eddy current inspection be performed at a shop that either has the capability of doing the wing spar
replacement (which is a big sheet metal job) or the capability of removing the wing and shipping it
to a good sheet metal shop for the spar transplant.
The latter course of action will usually be the most advisable. I know I certainly wouldn’t want my
main wing spar replaced by anyone but the best sheet metal guys I could find. Nobody knows how many
of these airplanes will turn out to have detectable cracks, but if it turns out that hundreds of
airplanes have cracks, the relatively few really good sheet metal shops in the country might be
overwhelmed and backlogged. Owners should plan accordingly.
The AD requires that the results of any eddy current inspection required by the AD be reported to the FAA within 30 days.
The FAA states that it considers this AD to be “interim in nature” and that
it may be amended based on the inspection data that the FAA receives
The FAA has estimated that the eddy current inspection will cost a bit over $1,000 per airplane and
a wing spar replacement will cost over $12,000 per wing. Keep in mind, however, that FAA cost
estimates are notorious for being low, so the actual cost owners pay is likely to be a good deal
more.”

That’s the mother of all ADs
And others may come for other makes.

LFOU, France

This AD is either a big deal or no deal. For any aircraft that has less than 5’000hr total time, or any aircraft with more than 5’000hr but which has never been operated commercially (i.e. no 100hr inspections under 91.409(b)) then no further action is necessary. Many privately owned aircraft have never been operated commercially, even if there are still a lot who are impacted.

LSZK, Switzerland

lionel wrote:

I thought it was more related to pressurisation/depressurisation cycles, actually.

It depends which piece of airframe.
Fuselage (especially forward of the wings) – pressurisation cycles
Wings (outboard of landing gear) – Flight cycles first order and then length of flight as longer flight is more likely to be have more turbulence.
Wings (inboard of landing gear) – Flight cycles, runway type, landings – It’s complicated
Empennage – Flight cycles then turbulence
Fuselage between wing and empennage – depending the design it can be driven by pressurisation or a combination of flight loads and pressurisation

Nympsfield, United Kingdom

chflyer wrote:

This AD is either a big deal or no deal.

For “us” it’s also heavily depending on how EASA will translate to our regulation.
Best case (from cost point of view) would be “EASA-reg doesn’t have 91.409b inspections and therefore this AD has no practical impact on any EASA-reg”
Worst case would be “We do not have 91.409b inspections so let’s just remove this from the formula and go with the 5000h”
Somewhere in the middle “A 100h is a little like our annual airworthiness review so let’s take the number of years instead the number of 91.409b 100hrs”

Unfortunately I don’t trust EASA enough to believe that the translation to European owners will be good.

Btw.: How would FAA look at airframes that have not been under FAA-reg in the past and therefore doesn’t have any 91.409b 100hrs. ?

Germany

Indeed. If EASA counts all 100h inspections, it in fact counts total time .
BTW, I have flown in a number of clubs, and only a fraction counts all landings.

Fingers crossed, EASA will wait for the FAA to do the research and refine the criteria.

Secondary question : are there many shops in Europe (really) able to do such invasive maintenance ?

LFOU, France

Jujupilote wrote:

Secondary question : are there many shops in Europe (really) able to do such invasive maintenance ?

We did this procedure voluntarily on a PA-28-181 in my club a few months ago. There was no problem whatsoever for our regular shop (a 2 man branch of a 145 maintenance facility) to do it. There is nothing remarkable about either the shop itself or its parent company so I don’t see why not any shop should be able to do it. Of course they had to call in someone else to do the actual eddy current inspection and that could prove a bottleneck if lots of aircraft have to be checked.

If you ask why we did it without having to. We had a rather heated debate in the club whether the aircraft was worth renovating for a sizeable sum due to its age (41 years) and flying time (about 10.000 hours, much of which was in training). As we more or less expected this AD to happen anyway, we went ahead with the inspection. (Which, btw, settled the debate — no cracks.)

ESKC (Uppsala/Sundbro), Sweden

How does one change the wing spar? The wing is the wing spar, with some sheet metal attached to it It looks like you have to make a new wing. You can re-use the training edge control surfaces etc, and probably re-use the rest of the skin if not damaged (which will be more interesting if flush rivets were used).

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

How does one change the wing spar? The wing is the wing spar, with some sheet metal attached to it

It’s sort of like changing the chassis of a unit body car, take everything off, replace the expensive bit in the middle, and put everything back on. ’A little more complex than I make it sound….

Home runway, in central Ontario, Canada, Canada

Airborne_Again wrote:

There is nothing remarkable about either the shop itself or its parent company so I don’t see why not any shop should be able to do it.

For the inspection, most shops should be able to do them.

For the replacement if they find a crack I actually doubt it – and even less shops I would trust with replacing the wing spar. And as Savvy writes: It would be a major challenge if you need to ship the wings from the shop that did the inspection to another shop to do the sheet metal job.

The core question, however, is similar to what you obviously have also discussed in your club: On ho many PA-28 will the spar replacement actually be done given their current value and the cost of such a repair. I would assume that for most parts of the fleet a finding in the inspection will be a “damaged beyond repair” anyways.

Germany
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