Embry Riddle - April 4,2018

[JasonE]

2 out of 11....That makes pretty good odds for an A/D coming!

[pelmet]

NTSB Member Recommends Changes to proposed Piper Wing Spar AD

An NTSB member responded (on NTSB letterhead) to the Proposed Piper Wing Spar AD and said it would like some clarifications and changes made. A summary of the letter, written by Earl F. Weener, PhD:

"While the affected airplanes all have a similar main spar design in the wing attach-point area where the fatigue cracking was found, engineering data presented by Piper separately to the FAA and the NTSB showed that the localized stress level can vary significantly depending on airplane gross weight, cruising speed, and amount and location of fuel in the wings. The data also showed that the airplanes at greatest risk for fatigue cracking are the PA-28-235 model airplanes, all PA-28R series airplanes, and the PA-32-260 and PA-32-300 model airplanes. The NTSB supports the inspection requirements of the proposed AD for these airplanes.

However, the NTSB notes that the data showed that the risk of fatigue cracking on all affected PA-28 series airplanes other than the PA-28-235 is significantly lower over their assumed useful life. We are concerned that the risks associated with disturbing the joint to complete the inspection may outweigh the risk of fatigue cracking in all affected PA-28 series airplanes other than the PA-28-235 and urge the FAA to reexamine the applicability of the proposed AD."

http://piperowner.org/aopa-eaa-join-pip ... -ad-delay/

[PilotDAR]

We are concerned that the risks associated with disturbing the joint to complete the inspection may outweigh the risk of fatigue cracking in all affected PA-28 series airplanes other than the PA-28-235

A worthy concern, and, we've been down this very road before. There was a very similar AD back in the '80's, to inspect PA-28 spar attachments. I did the disassembly and inspection as an apprentice. The AD was withdrawn for the same reason, more damage from performing the inspection than that being found. But, there is still an obvious and real risk of a cracked spar, and finding it would be a good idea.

This is an unfortunate feature of this simple wing attachment design - difficult to inspect, and now inspection has been found to be pretty important!

[pelmet]

I think that I might be supportive of some sort of AD on these aircraft.....

"The National Transportation Safety Board determines the probable cause(s) of this accident to be:
Extensive fatigue cracking in the left-wing main spar lower cap and doublers, which resulted in the in-flight separation of the left wing. The fatigue cracks initiated and grew to a critical size due to flight and ground loads associated with flight-training involving flight-training maneuvers, significant operation at low altitudes and frequent landing cycles. Previously established inspection criteria were insufficient to detect the fatigue crack before it grew to a critical size."

https://app.ntsb.gov/pdfgenerator/Repor ... l&IType=FA

[Capt. Underpants]

If taking them apart to do the inspections causes more damage than the damage typically found, then it seems to me x-rays would be the next logical inspection method. Yes they cost money but this accident has cost ERAU and the families of the victims way, way more.

[pelmet]

These aircraft can live tough lives. Wouldn't surprise me to see more with similar cracks. The report talks about hard landings recorded in the logbook. I bet a lot of hard landings don't get reported.

Reminds me of the Piper Arrow(now gone due to fatal crash in bad weather) at a local flight school where a pilot went to do a walkaround and found a bump on top of the wing. A previous pilot had landed so hard that it(or the structure it was attached to) was pushed upward causing damage. Of course, all the previous pilots denied any hard landing. Bottom line...there have been a lot more hard landings than what is recorded in the logbooks.

[Oldguystrtn2fly]

Does it seem reaosnable to place the AD agaisnt Pa-28 235's when only Arrows have had a issue?

[PilotDAR]

Does it seem reaosnable to place the AD agaisnt Pa-28 235's when only Arrows have had a issue?

I opine that as the design for the wing connection to the fuselage, and means of construction are the same, or very similar, as is the vintage of the airplane, it's hard to make a determination that it would not be appropriate to require an inspection.

It would not be practical to xray instead of disassemble to inspect the wing spar ends. The wing spar ends are bolted into some robust structure in the fuselage, and both that structure, and the bolts themselves could hide a crack in the spar. I have done the wing pull for the 1987 AD of this area in the structure, unless you get it all apart, you cannot be assured that you saw everything.

These airplanes have flown for decades longer than the manufacturer intended. That's not to say that they are no longer worthy of operation, but the manufacturers and authorities are now recognizing that additional inspections are appropriate. This is not a Piper only concern, Cessna's are subject to some pretty important wing attachment inspections too. I am aware of four high wing Cessnas which have concerning wing attachment defects due to age/condition/environment found during inspections this summer. In my opinion, three of these four planes will require structural repair to be safe.

In light of the recent experience with wing attachment defects being found in GA airplanes, I hardly expect the regulators to back off inspection expectations.

[flyguy73]

These airplanes have flown for decades longer than the manufacturer intended.

While this is true, it must be remembered that the accident plane was only about 10 years old, so this fact is not really relevant in this situation. Moreso, it would seem that perhaps if the 50 year old PA28's don't have an issue with this, then they might be OK? (Full disclosure: I own a 48 year old PA28 and not looking forward to an expensive AD).