Upcoming AD for many more PA-28 and PA-36 wing spars. 100 anomalies and 6 cracked wings found
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Would it be in poor taste to key the mike anytime I hear "Riddle"
pfarber
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Just to what most airlines do... fly the AC to Mexico and get it done for a fraction of the cost. Sounds like a new business venture... scarf up affected Pipers, fix them in another country where labor is just as good but 1/10 the cost) and resell them with the AD complied.
Or go E/AB.
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pfarber
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From reading this thread it appears the spars were made 'wrong' and people had to die in order for it to be rectified. This is a manufacturing issue. Not a wear or abuse issue.
Not really. They were designed and produced based on the known usage and application at the time under CAR4. Then the regulations changed with Part 23 which added structural life cycles to the equation due to the known increased usage. If it was a true manufacturing error/issue there wouldn't be 2 separate ADs covering the same part. Perhaps if they included "training and aerial work" in the definition of a "utility" aircraft this may have not ever been an issue?
Yeah...a manufacturing error in 40,000 aircraft has finally showed up in ~10 planes some 60 years later.
Reading some of the bigger organizations that submitted comments. There's 20,000+ hour planes used only for flight training that passed with no issues that had spent their entire lives in Florida.
3 of the spars showing cracks were all close serial number planes from one organization. So perhaps there's something metallurgically amiss in that narrow band of serial numbers. Or perhaps something with that organizations training/maintenance practices that caused premature failure.
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pfarber
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"The spar was cold formed leading to high residual stress near the bolt hole locations."
This wouldn't be a FAR/CAR issue, but a choice in manufacturing, correct? First post does say that newer units were produced differently. not knowing what newer units are it seems that this is purely an engineering choice that even today would not be prohibited.
I cold formed many high stress parts on my airplane. it's a valid practice.
If there is a FAR that ages out spars for part 23 designs can you give a reference?
Piper disputed that finding. In fact the only reason they went with a machined spar is because they were having trouble getting the extrusion.
I believe Cirrus is/was limited to 12,000 hours.
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Drake the Outlaw
All new aircraft designs certified since Part 23's inception (February '65) have a life limit.
luvflyin
Touchdown! Greaser!
Just get it over with. Substitute Cherokee for cop car.
Sure. Below is a brief regulatory revision history of fatigue monitoring, ie., spar aging. You’ll note the wing fatigue monitoring starts with Part 23.572. That section remained in effect until 2017 when Part 23 was rewritten which moved the fatigue monitoring into other FAA guidance documents. Questions?
FYI: there are actually two methods available: assigning a life-limit or use fault-tolerant design principals. Diamond Aircraft uses the latter and has no structural life limits and only structural inspection limits listed in the Airworthiness Limitations Section.
Mooney Fan
Cleared for Takeoff
Let us keep in mind, there are a host of aircraft with airframe limits such as the Tomahawk at 11,000/hrs (has an extension available) Cirrus has a 12,000 airframe limit at which time major inspections and repairs will be required.
Trying to sell an airplane with 8K-10K TT already has its challenges.
And what impact will the proposed AD have on Insurance rates if it comes to fruition as written?
Trying to sell an airplane with 8K-10K TT already has its challenges.
And what impact will the proposed AD have on Insurance rates if it comes to fruition as written?
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Drake the Outlaw
Unless we see more wing failures, I don’t see it as an insurance issue. The AD should make the fleet safer, right? And worn out wings shouldn’t be an insurance claim. At least from my POV.
"Don't go away mad, fellas... Just go away."I wonder if we should hope they don’t read forums like this and get some idea of how much pilots who haven’t met them apparently despise them; their quite normal human reaction would probably not be to our benefit. Hopefully they’re bigger/better than that…
moparrob66
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I wonder if we should hope they don’t read forums like this and get some idea of how much pilots who haven’t met them apparently despise them; their quite normal human reaction would probably not be to our benefit. Hopefully they’re bigger/better than that…
This is the federal government we're talking about, right? I'm not optimistic...
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Llewtrah
Watching the storm brewing, I understand your pessimism…
flyingcheesehead
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Thank you @Bell206. I knew the DA40 didn't have a life limit but I didn't know the rules behind it.
I do know that it has dual main wing spars and they did successfully complete the structural certification with one of the spars missing/removed.
To use this as an example, how the fault tolerant design works is if the structure is damaged or fatigued it will not fail catastrophically and be discovered within the inspection time frame stated in the ALS. A lot of newer airplane/helicopter designs have moved to this principal for various reasons. The Cessna SIDS inspections were an attempt to provide a similar but not equal method of surveillance. Unfortunately most of the structural issues manifested prior to the SIDS release plus the fact fault-tolerance design methods were not used back then so any damage/fatigue found was usually fatal to the airframe.
flyingcheesehead
Touchdown! Greaser!
I'm guessing that's also where Diamond's recurring maintenance schedule came from. As I recall there were both voluntary and required inspections... Or maybe it was just that we decided to have all the 2000-hour inspection items done at 1000 hours (we purchased the plane with just under 700 hours on it) because I can't find anything about anything being voluntary.
It depends where the inspection is listed whether its mandatory or optional. In the DA 40 manual, inspections listed in Chap 4 Airworthiness Limitations Section (ALS) are mandatory and the inspections listed in Chap 5 are optional. The reason is the Ch4 ALS tasks are required by rule: 43.16 and 91.403(c). However, if a Chap 4 ALS task references a Chap 5 inspection item those specific items in that Ch5 inspection are mandatory as well.
For example, with a Part 91 DA 40, an owner can have an annual inspection performed per the list in 43 Appx D and still be legal. Then as the Chap 4 ALS items come due he is required to have those additional tasks performed as well. Even when the aircraft hits the 6000 hr Major Structural Inspection limit, the inspection tasks required to be performed are those only marked “MSI” on the Chap 5 forms. None of the other CH 5 inspection tasks are mandatory. Examples below.
DA 40 NG AMM
Chap 4 ALS:
Chap 5 Inspections:
flyingcheesehead
Touchdown! Greaser!
Extra is a mid wing isn't it?
pfarber
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This is informative but does not answer the original question: is cold rolling (or more correctly, cold bending) a spar, or similar machining, prohibited by FAR? It would appear that the CAR/FAR was complied with as a TCDS was issued for the type.
I can see how the CAR/FARs were 'tightened' to include more intensive fatigue analysis for type certification, but there seems to be an 'out'. You can do the math/tests and show the FAA that the metal spars are good, or you can assign a life limit and still satisfy the FAR.
I'm also unable to find the original 60's era life limit number. The 12,000 hour limit appears to be originated when the spars started separating and the reinforcement kit was produced.
This part is a little off topic ------
From reading FAR 23.572 can be ignored if there is a similar structure already approved:
(a) For normal, utility, and acrobatic
category airplanes, the strength, detail
design, and fabrication of those parts
of the airframe structure whose failure
would be catastrophic must be evalu-
ated under one of the following unless
it is shown that the structure, oper-
ating stress level, materials and ex-
pected uses are comparable, from a fa-
tigue standpoint, to a similar design
that has had extensive satisfactory
service experience:
flyingcheesehead
Touchdown! Greaser!
Interesting. I didn't realize it moved that much. It still kinda looks like a mid wing, but it's definitely set quite a bit lower.
And OMG looking at this angle... How on earth does that come out the top?
Is it a one-piece spar and everything above it has to be removed? Yikes.
3393RP
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Probably designed by former Ford engineers that decided removing the cab of an F-250 was the best way to work on the engine.Interesting. I didn't realize it moved that much. It still kinda looks like a mid wing, but it's definitely set quite a bit lower.
And OMG looking at this angle... How on earth does that come out the top?
Is it a one-piece spar and everything above it has to be removed? Yikes.
Was simply answering your question what reference FAR for "spar aging." Regardless, you can use any fabrication method to build an aircraft. The only change was they want you to prove how long the method used will last before failure.
What original limit number?
Not quite. This merely permits the use of previous data to comply with this rule, not to ignore it. Its usually used for model variants and not new models.