Would it be in poor taste to key the mike anytime I hear "Riddle"ERAU conspicuously missing...
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.Not only that, doubtful there are many A&Ps that would even be interested in tackling that kind of project. Any if you happen to find one, guaranteed it will be long and drawn out.
Piper never intended on these planes being around forever. If they could go back in time, I’m sure they would life limit the airframes.
Warranty on a 50+ year old airframe that’s had 20 plus owners, questionable maintenance, stored outside and other factors is not even realistic.
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?From reading this thread it appears the spars were made 'wrong' ...
Yeah...a manufacturing error in 40,000 aircraft has finally showed up in ~10 planes some 60 years later.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.
"The spar was cold formed leading to high residual stress near the bolt hole locations."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?
Piper disputed that finding. In fact the only reason they went with a machined spar is because they were having trouble getting the extrusion."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?
The Rockwell 112/114 and Piper PA-38 have life limits per TCDS.
I’m sure there are a few more.
All new aircraft designs certified since Part 23's inception (February '65) have a life limit.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.
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?If there is a FAR that ages out spars for part 23 designs can you give a reference?
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.All new aircraft designs certified since Part 23's inception (February '65) have a life limit.
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.And what impact will the proposed AD have on Insurance rates if it comes to fruition as written?
"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…
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…
Watching the storm brewing, I understand your pessimism…This is the federal government we're talking about, right? I'm not optimistic...
All new aircraft designs certified since Part 23's inception (February '65) have a life limit.
Thank you @Bell206. I knew the DA40 didn't have a life limit but I didn't know the rules behind it.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.
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.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.
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.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.
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.I can't find anything about anything being voluntary.
Extra is a mid wing isn't it?The Extra 300 has a 1000 hr Inspection required by AD IIRC.
It is a low wing aircraft but the one piece Wing comes out the top.
Daunting!
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.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?
View attachment 135094
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.
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.My post reflected the 300L and I edited the L in.
Evidently some earlier models were mid wing but the L is 8 inches lower.
And OMG looking at this angle... How on earth does that come out the top?My point was it was an unusual way to remove a wing.
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.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?
What original limit number?I'm also unable to find the original 60's era life 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.From reading FAR 23.572 can be ignored if there is a similar structure already approved: