Is there a reason the recent 400 series Cessna AD might not end up on the 300 series also? Are the spars different or the loads different?

Thanks,

Rohan

The twin Cessna spar controversy dates back to 2004 time frame. It was based on some rather questionable analysis, and spurred on by a damaged non conforming 402 shedding a wing (the Goldsby, OK accident)

In the end, the wing spar AD had no solid basis, but the FAA went forward with it on 402s and 414A. Cessna had proposed wing spar SIDs for all the twin Cessna models, with the idea that would become ADs. But after the 402/414 AD went through, the FAA seems to have quietly dropped the whole thing and left the 402/414 AD in place.

Since that was ~14 years ago, I expect no action in pending.

There's a lot more to this story, but it would take a novel to tell it all. The basic gist of it is the FAA doesn't know math very well and really wasn't a very good gatekeeper of truth in this matter.

Realistically, the twin Cessna spar is just fine. I am not aware of a ANY conforming twin Cessna spar failing from fatigue. The vast majority of twin Cessna spar failures are from turbocharged exhaust failures, so spend all your worry and care on that and don't worry about the spar at all. The few others are from single cycle overload (say, from spatial disorientation, but even that's very rare), and there is one case of a defective spar coming apart (though it gave PLENTY of warning over several years).

In short, the twin Cessna spar is FINE and I would expect no further AD action on it.

The Goldsby 402 accident:

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

Mike C.

Thanks Mike - great reply. I just re read the 400 series recent AD and it is for high time aircraft and an inspection. Someone told me it was of risk of spreading to the 300 series - do they have the same spar set up?

I am looking at a 340 at present with a view to flying it from the UK to the US as I want to do the crossing but would sell it once over there.

Regards,

Rohan

N340GJ by chance? I've seen it on Controller and it looks like a nicely equipped plane. Even has an HF for your crossing!

There is a SID for the addition of a spar strap on the 340, but it is out at something like 25,000 airframe hours.

There was also a failed spar on a Cape Air 402 that did not involve a crash. I think the wing was held on by the skin. I don't recall if the pilot noticed a problem in the air, or if the floppy wing was detected on the ground post-flight.

I know the story of that situation fairly well.

An Island Air 402C was being flown and the pilot had to hold excessive aileron input to fly the plane level and it was getting worse as the flight progressed. After landing, he refused to fly the plane any more. Upon inspection, at wing station (WS) 114 on the left wing, the lower spar cap was found broken and the web had cracked almost to the upper spar cap.

WS 114 is right behind the exhaust and thus an area subject to thermal as well as other stresses. Interestingly enough, the analysis Cessna had done on the 402C wing identified a number of "hot spots", places where the fatigue damage is highest. None of the spots were anywhere close to WS 114, which leaves one wondering about the Cessna analysis. The spar strap kit Cessna produced for the 402C was based on their analysis, which suggests it may be not fixing the real problem exactly.

The plane landed at Hyannis where it was inspected and the spar cap failure on the left wing discovered. The wing was changing incidence slightly which accounted for the aileron input required for level flight. A partial crack was also found on the right wing, also WS 114. Cape Air then inspected their 402C airplanes (also based out of Hyannis) and found one of their planes with a crack at WS 114.

Having two 402C with spar cracks prompted the FAA to issue an emergency AD for checking that location:

https://www.aopa.org/-/media/files/aopa ... .pdf?la=en

It should be noted that 402C used in airline duty are incredibly short haul, rapid cycle, high cabin load, low fuel load flights. The airplanes with cracks had over 20,000 hours each. The way those airplanes are used *greatly* increases fatigue damage over what an owner operator would do. It is not a stretch to say an owner operator that has lighter cabin loads, longer cycles, and more fuel load wouldn't have the same fatigue damage in 100,000 hours as the airline 402C airplane shad in 20,000 hours. That is the nature of fatigue damage, even very small increases in the cycle load can result in hugely more damage per cycle.

The other 402s that had spar cracks, 402A and 402B generally, were used for Grand Canyon flights. You cannot devise a more fatigue severe use case than that. Always max cabin loads, always near zero fuel, always near the ground, always in day time with turbulence generated by mountains and a state with ultra high solar heating, always with lots of turns, always with short cycles (~45 minutes). The planes were not given the best maintenance, either, and they flew 8 hours a day and had 20,000+ hours in short order.

The FAA refused to consider the use case when looking at this issue. So owners of 414As got an AD for spar fatigue damage they will NEVER see because cheap operators abused 402s in the Grand Canyon.

There is not a damn thing wrong with the twin Cessna spar. The only issue is a misguided analysis from Cessna and an FAA that doesn't have the brain power to understand fatigue damage. Given the years that have passed without further action, I would hope the folks at the FAA have realized the spar is fine and now are just quietly doing nothing.

Mike C.

Hi Scott - ha yes that's the one - its at my home field but has been sitting a while as the owner sadly passed away.

Thanks for all the information - seems that on any aircraft sub 10-15k hours it is not worth a thought.

Those twin cessnas sure are pretty and have a presence on the ramp.

For those not aware of Mike C's history with the Twin Cessna wing spar issue, he was instrumental in helping plead our case against the FAA issuing a broader AD. There was a meeting with the FAA where interested parties were invited to present and IIRC Mike was the only presenter not affiliated with an alphabet group and only one of a very small number of presenters. He may have been the only presenter, but my memory fails to call up that tidbit of information.

He did what Mike does which is to research the hell out of the issue and discovered that the AD was unwarranted and that their basis for it was unsupported by credible facts.

Mike contributed substantially to keeping the AD from being expanded beyond its original scope.

even though it is an apparent non-issue on the normal AF times, it aided in my decision to buy the 340. I didn't want to risk getting caught in a 414 AD.

as has been stated many times, find a plane that has a great maintenance pedigree, examine the exhaust system every time you have the cowling off, and it'll be fine.

https://flightaware.com/live/flight/N340AJ

love the 340.

And you have one of the sweetest 340s out there Gary.... I'm glad to see you are enjoying it.

I have YOU to thank for that. I couldn't add anything to this plane if I wanted to...