Cessna C337 SID

K337A · #1 08-20-09, 01:36 PM

C337 SID ?

Is there a public database of documented failure/failed inspections of C337 spars? I have the 5000 hr. AD. on my desk and have wondered about the failure rate of this inspection and the incidents which required it. What has caused this at this time? I have checked the NTSB database the best I could and the incidents of Spar problems causing a accident beside repeated aerobatic flight is non existent. It would be good science to be able to compare failure rates with other aircraft in a logical process. God help the GA owner if the FAA Legal Department has chosen this avenue to demonstrate their authority to the lowly taxpayer/owner.

WebMaster · #2 08-20-09, 01:41 PM

I really like your avatar.

K337A · #3 08-20-09, 02:50 PM

Unfortunately I have been through this dog and pony show before. Please refer to this article from Mike Busch from 2004. Cessna will sit and listen but the course of action is already determined by Cessna with the FAA blessing. The sad part about this is that there is no, nada, zero determination by investigation if aircraft was abused or g limits routinely exceeded. And don't ask Cessna for the Analysis data or you will be hustled out by the TSA,Homeland Security, FBI or Marv Nuss personally.

twin.cessna.org/reference/twnc400nprms2.pdf

http://www.avweb.com/news/features/189243-1.html

K337A · #4 08-20-09, 03:25 PM

- Mr Truman Sparks and his fine flying machine. Best line in the film as he picks up the chicken ...."No flying today Agnes". Then Mr. Sparks does a a little field approved Duct tape repair. Aircraft is now owned by Randy Deluca's son. Still fly's it out in California.

edasmus · #5 08-20-09, 05:17 PM

Thanks for the info gentlemen. I tell ya, I must be getting old and crabby, but between the FAA (who happens to be my employer incidentally), the TSA, Cessna, and others, flying my Skymaster on a sunny day to play a round of golf is getting to be more and more challenging. It shouldn't be so complicated.

Thanks again! Ed

WebMaster · #6 08-20-09, 05:34 PM

I couldn't agree with you more Ed. Just be thankful you weren't planning on going to Martha's Vineyard real soon.

Ernie Martin · #7 08-20-09, 06:26 PM

The two links contained in one of the above messages were very informative.

The one important element that may be pertinent to the upcoming meetings and where we have critical data to contribute is cabin weight.

This is somewhat simplified, but in the first of the two links, Mike Busch makes the case that Cessna's analysis seems to have assumed large cabin loads and low fuel loads in the stress analysis, yielding fatigue lifes which are much shorter than if it had assumed low cabin loads and high fuel loads*. I believe that 337s are mostly operated with low cabin loads (often with 1 or 2 occupants) and often on long-endurance surveillance missions (with large fuel loads). I know that I never use my 5th and 6th seats. We must try to get Cessna to consider this, which will result in much longer safe life if the 337 wing structure and stress distribution bears some similarities to the 400 series.

Ernie

* "The tensile stress on the critical wing main spar elements is a function of cabin load (i.e., zero-fuel weight), not of gross weight. In fact, fuel weight (which is outboard of the “ hot” region) actually reduces the stress. It turns out that fatigue life is exquisitely sensitive to changes in tensile stress—a small reduction in stress can result a big increase in safe life" (abreviated excerpt). Yet Cessna proposed the same safe life for the 401 models (which came with seating for 6) and for the 402 models (which came with higher-density seating of up to 11 passengers). And Cessna did this despite the fact that "there are six known instances of 402s with cracked spars, but no known instances of 401s with cracks."

Skymaster337B · #8 08-20-09, 11:28 PM

I'd like to talk to the Cessna folks about their SID plans. Who is the contact over there at Cessna? Even if I can't visit in person, perhaps teleconference or phone interview. My other question is why does Cessna even care about 337's any more? It must cost them allot of money to worry about old Skymasters...especially since we can't sue them any more since all Skymasters are over 20 years old (Federal law). My point is I smell a rat. Does Cessna have a plan to shake us all down for "Life Extension Kits".