Cessna C337 SID
 

I have received a request from Cessna for a gathering of a few people to discuss the SID that is upcoming for Cessna 337 aircraft.

The text of the message is this

I am looking to locate some experienced 337 owners in Kansas and the surrounding near by states to have a meeting to discuss and get customer feed back for the SID’s program coming up for the aging Cessna 337 aircraft.

Could you help me with this?

Thank You for your time

Cameron Miller



We have had a flurry of Email's going back and forth, and the upshot is that Herb Harney, our President, has offered to spearhead the contact with Cessna.

Anyone wishing to be involved in this discussion, please contact Herb by email, at hharney@sbcglobal.net

Please forgive my ignorance, but what is the "SID" program?

Supplimental Inspection Documents

http://www.casa.gov.au/airworth/info/CessnaSIDs.pdf

The link above is a good description of the program.

Further to Herb's message above, the Supplemental Inspection Document addresses inspections and modifications required for aging aircraft to remain airworthy. The most infamous is the one for 402 Cessnas, which for aircraft with over 15,000 hours requires the installation of wing-spar straps in a procedure that is so expensive that it threatens grounding much of the fleet. Cessna is now working on other models, including the 337.

But please note:

1. The 402s are low-wing aircraft with wing mounted engines and some have a dry wing with the fuel in tip tanks, so the loads at the root of the wings are quite different than for a 337.

2. Many (most?) of the 400s have spent much of their life in charter operations, accumulating thousands of hours per year, so fatigue cycles are much greater than for the typical 337.

It's possible that the difference in loads and designs will result in an SID for the 337 which is considerably less costly and may be applicable even later in life (say, 25,000 hours). Since most 337s have far less hours, few aircraft may be affected over the next decade.

But we need to stay on top of this.

Ernie Martin

The SID program calls for inspections. It is no different than the requirement for wing spar x-rays on Beech 18's, or the spar inspection or other mandatory service bulletins for twin commanders. While Ernie is correct that it has been applied to 402's, it has also been applied to 414's, and the 425 and 441 turbo props. On the 441's, they determined that the fleet averaged 8000 hours. The initial requirement for the SID was extremely invasive. It consumed so many hours that the centers that could do the SID were overloaded, and they extended and modified the requirements. Incidentally, the initial SID for 425's was anticipated to cost $150K to $250K, depending on the findings.


Cessna has obviously decided to extend the program to other aircraft. The initial implementation may not be the final outcome. As Ernie says, it's important to stay on top and be aware.

Between now and the initial implementation, the input from users should have a major impact on how it is implemented. It behooves everyone to be as involved at this point as possible. If you live in Kansas, or would like to be involved in the discussions, please send Herb an email.

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.

I really like your avatar.

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

- 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.

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

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

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."

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".

For a background on why this is being done, read the first of the two links in the 3rd message from K337A.

Ernie

Amigos,

AOPA responded thusly to an inquiry about what they knew about the proposed 336/337 SID:

Paul,

John Collins asked me to respond to your question on the Cessna SID program. The Cessna SID program goes back a few years as you mention below and Cessna is working on developing SID programs for most of their fleet. For the majority of operators complying with Cessna SIDs is not mandatory.

The recent issue with the C-425/441 SID surrounded the fact that those aircraft fall under FAR 91.409(e) and (f) and have to be on an approved maintenance plan. Most C-442/441are maintained on the Cessna factory plan, as these plans meet the requirements for 91.409. When Cessna updated their maintenance plan to include the SID these owners asked for clarification of their regulatory responsibility under 91.409, and in some cases the SID is required.

Because the Cessna 337 does not meet the requirements of FAR 91.409(e) a Cessna SID would not be mandatory for owners/operators of these aircraft. I've include 91.409(e) and (f) below. I hope this helps.

e) Large airplanes (to which part 125 is not applicable), turbojet multiengine airplanes, turbopropeller-powered multiengine airplanes, and turbine-powered rotorcraft. No person may operate a large airplane, turbojet multiengine airplane, turbopropeller-powered multiengine airplane, or turbine-powered rotorcraft unless the replacement times for life-limited parts specified in the aircraft specifications, type data sheets, or other documents approved by the Administrator are complied with and the airplane or turbine-powered rotorcraft, including the airframe, engines, propellers, rotors, appliances, survival equipment, and emergency equipment, is inspected in accordance with an inspection program selected under the provisions of paragraph (f) of this section, except that, the owner or operator of a turbine-powered rotorcraft may elect to use the inspection provisions of §91.409(a), (b), (c), or (d) in lieu of an inspection option of §91.409(f).
(f) Selection of inspection program under paragraph (e) of this section. The registered owner or operator of each airplane or turbine-powered rotorcraft described in paragraph (e) of this section must select, identify in the aircraft maintenance records, and use one of the following programs for the inspection of the aircraft:

Have a good weekend,
Leisha


Leisha Bell
Director, Aircraft and Environment

Aircraft Owners and Pilots Association

Ph: 301-695-2086

Fax: 301-695-2214

Leisha.Bell@aopa.org

www.aopa.org



Whether the FAA proceeds to require compliance by AD (as occured with the 400 series twin Cessnas), and/or whether insurance companies will attempt to encourage compliance, are different questions.

Therofer, it behooves us to pay close attention to this developing saga.