Cessna C337 SID

[Roger]

Do to an AD I had to remove the rudder shaft in my Navajo because of an inspection requirement for possible corrosion. This is a long vertical tube in the tail, that was sealed at the bottom. Over the years they would at times accumulate moisture and potentially corrode at or near the bottom. Had they been made with a hole in the bottom they would have never held moisture and this would probably never have come about. During years of Navajo aircraft maintenance, A&P's around the world had reported this occurance often enough that the inspection AD was eventually put in place. So of course there are issues in the design and manufacture of virtually all things that can possibly fail, and or "go bad" over time, but it isn't "time" alone that creates the problem.

Our questions about the proposed SID with the 336/337 isn't "if" we should be concerned about safety, it is "if" there is a demonstrated real use observation of a failure to a system or component that can be expected to be found in even a small percentage of the fleet. If not, then move on to the next model.

I'm quite sure you can make a fatigue failure computer program do just about anything, if your motivation is to "do something", but that's a far different thing than demonstrating real life components failures in the fleet.

Have there been any Service Difficult reports or have any A&P's reported real life issues with the area in question, or is this entirely a Nerd generated computer simulation?

[WebMaster]

Originally Posted by Roger

Have there been any Service Difficult reports or have any A&P's reported real life issues with the area in question, or is this entirely a Nerd generated computer simulation?

It's worse, Roger. There are no Service Difficulty reports, and there is no computer simulation. It's an engineer saying, "we ought to do this".

Think about it, and we have, all 0-2's were based on 337's, and in all the time in SE Asia, and other activities, the only time a wing failed at the fuselage attach point was when it was hit with a large caliber shell, or a missile.

Cal Fire used them a lot, and there was never a failure at the fuselage attach point, or the wing strut attach point.

[hharney]

Cessna did not use any computer based analogy to provide any rational to the proposed SIDs. Cessna says that all proposed documents are based on SDR information. There are NO SDR's that relate to the wing/strut attach points. This is the main issue with these specific proposed inspections. Cessna's opinion is that because the aircraft are over 20 years old, they need a routine checkup in these areas to determine if there is a potential problem. The red herring is that the process they require will necessitate removal of the tail, then the booms and finally the wings to perform an eddy current inspection on the attach points. Unless someone comes up with some kind of device that can safely allow the bolts to be removed without removal of the tail and booms, the cost of this inspection is huge. Then you have to take into account the damage that will be subdued to aircraft when non-qualified shops try to perform this inspection. There may be no damage to any Skymasters out there right now but there will be once shops start to perform this inspection.

Don Nieser has even gone as far to search all the military SDR's for the aircraft and I understand that there is nothing in that data base also that would point to a problem. The aircraft is just overbuilt in that area and there are other related components that would fail first before these attach points would be a problem. We addressed this with Cessna but the engineers just think that it's a good idea to inspect these locations. No basis, just a good idea.

I suggested several times at the meeting in Wichita that Cessna should soften these inspections to some type of visual without removal of the bolts. All reports of these inspections could be sent in as information to determine if there is a problem. I don't know if that was the best alternative or not for us because there is still no rational for the inspection.

[rschimizze]

I have a 6mm diameter articulating borescope, 3 meters in length that I use for failure analysis work. I am sure it could be wriggled to the area in question and get a very good look (photos and all) at the fittings. If those joints appear pristine then I would be very surprised to find anything more seriously wrong, given the lack of documented historical problems. This seems to me to be a more practical method for performing field examinations of otherwise good aircraft, but as others have stated Cessna has no motivation to be practical to the benefit of the Skymaster community.

[skymstr02]

With some minor disassembly of the wing fairings, the attach points are visually accessable, so the borescope is not necessary.

What you won't see are potential cracks emenating from the bolt holes, or corrosion that may be hiding in the bolt holes, or the laminated layers where the outer wing spar mates with the center section carry thru.

[Skymaster337B]

I have a good idea too -- since Cessna can just come up with good ideas. It seems to me that Cessna is admitting to gross negligence in the way they designed and built the Skymaster. I know that aircraft manufactures are protected from suits on airplanes older than 20 years old, in the U.S. But I don't think they are protected in a case of knowingly producing a faulty product at the time and only now admit it today. Perhaps a motion for discovery is in order to determine what they knew and when they knew it...i.e., engineering data. I'm sure Cessna wouldn't like that one bit.

[tropical]

Perhaps Cessna should consider a program to buy back the 337's and destroy them.

[John Hoffman]

Originally Posted by Skymaster337B

I have a good idea too -- since Cessna can just come up with good ideas. It seems to me that Cessna is admitting to gross negligence in the way they designed and built the Skymaster. I know that aircraft manufactures are protected from suits on airplanes older than 20 years old, in the U.S. But I don't think they are protected in a case of knowingly producing a faulty product at the time and only now admit it today. Perhaps a motion for discovery is in order to determine what they knew and when they knew it...i.e., engineering data. I'm sure Cessna wouldn't like that one bit.

This is exactly where I am on this Cessna proposal - if they want to hide behind the protection they got for legacy planes then they are asking for a reopener on the whole thing if they want to impose new inspections on those planes. That is - if the tests and exams are performed then Cessna steps in and assumes responsibility for those planes.

[Skymaster337B]

It sounds like Cessna is assuming liability for these planes...or are they covering something up, such as a way to make $14 million on new parts? Either way, it is my understanding that under the old way of aircraft certification (CARs) the only thing mandatory are AD's. And that the maintenance manual published at the time the aircraft was built is the only other authority for required maintenance (other than the 100hr/annual)...periodic updates to the maintenance manual is informational only, if you chose to ignore them.

[John Hoffman]

Originally Posted by skymstr02

With some minor disassembly of the wing fairings, the attach points are visually accessable, so the borescope is not necessary.

What you won't see are potential cracks emenating from the bolt holes, or corrosion that may be hiding in the bolt holes, or the laminated layers where the outer wing spar mates with the center section carry thru.

Way back in the dark ages when I worked as a quality assurance engineer the team was constantly coming up with ways to perform NDE on new assemblies that were being designed as the plant was being built. It seems that 30 years latter there can be a creative examination designed for this application if it comes to that.