Questions from a Potential 337 Buyer

[Denhamblin]

Originally Posted by Justadude

In my search for a 337, today I looked at a 1975 P337 that was in very good shape, good times on airframe and engines, and well equipped. The plane had the engines reman'd and all upgrades done in 204 by the Rocket Aircraft LLC. To my understanding, many were part of Riley back in the day.

The big question for all of the knowledgeable folks on the board is what to do with the AE wing tanks (plus fuel xfer/fuel dump equipment) that Rocket installed in 2004. I've read all of the treads on this board, plus anywhere I could find information. A lot of emotions to say the least. Is it best to walk away from this plane, insist that the seller go through the removal and final AD inspection, or negotiate in a $ value to accommodate the removal (and what would/could that $ amount be?). As an aside, I saw no skin cracks or smoking rivets when inspecting the top of the wings.

Appreciate the help here. I really like what these planes can represent in usefulness, while appreciating the complexity and financial commitment required.

Thanks in advance,
Bob

Hello Bob,

The 1975 models should have the factory long range tanks (150.6 total capacity) as standard equipment (some call this the "long" wing). The wings in these aircraft are stronger than the earlier models. This is because they have "hat" type stringers that extend out to WS 170 (maybe it is 177, I don't recall exactly). At that point they splice into a "J" stringer. On the earlier models this transition occurs at WS 150. I do not know the details of the AD that affected those aircraft modified with the AE extensions but I can say that aircraft modified with Flint Tanks are not affected if they have the factory long range tanks.

One question I have is if the aircraft you are looking at had a gross weight increase over 4630 (4700 for turbo). I believe with some engine mods you could get the gross weight up over 5000 (I want to say 5240 for some reason). If it had a GWI and was operated above 4700 then I would have some concerns about the wings as my engineer didn't think that would be possible even with the "long" though he did not do calculations for a gross weight over 4700.

Another question would be whether the aircraft had winglets. Winglets can increase the load as well. We didn't look at that either since the Flints don't use winglets.

Again, you would want to follow the AD that affects the 337s modified with the AE STCs and, while I do think I have a copy of that at the office, I'm not sure of the details. I would expect that AE issued a SB to deal with that AD so you would need to follow that as well.

I can say that with the Flints you do not need to remove the tips. If you have the "short" wing you need a structural retrofit kit which beefs up the wing at WS 150 (a doubler at the rib at WS150 which spans about 3.5" inboard and 5" outboard, 3 stringer doublers that extend out from WS150 to WS177 and a forward spar doubler that does the same). These doublers are put on the exterior of the top wing surface and are provided for free for those aircraft modified before the issuance of the AD that affected the Flint modified aircraft. Labor costs are not included and you are looking at 30-35 hours to install the structural retrofit. If you have a "long" 337 with Flint tips there is no action necessary. Please note that with the Flint tips you have a limitation of keeping 12 gallons in each tip until your gross weight drops below 4330.

I hope this helps.