Wind Spar Inspection
 

I heard recently from someone selling a Skymaster that all Skymasters must have a wing spar inspection every 500 hrs. I had not heard that before. Why is it that they need a wing spar inspection at 500 hrs.?

Wing Spar Caps and Web Doublers
 

Hew,

Not too much to worry about, but the AD does cover the 336 models, 337's, and the P-models as well, but with different affectivity times as to when the inspections are to begin.

The purpose of the AD is to detect cracking of the wing front and rear spar lower caps, front spar web and web doubler, in the vicinity of where the struts attach to the wing. The inspection process involves using an eddy current probe and dye penetrant, as well as the old eyeball. Of course, if any cracks are discovered, the parts must be replaced before the airplane is returned to service. So far, I've not heard of anyone having to replace the subject parts, but given the prices Cessna has been charging lately for things, this could be a rather EXPENSIVE proposition.

Cessna Multi-Engine Service Letter ME78-2 addressed the issues on February 13, 1978, so this is not something new for Skymasters. However, the original AD that came out was 73-04-03 with a later amendment, 76-10-11, and then the current amended AD, which is 78-09-05.

The affectivity and "compliance timetable" are based on the type of aircraft operations and total time in service by model. For example, non-pressurized Skymasters are generally not affected by the current amended AD until 5,000 hours total time in service have accumulated, and the initial inspection must be accomplished within 25-hours time in service after the effective date of the AD, with 500 hour repetitive inspections.

Since the P-model has a beefier airframe and generally isn't subjected to low-level contour operations like pipeline patrol or police patrol work, the P's aren't affected until 10,000 hours total time in service. And then, within 25-hours time in service after the effective date of the AD, and the same 500 hour repetitive inspections.

Mind you, this is my read of the AD, and like anything else, it would behoove the reader to check out the facts and actually obtain the necessary paperwork from Cessna and the FAA to get the straight skinny.

So, there is something to be said for searching out a pristine, low time airplane. Personally, I've never heard of a 337 having cracks as per the AD, so I think this boils down to Cessna doing a "CYA" Operation with the FAA's blessing, i.e., "cover your _ _ _ " type of thing. But that's my personal opinion based on other known facts. In any event, the AD is issued for safety reasons, and it is a mandatory thing.

Overall, I'd say the Skymaster, at least the later model P337 series have a minimal number of AD's to comply with, as compared to other airplanes. Ever look at the AD list on a Piper? Yikes.

Hope this helps.

SkyKing

Re: Wing Spar Caps and Web Doublers
 

I agree with you SkyKing.
Mine has 7,800 hours on it, a 69 - 337D, and we had to do the spar AD this annual. Aside from being costly, and time consuming, it is a bit frustrating as an owner to see some guy show up, wave his wand around for 15 minutes, and you get to part with $$$$ for him, and even more $$$$$$ for the mech who preps it for him.

Does anyone know of an actual incident?

Skyking's answer is generally correct, but I think that normally aspirated models which were used for low-level contour operations like pipeline patrol or police patrol work need to perform the initial inspection earlier than 5000 hrs -- I think like 3000 or 4000 hours. Maybe someone will jump in and confirm.

Ernie

Checkout Skymaster AD's here... Including all about the wing spar.
 

What a great freakin' web site
 

I never fail to be impressed with the quantity and quality of the information available on this site. This may be a bit over the top but true nonetheless: it renews my faith in America. Where else in the world would average citizens have the freedom and wherewithal to pursue and refine there interests and passions? My parents were Scottish immigrants and this country just blew their minds.

I'm looking forward to the talk on Skymaster ADs at PWA. As well as the talks on flying to Mexico and Europe.

I'll be looking to hitch a ride on the fly out if anyone has room ;-) More than happy to cover fuel and maintenance expenses as appropriate. If there is a 336 with an extra seat, I would particularly love that.

Thanks to all for allowing a neophyte to the dance.

Hugh

Ernie is correc-to-mundo
 

Yep Ernie... A 'Gold Star' for you. Cessna and the FAA strongly recommend the lesser time as you have duly noted for those birds doing the 'How Low Can You Go' bumba song and dance.

SkyKing

But I'm not entirely correct. I went to the AD and, as Skyking says in the message right above this one, doing it before 5,000 hours is not a requirement but a recommendation (the exact words in the AD are: "Cessna recommends and FAA strongly urges").

Ernie

I am in the final stages of purchasing a 73' 337 Pressurized w/ about 2500 TT - I was under the impression the Spar inspection was due at 3000 TT on this aircraft. (based upon my read of the AD-Log with the aircraft, and other research) From my read of this thread, it looked like some of the P-Models may have more time? Perhaps that is only on later P-Models? In any case...

I would like to get some idea what I am in for financially in 500 hours if this inspection is in fact due at 3000 TT. What experience have other member had with this process?

NDT of the 3 bolt holes, $400. Dye penetrant of the rear spar, $1400. P models do not need any spar inspection until like 9000 hours. Stronger spars, not so severely affected by the AD.
The biggest charge is labor. If there is a hole on the top of the wing, they can get to the nuts without removing the tanks. To do the dyepenetrant, they have to remove the top of the wing.

Don't worry... Be Happy if it's a "P"
 

Pat... Not to worry on any of the "P" models (1973 thru 1980), unless by some queer thing the one you're looking at has been playing La Bumba at low-level contours. Larry is correct... the AD doesn't kick in until after 9,999 hours TT.

SkyKing

Is the O2-A included as it too has an extra and beefed up spar?Thanks
Tom

O-2A is most definitely included, particulary since it was subjected to lots of high G maneuvers. Falls in the same classification with arcraft used for terrain following. Good idea to do anyway, considering the things most O-2s went through.

My '67 Turbo model (not P) required it at the 5000 hour point. So it sounds like only the P's that haven't been doing the low and slow hard stuff are OK for longer than that.

I have a 1973 P model that was used as a fire fighter, after speaking with three different IA's all agree that Note 1 of the AD applies only to non-pressurized 337s. One says there is no reason to do the inspection until the airframe has 10,000 hours, the other two believe the best course would be to voluntarily begin the inspections at the 5000 hour mark to be on the safe side. It is my understanding that the P has a stronger airframe, and the latter recommendation seems safe and reasonable. I just wanted to get some of your thoughts. Borden
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M2B15