Forum: F-16 Design & Construction

How do the new production jets address the issues of wing life from earlier models?

The F-16 overall is a great jet, yet there is certainly a history involved with earlier models. Not unheard of in other plane types either. To where the original requirement for a "light weight figher" ends up picking up the slack from the F-4 and of course carrying lots and lots of stuff on it: 2x Mk84s, drop tanks, A2A missiles etc. on an almost routine basis.

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The F-16 ended up carrying MORE than the F-4 actually. And the wing is stressed for an 8,000 service life. The wing is put on a test rig and a simulated life is simluated by a factor of four. Thus the wing is subjected to the equivalent of 32,000 hours.

Well from what I am seeing here at Hill and what I am gathering from other bases the wings on some of them are not even making it to 4000 hrs. We do a 900 hr inspection on the wings and LEF drive system and we are finding corrosion in the 370 attach point rib box severe enough to cause wing changes now. The jet we are phasing right now has a bad right wing now.

Rigo

Hey thanks! Interesting stuff. On the average, how many hours before you send a jet up to Hill for depot work?

Rigamortis, can you comment on the source of the corrosion? Is water getting trapped inside the wing or is this a dissimilar metal problem or... ???

What we have found out from just pulling out the ext wing tank mounts is that they are sealed with what we call B 1/2 . It is a black colored 2 part sealant we use all over the jet. We have noticed that some of them are not sealed enough so water seeps into the space between the mount and the rib box it is mounted in.

The box is made of cast aluminum and the water causes the a reaction between the mount and the box causing corrosion in the aluminum, usually down right around the neck area of the mount. After the mount is pulled and the area is stripped by sheet metal of primer (what little is left!) metals tech ( formerly machine shop) has to check for corrosion and then remove any corrosion they find. This gets tricky since they can only go .160 deep max. when they are done it looks like a dentist went berserk with a drill.

Rigo

Rigo hit it right on with that answer I couldn't have put it any better myself. If the corrosion was more than could be honed out the wing has to be replace and I believe the box is replaced at depot. I know at Shaw we were getting some of the same wings we removed for corrosion back after they were repaired by depot. Only to put them on another jet. Odd.

Dave

This might sound obvious but to units that are close to the salt air (Kunsan, Misawa, Florida etc ) suffer this problem more than lets say a unit in San Antonio, New Mexico, Nevada?

Rigamortis, Dave, thanks for the corrosion info. Does USAF have wash racks like I've seen for some navy bases? The ones where they taxi through a rack that sprays the plane from all sides? I can see how that might introduce water to the area you describe.

They do have them at some of the bases, I know Misawa and Kunsan have them but unfortunately the one at MIsawa is meant for the P-3's that the Navy rotates in and out of there. I was told they tried them once with a Viper and it cold soaked all the cannon plugs in the wheel wells, the one there sprays from the ground up so the Orions get their bellies washed free of salt, the one Kunsan though is an arched affair that sprays down on the a/c so they use it alot there.

As far as salt goes the reason why corrosion is a problem here at Hill is the fact of the Great Salt Lake being right next to us but the main problem with wing fittings corroding is that paole didnt use enough B Half to seal the wing mount fittings when they were pulled last. the water just seeped right in them and was then trapped. When we do them now we use so much it oozes out of the seams around the fitting and then we seal the top with it so no water can get in.

The last one I pulled (last jet we did about 2 weeks ag ) I had rusty stagnant water run out when I popped the mount free. As long as the sealant is done right no water should get in there, plus our birds here sit out in the elements year round.

Rigo

Forum: F-16 Design & Construction

Wing Life