Sealed Struts

[sparky66]

We are doing the annual on our club 7AC, and are trying to address AD's and service letters. There is a service letter that states we should drill a drain hole in the front lift strut. We looked at the strut, and there isn't a drain hole, and we don't see where water could get in anyway. Were there different styles of struts? Do we still need to put in a drain hole on a strut that appears to be completely sealed?

[N86250]

We looked at the strut, and there isn't a drain hole, and we don't see where water could get in anyway.

Just like anything that has an opening to air, changes in barometric pressure will move air with its moisture content in and out of the strut. And changes in temperature will cause any moisture on the inside of the strut to condense. Just like a half full gasoline tank collects moisture from condensation over time. Cold airplane, warm air, condensation(sweat) on the outside of the airplane. Condensation on the inside of the parts too. jrh

[MikeB]

Although I can't prove it, somewhere back in my memory, it seems that particular SB was dropped (the drilling). Probably when the sealed struts came out. I have four new lift struts from Univair still in the crate but I don't believe they are drilled. I know the new struts I put on my Champ (from Safeair) are not drilled. I suspect that's a old bulletin but someone might jump in and prove me wrong.

Having said that, it pays to watch the bottom of the old struts as I've seen a couple rusted through. Some have not been changed since the plane rolled out of the factory in 1946.

MikeB