FAA Description of Airworthiness Concern: Main Landing gear tie strut

[3Dreaming]

3D, does your gear have a hole at the bottom of each vertical "V" through the round flange that the brake assy bolts to? It's covered if brakes are installed. They're on the axle side and above. Gary N36007

Anyway on my gear that was off while on floats I blew shop air through every access point and saw no rust emerge. Then I sprayed Corrosion X into every hole and rotated the gear to let it distribute. Won't replace any lost metal but it might arrest existing corrosion.

I don't know, but I can check tomorrow. If I don't forget.

[PA1195]

3D, does your gear have a hole at the bottom of each vertical "V" through the round flange that the brake assy bolts to? It's covered if brakes are installed. They're on the axle side and above. Gary N36007

Anyway on my gear that was off while on floats I blew shop air through every access point and saw no rust emerge. Then I sprayed Corrosion X into every hole and rotated the gear to let it distribute. Won't replace any lost metal but it might arrest existing corrosion.

[3Dreaming]

I have a set of gear here that I just checked. Both are drilled. I applied air pressure to the drain holes one was sealed at the top cluster, and the other was not. Where the bungees ride on the gear is a streamlined tube, that is open on the end towards the gear. That is where the air was escaping when I pressured it up, so that would be where moisture could get in. There would be no way of knowing whether it is open or not without having the hole to pressure it up. I suspect the reason for the service bulletin were because they were aware that some were open in that spot.

[PA1195]

On my Pre-War 1941 the three struts are potentially open in a couple of places to moisture, and another set I've seen from that build era was the same. At the junction ends where the bungees attach the three tubes welded in a cluster may be open and not sealed, my diagonal was for sure open (see below). Under the brake plate to gear flange were some holes in the lower two A-frame vertical tubes. If moisture gets into the three tubes from the upper or lower openings it can cause problems. Taylorcraft noted this and suggested drilling that lower diagonal hole to let it drain and not remain.

Ok, so now what? Removing the gear and tapping the tubes with the potential two opening areas down might inform as to corrosion. Blowing shop air into a drilled lower drain hole while still in place might cause corrosion to exit the diagonal near the bungees.

There was a local gear that failed on skis. There was corrosion where the two A frames (vertical and horizontal) meet at the gear to fuselage fitting junctions. Also, the diagonal separated at the lower end. A drain had been drilled but it went into the solid steel end and not into the hollow portion uphill. Gary N36007
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[SomethingScrewy]

I asked my A&P/IA to take a close look at my tie struts during the annual this year. They appear in good shape with no evidence of corrosion, as best we can tell from the outside. My tie struts do not have drain holes. We are not convinced that drilling holes would be beneficial, because these struts appear to be sealed (we do not see any obvious openings). If sealed struts are preferred for the wings and those do not have drain holes, then what is the logic behind drilling a hole in the apparently sealed landing gear tie struts?

Regards,

Lance

[Robert Lees]

The other reason for a bolt at the bottom of the tie strut is somewhere to attach the wheel spat bracket.

[waltermrich]

Thanks for chiming in did not know that.

[Hank Jarrett]

The reason for making a welded attach at one end and a bolted attach at the other is if welded at both ends the tube can be loaded in bending as well as tension/compression. With a bolt at at least one end the bolt acts as a pin and allows rotation eliminating any bending loads. If the tube doesn't get loaded in bending it can carry much more load for the same size tubes. It is the same reason most bridge sections are attached both pinned joints instead of being solid. On bridges they also add in links to allow for expansion and contraction of long sections but our gear isn't long enough for that to be as much of a problem. You would NOT want the support tube welded at both ends!

Hank

This problem is another reason we REALLY need a gear fixture. Minor axle misalignment can cause lots of problems on landing. Toe and castor of the axle can be critical.

[waltermrich]

Has any one heard of making a cable to tie the landing gear strut on each end incase of failure, the landing gear struts are definitely a concern on our 77- 78 tear old aircraft , I recently found rust on the lower few inches of the landing gear strut on mine , A repair will be in order with a sleeve over the lower end of the strut, but would that be considered a major repair, Any feed back, have to discuss this with my A&P and any examples of repairs would certainly help.

[bluerooster]

The one on my right gear was repaired by welding in a replacement strut. I was wondering why it was larger than the left side until I found the write up in the logs.

[steve canyon]

My A&P got 2 pcs. of streamline 4130 tubing 2 ' long each , 1 slightly smaller than original tube ID and 1 slightly larger than out side from Aircraft Spruce for $85. it was enough to repair both sides . I spent quite a bit of time trying to find some streamline tube same size as original with out any luck. We replaced bungees with winter ones since we had it apart and they needed replaced . I uploaded a tool I made for installing bungees. It worked real well.

[3Dreaming]

I have repaired some by replacing the lower end with the next size larger streamlined tubing using 1/2 of the splice and locating it near the top cluster.

[waltermrich]

That looks like and excellent splice, would you know where your A&P got the tubing for the splice and what size it is ? Thanks for posting

[PA1195]

Nice catch on the corrosion and repair. It's a credit to the A&P for actually repairing and not just demand a replacement gear. I have a similar repair from a dent on mine. In addition to internal and external corrosion that tubing can be subject to impact from gravel and excessive side loads. Any exposed metal should be promptly cleaned and primed/painted.

My suggestion is to blow through the drain hole and confirm air without debris exiting the tubing cluster under the bungees. I DON'T know if all three gear tubes are open at the upper cluster. I'd then spray preservative oil into the diagonal drain hole and upper cluster and position the gear to let it coat the interiors. There's likely another hole under the brake stuff above the axle where the two outside clusters meet. If there coat the tubing with preservative.

Edit: I believe the bottom bolt arrangement is for adding a support plate for wheel pants. The outboard end of the axle is threaded to accept a fastener for the pants.

Gary

[steve canyon]

Here's a couple more