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Improving the Main Landing Gear in VariEzes and Long-EZs
Several mods will help transfer the landing gear load to the fuselage structure. If you are too far along to do them all, do what you can, as some help is better than none. You'll be limiting the number of weak spots. I'll list them in construction order.
Back when building the fuselage sides, consider substituting a hard wood (oak-maple) for the spruce when making the LWX & LWY hard points. The soft spruce easily crushes when heavy landing gear loads hit the soft spruce/AN-4-16A joints. The crushed spruce causes loss of clamping force and starts the gear movement process. Loose extrusions also allow bending of the AN-6-80A mounting bolt. Once bent, the main wheel geometry gets misaligned and when that long bolt gets bent, it is EXTREMELY difficlult to remove. View attachment: flox donut2.JPG
Plans call for AN 960 washers to be used under the heads of the 16 AN-4 bolts extrusion mounting bolts. They have proven to be too small to adequately spread the bolt loads to the soft spruce hard points. It would be far better to use wide area washers (AN-970) so as to spread the compression loads. They are used only under the bolt heads.
If you have a project, it is wise to replace those washers if the fuselage has not been painted. You will have to remove the bolts and do a local glass repair over the bolt head area. If the 16 extrusion mount nuts were over tightened and the spruce hard points crushed, you may have to use shorter bolts to get proper clamp up length.
Note how the AN-4 bolts in the pic all show excessive threaded area. Typically there will be only a few threads exposed. That excessive thread area is probably due to over tightening during construction. This pictured project is being buit with a serious landing gear flaw and will probably result in early landing attachment problems. These are quite difficult to fix on a flying airplane. Look for that thread clue when buying a project or even a finished airplane.
The aluminum extrusions were originally constructed with no bushing to transfer the long 3/8" diameter 80A bolt loads to the extrusion. The softer aluminum extrusion's bolt hole soon gets hammered out of round allowing strut movement . That can be noted by aluminum dust around the bolt/extrusin joints. The fix, which was later accomplished on most extrusions, is to install a flanged bushing in the extrusion. That spreads the load on the extrusion holes and allows longer life.
The strut is attached to the landing gear tab & extrusions via the 5/8" diameter LMGA assembly. Be sure to assemble it and the 80A bolt with anti seize product. Steel bolts and steel bushings in a hidden potentially damp area will soon grow fast and will be a nightmare to remove or even tighten later.
The LMGA assembly is attached to the strut with a drilled hole process and flox. That is a failure area which can be easily eliminated by inserting a flox donut between the strut tabs and the extrusion face. Note the large space between the inside of the extrustion and the outer faces of the strut tabs. see flox donut2
Any sharp impact from landing load or hitting a chuck hole can crack the LMGA assembly loose from the strut tabs and start a sliding process that gets worse with time. The fix is to grease the steel parts area so you can get it apart at a later day and construct a flox donut to fill that void between the tab & extrusion. The donut is loaded in compression and not a structural member so don't panic about trying to get the cleanest extrusion or tab face when installing the donut. It is a sloppy process. I lay out a piece of Saran Wrap about 2" wide and 6-8" long and put a blob of flox in the center about 1" wide and 2" long. Then lift both ends of the Saran up with the flox touching the bolt & bushings and sort of pat the Saran around the bolt so as to form a hard donut that will spread the impact from tab to extrusion faces. This will help prevent the landing strut shock from breaking the LMGA assembly loose from the strut tabs.
These changes are easy and fast during construction. If not caught then, they have proven to be airplane grounding and major repair issues later.
CSA Newsletter Editor/Publisher
Long-EZ N9TS, 4000+ hours with NO gear problems