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Replacing Broken Gear Mount Extrusions
The strength of the landing gear on the Long-EZ is legendary. There are numerous accounts of EZ's being dropped hard onto a runway, landing off airport, etc., where the main gear has held firm with no apparent damage. (See "The Flight to Remember" here in the "Articles" section.
The Long-EZ in this article was first flown in 1987. Several people were sequentially involved with its construction over a period of about 3 years (remember this as you read on). It has led a rich life, even traveling from San Diego to Ireland and back, experiencing a very hard landing in severe crosswinds in Greenland.
Several years ago it was noticed that the airplane did not track perfectly straight when taxiing and the right brake seemed soft. Excessive brake use eventually softened and damaged the gear leg. This was repaired but the braking still felt soft. A brief inspection of the gear mounts at that time did not reveal an obvious problem and it was flown regularly until recently. On a subsequent flight it was reported that the right rudder seemed to freeze up, but it worked properly on the ground. Then a few months later, while heavily loaded with two people and a lot of fuel, it was observed that the main landing gear moved excessively when the aircraft braked to a halt.
A thorough examination of the landing gear fittings is difficult because they are located behind the rear seat bulkhead in the "hell hole". However, using a mirror and high intensity light it was observed that the gear was moving in the mounts when the plane was rocked, and the motion revealed a crack in the mount. This led to the difficult, but necessary, decision to cut into the fuselage to gain access to the gear for repairs. The following photos show what was found.....
The wings, canard and canopy were removed. Two substantial wood attachments were bolted to the wing fittings so that the fuselage could be rolled over (without damage to the strakes) onto sawhorses for easy access to the gear area.
A Dremel with a carbide bit was used to cut through the gear fairings and fuselage bottom.
This aircraft was equipped with a NACA scoop for engine cooling, so it was necessary to remove the non-structural skin and foam that formed it before cutting into the fuselage.
Then the fuselage was cut open to gain access to the gear mounts.
The damage was much worse than originally thought. The rear fitting was broken completely through! Even scarier, it was found that the same fitting on the other side was also broken in half. It is hard to believe that the plane had been enduring landings, possibly for several years, with these main supports broken.
The reported incidents of the rudder "freezing" while in flight were explained when it was found that the right rudder cable would often be caught in the broken fitting as the gear flexed. Apparently this was relieved when the aircraft weight was re-imposed on the ground.
Although harder to see, the mount on the other side was similarly broken.
The main bolts were removed and the gear was pulled from the aircraft. This involved significant effort to gain access through the rear seat bulkhead to pull the bolts.
This photo shows why the fittings broke. In a properly prepared fitting there is a single hole drilled to allow the rudder cable to pass through one side of the angle. Here it can be seen that there were two attempts to drill the hole. The first one (toward the top) was abandoned and another was drilled lower in the extrusion, actually creasing the other side of the angle. This weakened the fitting in an area of extremely high stress and the break occurred across the two holes. It is surmised that this extrusion was the first to break. The fracture was heavily oxidized and worn by repeated movement, indicating that the break had occurred in the distant past. These extrusions were fabricated and installed by one of the early builders, with the final owner unaware of the defective workmanship involved.
The second fitting broke in almost exactly the same place.
New fittings were fabricated, being careful to have smooth, beveled and rounded edges everywhere to avoid future stress fractures. It was also decided to eliminate the hole for the rudder cable and simply route it around the fitting. This aircraft has the brake cylinders mounted in the front, so the tension on the rudder cables is not substantial. In this photo you can see where the rudder cable was flattened when it was caught in the broken fitting. It was subsequently replaced.
The gear was remounted and found to align nicely. Although not shown here, aluminum spacers were fabricated to fit between the gear leg and the fittings. These were all rigidly secured into place with flox.
This article illustrates how important it is to fabricate parts exactly to plans. Poor workmanship demands that the part be immediately discarded, because severe consequences can result. This problem could have resulted in a badly damaged airplane and possible injuries to the occupants.
The fact that this gear did not tear off is a great testament to the phenomenal strength in this design. Even with both extrusions broken, this airplane endured many landings. How many more before it would have collapsed is anyone's guess.
If you are contemplating buying a completed homebuilt aircraft, be aware that there are many structural components that are difficult or impossible to inspect. You are relying entirely on the expertise (or lack of expertise) of the original builder. Be careful!