Tuesday was different by design. It was the long awaited day that I would torch parts of my airplane until they were red- hot, and bend them with a four foot lever bar. Over the previous days I had consulted all my acquaintances who might have had some experience with this sort of challenge, and Monday I finalized my plans and assembled all the necessary equipment. I had come to this point only after great deliberation, and the grudging acknowledgment that landing my plane on pavement was not any fun.
The problem was that the main wheels were slightly pigeon- toed, and pointed a few degrees inward from straight ahead. It makes the plane unstable because a slight turn after the plane touches down adds to the traction of the tire and makes the plane want to turn even more strongly in that direction. The right wheel aims slightly left, and a left turn loads the right wheel more heavily with centrifugal force and encourages the turn to tighten. It is a case of having a tiger by the tail, and it is worse on pavement, where traction is greater.
Even at its best, the tailwheel landing gear is unstable in the same manner as a tractor trailer combination. The center of gravity is located behind the decelerating force, and will always seek the natural equilibrium of swinging around to precede the drag. Tractor trailers jack- knife and tailwheel airplanes ground- loop.
My goal was to make my airplane's main wheels point very slightly outwards. Aimed in this fashion, a left turn would add traction to the right wheel, which pointing slightly left, would tend to dampen rather than aggravate the tendency to turn. The gear is still unstable, but at least it would no longer generate its own turning tendencies.
The torch- and- lever method of aircraft repair is by nature imprecise, and seemingly out of place in the genteel 90s, but fifty years ago when the plane was new, the technique was already old. The procedure was explained to me by a fellow who did it after a landing accident, and another fellow told me of doing much the same thing with a size 12 boot and a longer lever bar. The best story was from a man of great experience, who told me how he removed the gear legs and rewelded and machined them in carefully fabricated jigs. He did this twice, and was unsuccessful on both tries. He stated that as soon as the plane is out of his basement, he will fix the landing gear right... with a torch.
It is a simple, but tedious process. A reference centerline has to be established on the hangar floor with a plumb bob hung from the middle of both ends of the fuselage, and snapping a chalk line between those points. Straight edges are then placed fore and aft along the outside faces of the tires, and the locations of each straight edge transferred the floor, just as the fuselage centerline was. Accurate measurements of the tire's aim relative to straight ahead can then be made.
We spent six hours jacking, heating, bending, cooling, measuring, and then doing it all over again because it didn't turn out right. The right side was OK after the second try, but the left side took three tries before it too, was acceptable.
The proof was in the pudding, as they say. We put it back together and I taxied the plane to the runway, gradually feeling out the directional stability as I went faster and faster. Just because I thought that we had fixed the landing gear was no guarantee that we hadn't actually made it worse, so I approached the test flight with a bit of caution.
Out on the runway, I accelerated at less than full power so that I could feel the plane as the speed built up more gradually. After the plane lifted off, I cut the power, drifted down, and landed uneventfully. From there, I made a normal takeoff and came around for a normal landing. My able assistant then made several more uneventful takeoffs and landings while I watched.
As I have said before, I am partial to that airplane, and it was an unusual treat to view its flight from the ground looking up. No Wichita spam- can, it has pleasant and distinctively classic lines, and I watched and listened with delight as it circled the airport. As much as I enjoyed watching the plane, the real pleasure was knowing that a dreaded but necessary job had been successfully completed, and that I'll be flying the plane more often now.
To contact Bob Tilden, send an e-mail.