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Sunday, January 4, 2009

Tailwheels! The Critical Link


Learning to fly tailwheel aircraft will make you a better pilot and be richly rewarding, but you must pay attention to the most critical part, the tailwheel assembly and the springs.

Flying a tailwheel aircraft is exactly the same as any other airplane - in the air! For takeoff, landing and taxiing however, it is exceptionally different, and it takes a refined set of skills to safely and comfortably operate one on every flight. But before we get to the skills, let's look at the components. From my experience owning and operating an Aeronca Chief for about 400 hours and teaching many others to safely operate their own tailwheel aircraft, there are several critical areas to examine.

First, look at the springs. The illustration shows compression springs installed, and typical tension springs not installed but next to the compression springs for comparison. You should use compression springs, for several reasons. Compression springs in their unactivated state, or when the rudder is neutral, are not applying any force on the tailwheel. They only apply force when the rudder is moved left or right, and then only on the side of desired movement. Tension springs, on the other hand, apply tension all the time, so if one breaks, (and tension springs are typically more inclined to occasionally break) the broken side whips free and the tension on the other side pulls the tailwheel to the side. Not good at critical points of a landing or while taxiing! Compression springs also give better handling. When you are taxiing with a tension spring, and you push rudder, it stretches the spring and the wheel thinks about moving then responds, in a springy sort of way. When you do the same with compression springs, the response is tight and immediate, which means as pilot and operator, you get immediate feedback as to whether you need more or less rudder input; you don't have to wait and see what will happen. Also, compression springs are typically thicker. Thicker metal outlasts thinner metal every time.

Next, the wheel must track straight and sit straight on the ground. A worn wheel where one side of the tire is angled and higher than the other, is a sure sign of a badly angled wheel, and while this can be compensated for with rudder pressure and brakes, why do that? It is like driving a car that's out of alignment. Most tailwheels on antique aircraft and some newer aircraft that I have seen have some misalignment and tracking problems. If you have any doubts about your tailwheels alignment and tracking, have your A&P check this out thoroughly. Since many older tailwheel aircraft have the same assembly they've had for 40 years or more, you probably should just buy a new tailwheel assembly. They are only a few hundred dollars, and the performance and peace-of-mind benefits are immediate and well worth the cost.

The next step is to examine and restore every component of the steering system. Those tailwheels are tiny, in comparison to the rest of the aircraft, yet they take the most beating. They are also the most exposed to weather and since the plane tilts 'downhill' towards the tailwheel, when they are sitting on the ground all condensation and rain runs down and drips on the components. When I say restore all parts of the steering system I mean start at the rudder pedals. Look at the bearing surfaces. Replace the rudder cables with new cables; I prefer stainless steel, since it is more corrosion resistant and part of the cables do run to the outside of most tailwheel aircraft. Check the cable guides along the entire path, they must be smooth and straight. Check the exit pat through the fuselage, there should be the smallest hole possible, it should not rub, and it is best if there is some type of shield to reduce the chance of bugs or moisture getting inside. Check the bearing and attachment points at the rudder horn, the entire system should be in good shape, not loose, no corrosion, and the bearings should be in good shape. Any bolts should be safety wired. The compression springs should be well attached to the rudder horn, and should have no slack and be equally taught going back to the rudder steering assembly. If you pay attention to all these areas, you will know your aircraft at a new level, and you will have a new sense of security and accomplishment as you operate your airplane.

It might be useful for you to know how I came to this position on tailwheels. In the late '80's I bought an Aeronca Chief. It had flown for years, successfully, yet the previous pilot just got used to the tailwheel quirks and foibles. One day I was looking closely at the clevis bolt connecting the rudder cable and there was a small spot of brown. I 'scritched' at it with the screwdriver in my hand, and instead of it cleaning off, like I expected, the clevis snapped in half! It was corroded nearly to the core and their was no sign of that on the exterior. This is what sent me down the path of straightening and replacing everything, and it was a fantastic decisions. For only a few hundred dollars and a weekend's worth of time, the steering immediately improved, tight turns were suddenly easier and did not need brake-assist, and the peace of-mind was very good.

If you came to me and asked me as an instructor to teach you tailwheel flying, (I am available, by-the-way) This is the first conversation we would have, as we looked closely at your tailwheel.


Onwards & Upwards!

Rob Bremmer

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