Ground Handling

So far we have covered how the weather will affect an airplane in flight, how lift is generated, why a plane sometimes acts strange, and how control surfaces work. In the next section we will get into proper set up for ground handling and flight trim.

In order to get a plane into the air so it can fly it must first be able to accelerate down the runway until it reaches flying speed. Since MASH field has a grass runway, most of this discussion will be about a grass runway.There is an old saying among pilots "you don't have to take off but you always have to land" . Taking this into consideration, maybe we should hit on landing too. To start with we need to know where the landing gear needs to be positioned on the plane for the best tracking possible. In figure 1 which depicts a plane with conventional landing gear or tail dragger we see that the wheel center line is a small distance in front of the center of gravity or cg. It is obvious why the landing gear needs to be placed here. The question is, how far in front of the cg should it be for proper handling. As a rule of thumb, it should be just far enough in front of the cg to prevent nose over for the surface you are flying from. Since MASH field is grass, we usually have to place the gear a little more forward than if it were a hard surface. As the gear is moved more and more forward, it will create two problems. On take off, if the gear is mounted too far to the front, a pendulum effect will set up causing the tail to swing back and forth making a straight roll out almost impossible. This happens because the plane wants to rotate around the cg but the wheels, being attached to the ground, are forcing the plane to rotate around them. This places a large amount of mass behind the point of rotation such as a pendulum in a clock. To quote another one of Newtons laws, "A body in motion tends to stay in motion until an opposing force acts upon it". In our case the opposing force is the rudder. We find ourselves moving the rudder stick back and forth rapidly and sometimes make the situation worse. The second problem created by a conventional gear being too far forward is landing bounce. What happens is that the main gear will touch down and with all that mass behind the gear (remember Newtons law) the tail wheel will go crashing to the ground. This will increase the angle of attack of the wing and the plane will try to lift off again. Not having enough speed to fly the wing will stall and the main gear will come back in contact with the ground starting the process over again. The plane will go hippity hop down the runway until it has finally slowed down. Some of those beautiful take off and landings you see at the field with tail draggers are only partly pilot skill. The rest is in proper landing gear set up. This is especially important to the beginning pilot as he should have a plane that will handle as close to perfect as possible. Next Page-->