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Ground Loops
How do we avoid ground loops?
A ground loop is an uncontrolled turn of rapidly tightening radius. It typically ends with the taildragger going backwards off one side of the runway. Unless obstacles are encountered, often no damage is done other than to the pilot’s ego and composure.
Unfortunately, obstacles are occasionally encountered, and in some cases a landing gear collapses under the sideward force. Sometimes the airplane tips forward and to one side, striking the wing tip and/or the propeller on the runway. Sometimes the airplane winds up on its back with considerable wing, tail, propeller, and engine damage.
In extreme cases, an attempt to fly out of the ground loop can result in a collision with some obstacle, or it can even terminate in a departure stall/spin crash, as seen in the accompanying video.
All ground loops are avoidable, and all taildragger pilots need to know how to avoid them. The bottom line is that ground loops can occur only while the airplane is decelerating during a turn. The turn puts the center of inertia, which is behind the main wheels, out of alignment with the center of resistance, which is normally half way between the main wheels.
With inertia (acting at the center of inertia) pushing the airplane forward, and with the friction of the tires on the runway surface (acting at the center of resistance) resisting the airplane's forward progress, the airplane wants to swap ends whenever the two forces get out of alignment.
Ground loops are easily prevented by eliminating either the deceleration or by keeping the forces in proper alignment. The deceleration can be eliminated simply by adding a little power. The forces can be kept in alignment simply by not allowing any turns. If an uncommanded turn is already in progress, the forces can be put back into alignment by terminating the uncommanded turn, initiating a commanded turn back toward the current direction of travel, and terminating the commanded turn when the proper heading is reached.
Fortunately, the reflexes required for instantly terminating turns can be learned while taxiing, because taxiing a taildragger tail-down is all about terminating turns. Whether a turn is caused by a crosswind gust or is commanded by the pilot, the turn puts the tailwheel out of alignment with the fuselage, where it tends to remain until put back into alignment by opposite rudder or brake. With the tailwheel out of alignment, the airplane will keep on turning until the turn is terminated by the pilot.
By simply taxiing and terminating a lot of commanded turns precisely on a chosen heading with rudder and differential braking, the turn terminating rudder reflex and the turn terminating brake reflex can be acquired. Once acquired, these two reflexes will automatically terminate uncommanded turns as well as commanded turns. The Art of Avoiding Ground Loops offers a series of taxi exercises to safely and incrementally develop these reflexes.
