July 2003Departments

Flying Smart : What It Looks Like

Tow limits

Graceful as they are in the air, airplanes are trucks on the ground - slow to respond, difficult to steer, and even more difficult to push. Backing an airplane into a tight parking space using a tow bar is an exercise in trial-and-error steering and plain old hard work, especially if you are pushing solo.

Directional control should not be your only airplane ground-handling concern. Take a close look at the nosewheel strut on the airplane you fly (if it has tricycle landing gear). Most have two small metal "ears" on the strut assembly, with a metal tab or protrusion placed between the ears. These innocuous (and on most aircraft, grimy) parts play an important role in ground handling because they set the tow limits of the airplane.

The arc between the two ears defines the turning radius. It may be as little as 20 degrees either side of center, or as much as 55 degrees or more. The turning radius is limited by the design of the nosewheel steering mechanism.

The ears and tab on the strut assembly are supposed to prevent you or the FBO line person from exceeding the turning radius, a mistake that could have the expensive result of damaging the steering mechanism and nosegear.

It's not likely that you would be able to oversteer - exceed the tow limits - when using a tow bar to maneuver the airplane. It is relatively easy, however, for someone who is towing the airplane using a tug or tractor to turn too sharply and bend or break one of the ears on the strut assembly or the tab that the ears impact at the limits of the turning arc.

Next time you preflight the airplane, make it a point to closely examine the nose strut to determine the configuration of the steering mechanism and the condition of the tow-limiting components. Check the pilot's operating handbook for specifics on tow limits, and make sure that anyone who tows the airplane is aware of the limits and observes them.