What mechanism towbarless tractors have while towing the aircraft when there is a risk of steering failure?

Question

like normally towbar tractors if there is a steering mechanism failure,towbar will break to prevent damage to nose landing gear.but in case of towbarless tracors,its holding the wheels from both sides tightly..so how do it work when ders a steering mechanism failure evenif the steering pin is installed??

Answer 1

Seadog in correct, Even if something other warning system is used, shear bolts are installed so they break away without damage to the gear, usually.

Answer 2

I am going to assume you mean the small sled looking tugs they have at commercial airports. These are made by a company called Lektro, I have spent many hours on them.

There are two ways of using the equipment, the right way, and the safe way.  The right way uses the tow strap to pull the nose gear onto the cradle, then the side bars are secured against the tires. This prevents the airplane from moving in any direction. If the operator were to turn the tug too far there is nothing to prevent damage. The smaller lektro's do not have anything that would even alert the operator of excessive stress.   I do not like using a lektro the right way (unless its wet out, in that case I just be sure not to over steer) The safe way is to only use the tow strap, and keep it slightly loose. If the tug is turned too far, the wheel just slips in the cradle and no damage is done. Not only is this safer, but it also allows an airplane to be turned much tighter.

Answer 3

The tractor has over-torque protection sensors.  A red light flashes in the cab of the tractor when a certain amount of force is reached letting the driver know something is wrong, like forgetting the steering bypass pin.

If the driver keeps going and reaches a slightly higher force, the tractor shuts down and the brakes are applied to prevent any damage to the plane or the tractor.  Since there's no towbar, no towbar damage or shear bolts breaking.

This is assuming you're talking about the towbarless tractors for bigger planes like the B757, B747 etc.

Answer 4

Good Question

I was a Crew Chief On the KC-135R Airframe for years in the air force so i have towed a few aircraft. And while i do not know all the specs, i can formulate a fairly educated guess.

Think of it like this. In a conventional tow bar, the bar couples to the piece that attaches to the steering collar with a set of sheer bolts that are designed to sheer when the back pressure reaches x amount. ( the amount of pressure needed to sheer the bolts is airframe specific.)

I would say that the barless tractor would have a similar setup (at least in theory) I think it couples to the nose gear with a variable pressure setting that could be adjusted by the operator depending on the airframe he is towing, and should the back pressure reach (x) amount the connection to the nose gear would pop lose, no harm done.