1 The development of towbarless aircraft tractors

For many years aircrafts have been moved on airports by special tractors. These tractors have to be ballasted up to 70 tons gross weight to get the required towing force on the ground, e.g. a B747 ("JUMBO" with a max. taxi gross weight MTGW has to be ballasted up to 400.000 kg). The linking between aircraft and tractor occurs by special towbars, each towbar matching a special aircraft type. These towbars are usually equipped with shear-pins to protect the aircraft against too high tractive or brake forces, i.e. when exceeding the max. forces the shear pin breaks and the towbar is disconnected from the aircraft! This is the reason why a "brakeman" has to be in the cockpit while towing an aircraft with a towbar. This "brakeman" has to brake the aircraft, which is not steerable in this situation because of the disconnected torque link or the open by-pass of the steering. While towing with towbars the max. speed is limited to a range of 8 - 10 mph because of the driving stability.

2 The advantage of towbarless aircraft tractors

All those well-known disadvantages can be avoided by towbarless aircraft tractors. By means of the pick-up device, which is located in the tractor's centre, the aircraft is seized on its nose gear tyres and pulled onto the platform. In simple terms you might say that the aircraft is "hitched up" and a backlash-free link is established between tractor and aircraft. By using part of the aircraft weight (up to 45 tons) to additionally load the the aircraft tractor, there is no need for ballasting the tractor when using this concept. This results in a deadweight of only 25 to 30 tons (instead of 70 tons for a towbar tractor). This direct and backlash-free link ensures that the combination consisting of towbarless tractor and aircraft can easily achieve speeds of up to 30 km/h. You can completely do without a brakeman because the towbarless aircraft tractor is dimensioned so that the tractor driver can handle all functions such as loading and unloading of the aircraft as well as all ground movements from the driver's cabin as a "single operator".

3 The first Goldhofer AST-1 A 840

(c) by Aerolog Gesellschaft für Informationslogistik, München