page_title: Pushback
section_title: Tractors and towbars
hierarchical_section_title: Pushback / Equipment / Tractors and towbars
caption_attribution_description: reg.: D-AIGL
context_page_description: In aviation, pushback is an airport procedure during which an aircraft is pushed backwards away from an airport gate by external power. Pushbacks are carried out by special, low-profile vehicles called pushback tractors or tugs.
  Although many aircraft are capable of moving themselves backwards on the ground using reverse thrust, the resulting jet blast or prop wash might cause damage to the terminal building or equipment. Engines close to the ground may also blow sand and debris forward and then suck them into the engine, causing damage to the engine. A pushback is therefore the preferred method to move the aircraft away from the gate.
context_section_description: Large aircraft cannot be moved by hand and must have a tractor or tug. Pushback tractors use a low profile design to fit under the aircraft nose. For sufficient traction the tractor must be heavy, and most models can have extra ballast added. A typical tractor for large aircraft weighs up to 54 tonnes (119,000 pounds) and has a drawbar pull of 334 kN (75,000 lbf).  Often the driver's cabin can be raised for increased visibility when reversing and lowered to fit under aircraft. There are two types of pushback tractors: conventional and towbarless (TBL).
  Conventional tugs use a tow bar to connect the tug to the nose landing gear of the aircraft.  The tow bar is fixed laterally at the nose landing gear, but may move slightly vertically for height adjustment. At the end that attaches to the tug, the tow bar may pivot freely laterally and vertically. In this manner the tow bar acts as a large lever to rotate the nose landing gear. Each aircraft type has a unique tow fitting so the towbar also acts as an adapter between the standard-sized tow pin on the tug and the type-specific fitting on the aircraft's landing gear.  The tow bar must be long enough to place the tug far away enough to avoid hitting the aircraft and to provide sufficient leverage to facilitate turns.  On heavy tow bars for large aircraft the towbar rides on its own wheels when not connected to an aircraft.  The wheels are attached to a hydraulic jacking mechanism which can lift the towbar to the correct height to mate to both the airplane and the tug, and once this is accomplished the same mechanism is used in reverse to raise the tow bar wheels from the ground during the pushback process.  The tow bar can be connected at the front or the rear of the tractor, depending on whether the aircraft will be pushed or pulled. The towbar has a shear pin which prevents the aircraft from being mishandled by the tug; when overstressed the shear pin will snap, disconnecting the bar from the nose gear to prevent damage to the aircraft and tug.
  Towbarless (TBL) tractors do not use a towbar; they scoop up the nose landing gear and lift it off the ground.  This avoids the time penalty of connecting/disconnecting a towbar, and entirely removes the cost/complexity of maintaining towbars on the ramp.  The tug itself does not need to be particularly massive - the aircraft's nosewheel weight provides the necessary downward force.  Lastly, a TBL tug is much shorter (compared to a tug+towbar system) and has one only a single pivot point instead of one at either end of the towbar, so it has much simpler and precise control of the aircraft.  This is very useful in general aviation settings with a wider variety of aircraft in more confined spaces than their airline counterparts.
  Manufacturers of electric TBL tugs offer models capable of moving any aircraft from the smallest single-engine type to narrow-body airliners, military cargo and airline-sized business jets.  Just as specialized towbars are required for a wide range of aircraft, many TBL tugs use adapters which enable the movement of many unique aircraft.  The majority of aircraft do not require adapters and can be moved without any special adjustments to the tug.  This is in contrast to conventional tugs which often use so-called "universal" towbars which must be adjustable to suit many aircraft types.  Electric TBL tugs are gaining popularity among general aviation operators and FBOs as an alternative to gas or diesel-powered conventional tugs. Being electric rather than internal combustion-powered, electric tugs are low-emission which is a major advantage for environmentally-conscious operators; this also enables the tug to be safely operated inside a closed hangar.
caption: A towbarless tug at Frankfurt Airport transporting a Lufthansa Airbus A340-300
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