Pushback is the movement of an aircraft from a nose-in parking stand using the power of a specific ground vehicle attached to or supporting the nose landing gear. It is commonly the second part of a ‘Taxi In Push Out’ (TIPO) procedure at airport terminal gates and will be necessary to depart from all except self maneuvering parking stands unless the aircraft type is capable of powerback and local procedures allow this. Occasionally, a pushback may need to be followed by an engines-running pull forward to a position where local procedures allow aircraft to move forward by their own means, but usually, ground vehicle disconnection will occur after the completion of a pushback.
Once the aircraft captain has given the confirmation of ‘brakes released’ to the person in charge of the ground crew who are to carry out the pushback, the ground crew become temporarily responsible for the safe maneuvering of the aircraft in accordance with the standard procedures.
Unless the maneuver is taking place outside the movement area controlled by ATC, an RTF clearance to carry it out will be required. Usually but not always, this will be obtained by the captain. The prescribed RTF phraseology for pushback is contained in ICAO PANS-ATM.
The ‘traditional’ method of allowing the ground vehicle to move an aircraft is to attach it to the aircraft nose landing gear with a towbar. These must be approved for use with a particular aircraft type, clearly marked. The same towbar attachment and ground vehicle may also be used for Aircraft Towing in the forward direction.
An alternative method which is becoming more common for pushback is the use of a specific vehicle called a ‘towbarless tug’. This vehicle positions two low level ‘arms’ either side of the aircraft nose landing gear and these are used to engage with the aircraft gear leg and raise it slightly off the ground.
Both pushback methods are subject to the observance of any aircraft limits for maximum nose landing gear steering angle.
The responsibilities of the ground crew team carrying out a pushback include ensuring that no part of the aircraft structure will impact any fixed object or other aircraft and may include giving clearance to start one or more engines just before, during or immediately after a pushback.
The number of people assigned to a ground crew team for a pushback may vary according to aircraft size, but in most cases will be at least three. One will be driving the pushback vehicle, one will be walking close to one of the aircraft wingtips and looking beyond the aircraft tail and one will be in charge of the maneuver and in communication with the person with aircraft responsibility in the flight deck.
Communication between the ground crew supervisor is usually by means of a plug in to an aircraft ground intercom circuit; if so, this is facilitated by a ground crew microphone which acquires the voice of the user while excluding background noise, which if the aircraft engines are running can be considerable. If only two ground crew are used for pushback of a smaller aircraft then it is important that the procedure takes full account of the roles of each ground crewmember and that the person in charge of ground crew communications on the flight deck is aware of the number of ground crew being used and the physical location of the supervisor.