Aircraft Taxiing (rarely spelled taxying) is the movement of an aircraft on the ground, under its own power, in contrast to towing or pushback where the aircraft is moved by a tug. The aircraft usually moves on wheels, but the term also includes aircraft with skis or floats (for water-based travel).
An airplane uses taxiways to taxi from one place on an airport to another; for example, when moving from a hangar to the runway. The term “taxiing” is not used for the accelerating run along a runway prior to takeoff, or the decelerating run immediately after landing, which are called the takeoff roll and landing rollout, respectively.
Taxiing is an important process for nearly all airplanes. From small and medium-sized airliners to large wide-body airliners, most airplanes require taxiing while on the runway. Before taking off and after landing, for example, airplanes must taxi.
Overview of Airplane Taxiing
Taxiing refers to the movement of an airplane while on the runway. At any given moment, there are 5,000 to 10,000 commercial airplanes in the skies over the United States.
As these airplanes transport passengers to their intended destination, they must land at an airport. Airports only have a limited amount of runway space. Therefore, airplanes must be taxied off the runway after landing so that they won’t block or otherwise prevent other airplanes from using the same airport.
Taxiing is simply the process of moving an airplane while it’s on the runway. It occurs after an airplane has landed, and it occurs before an airplane takes off. Airplanes don’t actually fly while on the ground. As a result, the process by which they move on the runway isn’t known as flying; it’s known as taxiing.
How Taxiing Works
There are different ways that airplanes can be taxied. Taxiing is most commonly performed using an airplane’s own propulsion system. For propulsion, most airplanes have either jet engines or propellers. Engaging the propulsion system allows airplanes to move while on the runway.
Some airplanes also have thrust reversers. Thrust reversers live up to their namesake by changing the direction of an airplane’s thrust. In jet-engine airplanes, thrust reversers can assist with taxiing. It essentially allows airplanes to back up while on the runway.
Pilots must still steer airplanes when taxiing them on. Steering is performed using the same control systems as flying an airplane. Pilots can turn the nose wheel or rudder to change the direction in which their airplanes travel while on the runway.
Taxiing vs Towing
It’s important to note that taxiing isn’t the same as towing. When many people hear the word “taxiing,” they envision a ground vehicle physically moving an airplane on the runway.
Taxiing, though, specifically involves the use of an airplane’s own propulsion system to move while on the runway. Towing, on the other hand, refers to the use of a ground vehicle. Known as a tug, these ground vehicles connect to airplanes so that they can move and turn airplanes.
Aircraft Taxiing phase
Taxiing refers to the movement of an aircraft on the ground, under its own power. The aircraft moves on wheels. An airplane uses taxiways to taxi from one place on an airport to another; for example, when moving from a terminal to the runway.
The aircraft always move on the ground following the yellow lines, to avoid any collision with the surrounding buildings, vehicles or other aircraft. The taxiing motion has a speed limit.
Before making a turn, the pilot reduces the speed further to prevent tire skids. Just like cars, there is a certain list of priorities during taxiing. The aircraft that are landing or taking off have higher priority. The other aircraft have to wait for these aircraft before they start or continue taxiing.
The thrust to propel the aircraft forward comes from its propellers or jet engines. Steering is achieved by turning a nose wheel or tail wheel/rudder; the pilot controlling the direction travelled with their feet.
The use of engine thrust near terminals is restricted due to the possibility of jet blast damage. This is why the aircraft are pushed back from the buildings by a vehicle before they can start their own engines for taxiing.
AIRCRAFT TAXI-OUT PROCEDURES
The aircraft taxi-out movement starts when the aircraft disconnects the terminal ground equipment. Then, a towing tug leads the aircraft from the apron gate to the assigned taxiway.
The aircraft main engines are turned on only when a safe distance from the gate areas is reached. At the end of the pushback, the towing tug disconnects (detachment point) and the aircraft moves towards the runway head.
During this step, the main engines operate at low speeds with a 7% thrust, which provides a minimum of 30 knots speed. The required taxi-out time depends on the distance between the standpoint in the apron area and the runway head, therefore on the airport configuration.
Due to security reasons, pilots directly control direction and speed of the aircraft while the airport Ground Movement Control System coordinates aircraft on the airport movement areas to ensure efficient and safe ground movements, including taxiing operations.
The TaxiBot technology allows a direct pilot control during taxi-out, by using the installed cockpit command interface. The tractor is equipped with a special system specifically designed to attach the nose gear tire of the aircraft and lock it up in position.