Taxiing (rarely spelled taxying) is the movement of an
aircraft
An aircraft is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or by using the Lift (force), dynamic lift of an airfoil, or in ...
on the ground, under its own power, in contrast to
towing or
pushback
In aviation, pushback is an airport procedure during which an aircraft is pushed backwards away from its parking position, usually at an airport gate by external power. Pushbacks are carried out by special, low-profile vehicles called ''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
An airport is an aerodrome with extended facilities, mostly for commercial air transport. Airports usually consists of a landing area, which comprises an aerially accessible open space including at least one operationally active surfa ...
to another; for example, when moving from a
hangar
A hangar is a building or structure designed to hold aircraft or spacecraft. Hangars are built of metal, wood, or concrete. The word ''hangar'' comes from Middle French ''hanghart'' ("enclosure near a house"), of Germanic origin, from Frankish ...
to the
runway
According to the International Civil Aviation Organization (ICAO), a runway is a "defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft". Runways may be a man-made surface (often asphalt, concrete ...
. 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.
Etymology
As early as 1909 aviation journalists envisioned aeroplanes to replace the
taxicab
A taxi, also known as a taxicab or simply a cab, is a type of vehicle for hire with a driver, used by a single passenger or small group of passengers, often for a non-shared ride. A taxicab conveys passengers between locations of their choi ...
in traffic-congested cities.
Some aviators and some linguists report that around the year 1911 the
slang
Slang is vocabulary (words, phrases, and linguistic usages) of an informal register, common in spoken conversation but avoided in formal writing. It also sometimes refers to the language generally exclusive to the members of particular in-gr ...
word "taxi" was in use for an "airplane". They suggest that the way aircraft move under power before they take off or after they land reminded someone of the way
taxicab
A taxi, also known as a taxicab or simply a cab, is a type of vehicle for hire with a driver, used by a single passenger or small group of passengers, often for a non-shared ride. A taxicab conveys passengers between locations of their choi ...
s slowly drove around the block when looking for passengers.
Also by 1909, French aviation pioneers like
Blériot,
Farman and
Voisin used the term "taxi" for a
trainer aircraft, that was so constructed that a pupil would not accidentally get airborne.
Usage of the word for an airplane quickly disappeared again, but the verb "to taxi" stuck, and words like the "
taxiway" were derived from it.
Propulsion
The thrust to propel the aircraft forward comes from its
propellers or
jet engine
A jet engine is a type of reaction engine discharging a fast-moving jet (fluid), jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include Rocket engine, rocket, Pump-jet, water jet, and ...
s. Reverse thrust for backing up can be generated by
thrust reversers
Thrust reversal, also called reverse thrust, is the temporary diversion of an aircraft engine's thrust for it to act against the forward travel of the aircraft, providing deceleration. Thrust reverser systems are featured on many jet aircraft to ...
such as on the
Boeing C-17 Globemaster III, or reversible pitch propellers such as on the
Lockheed C-130 Hercules, a procedure known as
powerback. Most aircraft, however, are not designed to back up on their own and must be pushed back either by hand or by using an
aircraft tug.
At low power settings, combustion aircraft engines operate at lower efficiency than at cruise power settings. A typical
A320
The Airbus A320 family is a series of narrow-body airliners developed and produced by Airbus.
The A320 was launched in March 1984, first flew on 22 February 1987, and was introduced in April 1988 by Air France.
The first member of the fami ...
spends an average of 3.5 hours a day taxiing, using of fuel. Hybrid electrically driven nose gear are under development to allow high use aircraft to shut down the engines during taxi operations.
Control
Steering is achieved by turning a
nose wheel or tail wheel/
rudder
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally air or water). On an aircraft the rudder is used primarily to counter adve ...
; the
pilot controls the direction travelled with their feet. Larger jet aircraft have a tiller wheel on the left side of the cockpit that acts as a steering wheel allowing the nosewheel to be turned hydraulically. Braking is controlled by differential toe or heel brakes. Not all aircraft have steerable wheels, and in some cases steering is solely by means of differential braking (all
Van's aircraft for instance) or solely by means of the rudder (including all
floatplanes).
Hover taxi
Skid-equipped
helicopters
A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attribu ...
and other
VTOL (Vertical Take-Off and Landing) aircraft conduct hover taxiing to move in
ground effect in the same manner that wheel-equipped aircraft ground taxi. In general hover taxis are conducted at speeds up to , or below
translational lift Translational lift is improved rotor efficiency resulting from directional flight in a helicopter. Translation is the conversion from the hover to forward flight. As undisturbed air enters the rotor system horizontally, turbulence and vortices creat ...
.
[Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 263. Aviation Supplies & Academics, 1997. ]
The
Bell CH-135 Twin Huey is hover taxied in a manner typical for skid-equipped aircraft of that size:
Safety
When taxiing, aircraft travel slowly. This ensures that they can be stopped quickly and do not risk wheel damage on larger aircraft if they accidentally turn off the paved surface. Taxi speeds are typically .
Rotor downwash limits helicopter hover-taxiing near parked light aircraft. The use of engine thrust near terminals is restricted due to the possibility of structural damage or injury to personnel caused by
jet blast.
References
External links
* aircraft
*
{{Flight phases
Aircraft operations
Flight phases