A takeoff/go-around switch (TO/GA; ) is a switch on the

autothrottle An autothrottle (automatic throttle, also known as autothrust, A/T) is a system that allows a pilot to control the power setting of an aircraft's engines by specifying a desired flight characteristic, rather than manually controlling the fuel flo ...

of modern large

aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...

, with two modes:

takeoff Takeoff is the phase of flight in which an aerospace vehicle leaves the ground and becomes airborne. For aircraft traveling vertically, this is known as liftoff. For aircraft that take off horizontally, this usually involves starting with a t ...

(TO) and

go-around In aviation, a go-around is an aborted landing of an aircraft that is on final approach or has already touched down. A go-around can either be initiated by the pilot flying or requested by air traffic control for various reasons, such as an unstab ...

(GA). The mode is dependent on the phase of flight; usually, on approach to land, the

autopilot An autopilot is a system used to control the path of an aircraft, marine craft or spacecraft without requiring constant manual control by a human operator. Autopilots do not replace human operators. Instead, the autopilot assists the operator' ...

will be set to approach mode, therefore if the TO/GA switch is pressed it will activate the go-around mode of the autothrottle; conversely, when takeoff is set on the autopilot, the switch activates takeoff mode of the autothrottle. On

Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and product ...

aircraft TO/GA modes are selected by a separate switch near the throttle levers, but on

Airbus Airbus SE (; ; ; ) is a European Multinational corporation, multinational aerospace corporation. Airbus designs, manufactures and sells civil and military aerospace manufacturer, aerospace products worldwide and manufactures aircraft througho ...

aircraft it is activated by pushing the thrust levers fully forward to the TO/GA

detent A detent is a mechanical or magnetic means to resist or arrest the movement of a mechanical device. Such a device can be anything ranging from a simple metal pin to a machine. The term is also used for the method involved. Magnetic detents are ...

Takeoff

Once an aircraft has lined up, the pilots first increase the engine power to 40–60% N₁ (low-pressure compressor RPM) on

aircraft, and 50% N₁ on

aircraft. Large jet engines accelerate slowly from idle to approximately 40%, and stabilising the engines prior to applying full power prevents a large thrust asymmetry from causing directional problems if one engine accelerates more quickly. This can also reduce the risk of a

compressor stall A compressor stall is a local disruption of the airflow in the compressor of a gas turbine or turbocharger. A stall that results in the complete disruption of the airflow through the compressor is referred to as a compressor surge. The severity of t ...

. Once the engines are confirmed to be stable, the pilots then either press the TO/GA switch, causing the thrust levers to automatically advance themselves to the appropriate power setting (on Boeings), or manually advance the thrust levers to the TO/GA detent (on Airbuses). (In Airbus aircraft, if de-rated takeoff power is desired, the thrust levers are instead advanced to the FLX/MCT detent.) In all cases, the engine speeds then increase to provide the computed takeoff power. Flight management computers on modern aircraft determine the amount of power needed by the engines in order to reach takeoff speed; a number of factors have to be taken into account, including

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, as ...

length, wind speed, temperature, and most importantly the weight of the aircraft. In older aircraft these calculations were performed by the pilots before takeoff. The advantage of having such a system is the ability to reduce wear and tear on the engines by using only as much power as is actually required to ensure the aircraft reaches a safe takeoff speed.

Go-around

The go-around setting is used during the approach. If a pilot finds that they are unable to land safely, or deems it necessary to go-around for any reason, activating this switch (usually positioned on the back of the throttle levers) will increase the power to go-around thrust. Importantly, the TO/GA switch modifies the autopilot mode, so it does not continue to follow the Instrument Landing System (ILS)

glide slope Instrument landing system glide path, commonly referred to as a glide path (G/P) or glide slope (G/S), is "a system of vertical guidance embodied in the instrument landing system which indicates the vertical deviation of the aircraft from its o ...

and it overrides any auto-throttle mode which would keep the aircraft in landing configuration. On Airbus aircraft, it does not disengage the autopilot but causes it to stop following the ILS and to perform the go-around maneuver automatically. In an emergency situation, using a TO/GA switch is often the quickest way of increasing thrust to abort a landing. On some aircraft, the TO/GA switch commands the autopilot to fly a

missed approach Missed approach is a procedure followed by a pilot when an instrument approach cannot be completed to a full-stop landing. The instructions for the missed approach may be assigned by air traffic control (ATC) prior to the clearance for the approac ...

pattern, if the autopilot is programmed to do so.

References

Controlling Pilot Error: Automation By Vladimir Risukhin
2001, , p43-45
Better Takeoffs & Landings By Michael C. Love
1995, , page 192 * {{DEFAULTSORT:Takeoff Go-around switch Aircraft controls

Takeoff

Go-around

See also

References