Full throttle is the maximum possible energy output; it is reached when the throttle plates inside the carburetor or throttle body are wide open, allowing the greatest air-and-fuel intake with the least resistance. In aircraft, this power setting is the primary means of controlling propulsion through the throttle levers, and it can be applied to normally aspirated as well as most turbocharged engines.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is a full throttle aircraft?
A full throttle aircraft refers to wide-open throttle, which is the fully opened state of throttle; this state occurs in an internal combustion engine. Full throttle is the maximum-speed state of running the engine, with normally aspirated (non-turbocharged) engines. It is accomplished through a push-pull device or lever that is pushed forward to increase power, letting the pilot add power by adjusting the amount of fuel-air mixture delivered to the cylinders.
Is full throttle bad for a plane?
No, full throttle is not bad for the plane. Engine wear prevention is the reason for not using full thrust on every departure. Calculations already show the aircraft still meets climb and obstacle-clearance limits with less power, so reduced thrust is the everyday setting. Full thrust exists as a reserve, held for the moment when extra margin is required: windshear, short runway, or an engine failure after liftoff.
Full throttle does not affect safety. Passengers typically experience no more than 1.3 g's (5.74 m/s) of force when the levers go forward; they notice a stronger push back into the seat. When a go-around call for TOGA thrust occurs, the pilot adopts an appropriate climb attitude and airspeed, lets the airplane pitch up, and the cabin senses a momentary 30% increase in perceived weight.
Full throttle may put the mechanism itself at risk. NASA ASRS Database reports a throttle stuck at full power, a snapped cable holding the levers at 2200 RPM, or autothrottle deactivated with thrust levers at idle. When these issues occur, crews re-trim, relax pressure on the yoke if high and slow, and recapture the glide path by adding or retarding power as needed.
Do planes fly at full throttle?
No, planes do not fly at full throttle. Pilots increase throttle to full only for a few minutes during the initial climb; once the aircraft is at a safe altitude the pilot will transition to a more efficient climb profile. At the initial cruise level the auto throttle will set the power required to achieve that speed, and thereafter the pilots set the most efficient climbing, cruising, and descent settings. Jet airliners cruise at constant speed and altitude, so the pilot will set a desired engine power for the given flight that is below the maximum. As the aircraft burns off fuel the required thrust will decrease to keep the same Mach number, showing that cruise flight is performed with a pre-arranged profile, not with continuous full thrust.
Commercial planes never sustain full throttle in level cruise. Full thrust is reserved for take-off, emergency climbs, or when altitude and temperature extremes leave the engines with little surplus margin; even then, aircraft cannot climb even with full thrust at high altitude. Instead, the flight's cruise phase is done using a pre-arranged profile that trades a small surplus of power for the lowest possible fuel flow.
Do planes take off at full throttle?
An airliner will rarely use full throttle at takeoff. The performance is carefully calculated prior to each takeoff, and the proper speeds, power settings and flaps are used for the weight of the takeoff on the runway intended and at the proper temperature.
When pilots move the throttle forward, the engine gradually spools up to the desired speed rather than jumping to maximum power immediately. Pilots often spool engines in stages, especially before takeoff. They first advance the throttles to a moderate power setting and hold briefly, allowing both engines to reach the same rotational speed. Spooling up gives pilots a final opportunity to monitor engine performance before committing to full thrust, yet it is always possible to increase to full power if the situation requires. Larger aircraft like the 747 take more time to spool up because more rotating mass in the engine has to be accelerated.
During the take-off roll the airplane accelerates from zero groundspeed to a predetermined speed at which it can lift itself from the ground, then rotates to a higher angle of attack. The buzzsaw effect is a grinding noise heard on takeoff as the engine spools up to the desired speed, yet lift will not equal weight until the moment of lift-off.
Do aircraft go full throttle during landing?
Aircraft do not go full throttle during landing. In normal operations the throttle is closed immediately after touchdown, and most jets are optimized for acceptable throttle response at approach speeds, so the lever modulates throttle to maintain the proper rate of descent until the runway is assured. Engine power is cut to idle at or below 1000 feet AGL (304.8 meters AGL) per ACS standards, once the airplane has touched down the throttle is pulled to idle after landing assured.
The exception is the short-field technique. Optimum short-field technique requires power to be on until the aircraft is in landing attitude and near the ground; the pilot advances throttle slightly to prevent excessive rate of sink or stall, then smoothly reduces power while raising the nose to landing attitude. Even here, however, power is reduced as the aircraft promptly lands, and the throttle is closed immediately after touchdown. The Fresnel lens optical landing system provides guidance for correctly landing on an aircraft carrier, but 2 seconds means you end in the water when landing on an aircraft carrier, so the pilot never flies approach to touchdown without moving throttles. Instead, advancing throttles keep engines spooled in case the hook misses the wire. If the arresting-gear crew inputs the weight specifications of the incoming jet before the aircraft lands and the gear fails, throttles advanced for three seconds give the energy to go around. Once the aircraft has landed with full flaps and the hook catches, the throttle is closed after the airplane has touched down.
How is full throttle applied?
Full throttle in an aircraft is applied through the thrust levers housed in the throttle quadrant mounted in the center pedestal. When WOT is required the pilot moves the thrust lever through roughly 90 degrees until the lever hits a forward stop. The mechanism set to fully open is unrestricted, so thrust levers must stop within 2% of the commanded position and carry about a quarter inch of spring back to confirm engagement.
Directional control during full throttle is maintained by steering with the rudder pedals while the aircraft is still on the ground. Once the elevator becomes effective the pilot continues to keep the wings level with aileron and the nose on the center-line with rudder, so throttle and flight-control inputs remain separate.
The throttle quadrant contains the TO/GA button: pressing it commands the autothrottle to advance the thrust levers to the full-throttle take-off or go-around position in exactly 7 seconds, after which the lever is held by the same forward stop until the pilot decides to reduce power.
