The throttle lever or throttle is an aircraft control mechanism that controls the power output of an airplane's engines, making it one of the most important control mechanisms in flight. The throttle adjusts the thrust produced by controlling the fuel flow to the combustion chamber. In single-engine airplanes it consists of one lever, whereas multi-engine throttle quadrants present separate levers for each engine, enabling the pilot, copilot, flight engineer, or autopilot to control the thrust output with accuracy.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is a throttle on an airplane?
The throttle is the main control mechanism for engine power output, and the throttle lever controls the power output of an airplane's engines. Single-engine throttle consists of a single lever while a four-engine airplane has four throttle levers. Throttle levers allow for precise adjustments to the engine's power setting.
In the cockpit the throttle is a lever that is connected to a throttleable valve that precisely meters the fuel or the fuel-air mixture that enters the engine. Because a single lever controls the power output of the aircraft's engine, pilots can increase thrust by pushing the lever forward. Precise adjustments directly influence the aircraft's speed and overall performance during flight.
The area of many flight decks that contains these thrust levers is called the thrust-lever quadrant, a name derived from the circular-arc panel on which the levers are mounted. Each lever is usually colored black, and the quadrant also houses the propeller control (typically blue) and the mixture control (typically red). In modern aircraft the throttle no longer moves cables; instead it sends signals to a computer that regulates fuel flow based on various parameters and thereby adjusts thrust, handles thrust reversers and afterburners, and shows pilots which settings the autopilot system is selecting when the motor-driven levers move automatically while in auto-throttle mode.
What does the throttle control in an airplane?
The throttle in an airplane controls the power or thrust output of the engine by regulating the amount of fuel or fuel-air mixture entering the engine. Throttle control is the main lever of engine power, normally a black lever at the bottom-centre of the instrument panel. In carburetted engines the lever sets the mass-flow rate of the air-fuel mixture whereas in fuel-injection engines the same lever is called a power or thrust lever and controls the amount of fuel injected into the cylinders. If the lever is pushed forward, the power, manifold pressure, torque, and propeller RPM rise whereas if the lever is pulled aft, the mixture, pressure, and power are reduced.
Precise adjustments to the throttle power setting directly influence airspeed, climb rate and descent profile, so pilots anticipate changes by adding power before climbs and reducing it before descents. Aircraft equipped with constant-speed propellers add a blue propeller control beside the black throttle and this control adjusts blade pitch while a governor keeps propeller speed constant. A red mixture control sits next to the propeller lever so the pilot can fine-tune the fuel-air mixture as altitude changes.
How does a plane throttle work?
A throttle works by controlling the amount of fuel and/or air entering the engine. The cockpit control is directly linked with the throttle valve. Modern jet aircraft are equipped with thrust levers which are connected to a Fuel Control Unit (FCU) and, in the most advanced installations, to a digital electronic computer called a Fully Authority Digital Engine Controller (FADEC). Thrust levers are used by the pilot, copilot, flight engineer, or autopilot to control the thrust output of the aircraft's engines; they adjust the fuel flow to the engines, and that fuel flow adjustment directly affects thrust output. In practice, pushing the levers forward automatically operates the switches to open the fuel cocks, which then remain open during the normal operating range of the levers. The throttleable valve precisely meters fuel into the combustion chambers, allowing pilots to increase an engine's power by pushing the throttle. Precise adjustments directly influence the aircraft's speed.
Microswitches are located in the throttle box so that throttle levers actuate the switches to shut the valves when the levers are at their aft end of travel; pulling the throttle lever to the aft position operates a mechanical latch that allows the lever to travel further and shut off the fuel valve. After the take-off climb is established the pilot reduces the power output of the engine to climb power by first decreasing the manifold pressure and then increasing the blade angle to lower rpm, a sequence that keeps thrust at maximum while decreasing engine rpm and reducing engine wear. Autothrottle systems have an ‘arm’ switch that powers the autothrottle system; when employed, the autothrottles will power the engines up to the maximum limit for the phase of flight. Boeing aircraft autothrottles physically move via a small motor system, whereas on Airbus aircraft the thrust levers do not physically move as engine power changes. The computer, whether mechanical or digital, handles the additional components of the engines like the thrust reversers and afterburners, assuring that every commanded change in lever position translates into the correct fuel flow and, ultimately, the correct thrust.
What are the throttle positions on an aircraft?
Throttle positions are set through the thrust or throttle levers found in the cockpit of aircraft. Typically there is one lever for each engine, and in two-pilot flight decks each pilot station is equipped with its own set.
Maximum take-off power is obtained by moving the levers fully forward, while the CLIMB detent or CLIMB position keeps the levers in place from the thrust-reduction altitude all the way to just before landing in normal operations. In Airbus airliners, placing the lever at this setting permits the autopilot to set N1 automatically to reach cruise speed, an action described by ‘stating’. The autopilot uses the CLIMB setting to set N1 automatically. The precise N1 window for the A320, taken from the A320 throttle quadrant operating in standard ISA conditions, runs from 80.4% to 86.5% depending on weight and altitude.
The levers travel forward for higher power and aft to the idle stop or aft end of travel when power is to be reduced or the engines shut down. Pilots intentionally pull the lever back further to its aft end of travel and overcome a mechanical latch, closing the fuel cut-off position. Forward motion is arrested at hard detents - CLIMB or TO/GA - rather than at an intermediate ‘backwards’ location, so movement towards the pilot is always IDLE or STOP rather than being a reverse thrust position. Reverse thrust is instead controlled by a separate device; the control for each thrust reverser is usually found adjacent to the corresponding engine lever, providing a distinct, independent actuation path. Throughout the flight the autopilot can continue to command lever position, using either the TO/GA setting for go-around or the stable CLIMB setting during cruise, in which case N1 will evolve automatically as weight decays to maintain Mach number.
What happens to the plane when the pilot closes the throttle?
When a pilot closes the throttle (reduces power to idle), the airplane's engine produces less thrust, leading to a loss of lift and a reduction in airspeed. In a stable, trimmed flight, this causes the nose to drop slightly, and the aircraft begins to descend.
What are the types of throttle on an airplane?
The types of throttle on an airplane are listed below.
- Single-Engine Throttle
- Multi-Engine Throttle Quadrant
- Jet Engine Thrust Levers
- Autothrottle/Autothrust (A/T or A/THR)
What is the best throttle for an airplane?
The best throttle for an airplane varies. For most desktop pilots, the Honeycomb Bravo Throttle Quadrant is the best overall choice because it offers exceptional versatility and quality at a reasonable price point. Detachable levers let the unit serve both single- and multi-engine layouts, while built-in switches handle flaps, speed-brake and other functions in one compact panel, making it equally useful to the GA flyer and the future airline captain. Seekers of maximum authenticity on a Boeing flight-deck gravitate to the Thrustmaster TCA Quadrant Boeing Edition, whose handles, detents and 15 analog axes directly mirror the 737, whereas Airbus enthusiasts reach for the parallel Airbus Edition for the A320 feel. Turboprop specialists choose the Virtual Fly TQ neo, the first high-end throttle designed specifically for turboprop simulation while still able to manage piston aircraft, whereas the more advanced Virtual Fly TQ3+ and V3RNIO+ represent the current pinnacle of high-end hardware.
Budget builders are well served by the Logitech G Flight/Pro Flight Throttle Quadrant, the best affordable throttle and a simple three-lever module that can be daisy-chained for multi-engine use. Those on an Xbox or PC hybrid set-up find the Turtle Beach VelocityOne Universal Control System best xbox-compatible throttle, with its integrated throttle controls built right into the yoke base, while a TWCS Throttle remains the best value HOTAS option for space or fast-jet cockpits. Expert sim centers rely on the Thrustmaster Warthog, Winwing Orion, Virpil VPC MongoosT-50CM3 and the forthcoming VKB TECS, whose heritage shows in their durability and ability to withstand intensive training environments.
