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Aircraft engine starting
Many variations of aircraft engine starting have been used since the Wright brothers made their first powered flight in 1903. The methods used have been designed for weight saving, simplicity of operation and reliability. Early piston engines were started by hand. Geared hand starting, electrical and cartridge-operated systems for larger engines were developed between the First and Second World Wars.
Gas turbine aircraft engines such as turbojets, turboshafts and turbofans often use air/pneumatic starting, with the use of bleed air from built-in auxiliary power units (APUs) or external air compressors now seen as a common starting method. Often only one engine needs be started using the APU (or remote compressor). After the first engine is started using APU bleed air, cross-bleed air from the running engine can be used to start the remaining engine(s).
Hand starting of aircraft piston engines by swinging the propeller is the oldest and simplest method, the absence of any onboard starting system giving an appreciable weight saving. Positioning of the propeller relative to the crankshaft is arranged such that the engine pistons pass through top dead centre during the swinging stroke.
As the ignition system is normally arranged to produce sparks before top dead centre there is a risk of the engine kicking back during hand starting. To avoid this problem one of the two magnetos used in a typical aero engine ignition system is fitted with an 'impulse coupling', a spring-loaded device which delays the spark until top dead centre and which also increases the rotational speed of the magneto to produce a stronger spark. When the engine fires, the impulse coupling no longer operates and the second magneto is switched on. As aero engines grew bigger in capacity (during the interwar period), single-person propeller swinging became physically difficult—ground crew personnel would either join hands and pull together as a team, or else a canvas sock would be fitted over one propeller blade, the sock having a length of rope attached to the propeller tip end. Note that this is different from the manual "turning over" of a radial piston engine, which is done to release oil that has become trapped in the lower cylinders prior to starting to avoid engine damage. The two appear similar, but while hand starting involves a sharp, strong "yank" on the prop to start the engine, turning over is simply done by turning the prop through a certain set amount.
Accidents have occurred during lone pilot hand starting, whether due to high throttle settings, brakes not having been applied, or wheel chocks not being used, all resulting in the aircraft moving off without the pilot at the controls. "Turning the engine" with the ignition and switches accidentally being left "on" can also cause injury if the engine starts unexpectedly when a spark plug fires—if the switch is not in the "start" position, the spark will occur before the piston hits top dead center, which can force the propeller to violently kick back.
The Hucks starter (invented by Bentfield Hucks during WWI) is a mechanical replacement for the ground crew. Based on a vehicle chassis the device uses a clutch driven shaft to turn the propeller, disengaging as the engine starts. A Hucks starter is used regularly at the Shuttleworth Collection for starting period aircraft.
Self-sustaining motor gliders (often known as 'turbos') are fitted with small two-stroke engines with no starting system, for ground testing a cord is wrapped around the propeller boss and pulled rapidly in conjunction with operating decompressor valves. These engines are started in flight by operating the decompressor and increasing airspeed to windmill the propeller. Early variants of the Slingsby Falke motor glider use a cockpit mounted pull start system.
Aircraft began to be equipped with electrical systems around 1930, powered by a battery and small wind-driven generator. The systems were initially not powerful enough to drive starter motors. Introduction of engine-driven generators solved the problem.
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Aircraft engine starting AI simulator
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Aircraft engine starting
Many variations of aircraft engine starting have been used since the Wright brothers made their first powered flight in 1903. The methods used have been designed for weight saving, simplicity of operation and reliability. Early piston engines were started by hand. Geared hand starting, electrical and cartridge-operated systems for larger engines were developed between the First and Second World Wars.
Gas turbine aircraft engines such as turbojets, turboshafts and turbofans often use air/pneumatic starting, with the use of bleed air from built-in auxiliary power units (APUs) or external air compressors now seen as a common starting method. Often only one engine needs be started using the APU (or remote compressor). After the first engine is started using APU bleed air, cross-bleed air from the running engine can be used to start the remaining engine(s).
Hand starting of aircraft piston engines by swinging the propeller is the oldest and simplest method, the absence of any onboard starting system giving an appreciable weight saving. Positioning of the propeller relative to the crankshaft is arranged such that the engine pistons pass through top dead centre during the swinging stroke.
As the ignition system is normally arranged to produce sparks before top dead centre there is a risk of the engine kicking back during hand starting. To avoid this problem one of the two magnetos used in a typical aero engine ignition system is fitted with an 'impulse coupling', a spring-loaded device which delays the spark until top dead centre and which also increases the rotational speed of the magneto to produce a stronger spark. When the engine fires, the impulse coupling no longer operates and the second magneto is switched on. As aero engines grew bigger in capacity (during the interwar period), single-person propeller swinging became physically difficult—ground crew personnel would either join hands and pull together as a team, or else a canvas sock would be fitted over one propeller blade, the sock having a length of rope attached to the propeller tip end. Note that this is different from the manual "turning over" of a radial piston engine, which is done to release oil that has become trapped in the lower cylinders prior to starting to avoid engine damage. The two appear similar, but while hand starting involves a sharp, strong "yank" on the prop to start the engine, turning over is simply done by turning the prop through a certain set amount.
Accidents have occurred during lone pilot hand starting, whether due to high throttle settings, brakes not having been applied, or wheel chocks not being used, all resulting in the aircraft moving off without the pilot at the controls. "Turning the engine" with the ignition and switches accidentally being left "on" can also cause injury if the engine starts unexpectedly when a spark plug fires—if the switch is not in the "start" position, the spark will occur before the piston hits top dead center, which can force the propeller to violently kick back.
The Hucks starter (invented by Bentfield Hucks during WWI) is a mechanical replacement for the ground crew. Based on a vehicle chassis the device uses a clutch driven shaft to turn the propeller, disengaging as the engine starts. A Hucks starter is used regularly at the Shuttleworth Collection for starting period aircraft.
Self-sustaining motor gliders (often known as 'turbos') are fitted with small two-stroke engines with no starting system, for ground testing a cord is wrapped around the propeller boss and pulled rapidly in conjunction with operating decompressor valves. These engines are started in flight by operating the decompressor and increasing airspeed to windmill the propeller. Early variants of the Slingsby Falke motor glider use a cockpit mounted pull start system.
Aircraft began to be equipped with electrical systems around 1930, powered by a battery and small wind-driven generator. The systems were initially not powerful enough to drive starter motors. Introduction of engine-driven generators solved the problem.