How Aircraft Engines Work

Aircraft engines and car engines seem like they would be rather similar. After all, they are both machinery that power massive vehicles used to transport people and goods. But, the truth is, aircraft engines are rather different. Aircraft utilize RPMs, not multi-gear transmissions.

RPMs are like gears in a car, in the sense that propeller driven aircraft depend on specific RPM, or revolutions per minute, settings to achieve different stages of flight. So, the RPMs are at maximum setting during take-offs and landing, and they are reduced to a slower and more efficient setting during flight. During flight, the aircraft engine’s RPM doesn’t change, but the engine power, which translates to speed, can.

Aircraft engines have three major controls: the throttle, the propeller knob and the mixture knob. While the throttle is like the gas pedal of a car in terms of increasing and decreasing power, it’s different in that the aircraft engine still runs at the same speed even as the throttle changes the power output. That’s because the propeller knob changes the RPMs. When the aircraft takes-off, the propeller knob and the throttle are set to full forward for maximum power. But at cruising altitude, the throttle is set to reduce the power output and the propeller RPMs accordingly. The mixture knob is then used to lean the fuel-air ratio to the proper stoichiometric ratio for that particular altitude so that the aircraft flies smoothly.

Notice, to reach cruising speeds, only the throttle and the mixture knobs need to be changed. But the aircraft can still speed up or slow down. The propeller knob doesn’t have to move, and the RPMs don’t have to change. That’s because speed is based on the power output by the throttle, and how propeller blades automatically change pitch, or the distance it would move forward if it were cutting through a solid, accordingly.

Clearly, aircraft engines and car engines are not that similar or comparable. You don’t have to deal with altitudes, stoichiometry of fuel-air ratios, or pitch when you drive a car. But, like a car, you do have to maintain your engine and repair and replace parts when need-be. At times like that, you have ASAP Purchasing, owned and operated by ASAP Semiconductor, one of the premier suppliers of aviation parts and components ranging from massive engines to tiny bearings.