3.2 Aircraft Systems and Flight

 Propeller

 The propeller is the component that converts the mechanical energy produced by the engine into thrust, which enables the plane to move forward due to changes in air pressure and speed caused by its aerodynamic profile. It is connected to the crankshaft and is in charge of converting the engine's work into a rotary motion that drives the propeller. The propeller is made up of blades positioned concentrically to an axis, which causes the blades to trace a circular motion when the engine is spinning.

   Each blade is made up of a number of aerodynamic profiles that gradually change their angle of incidence (twist) from the hub to the tip rather than having a single profile (the greater angle at the root, less at the tip). It is important to compensate for this disparity by providing a uniform force since the end of the propeller rotates faster than the part closest to its axis of rotation and covers a greater distance in the same amount of time. The solution entails gradually decreasing the angle of incidence towards the ends so that a higher speed but smaller angle towards the ends adjust the lower speed but greater angle in the propeller shaft. This method lowers internal stresses and vibrations by producing a uniform force throughout the whole propeller.

According to Turner, "A propeller overspeed occurs when engine RPM exceeds redline. This can overstress the propeller blades and hub resulting in failures that can break the propeller apart. In extreme cases, the vibration has ripped engines clean off the airframe, which alters the airplane’s center of gravity to the point the airplane is uncontrollable" (Turner, 2022). Performance of an aircraft is influenced by a wide range of factors in the aircraft, engines, and propellers. The airspeed necessary to maintain level flight may differ from the speed corresponding to the best glide speed in some circumstances of propeller overspeed, as should be noted by pilots of aircraft with variable-pitch propellers. In the event of propeller overspeed, the proper emergency measures must be followed to minimize the emergency situation; however, pilots should be aware that a slight decrease in airspeed may allow them to continue their flight and land safely. When the pilot has enough time to decide on a different course of action than a landing right away, it is only safe to determine an airspeed that is better than the optimum engine glide speed.

References

Turner Tom. (2022, June 13). Propeller Overspeed. PilotWorkshops. https://pilotworkshop.com/tips/propeller-overspeed/