Why do aircraft engines use ridiculously small propellers?

0:00 The engineering reasons why light aircraft propellers are designed with specific sizes and configurations. 0:13 Cessna 172 1:30 helicopter 1:48 Wright brothers' first airplane 5:32 landing gear 9:23 Republic XF-84H 11:32 Rotax 912 14:19 Airbus A400M Why do light aircraft use propellers that look ridiculously small? I break down the real engineering behind their size, using physics, performance, and practical design limits. I explain why helicopters and the Wright brothers’ airplane used much larger propellers, while modern light aircraft prioritize cruise efficiency. I also examine takeoff performance, landing gear clearance, tip speed, the speed of sound, and propeller noise. I compare direct-drive engines with reduction gearboxes, including the Rotax 912, and show how weight, torque, gyroscopic effects, blade count, and maintenance shape propeller design. I also look at the Republic XF-84H, the Airbus A400M, composite propellers, and electric propulsion.