Aeroplane Propellers and what’s required to drive them

Aeroplane Propellers can be made from wood, metal or composite materials. The power required to drive an airplane propeller depends on several factors, including the size and design of the propeller, the speed at which it is driven, and the type of aircraft it is installed on.

It’s not impossible to achieve flight with a small engine. The Wright brothers’ first flight was powered by a 12hp engine. But, the key question is whether a 7.5hp engine can provide a meaningful flight envelope while carrying a realistic useful load over a wide range of atmospheric conditions?

Turboprop engines are typically much more powerful. For example, Pratt & Whitney Canada PT6A-60A turboprop engine, used in some aircraft, is a very powerful engine. The PT6B/C are turboshaft variants are for helicopters. The PT6A turboprop engine covers the power range between 580 and 1,940 shp (430 and 1,450 kW). So, if you pick a 7.5hp motor cycle gasoline engine with reduction gears to fly a turbo-prop, you are probably short of a few hundred horse powers.

In general, most car/motorcycle engines rev too high to be used in an aircraft, you actually want to lower the RPM, not raise it. You can pull it off with a stepper gear box (like a turbo prop uses) and it was even done on a piston plane back in the 80’s by Mooney.

Again, these are my general understandings – Aircraft engines have to ensure safety and performance and I am no flight expert. I have just shared some observation.

The actual power required for steady level flight takes the form of a curve, with the velocity for minimum power obtained by taking the derivative of the equation for power with respect to velocity and setting it equal to zero.

Now, back to propellors. Let’s see how each one weighs.

Wooden Propellers: A typical 74-inch wooden propeller for a four-cylinder Lycoming engine weighs approximately 10-12 pounds.

The weight of a two-blade wooden propeller varies between 10 and 14 pounds, and a three-blade propeller weighs between 11 and 15 pounds.

Metal Propellers: A typical 74-inch metal propeller for a four-cylinder Lycoming engine weighs approximately 30 pounds.

The weight of a metal three-blade propeller/spinner on a Cirrus SR20 is 80.7 pounds.

The weight of a two-blade metal propeller varies between 10 and 14 pounds, and a three-blade propeller weighs between 11 and 15 pounds.

Composite Propellers: The weight of a Hartzell three-blade Raptor composite prop on a Cirrus SR20 is 51.2 pounds.

A 76-inch composite-blade propeller weighs only 46.8 pounds, despite its slightly larger diameter, compared to the aluminum-blade version.

The weight of a two-blade composite propeller varies between 10 and 14 pounds, and a three-blade propeller weighs between 11 and 15 pounds.