Jet engines may dominate the commercial aviation industry, but many airplanes still use propeller engines for propulsion. Propeller engines are commonly found on light aircraft, cargo airplanes and various military airplanes. They are typically more fuel-efficient for short-haul flights than jet engines. Propeller engines also require less maintenance.
Not all propeller engines have the same number of blades, however. Some of them have two blades, whereas others have three or even four blades.
What Are Propeller Blades
Propeller blades are airfoil extensions that rotate when the engine is running. They are designed to convert engine power into thrust.
Propeller engines include turboprops and piston engines, both of which have blades. Turboprops work by spinning a shaft, which turns the attached blades. Piston engines, on the other hand, work by pushing pistons, which turns a crankshaft to which the blades are attached. Regardless, the turning blades will slice through the air at a specific angle — the Angle of Attack (AOA) — to propel the airplane forward.
2-Blade Propellers
You’ll often see 2-blade propellers on smaller airplanes. They are characterized by two separate blades on opposite ends.
With only two blades, these propellers are very efficient. They produce less drag than their 3-blade and 4-blade counterparts. For smaller airplanes, this translates into better fuel efficiency.
Another advantage of 2-blade propellers is their weight. Each blade increases the total weight of a given propeller. As a result, 2-blade propellers weigh less than 3-blade and 4-blade propellers.
3-Blade Propellers
Some airplanes have 3-blade propellers. They feature three equally spaced blades.
3-blade propellers fall somewhere in the middle in terms of efficiency. They are more efficient than 4-blade propellers but less efficient than 2-blade propellers.
Many pilots notice reduced vibration with 3-blade propellers compared to 2-blade propellers. This is because 3-blade propeller engines distribute power more evenly with each rotation. In addition to a smoother flight, this helps to protect engine components like mounts from unnecessary wear and tear.
4-Blade Propellers
There are also airplanes with 4-blade propellers. They feature four equally spaced blades. Most turboprops use four individual blades such as this.
With four blades, these propellers allow for the lowest angle of attack. Why does this matter? With a low angle of attack, they offer superior acceleration and climb speed. Airplanes with 4-blade propellers can take off from shorter runways than those with 3-blade and 2-blade propellers.
They may not be as efficient as 3-blade and 2-blade propellers, but 4-blade propellers are very quiet. They produce the least amount of noise and vibrations. The downside to 4-blade propellers is the cost. They typically cost more than 3-blade and 2-blade propellers, and they require more work to maintain.
