In our last blog post, we discussed Constant-Speed, Controllable-Pitch, and Feathering Propellers for aircraft. In this blog post, we want to finish covering some other types of aircraft propellers. Namely, we’re going to look at fixed-pitch, ground-adjustable, reverse-pitch, and test club propellers.
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Now, let’s look at some additional types of propellers – and their differences.
A fixed-pitch propeller has the angle, or pitch, built into the propeller, as the name implies. The pitch cannot be changed once the propeller is completed.
A fixed-pitch propeller is just one piece. Only one pitch setting is possible, and the whole configuration is usually a two-blade propeller. Once built, the pilot cannot change the angle of the propeller. Fixed-pitch propellers are generally made of aluminum alloy or wood.
Fixed-pitch propellers are a compromise of best take-off and climb performance and cruise. Many single-engine aircraft use fixed-pitch propellers. The advantages to these propellers are they are less expensive, and they are a simple operation. This type of propeller does not require any control inputs from the pilot in flight.
Fixed-pitch propellers are further categorized into two categories: metal propellers and wooden propellers.
In 1940, the military popularized the use of solid steel propellers. Very few of these still exist, but were very efficient for the time.
Craftsmen create modern metal propellers from high-strength, heat-treated, aluminum alloy. The result was extremely successful and became the future of the propeller creation.
Metal propellers are now used extensively for all types of aircraft. The metal propeller’s general appearance is similar to the wood propeller, but the sections are generally thinner.
Additionally, metal propellers offer significant advantages to wood propellers. Aluminum alloy makes these incredibly strong and durable propellers. Metal propellers today are heat treated to enhance their natural properties and make them less prone to warping from heat or cold.
Today, it isn’t easy to find an airplane propeller made of anything but metal, for a good reason!
Before World War II, personal and business aircraft almost exclusively used wooden propellers.
It’s important to note that a wood propeller is not cut from a solid block.
A wood propeller is several separate layers of carefully selected and prepared wood. The most common woods used in making these now-vintage wooden propellers were black walnut, sugar maple, yellow birch, and black cherry.
The use of lamination of wood will reduce the tendency for the propeller to warp. For standard one-piece wood propellers, five to nine separate laminations, about ¾-inch thick each, are used.
Because of the advancements in crafting metal propellers, wooden propellers are not common today.
The function of ground-adjustable propellers is similar to that of fixed-pitch aircraft propellers. The pitch, or angle, can only be changed when the propeller is not rotating.
A clamping mechanism holds the propeller blade in place. Loosening this mechanism allows the angle to be changed.
After tightening the clamping mechanism, the propellers’ pitch cannot be changed in flight to meet varying flight requirements. With such limitations, present-day airplanes don’t commonly use the ground-adjustable propellers.
Additional refinements, such as reverse-pitch propellers (mainly used on turboprops), are included in some propellers to improve their operational characteristics. Almost all reverse-pitch propellers are of the feathering type.
A reverse-pitch propeller is a controllable propeller in which the pilot can change the angle to a negative value during operation. The reversible pitch feature aims to produce a negative angle that has thrust opposite the normal forward direction.
Typically, when the landing gear is in contact with the runway after landing, the pilot can move the propellers to a negative pitch (reversed), which creates thrust opposite the aircraft direction and slows the aircraft. As the propeller moves into a negative angle, engine power is applied to increase the negative thrust.
The negative pitch aerodynamically brakes the plane and reduces ground roll after landing. Reversing the propellers also reduces aircraft speed quickly on the runway just after touchdown and minimizes aircraft brake wear.
A reversible pitch aims to create a negative angle to manufacture thrust in the opposite direction held previously. Propellers may be repositioned to a negative pitch after the plane has landed to come to a complete stop.
Reversible pitch propellers are also used on floatplanes to allow the plane to be backed out of the docking area.
Test Club Propeller
A test club propeller tests and breaks in reciprocating engines. They provide the correct amount of load on the engine during the test break-in period.
The multi-blade design also has the advantage of providing extra cooling airflow during testing.
Even More Overwhelmed? Need Help With Your Aircraft Propeller?
No need to be overwhelmed at all of the different types of propellers and options for your aircraft! Contact the pros at Stockton Propeller for all your propeller repairs and overhauls. They are experts on servicing metal and composite propellers and are happy to assist you in meeting your needs!