types of propellers

Types of Propellers : Fixed-Pitch, Ground-Adjustable, Reverse-Pitch, & Test Club

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.

Stockton Propeller is a full-service governor, metal, and composite propeller shop in Stockton, California. If you need a composite propeller repair or overhaul, contact Stockton Propeller first.

Now, let’s look at some additional types of propellers – and their differences.

Fixed-Pitch Propellers

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.

Metal 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!

Wooden Propellers

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. 

Ground-Adjustable Propeller

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.

Reverse-Pitch 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! 

types of propellers

Types of Propellers : Constant-Speed, Controllable-Pitch, & Feathering

When the Wright brothers first dreamt of the aerodynamics of flight, their designs looked different from planes today. We’re going to look more in-depth at varying types of aircraft propellers used on present-day aircraft. 

The propeller is the airplane part that converts rotational energy generated by its power into propulsive force. Propellers are an essential part of any aircraft. Without them, an airplane cannot fly. It’s imperative that, when choosing propellers for your plane, you take all of the conditions of operation into consideration. These include takeoff, climb, cruising, and high speed. 

Today, there are many types of aircraft propellers available. The simplest of these propellers is either the fixed-pitch or the ground-adjustable propeller. More complicated propellers include controllable-pitch and complex constant-speed systems (automatic systems). 

Stockton Propeller employs the experts in propeller repair. If you need to have your propellers inspected or overhauled, look no further than Stockton Propeller!

But first, let’s peek at some of the most common types of propellers – and their differences.

Constant-Speed Propellers

The constant-speed propeller utilizes a hydraulically- or electrically-operated pitch-changing mechanism controlled by the governor. The pilot, using the RPM lever in the cockpit, adjusts the setting of the governor. During operation, the constant-speed propeller will automatically change its angle to maintain constant engine speed. If engine power increases, the blade angle increases, allowing the propeller to absorb the additional energy while RPM remains constant. The same goes for the reverse. If the engine power decreases, the angle decreases, making the propellers take less air, steadying engine RPMs. The pilot selects the engine speed required for any particular type of operation.

Constant-speed propellers increase angle when the airplane dives and decrease angle when it climbs. These changes are due to the flight’s changing load. As such, the governor tries to keep the RPM constant. The propeller’s governor is the mechanism that allows a constant-speed propeller to work. A propeller governor senses the aircraft’s speed and changes the propeller’s angle to maintain a specific RPM. This change is accomplished by increasing or decreasing the oil pressure going to the propeller. A governor doesn’t consider the aircraft’s operational conditions.

As the plane goes into a dive, the propeller’s angle increases. This increase prevents overspeeding, and the power output doesn’t change – since there is no change to the throttle settings. The reverse happens during a climb. The governor will decrease the blade angle to keep the rpm at the desired setting. 

High-quality constant-speed propeller systems respond to small variations to ensure constant engine RPM stays consistent throughout the flight.

Each constant-speed propeller needs an opposing force that operates against the governor’s oil pressure. 

Multi engine and aerobatic propellers use counterweights mounted to the propeller blade to move in the high-pitch direction as the propeller turns. Some also use air pressure and springs to move the blades toward high pitch. Oil pressure from the governor will move the blades toward low pitch. 

Most single engine propellers use springs and an aerodynamic twisting moment to move the blades toward low pitch and oil pressure to move the blades to high pitch.

Controllable-Pitch Propellers

As the name suggests, the pilot can change a controllable-pitch propeller‘s pitch or angle during flight while the propeller is still running. The advantage of this is the alteration of the propeller’s angle to meet flight conditions. The pilot can change the propeller’s pitch in flight or operate the engine using a pitch-changing mechanism operated hydraulically or electrically.

The controllable-pitch propeller allows for a change of angle while the propeller is still rotating. This change enables the propeller to assume an angle that gives particular flight conditions the best performance. The pitch positions may be limited in number, as they are with a two-position controllable propeller. Or the pilot can adjust the pitch to any angle between the minimum and maximum setting. The use of controllable-pitch propellers makes it possible to attain the desired engine RPM for any particular flight condition.

It is easy to confuse these controllable-pitch propellers with constant-speed propellers, but the two are very different. 

Controllable-pitch propellers allow the propeller angle to be changed while the propeller is turning. But, the propeller must be changed manually by the pilot. The propeller’s angle will not change until the pilot alters it manually. The pitch on a constant-speed propeller can change automatically.

With the controllable-pitch propeller, the pilot changes the angle directly in flight. The angle will not change automatically, only when the pilot manually changes it. 

Feathering Propellers

Multi-engine aircraft use feathering propellers, reducing propeller drag to a minimum under engine failure conditions. A feathering propeller is a type of constant-speed propeller used on multi-engine aircraft. 

Feathering propellers have a mechanism to change the pitch to an angle of approximately 90 degrees. Usually, a propeller is feathered when the engine fails to produce the power needed to turn the propeller. By angling the propeller parallel to the direction of flight, the drag on the aircraft reduces. With the propellers parallel to the flight line, the propeller stops turning, and minimum windmilling, if any, occurs. 

Almost all small feathering propellers use oil pressure to take the propeller to a low pitch, while counterweights, springs, and compressed air take the propellers to a high pitch. Since the propellers would go to the feathered position during a shutdown, latches lock the propeller in the low-pitch position as the propeller slows down at shutdown. These can be external or internal, within the propeller hub. Centrifugal force holds the latches during a routine flight to ensure they don’t stop the propellers from feathering. Latches prevent excess load on the engine and starter at startup. If the propeller were in the feathered position during an engine start, it would place the engine under an undue burden during a time when the engine is already subject to wear.

Overwhelmed? In Need Of Propeller Repair? Just have questions?

Constant-speed, controllable-pitch, feathering… There’s no need to be overwhelmed at all of the different types of aircraft propellers! (Besides, we haven’t even covered all of them yet.) Please keep reading for our next blog post, where we’ll be continuing with more details about different types of propellers. 

In the meantime, Stockton Propeller employs the experts in composite propeller repair. If you need to have your propellers inspected or overhauled, look no further than Stockton Propeller!