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The Basic Aerodynamics of Flight

For those learning about the principles of aerodynamics, this article seeks to cover some of the basics. Like how does a propeller work on a plane, and what are the four forces of flight.

Aircraft are complex machines. Each part must work together not only to propel it forward but also to overcome gravity for it to fly. The four forces of flight include thrust, weight, lift, and drag.

If you are concerned that there is an issue with your propeller and want to have a propeller overhaul to optimize the aerodynamics, contact Stockton Propeller. Stockton Propeller is a full-service propeller overhaul and maintenance facility with the needed equipment and expertise to perform your needed maintenance and repairs.

Thrust

One crucial component of an airplane’s aerodynamics is the force of thrust. The propulsive force created by the propeller or rotor works to counteract the effects of two of the other four forces of flight — weight and drag.

Airplane wing and tail flying though a cloudy sky

Your airplane’s propeller generates thrust by utilizing the principle of Newton’s Third Law. Newton’s Third Law states that for every action, there will be an equal and opposite reaction. A propeller or jet engine pushing air to the rear will have the effect of moving the plane forward unless some other force halts it. 

The plane’s propeller will push enough air past it to cause the aircraft to move in the opposite direction of this force. The propeller must work with a high level of efficiency to provide the necessary thrust for takeoff and flight.

The amount of thrust needed will change throughout the flight. As explained below, the weight of the plane’s propeller is just one component of weight to overcome.

You must also accommodate the mass of the fuel needed to power the propeller flight. As the flight continues, fuel is consumed.  As the fuel is consumed, its mass is reduced.  As mass is reduced, less thrust is needed. 

Weight

Another of the four forces of flight is weight. Weight is the force caused by gravity.

This weight includes not only the aircraft itself, but also the mass of the cargo, fuel, pilot, and any passengers. Increased weight means that the aerodynamic forces of thrust and lift must also increase.Diagram of airflow over the wings of an airplane

In propeller flight, the weight of the propeller itself must be accounted for in the mass calculations. Also, weigh or estimate the weight of all cargo, fuel, passengers, and anything else loaded onto the aircraft.

If this weight is not accurately determined, it will affect the plane’s performance.  It will also result in miscalculating the fuel volume needed for the flight, and even the plane’s ability to take off safely.

If the plane cannot generate enough lift and thrust to compensate for the weight, then some weight must be removed. To reduce the excess load, replace materials with stable, yet lighter materials, or carry fewer passengers and less cargo.

Drag

Drag is a rear-facing force caused by the disruption of airflow over the wing, fuselage and other components of the plane. The force of drag must be overcome through the forward momentum of the aircraft. To reduce drag, you may also need to alter the design of the aircraft.

Think about the comparative wind resistance of something like a paper airplane vs. a cup held concave side toward the airflow. The pointed shape of the paper airplane allows the air to flow smoothly over its surface and wings. Paper airplane flying due to aerodynamic principles

On the other hand, the cup will catch the air and not allow it to flow past. Catching or trapping the airflow will result in much more drag. The plane’s shape will allow the air to continue in the direction it was initially flowing without much interruption.

When questioning how does a propeller work on a plane, consider the concept of drag resulting from all aspects of the aircraft. Examine the surface of the plane, as well as the position and shape of the propeller. Optimize the propeller blades to create the least amount of drag possible while creating enough power to propel the plane. 

Lift 

According to NASA, lift “is the force that directly opposes the weight of an airplane and holds the airplane in the air.” Every component of the airplane works together to counteract the effect of gravity on the plane. 

Even with an efficient propeller, a plane in propeller flight would not fly if the rest of the aircraft was not designed to generate lift. 

Lift is a complex and often misunderstood principle. Lift is the force produced by the changes in air pressure above and below the aircraft components, most specifically the wings. 

For lift to take place, a fluid or gas: in this case, the air around the plane is required. In addition to a fluid or gas, you also need a solid to deflect the flow — the airplane wings, flaps, ailerons, among others. The fluid or gas must also be in motion.Diagram of flow of air over a plane flying landscape

In order to understand how does a propeller work on a plane, you need to put the fluid in motion by propelling the aircraft through it.  Planes cannot take off without being powered to generate this initial forward momentum.

The curved shape of the wing creates lift by making the air move faster across the top of the wing and lowering the air pressure.  This reduced pressure results in less force pushing down on the wing while maintaining an upward force under the wing, creating lift.

How Does a Propeller Work on a Plane to Optimize the Forces of Flight?

The propeller, coupled with the engine, is what produces enough thrust to move a plane forward. Once the plane is moving forward, the remaining four forces of flight combine to provide the necessary lift to get the aircraft in the air.

These aerodynamic forces of flight, all working optimally together, result in an efficient and safe voyage.

If your propeller is not operating as efficiently as needed to optimize thrust, contact Stockton Propeller. Stockton Propeller is a full-service propeller overhaul and maintenance facility that can assess your plane and perform any necessary maintenance.

 

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Fixed Pitch and Other Propeller Types

When you first begin training to become a pilot, the amount of technical information and jargon can become overwhelming. You need to learn the principles affecting lift, the variety of regulations governing what altitudes you can fly at, and you need to get the answer to questions like where to go for fixed pitch propeller repair and other necessary maintenance.

While the amount of information may seem daunting at first, once the basic principles are understood, you can apply them to different types of aircraft and different types of flight.

One vital factor in deciding what sort of certification to gain is knowing what kind of plane you wish to fly using what type of propeller. There are several factors to be considered, including:

  • Will you be flying a single or multiple-engine aircraft?
  • Is there likely to be bad weather where you will be flying?
  • What is your budget?
  • How much automation do you want to have vs. hands-on control during all aspects of flight?

All of the above questions influence the choice of propeller to look for on your aircraft. The propeller impacts all areas of flight.

Pilots may choose to have the most state of the art propeller, which helps to automate more of the flying experience, or they may want to have more control for a more classic flying experience.

Read on to learn more about the different types of propellers available and which type is best suited for every kind of flying conditions. Contact Stockton Propeller for all your propeller repair and maintenance needs.

Fixed Pitch Propellers

A fixed pitch is the simplest type of propeller. It is linked mechanically to the engine, and many of the simpler, light aircraft use it. This simplicity makes these planes easier to fly in some sense as engine speed is directly linked to propeller speed.

Some limitations may apply to the use of this propeller.

The propeller’s angle is set in one position and remains in that position for the entire flight. This fixed position means that the propeller angle is the best estimate and compromise of positions for takeoff, landing, and flight. At times, however, this results in the engine not running at its most efficient.

closeup of a worn propeller on an old airplane

Fixed Pitch Propeller Repair

Fixed pitch propellers can run into occasional problems. One of those is vibration, which can take a toll not only on the aircraft but upon the passengers riding in the plane. This vibration can cause excessive noise as well as resulting in needed maintenance or repair.

If you need fixed pitch propeller repair, Stockton Propeller is a full-service facility in Northern California. We have the skills to maintain and repair a wide range of propeller brands. We also have experts in blade reconditioning and can ensure that your propeller is running at its best.

Variable Pitch Propellers

Unlike their fixed-pitch counterparts, variable pitch propellers can alter the propeller’s angle to suit the different flying situations. Varying the propeller’s angle means that the propeller is in the best position for takeoff, flight, or landing, as is needed.

One of the useful features of most variable pitch propellers is that they can use feathering in case of an emergency. When feathering is in use, the propellers turn parallel to the way the air is flowing. The turning stops the rotation of the propellers.

When a variable pitch propeller uses feathering, the goal is to add to the distance the plane can fly. In single-engine planes in an emergency where that engine has shut down, this may increase gliding distance. In a plane where one of several engines has shut down, this will decrease the effect of drag on the propeller and allow the other engines to take over more completely.

One of the simplest forms of variable pitch propeller is a two-speed version where there is one setting for takeoff and one for cruising. A more complex design is the “constant speed unit,” which works by self-governing the pitch angle rather than selection by the pilot.

close up of silver small plane propeller

Constant Speed Propellers

An improvement on the variable pitch propeller’s constant speed unit is the constant speed propeller. This innovation works to maximize the effectiveness of the engine. It functions to keep the engine at a continuous speed no matter what combination of factors is in play.

The pitch of the propeller adjusts according to the engine’s speed. When taking off or flying, the engine adjusts to meet the needs of the aircraft to maintain the required lift and thrust. The pilot can set a particular speed of engine rotation, and the governor acts to control the propeller’s pitch to preserve this instruction.

Reverse Pitch Propellers

Some variable pitch propellers are so advanced that they use what is known as negative blade pitch, or reverse thrust. These propellers can change their angle so that they can slow down the aircraft.

Changing the propellers’ angle to reverse the thrust is particularly important when landing on runways that are short or experiencing bad weather conditions, such as rain or ice.

The reverse pitch of the propellers, in effect, pushes against the forward momentum of the plane to shorten the length of taxiing. Some propellers can allow the plane to back up, like floatplanes on water.

Pilot leaning out towards the back of a small prop plane giving a thumbs up sign

Propeller Maintenance and Repair

Care of your plane’s components before any issues arise is vital to you and your passengers’ safety. Proper maintenance of all parts of your plane is crucial to its long term safety and longevity.

The propeller is no exception. Regardless of propeller type, maintenance should be performed on a regular basis, and some procedures require a professional shop to complete those tasks.

Stockton Propeller is a full-service propeller overhaul and maintenance facility with the required equipment and expertise to perform

  • both static and dynamic balancing,
  • metal repair and refinishing,
  • NDT testing, and
  • on-site etch and alodine surface prep.

Contact Stockton Propeller today to schedule an appointment, request a free quote, or discuss your specific propeller needs.