Some aircraft cockpits feature a large blue lever located next to the throttle. This the propeller controller, and is used to set the propeller and engine speed for an aircraft with a constant speed propeller. Constant speed propellers work by varying the pitch of the propeller blades, which alters the in-flight properties of the propeller. As the propeller blade angle is increased, it produces more thrust, but also requires more torque to spin the propeller, which slows down the engine. Inversely, when the blade angle is decreased, the torque required is decreased, and the engine speeds up.
Constant speed propellers are named such not because they always operate at the same speed all the time, but because the operator can set their RPM, which the propeller then maintains until the operator changes. During takeoff, high RPM is best to achieve maximum power, but during cruising operations pulling RPM back is better for fuel economy.
The propeller’s blade pitch is altered hydraulically by using engine oil. This is the same oil that goes through cylinders to keep them cool and lubricated, and is paired with a spring at the back of the propeller hub assembly that helps the propeller return to a low pitch/high RPM setting. For most single-engine airplanes, there are stops installed so that the blades cannot be fully feathered or flattened.
The job of governing the movement of the propeller falls to an assembly called a governor. The governor moves oil back and forth through the propeller hub to make sure the propeller is at the pitch and speed you want. The governor is comprised of:
The greatest design strength of helicopters, the horizontal main rotor blade that lets the aircraft take off and land vertically, is also its greatest design issue: as the main rotor spins, it generates enormous amounts of torque, which, if left unopposed, will cause the rest of the helicopter to spin as well, rendering it completely uncontrollable. To balance out this torque, the vertical tail rotor spins in opposition of the main rotor to cancel out the rotary effect.
Like the main rotor, the tail rotor consists of several small airfoils, or blades, usually made from aluminum cores covered in carbon fiber composite materials and can be made with both symmetrical and asymmetrical construction. Tail rotors are powered by the helicopter’s power plant via shaft and bearings and rotate at a speed proportional to the main rotor’s. In both piston and turbine-powered helicopters, the main rotor and tail rotor are mechanically connected through a freewheeling clutch system, which allows the rotors to keep turning and providing lift and thrust in the event of engine failure.
Alternatives to the tail rotor design do exist. McDonnell Douglas has developed the NOTAR (NO TAil Rotor) system, which uses a variable pitch ducted fan driven by the helicopter’s powerplant, mounted inside the fuselage ahead of the tail boom. When exhaust passes through the tail boom to the end, it is expelled out one side, fulfilling the same role as a tail rotor. Other solutions involve multiple tail rotors operating in opposition of one another to cancel out their respective torque. The tandem/transverse rotor system, typically seen on heavy lift and transport helicopters, uses two non-overlapping main rotors that turn in opposite directions.
Coaxial rotors use two rotors that are mounted on the same axis, but spin in opposite directions. Finally, intermeshing rotors turn in opposite directions, and rotate within each other’s planes without colliding thanks to mechanical linkage that prevents them from trying to occupy the same space at the same time.
Like all aircraft parts, tail rotors need regular inspections and maintenance. Many parts are considered life-limited, meaning that they are replaced after a certain number of flight hours, regardless of that part’s condition.
How is an aircraft capable of flight? A key component in their ability to fly is the type of engine the plane houses and the parts that construct the engine. Aircraft engines are designed with the same core components across different planes, including fans, compressors, combustors, turbines, and nozzles. When these parts operate in unison, flight is possible. If any one of these parts was missing, then flight wouldn’t be achievable. The individual parts of the engine may be small be they contribute to a wholesome larger picture. Many aircraft today utilize gas powered turbine engines because of their efficacy, reliability, and performance. There are four main types of turbine engines in operation today: the turbojet, turboprop, turbofan, and turboshaft engine.
A turbojet engine produces thrust by ejecting a high energy gas stream from the engine exhaust nozzle. Air is directed into the engine through an inlet at the front of the plane, which is then heated by a compressor. Fuel is added in the combustion chamber and then ignited, expanding the air and adding energy to the exhaust stream. The turbine extracts energy from the exhaust stream in order to operate the compressor. The remainder of the exhaust energy is turned into thrust, aided by the exhaust nozzle. As gas passes through the exhaust nozzle it is accelerated into high speeds as it expands, resulting in propulsion. Turbojet engines are relatively simple in design, occupy little space, and are capable of very high speeds. On the other hand, this engine requires a considerable amount of fuel and tends to be louder than other engines.
A turboprop engine uses a gas turbine to turn a propeller. Propellers are efficient in flying and can be used with nearly any kind of engine. The core of a turboprop engine is relatively similar to a turbojet engine. A main difference is that instead of expanding all the hot exhaust through the nozzle to produce thrust, most of the energy is re-routed in a ducting system to power the turbine. Turboprop engines are mainly used for low speed aircraft such as cargo planes and general aviation aircraft.
Turbofan engines are most commonly found on commercial aircraft. They combine the best of both worlds between turbojet and turboprop engines. They work by attaching a ducted fan to the very front of a turbojet engine. This fan has many functions as it lowers the noise output of the engine, helps keep the engine cool, and creates additional thrust. As air enters the fan, it gets divided into two separate streams. One stream act as bypass air and flows around the engine, while the second stream passes through the engine core. The bypass air is accelerated by a duct fan, which ultimately produces more thrust. Turbofan engines are much quieter than turbojets and are very fuel efficient for commercial flight.
The last style of turbine engine is the turboshaft. Instead of producing thrust, these engines utilize shaft power and machinery to provide movement. These engines are typically found in small but powerful aircraft such as helicopters as they have much higher power-to-weight ratio.
The standard propulsion system seen on commercial aircraft is a twin turbofan gas turbine engine assembly. Airbus and Boeing utilize this dual engine system on most of their aircraft. The fuel-efficient assembly is widely used in high-speed transport and has helped propel the aerospace industry to what it is today (pun intended).
Standard gas turbine engine functionality is powered by a specific set of turbomachinery including a compressor, a combustion area, and a turbine unit. Turbofan engines add an additional fan in front of the engine, and an additional fan turbine behind it. Let’s examine how a turbofan engine works.
Turbofan engines have two separate shafts— one houses a fan and fan turbine, and the other houses a core compressor and core turbine. This system is called a two-spool engine because of its dual shaft arrangement. The fan serves two main functions that are critical to turbofan fuel efficiency. Its multi-blade construction increases the velocity of the incoming air stream and directs some air into the core compressor. Air that flows from the fan and around the engine instead of into the core compressor is called bypass air. Because the velocity is increased, this airflow provides additional thrust on essentially the same amount of fuel.
The core turbine is the driving unit of the engine. The turbine is made up of two types of airfoil blades: high-speed rotating blades called rotors, and stationary blades called stators. This configuration keeps airflow from deviating around the axis. The power turbine utilizes hot air flow from the burner to power the compressor.
The core compressor increases the pressure of air that is routed into the assembly. The compressor is powered by the rotation of the turbine and is located on the same shaft. The compressor pressurizes air flow using a centrifugal or axial flow rotating method. It is most common for a commercial jet to use a multistage axial compressor, which directs air in parallel to the axis of rotation of the shaft through a series of airfoil cascades. The compressor, like the power turbine, uses rotors and stators to increase pressure and direct airflow.
Diesel engines are internal combustion engines. The main difference compared to other internal combustion engines is how the fuel is ignited. Hot air from the compressor is transferred to the combustion chamber, but instead of requiring an ignitor, the air is hot enough that when the fuel is injected, it spontaneously combusts. Spontaneous combustion is the result of two things, the self-ignition temperature of diesel and the compression ratio of diesel engines.
Because the fuel is injected before it ignites, there is an uneven distribution of fuel. Diesel engines operate with a diffusion flame— the oxygen diffuses into the flame. The torque produced is controlled through the manipulation of the air ratio. Diesel engines rely on changing the amount of injected fuel and the air ratio is typically high. Its high expansion ratio makes it the highest thermal efficiency combustion engine— it enables heat dissipation by the excess air.
Some of the common advantages of diesel engines are:
Some of the common disadvantages of diesel engines are:
Diesel engines have a wide variety of applications including passenger cars, commercial vehicles, locomotives, watercraft, and construction equipment. Just like every other component of an engine, the pros and cons of a diesel engine need to be evaluated based on their applications.
A Swiss engineer, Alfred Buchi, patented the turbocharger in 1905, but it wasn’t used until 1923 when it was incorporated into large marine engines used in the construction of two passenger liners. This was commissioned by the German Ministry of Transport. Turbochargers were first used in production aircraft engines in the 1920s but were kept out of widespread use due to the need for high-temperature metals for the turbine. Using turbochargers can improve an engine's fuel efficiency, reduce emissions, and generate more power.
Turbochargers, or turbos, utilize waste power to increase an engine's efficiency. The three main parts of a turbocharger are the turbine, the compressor, and the central hub. The turbine converts the heat energy from the exhaust into a mechanical rotation. Since the compressor and turbine are connected to the same shaft, the compressor also rotates. Therefore, the turbine is powering the compressor. Turbines and compressors are turbomachinery; they transfer energy between a rotor and a fluid. However, a turbine transfers energy from a fluid to a rotor and a compressor transfers energy from a rotor to a fluid. Essentially, what happens is that a turbine converts energy from a fluid flow into useful work.
A turbochargers performance is related to its size. Smaller ones can spin quickly but don’t perform as well at high acceleration. Larger turbochargers require more heat and pressure to spin the turbine, which creates lag at lower speeds. To balance the benefits of both sizes, combinations of the two were made. They are twin-turbochargers, twin-scroll turbochargers, and variable-geometry turbochargers.
Twin-turbos have two separate turbochargers that operate in a sequence or in parallel. Both turbochargers are each fed half of the exhaust in a parallel configuration. In a sequential configuration, one turbocharger operates at low speeds and the second operates at predetermined engine speed or load. They reduce turbo lag but use an intricate set of pipes. This setup is used because the pressure from one turbocharger amplifies the other. A bypass valve is used to regulate the exhaust flow. Twin-scroll turbochargers have two exhaust gas inlets and nozzles. The smaller one is used for quick response and the larger one is used for peak performance. Variable-geometry turbochargers use moveable vanes that adjust the air-flow to the turbine. It improves fuel efficiency without producing higher levels of turbocharger lag.
Aircraft bearings require a special grease in order to operate properly and ensure longevity. Automotive grease can be used as a cheap alternative, but it is not recommended if you want all your parts to stay reliable and in pristine condition. After all, the needs of an automobile and the needs of an aircraft are entirely different. In terms of aircraft maintenance, there are three types of grease that are highly recommended: Mobil SHC100, Braycote 622, and ROYCO 22CF.
Mobile is a reliable and well-known brand with a variety of products— and for the aviation industry, they have the SHC100. The SHC100 aviation grease is a multi-purpose synthetic product that comes in a tube. Being multi-purpose, it’s perfectly suitable for greasing aircraft bearings. This grease is recommended for heavy load, high-speed applications such as landing gear bearings, wheel bearings, sides, and joints. This grease also provides protection from damage in operating temperatures of -54? to 177?. It’s a unique blend of a polyalphaolefin base and a lithium soap thickener, making it also resistant to water washes.
Royce is another great brand when looking for aircraft grease. The ROYCO 22CF is an inorganic gel-type grease that protects aircraft from friction at a wide range of operating temperatures. This grease is used for instruments, gearboxes, rotor bearings, actuators, general airframe applications, and wheel bearings. The grease also contains additives the prevent oxidation and corrosion.
Castrol Braycote 622 is a good hydrocarbon-based synthetic oil that doesn’t contain additives or soap thickeners. This grease is a good option for operating temperatures up to 177?, water resistance, extreme pressures, and strong vibrations. This grease goes above and beyond conventional greases making it suitable for helicopter rotor bearings, alternator bearings, high-speed bearings, and wheel bearings. Grease selection depends on the type of application in which the grease needs to be applied to.
Just Parts Unlimited, owned and operated by ASAP Semiconductor, should always be your first and only stop for all your aircraft grease and bearing needs. Just Parts Unlimited is a premier supplier of aircraft bearings. Whether new or obsolete, we can help you find all the parts you need 24/7x365. If you’re interested in a quote, email us at firstname.lastname@example.org or call us at +1-412-212-0606.
It’s always easy to mistake two similar things as the exact same thing. Jam and jelly, weather and climate, and pumps and compressors. While sometimes misunderstanding the difference is no big deal, other times it means that you just bought the wrong mechanical device for your project.
Pumps and compressors are both mechanical devices used to move hydraulic fluid through a system, from point A to point B. They work by utilizing high pressures and serve many different functions. However, they’re completely different. A pump can move both gases and liquids and a compressor can only move gas.
Pumps are machines that move fluids, liquid or gas, from one place to another. The two basic types of pumps are positive-displacement and centrifugal. Positive-displacement pumps move fluid by moving and forcing a fixed amount of it into a discharge pipe; they include reciprocating pumps, power pumps, steam pumps, and rotary pumps. Centrifugal pumps convert input power into kinetic energy by accelerating liquid in an impeller. The most common centrifugal pump is the volute pump which lets fluid enter the pump through the eye of the impeller and rotates at high speed, creating a vacuum that in turn creates more suction to draw in more fluid.
Compressors are machines that squeeze a gas into a smaller volume and pump it somewhere else at the same time. The two basic types are the positive-displacement and the dynamic or negative-displacement. Most compressors are positive-displacement compressors, they force air into a chamber and compress the air by decreasing the volume. Positive-displacement compressors include rotary compressors and reciprocating compressors. Reciprocating or piston-type air compressors pump air with pistons and one-way valves to guide air into the cylinder chamber. Dynamic or negative-displacement compressors typically use a spinning impeller to generate centrifugal force to accelerate or decelerate captured air in order to pressurize it.
Even more important than knowing which machine to use is knowing how to maintain and repair them. At Just Parts Unlimited, owned and operated by ASAP Semiconductor, we’re a premier supplier of aerospace and aviation parts and components. Whether you’re in the market for pumps or compressors, new or obsolete and hard-to-find, we have it all in our vast ready-to-ship inventory. For more information or a quick quote, visit us at www.justpartsunlimited.com or call us at +1-412-212-0606. We’re available and ready to help 24/7x365.
Humans travel a lot. Whether by car or by plane, as a collective, humans travel a lot. And in doing so, we’ve driven an entire industry without even knowing it. To be specific, the wheels and brakes industry. From manufacturing to maintenance and servicing, the wheels and brakes of aircraft and ground vehicles alike have begun to develop at alarming speeds.
Today, in addition to hydraulic brakes such as steel and carbon, there are all-electric brakes and electro-hydraulic brakes. Currently, the market is saturated with carbon and electro-hydraulic brakes, effectively ending the widespread use of steel brakes and “old” hydraulics. However, with the demand for brakes being directly correlated to worldwide passenger traffic and cargo trade, perhaps composite and all-electric brakes will begin to replace them too. After all, innovation is driven almost purely by demand. An increase in air passenger traffic ensures the need for lighter, more durable, and cost-efficient options.
A polymer is a macromolecule composed of repeat units that are linked. The molecules are light, have a broad range of properties making them perfect to use for aircraft bearings. These bearings have extremely strict requirements for performance and quality. The bearings must withstand tough weather conditions, extreme cargo loads and extreme fluctuations in temperatures. In the aerospace industry, Ultracomp, CJ, Tristeel, and Rulon are the four most common polymers. Recently, polymers are replacing bronze and metals in the fuselage, steering, and wings. The use of polymers in aircraft creation allow for the aircraft to be significantly lighter, contributing to low maintenance costs and quick repair times. The polymer molecules have great temperature and vibration properties, making it a great material for aircraft.
Ultracomp UC 200 bearings have an excessive compressive strength of over 54,000 PSI with unique geometry that joins fixtures of gear doors, landing gears, fuselage components and high pivot points. Rulon LR is used for landing wear bands for oleo struts. Rulon can easily tolerate high loads and extreme environmental exposure. Try steel bearings allow for easy maneuverability of steering gear and aircraft towing vehicles because they offer dual-layer designs to increase properties. These applications extend the life of the bearing and allow for less maintenance over time. Polymer macromolecules have truly changed the aerospace industry in terms of efficiency.
Just Parts Unlimited owned and operated by ASAP Semiconductor, should always be your first and only stop for all your hard to find landing components. Just Parts Unlimited is the premier supplier of FSG bearing components, whether new, old or hard to find, we can help you locate it. Just Parts Unlimited has a wide selection of parts to choose from and is fully equipped with a friendly staff, so you can always find what you’re looking for, at all hours of the day. If you’re interested in obtaining a quote, contact the sales department at www.justpartsunlimited.com or call +1-412-212-0606.