M17.2 Propeller Construction PDF

AAE4110 Propeller M17(B1) Part B M17.2 Propeller Construction Rev 1 11/2022  M17.2 Propeller Construction – Construction and Material 08/2024 Rev1111/2022 >Construction methods and materials used in wooden, Rev...

AAE4110 Propeller M17(B1) Part B M17.2 Propeller Construction Rev 1 11/2022  M17.2 Propeller Construction – Construction and Material 08/2024 Rev1111/2022 >Construction methods and materials used in wooden, Rev composite and metal propellers;  PROPELLER CONSTRUCTION 08/2024 FIXED-PITCH WOODEN PROPELLERS Rev1111/2022 Laminated wood Rev Fabric sheathing Hub Leading edge Tip Shank Trailing edge Metal tip and leading edge protection  > FIXED-PITCH WOODEN PROPELLERS The wooden, fixed- pitch propeller is well suited for small aircraft 08/2024 Rev1111/2022 because of its lightweight, rigidity, economy of production, simplicity of construction, and ease of replacement. Rev Because many small aircraft have a variety of approved propellers for installation, aircraft owners or operators have the option of selecting the appropriate propeller for their operation. The two common options are a “climb prop” or “cruise prop”: Climb propellers generally have a lower pitch or shorter diameter that allows the engine to attain higher rpms. Cruise propellers are built with higher pitch angles and longer diameters and are well suited for cruise operations  Wooden Propeller > All wooden propellers consist of individual laminations of 08/2024 Rev1111/2022 wood, usually roughly 3/4 inch in thickness. Manufacturing of a wooden propeller consists of wood Rev selection, gluing, shaping and finishing. > Wood Selection not the choice of wood species but rather the careful selection of individual boards of wood. wood grain (annual ring orientation) was carefully matched to produce equal stiffness, or resistance to torsional deflection, in each blade. Following the matching of wood by weight and grain, the rough outline of the individual piece, based on its position within the propeller was cut out for gluing.  > Gluing Pre-selected boards were heated, warm glue applied to opposing surfaces, and multiple special clamps applied at short intervals along 08/2024 Rev1111/2022 the entire length of the blade, beginning at the hub. Clamps were left in place for 24 hours or more, then the rough form allowed to cure for several days before milling. Rev > Shaping Cross sectional templates used to determine exact shape along various distances from the center, or a variety of machines were created to accurately obtain the final shape, some producing multiple propellers in one process. As part of the shaping process, the center of the propeller was placed on a knife edge balancing device, and small amounts of wood were removed to obtain precise balance. At the completion of the final shaping, after inspection of the product, the final drill holes were created in the hub, and specification numbers stamped into the wood.  A wooden propeller is not constructed from a solid block of wood, but is built up of a number of separate layers or laminates of carefully selected and well seasoned hardwoods. 08/2024 Rev1111/2022 Many woods, such as mahogany, cherry, black walnut and oak, are used to some extent, but birch is the most widely used. Rev Rev 08/2024 Rev1111/2022  > Finishing The surface was smoothed with furniture scrapers or sanding materials, then in some cases, the tips were covered with fabric 08/2024 Rev1111/2022 and /or metal sheathing before multiple coats of varnish were applied. Many times the final balancing of the blades was actually accomplished by the uneven application of varnish. Rev  After the propeller blades are finished, a fabric covering is cemented to the outer 12 to 15 inches (30 to 38 cm) of each finished blade. A metal or composite tipping is fastened to the leading edge and tip of 08/2024 Rev1111/2022 each blade to protect the propeller from damage caused by flying particles in the air during landing, taxiing, or takeoff. Rev  The tipping also serves as an erosion strip to protect the leading edge of the propeller. 08/2024 Rev1111/2022 Metal tipping may be of terneplate, monel metal, or brass. Stainless steel has been used to some extent. The metal tipping is Rev secured to the leading edge of the blade by countersunk wood screws and rivets. The heads of the screws are soldered to the tipping to prevent loosening, and the solder is filed to make a smooth surface. Since moisture condenses on the tipping between the metal and the wood, the tipping is provided with small holes near the blade tip to allow this moisture to drain away or be thrown out by centrifugal force.  Metal Propellers > As technology progressed and aircraft engines are now producing more power, wooden 08/2024 prop blades became impractical and were soon replaced by ones crafted from steel and Rev1111/2022 aluminum alloy. > These offered lighter weight, can generate higher rotation speeds, better durability, and Rev are much easier to repair. > During 1940 , solid steel propellers were made for military use. > Modern propellers are fabricated from high-strength , heat-treated, aluminum alloy by forging a single bar of aluminum alloy to the required shape. > Metal propellers is now extensively used in the construction of propellers for all type of aircraft. > The general appearance of the metal propeller is similar to the wood propeller, except that the sections are generally thinner. > Metal propeller including aluminium propeller are usually pitch changeable whereas wooden propeller is usually fixed pitched.  08/2024 Rev1111/2022 Stainless Rev Steel Fixed Pitch Propeller Aluminium Alloy VP Propeller  ALUMINIUM PROPELLERS > Machine cuts a blank to 08/2024 Rev1111/2022 its rough shape. > Followed by hand Rev grinding  08/2024 Rev1111/2022 Rev Buffing/polishing Inspections for defects (Fluorescent) Rev 08/2024 Rev1111/2022 Rev 08/2024 Rev1111/2022  Advantages of Aluminum Props 08/2024 > To start, aluminum props are very economical, often Rev1111/2022 costing a third of what a comparable, stainless steel propeller will run. This is one of the top reasons why Rev they’re selected so commonly for aircrafts and are used by manufacturers, due to the lower cost. > Given their low cost of acquisition, it’s pretty common to see them used as a spare propeller as well such as a prop blade shearing off due to an impact while you’re out and about. > An aluminum propeller can also be easy to repair, especially when compared to a stainless steel propeller.  Disadvantages of Aluminum Props > Aluminum is a strong but flexible material, which is among 08/2024 Rev1111/2022 the reasons why it’s used in many types of aircraft. > However, this flexibility can cause the pitch on propeller Rev blade to change, which can reduce performance, especially on higher rotation speed at high speeds. > Aluminum blades are generally thicker than stainless propeller blades, which create more form drag. > The third disadvantage of aluminum propellers is that they are more likely to be damaged particularly running in sandy conditions  Manufacture of AlAl Propeller 08/2024 Rev1111/2022 Rev  Composite 08/2024 Rev1111/2022 Propeller Rev https://www.compositesworld.com/articl es/digital-tools-rtm-update-aircraft- propeller%283%29  Design Result > Composite design is customized to specific aircraft 08/2024 Rev1111/2022 performance goals and engine characteristics, while meeting stringent Federal Aviation Admin. (FAA) or EASA Rev type-certification requirements. > Resin transfer molding (RTM) process, using co-molded components, is faster and less costly than prepreg layup, enabling a wider market reach. > Composites lengthen blade life, because damaged material can be replaced during repairs, where damaged aluminum blades must be ground smooth, which eventually results in an undersized propeller.  > As with other parts of the airplane, composite materials and construction techniques have been adopted by the propeller manufacturers. They offer numerous advantages, especially for higher speed turboprop aircraft. 08/2024 Rev1111/2022 > The strength offered by composite blades in conjunction with lightweight and reduced sound levels have proven useful attributes. Similar to other composites used throughout the aviation industry, two essential Rev components are utilized to produce the blades: The matrix material and The fiber material. > The former is similar to an epoxy and is used to keep the strands of the fiber in position. > The fibers possess considerable tensile strength and provide vigour in terms of blade resiliency. > A number of propellers flown in aerobatics are composite because of their lightweight, low inertia, durability, and affordability.  > Composite blades typically begin at the blade root 08/2024 where they are formed Rev1111/2022 around the metal blade shank. Rev > Numerous layers of carbon fiber laminates are wound around a core. > An attached erosion strip, when included, provides protection against blade erosion.  Carbon Fiber Composite vs. Wood Core Propeller Blades 08/2024 Rev1111/2022 > Stronger Materials Our carbon fiber is up to 10X stronger than wood, offering uniform strength and integrity. Rev > Aerodynamic Advantages Laminated wood blades are significantly thicker than Hartzell composite blades, and thicker airfoils produce more drag. With our carbon fiber composite blades, you can expect aerodynamic advantages in every flight stage. > Durability Wedge retention system and stainless steel shanks are much more durable than the alternative aluminum/lag bolt design. The blades can be repaired in the field or at overhaul shops. > Better Performance shorter take-off distances, increased climb rates, faster cruise speed, excellent fatigue life and overall smoother operation  Dimension 08/2024 Rev1111/2022 comparison between wooden Rev core and composite propellers  > Composite vs Metal Propeller Lighter in weight 08/2024 Rev1111/2022 More slender design Corrosion free Rev Higher solidity – higher C-130 Hercules 1954 power absorption onwards. Aluminum alloy capability Slower speed – reduced noise Need extra lightning protection Lower damage tolerance Special repair skills C-130J Super- required Hercules 1999 onwards. Composite  Rev 08/2024 Rev1111/2022 >Questions?