A broad range of aerospace manufacturing processes and materials are used in producing AeroComposites components and propellers. Processes include forging of hub housings, CNC machining, electro-chemical deposition, shot peen, heat treat, grit-blasting, cleaning, surface passivation, acid etch, bond prime preparation, adhesive coatings, die penetrant inspections, blade and assembly balance, and blade resin transfer molding. At the heart of AeroComposites blade manufacture is the VARTM (Vacuum Assisted Resin Transfer Molding) process used in producing its composite blades. AeroComposites' VARTM is the most advanced fabrication technique available today for making composite propeller blades and overcomes the many shortcomings inherent with other composite propeller blade manufacturing methods. AeroComposites has taken existing VARTM technology to a new level by selecting a state-of-the-art toughened resin and adding its own proprietary processes and techniques for which it won an International Composites Industry 1st Place Prize/Award in 2003. the Award was for Composites Quality and Process Innovation.  The process innovations insure controlled fiber alignment/content, complete and total resin penetration, co-curing of all structural blade elements, and minimum possible levels of internal porosity in the composite blade laminate. The innovations optimize blade inter-laminar shear strength. The resulting molded AeroComposites' blades are repeatable, of consistent quality, and are of very high strength and stiffness.

The aerospace components/materials used in making AeroComposites' propellers are carefully selected and controlled for quality, material properties, and dimensional tolerances using material specifications, design drawings, and incoming and in-process parts inspections/tests. Resulting blades are a hybrid composite structure that include fiberglass braided socks and carbon structural plies in a resin matrix, combined with high-strength non-corrosive metal parts at the blade root and leading edge, all precisely positioned/held over an internal structural high density foam core during fabrication.

Composite Blades

AeroComposites propeller blade manufacture begins with a dry lay-up consisting of 1) a molded, pre-cured, high density, closed-cell high density foam core, 2) multiple plies of high-strength, uni-directional carbon fibers, sandwiched between successive layers of pre-braided fiberglass socks, and 3) high strength, corrosion-resistant stainless steel, blade retention rings. These components are integrated precisely according to the blade structural design for the rated engine horsepower. Each finished blade will have the correct fiber content and ply alignment at every blade radial station, providing many times the structural strength required to resist bending and centrifugal loads generated in service.

The blade lay-up then proceeds to final assembly where an external nickel alloy leading edge sheath and external "Astro-Strike" (lightning protection) expanded aluminum mesh are installed on the dry lay-up. The blade assembly is then placed in the VARTM mold followed by liquid injection of an advanced, toughened epoxy resin. The detailed process for molding blades is proprietary and involves many critical and carefully controlled computer automated steps that monitor the injection rate and quantity of resin, mold heating and cooling cycles/rates, pressure/vacuum cycles, and the precise alignment of the fiberglass and carbon structural plies.

After the VARTM blade molding process has been completed, the blade is ready for removal from the mold, cleanup of residual resin flashing, molding on of a durable composite collar at the blade root that incorporates machined snap-ring and O-ring grooves, and attachment of a metal root closure cup with provisions for the blade pitch change pin assembly, and installation of an internal balance tube. The final step involves applying a passivation coating to the "Astro-Strike" mesh followed by a high quality and durable paint finish to the blade.  Custom paint designs available for AeroComposites blades are outstanding.

Constant Speed Hub

AeroComposites' hub fabrication begins with an aerospace quality, high strength aluminum forging (100 lbs) that is first machined (50 lbs) to rough dimension to a "lolly-pop" shape.  The forging geometry/dimensions for both 2-bladed and 3-bladed propellers have been selected to allow machining of finished hubs to support most any aircraft/engine/cowling configuration. Following finish-machining of the hub (13 lbs) using a 4-axis CNC milling machine, the hub is heat treated, shot-peened in all critical areas to enhance fatique strength, dye penetrant inspected, bearing races areas final machined, acid etched to remove any surface tooling metal impurities that could lead to corrosion, passivation coated, and finally painted.  Smaller parts used in the constant speed hub assemblies are manufactured using a number of processes that include the use of CNC milling and lathe operations, hydraulic forming, punch press, screw machines, etc.

Spinners

AeroComposites' propeller sales are for both installation on new experimental aircraft (forward fit) under construction and on operational aircraft, where aircraft owners want improvements in propeller performance (e.g. safer, lighter weight, faster cruise, more durable, vibration free operation). Spinner dimensions and installation engineering details for many experimental category aircraft (e.g. Van's RV's, Lancair, Seawind, Glasair, Glastar, Express, Stallion, F1 Rocket) installations have now been defined. AeroComposites hub forgings (with long integral forged extensions) allow for machining of the rearward hub extensions (either short or long) to meet installation requirements for most any aircraft/engine configuration.

AeroComposites' spinner kits include a nose cone, forward bulkhead, rear bulkhead (or back-plate), and all hardware required for finishing the spinner assembly (e.g. rivets, doubler plates, bolts/washers) and installing it on the aircraft. AeroComposites hubs are designed with integral machined multi-point bosses for spinner attachment, that avoids spinner cracking due to in-flight vibrations.  The spinner cone and bulkheads are generally made of light-weight composite materials. Detailed instructions are provided with each kit for use by the builder in finishing the spinner assembly.

To minimize what can become a lengthy and tedious task for many builders, AeroComposites pre-aligns all key parts provided in its spinner kits. The nose cone and front and rear bulkheads are mounted on a representative hub bolted to a precision AeroComposites' turntable.  These parts are then precisely aligned to insure that the finished spinner assembly will turn on the propeller's axis with minimum eccentricity/wobble. All critical screw holes are indexed and line-drilled through the cone and rear bulkhead to insure alignment.  The forward bulkhead is then permanently installed in the spinner cone. Finally, the propeller blade holes are precisely scribed on the nose cone surface, facilitating builder hole marking, cutout and trim operations.  Proper scribing of the blade holes insure a close spinner/blade fit, throughout the blade pitch range at final assembly, which serves to minimize aerodynamic spinner drag. 

Propeller Assembly

First a propeller build parts kit is pulled from finished stores (blades, hub housing, and hub detail parts) where the complete assembly process is controlled through the use of process control sheets that detail specific requirements for that specific customer's order. The blades then receive a cleaning, passavation surface coating, followed by painting.  The propeller assembly process proceeds with static balance of the individual propeller blades as a set. Each blade is balanced to determine the heaviest blade in the set. Weight in the form of lead wool is then added (compressed in place, inside blade balance tube), in the lighter blade(s) making up the set, to bring the set of blades into balance. Negligable unbalance or blade twist varation is measured between AeroComposites' as-molded blades as a result of the precise and repeatable computer controlled VARTM blade molding process.

The build proceeds with the blades assembled in the constant speed hub together with the detail hub parts (e.g. links, bearings, cylinder, piston).  Blade low pitch and high pitch stop angles are measured at each blade's reference station and adjusted, as required, where all critical assembly data/dimensions is recorded. Note that with aluminum blades, a mechanical re-twisting of the actual aluminum blades is required to achieve equal pitch angles between blades.  Occasionaly a slight pitch angle (e.g. 0.1 degrees) adjustment of one of the AeroComposites blades is required.  This angle variation between blades can be the result of the stackup of small changes between hub detail parts or between the bonded position of the blade closure cups installed in the base of the blades.  A small change in blade pitch can be accomplished by simply by changeout of the pitch change link. 

The propeller pitch change mechanism is then activated pneumatically on the assembly stand to confirm proper pitch change actuation. The propeller is then statically balanced as an assembly with fastners safety-wired in place. The propeller assembly is then given a final inspection, paper work is checked for completeness and compliance with customer/propeller build requirements, and the propeller is then packaged in a specially fabricated and sturdy wooden shipping container in preparation for shipment to the customer.

Quality Assurance

The Quality Assurance Program (QA) at AeroComposites monitors/controls all aspects of component and propeller manufacture. QA begins with review/approval of procurement specifications and component drawings for completeness, and extends to supplier selection and quality audits at the suppliers location, on an on-going basis. All propeller components/materials received at AeroComposites go through an incoming inspection to insure material certifications exist where required, hardware conforms to purchase order specifications including critical dimensions, and parts are free of damage or manufacturing defects. Checks are made to insure that all in-process tests during blade manufacture have been conducted, data has been properly recorded (e.g. resin samples saved). The finished blade, prior to painting, is inspected to detect any defects or non-compliance. A unit history paperwork file is stored at AeroComposites for each customer propeller build that contains the manufacturing process sheets and in-process test data. The QA program in place at AeroComposites is consistent with accepted aerospace quality assurance systems/standards used in major corporations for commercial and military aerospace hardware.