Forgings for Affordable Airframe Structures

Aluminum forgings are desirable in helicopter structural applications because of their superior mechanical properties. However, forgings have lead times and tooling costs that exceed the schedules and budgets of many programs, precluding their use. These conditions have driven designers of new components to specify aluminum plate, which is more readily available, and have virtually no tooling costs. This practice also occurs in the after market segment of the aerospace business, where depots are forced to substitute plate for forgings or loose aircraft availability. The problem is that plate properties are no match for those of forgings and the structures require heavier cross sections or reductions in performance life. Other drawbacks are higher waste (95% of the plates volume ends up as chips) and increased machining hours (up to 50% higher when compared to forged parts) even with high speed machining equipment. Sikorsky Aircraft Corporation is working with the Forging Defense Manufacturing Consortium (FDMC)i and Ohio State University to institutionalize improvements to the forging process that will make this material selection practical for new and re-capitalized structural airframes. This paper will discuss the technologies being developed to reduce the forging lead times to that of plate and for affordable order quantities of less than 4 parts.