TECHNOLOGY AREAS: Air Platform, Materials/Processes

ACQUISITION PROGRAM: PMA-274, VH-71 Presidential Helicopter Program

OBJECTIVE: Develop innovative designs, materials and manufacturing processes to produce advanced helicopter masts (main rotor shafts) to meet future Navy mission requirements.

DESCRIPTION: USN rotorcrafts operate in extreme environments under adverse conditions. 4000-series low alloy steels are commonly used in helicopter masts, however they require the use of coatings (including but not limited to toxic cadmium-based coatings) for environmental protection. Due to the increased operational demands, in addition to enhanced environmental protection, improved resistance to stress corrosion cracking and fatigue is desired for the next generation rotorcraft weapon systems.

Recent technology advancements in design techniques, metallic and non-metallic materials and manufacturing methodologies provide the opportunity to substantially upgrade helicopter masts. An innovative approach is needed to identify potential technology insertions for future weapons systems. Materials selection, process requirements, and finishing recommendations are needed to define the manufacturing and production (M&P) portion of the component specification. Procedures that are consistent with current processing paths and a material that is a drop-in replacement for baseline steels are highly desired.

Technologies that increase performance over existing industry standards must maintain fleet safety, reliability, and affordability. These advanced helicopter masts should easily replace today's designs without significant impact to manufacturing practices and qualification procedures.

PHASE I: Determine the feasibility of replacing existing helicopter mast with materials and processes that will enhance performance.

PHASE II: Build and test helicopter mast prototype to verify manufacturing feasibility and perform static testing to demonstrate functional properties.

PHASE III: Complete component qualification and transition across USN platforms as appropriate working with helicopter manufacturers.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The requirements of helicopter shaft materials are shared between government and commercial uses. Strong commercial potential is expected as a result of efforts on military aircraft.

REFERENCES:
1. http://www.compositesworld.com/articles/composites-take-off--in-ltigtsomeltigt-civil-helicopters.aspx

2. Hirko, A. G. and Soffa, L. L., "Inertia welding of nitralloy N and 18 nickel maraging 250 grade steels for utilization in the main rotor drive shaft for the AR-64 military helicopter program ," in AGARD Advanced Joining of Aerospace Metallic Materials 9 p (SEE N87-17051 09-37); 1986

3. Ingle, R B and Ahuja, B B, An Experimental Investigation on Dynamic Analysis of High Speed Carbon-Epoxy Shaft in Aerostatic Conical Journal Bearings," Composites Science and Technology," Vol. 66, no. 3-4, pp. 604-612. Mar. 2006

4. Department of Transportation. Journal of Nondestructive Testing. Vol. 12, no. 6. June 2007

5. Yeo, H and Shinoda, P M, "Investigation of Rotor Loads and Vibration at Transition Speed," AHS International, 58th Annual Forum Proceedings - Volume I, Montreal, Canada; United States; 11-13 June 2002, pp. 1175-1199

KEYWORDS: High Strength Steel; Advanced Alloys; Corrosion Resistance; Helicopter Mast; Manufacturing

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