Fuel Tank Energy Attenuation through Fitting Optimization

The U.S. Army seeks improved fuel tank fittings for helicopters that meet crashworthiness requirements while reducing the overall weight of the system. In response to this need, Corvid seeks to mature the lightweight functionally-graded fuel tank fittings developed in Phase I. Fittings developed under Phase I demonstrated a reduction in stresses at the fitting-bladder wall of more than 30% while reducing mass in the fitting transition region by 58%. This outcome indicates that fewer reinforcement layers in the bladder wall are required to meet crash requirements while reducing system weight between 5-15% depending on geometry of the fuel tank and fittings. Design, fabrication, and validation testing of these fuel tank fittings will be performed to demonstrate this technology’s readiness level (TRL) up to 7. The Phase II effort will focus on developing fitting designs considering various fuel tank integration methods, materials, sizes, and locations. Modeling and simulation-driven optimization will be combined with Corvid’s expansive in-house computing resources to generate a diverse set of candidate functionally-graded fitting designs with a focus on reducing overall system weight. High fidelity computational physics (HFCP) models will be established for leading fitting designs integrated into the system-level fuel tank for accurate crash impact drop test analysis. These design and numerical validation efforts will be extended to both sub- and full-system fabrication and testing to demonstrate the fitting technology’s ability to meet the specifications under MIL-DTL-27422F. Corvid will accomplish these system integration and manufacturing efforts by partnering with METSS Corporation and Floats and Fuel Cells, Inc. (FFC), respectively. METSS leverages 25 years of materials development for lightweight, crash resistant fuel bladders to provide state-of-the-art fuel tank bladder wall material data and integration support. FFC will fabricate the sub- and full-system fuel tank specimens integrating the functionally-graded fittings developed under this effort. A capstone virtual system integration will be performed on a platform-specific fuel tank with the functionally-graded fittings developed throughout Phase II. Boeing, in collaboration with their ongoing Joint Aircraft Survivability Program (JASP) to minimize next generation rotorcraft fuel tank system weight and meet crashworthiness requirements, has been identified as a technology transition partner beyond Phase II. As such, Boeing has demonstrated interest in providing relevant data to support the capstone virtual integration on one of Boeing’s rotorcraft, such as the AH-64. Beyond Phase II, Corvid will continue this relationship with Boeing to mature next generation functionally-graded fittings beyond TRL 8, proceed with qualification efforts, and identify opportunities for technology insertion.