Design of Self-Sealing Breakaway Coupling for Fuel Shut-Off Valve of Rotary-Wing Aircraft Considering Mechanical Fracture Characteristics

Abstract

A self-sealing breakaway coupling for a rotary-wing aircraft fuel shut-off valve is installed between the fuel tank-fuel supply pipe and fuel supply pipe-engine interfaces. This coupling separates into two parts if loading that surpasses a specific critical point is applied to the fuel supply pipe. This separation prevents secondary accidents by shutting off the fuel supply. At this time, the loading modes for coupling separation are bending and tensile. This coupling design follows the MIL-STD-1290A standard to meet design conditions considering fracture characteristics. In this study, the appropriate fracture pin diameter and fracture surface angle are obtained to satisfy design conditions considering fracture characteristics. We investigate the coupling fracture characteristics via finite element analysis and fracture surface experiments. To satisfy the loading conditions, the suggested design for the fracture pin is a 2.5 mm diameter and a fracture surface angle between 7.0 degrees and 8.0 degrees.