Volvo RM-12

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The Volvo RM12 is a low-bypass afterburning turbofan jet engine designed specifically for the Saab JAS 39 Gripen fighter. A version of the General Electric F404, the RM12 was produced by Volvo Aero (now GKN Aerospace Engine Systems), which created this advanced engine. Developed by Volvo Aero (now GKN Aerospace Engine Systems), the RM12 is a derivative of the General Electric F404-400, but with significant improvements. Key changes include greater reliability for single-engine operations, including more stringent birdstrike protection, increased thrust, and the adoption of a full authority digital engine control (FADEC) system. Several subsystems and components were redesigned to reduce maintenance demands. The air intakes of the engine were designed to minimize radar reflection from the compression fan, reducing the overall radar cross section of the aircraft. The F404's analogue Engine Control Unit was replaced with the Digital Engine Control – jointly developed by Volvo and GE – which communicates with the cockpit through digital data buses and a hydromechanical back-up for redundancy. Hydromechanical backup remains in the new Full Authority Digital Engine Control (FADEC) system, which Volvo began developing in 1996. General Electric produces 50% of the engine. Key components such as fan/compressor discs and case, compressor spool, hubs, seals, and afterburner are manufactured in Sweden, with final assembly taking place there. The JAS 39 Gripen relies on the RM12 for its power, a partnership between Saab and IAI Nammer that began with design and not actual construction. General characteristics of the engine include: Type: Afterburning turbofan Length: 4.04 meters (159 inches) Diameter: 0.889 meters (35 inches) Dry weight: Components: Compressor: Axial compressor with three fan stages and seven compressor stages Combustors: annular Turbine: One low-pressure stage and one high-pressure stage Performance: Maximum thrust: 54 kilonewtons (12,100 pounds-force) military thrust 80.5 kilonewtons (18,100 pounds-force) with afterburner Overall pressure ratio: 27.5:1 Bypass ratio: 0.31:1 Air mass flow: 68 kilograms per second Specific fuel consumption: Military thrust: 23.9 milligrams per Newton-second (0.844 pounds per pound-force hour) Full afterburner: 50.6 milligrams per Newton-second (1.79 pounds per pound-force hour) Thrust-to-weight ratio: 7.8