The Volvo Flygmotor RM6C was a turbojet engine developed from the British Rolls Royce Avon 300 machine. It was built in Sweden in large numbers, under license, to power the Saab J35 Draken combat aircraft. It was a powerful and reliable engine, capable of delivering 17,700 pounds of thrust, enabling the aircraft to fly at Mach 2 (1,350 miles). It was fitted with a Swedish-designed Model 67 afterburner.
Technical Description
The intake of the Volvo Flygmotor RM6C was made of a magnesium annular casing, with variable incidence inlet guide vanes, which were hydraulically-actuated. The engine compressor was a 16-stage axial unit, with rotor blades pinned to the rotor discs, which, in turn, were splined to a shaft. Both the stator and rotor blades were of aluminum alloys. The compressor shaft was both roller and ball-bearing mounted. The front compressor casing was cast magnesium alloy, and it carried the stage 0 to 6 stators. The intermediate casing was cast in aluminum alloy, and carried the stage 7 through 9 stators, while the fabricated steel outlet carried the stage 10 through 15 stators.
The turbine of the Volvo Flygmotor RM6C was a two-stage design, with the turbine shaft being coupled to the compressor shaft. High-pressure and low-pressure blades were both of Nimonic alloys. All turbine blades were shrouded at their tips. The combustion chamber was of the annular type, which was fitted with eight flame tubes and duplex burner. There were interconnecting pipes between each pair of flame tubes. The nozzle casing, of cast chrome steel, had two rows of guide vanes, with one being mounted ahead of each turbine stage.
The accessory drives for the lubrication, fuel pumps, and electrical power equipment consisted of two horizontal power take-off shafts, with one on each side of the engine. They were driven by gearing on the main shaft, just aft of the center bearing assembly. The lubrication system, with its four scavenge pumps, was of the closed circuit type, with lubrication being provided for the three main bearings, the starter reduction gear, and the ancillary drive system.
The Volvo Flygmotor RM6C was started by a Plessy iso-propylnitrate fluid starter, which was mounted in the intake bullet. The starter fluid tank had a capacity for three starts. It was integrated with an automatic high-energy ignition system. A related torch ignition system for the afterburner was also automatically controlled. The afterburner had infinitely variable flap-type nozzle driven by screw-jacks. It had V-type flame holders with fuel injection manifold located at the front of the V.
Below, a photograph of the Volvo Flygmotor RM6C turbojet engine taken out the aircraft fuselage rear section. It was unusual in having an extended exhaust and an angled afterburner.
Cutaway drawing the RM6C
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