160 horsepower free shaft turbine engine  

Boeing 502-6 Turboshaft

The Boeing 502-6 is a simple, free shaft turbine engine, which was actually designed in the 1950's. The engine is quite bulky, quite heavy, and not very powerful for its size. Superficially, it is similar in dimensions to the T63-A700 engine in the turbine boat, although it weighs 60 lbs. more and produces half the horsepower. The engine also burns more fuel per hour than the T63.

The intended usage for the Boeing 502-6 is to provide electrical power for a United States Navy minesweeping ship. The engine is mounted in pairs to a combining gearbox, which turns an electric generator that creates a current in a mine sweeping device that sets off unexploded mines.

Various versions of the 502 were developed for a number of purposes. The engine was initially derived from the Model 500, a simple cycle turbojet with 180 lbs. of thrust. The 502 also saw experimental use as an auxiliary power unit, a turboprop engine, an engine for a road car, a truck, and even a race car. Other versions made it into a military truck, a tank, a locomotive, a tractor, and a firetruck.

The 502-6 is similar in general layout to the JFS-100. Located in the front of the engine is a single stage compressor, with a 3.5:1 compression ratio, a 3.5 lb/sec air mass flow, and a peak speed of 36,500 rpm. The compressor feeds two through flow can combustors, each with a single fuel nozzle. Combustion gas travels through a transfer tube where it connects to the nozzle box. After passing through the high pressure nozzle, the gas is expanded through a single stage axial gasifier turbine, which drives the compressor and the accessory gear train.

Combustion gas continues through the wastegate section, which bypasses excess gas pressure around the power turbine to maintain governed rpm. The power turbine is single stage axial, and rotates at a maximum speed of 23,725 rpm. The power turbine drives an output reduction gearbox at the rear of the engine, which turns the output shaft at 2,750 rpm, and produces 160 shaft horsepower. The exhaust is collected in a scroll type diffuser, with a single outlet facing upwards.

Like the JFS-100, the power section of this engine can be removed, eliminating some weight and leaving the gasifier section. With the proper sized jet pipe, the engine is said to be able to produce around 140 lbs. of thrust.


Boeing 502-6 Gas Turbine Shaft Engine

  • Type: Dual spool, free shaft turbine
  • Inlet: Axial
  • Compressor: Single stage centrifugal
  • Burner: dual can combustor
  • Turbine: Dual spool, single stage axial gas producer turbine, single stage power turbine
  • Exhaust: upward facing, single exit scroll diffuser
  • Power Rating: 160 shaft horsepower at 2,750 rpm
  • Peak Torque Output: 550 lb/ft at stall rpm
  • Weight: 200 lbs.
  • Power/weight: .8:1
  • Air mass flow: 3.5 lbs/sec
  • Compression Ratio: 3.5:1 at 36,500 rpm
  • Maximum TIT: 1250 degrees F
  • Specific Fuel Consumption: 1.5 lb/shp/hr


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