The Fiat 4700 was an Italian turbo-generator developed by Fiat Aviazione under contract to the Italian Defence Ministry and used to power the experimental Fiat 7002 tip jet helicopter.^[1]

Design and development

The Fiat 4700 was developed to provide power in cold-jet driven helicopters.^[1] The 4700 was a turbo-driven air compressor driven by the primary engine, a turbojet engine based on the Fiat 4002.^[1] The compressor and primary engine are mechanically independent.^[1] The engine is mounted vertically to reduce the length of the compressed-air ducts to the rotor.^[1] The engine was used on the Fiat 7002 helicopter which first flew on 26 January 1961 where the Fiat 4700 was used to power the cold tip-jets on the two-blade rotor.^[2]

Applications

• Fiat 7002^[2]

Specification

Data from Jane's All the World's Aircraft 1962-63.^[3]

General characteristics

• Type: Gas generator
• Length: 1,300 mm (51.2 in) (height)
• Diameter: 612 mm (24.1 in)
• Dry weight: 152 kg (335 lb)

Components

• Compressor: Single-sided centrifugal flow plus gas generator single-sided centrifugal flow compressor driven by the free power turbine
• Combustors: Annular with 16 burners
• Turbine: 1-stage axial flow (gas turbine power) + 1-stage axial flow free power turbine (gas generator power)
• Fuel type: Aviation kerosene
• Oil system: Re-circulating pressure system with one pressure pump and three scavenge pumps

Performance

• Maximum power output: 450 kW (610 hp) (gas hp for take-off), 377 kW (505 hp) (ghp max continuous)
• Overall pressure ratio: 4:1
• Air mass flow: 5.1 kg/s (11.2 lb/s) at 25,000 rpm at sea level, 3.34 kg/s (7.36 lb/s) (max continuous)
• Specific fuel consumption: 0.758 kg/kWh (1.246 lb/(hp⋅h))
• Power-to-weight ratio: 2.99 kW/kg (1.82 hp/lb)