Castor
Walter Castor III
Type	Radial aero engine
National origin	Czechoslovakia
Manufacturer	Walter Aircraft Engines
First run	1929

The Walter Castor was a Czechoslovakian seven-cylinder, air-cooled radial engine for powering aircraft that was developed in the late 1920s. The Super Castor was a nine-cylinder development.^[1] Castor I production began in 1928, Castor II in 1932 and the Castor III in 1934.

Applications

• Aero A.35
• Aero A.304 (Super Castor)
• Airspeed Envoy
• Breda Ba.25
• Dornier Do K
• Fizir F1V
• Hopfner HV-6/28
• Letov Š-28
• Rogozarski AZR
• Savoia-Marchetti S.71

Engines on display

A preserved example of the Walter Castor engine is on display at the following museum:

• Prague Aviation Museum, Kbely

Specifications (Castor I)

Data from Flight.,^[2] L'Air 1 December 1929: Les Moteurs Walter^[3]

General characteristics

• Type: 7-cylinder radial piston engine
• Bore: 135 mm (5.31 in)
• Stroke: 170 mm (6.69 in)
• Displacement: 17.033 L (1,039.4 cu in)
• Dry weight: 248 kg (547 lb)

Components

• Valvetrain: One intake and one exhaust valve per cylinder
• Fuel system: Zenith carburettor
• Fuel type: 50% Petrol, 50% Benzol
• Cooling system: Air-cooled

Performance

• Power output: 180 kW (240 hp) at 1,750 rpm normal
• Compression ratio: 6:1
• Specific fuel consumption: 0.302 kg/kWh (0.496 lb/(hp⋅h)) at 0.8 - 0.81 specific gravity
• Oil consumption: 0.027 kg/kWh (0.044 lb/(hp⋅h))
• Power-to-weight ratio: 0.78 kW/kg (0.48 hp/lb)