Blackburn Cirrus Major

Design and development

The Blackburn Cirrus Major started life as a development of the original ADC Cirrus series of aircraft engines which progressed through a number of variants, each with slightly different displacement and power outputs. The Cirrus series was later bought by Cirrus Aero-Engines (later known as the Cirrus-Hermes Engine Company) which produced the Cirrus Hermes I, II, III and IV, again each differing slightly in displacement and power.

In 1934 Cirrus was bought again by the Blackburn Aircraft company and later that year the Cirrus Minor was produced. In 1935 the Cirrus Major entered production.

Variants

Cirrus Major I

135 hp

Cirrus Major II

148 hp variant.

Cirrus Major III

Higher compression engine with an increase in output to 150 hp (116kW).

Specifications (Cirrus Major I)

Data from Lumsden

General characteristics

Type: Inline air-cooled inverted 4-cylinder

Bore: 4.72 in (120 mm)

Stroke: 5.51 in (140 mm)

Displacement: 385.64 cu in (6.31 L)

Length: 50 in (1270 mm)

Width: 17.5 in (444 mm)

Height: 30 in (762 mm)

Dry weight: 310 lb (141 kg)

Components

Valvetrain: 1 inlet and 1 exhaust valve per cylinder

Fuel system: 1 Claudel-Hobson carburettor

Fuel type: 73 octane petrol

Cooling system: Air-cooled

Performance

Power output: 135 hp (101 kW) at 2,350 rpm

Compression ratio: 5.1:1

Power-to-weight ratio: 0.43 hp/lb (0.71 kW/kg)