The design started as an experimental pure-turbojet known as the ASX, which commenced testing in 1943. By this point other engine designs were already entering pre-production, and it seemed there was little need for the ASX in its existing form. The design was then modified into the turboprop layout with the addition of a second turbine stage, which was geared to the propeller and was named ASP at that stage.
Early flight-testing of the Python was carried out using the Lancaster B.1 (FE) TW911 and the Lincoln B.2 RE339/G, each aircraft having the two outboard Rolls-Royce Merlins replaced by Pythons. Lincoln B.2 RF403 also had two Pythons similarly installed and was used for high-altitude bombing trials at Woomera, South Australia, the Pythons being used to increase the height from which tests could be carried out. These trials were principally of the ballistic casings for the Blue Danube atomic weapon, there being at the time no other suitable aircraft available that could accommodate the large weapon casing measuring 62 inches diameter x 24 feet (7.3 m) in length, and carry it to the height required. Maximum release height and speed for the first eleven tests was 275 mph and 34,783 ft (10,602 m) with a bombing error of 61 ft.
Avro Lancaster - (test only)
Avro Lincoln - (test only)
Length: 123.2 in (3129 mm)
Diameter: 54 in (1372 mm)
Dry weight: 3,450 lb (1565 kg)
Compressor: 14 stage axial
Combustors: 11 combustion chambers
Turbine: Two-stage turbine
Maximum power output: 4,110 ehp (3,065 kW), sea level at 8,000 rpm including 1,180 lbf (535 kgf) exhaust thrust
Overall pressure ratio: 5.35:1
Specific fuel consumption: 0.805 lb/hr/eshp
Power-to-weight ratio: 1.2:1