[4] The combustion chamber was connected to the compressor outlet by a very large single spiral duct giving the engine an asymmetrical appearance.
Whittle designed the centrifugal compressor to develop about 4:1 pressure ratio when, as far as he was aware, the best previously demonstrated performance in a single stage was about 2.5:1.
One disadvantage of a double-sided impeller is the requirement, in an aircraft installation, for an intake with a plenum with its higher pressure losses.
Some heat exchange was expected from the exhaust pipes to the ten ducts delivering air to the combustion chamber as they were all enclosed by the outer casing.
[2] Testing began with a reconstructed engine at the premises of the BTH's redundant Ladywood foundry at nearby Lutterworth in Leicestershire on 16 April 1938 and continued until the turbine was damaged on 6 May 1938.
Poor fuel system and combustion performance no longer limited the testing of other parts of the engine.
[2] The team demonstrated that the turbojet had the potential to compete with the large reciprocating aero-engines then being mass-produced for the UK Re-armament Programme.
The initial rounded "bulb" de Laval-type turbine blade root fixing was later replaced with a new triangular "fir-tree" design after repeated stress/fatigue failures of the earlier type.
The reverse-flow arrangement had no thermal expansion problems, it allowed the continued use of a very short shaft between the impeller and turbine, the end covers at the rear of the chambers could be easily removed for inspection and modifications to the combustor components.