One major problem with the design of the Hawker Tempest and Typhoon aircraft was that they had a large ‘chin’ radiator. If another aircraft got into trouble it could belly flop land, in a field for example, and slide along the ground to a standstill. The chin radiator fitted to Napier Sabre powered aircraft meant that any such landing was much more risky because it would make contact with the ground first, dig in and flip the aircraft over.
Napiers spent a great deal of time researching and developing a range of solutions. The requirement was to allow sufficient airflow across the radiator with adjustment to correctly regulate the cooling. This increased as the engine Series was developed and required extra cooling.
The solution was to create an annular radiator allowing air to pass through the spinner of the aircraft. As can be seen in the images several types of annular radiator were tested and developed. In reality very few Sabre engined aircraft actually received this modification die to the war ending. The unique Vickers Warwick HG248 was the only twin engined Sabre aircraft and it had annular radiators.