"Handley Page Halifax Mk II Series 1 of No. 1658 Heavy Conversion Unit based at Riccall, Yorkshire, being test-flown on the starboard inner engine only by Squadron Leader P Dobson in order to determine the height loss for emergency flights on one engine, July 1943." Halifax B Mark II Series 1, R9430 19, of No. 1658 Heavy Conversion Unit based at Riccall, Yorkshire, being test-flown on the starboard inner engine only by Squadron Leader P Dobson in order to determine the height loss for emergency flights on one engine.