[Jim Oxley]

Just to elaborate on the above.Bristol proposed a Beaufighter powered by Rolls-Royce Merlin XX liquid cooled engines to the Air Ministry in March 1939 while production plans were being drawn up. It was as a hedge against shortages of the Hercules powerplants, which were experiencing production problems at that time.In total 450 Merlin powered Beaufighter Mk.IIF's were built, as opposed to 910 Hercules powered Beaufighter Mk. I's.The prototype Beaufighter Mk.II first flew in July 1940. The first production Beaufighter Mk.II's took to the air in March 1941. The Merlin XX engines were rated at 1,280hp for take-off and 1,260hp at 11,000ft. Due to the reduced drag afforded by the Merlins and their slimmer nacelles, the Beaufighter Mk. II was seven mph faster than the Mk. I at 15,650ft, but climb was slightly down, by three mph. In addition directional stability was worse - and the Mk.I wasn't great to start with. To solve the problem the Mk.II's were fitted with a taller fin and rudder designed to compensate for the extra side area of the Merlins nacelles, which accentuatede the problem. Later production Mk.II's also incorporated 12 degree's of diherdral in the horizontal tail planes.Above information drawn from Stewart Wilson's book "Beaufort, Beaufighter and Mosquito in Australian Service".