Beaufighter question

[John Beaman]

In the recent book by Osprey on Beaufighter Aces, it was mentioned that the IIF, with the Merlin engines, had a "significant" drop off in performance and handling compared with the Hercules-engined IF. What was the reason for this "drop-off" and why change to the Merlin? ...a shortage of Hurcules engines because the Halifax production had priority?

Thanks

John

[Graham Boak]

I think I can answer one of the three: the Merlin engines have additional side area forward of the c.g, which is destabilising. The propellers are further forward, also destabilising. Hence the poorer handling. This was largely restored by adding dihedral to the tailplane, thus providing additional side area aft.

For the second: I suspect that the Merlin XXs were simply less powerful than the Hercules, at least at lower level. At higher altitude they would be superior, but the German bombers of the period would be below the optimum altitude for the Merlin XX.

For the third: this may be because the Hercules was delayed in production because of problems with the sleeve valves. Alternatively, (or additionally), it was considered useful to have alternative sources of production in case of supplies of one engine being cut by German bombing. I don't know which was considered the most important.

[Franek Grabowski]

There was another factor as well. At the time a new production run was started at a new factory (forget the name) and quantities of power eggs became available, however initially they suferred from a very bad quality. I think the same problem appeared with Wellingtons at the time.

[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".

[Graham Boak]

I hadn't seen that about the larger fin and rudder before - was this fitted to all subsequent Beaufighters or is it a distinguishing feature of the Mk.II?

[Jim Oxley]

The larger fin and rudder became standard for all subsequent models.

[John Beaman]

Good information.

[John Beaman]

Good information. I

[John Beaman]

Good information. I was

[John Beaman]

Good information. I was not