1937-45: Doubling down on the 2-engined 'day fighters' (3 Viewers)

[ThomasP]

The 37mm M4 and M10 could both use articulated metal link belt feed. The first production P-39Ds were fitted with the belt feed, but production was quickly switched to the magazine type endless belt feed. The articulated metal belt feed arrangement only allowed 15 rounds of 37mm. The Russians received a bunch of the aircraft with the belt feed in their first Lend-Lease shipments. The image below is from the Mar'42 edition of the TM.

 

[yulzari]

The Whirlwind had terrible range for a twin. Move the radiators and fill the void with fuel. But the new rads will add to drag and speed loss.

Indeed squeezing in more fuel and/or drop tanks for escort work would be a benefit but the Whirlwind was not intended for that. It was a home defence bomber destroyer to operate from British and French bases intercepting German bombers. Range was not a critical part of the task. Similarly in single engines types the Spitfire and Me109 had limited ranges because they were for the same short range interceptor or tactical escort roles.

We can see the uncertainly of the best way to do it at the time as the RAF employed three options. The multi rifle calibre single seaters, turret fighter and four cannon twin. What the twin brought was the same power as later developed single engine fighters but much earlier by using the leverage of mounting existing engines not relying upon new types or later developments. Essentially you can get a quasi Tempest two years early. It is not what you can make but what you can bring to the battle today.

First define the task then examine the means available to meet it. For the same four 20mm gun armament the Beaufighter was intended for tasks needing endurance hence had a longer range. Equally hence, was larger and heavier.

Whirlwind tests showed that a beard radiator on the engines gave much the same drag as the standard wing radiators so the inner wing could have been freed up for more fuel. All part of the differences that would have led to a more capable MkII which would better meet the post BoB tasks.