Graham:
If I overrate the MS 406, then you too overrate the D.520. Back in 1978, the belgian researcher Gaston Botquin sent to the Air International his figures for how many enemy planes were claimed, (confirmed and probable) for each french fighter pilot killed. I calculated the same statistic for the british Hurricane force from Brian Cullīs et.al. Twelwe Days in May. The figures are as follows.
MS 406 = 1:2.5
MB 151/2 = 1:2.9
H75A = 1:6.2
D.520 = 1:7.7
Hurricane = 1:11.1
The Hurricane is much superior to the D.520. Also, if you look at the Campaign in Syria in 1941, where the best French outfit faced fairly ordinary Hurricane outfits, the Hurricane still comes out on top. Ditto Operation Torch. Small samples to generalize, but...
One shortcoming of the MS 406 was that it rarely performed up to itīs advertized performance. (As is confirmed by Finnish performance tests). The HS 12Y-31 engine wore out quickly, and also lost power with altitude quickly. (Similar to the Allison V-1710.) It was only with the addition of the Szydlowski-Planion supercharger that this defect is alleviated. The MS 405 was of the same technical generation as the Hurricane. With comparable engine (MS 411) the aircraft should have performed similarly. The MS 406 had superior armament, (the motorcannon). The two/four wing-mounted machine guns were largely useless.
That brings up a different issue, which is more pertinent to the main theme of this thread. It is well known how the allies "lost" the opportunity to get their hands on the direct injection system before the war. But why didnīt they copy the strong points of the DB-601 series, as soon as war broke out. The Bosch injection system, and the supercharger gearing system. Both features kept the DB engines competitive for most of the war. Surely not Patent rights
