On Saturday, July 11, 2020 at 9:21:37 AM UTC+1, nightjar wrote:
On 11/07/2020 08:15, Chris Hogg wrote:
On Sat, 11 Jul 2020 08:02:32 +0100, Harry Bloomfield, Esq.
wrote:

BBC News article claiming a 13 year olds intricate calculations
persuaded them to fit 8 browning guns rather than the four planned.
Obviously chances are improved of bringing down an enemy aircraft, the
more guns are being fired, but what is the intricate calculation needed
to prove that?

It seems the guns were aimed to coincide at a range of 250 yards. 250
yards seems awfully distant to me, what they show of the films of the
time, it seems much less than 250 yards, maybe as little as 50 yards,
unless the used telephoto lens?

The convergence 'point' was actually a 12' x 8'rectangle, known as the
Dowding spread, as he believed it gave even a mediocre pilot a fair
chance of hitting the enemy. With Spitfire guns so widely spaced on the
wings, there was also quite a wide area of less concentrated fire both
before and after the convergence point. Aces would normally have the
guns set to their own personal preferences, while some Spitfire
squadrons set different convergence distances for each wing, to give a
greater depth of concentrated fire.



ISTR Douglas Bader having his convergence close in. He claimed it was the only way to shoot down the target. He was opposed to cannon for the same reason, believing it encouraged pilots to fire from too far away.