iverson

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The understanding I have is the weight of rounds in a given concentration (Space) over a given time. The calculation done by the daughter of one of the team deciding on what weapon and how many per aircraft. When the Hurricane and Spitfire were in development the requirement was four .303 per aircraft. Would this have meant failing the BoB? We are essentially discussing the habit of specifying equipment on the last conflict on the grounds that it was good enough then (Probably).

My point was simply that the effectiveness of a round and the likelihood of a hit were a trade-off. A metric like "weight of rounds in a given concentration (Space) over a given time" or "'weight per pound' of rounds fired in a minute" obscures this fact. There is no such thing as a "given concentration" or a "given time" outside of theory, but there are "given aircraft" available at given times whose characteristics limit the kinds of optimization that you can make--in our example, the Spitfire. Without the empirical evidence that only became available in hindsight, later in the war, the RAF's intial choice of a large number of Brownings over cannon seems perfectly sound.

When the choice between small caliber machine guns and 20-mm cannon became a practical possibility for the Spitfire, a belt-fed Hispano was not available. In fact, I believe that the Oerlikon was being considered. Either way, Hispano or Oerlikon, the gun was fed by a 60-round drum, heavy, and only one gun would fit in each wing. The cannon fired a relatively small number of projectiles at a relatively low rate of fire. While each individual projectile had a high probability of inflicting fatal damage, it also had a relatively low probability of hitting its target. So, in practice, in 1939-40, cannon had to be more accurate than machine guns. So:

* Cannon had to be more precisely manufactured in ordered to insure tighter shot groupings
* Cannon ammunition also had to more carefully manufactured and quality checked to insure consistent performance.
* Cannon had to be precisely harmonized and sighted in, which is harder with wing-mounted ordinance (hence the French preference for the moteur-canon).
* The average pilot had to be trained to shoot cannon more accurately despite greater and/or locally more concentrated recoil forces on the aircraft
* The premium on accuracy required shooting from relatively close range, negating any theoretical range advantage that heavier shells might otherwise provide.

By comparison, whatever its deficits, the 0.303-in Browning had many compensating virtues. It was belt-fed. It had a high rate of fire. This and the gun's smaller size, caliber, and weight meant that four of them could be fitted in and dispersed along each wing, complete with a fairly large quantity of ammunition. This installation fired a much larger number of projectiles, each with a low probability of effecting fatal damage from a single hit but also with a much higher probability of getting hits. So:

* Consistent gun and ammunition quality were not critical, because some dispersion actually increased the liklihood of hits by compensating for pilot or armorer errors.
* Harmonization and sighting in need not be as precise for the same reasons.
* A larger number of guns, dispersed across the wing span, and higher rates of fire for each likewise increased the likelihood of hits.
* Given the greater probability of hits and the consequent reduced demand for accurate shooting, pilot training need not be as strict or as comprehensive.

Effectively, in the late '30s, RAF planners faced a choice of solutions analogous to the choice between a rifle and a shotgun. They knew from WW1 experience that the first weeks and months of the next war would consume nearly all of the interwar RAF's small number of highly trained pilots, necessitating the rapid training of large numbers of replacements in minimum time. So they chose the shotgun.

Note doubt contemporary faith in the greater accuracy of aiming a turret independently of the aircraft was enough to justify a four-Browning armament in the Defiant but not enough to justify adoption of a single Hispano.
 

iverson

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While I find the choice of Brownings for the Defiant sensible enough, I have never understood how the RAF came to believe that a fighter could dispense with forward firing armament. WW1 experience with the F2B fighter showed that relying on the gunner in air-to-air combat invariably caused high losses. The F2B had to be flown like a fighter using the front gun, with the rear gunner merely warning the pilot and defending the rear against surprise attacks.
 

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The Defiant has always been one of my favorite WW2 misfits aircraft. it was an incredible idea that (possibly) didnt get the right company to develop it. if you look at the pictures the edges around the turret were almost air scoops. the fuselage was just slashed open to make it fit. the drag was horrible. if possibly it was like an (correct me if im wrong) F4F Wildcat? the dual LMGs back there? they folded down to make room and were in a more aerodynamic cabin. could it be possible to do something like that and still have the same quad .303 system?
 

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I think the 4*7.7 mm MG (0.303) were hopeless. But how about two 12.7 mm in the turret (like a B-17 turret) and 2*20 mm gun in the wings ? Now that would have been a decent firepower. Add a Griffon in place of the Merlin, and now we are up to something. Must be possible: see Fulmar / Firefly.
Next step is 1*20 mm in the turret, but this has already been discussed.

Yeah, I kind of like it. Firefly's Griffon, two 20 mm in the wing, two 12*7 in the turret.

I'm tempted by a line-profile, if only I can find a Firefly matching a Defiant...
 

EwenS

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The Defiant has always been one of my favorite WW2 misfits aircraft. it was an incredible idea that (possibly) didnt get the right company to develop it. if you look at the pictures the edges around the turret were almost air scoops. the fuselage was just slashed open to make it fit. the drag was horrible. if possibly it was like an (correct me if im wrong) F4F Wildcat? the dual LMGs back there? they folded down to make room and were in a more aerodynamic cabin. could it be possible to do something like that and still have the same quad .303 system?
If you think the Defiant is bad just look at what Bolton Paul did to the Skua when they turned it into the Roc for Blackburn.

Biggest problem for both to overcome is the weight of that turret.
 

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The Defiant has always been one of my favorite WW2 misfits aircraft. it was an incredible idea that (possibly) didnt get the right company to develop it. if you look at the pictures the edges around the turret were almost air scoops. the fuselage was just slashed open to make it fit. the drag was horrible. if possibly it was like an (correct me if im wrong) F4F Wildcat? the dual LMGs back there? they folded down to make room and were in a more aerodynamic cabin. could it be possible to do something like that and still have the same quad .303 system?
If you think the Defiant is bad just look at what Bolton Paul did to the Skua when they turned it into the Roc for Blackburn.

Biggest problem for both to overcome is the weight of that turret.
ok thank you for ruining my outlook on Boulton Paul...... JK
 

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The Defiant has always been one of my favorite WW2 misfits aircraft. it was an incredible idea that (possibly) didnt get the right company to develop it. if you look at the pictures the edges around the turret were almost air scoops. the fuselage was just slashed open to make it fit. the drag was horrible. if possibly it was like an (correct me if im wrong) F4F Wildcat? the dual LMGs back there? they folded down to make room and were in a more aerodynamic cabin. could it be possible to do something like that and still have the same quad .303 system?
If you think the Defiant is bad just look at what Bolton Paul did to the Skua when they turned it into the Roc for Blackburn.

Biggest problem for both to overcome is the weight of that turret.

And if you think the Roc was bad, just consider the fact they pondered about a variant with floats - just to make it even more slower, ugly, unaerodynamic, and a perfect giant training target for the LW.
This was in the days of Norway, 1940, where the Skuas already suffered against the LW.
 

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tomo pauk

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When the Defiant was designed, no one expected that German bombers could attack from French bases with fighter escorts. Bombers were supposed to take off from German bases and reach England without escort.

I always find the notion that German bombers are supposed to fly from Germany ... short-sighted from the powers that were. 20+ years before Defiant was mooted, Germans have had air bases in Belgium, for crying out loud.
Defiant was also sporting half the firepower of Hurricane or Spitfire, while being more expensive to make. Slower, with lower rate of climb - both categories required for a bomber destroyer. Ability to carry cannons was straight-forward with these two, unlike with Defiant.
 

Justo Miranda

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When the Defiant was designed, no one expected that German bombers could attack from French bases with fighter escorts. Bombers were supposed to take off from German bases and reach England without escort.

I always find the notion that German bombers are supposed to fly from Germany ... short-sighted from the powers that were. 20+ years before Defiant was mooted, Germans have had air bases in Belgium, for crying out loud.
Defiant was also sporting half the firepower of Hurricane or Spitfire, while being more expensive to make. Slower, with lower rate of climb - both categories required for a bomber destroyer. Ability to carry cannons was straight-forward with these two, unlike with Defiant.
To avoid the defensive fire of the Germans bombers the Defiant designers developed the tactic of shooting against the belly of the bombers using angled upward-firing machine guns. The idea was not new (it has been used by British fighters fighting against the Zeppelins during the World War I) but its advantage was to be able to shoot directly against the engines and wing fuel tanks that in a classical attack from behind were protected by the wing structure.

Firing from below the Defiant's four machine guns were more effective than the eight of a Hurricane firing from behind at a He 111 with 270 kg armour.
 

tomo pauk

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To avoid the defensive fire of the Germans bombers the Defiant designers developed the tactic of shooting against the belly of the bombers using angled upward-firing machine guns. The idea was not new (it has been used by British fighters fighting against the Zeppelins during the World War I) but its advantage was to be able to shoot directly against the engines and wing fuel tanks that in a classical attack from behind were protected by the wing structure.

Firing from below the Defiant's four machine guns were more effective than the eight of a Hurricane firing from behind at a He 111 with 270 kg armour.

Defiant as-is was incapable of a head-on attack - not the case with Hurricane. Hurricane can also do the angled firing in order to hit vitals of a bomber. Hurricane can also do the 'beam attack' (ie. from the side), or a diving attack either from the front or from rear.
 

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i see the Defiant being used like the Bidge Busting Jugs of the air force:
0073055-large.jpg

art by Stan Stokes.

this could have been a great job for them they were slow enough for precision bombing with rear protection (if it was developed better of course) one 500lb bomb with a good pilot could do a ton of damage and the turret could also act like a gunship. orbiting a target and raining shells/bullets on it for precision battlefield attacks
 

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