Another use for the Boulton Paul Defiant

[stona]

If the massed firepower of the bomber formations was so ineffective, the Luftwaffe sure went to a lot of trouble to develop weapons that enabled them to attack the formations while staying out of the range of that ineffective firepower.

It depends how you define effective. The armament of US bombers, even when used in mutually supporting formations, as intended, did not allow unescorted bombers to survive determined fighter attack and to pass through hostile air space with sustainable casualties. Since that was the raison d'etre for carrying all the weight of the armament, to the detriment of the bomb load, it was ineffective in its primary role.
From a German point of view it was effective enough to inflict casualties on the attacking fighters, and it was obviously in their interests to mitigate these by developing systems that would allow the fighters to attack from longer range. Few of these systems were successful and none were as effective as cannon.
It was not the bombers that defeated the Jagdwaffe, it was the US escort fighters. Without those fighters the USAAFs could never have carried their campaign to the heart of the Reich.
Cheers
Steve

 

[swampyankee]

The leadership of the RAF couldn't have predicted the quick failure of France's defense. I think the late prewar panicked re-armament both loosened up the purse strings and weakened critical faculties, but, nonetheless, it may be that the Defiant was built in large numbers less because of RAF stupidity than that Spitfire and Hurricane production was maxed out and the UK government felt keeping Boulton-Paul in the airplane business was important.


Prewar the USAAC leadership seems to have thought that bombers could a) defend themselves well enough so escorts were superfluous and b) aerial bombardment was so effective that there would not need to be enough raids to worry about attrition of the bomber force.

Then reality sunk in: premise b was invalid: bomber raids didn't terrify everybody into submission and multiple raids were needed and attrition of the bomber force was important. RAF raids didn't "always get through," but the USAAF (name change around this time) leadership seems to have felt the problem was the RAF bombers, not a flaw in premise a. How do you improve bomber defense? Add guns! Did this work? To some extent, yes, but the resulting loss in the bombers' payload/range/speed performance reduced the bombers' effectiveness faster than it decreased losses.

I suspect the most effective added armament was the tail turret, followed by the nose turret, as these would be most effective against the attacks with the greatest probability of success and have the least effect on aircraft drag. The central (ball) turret, especially, and the dorsal turret would seem to very draggy, as would the big holes for the waist gunners; these would be the most detrimental to performance.

 

[Shortround6]

Prewar the USAAC leadership seems to have thought that bombers could a) defend themselves well enough so escorts were superfluous and b) aerial bombardment was so effective that there would not need to be enough raids to worry about attrition of the bomber force.

Then reality sunk in: premise b was invalid: bomber raids didn't terrify everybody into submission and multiple raids were needed and attrition of the bomber force was important. RAF raids didn't "always get through," but the USAAF (name change around this time) leadership seems to have felt the problem was the RAF bombers, not a flaw in premise a. How do you improve bomber defense? Add guns! Did this work? To some extent, yes, but the resulting loss in the bombers' payload/range/speed performance reduced the bombers' effectiveness faster than it decreased losses.

I suspect the most effective added armament was the tail turret, followed by the nose turret, as these would be most effective against the attacks with the greatest probability of success and have the least effect on aircraft drag. The central (ball) turret, especially, and the dorsal turret would seem to very draggy, as would the big holes for the waist gunners; these would be the most detrimental to performance.

Well Pre-war there was no hope of a of a fighter with enough range to escort the bombers over the range/s the US wanted bombers to operate, ( it was technically impossible) so solutions are limited to restricting the range of the bombers to the existing (or soon to be fighters) or trying to build bombers that didn't need escorts.
A B-17C could carry 4000lbs of bombs over a 2400 mile range (not in large formations) and the likelyhood of an escort fighter capable of even doing a 1600 mile trip (using relays) in 1940 was zero.

Everybody over estimated the effects of bombing raids so small bombs and small formations were the norm.

It takes a lot longer to design and build new aircraft (and to tool up multiple factories for them) than to change tactics/techniques or realize such tactics need to be changed.

And sometimes basing your attack force on your own defense force (and vice versa) is a big mistake. American fighters during the 30s carried ONE.slow firing .50 cal and ONE .30 cal machine gun so expecting a small bomber formation armed with 5-6 .30 cal guns ( or four. 50s and several .30s ) per plane doesn't seem so unreasonable. In the Spring and early summer of 1940 German bombers carried THREE ,7.9mm machineguns but soon jumped to 5-6 per plane however many times 3 or even 4 of these guns were "manned" by one gunner so the effective firepower was nowhere near what the number of guns suggests.

 

[stona]

it may be that the Defiant was built in large numbers less because of RAF stupidity than that Spitfire and Hurricane production was maxed out and the UK government felt keeping Boulton-Paul in the airplane business was important..

Just over 1,000 Defiants were built, not all as turret fighters. Many of those built as fighters were converted to other roles (tugs, ASR aircraft, etc.) I would suggest that, in terms of WW2 production, that is not a large number.

Cheers

Steve

 

[Glider]

I have always believed that GA was a good role for the Defiant. A couple of 20's firing forwards ditch the turret and replace it with a rear gunner to save weight and that would translate into (for 1939/40) a GA aircraft with a decent low level performance, a good strike capability and a payload

 

[Shortround6]

Like many late 30s or 1940 British aircraft the last few hundred were completed on the production line as target tugs.
An admission that they were not up to combat standards yet way to much in the way of materials/parts had already been manufactured to throw in the scrap bins?
Many others were converted after being manufactured.

It might be considered demoralizing to factory workers to have production lines shut down with uncompleted aircraft on them and then weeks or months of idleness while the next aircraft to be produced is tooled up for.

 

[stona]

I have always believed that GA was a good role for the Defiant. A couple of 20's firing forwards ditch the turret and replace it with a rear gunner to save weight and that would translate into (for 1939/40) a GA aircraft with a decent low level performance, a good strike capability and a payload

Something like the Fairey Battle

Cheers

Steve

 

[Shortround6]

I have always believed that GA was a good role for the Defiant. A couple of 20's firing forwards ditch the turret and replace it with a rear gunner to save weight and that would translate into (for 1939/40) a GA aircraft with a decent low level performance, a good strike capability and a payload

Where do the 20mm guns go? The Defiant fuel tanks are in the wings outboard of the landing gear (or just about where the prop circle ends.
The basic airframe (and wing) is about the size of a Hurricane with a slightly longer fuselage. Keeping the rear gunner (even without turret) means keeping the larger fuselage, keeping 200lbs worth of gunner and flying gear (parachute) plus whatever gun/s and ammo you keep. You have only lightened the plane up by 400-600lbs at best, perhaps less before adding the 20mm guns.
Unless you swipe Merlin XX engines form the bombers (or From Hurricane IIs) you are stuck with Merlin III engines ( or Merlin VIIIs?) which means 880hp for take-off. Not the best idea for strapping 20mm guns and bombs to if you are operating from small airfields.

 

[Shortround6]

Hawker Henley. 200 produced as target tugs after being rejected as dive bomber/close support aircraft. 48ft wing span and 342 sq ft of wing. The Defiant had a 250sq ft wing.

 

[stona]

Also the first ground attack missions by any RAF aircraft occurred a bit late to save the Defiant. In the North African desert in December 1940 and January 1941, in the successful campaign against the Italians, some Hurricane pilots were ordered to attack ground targets on their return from a sortie, using any remaining ammunition. In November 1941 the obsolescent Hurricane Is of No. 80 Squadron were adapted to carry eight 40lb fragmentation bombs under wing and operated during 'Crusader'. The squadron re-equipped with IICs in January 1942 and reverted to a fighter role.

Meanwhile, in Europe, the Hurricane IIA and IIB arrived, strengthened to carry bombs and the latter equipped with 20mm cannon. Nos 1 and 3 Squadrons carried out low altitude intruder missions (Rhubarbs) across the Channel by the autumn of 1941 with their IICs. The first true fighter bomber attack in Europe was carried out by No. 607 Squadron on 30th October 1941, more than a year after the Defiant was withdrawn from front line service.

Cheers

Steve

 

[Shortround6]

I would note that the Lysander was expected to perform most of the ground attack missions or close air support that were going to be done. In France they were heavily supplemented by The Battles and Blenheims, ALL three proved grossly inadequate and only that British aircrews could die bravely while trying to support the army. In the spring/summer of 1940 there were precious few spare 20mm guns floating around for re-armament schemes. By the Spring of 1941 the gun supply was much better (although most had drums) but there was still a shortage of Merlin XX engines.

 

[Greyman]

Where do the 20mm guns go?

Where there's a will there's a way.

 

[Shortround6]

But such installations tend to kill the "decent low level performance" due to drag.

 

[Old Wizard]

 

[stona]

The top one is a Hurricane methinks.
Cheers
Steve

 

[Greyman]

The top one is a Hurricane methinks.
Cheers
Steve

Yep.

 

[Glider]

Where do the 20mm guns go? The Defiant fuel tanks are in the wings outboard of the landing gear (or just about where the prop circle ends.
The basic airframe (and wing) is about the size of a Hurricane with a slightly longer fuselage. Keeping the rear gunner (even without turret) means keeping the larger fuselage, keeping 200lbs worth of gunner and flying gear (parachute) plus whatever gun/s and ammo you keep. You have only lightened the plane up by 400-600lbs at best, perhaps less before adding the 20mm guns.
Unless you swipe Merlin XX engines form the bombers (or From Hurricane IIs) you are stuck with Merlin III engines ( or Merlin VIIIs?) which means 880hp for take-off. Not the best idea for strapping 20mm guns and bombs to if you are operating from small airfields.

There was at least one mock up of a single seat fighter built and presumably they found somewhere to put the guns so that is do able.

You do save the weight of the turret and that will be available for payload and as for the engines if the need was there then I am sure they would have been sourced from somewhere.

A close to 300mph GA aircraft with decent agility in 1940 is a lot better than most airforces could manage.

 

[stona]

A close to 300mph GA aircraft with decent agility in 1940 is a lot better than most airforces could manage.

Dowding had plans to use the Whirlwind in this role IF the Germans managed to land in Britain. Ground attack by fighters was otherwise not really something considered for fighters.
Fighter Command was established as a defensive organisation, the clue is that it succeeded ADGB which is self explanatory. Offensive aerial operations were the responsibility of Bomber Command.
In 1940 Fighter Command had little interest in ground attack and Bomber Command was established as a strategic strike force even less interested in tactical operations.
Cheers
Steve

 

[Shortround6]

There was at least one mock up of a single seat fighter built and presumably they found somewhere to put the guns so that is do able.

You do save the weight of the turret and that will be available for payload and as for the engines if the need was there then I am sure they would have been sourced from somewhere.

A close to 300mph GA aircraft with decent agility in 1940 is a lot better than most airforces could manage.

Nobody needs a 300mph GA aircraft that does the 300mph at 15-18,000ft. And that was the trouble with using Merlin III as a powerplant for a GA aircraft.

The "Mock up" was the original prototype with the turret yanked out and fared over. Kept the Merlin III engine, it was for flight trials and no armament was ever fitted. Drawings were made of several installations, some rather ambitious like tilting the guns 17 degrees for ground strafing (done by NO service aircraft in anybodies air force).

The decent agility is also suspect. An empty Defiant I weighs about what a Spitfire I or II did loaded. It went about a ton more (over 2000lbs so split the difference between between short ton and long ton) loaded or about 33% more than the Spitfire on a wing that was about 3% larger. Sorry, but yanking the turret and keeping the rear gunner (even with a Vickers K gun) doesn't lighten the plane up enough.

If you have enough Merlin XX engines for this project stick them in Spitfires.

Please note that the Hotspur and the Fairey P.34/4

Predecessor to the Fulmar were both GA aircraft with 500lb bombloads and only single forward firing gun.

 

[Greyman]

The decent agility is also suspect.

Depends what is meant by 'agility', but for what it's worth, a bit from AFDU Tactical Trials with the Defiant:

Defiant v. Spitfire

After some preliminary practice engagements, the Defiant was placed on a patrol line and a Spitfire instructed to attack when he desired. The full initiative in the attack was therefore given to the Spitfire.

As the Spitfire approached, the air gunner of the Defiant was able to open fire. The Defiant then went into a steep turn and was followed by the Spitfire. The engagement lasted about 10 minutes and the air gunner after the first five minutes had used up all his film. During the whole engagement the Spitfire was unable to bring his guns to bear and finally landed having failed to use his cine gun.

The following notes upon his manoeuvres were given by the Defiant pilot:-

(i) it is imperative to turn at an air speed of at least 160 m.p.h., because in a vertical turn the aircraft stalls at a much greater speed than when flying straight.

(ii) By losing height slowly, it is possible to maintain a Rate 4 turn and keep up the speed. At one time of the encounter the Defiant was on the tail of the Spitfire but below it.

(iii) At no time did 'G' affect the pilot or air gunner.

(iv) There is plenty of warning before the stall, which is gentle.​