Boulton Paul Defiant

An interesting idea, it probably could have been done but it would have been a less than perfect aircraft. Much better that the type was used as a night-fighter once the German's switched to night-bombing from late August 1940; some aircraft being fitted with AI MkIV radar.

Overall though, if the Boulton Paul Wolverhampton factory had been used for Spitfire production instead of Defiant's it would have given Britain three active Spitfire lines (Supermarine and Woolston/Itchen/Eastleigh and Nuffield at Castle Bromwich as well as BP) at the outbreak of war which would have made Westland the fourth line when it came on line in 1940/41.
 
GTX said:
Tzoli said:
I always wondered why does the Defiant not have any regular forward firing guns? Like on the nose or on the wings, there were plenty of space for it!
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Covered on the first page of this thread.
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No.
I meant Turret AND MG's on the wings!


so it's like 8x 7.7mm (4 on wings, 4 in the turret)
or 4x 7,7mm in the turret and 4x 12.7mm in the wings
or a late production variant with 4x 12.7mm turret guns and 4x 20mm Hispano Guns on the wings
 
Tzoli said:
GTX said:
Tzoli said:
I always wondered why does the Defiant not have any regular forward firing guns? Like on the nose or on the wings, there were plenty of space for it!
Click to expand...


Covered on the first page of this thread.
Click to expand...

No.
I meant Turret AND MG's on the wings!


so it's like 8x 7.7mm (4 on wings, 4 in the turret)
or 4x 7,7mm in the turret and 4x 12.7mm in the wings
or a late production variant with 4x 12.7mm turret guns and 4x 20mm Hispano Guns on the wings
Click to expand...


Once again - Covered on the first page of this thread. Reply#2 to be specific!
 
JFC Fuller said:
An interesting idea, it probably could have been done but it would have been a less than perfect aircraft. Much better that the type was used as a night-fighter once the German's switched to night-bombing from late August 1940; some aircraft being fitted with AI MkIV radar.
Click to expand...

For that role, it would have been better to remove the turret (while keeping the second crewman in an extended cockpit as a radar operator) and use the weight saved to mount a couple of Hispanos in the wings and a quartet of .303s behind the cockpit, fixed to fire upwards at a steep angle. Overall there should still be some weight saving and the aerodynamics would be cleaner, improving performance.

This type of upward-firing gun installation became very successful for Luftwaffe night fighters later on (their name for it being Schräge Musik) and was also used by Japan, but in fact the RAF were well aware of the possibilities before that, having tested planes with upward-firing guns specifically for night fighting.
 
JFC Fuller said:
Introducing it into the production line is interesting but there seem to be better solutions available, like the Beaufighter.
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No question - but as this thread is about the Defiant, including what might have been done to make it more useful and effective, that's what I was focusing on.
 
I keep wondering...
Say, take a Mk II Defiant, without the turret and with a rear cockpit kind of like the TT marks, albeit with a little more glazing plus provision to mount 1-2 VGO or Browning guns, add 8-12x0.303"/4x0.50"/2x20mm + 4x0.303"/2x20mm + 2x0.50"/4x20mm forward-firing guns, folding wings and a tail hook. How do you think the Sea Defiant described above would compare to a Fulmar or even an early Firefly, especially if re-engined progressively with 45 and 60 series Merlins? Personally, I think it would be faster but most likely somewhat shorter ranged.
 
It seems self evident that aircraft turrets held false promise, & did not allow 'self-defending' bombers
( extreme case - YB-40) to function viably in the face of determined fighter attack.

Like-wise, the turret interceptor ( Defiant) was a dead end, being too heavy, slow, & lightly armed.

The B.o.B. showed that only the 8 gun (& cannon were better yet) high power-to-weight single engined fighters were really viable ( Bf 110 & W. Whirlwind also failed to impress), if fighter opposition was about.

& it was not turret equipped fighters that decimated USAAF bombers by day/RAF bombers by night
over Germany.

Even arch-pragmatist Curtiss Le May found though his B-29 had 'state-of-the-art' turrets - they were in fact counter-productive, & deleted them for maximum bomb-truck functionality.

Operations showed that studding B-25 & B-26 medium bombers with turrets only served to reduce
their bomb-truck & speed/range capabilities but did not make them self-defending..

B-25/26 empty/loaded weights, bomb/fuel loads & cruise/max speed compare poorly with the similar sized, but lightly defensively armed Do 217, - making the cost of the turrets clear..

& don't mention Mosquito, - how many lives were needlessly lost in slow, lumbering turret bombers..
 
If you look up 'no deflection aiming' you can why the Defiant pilot had a facility to fire the turret guns.

With them locked forwards, angled above the propellor disk, and a suitable gun sight he would have been able to fire them at targets in front of him. However, the concept got lost along the way so the pilots never had the sight nor training or even knowledge of the idea for this but the Defiant, as made, did have 4x.303" fixed firing guns had the concept been followed through and at next to no added weight (ie a couple of kilos extra for the sight).
 
That would have been a system similar to the later German "schräge Musik" installations,
which required the fighter to fly more or less with the same speed, as the target, below
and behind. The gunner could have compensated for the differences in speed, but fixed
and triggered by the pilot, I don't think, that it would have been effective against enemy
fighter aircraft.
(drawing used from http://www.aviastar.org/pictures/england/boulton_defiant.gif )
 

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I have often thought that the Defiant could have made a great two-seat attack aircraft. Go with a lighter and more damage-resistant radial engine installation, faired fixed landing gear, use the weight and volume saved for a pair of 20mm cannon, ammo, fuel and armor and strap on a couple of 250 lb bombs or a rack of 60 lb rockets. You'd have a fighter bomber comparable to the successful Hurribombers with good defensive armament and it wouldn't have taken long for crews to discover that a couple of Defiants orbiting a ground target and pouring down fire from eight .303 Brownings could be very effective.
 
You'd still have the four-gun, power-operated turret and much heavier construction than the Japanese design so I am not sure the Val is a valid comparison. A faster and more heavily armed and armored Blackburn Roc might be a better description. The Miles M.20 showed that there is very little speed penalty to fixed landing gear up to about 300 mph anyway.
 
Resurrecting an oldish thread to pose a related question: Might Defiants have been useful as mixed squadrons/flights to act as wingmen for Hurricanes?

Idle musing but wondering whether having a turret armed fighter like the Defiant might have been useful to provide rearward vision and covering guns while the Hurricanes went on the offense
 
lostcosmonauts said:
Idle musing but wondering whether having a turret armed fighter like the Defiant might have been useful to provide rearward vision and covering guns while the Hurricanes went on the offense
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Possibly. One issue is the 20 mph speed difference between the two types. Perhaps a more compact, 2-gun turret to get the Defiant's speed up to par?
 
Archibald said:
I wonder, could a belt fed single HS-404 fit inside the turret ? now that would justify its presence better than 4 0.303...
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Well yes, a Hispano-armed Defiant was tested by the A&AEE at Boscombe Down, using the first prototype (K8310) with a single HS-404 in a standard turret. Fitted with the cannon, that Boulton Paul 'A' turret became an 'F'.

Belt-feed is another matter. Hispano-Suiza's work on belt-feeding ended with the German occupation. And Martin-Baker didn't design a British equivalent until 1941 (Hispano Mk.II).
 

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Coooool ! I KNEW it was feasible. Except the drum was a nightmare: only 60 shells and a weight of 25 kg (screw imperial units). French gunners onboard LeO-451 had very hard times reloading... in a cramped Defiant it would probably be even worse.

Say what you want, but a Defiant with one 20 mm in the turret and two under or inside the wings would have some very respectable firepower. In a sense, even a lone 20 mm gun would make the Defiant (and its turret) worthwile. Because the gun at least had explosive shells, not tiny chards of metal like the 0.303.
 
Archibald said:
Coooool ! I KNEW it was feasible. Except the drum was a nightmare: only 60 shells and a weight of 25 kg (screw imperial units). French gunners onboard LeO-451 had very hard times reloading... in a cramped Defiant it would probably be even worse.
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That was pretty much the same in the first Bristol Beaufighter night fighters for the radar operator, he had to go forward and change the magazines on 'four' Hispanos, all the time the pilot was trying to stay in visual contact with the target and weaving all over the place. The book called 'Night Fighter' about Cunningham' and Rawnsley' exploits describes it very well ---
 
Archibald said:
I wonder, could a belt fed single HS-404 fit inside the turret ? now that would justify its presence better than 4 0.303...
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I would have needed a larger and heavier turret with increase in drag and decrease in speed.
 

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lostcosmonauts said:
...

Idle musing but wondering whether having a turret armed fighter like the Defiant might have been useful to provide rearward vision and covering guns while the Hurricanes went on the offense
Click to expand...
Have to look up, where I read this many years ago, but it is said, that such mixed formations actually were used.
They lured the German fighter pilots into attacks from the rear and above against the seemingly unalerted and
helpless Hurricanes. This tactic was said to have been successful for a while, until the Germans were forewarned.
 
Archibald said:
Justo Miranda said:
In my opinion a single seat Defiant fitted with a large fuel tank at the turret site could have escorted the Short Stirling heavy bombers to Berlin in 1940.
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Brilliant !
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Sorry to rain on your parade but the first production Stirling didn’t fly until July 1940 and the first squadron, number 7, wasn’t ready until Jan 1941, flying its first sorties in Feb. The second squadron only began to get them in April and the third in Nov.
 
No problem really, swap the Stirlings for Hampdens or Wellingtons.
 
I was sure I’d read about the mix up between Hurricanes and Defiants as well but thought that had been all Defiant squadrons. Kind of what had got me thinking along this line
 
Main problem was that the germans learned fast ! Too fast... smart idea nonetheless.
 
EwenS said:
Archibald said:
Justo Miranda said:
In my opinion a single seat Defiant fitted with a large fuel tank at the turret site could have escorted the Short Stirling heavy bombers to Berlin in 1940.
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Brilliant !
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Sorry to rain on your parade but the first production Stirling didn’t fly until July 1940 and the first squadron, number 7, wasn’t ready until Jan 1941, flying its first sorties in Feb. The second squadron only began to get them in April and the third in Nov.
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OK, in 1941:confused:
 
Archibald said:
Coooool ! I KNEW it was feasible. Except the drum was a nightmare: only 60 shells and a weight of 25 kg (screw imperial units). French gunners onboard LeO-451 had very hard times reloading... in a cramped Defiant it would probably be even worse.

Say what you want, but a Defiant with one 20 mm in the turret and two under or inside the wings would have some very respectable firepower. In a sense, even a lone 20 mm gun would make the Defiant (and its turret) worthwile. Because the gun at least had explosive shells, not tiny chards of metal like the 0.303.
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As it happened, though, a Spitfire with two 20-mm in the wings or a Hurricane with four provided the heavier firepower without the weight, complexity, and performance penalty of the turret and its gunner.
 
Apophenia said:
Archibald said:
I wonder, could a belt fed single HS-404 fit inside the turret ? now that would justify its presence better than 4 0.303...
Click to expand...

Well yes, a Hispano-armed Defiant was tested by the A&AEE at Boscombe Down, using the first prototype (K8310) with a single HS-404 in a standard turret. Fitted with the cannon, that Boulton Paul 'A' turret became an 'F'.

Belt-feed is another matter. Hispano-Suiza's work on belt-feeding ended with the German occupation. And Martin-Baker didn't design a British equivalent until 1941 (Hispano Mk.II).
Click to expand...

I believe that belt-feed work in France did not end with the invasion of France or restart with Martin-Baker in England. Chatellerault developed the first belt-feed system for the Hispano and sent the result to Britain in 1939 or '40. Molins then developed the design for operational use in Britain. Martin-Baker developed a later feed system. I have no idea when belt feed first became available in the UK, though.

I can't recall where I first read this. But a quick google found the following:

Hispano 20mm Cannon - Incorrect Reference to Use of Martin Baker Feed Mechanism

There are ongoing incorrect and multiple source references to the belt feed mechanism that was designed and manufactured for the Hispano 20mm cannon. The Hispano cannon became a true superior weapon when the French designed Chatellerault feed mechanism was adopted to replace the 60 round...
ww2aircraft.net ww2aircraft.net

 
Jemiba said:
lostcosmonauts said:
...

Idle musing but wondering whether having a turret armed fighter like the Defiant might have been useful to provide rearward vision and covering guns while the Hurricanes went on the offense
Click to expand...
Have to look up, where I read this many years ago, but it is said, that such mixed formations actually were used.
They lured the German fighter pilots into attacks from the rear and above against the seemingly unalerted and
helpless Hurricanes. This tactic was said to have been successful for a while, until the Germans were forewarned.
Click to expand...
I've heard this too. But I suspect that it is no more than a war story. At least some attacking fighters would probably be shot down by rear gunners during any large fight. But I can't see how the allegedly surprising presence of a turret and gunner in the Defiants could turn the accompanying performance deficits into even a momentary advantage. I suspect that, during an attack by Bf109s, correctly and incorrectly identified Defiants would be shot down at about the same rate.
 
Archibald said:
Coooool ! I KNEW it was feasible. Except the drum was a nightmare: only 60 shells and a weight of 25 kg (screw imperial units). French gunners onboard LeO-451 had very hard times reloading... in a cramped Defiant it would probably be even worse. ...
Click to expand...
Good point!
The Defiant turret was so cramped that George Quilter (G.Q. Parachutes or G.Q. Security) had to invent a slender new type of parachute container: the Para-Jerkin (aka. Dumbo Suit). The Para-Jerkin was essentially a long vest with the parachute canopy spread wide across the back. It had the first pilot-chute (aka. extractor) with a spiral spring and was closed by soft through-loops (as seen on all modern emergency parachutes).
All other British Bomber Command turret gunners only wore parachute harnesses while inside their turrets. If the bomber was damaged, they had to crawl out of their turret - into the fuselage - find their chest-type parachute - clip it on and dive out the escape hatch. Is it any wonder that Lancaster crews suffered such heavy losses?
Rob Warner FAA Master Parachute Rigger with back, seat and chest ratings. I have also lectured on packing lap-type parachutes at Parachute Industry Association Symposiums.
 
iverson said:
Apophenia said:
Archibald said:
I wonder, could a belt fed single HS-404 fit inside the turret ? now that would justify its presence better than 4 0.303...
Click to expand...

Well yes, a Hispano-armed Defiant was tested by the A&AEE at Boscombe Down, using the first prototype (K8310) with a single HS-404 in a standard turret. Fitted with the cannon, that Boulton Paul 'A' turret became an 'F'.

Belt-feed is another matter. Hispano-Suiza's work on belt-feeding ended with the German occupation. And Martin-Baker didn't design a British equivalent until 1941 (Hispano Mk.II).
Click to expand...

I believe that belt-feed work in France did not end with the invasion of France or restart with Martin-Baker in England. Chatellerault developed the first belt-feed system for the Hispano and sent the result to Britain in 1939 or '40. Molins then developed the design for operational use in Britain. Martin-Baker developed a later feed system. I have no idea when belt feed first became available in the UK, though.

I can't recall where I first read this. But a quick google found the following:

Hispano 20mm Cannon - Incorrect Reference to Use of Martin Baker Feed Mechanism

There are ongoing incorrect and multiple source references to the belt feed mechanism that was designed and manufactured for the Hispano 20mm cannon. The Hispano cannon became a true superior weapon when the French designed Chatellerault feed mechanism was adopted to replace the 60 round...
ww2aircraft.net ww2aircraft.net

Click to expand...
Hispano-Suiza originally designed smaller-capacity magazines than the 60-round drum, specifically for flexibly-mounted guns, but I don't believe that any of these entered service.
 
60 rounds was already not enough shells, yet too heavy. Less shells helps the weight issue (thank you, Captain Obvious !) but of course cut into the firing rates even more.
The only solution was the British one: belt-fed. More shells, less weight, faster firepower.
 
It was not quite that simple: if bombers came under attack, a fighter would typically do a "firing pass" of fairly brief duration. A magazine capacity of 20 rounds would allow the gunner two seconds of firing, which in many instances would be enough to engage a fighter - hopefully allowing time to switch magazines before the next fighter came in.

Belt feeds had their own problems where defensive cannon were concerned. The feed had to supply a cartridge belt from the ammo box to the gun breech, regardless of the elevating and traversing gun. Getting belt guides to make the smooth transition in these circumstances was difficult, and could well require a power-assisted feed (adding to the weight).
 
The larger caliber, explosive shells, and longer range of the 20-mm gun were presumably thought to be a good tradeoff for the lower rate and volume of fire compared to rifle-caliber machine guns. The cannon could engage attackers sooner, while farther away, thus compensating for the slower rate of fire. Moreover, larger, explosive projectiles could destroy a target with fewer hits, thus compensating for the lower volume of fire and consequent reduced probability of getting hits.

But it seems to me that the choice of gun makes very little difference. Defensive fire from flexible or turreted guns proved singularly ineffective in combat. Defiants failed disastrously in the day fighter role. Wellington, Halifax, and Lancaster gunners died in large numbers (along with navigators, pilots, and bombardiers) because the weight, drag, and tactics produced by their mere presence and equipment made their aircraft more rather than less vulnerable to fighter attack.

Freeman Dyson recounts somewhere how RAF Operational Research recommended stripping out all but the tail turrets on Lancasters, because calculations show that doing so would boost their speed and altitude performance just enough to make interception by Ju88s and Bf110s practically impossible. And of course, Mosquitoes proved the point in action. But Bomber Command stuck to its guns, basing its decisions on "common sense" and wildly inflated gunner's claims, until the V-Bombers.
 
In one of the books I have on the Spitfire, there's a diagram showing the different gun arrangements along with the firing rate, eg, eight .303's, two 20mm's and four .303's, two 20mm's and two .5's, four 20mm's. The firing rate wasn't expressed in volume, it was shown in 'weight per pound' of rounds fired in a minute ---
Each development produced more weight per pound than the previous one. I just need to find the book now ----
 
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).

Schoolgirl who helped to win Battle of Britain - Carmel College

Today marks 80 years since the start of the Battle of Britain in July 1940, the RAF is publicly acknowledging the contribution made by Hazel Hill
www.carmel.ac.uk www.carmel.ac.uk
 
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