Boulton Paul Defiant

[Flitzer]

I was wondering...(always a bad sign)...

The Defiant proved quite effective for a short time, until Luftwaffe crews quickly learned its limitations.

How good a fighter might the Defiant have proved if it had been designed from the outset to have a more conventional armament arrangement rather than the turret?

Any views?

Cheers
P

 

[archipeppe]

I was wondering...(always a bad sign)...

The Defiant proved quite effective for a short time, until Luftwaffe crews quickly learned its limitations.

How good a fighter might the Defiant have proved if it had been designed from the outset to have a more conventional armament arrangement rather than the turret?

Any views?

Cheers
P

Good question, I suppose anyway not better than an Hurricane Mk I.
Probably Reginald Mitchell's Spitfire would remain at the top of pyramid.

 

[Abraham Gubler]

A good starting point for answering this question is British Secret Projects: Fighters and Bombers 1935-1950 by Tony Buttler. This book has a big chapter on turret fighters designed for the first RAF spec (which resulted in the Defiant) and the later spec (never built). The most important thing there is the reason why the RAF ordered turret fighters which is often not known by many willing to pass judgement on it.

They were designed for anti-bomber operations not fighting other fighters. The idea was that because bombers were becoming so heavily armed attacking fighters would need a lot more firepower. There were two solutions: arming fighters with heavier cannons and massed fires by squadron formations. To achieve the later it was rightly thought that a fighter would need a turret. That why a whole squadron would stay in formation wing tip to wing tip and fly past the bombers while the turrets tracked onto the target and fired. This would have resulted with the massed fires of 48 .303 machineguns being targeted on a single bomber.

Unfortunately for the idea the bombers were being escorted by fighters which soon broke up the Defiant formations. Then the heavy weight of the turret and air gunner reduced the Defiants performance compared to non-turret fighters so they were at a major disadvantage. Especially after the attacking fighter learnt to stay out of the turret’s field of fire.

Directly answering the question of a Defiant sans turret is an article in Air Enthusiast No. 106 (July/August 2003). “The Best Fighter the Navy Never Had: Boulton Paul’s ‘Sea Defiant’” by Alec Brew details the story of the Boulton Paul P.85 a naval fighter along the same principals as the Defiant (but not a navalised Defiant). Surprisingly the Blackburn Roc was chosen as the RN’s turret fighter despite being 85 mph slower than the P.85. Even more surprisingly Blackburn sub contracted building all the Rocs to Boulton Paul!

Anyway Brew then postulates ‘what if’ the faster P.85 was built by Boulton Paul for the RN and as experience showed the flaw in the turret fighter concept. The RN being the RN this would mean deletion of the turret but not the second aircrew (an aircraft must have an Observer) which would have resulted in a 320 mph Sea Defiant. Boulton Paul also designed the P.94 a single seat Defiant with heavy forward firing gun armament (12 x .303 MGs or 4 x 20mm cannon) for the RAF requirement that lead to the Westland Whirlwind. With a Merlin XX this aircraft could reach 380 mph and could roll off Boulton Paul’s factories whenever the RN decided to not equip fighters with an observer.

 

[alertken]

This design has been traduced because of misuse of the word "fighter". RAF's 1936 name-change, Air Defence of G.B to Fighter Command was a budget-jerking wheeze: politicos wanted to concentrate spend on bombers. RAF/1930s bought no "fighter" because UK was to rely on the Maginot Line: the Abbeville Boys were French. Luftwaffe Army-support types - He.111/Do.17, transport-derived -would trundle beyond escort range towards Expeditionary RAF bases, to be taken out below/abeam/astern after visual intercept. No head-on, so no forward fire; no manoeuvre/second pass, so no superior energy. Phalanx (per AG) if the incomers had been early detected, or solo-lunge by a loitering patrol pair: the Task is less to destroy, more to disrupt, break the formation (only the leader could navigate), dump the load. No GCI, no nightwork. No type slowed by turret+its fingers and eyes could take on a nimble dasher: but those would be immured beyond the Rhine: Defiant would not meet one. Hurricane, Spitfire, Whirlwind (A to Flitzers Q: these were the no-turret interceptors), Bf.109, Bf.110 were similarly intended to be bomber-destroyers (Zerstorer). Defence Policy has failed if we are within range of no-endurance, point-defence sprinters. It did; we were.

The "even more melancholy story" (M.M.Postan, WW2 Official History, Design & Development of Weapons, HMSO 1964,P.135) of RN turret-fighter, and then of turret-less multi-role Skua, resulted from Admiralty perception, when extracting 1936 funds for 6 large Illustrii, that land-based Air would offer little threat to the Fleet on the High Seas - one Spec was for a 3-seat Spotter-Fighter! Deck armour was anti-plunging big-gunfire, not piffling 250lb. squibs making holes in the water.

Air Ministry/then Ministry of Aircraft Production "owned" Design Rights in everything we paid for; design parents had no right to production. MAP assigned work having regard to, for example, ease of moving material/engines around under bombing, no motorways, no street lights. So, Roc, Defiant and their BPA-licenced French turret, were all built snug in Wolverhampton; Roc-less Blackburn was put to assembling Swordfish in Barton, Pegasus from Accrington.

 

[Jemiba]

" Bf.109, Bf.110 were similarly intended to be bomber-destroyers (Zerstorer)."

SMART-ASS MODE ON
The Bf 109 was designed as the smallest possible aircraft with the most powerful
engine available, demanded to be the most powerful fighter. The actual task wasn't
strictly defined, I think. It had to be an interceptor, of course, but would act as an
"air superiority fighter", too. A task not envisaged was bomber escort. That was to have
been the field of the Bf 110. The competition, which ultimately led to the Bf 110 actually
called for a type with turrets/flexible gunmounts to "sweep the sky ahead of the bombers",
but as twin engined aircraft, those types (Hs 123, Fw 59) still had a field of fire directly
ahead, in contrast to the Defiant.
So, another question could be : Would a twin-engined aircraft, able to bring his guns to bear
straight ahead, have been more succesful?

SMART-ASS MODE OFF

 

[archipeppe]

So, another question could be : Would a twin-engined aircraft, able to bring his guns to bear
straight ahead, have been more succesful?

Did Lockheed P-38 "Lightning" could be a nice example??

 

[Jemiba]

I thought of something like the Beaufighter and Mossie types,
fitted with a turret, or the Bell Airacuda. The P-38 was more or less a standard
fighter, just with two engines, as was the Whirlwind or, on the german side,
the Fw 187, of course able to carry quite a heavy armament for its days.

 

[archipeppe]

I thought of something like the Beaufighter and Mossie types,
fitted with a turret, or the Bell Airacuda. The P-38 was more or less a standard
fighter, just with two engines, as was the Whirlwind or, on the german side,
the Fw 187, of course able to carry quite a heavy armament for its days.

What you want it is essentially the Northrop P-61 "Black Widow".
Big, powerful, twin engined and - overall - armed with a turret on top (not mentioning the 3 crewmembers, a radar in the nose, etc.).

 

[Avimimus]

The fundamental difficulty is gunnery: The gunner has to handle the behaviour of the turret (eg. input delays), sideways movement of the air leading to increased dispersion of the rounds (if firing other than directly ahead), forward velocity of the aircraft imparted to the bullets (making sighting difficult while firing abeam), any manoeuvring by the pilot who is pursuing the target, and finally, the relative position, speed and manoeuvring of the target. There is also the added difficulty of firing a prolonged burst into the same space (thus increasing the damage done and probability of scoring hits) and possibly recoil imparted by the turret to the airframe (on a small aircraft or if using cannons).

So, this is no small task. It is easier if one is firing on a target that is coming from the rear (or the front), and if one is firing from a non-manoeuvring or non-manoeuvring and slow platform.

Without computer assistance such a proposition is unlikely (although it may have been possible in the early trans-sonic days). Most powers over estimated the ability of gunners to accurately hit targets during the 1930s (possibly due to the relatively high speed of bombers compared to fighters throughout that period - forcing trail pursuit).

Could a design have worked? Possibly. It would have to be almost as fast as existing single seat fighters, have a small cross section and have heavy cannon armed turrets with limited ranges of fire focussing on the front and the rear. If the difference in speed was close enough and the cannons high-enough velocity it might be possible to force fighters into rear pursuit where they would become easier targets. But, it would be marginal.

 

[Justo Miranda]

Defiant projects -post-1

 

[Justo Miranda]

Defiant projects -post-2

 

[Justo Miranda]

Defiant projects -post-3

 

[Justo Miranda]

Defiant projects -post-4

 

[Justo Miranda]

Defiant projects -post-5

 

[Pepe Rezende]

They could be terrific escort fighters...

Remove the turret, substitute it with a center fuel tank and put four 20mm cannons at the wing!

Cheers

Pepe

 

[JohnR]

I thought of something like the Beaufighter and Mossie types,
fitted with a turret, or the Bell Airacuda. The P-38 was more or less a standard
fighter, just with two engines, as was the Whirlwind or, on the german side,
the Fw 187, of course able to carry quite a heavy armament for its days.

Trials were undertaken with both Beaufighters and Mossies with turrets, but it was found that the increased drag reduced performance to unacceptable levels.

With regard to the Boulton Paul P105 proposal, I do remember reading and article on it in Air Enthusiast some years ago and it was described as the Best fighter the RN never had.

 

[Abraham Gubler]

Trials were undertaken with both Beaufighters and Mossies with turrets, but it was found that the increased drag reduced performance to unacceptable levels.

These were bomber configurations with the turrets used for self defence. The biggest problem was additional weight along with a bomb load.

As detailed in "BSP: 35-50" the second RAF turret fighter specification (F.11/37) had a range of twin engine respondents. Boulton Paul also deeloped the low drag turret with four recessed 20mm cannons that was to feature in a range of unrealised RAF designs of WW2. The Boulton Paul P.92 with two RR Vultures and a turret wtih four 20mm was to have a maximum speed of 371 mph.

 

[hole in the ground]

Surprisingly the Blackburn Roc was chosen as the RN’s turret fighter despite being 85 mph slower than the P.85. Even more surprisingly Blackburn sub contracted building all the Rocs to Boulton Paul!

How much in common does the Roc have to the Skua? It may have been that the choice of aircraft was partly down to standardisation. Fewer unique parts reducing the unit production cost and through life maintenance? A rare example of forward planning?

 

[robunos]

Unfortunately for the idea the bombers were being escorted by fighters which soon broke up the Defiant formations. Then the heavy weight of the turret and air gunner reduced the Defiants performance compared to non-turret fighters so they were at a major disadvantage. Especially after the attacking fighter learnt to stay out of the turret’s field of fire.

To my mind they should have added four wing-mounted forward firing guns to the standard Defiant. While this would have further increased weight and reduced performance,
it would in effect be re-inventing the WWI Bristol Fighter.
These would then be used exclusively as bomber destroyers, the pilot attacking the bombers with his forward firing guns, while the gunner used his turret to deal with the enemy escort fighters, aided by the defending fixed gun fighters.


cheers,
Robin.

P.S. My grandfather worked at Boulton Paul during the war, building Defiants......

 

[Abraham Gubler]

How much in common does the Roc have to the Skua? It may have been that the choice of aircraft was partly down to standardisation. Fewer unique parts reducing the unit production cost and through life maintenance? A rare example of forward planning?

The Roc is pretty much a Skua with the four gun turret added. While this might have alleviated the Royal Navy's spares storage onboard carriers it resulted in a rapid loss of aircraft requiring said spares. There comes to the point where standardisation does not deliver dividends? A 30% loss in speed for this mission is not worth using the same airframe.

To my mind they should have added four wing-mounted forward firing guns to the standard Defiant. While this would have further increased weight and reduced performance,
it would in effect be re-inventing the WWI Bristol Fighter.
These would then be used exclusively as bomber destroyers, the pilot attacking the bombers with his forward firing guns, while the gunner used his turret to deal with the enemy escort fighters, aided by the defending fixed gun fighters.

I don’t think this would have helped them much because the Defiant turret was not designed for defence against fighters – but for attacking bombers – so it lacked a good firing arc to the rear.

The Armstrong Whitworth design for the RAF F.11/37 specification (that followed the Defiant) was an interesting configuration. It had twin wing mounted pusher Merlin engines for a top speed of over 400 mph. The pilot was in the nose and above and behind him, but forward of the leading edge, a turret with four 20mm cannons. This turret could rotate and fire at targets in the forward ~270 degrees (but only above horizontal). Such a fast fighter would be highly lethal in head to head engagements where the only counter to its interception would be to dive under it. Its high speed would then be used to outrun any maneuvering fighters. Against a bomber formation it could sit beside and below them (in a blind spot or out of range of MGs), match their speed and let the gunner fire away.

 

[Flitzer]

Very interesting comments.

The nearest illustration of what I was thinking about is shown in Justos reply Defiant-posts-2 Escanear 0009.

My thoughts were if Boulton Paul produced the Defiant purely as a fighter (without the turret of course) how good might it have been?

I think Archipeppe is right in that the Spitfire would still be king.

Cheers
P

 

[AeroFranz]

This might just reinforce previous comments, but AFAIK, the single-setaer Defiant compared favorably with the Hurricane, but probably not with a Spit in the fighter role.

 

[Flitzer]

This might just reinforce previous comments, but AFAIK, the single-setaer Defiant compared favorably with the Hurricane, but probably not with a Spit in the fighter role.

Thanks Areofranz,
that's more or less what I was sort of expecting.
Stripped of its turret the Defiant is not a bad looking aircraft.

 

[Justo Miranda]

What if?
Single seat long range escort fighter Defiant versus Mustang Mk.I ?

 

[Flitzer]

What if?
Single seat long range escort fighter Defiant versus Mustang Mk.I ?

Could prove an interesting subject for a profile.
Extra fuel tanks? Single under belly or twin underwing?

 

[Justo Miranda]

-Twin underwing fuel tanks
-One undernose long range oil tank
-Suggested 137 Squadron paint scheme and codes

 

[Abraham Gubler]

This might just reinforce previous comments, but AFAIK, the single-setaer Defiant compared favorably with the Hurricane, but probably not with a Spit in the fighter role.

A closer look in BSP: 35-50 shows there is actually an answer to the original question about a turretless Defiant! The prototype Defiant (K8310) was flown without the turret in August 1940 as a performance demonstrator for the Boulton Paul P.94 emergency fighter. This would use the existing Defiant production line to mass produce a general purpose fighter for the hard pressed post Battle of Britian RAF. The P.94 was basically a Defiant without the turret and a Merlin XX and could fly at 360 mph and had a rate of climb of 3,235 ft/min.

Compared to a Spitfire VB the P.94 is slightly slower at maximum speed (360 vs 378 mph) but has a faster rate of climb (3,235 vs 2,665 ft/min) at sea level. It is however faster than the Hurricane IIC (360 vs 340 mph) and also a faster climber (3,235 vs 2,780 ft/sec).

However the P.94 would be armed with 12 forward firing Browning .303 MGs for an increase in fire power of 50% over both the Spitfire and Hurricane. The 12 Brownings could be replaced with four Hispano 20mm cannons and four Browning .303 MGs. The MGs could also be depressed up to 17 degrees below the horizon to enable level flight strafing. The P.94 could also carry auxiliary tanks for long range fighter duties.

The production of conventional fighters at the Defiant line was rejected by the air ministry in mid-late September 1940. A heavily armed gun fighter/strafer that could actually fly in squadron service in 1941 would have provided much of the Typhoon capability three years earlier.

 

[Justo Miranda]

I thought of something like the Beaufighter and Mossie types,
fitted with a turret, or the Bell Airacuda. The P-38 was more or less a standard
fighter, just with two engines, as was the Whirlwind or, on the german side,
the Fw 187, of course able to carry quite a heavy armament for its days.

Trials were undertaken with both Beaufighters and Mossies with turrets, but it was found that the increased drag reduced performance to unacceptable levels.

Please see http://www.secretprojects.co.uk/forum/index.php/topic,3537.0/highlight,beaufighter+turret.html

With regard to the Boulton Paul P105 proposal, I do remember reading and article on it in Air Enthusiast some years ago and it was described as the Best fighter the RN never had.

 

[hole in the ground]

The P.94 was basically a Defiant without the turret and a Merlin XX and could fly at 360 mph and had a rate of climb of 3,235 ft/min.

Compared to a Spitfire VB the P.94 is slightly slower at maximum speed (360 vs 378 mph) but has a faster rate of climb (3,235 vs 2,665 ft/min) at sea level. It is however faster than the Hurricane IIC (360 vs 340 mph) and also a faster climber (3,235 vs 2,780 ft/sec).

However the P.94 would be armed with 12 forward firing Browning .303 MGs for an increase in fire power of 50% over both the Spitfire and Hurricane. The 12 Brownings could be replaced with four Hispano 20mm cannons and four Browning .303 MGs.

I wonder how much slower the P.94 would be with the weight of all that weaponry, or how much faster a spit or hurri would be without theirs...

 

[Abraham Gubler]

I wonder how much slower the P.94 would be with the weight of all that weaponry, or how much faster a spit or hurri would be without theirs...

The speeds of each aircraft with their weapons are as quoted. That is P.94 with 12x .303 (or 4x 20mm, 4x .303) and the Spitvifre VB with 8x .303 and the Hurricane IIC with 8x .303. By flying the converted new P.94 Defiant the engineers at Boulton Paul were able to predict performance of a production aircraft very closely. Obviously the demonstrator flew with the Merlin XX, no turret and with weights to simulate the heavy forward firing armament.

 

[hole in the ground]

Ah ok. That was not explicit in an earlier post. Thanks for clearing up the misunderstanding.

 

[Hammer Birchgrove]

I thought of something like the Beaufighter and Mossie types,
fitted with a turret, or the Bell Airacuda. The P-38 was more or less a standard
fighter, just with two engines, as was the Whirlwind or, on the german side,
the Fw 187, of course able to carry quite a heavy armament for its days.

What you want it is essentially the Northrop P-61 "Black Widow".
Big, powerful, twin engined and - overall - armed with a turret on top (not mentioning the 3 crewmembers, a radar in the nose, etc.).

The turret had issues IIRC - got removed.

 

[elmayerle]

I thought of something like the Beaufighter and Mossie types,
fitted with a turret, or the Bell Airacuda. The P-38 was more or less a standard
fighter, just with two engines, as was the Whirlwind or, on the german side,
the Fw 187, of course able to carry quite a heavy armament for its days.

What you want it is essentially the Northrop P-61 "Black Widow".
Big, powerful, twin engined and - overall - armed with a turret on top (not mentioning the 3 crewmembers, a radar in the nose, etc.).

The turret had issues IIRC - got removed.

For a while until the technical problems got sorted out; then the turrets got installed.

 

[Hammer Birchgrove]

Thanks.

 

[Flitzer]

Many thanks.
Loads of interesting information.

So to my original question
How good a fighter might the Defiant have proved if it had been designed from the outset to have a more conventional armament arrangement rather than the turret?


I gather the answer would have been a decent prospect, at least on a par with the Hurricane but not the Spitfire.
But would it have improved with engine developments and for example a cut down fuselage with bubble canopy?

Many thanks
Peter

 

[merlin]

The Defiant was a replacement for the Hawker Demon, but the Demon was like the Bristol Fighter of WW1 in that it had both forward & rearward guns. Hence, the the pilot for the Defiant became not a 'fighter pilot' but a taxi driver for the gunner!
The Bristol Fighter, because of its large engine was able to combat the more nimble German single-seat fighter - if anything it was faster. That ws not going to be the case with the Defiant. But yet as others have said it was only intended to combat bombers - then what were they doing in the BoB in 109 range!?
The Defiant was one of Sholto Douglas' pet projects - Dowding wasn't a fan. So doesn't seem implausible that with his 'contacts' with Boulton Paul, the P.94 proposal might have come earlier - e.g. after Dunkirk. And with the jigs and tools already in place could have been available in time for BoB. No, not as good as a Spitfire but better than a Hurricane.

 

[Tzoli]

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!

 

[JFC Fuller]

But yet as others have said it was only intended to combat bombers - then what were they doing in the BoB in 109 range!?

One suspects it was never considered that France would fall and that therefore German fighters would never get that close to British air space. I have often thought of the Defiant as a waste of resources though it is worth noting that at the outbreak of war a total of 3,500 Hurricanes, 2,160 Spitfires and 1,000 Tornados/Typhoons on order against just 363 Defiants (also worth noting the 200 Whirlwinds). With that said, it would probably have been helpful if Boulton Paul had been contracted to set up a Spitfire line at its new (and one assumes therefore modern) Wolverhampton factory rather than pursue development and production of the Defiant.

 

[GTX]

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!

Covered on the first page of this thread.

 

[Archibald]

A bizarre idea. At some point in the darkest hours of the Battle of Britain, could standard Defiants have their turrets removed and gun / machine-guns pods stuck under the wings - to turn them into decent fighters ?
We suppose there would be a "cover" above the turret hole in the fuselage, of course...

(Edit, many years later: would be an interesting alternative to the P.94)