Redesigning the Defiant.

Shortround6 said:

Doesn't really matter what the range is if the thing is a dog in combat.

The only chance it had at being a single seat fighter was in 1939, before the first ones were issued. By the summer of 1940 when the Prototype single seater flew it was a dated design.

Much is made of the "projected" 360mph top speed. This was "projected" using a Merlin XX engine at 21,700ft. Also projected was the ability to out climb a Hurricane IIc at sea level by about 500ft/min and be able to climb to 25,000ft in little more time than the Hurricane IIc took to get to 20,000ft.
All this while carrying 4 20mm cannon AND four .303s AND the 20mm guns could pivot downwards by 17 degrees for ground strafing.

As noted already, Production MK II Defiant's using the same MK XX engine gained a whopping 10-12mph over the MK Is.

The Spitfire with drop tanks wasn't going to be a long range fighter but at least it COULD fight in the areas it could reach.

This single seat Defiant wouldn't reach service use (with the MK XX engine) until the spring/summer of 1941.

While a bit later in timing the P-40F makes a good reality check, A bit smaller wing, a smaller fuselage, lighter weight armament, Fuel load??? and goes 360mph at 20,000ft with the same engine.

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I've already stated that CBI and MTO would be the primary battlefields, Italian and Japanese fighters would not have the edge to put the single-seater Defiant into a 'dog' category. The armament set-up proposed by BP was unrealistic, fixed 8-10 LMGs would do the job, or 2 cannons + 4 LMGs. The projected performance figures are also a bit too high, wing of P-40 was also thinner. With historical Defiant II making, what, 315 mph, a similar plane minus turret, but plus fixed guns, would gain maybe 10-15 mph. Comparable with Martlet/Wildcat, or Hurri II?

I very much doubt that it was 4 x 20 mm cannon AND 8 x 0.30" machine guns!?? 'Or' yes, but 'and' I just don't see that, especially as the Mk 1 was offered as a single-seat with 4 x 0.303" MGs.

In the OTL, the Air Ministry's decision (for the P.94) wasn't surprising - though perhaps to agree to it would have held them up to ridicule for the two-seat aircraft design that was supposed to be the 'latest thing' in aircraft design!
Likewise, there weren't any great problems in aircraft supply for the BoB, yet the BPC was frantically trying to buy aircraft elsewhere. Nevertheless the P.94 did have it's advantages. It could be built quickly using already available 'jigs tools' indeed you could probably build them both on the same production line. The aircraft did fly - though how much I don't know - but estimates are based on those air-miles, so mph maybe surprising - but not a 'wank'.

However, the flight and proposal could have been brought, perhaps as a result of an 'off-the-record' comment from Dowding after several Defiants were lost over Holland in May. It doesn't mean that hunreds of P.94s will be available during the BoB, but possibly two or three mid-late September. Interesting to what could happen next .....

If one went back to 1936, and went for a turretless version then and abandoned Boulton Paul building Blackburn Rocs production Defiants would be reaching squadrons in 1939. However the concept was for a turreted bomber destroyer against unescorted German bombers having to fly from Germany so the logic for ordering Defiants at all would have to change.

Hence the suggestions to have it as the FAA modern monoplane fighter.

Now the FAA wanted 2 seaters,, not for a navigator but to carry a TAG seaman to operate the secret carrier finding radio. Giving him a gun in a Skua was just because he was there anyway and even that was abandoned in the Fulmar and Firefly. Surprisingly enough an extra person is not that much of a weight addition so it is quite feasible for a TAG to go in close behind the pilot with a token Vickers K and it would even maintain the side area of the fuselage so a larger fin, that would be desirable if a bubble type canopy were fitted, could be avoided.

There would still be room for extra fuselage tankage which, at worst, would equal the original outer wing tanks so leaving room for fixed wing guns.

It is worth noting that the longer Defiant nose, against that of the Spitfire, was to balance the CofG against the turret weight so one could adjust a new CofG with a shorter nose and better pilot visibility. The complicated retractable low aerial was to leave a clear field of fire for the turret so, without a turret, a conventional fixed upper aerial would suffice.

Given the 1936ish date the only armament option available is .303 Browning so x4 in each outer wing.

I am slightly at a loss to understand why the Defiant wing is being seen as so thick as to preclude mid war maximum speed standards. Boulton Paul were happy to maintain the basic wing structure for their later Defiant follow on proposals with projected speeds in the @400mph range.

The wingfold mechanism can be securely mounted at the centre section/outer wing joint.

The FAA were wedded to a V type hook mounted under the fuselage. They were not going to change to one at the rear until post war so the turret supporting structure would be useable to mount the V carrier hook.

The Defiant was fitted for a light series bomb rack under each wing for 4x20lb bombs each and dive bombing (presumably shallow) was trialled pre war. If it were to take the FAA universal wing rack as on the Roc and Skua then it could take up to 250lb bombs on each wing, so would have a decent strike capability. If not with Skua type dive bombing accuracy.

So, without departing from 1936 actually available technology, we would find FAA armed with 300+mph 2 seat fleet fighters able to both meet land based fighter on equal terms and carry out light strikes almost as well as Skuas. With 2 seats, and if fitted with external tankage, they could be navigated occasionally on long ferry flights allowing replacement planes to arrive whilst carriers were still on station. The RAF would be unaffected as there was enough Hurricane and Spitfire production to have equipped the OTL Defiant squadrons. Pilots were the limiting factor in 1940.

If they proved their worth entering service could one not see Fairey Battle production moving over to Defiant production for tactical air support to make better use of scarce Merlins in de-navalised Defiants? Cue my hobby horse of HE armed 40mm S guns.

I wonder if the date of the Air Ministry's rejection of the P.94,recorded by B.P. on 26th September 1940 (according to Tony Buttler's "'British Secret Projects, Fighters and Bombers 1935-1950") is coincidental. It matches the end of the BoB quite nicely.

Like several other 'what ifs' it was just another aircraft which was not needed.

We already had the Hurricane,which would be developed into the Typhoon,Tempest,Fury etc and another fighter beginning with S.

Cheers
Steve

stona said:

I wonder if the date of the Air Ministry's rejection of the P.94,recorded by B.P. on 26th September 1940 is coincidental. It matches the end of the BoB quite nicely.
Like several other 'what ifs' it was just another aircraft which was not needed.
Cheers
Steve

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I dont think anyone in Britain knew the Battle was won in september.

They might not have known the Battle was truly won but the crisis may have been past or the problem of new pilots vs new aircraft realized or production of existing aircraft increased enough to do away with the need for stop gaps.

fastmongrel said:

I dont think anyone in Britain knew the Battle was won in september.

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Well Park wrote,retrospectively admittedly,that in his mind 7th September was the turning point,pre-dating the disastrous Luftwaffe losses on the 15th and the well known cancellation of "Sealion" on the 17th. The 7th was the day (or evening) of the first major assault on London.

On 7th September Dowding was discussing,with Evill,how best to manage his diminishing resources. The resource most diminished was pilots not aircraft. There was certainly no need for another fighter.

In Dowding's covering letter,sent with Park's early September report to the Air Ministry on 22nd September,he wrote that Fighter Command and Park had "dealt most successfully with the rapidly changing phases of the tactical situation described in this report."

By the end of the month there is a much more optimistic tone in his (and Park's) reports and communications.I agree that they couldn't know that they had won but Dowding in particular knew that he would not be defeated before November,the target he had set himself after the Battle of France.

Cheers

Steve

Hmmmm Such a shame the Defiant didn't have forward firing armament from the start.

Having a wide fuselage, maybe the Sabre would provide great boost in power, while the increase in drag would be minimal? Or some radial - Hercules, R-2800?

There are/were sketches of further developments of the concept using the big engines and even some parts from the Defiant.

Please remember that most British radial installations are going to pretty high drag until they get a good look at the Fw 190.

Hercules is also in very short supply in 1940-41 unless you scrap the Stirling bomber program. Wellingtons don't go into combat with Hercules engines until 1941. Both the MK II with Merlins and the MK IV with P&W engines being built to make up for the shortage of Hercules engines.
Hercules engines also usually had a real problem with performing at altitude. Sources seem to be all over the map but Lumsden gives 1210-1250hp at 16,750-15,000ft depending on fuel for the MK III engine for the 5 min rating. The MK XVI (used in Beaufighter MK VIs and Wellington Xs) was good for 1545hp at 15,500ft at +8.25lbs boost and that is about as good as it got for wartime engines.

Such a shame the Defiant didn't have forward firing armament from the start.

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With or without the turret? With the turret it would have been slower, more unwieldy and have next to no range. Without and it might have made a good fighter for the time. The thing was, Boulton Paul's spoecialty was gun turrets; the Overstrand was the first RAF bomber to be fitted with a powered turret, so naturally, when the spec for a two-seat turret fighter appeared, BP were in the best position to provide an aeroplane. The design of the Defiant's turret was French, by a chappie called de Boysson and BP licence built it from SAMM; all subsequent BP turrets were based on the de Boysson turret. It was also the turret that caused Daffy production to lag, so that by December 1939 there had only been enough off the production line to equip one squadron.

The basic design of the aircraft was built for ease of maintenance and assembly and possesed good structural strength, and, removing the turret and gubbins, there's no reason to believe that the P.94 as it was projected would not have reached 350 mph, faster than the Hurricane at least. The P.94 was not built, but a number of features to be applied to advanced aircraft based on the Defiant were fitted to one called the 'Special Features Defiant for naval projects, including the P.103. This aircraft was based on the Daffy and was to be fitted with a Griffon or Centaurus.

Someone,Verney,Sorley or maybe even Dowding himself,pointed out that the best position for a Defiant to engage an enemy aircraft from was infact the worst possible tactical position,ahead and lower. The pilot could see neither what his gunner,nor what the enemy aircraft were doing. Not an exactly brilliant plan when confronted with any aircraft with forward firing armament.
Cheers
Steve

nuuumannn said:

The basic design of the aircraft was built for ease of maintenance and assembly and possesed good structural strength, and, removing the turret and gubbins, there's no reason to believe that the P.94 as it was projected would not have reached 350 mph, faster than the Hurricane at least.

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Why is there no reason to believe it would not?

does anyone have any test flight data?

Granted many aircraft changed speeds (got better) from prototype to production (many did not) but I believe the Original Defiant prototype when Flown without turret was only a few mph faster than when the turret was fitted. Why would ditching the turret on the MK II give it another 35-40mph?

I believe the Original Defiant prototype when Flown without turret was only a few mph faster than when the turret was fitted. Why would ditching the turret on the MK II give it another 35-40mph?

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Because presumably modification to the airframe, be it structural and streamlining, might have enabled a higher forward speed. You're assuming that the P.94 was simply a Defiant II without a turret; BP would not have come up with such projected figures without doing some calculation and structural redesign and whilst we can be certain that a max speed of 364 mph might be a bit optimistic, surely 350 mph would not be wide of the mark. Their calculations wouldn't be that inaccurate to mean the new aircraft's performance would be significantly lower than that, why would they bother producing a new fighter if it couldn't match the status quo?

From Tony Buttler's 'British Secret Projects, Fighters and Bombers 1935-1950.

Prototype Defiant K8310 eventually had its turret removed and in August 1940 was flown as an unarmed flying demonstrator for a fixed-gun version called P.94, which was intended for rapid production using many complete Defiant components. The P94 had the turret replaced by 12 0.303" MG disposed in each side of the wing centre section in nests of six – 4 20mm cannon replacing 8 of the 0.303" in two nests of two each were an alternative while the MG could also be depressed 17 degrees for ground attack work. P.94 had a 1,100hp Merlin XX, which offered a maximum speed of 360mph at 21.700ft, a sea level climb of 3,250ft.min and would get to 25,000ft in 8.1 minutes. To allow the type to act as a long range fighter two 30-gallon auxiliary tanks could be carried and in production the aircraft would use standard Defiant jigs. The P94 was never ordered but Boulton Paul also proposed to convert the now single seat Defiant prototype into a 4 cannon fighter demonstrator. The Air Ministry's rejection of this idea was recorded at a company board meeting on 26th September 1940.

It is worth remembering that the P94 proposal was not to offer a better fighter than contemporary ones, but to offer a fighter quickly available in addition and using existing production lines. Boulton Paul had better designs to offer for future fighters.

Projected speed for Typhoon was what, 450 mph? The Fw-190A-3 was to fly 700 km/h, at least that's what Germans wrote in mid 1942 - we know that it was never able to beat 670 km/h mark. The XP-39 (turbo, no guns armor) was trumpeted as capable to hit 390-400 mp/h, but that was not so. The P-63A also fell from projected 425 mph to ~410.

The way the P.94 was to attain 360 mph, as described cryptically in 'BSP', is of note: the gun-less Defiant K8310 was flown, yet we do not know how fast it was. We also don't know whether the P.94 ever flew, either armed or unarmed. Since the AM rejected the project on 26th Sept 1940 (the turret-less K8310 flying a month or so earlier), it indicates that P.94 was never built, let alone flew. The P-40F, as noted by SR6, offers indeed a good reality check, since it was the far more streamlined plane, flying on about the same engine, yet barely able to make 360 mph.

There is a picture way back in post number 10 of the single seat mock up for the P.94. A real P.94 never flew and never got ordered so we'll never know how fast it would have been.

It's pretty irrelevant. The turret fighter was designed for a battle that never happened. It was to intercept unescorted bombers. With the fall of France,something not envisaged in pre-war scenarios and the shock of which is hard to comprehend today,the Luftwaffe had bases that enabled its fighters to escort the bombers to London...just.

The RAF had two single engined fighters which were up to the task and they had enough of them. Introducing another one would have been pointless. Gloster,Miles,Boulton Paul,Fairey and probably others I've forgotten all fell foul of this,failing to get their designs into production.

The turretless redesign smacks of the sort of desperation shown by aircraft manufacturers on both sides to get something ordered and prevent a loss of contract. It would have been much more expensive and time consuming and equally uncertain to embark on designing an entirely new aircraft. The bodge of the turretless "Defiant" would have seemed much more attractive to the board of BP (and their accountants).Business is business,even in war time.

Cheers

Steve

For a reality check try looking at the Hawker Typhoon. Using the cube law and 2200hp for 412mph it says that 1466hp would be needed for 360mph for a Typhoon. Typhoon was a bit bigger than the Defiant but only 29 sq ft of wing (about 10%) and 2 feet more wingspan (fuselage is shorter though). Merlin XX was good for about 1120hp at that altitude.

Compressability was little known at the time. This was not only the problem with controlability in dives but a very large rise in drag as planes approach 400mph depending on design. Please note that the Hawker Tempest was 20-23mph faster using the same engine while changing pretty much only the wing.

Boulton Paul was estimating that their thick wing aircraft could almost equal the speed of a Spitfire.

Something seems a bit off.

Shortround6 said:

Boulton Paul was estimating that their thick wing aircraft could almost equal the speed of a Spitfire.

Something seems a bit off.

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Yep. Maybe they were after finance for at least a couple of proper prototypes. Mind you if they only made a more realistic 320 (ish) mph they might have had some explaining to do.

Removing the mid upper turret on a Blenheim was estimated to give a 15 mph increase in speed (according to Douglas in a minute to Newall) but this might be a bit optimistic and Douglas doesn't say where he got the estimate from.

Cheers

Steve

There was a Blenheim I tested with a number of modifications.
250 hours in filling repainting polishing.
Clipped wing tips.
Turret removed and hole filled.
Fairing the lower flat panels with sheet metal.

This got the max speed from 263 to 278mph. Please remember that the turret partial retracted and few (if any?) sources say if the turret was up or down when giving the speed.
This aircraft (L1348 ) was then fitted with constant speed propellers and run at 2750rpm and 9lbs boost at 13,000ft by the A&AEE at Boscombe Down at a speed of 294mph.
It was being evaluated as a photo recon plane by Sidney Cottons crew.

A later passage from this book "The Bristol Blenheim A complete history" by Graham Warner states the ventral gun pack was worth a 15 mph loss which meant shipping strike missions using Blenheim bombers and fighters had the strange combination of bombers being faster than their escorting fighters.

Some of the later turrets fitted to MK IV or MK V Blenheims may not have been retractable????