BP Defiant: any plausible evolution?

[tomo pauk]

The plane that received plenty of bad rap, the Boulton Paul Defiant, was one of RAF's single engined fighters in combat use during the 1st half of WW2. What kind of development and roles could you envisage for it? Some minor change to go into effect some time in 1941, and another for maybe 1943? A comment that goes beyond of 'build Spitfires instead' is encouraged

 

[Shortround6]

Build Hurricanes????

While Defiants may have had a role in 1941 in any of several versions/modifications building them in 1943 is just a waste.

Very few fighter planes designed in 1935-36 were still viable in 1941 let alone 1943. Just because the Spitfire and the 109 did it and beyond doesn't mean there is any shame in another design not making it that far. Don't forget that the Typhoons 1937 wing had some real problems with high speed drag.

The Defiant was actually just a tiny bit smaller than a Hurricane but weighed a lot more. While you can pull the turret and fair over the opening, getting rid of the extra structural weight that supported the turret ( and the heavier wings that allowed for the same "G" loads at the higher weight) is a lot harder. You may be able to streamline the plane to get speed but climb is always going to suffer without a thorough re-stressing and redesign to lighten it up. And then you are spending scarce resources (engineering man hours) to up date an old design rather than going for a new airplane that can more easily incorporate new knowledge of airfoils, structure, manufacturing techniques and so on.

 

[oldcrowcv63]

The plane looks like it would be a good candidate for becoming a decent interceptor, if not a fighter. It's got clean lines, and is nicely streamlined. It possesses the modern features of the time such as retractable gear and a Merlin engine. To some extent, that's all you need to make a superior aircraft isn't it?

The old saw if it looks good it should fly good might apply here and that may also be worth a separate thread although to make it interesting it should be relative flying qualities compared to aesthetic appeal. The Barracuda looked a monstrosity (to me) but it appears to have got the job done. The Buffalo has always remined me of a US Polikarpov I-16.

From wikipedia (my favorite source for non US aircraft )

Boulton Paul Defiant - Wikipedia, the free encyclopedia

"In 1940, Boulton Paul removed the turret from the prototype as a demonstrator for a fixed gun fighter based on Defiant components. The armament offered was either 12 .303 in (7.7 mm) Browning machine guns (six per wing) or 4 20mm Hispano replacing 8 of the Brownings. The guns could be depressed for ground attack. By that time, the RAF had sufficient quantities of Hawker Hurricanes and Supermarine Spitfire and did not require a new single-seat fighter. With a calculated top speed of about 360 mph (579 km/h) at 21,700 ft, the P.94 was almost as fast as a contemporary Spitfire although less manoeuvrable."

The capability for depressing the guns sounds like it might make a very good Fighter bomber. Range is a bit limited by US standards but not by European. I'd say trade a set of guns for some extra gas and give it longer legs. I am a believer in 4 x .50's as being quite sufficient.

 

[michaelmaltby]

Hang rockets under the wings (as with the Hurricane) and use it for Coastal Command shipping strikes ... freeing up Beaufighters for other missions.

MM

 

[davebender]

WWII Britain never had enough aluminum or Merlin engines. That's why large quantities of both were imported from North America.

The Defiant was made of aluminum and powered by a Merlin engine.

How many Spitfires or Lancaster bombers are you willing to forego to keep the Defiant in production?

If the choice is mine then the Defiant program dies without producing any aircraft at all. That frees up resources for additional Spitfires, a much more valuable aircraft.

 

[fastmongrel]

It doesnt have to be a combat aircraft. The Defiant could have been turned into an advanced trainer with a performance almost up with contemporary fighters. We always forget trainers but you can never have too many.

 

[oldcrowcv63]

Found on another forum

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.

 

[Kryten]

foreward firing armament would have been a good idea, maybe binning the 4x.303 for 2x20mm to increase range, but as pointed out above, not really a practical design for post 43?

 

[tomo pauk]

How about a fighter for FAA?

 

[oldcrowcv63]

How about a fighter for FAA?

Would it have been as robust as the Sea Hurricane or as long legged as the F4F-4? Without that ball turret, it's possible there would have been ample space for fuel and with the engine, similar fuel consumption efficiencies ... reducing armament to 4 .50's, should have help maintain a reasonable climb rate, assuming any CoG issues are overcome.... I suppose its possible and that would have made it worthwhile to produce assuming its overall characteristics were superior to any of the Martlet series.

 

[Shortround6]

The 360mph speed appears to be calculated and not proven.

The prototype, according to one account, hit 302mph without the turret. production versions hit 304mph. with the turret. The MK II with the Merlin XX was only about 8-12mph faster than the MK I which leaves one wondering where the extra 45mph to hit 360 was going to come from?
A loaded MK I was about 32% heavier than a MK I Hurricane, not all the weight was the turret.

Using it as rocket firing strike aircraft means it has around 50% more strike radius than a Hurricane II, useful perhaps but still very limiting.

Operational conversion trainers are nice to have ( two seat fighters to accustom pilots to service fighters). Merlin powered advanced trainers that DO NOT fly like an operational type and still require conversion trainers are a VERY expensive luxury.

 

[stona]

The RAF already had the Miles Master as it's advanced two seat trainer with the Bristol Mercury engine and later a U.S.Pratt and Whitney power plant. Why on earth would they want another one using the engine needed for front line aircraft.
This is just one of many dead ends for the Defiant,despite the efforts of Boulton-Paul to find a role for it.
It was designed as a turret fighter to meet a specification dreamed up by people who envisaged aerial combat rather like a 19th century naval engagement with the fighter flying alongside the bomber formation engaging it with its turret mounted armament. It was obsolete before the first one was built.
Cheers
Steve

 

[rank amateur]

It doesnt have to be a combat aircraft. The Defiant could have been turned into an advanced trainer with a performance almost up with contemporary fighters. We always forget trainers but you can never have too many.

If I'm not mistaken, Miles had a prototype in 1938 for an advanced trainer, the Kestrel with nearly the speed of the Hurricane but with a Rolls Royce Kestrel engine of only 745 hp. This eventualy went in to production as the Master but the Master turned out a lot slower. I wonder why that was but appearantly the RAF did not see any need for a high speed trainer

 

[stona]

The M.9 Kestrel first flew in 1937 with the 745 hp Kestrel XVI engine and could reach 290 mph but it never entered production. The Master I first flew in early 1939 with the Kestrel XXX power plant with 30hp less than the M.9 so it was slower but nonetheless fast for a trainer of that era. It was considered adequate by the RAF as an advanced trainer.
The Bristol Mercury powered MkII had 870 hp but I haven't got a speed for it. The Pratt and Whitney powere MkIII had 825 hp. These were powerful engines for a trainer of the time.
Steve

 

[pbfoot]

It was used extensively by the RCAF as a target tug (the drogue operator was the only ground crew rated for flight pay)

 

[nuuumannn]

The Defiant could have been turned into an advanced trainer with a performance almost up with contemporary fighters.

The Defiant was used for night fighter training with Operational Training Units, such as 54 OTU based a Charterhall (nicknamed 'Slaughter Hall' because of its worrying crash rate!) and 132 OTU at East Fortune, to name a couple. The last operational Defiants were target tugs, as Neil mentions.

How about a fighter for FAA?

This was certainly considered by BP, but for some bizarre reason, BP ended up building the awful Blackburn Roc under licence, which used the same BP gun turret. This was a largely political decision. North had big plans for FAA versions of the basic design however. BP proposed a naval fighter, the P.103 in two variants, one powered by a Griffon and the other that looked a bit like an Fw 190 powered by a Centaurus, to Specification N.7/43. As a single-seater it bore only superficial resemblance to the Defiant, notably the same main wing and tailplane profile. Maximum speed at sea leverl was 366 mph for the Griffon variant and 365 mph for the Centaurus.

The turret fighter was not really an idea that was going to be pressed on with, not least because of prejudice toward it as a result of the Defiant's poor showing during the Battle of Britain. The idea of a turret armed bomber destroyer was a smart one in theory if the German bombers were flying from Germany without single-seat fighter escort, but when they launched their offensive against France and the Low Countries in the Spring of 1940, the concept became dated almost overnight; only a few short months after the first Defiant squadron went operational (264 in December 1939).

 

[tomo pauk]

Now that you've mentioned heavier engines with more power, how about Sabre + Defiant? Defiant was in size weight somewhere between Hurricane and Typhoon, and we will ditch the turret here, too. Pilot goes back, his place will be occupied by a fuel tank. A layout similar to F4U, or Spitfire - engine, then fuel, then pilot. The tail would need some enlargement, nothing new with any plane receiving more powerful engines.
Sabre was a troublesome machine, we all know that, but it was available in 1942 (unlike Griffon Centraurus), and the performance would be astounding. In 1943 the engine issues are mostly (not totally) down, so we are left with some fighter, a least on paper

 

[Shortround6]

The Defiant was NOT in between the Hurricane and Typhoon in size even if it was in weight. The Defiant had several inches less wing span and 7 sq ft less wing area than a Hurricane. 29sq ft less than the Typhoon. The Fuselage was longer though.
Fuel tanks in a Defiant are right about where the wing guns would go, outer ends of the wing center section. MK II added Auxiliary tanks in the outer wings.

The Sabre weighs about 1000lbs (dry weight) more than a Merlin and the prop not only is heavier but at least 2 feet bigger in diameter which calls for longer landing gear or trying to 3 point the aircraft at ALL times.

The big objection to major modifications to small aircraft is that often so many changes are needed than nothing is gained by keeping the old design. Like many of the schemes to update/modify the Bf109 in order to keep the production tooling, that when they were done only used 30% or less of the existing parts. And you may have to live with compromises to use those parts that would be eliminated by just going to a new design. A clean sheet may be easier than trying to decide what parts to keep and which to change on an old one.

 

[tomo pauk]

I do agree that it should be better if the plane is designed from ground up for a particular engine, but there is plenty of instances when a that was not the case, and the up-engined planes soldiered rather well in many air forces. Spitfire comes to mind as a pretty light plane being able to accept really big engine without much of trouble.
As for where the fuel would be (either all, or most of it), it's covered in the post above:
Pilot goes back, his place will be occupied by a fuel tank. A layout similar to F4U, or Spitfire - engine, then fuel, then pilot.
Defiant's hull was somewhat wider than Spitfires, so more fuel can be there.
Defiant I was some 1000 lbs heavier than Spit V (empty weights), and some 1100 lbs heavier in MTO weight. I'd reckon that Defiant was rather a sturdy plane. Now, Spit V airframes served as a prototype for Griffon engined Spitfires, so I see no issues for Defiant to receive the Sabre. Instead of 3-blade prop, attach the 4-blade one.

An old sqetch that does not feature the Sabre, but the general idea is easy to grasp:

 

[Shortround6]

Even a two stage Griffon is 425lb lighter than a Sabre. a difference of almost 20%. Difference between a Single stage Merlin and the Sabre is about 72% increase in dry weight of the engine.


Many planes were re-engined but this is like going from a R-1830 to a R-3350 instead of stopping at the R-2600.

the Four bladed prop doesn't show up until Jan 1943 historically at the earliest and for the Typhoon it is no smaller than the 3 blade. In fact even the 5th production batch of 800 Typhoons (built Dec of 1943 to June of 1944) did not ALL get 4 bladed props.

Granted this is a what if but the further from history we get the "iffier" it looks.

Relocation of the fuel is certainly possible, it is just more engineering time and drawings and fewer common parts even if the outside shape doesn't change much.