mercredi 21 août 2013

The Defiant: Obsolete concept annihilated a promising fighter (Revised 03 / 10 / 2017)



[The data I'd used are mainly issued from the complete book of fighters of W. Green & G. Swanborough and from the En. Wikipedia]



The two-seat, single engined fighter? An idea stemming from WWI...


During WW I, British engineers have developed successfully a single engined two-seat fighter, the Bristol F2B, which was also successful operationally.

This fighter was 
powerful, nimble and very fast for its times.

So, she was able to fulfill recce missions as, also bombing  and, obviously, fighting missions.

Such an idea was relevant in 1916.



The best fighters (as actually was, e.g., the Nieuport 11) were using rotary air cooled engines. When you read about these fighters were outstandingly maneuverable, it's not absolutely true.

In the "good direction" of turn, yes, they were absolutely perfect.

However, in the opposite direction, the gyroscopic effect of the engine rotation was such that the fighter must do a complicated maneuver to obtain a good firing place...

So, the defending gunner had a good chance and all the needed time to down the enemy fighter (except if he confronted men such as René Fonck or Albert Ball).

The concept revival begin in 1935 in the British Air Ministry with its specification 9/35.



May 1940 in France? A completely different context! 


The Aviation of 1935, nevertheless, was completely different!

The recent aircrafts were reliable, very easy to fly, to land, they fly incredibly faster... The Aviation was mature.


But, 
for fighter planes, actually, the most important quality to be achieved was the best possible aerodynamics.

To a structural point of view, the old structures were made with steel tubes, wooden spars and were covered with fabric.

That was easy to repair everywhere (especially in a huge colonial Empire) but unable to withstand all the 
constraints induced by very high speed.

On the contrary, the all-metal monocoque structures, with their stressed skin, were lighter, much more aerodynamically efficient, and, also, more resistant against riffle caliber machine gun fire.

The powered turret build by Boulton Paul was based on a French license of the SAMM and have been successfully tested of the biplane bomber Overstrand. Nevertheless, it was too heavy (at least 500 kg without the gunner).




The two contenders


The Defiant, conceived by the Boulton-Paul staff, was the first contender for a twoseats, single engined fighter to fly, the August 11, 1937. 


Boulton Paul Defiant - the turret is facing an aircraft flying above the one of the photograph.


She had an up-to-date all-metal stressed skin monocoque structure similar to that of the Spitfire MK I.

Powered by the same Rolls-Royce Merlin III than the
 Spitfire, she was heavier: The empty aircraft weighted 2760 kg (100 kg more than the take off weight of the Messerschmitt Bf 109 E).

The normal take off weight was 3800 kg and the wing area was 23.5 m², near from that of the Spitfire Mk I.

Obviously, her larger weight induced a reduced maneuverability when compared to a
 Spitfire.


The electro-hydraulically powered turret was broader than the fuselage, inducing clear losses in fineness.

So, the Boulton-Paul designers had conceived aerodynamic fairings pneumatically powered to minimize the speed losses (but 
notably increasing the weight).

With her turret installed, the Defiant achieved:
  • a top speed of 490 kph at 5,200 m, 
  • 8' 30" to climb to 4,600 m (a poor performance similar to that of the poor Morane-Saulnier 406...),
  • a service ceiling of 9,200 m.

The flying qualities were good.

However, this fighter suffered from her complete lack of frontal armament as, also, of any gun sight
 for the pilot (!).


Such a decision was silly.


The other contender was the
 Hotspur and stemming from the unsuccessful light bomber  Hawker Henley.

Her design used the old and heavier structural solutions used in the
 Hurricane 
(with all the same shortcomings).

Her maiden flight occurred in mid-June, 1938, 10 months after the Defiant.

She was powered by the same Rolls-Royce Merlin III engine yielding 1030 hp.

Her empty weight was 2630 kg and the take off weight 3470 kg.

Her wing area was ~32 m², very similar to the wing area of the French ground strike twin-engined bomber Potez  631.




Hawker Hotspur  - Ok, you can see a turret (not streamlined at all!), but it's not a Boulton-Paul one, and there was no weapon fitted on



The Hotspur was said lighter than her competitor, a very amazing statement, because she can be seen as a Henley - weighting 3,850 kg for take off - with the addition of a powered turret of 4 machine-guns...

The horizontal speed at altitude, tested at Martlesham, appeared better than those of the Defiant and, for a scientific observer, that was, at least, very amazing too!
  • The published top speed was 510 kph, 
  • 10' 30" were needed to reach 4,600 m,
  • The service ceiling was 8,200 m.
The top speed was identical to that of the Hurricane Mk I prototype (KL 5083)My personal opinion is that such performances were absolutely impossible to reach by the actual prototype.

Ok, the Hawker's new baby was said as 300 kg lighter than her competitor, nevertheless she was 570 kg heavier than the operational Hurricane Mk I and ~900 kg heavier than the initial
 Hurricane  K 5083 with which she must be compared.

Moreover, the aerodynamic capacities of the
 Hotspur were not good at all
  • The turret was not streamlined at all.
  • The wings aspect ratio  - 4.78 - was bad, compared to the 6.19 of the Defiant or the 6.21 of the Hurricane
  • The thick wings displayed no thinness at all.
  • Having in recollection the Hurricane K 5083 story, the Hotspur weight was 300 kg below the real one, owing some outrageous minimizing of her ballasts.
All these evidences were convergent to suspect some fake created to give a better picture of the Hawker technology.

I suspect the true top speed of the Hotspur was, at least, clearly inferior to that of the
 Defiant.

William Green wrote in his book that no real competition was organized between the two contenders. 

It is said, to and fro, that the hard work to produce the
 Hurricane explained the weak competition spirit of the Hawker's engineers. 

May be, it was one among some fairy tales used to deceive the German deciders about the true performances of the Hurricane


The first time Adolf Galland fought against
 Hurricane, as he wrote in his memories, he seemed very disappointed by the weakness of the British fighter...

At the time of the Defiant production started, Sydney Camm, chief engineer of Hawker, was starting a very long and hard way to be able to create really fast fighters.

He was designing the pretty but defective
 Tornado, which was later modified in the better Typhoon, before to obtain the very good Tempest and a bit too late, the superlative Fury
.


But, as for the false top speed of the French Morane 406 fighter, it would be better to told us the truth.


 

A British wasted chance


During the Fall of 1939, after dogfights opposing Hurricane to Defiant, all resulting in defeats for the two-seater,  Boulton-Paul staff engineers become aware of the wrong conception of his fighter.

They removed the turret and all things needed to accept a second crew member from the prototype to test the Defiant as a single seat fighter (project P 94). 

The P 94 could see her weight dropping to ~3100 kg, enabling a good maneuverability and boosting her climbing speed.

William Green wrote in
 Famous Fighters of WWII (in 1960) that the performances were "marginally better" than that of the Hurricane, but, in Wikipedia in English linguage, you may found the expected top speed was 580 kph! 

Knowing that, as also the fact that more than 1,000 Defiant were build during the first year of WWII, it is tempting to imagine the tactical weight of the reinforcement obtained by the Fighter Command with the transformation of 500
 Defiant in their P94 variant. 

But the British Government preferred to sent his courageous pilots in their obsolete Hurricane.

It was not a wise decision.


Inappropriate tactics!


CJ Ehrengardt wrote in his review Aéro-Journal hors série #7, Spitfire sur l'Europe, that Sir Hugh Dowding had incredible difficulties to obtain more Spitfire and Hurricane from the administration of the Air Ministry who want an all Defiant Fighter Command...

Anyway, if these
 Defiant have been in France, as they were, the May 10, 1940 in the morning, when most of the numerous German bomber raids were unprotected, the losses of German bombers could have been very heavier.

Moreover, some of these fighters, associated with
 Hurricane flying as high cover, could have given a good protection for the hopeless Fairey Battle during their heroic missions in Belgium and in France. 


For their first combat, the Defiant squadrons have encountered the Luftwaffe over Dunkirk.
They worked very efficiently against bombers.

Obviously, fighting the Messerschmitt was a completely different task for them.

Some initial success occurred, thanks to the surprise of the German pilots unprepared to facing such a rear defense from what they identified as a single seat fighter.


However, each time the Defiant pilots forget their peculiar weapon layout and as long they were staying at altitude, the German Bf 109 attacked them from beneath - without hazard for them - and downed the Defiant.

 During one mission, for example, for 9 Defiant sent, 7 were downed this way...

The only successful defense method was a quick spiraling descent until some meters above the ground level, forbidding any attack from beneath. This being followed by a defensive (or Lufberry) circle.

An famous over-claim of 38 German planes (!) downed was recorded at a day during which only 14 aircrafts were lost by the Luftwaffe over the complete front lines!
 


The weapons lay out: In opposite way to the Fighting Spirit


The Defiant cannot be used as the fighter pilots were trained to proceed, a huge mistake of the deciders.

First, they were not fitted with a gun-sight to fire frontally (even it was possible to turn the turret to the bow while transferring the firing commands to the pilot).

However, it should be clear to any decider the pilot was the only people to have a clear view on the aerial situation.

To steer optimally his fighter in a favorable fire place, he needed a really strong telepathic link with his gunner!

I wonder how this peoples who wrote, after the war, a lot of books about the situation awareness – a very useful concept, indeed - might have invented a so perfect situation blindness...

So, it is impossible for me to give an assessment about the efficiency of the Defiant concept.
But her pilots and crew displayed their great courage.

The lesson was not still understood for the Battle of Britain, were the stress of the pilots was much heavier.


So, the Defiant were only used to the night fighting where they appeared better than all other British planes, probably because the turret playing the role of the famous schrägeMuzik of the German night fighters.


This story is a proof  that never the Aerial Fight can be summarized to any appealing concept (as the USAF will, may be, discover with the stealth one).


From the other hand, while reading in the William L. Shirrer’s Berlin Diary the report of his visit on the beach of Dunkirk, he was told by a young German fighter pilots that the Defiant was “terrific”!


The failure of the Defiant was even worst than that of the Morane–Saulnier 406 - which may be helped by a good better maneuverability than the one of the Bf 109 E - but, as in the case of the French fighter, the aeronautic administration was the great devil...





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