Boulton Paul Defiant Rationale

[buffnut453]

The concept, as whole, only works as long as your expected enemy FAILS to develop power turrets of their own and/or fails to develop larger than rifle caliber machine guns. Had the Germans, for instance, developed a power turret in this time period then you would have had your hypothetical squadron/formation of Defiants flying a parallel course and similar speed to a squadron/formation of He 111s with power turrets of their own. Kill to loss ratio would not have been good.

True, but depending on your enemies not to do what you yourself are doing at some point several year in the future is poor planning. The French were fitting power turrets/mountings on some bombers in 1939/40.
Power turrets were not secret technology. Yes the Germans screwed up by trying to jump to remote control barbecues instead of using manned turrets but planning your air defense strategy/tactics in 1937/38 on the assumption that the Germans WILL NOT develop and fit power turrets in 1940/41 seems to be wishful thinking.

In fairness, NONE of the Axis powers developed a really effective power turret set-up for ANY of their bomber aircraft. Even the USAAF struggled with bomber defences. When the B-17E/F started operations in August 1942 it had virtually no forward defences. It wasn't until the B-17G came along over a year later that the type finally received a decent power-operated front turret.

The point I'm trying to make is that new military technology is inevitably evolutionary in nature, with new capabilities being neutralized by an adversary's change in technology or tactics. While your points are valid about the Defiant, there's a degree of retrospectroscopy about them. After all, if it was so blindingly obvious, why didn't ANY Axis nation develop power-operated turrets and why did the B-17 start its combat career in the middle of 1942 without adequate forward-facing defensive weapons?

Sometimes, a particularly foresighted individual (Dr R.V. Jones is one example) has the ability to think through the logical results of technology to "see the end from the beginning". All too often, however, the lessons are only learned in the harsh petri dish of combat...with concomitant loss of brave personnel until a fix is found and implemented.

 

[stona]

The reason for the turret, or any other system of gunnery operated by someone other than the pilot, goes back to the 1920s. In the case of the Defiant it has roots in Maund's 'Bright Idea Fighter' of 1930.
Maund emphasised that fighters would have to attack in formation in order to bring sufficient weight of fire to bear on enemy bomber formations. If the pilots had to aim, they HAD to take their eyes of their formation leaders and this led to a risk of collision. This was deemed so serious that it was not acceptable in peace time training, though some felt it acceptable in war. (Five out of twelve squadron commanders consulted considered it acceptable in a real shooting war.)
The result was gunnery systems in which the pilots did not have to aim, that being delegated to gunners. One of these systems was the turret fighter.

The Defiant was ordered in 1938. The British did not develop its power turret. The turret was based on the French SAMM turret, the rights for which were purchased by Boulton Paul in 1935.

If you think the turret fighter was a bad idea, it did not satisfy the obsession with formation attacks and the required concentration of fire. 'Traversing' guns, 50 degrees was a frequently mentioned amount of traverse, fitted in the wings of fighters were very seriously considered. It was thought that this might reduce the total number of guns required to be fitted. Luckily it was never tried in a production aircraft or we would be having an entirely different discussion!

Defiant tactics were never properly worked out, because they never got to operate against large unescorted bomber formations. The widespread belief that bombers would be able to defend themselves adequately from attacks by fixed gun fighters, however well armed, is what led to support for the idea of multi seat fighters which would be able to do so.

Nobody seems to have believed that the Defiant needed forward firing armament. First it would have been aimed by the pilot, and the whole design concept was predicated on avoiding this. Secondly there was no use for such armament in the turret fighters intended role. A proposed development of the Defiant, a twin which would allow the turret to fire directly forward without blowing off the propeller, was to have one machine gun in the wing to engage 'low flying targets'. Why this was needed I'm not sure. It was the result of a request from Dowding.

One thing this thread has demonstrated is what a wonderful thing hindsight is

Cheers

Steve

 

[MIflyer]

Well, the B-17 as envisioned in the 1930's would be operating at 25,000 ft or above, and the early models with less armament and no power turrets could reach speeds of 325 mph at that altitude. In the no-radar days of the 1930's it was a Stealth Bomber, or at least an "Oh Sh!t!" bomber. The enemy would not make head on passes because they'd be lucky to even be able to make passes from behind; none of their fighters had two stage supercharging.

Imagine how the Y1B-17 looked to the USN when it came out. Capable of 325 mph at 25,000 ft, over 50 mph higher than the F3F and the same top speed as the F2A but at 10,000 ft higher. Equipped with a "pickle barrel accuracy" bombsight. And with no radar there was no way to detect it until you saw the contrail. And able to intercept even lone ships far out at sea, as Lemay demonstrated with that Italian ocean liner. No wonder the USN first secured an agreement from the Army to not allow their bombers to fly far out to sea and then got Grumman working on a fighter with two stage supercharging. The first battle any weapons system has to win is in Wash, DC, and the USN was about to lose a big one. I have copies of the Washington Times headlines after Gen Mitchell sunk those German battleships, "Millions Wasted on Battleships When Airplanes Could Defend the USA." And then, over 10 years later, in the middle of the cash strapped 1930's, their worst fears were realized.

 

[buffnut453]

I can't disagree with your comments about the disparity in fighter performance when the YB-17 came. However, by August 1942, there had been almost 3 years of combat experience in Europe involving the most modern fighters, many of which were perfectly capable of intercepting a 325mph bomber at 25,000ft. So why did it take another year for a front turret to enter service? The answer is that people aren't commonly blessed with the foresight necessary to identify such needs. In other words, it takes the loss of many aircraft and their crews before action is taken.

 

[MIflyer]

Well, I am even more astonished when you consider that at the end of WWII we had all of the elements required to build air-launched precision guided stand-off weapons, such as the JB-2 Loon/V-1, that could have been launched from B-29's. Radio and TV guidance had been developed and the Bat missile actually used in combat by the USN could have provided radar guidance for an anti-ship version. Without the need for any panic-style wartime development effort such weapons could have been available in time for the Korean War,. But in reality they were not even available in time for Vietnam!

I worked in the Pentagon for 4.5 years. One of their proudest boasts is, "We refuse to be constrained by the excessively limited parameters associated with rational thought."

 

[Shortround6]

We need to not use hindsight when either criticizing a design or defending it.
The Defiant was not designed to shoot down "glass nosed" German bombers.
The "glass nose" versions were not in existence during the first few years of the Defiant's "life" (design/development)

Granted the sheet metal offered very little more protection than the clear panels.
However on the flip side.

First bomber with a power turret (it wasn't very good). It flew in 1934 with the turret.

with nose turret, flew a year before the Defiant prototype.

Turret may not have been power operated but then the plane dates from the first 1/2 of the 30s.

Amoit 143, in service in 1935, again turret might not be power operated?

depending on the opposing force/s NOT to put power turrets (like the British themselves were doing) in the noses of their bombers in the 2-3 years it would take for the Defiant to go from prototype to squadron service seems to be wilful ignorance.

 

[fubar57]

Interesting kite, a rudder attached to the rudder to improve control, from Post #26...

 

[buffnut453]

depending on the opposing force/s NOT to put power turrets (like the British themselves were doing) in the noses of their bombers in the 2-3 years it would take for the Defiant to go from prototype to squadron service seems to be wilful ignorance.

Or, perhaps, the RAF's technical intel types had evaluated the German bomber fleet and had calculated that they couldn't fit multi-gun power turrets into those aircraft without considerable loss of payload or performance? Bear in mind that most were developed from civil airliners that could be accessed with ease prior to the war. Therefore, just maybe it was an informed decision rather than willful ignorance? You can't just slap several hundred pounds of extra turret weight, plus the need for a dedicated gunner ('cos you can't just run from one flex mounted gun to another as was attempted by the Luftwaffe in their bomber fleet), without a major performance penalty.

I would also say that the presence of power turrets on an adversary aircraft does not mean the Defiant is automatically useless as a bomber killer. Every bomber had weak spots in its defensive coverage and those could be exploited in combat. Again, the B-17 provides a classic example of that problem coming to fruition...and that was in an airframe that was much larger than any bomber the Luftwaffe had.

Yes, the RAF was fitting power turrets into every heavy bomber from the Whitley and Wellington onwards but every one of them had blind spots. The addition of mid-upper turrets was an attempt to prevent beam attacks but, even then, there were considerable blind spots beneath the bombers that would have been ideal for a fighter like a Defiant.

 

[Greyman]

As I posted before, the British were banking on the Germans up-gunning and up-armouring their aircraft. This was seen as strengthening the turret-fighter concept, not invalidating it.

The 'glass nose' of German bombers wasn't so much the significance, it was that most of the crew was bunched up there.

 

[KiwiBiggles]

Interesting kite, a rudder attached to the rudder to improve control, from Post #26...

View attachment 496186​

I think it was a primitive servo-tab, to allow the pilot to move that enormous rudder.

 

[Shortround6]

Or, perhaps, the RAF's technical intel types had evaluated the German bomber fleet and had calculated that they couldn't fit multi-gun power turrets into those aircraft without considerable loss of payload or performance? Bear in mind that most were developed from civil airliners that could be accessed with ease prior to the war.

No, they weren't. There were a few attempts to pass off some early He 111s and DO 17s as passenger aircraft but they were pretty poor examples of commercial aircraft. Acrobatics should not be required for a paying customer to reach their seat. On the HE 111 4 of the 10 passengers sat in a "smoking compartment" separated from the other six. It was actually the bomb bay.
The JU-86 was a "dual purpose" plane but stacks up pretty poorly as a transport of the era.

You can usually find a blind spot it you look hard enough but the idea the Defiant (or any turret fighter) could "sit" in a zone and fire with near impunity at a formation of bombers just doesn't hold up.
British thinking seems to have been rather muddled at the time. Fighter pilots could not shoot down bombers using fixed guns but SOME bombers were expected to defend their front hemispheres (or front arcs) with fixed guns? (Blenheim, Battle, Wellesley, Hampden).

 

[buffnut453]

You're missing (or ignoring) my main point. You can't just slap a power turret in a relatively compact twin-engined bomber if the airframe wasn't designed to carry the weight from the start. Clearly the He111, Do-17 and even the Ju-88 were NEVER designed to carry the extra weight of multiple power turrets, and that ought to have been blindingly obvious to anyone with aeronautical engineering qualifications. Ergo, your point about "what if the Germans put turrets on their aircraft" is merely an impractical "what if"...and the Air Ministry may well have understood it as such.

I don't think anyone said that the Defiant would do anything "with impunity" but, equally, the presence of power turrets on bombers does not negate the role of a turreted fighter to go against bombers. If that was the case, why put a turret on the P-61? And, yes, I know the turret was a complete failure but, equally, why specify it in the first place?

Yes, British thinking was muddled but so was everybody else's to some degree or other, as evidenced by German obsession with the tactical ground campaign, USAAF over-emphasis on the abilities of heavy bombers and Japan's inability to get the Army and Navy to cooperate on common standards.

 

[Greyman]

... the idea the Defiant (or any turret fighter) could "sit" in a zone and fire with near impunity at a formation of bombers just doesn't hold up.

Impunity wasn't the idea, to have fire superiority in a zone was.

 

[nuuumannn]

British thinking seems to have been rather muddled at the time. Fighter pilots could not shoot down bombers using fixed guns but SOME bombers were expected to defend their front hemispheres (or front arcs) with fixed guns? (Blenheim, Battle, Wellesley, Hampden).

You seem to believe that with a click of the finger and your astounding ability to conjure up hindsight like it was something British planners had oodles of, everything should have been done differently, SR; this seems to be a staple of almost every argument you enter into about British aircraft. Hindsight does give us the power to rubbish the turret fighter, (or anything British, in your case) but the reality was the rule book hadn't been written yet in terms of fighter tectics. New technology brought about new problems and attempting to solve them was very much hit and miss. When aeroplanes were first being developed in the first decade of the 20th Century, how many iterations of controls in the cockpit were there? Heaps, until a successful forula was settled on, with experience.

It took timeand the proverbial blood sweat and toil to get there. Yes, the idea was flawed, but the Air Ministry didn't know that in 1935 when the spec that produced the Defiant was released would be so. The fear of massed formations of bombers was real to these guys. Remember, that same fear spawned the Zeppelin threat in Britain during the Great War; fear of German airships carrying out mass attacks on Britain drove this, yet the reality, although casualties were recorded and damage done was not what was expected. That did push the British to evolve an air defence network unlike any other however. Such is the benefit of experience. The fear of modern fast monoplane bombers in formation was a likely argument to evolve a turret fighter if your country has the technology to do such a thing.

By 1939, Britain had 3 major power turret manufacturers, BP, Bristol and Fraser Nash. No other country had bombers armed with power turrets in service at that time. The Sunderland was the first 'modern' all metal monoplane 'bomber' to be so fitted. Interestingly, the first American bomber put into production with power turrets was the B-24; in the Liberator II, a variant built expressly for the British, the bomber was completed without armament, delivered to Britain and Boulton Paul turrets were fitted to it.

That the BP Overstrand was 'not very good', compared to what exactly, SR?! Again, you are attempting to impose standards by which these things are judged that simply did not exist at the time!

 

[XBe02Drvr]

I think it was a primitive servo-tab, to allow the pilot to move that enormous rudder.

And badly needed! Did you see those big fixed-pitch non-feathering props and that short fuselage? I bet an engine failure in flight in that beast with "one churning and one windmilling" would render it virtually uncontrollable without some rudder help for the pilot. (An ATR-72, even with rudder boost and autofeather, needs 90 lbs rudder pedal effort to maintain control in a V1 engine failure, as my girlfriend experienced in her first week on the line with Eagle.)
Cheers,
Wes

 

[GrauGeist]

When the Do17 and He111 were designed, Gemany was still constrained by the Versailles treaty, so they had to be thinly disguised as commercial aircraft. Provisions for turrets would have been rather obvious at the time.
The Ju88's concept was to be a "fast bomber", so the primary intention for defense, was it's speed - which was an ideaology of the 1930's.
Even the Me264 was designed for speed (again, a holdover of 1930's ideology) and relied on flexible-mount armament rather than turret mounted defenses, although it was considered later on.

 

[stona]

The fundamental flaw in the Defiant and turret fighter concept was not the turret. If German bombers had appeared in large formation without escort the theory might well have worked.

The more fundamental flaw was that the Defiant was not fast enough. Many at Fighter Command did not believe it was capable of intercepting the bombers. If you can't make the interception it doesn't really matter what armament you carry or how it is configured.

In the end Fighter Command was left grasping at straws.

It appears the trials just caused more confusion, as more than three months later it was still not clear what the Defiant could do.

Cheers
Steve

 

[Shortround6]

You seem to believe that with a click of the finger and your astounding ability to conjure up hindsight like it was something British planners had oodles of, everything should have been done differently, SR; this seems to be a staple of almost every argument you enter into about British aircraft. Hindsight does give us the power to rubbish the turret fighter, (or anything British, in your case) but the reality was the rule book hadn't been written yet in terms of fighter tectics. New technology brought about new problems and attempting to solve them was very much hit and miss. When aeroplanes were first being developed in the first decade of the 20th Century, how many iterations of controls in the cockpit were there? Heaps, until a successful forula was settled on, with experience.

It took timeand the proverbial blood sweat and toil to get there. Yes, the idea was flawed, but the Air Ministry didn't know that in 1935 when the spec that produced the Defiant was released would be so. The fear of massed formations of bombers was real to these guys. Remember, that same fear spawned the Zeppelin threat in Britain during the Great War; fear of German airships carrying out mass attacks on Britain drove this, yet the reality, although casualties were recorded and damage done was not what was expected. That did push the British to evolve an air defence network unlike any other however. Such is the benefit of experience. The fear of modern fast monoplane bombers in formation was a likely argument to evolve a turret fighter if your country has the technology to do such a thing.

By 1939, Britain had 3 major power turret manufacturers, BP, Bristol and Fraser Nash. No other country had bombers armed with power turrets in service at that time. The Sunderland was the first 'modern' all metal monoplane 'bomber' to be so fitted. Interestingly, the first American bomber put into production with power turrets was the B-24; in the Liberator II, a variant built expressly for the British, the bomber was completed without armament, delivered to Britain and Boulton Paul turrets were fitted to it.

That the BP Overstrand was 'not very good', compared to what exactly, SR?! Again, you are attempting to impose standards by which these things are judged that simply did not exist at the time!

How about getting a grip.
A lot of what I complain about the British is because they ignored the lessons of the First World War. Bringing up that they ignoring things that happened (and were paid for in British blood) hardly requires hindsight on my part.
There are somethings the British did very well, other things not so well. Like a lot of other countries.
The Rule Book of fighter tactics had been written, in large part, by the end of WW I. Ignoring it or trying to come up with alternatives to it should have called for some sort of testing.
I have no trouble with issuing a specification in 1935 to explore the "idea". The problems start creeping in with ordering hundreds of production examples when the Prototype had barely flown (without turret) and before firing trials were even conducted against towed targets.
How about if I quote an English author?
Francis Mason page 234 "The British fighter Since 1912" on the Hawker Demon.

"It has to said at this point that, while the Demon performed the task to which it was allotted--- that of providing a 'defence' against the Hawker Hart during defence exercises---- its entire concept in the wider sense was flawed. Sydney Camm is on record as having stated that his proposal 'to set a Hart to catch a Hart' was never intended to be more that a very short term expedient. He was well aware that his new Fury was the answer to any bomber threat extant in Europe in the early 'thirties. Indeed, the Demon came to be perpetuated as a product of financial necessity. Unfortunately, what came also to be perpetuated, probably owing to the success of the Demon in its very limited context, was that the two-seat interceptor represented an essential item of equipment in the RAFs arsenal,
which it most certainly was not."

At this point the Demon had yet to be fitted with a "turret" (the turret may have been hydraulically powered in travers only?) The turret version (only 61 built?) was not delivered until 1936.
Again from Mason
"By the time of the Munich crisis of Sept 1938, the two year old Fighter Command fielded eight Demon squadrons---- a larger number at home than at any other time. Unfortunately this apparent dependence upon a two seat, single engine interceptor had artificially established within the Command a class of fighter which, when considered for replacement, engendered a requirement for a replacement--- the Boulton Paul Defiant, as it transpired---which, in the great air battle of 1940, was not only found to be technically and tactically flawed but, worse, was wholly superfluous to the needs of fighter Command."

Now had any test intercepts been done with Demons using gun cameras to prove (or at least gather data) on the proposed tactics? Before ordering over 500 Defiants?

AS for
"That the BP Overstrand was 'not very good', compared to what exactly, SR?! Again, you are attempting to impose standards by which these things are judged that simply did not exist at the time!"

This constant defending of what amounted to obsolete junk is getting a bit tiresome.

The Overstrand was a modified Sidestrand (first flown in 1928) which equipped one squadron. A late production example (J9186) was used to help test a succession of Jupiter engines and cowls. Finally in 1933 John North suggested fitting it with Pegasus engines instead of the Jupiters. The Original suggestion was to rebuild the original airframes but only a few were re-engined and 24 (?) were built new in 1935. and issued to 101 Squadron between Sept 1935 and Jan 1936. Please note that the Bloch 210 had first flown in 1934, the S.M. 79 had first flown in in 1934 and the HE 111 had first flown in Feb of 1935.
Now what standard do you want to apply? Yes I am comparing limited production plane to prototypes but they predate the production Overstrand by over half a year at least.
I am using European planes as you seem to dislike the American ones.

Accounts differ as to the turret, some accounts say it was pneumatically powered in travers, others say hydraulic (or system was changed?) with the weight of the gunner balancing the weight of the gun in elevation.

1936 | 2850 | Flight Archive
1936 | 2876 | Flight Archive

For contemperaty description and pictures.

 

[Shortround6]

When the Do17 and He111 were designed, Gemany was still constrained by the Versailles treaty, so they had to be thinly disguised as commercial aircraft. Provisions for turrets would have been rather obvious at the time.

The Germans had built hundreds of the Do 11/13/23 series

before building the Do 17 and He 111, they just kept them out of sight for the most part.

The JU 86 was designed to the same specification as the HE 111. They were to some extent "dual" purpose if you changed the noses in front of the windscreen and plated over the holes for the top and bottom guns. However using 600-750hp engines to move just 10 passengers was never going to be economically viable.
Designs tended to follow the "market", if you could be assured of large sales to either the commercial or military market you could tailor the design to suit. If both markets looked small you tried for the "Dual Purpose" to maximise sales for investment. It also helped to have state/government run/subsidised airlines
that were willing to sacrifice profits for prestige.

 

[pbehn]

The Defiant wasn't really a radical design, maybe just a high tech development of the Bristol Fighter.