Bf-109s and FW190s against B17s

Shortround6 said:

The British were willing to compromise armament (the bombs) and fuel load to get the guns/ammo they wanted in an existing design.
Without that compromise what would have been the result?
A compromise of less performance?
A delay while a new aircraft/engine was worked on to give the desired performance with the desired weapons load?
A compromise that saw, air ministry officials cringing in horror, fighters equipped with something other than fixed pitch propellers

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I think the Air Ministry had to compromise. Aircraft design was moving very fast in the mid 1930s and there were several specifications which needed somehow bringing together. The distinction between 'zone' and 'interceptor' fighters was becoming blurred, which had a fundamental impact on the endurance required of what would become the Spitfire and Hurricane) and the never ending quest for both firepower and speed was also leading to compromise. When they went to eight guns they also reduced the ammunition requirement per gun from 500 to 300 rounds.

It is worth mentioning that as early as April/May 1935, when the idea of eight guns, all in the wings, was being discussed, Hawker was quite keen to do away with the fuselage guns as the company was worried about making them work with the '3-balded VP airscrew' which they proposed to use.
Given the discussions around both the Hawker and Supermarine fighters, and at Rolls Royce and Bristol, about variable pitch propellers (or sometimes controllable pitch in the language of the day) the fact that Fighter Command's two principle fighters did not get a proper CSU until 1940 is a 'just in time' that did not need to be such.

Cheers

Steve

The fighters (and actually all aircraft) also had to meet field requirements like take-off distance to certain height and landing speeds and landing distance. Wings and flaps and slats/slots were also going through a very fast evolution at the time.

Spitfire "flap"

There were no intermediate positions, at least on the early Spitfires (MK IX and earlier?) It was all or nothing. Lost through the years since WW II is the terminology of the time when plain flaps were sometimes called "drag flaps" as the idea/effect was to increase drag and they had very little to do with lift. Nowadays we might call them air brakes and not be far off. They steepened the glide path on approach but did nothing for take-off so the big wing was needed for take-off performance.
In just a few years (3-4) flaps had advanced to multi-position- Fowler flaps- Zap flaps -slotted flaps and a few others that could do a variety of things.

On the gun issue " When they went to eight guns they also reduced the ammunition requirement per gun from 500 to 300 rounds."

Weight of the 303 ammo was roughly 6lbs per hundred so that savings in weight was about 96lbs or call it 100lbs which shows how tight the designs actually were. If they were worried about 100lbs while still in the design stage they certainly were NOT designing an airframe and THEN seeing what they could stuff in it.

stona said:

As I said, the type was cannon armed from its earliest service version. The cannon were initially in the outer wing position (outside the propeller arc for obvious reasons), not the wing root as I erroneously typed above (now corrected).

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Indeed, the 1st service version (A-1) was cannon armed.
My idle thinking - many RAF airmen survived due the A-1 not being outfitted with 4 cannons (whether MG FFM firing outside the prop arc, or MG 151 in different 'flavors' and installations), while 2 x 60rpg was certainly not enough for the needd envisioned.

The armament varied through the V/A-0 aircraft.
...
Whatever the original intention, the armament clearly developed along with the rest of the aircraft.

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Agree pretty much.
We can see in the tables that it took the 'big wing' to be developed in order the Fw 190 carry wing cannons. Original wing on the 1st prototypes was even smaller than what the Bf 109 had.

With concessions made on the bomb load, fuel and ammunition, Mitchell estimated that the eight gun Spitfire would be 180lb lighter than the four gun version. Of course no service version ever came close to those projected weights, all being substantially heavier.

One of Mitchell's claims for the relative ease with which the eight guns could be fitted in the wings was that his elliptical design would allow the gun breeches and ammunition containers to be close to the aircraft's vertical datum, so that the expenditure of ammunition would not adversely effect fore and aft trim. On an aircraft as small as the Spitfire I believe every pound was considered as the design developed.
Barrie Bryant, who took employment with Supermarine in October 1939, remembered that as a junior member of the technical office his job involved weighing or calculating the weight of every part of every sub assembly they designed. By the mid 1940s he would write:

"That left me as custodian of weight and balance records and recipient of growing weight work on Walrus, Sea Otter and Spitfire in its many variants, experimental and production...A year later I acquired an assistant, the first of an eventual 30 strong Weight Section. Our duties eventually included the prediction, calculation, verification and monitoring of weight, balance and moments of inertia of aircraft from conception to operational use; initiation of weight reductions; preparation of loading data; development of prediction methods; training design staff."

The Seafire 47s did have a three position flap IIRC, an intermediate 'take off' position was added. This did away with the disposable wooden wedges used to give 10 or 15 degree down against the return springs on earlier versions for carrier take offs.
I would guess that the reason for the two position flap is that it was what was required at the design stage for landings on grass aerodromes and anyone familiar with the pneumatic/spring operation of the system would understand why it would need a substantial redesign or replacement to operate as a multi position system. The Spitfire wing is notably devoid of any devices to increase lift. The Spitfire prototype had a 60 degree flaps down angle, this was later increased to that above (85 degrees)
I have read accounts of the development of the Spitfire by Shenstone, the three Fs (Faddy, Fear and Fenner) as well as Smith and various others and I don't remember any of them even mentioning the landing flaps! Both Quill and Summers mention that Summers raised and lowered them on the first test flight (the undercarriage stayed down as per his instructions) but apart from that nobody seems to have been concerned with them.

Cheers

Steve

Edit, checked flaps down angle 85 degrees

Shortround6 said:

They steepened the glide path on approach ...

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The British called that "reducing the flatness of the glide"
Cheers
Steve

Ah, yes. The English and the Americans, two peoples divided by a common language

Maybe someone said this before: over the green bar showing the votes for Focke Wulf, it is written Fw109 instead of 190. Cheers.

pbehn said:

I believe the British settled on 4 x 20mm canon for fighters sometime in late 1940/41.

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Specifications for fighters armed with four 20mm cannon or eight machine guns are almost exactly contemporary, dating to 1934/35.
It is worth pointing out that this proposed armament was FAR in advance of the armament being specified by other air forces at this time.
The initial results were the Spitfire, Hurricane and Whirlwind.

In the case of the British it was the stubborn adherence to the belief that bomber formations would be able to defend themselves from attacks by fixed gun fighters, however heavily armed, that led to the development of multi seat fighters which were judged to offer the hope of breaking up those formations. The end product of that line of development was the Defiant which when confronted unexpectedly by single seat fighters was outclassed by them, with predictable results (Dowding had predicted them). How it might have fared in a campaign against unescorted formations we will never know.

By the time the Germans were confronting the B-17 it had been established that even the most heavily armed and armoured bombers could be vulnerable to attack by fixed gun fighters, and those fighters became very heavily armed indeed.

Cheers

Steve

Unfortunately this doesn't hold up well when one considers the "possibilities".
The Defiant might have worked well when used as intended against bombers with rather pathetic defensive armament.
Like Early He 111 and Do 17s with three rcmg (rifle caliber machine guns) per plane in manual mounts. However expecting your opponents to offer up such targets was perhaps optimistic? It did work out well for the British that the Germans were slow (glacial?) in providing better defensive armament (an no 3-4 separate guns manned by one gunner who bounced between them was not that big an increase in effectiveness).

One wonders how well the Defiant would have done against bombers equipped with power turrets mounting 2-4 rcmgs each or even the French bombers with a 20mm gun in the dorsal power turret?

One also wonders at thinking that four .303 guns, no matter how well aimed/directed would be so much more effective than double the number of fixed guns in a single seat fighter 1/2 the firing time needed to put the same number of rounds on target so lethal damage might be done in a firing pass vs a broadside engagement?

Once again I refer to WW I practice in which twin gun mounts on bombers, if not very common, was at least somewhat wide spread.
Why bombers built 15-20 years after WW I ended reverted back to single guns is something of a mystery.



The German fighters with even a pair of 20mm MG/FFs offered a fair amount of fire power against the early British bombers and the early Wellingtons that suffered so badly had a pretty dismal armament set-up if I recall. The early twin mounts (not turrets) offering restricted traverse and elevation? In any case much smaller fields of fire than the later Frazer-Nash turrets. The Hampdens started with the same three rcmgs as the German bombers in manual mounts.

The B-17s did force the Germans into using several different tactics/weapons that the British had not had to resort to (or had time to develop?) in the BoB. The underwing gun pods to increase fire power but left the fighters vulnerable to escorts? (shades of the Defiant, the bomber interceptor cannot handle escort fighters?) the large rockets to break up formations so the interceptors don't have to face formation firepower? The use of large twin engine interceptors to carry enough fire power?

In the end the self defending bomber was a failure or at best a very limited success but it took several years of development of fighters, bombers and guns to reach the final but inevitable conclusion. A single seat fighter was always going to be able to carry a heavier armament than any one or two gun stations on a bomber and since the single engine/single seat fighter is much cheaper than a bomber in a war of attrition the bomber comes out on the loosing end.

When considering the British fixed gun fighter armament proposed in 1934/35 it must be compared with contemporary armament from other nations.The Bf 109 did receive cannon armament by 1940, but in the immediate pre-war period, when the Spitfire and Hurricane were carrying eight rifle calibre machine guns it carried just two (or three). Design of the Fw 190 started in 1937/8 making it a contemporary of the Air Ministry's specification F.18/37. That specification called for twelve machine guns whereas initially the Fw 190 was to have just four.
French fighters were among the most heavily armed, often with four rifle calibre machine guns and a cannon, they too made a big jump from the two machine guns prevalent in the early 1930s.
Japanese, mid 1930s, two rifle calibre machine guns.
As for the Americans, the P-36, a near contemporary of the Hawker Hurricane, only had two machine guns. The P-40 first flew in 1938 armed with just two .50 calibre machine guns (more rifle calibre guns added later).

The British worked out that, according to them, the number of fighters attacking a bomber formation would number at most 1/3 the number of bombers in that formation. Based on this formula each fighter would be required to develop at least four times the firepower of one bomber from the rear gun. When the sums were done, in late 1933, the typical rear armament of a bomber (including the latest British specifications) was just one gun, so four guns in the fighter seemed reasonable. The reasons that this was soon raised to six or eight had more to do with newer concepts of air fighting, times of engagement and rate and weight of fire required rather than anything the bombers carried. These did not apply to the turret fighter and this is why it, unlike its fixed gun counterparts, retained four machine guns. Had the Defiant proved a success, then it would have received a turret with two 20mm cannon, this was the only sensible suggestion to come out of the debates of the mid 1930s about turret fighters. Efforts had been made to develop a cannon armed turret fighter, in 1936 the Operational Requirements branch suggested replacing the four machine guns of the Defiant with four cannon but both Dowding and Freeman doubted this was possible. This led to another debate about forward firing armament, nose turrets and even a twin engine design, all of which came to nothing.

Cheers

Steve

Well somebody was smoking the wacky weed?
replacing 10KG .303 guns with 50KG 20mm Hispanos even on a two for one basis wasn't going to work.
The turret with four 20mm cannon needed a twin engine plane a pretty big one at that.

Twin 20mm turret on an Avro Lincoln.


Trying to stick one of these on Defiant ( or even a slightly up-scaled Defiant ) is going to present big problems. Once they started figuring out the drag of those large gun barrels elevating and traversing on a much smaller plane than a four engine bomber the idea became a lot less attractive.


Boulton Paul P92 with either two Vulture or Sabre engines. There were proposals form other companies.

A lot of time and money seems to have been spent on a "theory" as so far any actual firing trials have not made it into the popular press or accounts, perhaps they were done and are buried in the archives?

When the Operational Requirements Committee discussed a new turret fighter in 1936 there were two options on the table. One was a re-incarnation of the Ellington type, a three seater with two twin cannon turrets, one amidships and one in the nose and as of 16th December 1936 this was the preferred option. The other option was a development of the Defiant, with a four 20mm cannon turret amidships, but now a twin engine design, allowing the single turret to meet the requirement for forward firing armament. As of March 1937 this became the preferred option. Dowding expressed doubts about getting four 20mm cannon into a turret and was told that a high wing monoplane with the turret merged into the top of the wing was envisaged. This must surely be the P.92. The designation of the new turret fighter was changed from F.18/36 to F.11/37 and an Air Staff Requirement was issued in May 1937. Later in 1937 another specification F.9/37 was issued to Gloster for a twin engine fighter with a nose turret set up for no allowance shooting (it still hadn't been abandoned) and a four gun turret amidships. These two were now the only runners for a cannon armed turret fighter.
Just to show how enamoured the Air Ministry was with the turret concept, despite little progress being made on any of the earlier specifications, and the turret being dropped from F.9/37 (to Gloster) yet another specification was issued in early 1939. F.2/38 (yes, 38) called for a four cannon nose turret capable of firing in a limited arc, but considerable angles of depression, really another re-incarnation, this time of the Novel Fighter concept. Before anything got done someone suggested that the upper turret of the B.1/39 specification (the Ideal Bomber) might work with this aircraft in place of the nose turret. A turret first proposed for a fighter (F.18/36 and F.11/37) but then specified for a bomber (B.1/39) was now proposed for yet another turret fighter (F.2/38). Are you with me so far? This turret fighter project, previously F.2/38 was redesignated F.26/39.
To sum up, in efforts to develop a cannon armed turret fighter the Air Ministry issued all the specifications above. Not one of them led to a completed turret fighter. The Defiant, machine gun armed, was the only one to reach the RAF.
Cheers
Steve

Perhaps I am being too hard on the British.
The Americans certainly poured a crap load of money into the rocket armed bomber interceptors in the early 1950s with little results in actual tests. Fortunately the guided missile (poor as the early ones were) was able to take over from the unguided rockets.

Both countries seemed to have jumped the gun on what was technically possible or assumed that the engineers could develop the hardware fast enough to bring the theory into service fairly quickly.

However I still can't understand the guys who thought they could build turrets will multiple cannon (or even multiple turrets) without huge penalties in weight and drag. That is simple physics or mechanics, ship designers since before WW I figured the weight of a gun and it's mounting went up with the cube of of it's caliber (not including armor) I don't know why an aircraft turret should be much different in early estimates.

Dowding may have been going by hunch or gut feeling but he was closer to reality than the guys pushing this theory.

I don't know whether anything other than mock ups of these turrets were built in the period from 1936-1939. I don't think they were. One things for sure, the entire concept of turret fighters died in 1940, though the cannon turret itself didn't.

To be fair to Dowding, he was also one of those expressing reservations about the entire turret fighter concept long before they were revealed, as early as 1933, when the idea was gaining momentum through the 'Novel Fighter' competition and Ellington's own preference for some kind of turret armed fighter to engage bomber formations.

Cheers

Steve

All this tlk of canon armed turret fighters while the bombers carried turrets with rifle caliber guns throughout the war.

The Brits weren't the only ones.

pbehn said:

All this tlk of canon armed turret fighters while the bombers carried turrets with rifle caliber guns throughout the war.

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The British were looking for ways to increase the firepower of their fighters in the mid 1930s which is why all the fixed gun fighters got many machine guns and/or cannon armament. The logical up-gunning of a turret fighter was to use cannon, you can only fit so many machine guns in a turret and two cannon give much more 'horsepower' (to use an Americanism) than four machine guns.

British bomber armament was also much discussed, the balance between defensive armament, weight and speed being the principle debate. When Ellington saw the heavy bomber requirement (B.12/36) he asked for 20mm cannon armament to be considered, the Air Staff decided against it. One year later the Deputy Director Operational Requirements (DDOR), Oxland, who had argued against 20mm cannon for B.12/36 was advising the Plans branch of the Air Staff that bombers in the near future would require 37- 40mm cannon armament. This was something of a volte-face, but Oxland seems to have got away with it. This requirement was confirmed in a review of bomber armament in June 1938.
The 'Ideal Bomber' would have had cannon armament had it ever got built and had a suitable turret been developed (big ifs). The switch to night time bombing rendered almost all previous planning irrelevant. Though the prospect of a return to day bombing was always acknowledged it didn't happen until the opposition had been effectively destroyed, by the Americans. The RAF's war time bombers retained their machine guns throughout.

Cheers

Steve

I found the cutaways of the.50 bullets I mentioned earlier.

This not all of the different .50 cal bullets used during WW II/Korea but one can certainly see the difference in the amount of incendiary material carried by the M23 and how it was done. One can also see why they might have problems with it as there is very little wall thickness to either support the projectile on firing or insulate the incendiary material from the hot barrel.
Flaw in the jacket or steel cup? Rough spot in the bore? Barrel is hot from a long burst? Incendiary material ins't 100% on spec?
Combination of the above?

Great find Shortround. This has been a mystery for a very long time. I couldn't discount dad, Henry Brown and others recount of flawed "HEI" 50 cal bursting shortly after leaving the barrel. Thanks for digging.

I would say that the M23 is the most likely answer. It was known to act like you describe, it was in Europe at the time in small amounts.
I have not read about any true HE .50 cal projectiles but that doesn't mean they didn't exist, just rarer than the M23.
I have no idea if the M23 was even called the M23 in 1944/45 or went by a different designation like XM____ or T__E_ or something.
What the armorer's or weapons officers told your father and his squadron mates I obviously have no idea either. ALL possible points of confusion.
The M23 carried roughly double the amount of chemical payload that the German/Italian/Japanese HE or HEI 12.7-13mm projectiles did so having them "light up" just in front of the gun muzzles was probably a "significant event" for the pilots involved.