improving the 109??

[stona]

I believe that the wing planform was to accommodate the gun installation. Not for beauty and not for the turn rate.

Right on the other two but not this. The wing was designed without compromise to achieve the best balance between speed and manoeuverability. The latter property reversed the trend for outright speed, sacrificing manoeuverability, which had developed with monoplane fighters.
Beverly Shenstone himself explained that the wing planform was at an advance design stage before the eight gun requirement was introduced.

"Specification F.37/34 had called for a four gun fighter, like its predecessor. But when work was well advanced the RAF changed its mind and asked if we could fit eight guns. After a bit of a struggle we managed to squeeze all eight into our thin wing, with just a hint of a bulge over the two outer weapons. The rather uneven spacing of the guns was because the Spitfire was originally designed for only four guns and only when it was in an advanced stage were eight guns decided upon. Had it not been for this, the installation would have been neater."

Shenstone's recollections are supported by other evidence. On April 26th 1935 Sorley went to Supermarine's Woolston factory to see the nearly completed mock up of what would become the Spitfire. Mitchell had received the Air Staff's requirements for a day/night fighter to Specification F.10/35 the previous day and discussed the requirements with Sorley, particularly the armament which was,

"not less than six guns,but eight guns are desirable. These to be located outside the airscrew disc. Reloading in the air is not required."

Mitchell assured Sorley that the extra armament could be accomodated, but that the bomb load would have to be deleted and fuel capacity reduced to save weight.Sorley was delighted and the Spitfire got eight guns.

Cheers

Steve

 

[wuzak]

The wing was designed without compromise to achieve the best balance between speed and manoeuverability. The latter property reversed the trend for outright speed, sacrificing manoeuverability, which had developed with monoplane fighters.

The balance between the speed and manoeuvrability, not optimised for the latter as suggested by A.N. Other earlier and to which I was responding.

The could have made the Spitfire even more manoeuvrable, but at the coots of speed. So they weren't truly following WWI fighter traits/goals.

 

[stona]

The balance between the speed and manoeuvrability, not optimised for the latter as suggested by A.N. Other earlier and to which I was responding.

The could have made the Spitfire even more manoeuvrable, but at the coots of speed. So they weren't truly following WWI fighter traits/goals.

Yes!
Both were important attributes in a fighter, again contradicting AN Other They still are.

Take a look at the performance aspects of the Bf 109 F that Bader was interested in knowing. I posted his letter earlier in the thread. I would respectfully suggest that Bader was much better qualified than AN Other to know which ones were important.

Cheers

Steve

 

[pbehn]

"not less than six guns,but eight guns are desirable. These to be located outside the airscrew disc. Reloading in the air is not required."

A wise decision, I think reloading six guns in the air would have caused problems for less experienced pilots.

 

[stona]

A wise decision, I think reloading six guns in the air would have caused problems for less experienced pilots.

Yes indeed, or any pilot! The guns being outside the airscrew disc, on a monoplane fighter, means that the guns are out in the wings

Cheers

Steve

 

[stona]

& technically, is a hub cannon not 'outside' the prop-disc?

I don't think in any definition the centre of a disc is considered outside it. It was certainly not what the Operational Requirements Committee would consider outside the propeller disc. It certainly thought in terms of the traditional British fuselage mounted weapons.
I can't think of any British WW2 design with a weapon firing through the spinner...though someone will probably come up with some obscure prototype to prove me wrong
Cheers
Steve

 

[stona]

But "inside" the prop-disc surely implies the needful provision of interrupter gear.

Steve, do you know why the Mustang Mk III was deemed to be 'lightly armed' by the RAF,
but not retro-fitted with the standard H-S 20mm cannon fit, that earlier Brit Mustangs had?

I think that the position 'outside the airscrew disc' was stipulated to avoid the need for interrupter gear, so you make a valid point, but I don't think that a weapon firing through the spinner would have been considered as there was no precedent for it. The Germans had trouble getting it to work.

I didn't know that the RAF deemed the Mustang III lightly armed, though four .50 calibre machine guns certainly isn't heavy armament, so I can't answer that question.

Cheers

Steve

 

[Peter Gunn]

*SNIP*

( & some people even give their bikes & cars pet names!),

*SNIP*

I used to call my '65 G.T.O. a "Goat" does that count? Well, myself and the rest of the automotive world anyway.

 

[pbehn]

Hispano via French/Russians got a moteur-cannon working before the Germans, Steve?

Part 23 of the Mustang III tactical trials described the 4 X 0.5" armament as:

"This is very little compared to the Spitfire."

So it would have to be officially... 'Piss-poor compared to 4 X 20mm'..

Some mustang mk Is were fitted with 4 cannon

The Mustang I carried a mixed armament of eight machine guns. Two .50 inch machine guns were mounted under the engine cowling, firing through the propellers. Each wing contained two .30 inch machine guns and one .50 inch machine gun, arranged with the bigger gun between and below the two .30s. Ninety three USAAF P-51 Mustangs were given to the RAF. These carried four 20mm cannon and were designated as Mustang IAs.

 

[Peter Gunn]

Grabbed this from the P-40 BoB thread:

"There is a remarkably restrained letter from the officer commanding No. 19 Squadron, Squadron Leader R Pinkham, following his squadron's unsuccessful attempt to employ two 20mm cannons in their Spitfires. On 16th August the cannon had functioned properly on just one of the seven Spitfires engaged, on the 19th it was none out of three, on the 24th two out of eight and on the 31st just three out of six.

Pinkham wrote:

"In all the engagements so far occurring it is considered that had the unit been equipped with eight gun fighters it would have inflicted far more severe losses on the enemy... It is most strongly urged that until the stoppages at present experienced have been eliminated this Squadron should be re-equipped with Browning gun Spitfires. It is suggested that a way of doing this would be to allot the current cannon armed Spitfires to an Operational Training Unit, and withdraw Browning gun Spitfires from there for use in this Squadron."

On 4th September the exchange was made. The aircraft received from the OTU (Haywarden) were not exactly pristine. The 19 Squadron diary noted:

" First day with the eight gun machines, and what wrecks. At least the guns will fire."

Armament that doesn't work is, quite literally, worse than useless.

Cheers

Steve"

Steve, et al.,
Any data on how the Mustang Mk Ia cannons worked? Better, worse or was the issue the Spits in the letter were having fixed by the time the Mustangs arrived? I always thought personally the Mustang should have kept the 4x20mm armament but am interested to see data to back that opinion up.

Thanks.
Pete

 

[pbehn]

Grabbed this from the P-40 BoB thread:


Steve, et al.,
Any data on how the Mustang Mk Ia cannons worked? Better, worse or was the issue the Spits in the letter were having fixed by the time the Mustangs arrived? I always thought personally the Mustang should have kept the 4x20mm armament but am interested to see data to back that opinion up.

Thanks.
Pete

The quote was from the Battle of Britain, the cannons were fitted in a hurry and suffered because of it, the problems were eventually solved.

The response was to fit the Spitfire with the 20mm Hispano cannon. This poses a variety of problems, not least of which was the size of the cannon. The only way to fit it in the Spitfire wing was to mount it on its side. A second problem was that the early cannons were prone to jam under the pressure of combat. If one cannon jammed, the recoil from the other one was enough to push the Spitfire off course.



The "b" wing entered service during 1940. No.19 Squadron used it during the battle of Britain, but the cannons were still causing problems. Finally in November 1940 No.92 Squadron was given Spitfires equipped with two 20mm cannon and four 0.303in machine guns. This proved to be a much more effective combination of weapons, and became the standard for the "b" wing.

"c" wing


Spitfire F.Mk IX with "c" wing
The "c" wing appeared in October 1941. It was a "universal" wing that could take eight .303in machine guns, four 20mm cannon or two 20mm cannon and four machine guns. Each cannon now had 120 rounds, compared to the 60 of the "b" wing. This wing was used on the majority of Mk V Spitfires, normally with the combined cannon and machine guns configuration. The "c" wing also had the capability to carry two 250lb bombs under the wings, or one 500lb bomb under the fuselage. If machine guns were used, they were used in the outboard position. The "a" and "b" wings were not used after the Spitfire V.

 

[wuzak]

Any data on how the Mustang Mk Ia cannons worked? Better, worse or was the issue the Spits in the letter were having fixed by the time the Mustangs arrived? I always thought personally the Mustang should have kept the 4x20mm armament but am interested to see data to back that opinion up.

I suspect that the Hispanos had been worked out by then. The Mustang Ia came along almost 2 years after the Spitfires that had the issues Pinkham described.

 

[pbehn]

I suspect that the Hispanos had been worked out by then. The Mustang Ia came along almost 2 years after the Spitfires that had the issues Pinkham described.

It was solved fairly quickly, one of the "heat of battle" events which resulted in a squadron of fighters being sent out with practically no guns that worked, I read elsewhere that the cannons needed to be warmed by hot air ducts which was hard to arrange for the out board cannon so the compromise of 1 cannon and 2 MGs became the standard.

 

[Airframes]

The problems with the cannons on the 19 Sqn Spitfires in 1940 were due to mainly three areas.
As has been mentioned, in order to fit into the wing, the weapons had to be mounted on their side. These earlier weapons were drum fed, from a 60 round drum magazine, which fed in from the side of the receiver, hence the 'blister' on the top surface of the wing, covering the drum magazine, and the magazine and feed were the primary cause of problems, due mainly to the side mounting arrangement.
Apart from problems with freezing, which caused stoppages, or more correctly, prevented the weapon(s) from firing at all, the main problem was stoppages, after one or two rounds had been fired, when the aircraft was under 'g' loading.
Although the weapons could, and would fire when the aircraft was level and stable, when manouvering, the 'g' loads caused an imbalance in the feed, where the nose of the round struck the edge of the breech face. As the bolt continued forward, with the nose of the round jammed hard against the breech rim, the cartridge case/round then bent, totally jamming the breech and bolt, and thereby preventing any further use of the weapon until it had been stripped on the ground.
This was eventually partly cured by modifying the feed system and drum spring, but wasn't fully overcome until the introduction of the MkII Hispano with belt feed via a BFM (Belt Feed Mechanism), which resembled the drum magazine in shape, although smaller, and with the ammunition belts stored in 'box' magazines in the wing, outboard of the gun.

As has been mentioned, by the time the Mustang Mk1a entered service, the Spitfire MkIX was already in service, with belt-fed cannon and mg armament. Note also that the Mustang Mk1a was allocated to tactical recce squadrons, as well as Army cooperation squadrons, whose operational environment was somewhat different to that of the true fighter squadrons, with most sorties being at medium to low level, where the majority of engagements were against ground targets - a rather more 'stable' situation for the operation of the cannons, compared to aerial engagements.

 

[Peter Gunn]

Many thanks gentlemen.

 

[wuzak]

Did the Mustang Ia have American built Hispanos, which had their own set of issues, or British built Hispanos?

 

[GregP]

Ours used SAE cartridges and the British used Whitworth cartridges!

 

[GrauGeist]

Did the Mustang Ia have American built Hispanos, which had their own set of issues, or British built Hispanos?

The ones in British service were the Hispano Mk.II

 

[Shortround6]

Ours used SAE cartridges and the British used Whitworth cartridges!

Yep, and getting American guns to fire British shells was real Bitc*!!!!

 

[Shortround6]

More seriously, I have read that the British never used an American made Hispano in an aircraft, some may have been used as AA guns. Source could be wrong.