1941 Article on Intermediate Caliber Aircraft Cannon

[MIflyer]

By the way I recently read that the Spifire V's that first flew from the USS Wasp to Mata were equipped with both four 20MM cannon and four .303 machine guns.

 

[David Fred]

By the way I recently read that the Spifire V's that first flew from the USS Wasp to Mata were equipped with both four 20MM cannon and four .303 machine guns.View attachment 496783 View attachment 496784 View attachment 496785 View attachment 496786

I have this excellent book, and no Mk V versions were listed that way.

Some also had 2 x 20mm and 2 x Browning M2 .50.

2 x 20mm and 4x .303 included the Mk Vb, Mk Vc, Mk Vc (tropicalised), Mk IX (early), LF Mk I ("C" Wing), Mark VIII, and the Mark XII.

2 x 20mm and 2 x .50 Browning II both had "E" wings, the Mk IXe and Mk XIVe.

I can find British fighters with 4 x 20mm ( Tempest for one), but none also carried RCMGs.

 

[David Fred]

By the way I recently read that the Spifire V's that first flew from the USS Wasp to Mata were equipped with both four 20MM cannon and four .303 machine guns.View attachment 496783 View attachment 496784 View attachment 496785 View attachment 496786

More data I found today.

"As mentioned before, the Malta Spitfires were of the Mk. VC variant, then freshly off the production line and armed with hard-hitting four 20 cannon. However, cannon ammunition was always in short supply and most aircraft had two of the cannon removed to save on ammunition and weight.

Compared with the first Spitfires Mk. V these aircraft featured a number of refinements. A new SU injector-carburettor increased the top speed by 5-10 mph depending on altitude. Internally-mounted windscreen armour gained around 5 mph, streamlined rear-view mirror another 2-3 mph. Modified exhaust pipes brought another 6-7 mph, and a slightly improved propeller another 5 mph. Thus, despite the presence of the large Vokes tropical filter under the nose which cut the top speed by 15-20 mph, the Spitfire Mk. VC could hold its own against the German Messerschmitt Bf 109F and the Italian Macchi C. 202 fairly well. The Bf 109F was the fastest of the three, and was also superior in climb. However, the Spitfire was the most manoeuvrable of the trio and despite the reduction to two cannon had the heaviest armament. Combat victories over Malta were therefore highly dependent on pilot skills, element of surprise and efficiency of ground control."

From: 1942: Defence of Malta — Spitfire in Service | 1942 | history | Spitfire Mk. V

 

[MIflyer]

Well, the pictures of the Spit V's launching off the carriers show 4 X 20MM. And the pilots write of firing both 20MM and machine guns. Upon arrival in Malta they were astonished to have the ground crew open up the ammo bays and take out everything from toothpaste to wrenches. I find it very believable that the were sent with both 4X 20MM and 4 X .303 guns as a way to get spares to the island, even though that was not a standard fit. Your source indicates that they were "special" airplanes. By the way, the new carb would have helped with the Merlin's tendency to cut out under negative G as well.

The Vb spits could only have 2X 20MM and 4X .303. The Vc Spits could have 2 or 4 X 20MM and/or 4X .303

2 X 20MM plus two .50 cal indicates an E wing and the Spit V's did not have those.

 

[David Fred]

Well, the pictures of the Spit V's launching off the carriers show 4 X 20MM. And the pilots write of firing both 20MM and machine guns. Upon arrival in Malta they were astonished to have the ground crew open up the ammo bays and take out everything from toothpaste to wrenches. I find it very believable that the were sent with both 4X 20MM and 4 X .303 guns as a way to get spares to the island, even though that was not a standard fit. Your source indicates that they were "special" airplanes. By the way, the new carb would have helped with the Merlin's tendency to cut out under negative G as well.

The Vb spits could only have 2X 20MM and 4X .303. The Vc Spits could have 2 or 4 X 20MM and/or 4X .303

2 X 20MM plus two .50 cal indicates an E wing and the Spit V's did not have those.

Well, I have a Vb and a IIa here for comparison, and I dont' know where you would mount two more 20mm, especially with wings stuffed with goodies. And I am fairly familiar with the wing types, the "e" became the "universal wing" in 1944, and could be adapted. The "c" was the clipped version for better roll at lower altitude.
In fact, the Wikipedia article on the Wasp delivery was Vc versions, with "improvements to streamlining."

Operation Bowery - Wikipedia

"USS Wasp returned to Glasgow on 29 April 1942, where she loaded 47 Spitfires Mk Vc at King George V dock at Shieldhall.[1][note 1] " ,
Guven the smaller wing, it seems even harder to shoehorn in 2 more Hispanos, particularly if they were ad hoc cargo storage.

 

[David Fred]

Well, I have a Vb and a IIa here for comparison, and I dont' know where you would mount two more 20mm, especially with wings stuffed with goodies. And I am fairly familiar with the wing types, the "e" became the "universal wing" in 1944, and could be adapted. The "c" was the clipped version for better roll at lower altitude.
In fact, the Wikipedia article on the Wasp delivery was Vc versions, with "improvements to streamlining."

Operation Bowery - Wikipedia

"USS Wasp returned to Glasgow on 29 April 1942, where she loaded 47 Spitfires Mk Vc at King George V dock at Shieldhall.[1][note 1] " ,
Guven the smaller wing, it seems even harder to shoehorn in 2 more Hispanos, particularly if they were ad hoc cargo storage.

I do have one more source to check, a rather nerdy, obscure book.

 

[David Fred]

View attachment 497672


I do have one more source to check, a rather nerdy, obscure book.

Ah, it might have been the tropicalised Vc, didn't need the clipped wings as the hot air was thinner. Still not much room.

 

[David Fred]

View attachment 497673


Ah, it might have been the tropicalised Vc, didn't need the clipped wings as the hot air was thinner. Still not much room.

Okay!!! On page 102 of Flying Guns Of WW2, it mentions that when the V c received a new Merlin, 4 20 mm cannons were tried for a brief time, but the idea was quickly discarded because the extra weight completely offset the speed invreas the new Merlin offered, and was quickly discarded and never went into production.

 

[KiwiBiggles]

View attachment 497640

I have this excellent book, and no Mk V versions were listed that way.

Some also had 2 x 20mm and 2 x Browning M2 .50.

2 x 20mm and 4x .303 included the Mk Vb, Mk Vc, Mk Vc (tropicalised), Mk IX (early), LF Mk I ("C" Wing), Mark VIII, and the Mark XII.

2 x 20mm and 2 x .50 Browning II both had "E" wings, the Mk IXe and Mk XIVe.

I can find British fighters with 4 x 20mm ( Tempest for one), but none also carried RCMGs.

From Concise Guide To Spitfire Wing Types — Variants & Technology | Reference

"Initial production Spitfires Mk. Vc, such as those which were transported to Malta were factory-fitted with four cannon. In field conditions, it was often sufficient with two cannon armament and many of the four-cannon Spitfires were converted to fly with either outboard or inboard pair of Hispanos, or else converted to B-standard armament. Later on, production aircraft carried the two 20mm Hispanos and four Brownings."

So it would appear that the C wing, as originally fitted to the first Mk.VC production, carried four cannon and four machine guns. The C wing always retained this capability, but for most of the production it was fitted as for the B wing, with two cannons and four machine guns.

 

[MIflyer]

Well, I believe what the Mata Spitfire pilot wrote. He specifically said the airplanes off the USS Wasp were extra heavily armed with 4 X 20MM and 4 X .303. And he said they flew and fought with 20MM and machine guns. It is logical that the removed two of the 20MM and used them as spares. Their supply situation was incredibly desperate.

Now, he also complained that the guns were not harmonized. I can only assume that they knew the people on Malta were going to remove what they wanted so they did not bother. Still, you would have thought they would have harmonized at least the two 20MM and the four .303. I guess that if the airplanes were specially equipped the usual production and checkout process was not followed.

The Egyptian depot at Aboquir developed a tropical filter that was much smaller and had reduced performance loss. The air intake for the Merlin was at the back of the engine with the usual airscoop designed to minimize ram pressure loss (or at least after Stanley Hooker redesigned it). The tropical filter developed in England took the air in just behind the prop and routed it all the way back to the carb intake.

The maintenance crews on Malta worked wonders putting Spitfires back together. Sadly the author related how they got new Beaufighters in and one of them fell out of the air one day, killing the maintenance chief and a number of his crew.

I've read quite a bit about personal experiences on Malta lately. It seems to have been about three orders of magnitude worse than the Battle of Brittan.

 

[MIflyer]

From the latest issue of Flight Journal here a a couple of items that address the use of .50 cal guns to replace the .303 guns in Spitfires.


According to the article, the driver was the use of Spitfires as fighter bomber aircraft with the 2nd TAS to support the Normandy invasion and advance into Europe.
The article mentions that even carrying only a single 500 lb bomb a Spitfire's combat radius was a mere 95 miles.

 

[David Fred]

From Concise Guide To Spitfire Wing Types — Variants & Technology | Reference

"Initial production Spitfires Mk. Vc, such as those which were transported to Malta were factory-fitted with four cannon. In field conditions, it was often sufficient with two cannon armament and many of the four-cannon Spitfires were converted to fly with either outboard or inboard pair of Hispanos, or else converted to B-standard armament. Later on, production aircraft carried the two 20mm Hispanos and four Brownings."

So it would appear that the C wing, as originally fitted to the first Mk.VC production, carried four cannon and four machine guns. The C wing always retained this capability, but for most of the production it was fitted as for the B wing, with two cannons and four machine guns.

Spitfire – History of the Spitfire's design and development | Military History Monthly

 

[MIflyer]

Okay, there is nothing new there, so the Spit Vc's sent to Malta were specially equipped with 4 X 20MM and 4X.303 machine guns, just as they were specially equipped in those other areas you mentioned.

Once there, it seems that they removed one of the 20MM guns from each wing, but kept the four .2303 guns, although according to the Profile, Spit Vcs with 4 X 20MM guns were indeed later used in Italy. Also according to the Profile, American squadrons in the Med equipped with the Spit V sometimes removed one .303 gun from each wing to improve maneuverability.