Spitfire IX Armament

[joeblogs]

I'm late to all this discussion but it sure seems to me that weight gain has a more significant effect on vertical performance than it does sustained turning and the early to mid war Spitfires were always trying to catch up with the Germans in terms of vertical performance.

In the pacific during 1942, USN pilots preferred the F4f-3 to the F4f-4s. Why? The -3s had four Brownings with more rounds per gun. The -4's had 6 Brownings (a spec change to satisfy a British order) and fewer rounds per gun. Weight went up and climb rate suffered. Turn rate suffered too, but the pilots mostly complained about the loss of vertical perfomance against an enemy plane that was superior in both the vertical and horizontal.

Another issue - could it be Center of Gravity?

-Blogs

Originally posted by Guppy35
Cobra,

The photo of the three Spits you refer to are two Spit 21s and a Spit 22 with the bubble canopy.  The Spit 21 saw very limited action with 91 Squadron just before the end of the war.  The 22 didn't see WW2 service.  The 21,22,24 had a completely different wing design and were Spits in name only.

They DID NOT use the 4 cannon wing with the IX in any numbers or total squadron service.  The ONLY squadron I can definately say used 4 Cannon Spit Vcs in squadron strength is 2 Squadron SAAF late in the war as an air to ground support aircraft in Italy.

The weight gain was far more detrimental in an A to A environment then the extra set of cannon was worth.  As I said earlier a number of pilots got rid of their 303s and relied totally on the 2 cannon as they figured if they couldn't hit with the cannon the 303s were pointless.  The loss of that weight improved speed and turning ability in the pilot's eyes.

Trust me I love Spits but there is no reason to push for a 4 cannon Spit.  A clipped wing, late war LFIXE or LFXVIE yes, but not 4 cannons

Dan/Slack

[Guppy35]

No question on the climb rate.  One of the specific comments on the Malta Vcs with 4 cannons was the impact on the climb rate.  As mentioned they removed two of the 4 cannons for performance reasons including helping with climb rate.

Dan/Slack

[HoHun]

Hi Dan,

>Clearly over time, the medium alt escorted bombers must have proved to be the best way to get the LW into the air as by 43 thats all they were doing based on the logbooks I've seen.

Very interesting!

It's all the more remarkable because the USAAF bombers which had superior high-altitude performance thanks to their turbo superchargers stuck to medium altitudes as well. I guess oxygen (and accordingly operational safety) was behind that.

Speaking about using bombers to get the enemy fighters into the air, I'm just reading about the role of Ultra in the Battle of Britain.

Apparently, Leigh-Mallory was pushing to go after the Luftwaffe in force just when Göring had told his squadrons that this was just what he wanted the RAF to do. Dowding and Park were cleared for Ultra and had Göring's orders on their desks, but Leigh-Mallory didn't get Ultra intelligence, and so they weren't allowed tell him what they knew!

Regards,

Henning (HoHun)

[Karnak]

Isegrim,

FYI, the USA had two Spitfire Mk IXs (MK210 and MK317) that they had worked up a scheme to increase the Spitfire's  range.

"In these the internal fuel capacity had been increased by fitting a 43 gallon tank in the fuselage behind the pilot's seat and two leading edge tanks, each of 16 1/2 gals.  Additional fuel was carried externally in two P-51 Mustang drop tanks, each of 62 gals capacity and suspended under the wings on P-51 bomb racks,  With all this fuel the Spitfires weighed 10,150lbs and the undercarriage was fully compressed.  Also, oil tank capacity had to be increased to 20 gals.  The still air range of the modified Spitfires was approximately 1,600 miles while the Vickers scheme was about 1,400, but the latter could be extended to 1,650 miles by an increase in internal capacity.  The American modified Spitfire handled better than the Vickers and was safer for reinforcing."


Now, that was a Spitfire Mk IX weighing in at 10,150lbs and the landing gear did not collapse.  The shocks were fully compressed, but that is hardly surprising given the Spitfire Mk IX's designed maximum load and could have been remedied by heavier duty shocks.


The Spitfire did not have either weak landing gear nor weak wings.

[Charge]

"One of the specific comments on the Malta Vcs with 4 cannons was the impact on the climb rate. As mentioned they removed two of the 4 cannons for performance reasons including helping with climb rate. " AFAIK this was also the case with Hurricane 2Cs' based on Malta. The Hurris 2 cannon armament was considered adequate and the less weight of removing 2 cannons allowed them to intercept enemies more readily as the aircontrol at Malta was not too good.

About Spitfire's wing: To my understanding the main spar of the Spitfire was a spring-like square tube with smaller tubes inside another and thus very durable as was necessary because of the huge forces it had to endure owing to weight and big wing area. However, I'm not sure if the wing design itself was very rigid because of the wing area vs. thinness.
The wing could propably very well carry the weight of the four guns but maybe the flexing of the wing while firing was too much? (The hispano was not a very heavy cannon when considering its huge muzzle energy so the energy has to go somewhere.)

Just an idea...

[Guppy35]

Originally posted by Charge
"One of the specific comments on the Malta Vcs with 4 cannons was the impact on the climb rate. As mentioned they removed two of the 4 cannons for performance reasons including helping with climb rate. " AFAIK this was also the case with Hurricane 2Cs' based on Malta. The Hurris 2 cannon armament was considered adequate and the less weight of removing 2 cannons allowed them to intercept enemies more readily as the aircontrol at Malta was not too good.

About Spitfire's wing: To my understanding the main spar of the Spitfire was a spring-like square tube with smaller tubes inside another and thus very durable as was necessary because of the huge forces it had to endure owing to weight and big wing area. However, I'm not sure if the wing design itself was very rigid because of the wing area vs. thinness.
The wing could propably very well carry the weight of the four guns but maybe the flexing of the wing while firing was too much? (The hispano was not a very heavy cannon when considering its huge muzzle energy so the energy has to go somewhere.)

Just an idea...

The C or Universal Wing was redesigned internally specifically to have the option to carry the 4 cannon.  It was strengthened for that.

Two diagrams from Spit manuals.  First is the C or Universal wing as MH434 and others had it with only one cannon and no second cannon bay opening and plug.  Note the outlined second cannon bay and ammo bay.

Second is of the installation in the C or Universal wing of the 2 cannon set up with out machine guns.

Dan/Slack

[joeblogs]

I'm a bit confused here.

It was my impression that US daylight raids were conducted at reletively high altitudes (25k & up) and British night raids were closer to 15k. The B-17 had no problem with 30k + altitudes but the ceiling on the B24 was lower. Of course bomb acuracy would suffer at higher altitudes.

-Blogs

Originally posted by HoHun
Hi Dan,

>Clearly over time, the medium alt escorted bombers must have proved to be the best way to get the LW into the air as by 43 thats all they were doing based on the logbooks I've seen.

Very interesting!

It's all the more remarkable because the USAAF bombers which had superior high-altitude performance thanks to their turbo superchargers stuck to medium altitudes as well. I guess oxygen (and accordingly operational safety) was behind that.

Speaking about using bombers to get the enemy fighters into the air, I'm just reading about the role of Ultra in the Battle of Britain.

Apparently, Leigh-Mallory was pushing to go after the Luftwaffe in force just when Göring had told his squadrons that this was just what he wanted the RAF to do. Dowding and Park were cleared for Ultra and had Göring's orders on their desks, but Leigh-Mallory didn't get Ultra intelligence, and so they weren't allowed tell him what they knew!

Regards,

Henning (HoHun)

[Guppy35]

Originally posted by joeblogs
I'm a bit confused here.

It was my impression that US daylight raids were conducted at reletively high altitudes (25k & up) and British night raids were closer to 15k. The B-17 had no problem with 30k + altitudes but the ceiling on the B24 was lower. Of course bomb acuracy would suffer at higher altitudes.

-Blogs

Both the RAF and USAAF had medium bombers that were flying raids into France from 41 on.  Spitfires were the primary escorts of these raids as they did have the range to take them to targets in France and back.  These raids were flown at medium alts in the 15-25K range as it was the best operating altitudes of the medium bombers.

We were not talking about heavy bomber raids to Germany as those were flown at different alts

As you can probably tell I like visuals too  

Scan is of the logbook of a Spit XII pilot that I have from September 43 showing all the escorts they were flying.

Dan/Slack

[Guppy35]

The answer it turns out was quite simple as to why we don't see Spit IXs with 4 cannon.

Quoting Jeffrey Quill, Cheif Supermarine Test pilot(A primary source I'd argue):

"Although the Universal (C) wing had provision for four cannon, it was normally possible to fit only two, because heating for the outboard cannon was inadequate.  Only some squadrons operating overseas in low level roles ever operated with four cannon fitted"


That explains 4 cannon VIII in Australia and 4 cannon Spit Vc in the Med does it not?

Heating, not weight was the issue

Dan/Slack

[MiloMorai]

Originally posted by Guppy35
The answer it turns out was quite simple as to why we don't see Spit IXs with 4 cannon.

Quoting Jeffrey Quill, Cheif Supermarine Test pilot(A primary source I'd argue):

"Although the Universal (C) wing had provision for four cannon, it was normally possible to fit only two, because heating for the outboard cannon was inadequate.  Only some squadrons operating overseas in low level roles ever operated with four cannon fitted"


That explains 4 cannon VIII in Australia and 4 cannon Spit Vc in the Med does it not?

Heating, not weight was the issue

Dan/Slack

A much more reasonable reason for the  2 cannon Spits over the truly lame 'weak u/c' reason given by another.

[Angus]

"Isengrim:
Can you carry a 30 lbs backpack in every hour on EVERY single day without your back starting to look like Quasimodo`s after a year or two? "

Try being 30 lbs too fat, - not a lot really ....weakling:D
Better still, try being a farmer for a year, hehe

[Charge]

Guppy:"because heating for the outboard cannon was inadequate"

But what is the inboard "stub" seen on 2 cannon Spit. I thought it was the outboard cannons that where fitted and the inboard ones deleted?

Where was the 50Cal fitted? Was it in the innermost MG bay or next to the 20mm(and inner or outer bay)?

-C+

[Guppy35]

Originally posted by Charge
Guppy:"because heating for the outboard cannon was inadequate"

But what is the inboard "stub" seen on 2 cannon Spit. I thought it was the outboard cannons that where fitted and the inboard ones deleted?

Where was the 50Cal fitted? Was it in the innermost MG bay or next to the 20mm(and inner or outer bay)?

-C+

That was the redesigned "E" Wing that had the cannon outboard and the 50 cal inboard.  This didn't appear until mid 44.  It still didn't carry two 20mm cannon however.  The point being that heating for one cannon was adequate but not for two.  

With the two 303 MGs on the Universal wing, they decided to have the 20mm cannon in the inboard bay.

They didn't solve the heating problems for the two 20mm cannons until the completely redesigned Spitfire 21.

Dan/Slack

[HoHun]

Hi Guppy,

>It still didn't carry two 20mm cannon however.  The point being that heating for one cannon was adequate but not for two.  

As this makes it sound like it was a question of heating power, I'd like to point out that to me, it sounds more like a question of the hot air not getting to the outer cannon if an inner cannon was present.

That the issue wasn't solved in my opinion shows that it didn't have much priority. If hot air didn't suffice, there were always electrical heaters as used by the USN.

Either the added firepower wasn't considered worth the effort, or there were supplemental reasons not to use the cannon. Disturbance of the air flow over the wing might be one, for example.

It comes down to the Spitfire with 2 cannon being a better fighter overall than the Spitfire with 4 cannon, whatever the trade-offs were.

Regards,

Henning (HoHun)

[Guppy35]

Originally posted by HoHun
Hi Guppy,

>It still didn't carry two 20mm cannon however.  The point being that heating for one cannon was adequate but not for two.  

As this makes it sound like it was a question of heating power, I'd like to point out that to me, it sounds more like a question of the hot air not getting to the outer cannon if an inner cannon was present.

That the issue wasn't solved in my opinion shows that it didn't have much priority. If hot air didn't suffice, there were always electrical heaters as used by the USN.

Either the added firepower wasn't considered worth the effort, or there were supplemental reasons not to use the cannon. Disturbance of the air flow over the wing might be one, for example.

It comes down to the Spitfire with 2 cannon being a better fighter overall than the Spitfire with 4 cannon, whatever the trade-offs were.

Regards,

Henning (HoHun)

Clearly the need for 4 cannon was not pressing enough to change production at that point in the war.  But it was clear from many sources not in the least Jeffrey Quill that the Universal wing was meant to hold 4 cannon and did in limited low alt and tropical settings.

But because of the heating issue, the ducting for the cannon heating to the one cannon was routed through the empty second bay.  This is visible in the maint manuals for the Spit.

There is little doubt though that because the hitting power of the single cannon wing was sufficent that they didn't force the issue earlier and in fact settled on the E wing with the 20mm cannon and .5 machine gun as the best set up for the wartime Spit.  

As mentioned earlier the Spit 21 with a completly redesigned wing did see limited service at the end of the war with one squadron but not enough to make a difference as the IXe, XVIe and XIVe did in the 44-45 timeframe.

Bottom line though for this thread, is the wing could have carried twin cannon as it clearly was strong enough and designed for such a loadout despite certain Spit hater's belief that it was unable to because the undercarriage was too weak

Dan/Slack