Cowl mounted cannon on early war Spitfires and Hurricanes

Been reading through the '4 Engined German Bomber' thread and suddenly had me a thunk.

Was there a reason why the single seat, engine British fighters of WW2 didnt use cowl mounted guns / cannon with interupter gearing?

The trouble of mounting 20mm cannon into the thin winged Spitfire ment that the design had to soldier on with 8 .303 Brownings for longer than was desired.

Ive recently looked at other designs of the 1939 period and many of the in service Aircraft (including older british planes such as the Gladiator) mounted guns on the cowling or above the Engine etc.

Also IIRC there was problems with the guns icing up in the wings - having them closer to the engine might have helped resolve this.
 

Deleted member 1487

Been reading through the '4 Engined German Bomber' thread and suddenly had me a thunk.

Was there a reason why the single seat, engine British fighters of WW2 didnt use cowl mounted guns / cannon with interupter gearing?

The trouble of mounting 20mm cannon into the thin winged Spitfire ment that the design had to soldier on with 8 .303 Brownings for longer than was desired.

Ive recently looked at other designs of the 1939 period and many of the in service Aircraft (including older british planes such as the Gladiator) mounted guns on the cowling or above the Engine etc.

Also IIRC there was problems with the guns icing up in the wings - having them closer to the engine might have helped resolve this.

For one thing the variable burn in cannon shot is problematic for interrupter gear, which is why the Germans never did it. Also the early ones weren't belt fed, rather drum fed, which precluded cowling mounts.

The British tried to get wing mounted cannons for the SE fighters, but couldn't get them to stop jamming until August, but then couldn't get enough until nearly October:
http://en.wikipedia.org/wiki/Hispano-Suiza_HS.404#British_production

http://en.wikipedia.org/wiki/Supermarine_Spitfire#Armament
In June 1939, a single Spitfire was fitted with a single drum-fed Hispano in each wing, an installation that required large blisters on the wing to cover the 60-round drum. The cannon suffered frequent stoppages, mostly because the guns were mounted on their sides to fit as much of the magazine as possible within the wing. In January 1940, P/O George Proudman flew this prototype in combat, but the starboard gun stopped after firing a single round, while the port gun fired 30 rounds before seizing.[95] If one cannon seized, the recoil of the other threw the aircraft off aim. Nevertheless, 30 more cannon-armed Spitfires were ordered for operational trials, and they were soon known as the Mk IB, to distinguish them from the Browning-armed Mk IA, and were delivered to No. 19 Squadron beginning in June 1940. The Hispanos were found to be so unreliable that the squadron requested an exchange of its aircraft with the older Browning-armed aircraft of an operational training unit. By August, Supermarine had perfected a more reliable installation with an improved feed mechanism and four .303s in the outer wing panels. The modified fighters were then delivered to 19 Squadron.[95]

Getting quantity production in time wasn't really possible.
 
It was a pretty normal thing at that time to have an engine mounted cannon firing through the propeller spinner. Most famous of the bunch was the Bf109, but the Heinkel 100, Morane Saulnier MS406 and the Dewotine 520 all had the same thing.

Given that the Merlin was also a V-12 it shouldn't be beyond the wit of man to fit something similar to the Spitfire and Hurricane, although maybe someone else can give a technical rather than doctrinal reason for this being impossible.
 
Been reading through the '4 Engined German Bomber' thread and suddenly had me a thunk.

Was there a reason why the single seat, engine British fighters of WW2 didnt use cowl mounted guns / cannon with interupter gearing?

The trouble of mounting 20mm cannon into the thin winged Spitfire ment that the design had to soldier on with 8 .303 Brownings for longer than was desired.

Ive recently looked at other designs of the 1939 period and many of the in service Aircraft (including older british planes such as the Gladiator) mounted guns on the cowling or above the Engine etc.

Also IIRC there was problems with the guns icing up in the wings - having them closer to the engine might have helped resolve this.

Thanks for asking this; I'd always wondered why the Spit at least wasn't rigged for a motorkannone type mount - especially as there were firepower concerns about the .303 even then.
 
For one thing the variable burn in cannon shot is problematic for interrupter gear, which is why the Germans never did it. Also the early ones weren't belt fed, rather drum fed, which precluded cowling mounts.

The British tried to get wing mounted cannons for the SE fighters, but couldn't get them to stop jamming until August, but then couldn't get enough until nearly October:
http://en.wikipedia.org/wiki/Hispano-Suiza_HS.404#British_production

http://en.wikipedia.org/wiki/Supermarine_Spitfire#Armament


Getting quantity production in time wasn't really possible.

The Emil T2 had an Engine mounted gun

Only very limited numbers of the E-2 variant were built, for which the V20 prototype served as basis. It was armed with two wing mounted, and one engine mounted Motorkanone MG FF cannon, which gave considerable trouble in service, as well as two synchronized MG 17s cowl machine guns. In August 1940, II./JG 27 was operating this type

It was a pretty normal thing at that time to have an engine mounted cannon firing through the propeller spinner. Most famous of the bunch was the Bf109, but the Heinkel 100, Morane Saulnier MS406 and the Dewotine 520 all had the same thing.

Given that the Merlin was also a V-12 it shouldn't be beyond the wit of man to fit something similar to the Spitfire and Hurricane, although maybe someone else can give a technical rather than doctrinal reason for this being impossible.

This is exactly what I was thinking - in fact nearly every other Fighter plane in service in 1939 had guns firing through the Properllor
 
This is exactly what I was thinking - in fact nearly every other Fighter plane in service in 1939 had guns firing through the Properllor

I think we have to make a clear distinction between firing through the propeller arc with syncronisation gear (for example, the cowling mounted guns on the 109 or the wing root cannon on the Fw190) and firing through the spinner with a cannon mounted between the cylinder banks.

79470504.F40xpVRb.DSC_3735.jpg
 

Deleted member 1487

I misunderstood I though you meant just a cannons mounted on the fuselage, not also the motorkannone type mount. That might be doable, but it would take a lot of regiggering with the Merlin I'd think. A cowling mount is different than a 'through the engine mount'.

Oldironside is right that its a different animal to work out and took the Germans a while to get it right. Not sure if the Merlin could even be adapted to that. AFAIK the Spitfire never had one, so it might not have been an option:
img_0
 
It was a pretty normal thing at that time to have an engine mounted cannon firing through the propeller spinner. Most famous of the bunch was the Bf109, but the Heinkel 100, Morane Saulnier MS406 and the Dewotine 520 all had the same thing.

Given that the Merlin was also a V-12 it shouldn't be beyond the wit of man to fit something similar to the Spitfire and Hurricane, although maybe someone else can give a technical rather than doctrinal reason for this being impossible.

Thanks for asking this; I'd always wondered why the Spit at least wasn't rigged for a motorkannone type mount - especially as there were firepower concerns about the .303 even then.

Engine mounted guns work better with a inverted V engine. The cannon is lower and the gearbox drops the spinner down from the crank to the axis of the bore. A regular V12 would have the gun and spinner too high.
 
Voila. Un Merlin. There doesn't seem to be much space between the cylinder banks. Of course, the reduction gearbox which would be rejigged to move centre line of the propeller even higher, but I can't help thinking would ruin the Spitfire's looks.

merlin1%282%29.jpg
 

Saphroneth

Banned
Call me a fool, but what's to stop the RAF (in an advanced threat environment) paying for the license to the Hispano earlier, getting to work on it earlier, and working out the mounting problems earlier?
 

Deleted member 1487

Call me a fool, but what's to stop the RAF (in an advanced threat environment) paying for the license to the Hispano earlier, getting to work on it earlier, and working out the mounting problems earlier?
Realizing that their MGs are not sufficient. They thought they had enough already and testing finally made them realize otherwise. That was partly due to the later start to rearmament and realizing war was coming; France was even further behind than Britain in most ways. The Great Depression and not realizing Hitler's real intentions were the reason there wasn't more preparation earlier.
 
Call me a fool, but what's to stop the RAF (in an advanced threat environment) paying for the license to the Hispano earlier, getting to work on it earlier, and working out the mounting problems earlier?

Well, nothing as far as I can see. It would just take someone in officialdom to see what the French are doing (and were doing as far back as the first world war) and demand it for the new generation of Merlin powered fighters. It should be worth remembering that at the time the Spitfire was being planned, senior RAF officers like Robert Brooke-Popham were not only against 8 Brownings, but didn't really like enclosed cockpits.
 
Just to show it wasn't a new idea, here's George Guynemeyer with his Spad XII with a 37mm (sic) cannon firing through the centre of the propeller.
1310548008-spad01.jpg

And a diagram from the pilot's notes.

HighFlight-ReneFonck9.jpg
 
I don't see any reason an alt-RAF couldn't do it, even if only looking at experience in Spain.

And if you're only after an increase in firepower, what would you say to 4-6 12.7mm or 15mm in the cowl/cheeks? (Or is it getting crazily nose-heavy?:eek:)
 

Saphroneth

Banned
By mounting problems, I mean the wing-mounted Hs-404 (with the stronger spring when side-mounted) in place of the regular MGs.
OTL they actually had it ready to license, they just dithered on the money, as I recall - and without the money they didn't get the diagrams and didn't find the problem. The problem once known about is a fairly simple fix.

And in an increased threat environment, there's that option available - seeing as the thread relates partly to the "heavier LW bombers" dealio.
 
The Merlin engine was not designed to mount a motor-cannon because it would interfere with the optimum induction tract routing. It was a conscious decision for best engine performance versus the gun. It seems to have worked because the Merlin was 26 liters, and everything else was 33-35 liters or so. My humble opinion was that the decision was correct. Cowl guns were a matter of design. If you need 8 guns, putting 2 in the cowl means you use space occupied by the fuel tank on the Spitfire and Hurricane, so that doesn't work. It also means extra areas for the armorers to service. Pointless.
 
Okay so it seems that mounting Cowl guns would impinging upon the design to much and firing through the prop ala Motor-Kanon style is out due to the positioning of the Engine and fuel tank.

I wonder if the use of under wing 'Gondolas' was ever contemplated as a short term fix as sported by the later BF109s and S gun mounts on Hurricanes.

But it seems that the simplest answer was coughing up some dosh in a more timely fashion and getting the correct diagrams from HS.
 

Deleted member 1487

Okay so it seems that mounting Cowl guns would impinging upon the design to much and firing through the prop ala Motor-Kanon style is out due to the positioning of the Engine and fuel tank.

I wonder if the use of under wing 'Gondolas' was ever contemplated as a short term fix as sported by the later BF109s and S gun mounts on Hurricanes.

But it seems that the simplest answer was coughing up some dosh in a more timely fashion and getting the correct diagrams from HS.
The wing gondolas badly impact performance and stands out, so like the LW in 1943-44 they get picked out as easy meat by escorts, who can then remove the significant threats to bombers first and stack up their kill score. Plus it impacts fuel economy, which for Spitfires, who already have short range, shorter in fact than an Me109 IIRC, would be in a bad way. Hurricanes could handle it better, as they did mount wing cannons for ground attack (once the cannons were sorted), but they could use gondolas instead of the bombs they historically carried; however those reduced top speed to 300 mph, which would make them very vulnerable to any German fighter.
 
Well, given the size of the 20 mm Hispano cannon installation, firing a 20 mm shell through the propellers in a cowled installation even with the interrupter gear was out of the question on the Spitfire and Hurricane. Indeed, the Bf 109 the 20 mm MG 151 (and eventually MK 108) cannon fired through center of the propeller spinner.
 
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