Hurricane Mk IIC cannon:drum-magazine or belt-fed?

[Johnny .45]

Hey, everyone. This is post #1 for me on this forum. I have a bad habit of making my posts far too lengthy and detailed, but if you'll bear with me, I shall try to restrain myself! =)
Okay: the Hurricane Mk IIC, with it's 4 x 20mm Hispano cannons, is variously stated as having 90 or 91 round capacity per gun, for a total of 360 or 364 rounds. I assume the one extra shell per gun can be explained by crewmen putting the additional shell into the feed mechanism, or even the chamber...sort of like how a semi-auto handgun with a 7-round magazine can carry "7+1", with a full magazine and one in the chamber.
But that's not what I was wondering. I had intended to ask if the Hurricane was belt-fed or not, but I actually just barely found a poor-quality photo that shows that the Hurricane did indeed have ammo-belts and Chatterault mechanisms. So, now my question is: why is the ammunition capacity of the Mk IIC so much smaller than cannon-armed Spitfires? A Spitfire Mk V used drum-fed Hispanos with a 60-round capacity per gun, but the later versions with a "C" or "universal" wing could hold up to 125 rounds per gun.
The Hurricane is notorious for having a relatively thick wing which limited performance, but did give plenty of room for up to 12 Browning .303's or 4 large Hispano's. It was a trick getting four cannon to fit into the Spitfire's thin wing, but they managed. So, if the Hurricane has all this room inside the wing, then why is it limited to only 90 rounds per gun? They can fit 120 - 20x110mm shells in the cramped Spitfire wing, but they can only fit 3/4 of that in the larger Hurricane?
My guess is that it has to do with how the guns were installed. The Spitfire's Hispanos were "staggered", with the inside-gun muzzle protruding distinctly further from the leading-edge than the outside-gun. This allowed the designers to run the magazine boxes side-by-side, one ahead of the other, matching the location of the cannon breech. I doubt they had much choice, since the wing was too thin to lay them on top of each other...the ammo capacity would have suffered.
The problem is, I'm not sure exactly how the Hurricane's gun bay and magazines are laid-out. The guns themselves are very close to being level with each other...I believe that the outer guns are actually an inch or two further ahead than the inner ones, but the difference isn't immediately apparent.
Of course, this makes it impossible, or difficult to "stagger" the magazine-boxes, so they have to lay them on top of one another...the wing may be thicker than the Spitfire, but it's still to thin to lay two 120-round boxes atop each other, unless they were very long and skinny. So the Hurricane got stuck with only 90 rounds per gun.
But one has to wonder why they didn't stagger the guns in the Hurricane like the ones in the Spitfire? It could have 180 rounds per gun that way! I'd have to guess that maybe it has something to do with the narrower chord of the Hurricanes wing..."chord" is the distance from the wings leading-edge to trailing edge. And the Spitfire had an unusually wide-chord wing. Maybe there just wasn't room?
Plus, Hispanos are very heavy and powerful weapons, even compared to other 20mm weapons. I suppose taking center-of-gravity into account, a designer would either have to put both guns right on the CoG, or put one ahead and one an equal distance behind. So I suppose thinking of the considerable length and weight of the HS.404, the narrower-chord wing, and the need to keep the plane balanced, maybe that WAS the only way to put four cannon in the wings of a Hurricane.
It's also worth considering the fact that 20mm cannon-shells weigh quite a bit! The Hurricane was always a bit "under" in performance, and slinging four 90lb guns plus ammo in the wings hurt it's performance even more. Maybe adding more ammo would just make it worse. I wonder though...I know that some Hurricanes, particularly in the deserts, would remove the outer pair altogether to save a little weight. If I'm right about the "stacked" ammo magazines, it seems conceiveable that one could remove the outer cannon, and "double" the magazine...so each wing would have one cannon with 180 shells, and still be lighter than a four-gun machine.
So, what does everyone think? I suppose I went and sort of answered my own question, at least a bit. Can anyone confirm, or debate my ideas? Also, does anyone know where I can find cutaways and/or diagrams, photographs of the different Hurricane wing-types? I've only found Spitfire ones, so far. =/

Regards,
Johnny .45

[Bill Walker]

I think you hit a number of the key issues. One is certainly weight, of guns, ammunition and the structure to support the guns and the belts. IIRC Hurricanes had a truss type wing construction, with spars and ribs made of thin rod-like elements, while the Spitfire had a stressed skin construction, with stamped ribs and the spar being a mix of stretched sheet metal, extrusions and machinings. In general, a sheet metal structure will give you more choice in where you add new structural elements, which makes (again in general) for lighter structure.

The sheet metal construction will also give you more choice in where you place new items like cannon (easier to make cutouts, more choice in structural design of attachments, more open space), and therefore might have made it easier to stagger the guns and permit longer belts.

Also, you would need to know where the "other bits" are inside the wings. Studying the cutaway drawings on the Flight website might explain differences in the relative gun positions within the wings. I think both Hurricane and Spitfire cannon installations were done fairly quickly, so they would not have been interested in re-designing and requalifying flight control push rods and cable runs, fuel tanks, and whatever else was buried in the wings just to get a few more rounds in. I suspect that, in both cases, once they got a solution that worked, the design and test teams moved on to the next thing on the "to do" list.

[Graham Boak]

I think you've both made good points, but I would point out that neither had fuel tanks in the wings (except the later Mk.VIII Spitfires, which is irrelevant to the discussion, but has to be cleared out of the way!) Both the Hurricane and Spitfire wings were stressed skin, with most of the loads carried by the spars and ribs: I don't see that it would be any easier to add strengthening structure in one or the other. The truss structure of the Hurricane only extended out to the undercarriage. I suspect the Hurricane required less redesign to take the cannon, because of the large weapon bay for four guns rather than two, but this alone can have little effect on the quantity choice of ammunition.

One question I have - did the (as originally desired) 4-cannon version of the Spitfire c wing retain the 125 rounds per gun, or was it then restricted to some 60 per? In which case the two types have much the same, and the answer is that 60 rounds is what the appropriate experts thought necessary.

The point about weight is well made: for both fighters, the 4-cannon version was considered restricting on performance and handling, and saw one pair removed. This was normal on the Spitfire, if less so on the Hurricane.

[Johnny .45]

-Bill: Where is this "Flight" website? Do you think it has a cutaway diagram of a "C" wing Hurricane? Because that's one important piece I'm missing. I'm pretty limited in my resources...I have a cheap book of cutaways, but the only Hurricane they show is the "A" version, with the 8 x .303 Brownings. I'm very curious to see how the design changed between the "A", "B", and "C" versions.

-Graham: First, where did you get the idea that the Hurricane didn't have wing-tanks? It did have tanks in the wings....34.5 Imperial gallons per wing. In fact, I was just reading somewhere the other day that although the fuselage tank was notorious for turning the cockpit into an incinerator if it was ignited, many pilots considered the real vulnerable spot to be the wing tanks. I guess for an enemy on your six, the wing tanks are a lot easier to hit! All the same, I think I'd prefer to have a spar burned through than to have my LEGS burned through. Which did happen...I've heard some pretty gruesome tales about pilots caught for even a few seconds in the cockpit of a Hurricane one the flames started coming through the bulkhead.
As for the ammo capacity of the 4 vs 2 cannon Spitfires, I think I have a pretty good idea...Mk V with "B" wings had a single Hispano in each wing, each with a 60-round drum. When they went to the "C" ("Universal") wing, the 4-cannon types had box-magazines with 120 linked rounds per gun, for a total of 480 rounds (a pretty good leap!). However, I don't know whether the "C" types with both .303 Brownings and cannons used the space in the second gun-bay to give each of the two Hispanos 240 rounds or not. I've never heard it before....probably a weight thing? Two .303's with 350 rounds each probably weighs close to a single Hispano with 120 rounds.
So, basically a Hispano with belt-feed (i.e. any type after the "B" wing) has a MINIMUM of 120 rpg....the only guns that held only 60 were the early drum-fed ones. Here's a good site that someone directed me to a while back...
http://spitfiresite.com/2010/04/conc...ing-types.html
That's the sort of article I need to find for the Hurricane!

(Correcting my original post...the box magazines held 120 rounds per gun, not 125. I was thinking of the outer-wing guns of the Fw 190)

-

[Bill Walker]

Here is a link to the Flight magazine on-line cutaways. A great time waster!

http://www.flightglobal.com/staticpages/cutaways.html

[Pilot]

I have one cutaway of c model and it show drum with cannon. When airplane have drum you could note bulge on the top of the wing (I talk about the Spitfire and Hurricane).

Cheers

[Graham Boak]

My apologies: I was thinking of the tank before the pilot as the only Hurricane tank.

The Hispano was a heavy gun: Perhaps the Hurricane Mk.IIc manual quotes the masses of guns (or the Spitfire equivalent). I'll dig them out later. Laddie Lucas on Malta was critical of the 4-cannon Spitfire Mk.V, and guns were removed from the Takali-based fighters (not always the outer ones). The Admiralty agreed that although they had required 4 cannon on the Seafire (to take care of BV shadowers on the Actic convoys), the handling and performance were too limited and the service aircraft was restricted to two.

There is a classic historial argument against placing any guns in the wings of fighters, on the grounds of the moments of inertia restricting the agility. Yakovlev (and apparently Lavochkin, judging from his designs) were entirely opposed, although the lighter and smaller Russian cannon would have been less restrictive than the long heavy Hispano. Messerschmitt also disapproved, and the loss in agility from the gondolas on the Gustav are, I think, well recorded in Luftwaffe memoirs. The Fw 190 suffered less, but it did have superb ailerons. Even so some examples were seen without the outer guns, and not just the fighter-bombers.

Today I was looking at the Haynes manual for the Hurricane: it has a lot of interesting items, and some previously unpublished photos. However, from memory, it also has a cutaway for the Mk.IIc. I saw it in WHSmiths at Deepdale, Preston, so presumably it is quite common elsewhere.

[Johnny .45]

Originally Posted by Bill Walker

Here is a link to the Flight magazine on-line cutaways. A great time waster!

http://www.flightglobal.com/staticpages/cutaways.html

Ah, and that's what I do best! I can waste time like NOBODY'S business!
Thanks. I'll be sure to check it out in a moment, once I've written this. And got another cuppa coffee.

-"Pilot": Perhaps I'm just misunderstanding you; when you say "When airplane have drum you could note bulge on the top of the wing", I hope you are talking about a specific TYPE of bulge. Because even planes without drum-magazines had bulges to cover the electric-feed mechanisms that pulled the belt of ammunition into the breech...it looks kind of like a "miniature drum".
The drum-magazine Spitfires like the "B" wing Mk V had a unique type of large bulge to cover the top of the drum. When they went to the "Universal" wing, they also went to belt-feed. But they still have bulges over the feed mechanisms...originally the four-cannon planes had a single wide bulge covering the two cannons in each wing. If it was a 2-cannon type, it had a single, much narrower bulge. A bit later on, they began using two narrow bulges to cover the cannons on the 4-cannon types, because it created less drag than the single wide bulge did.
Maybe you knew all that already; I'm just trying to be helpful.
(And if I have to type the word "bulge" one more time...I won't be responsible for my actions! )

LOL...I like this one!
I'll have to show that to my mother...I'm sure she still remembers me running around pretending to be a plane when I was a little kid!

-Graham- As far as I know a Hispano weighs about 90-something pounds...that's like a bit over 40 kilograms. I don't know if that includes the weight of the electric motor/drum magazine though. And I'm sure that 90 rounds of 20x110mm ammo weighs a considerable amount too.
What you say about guns being removed is entirely true, and most major combatants would do this from time to time...except the Italians. Their planes had barely enough firepower as it was, for most of the war. I think of it as the "Zero Approach"...when you have to choose between firepower/armor and performance, some pilots (usually the better, more aggressive ones) would choose lighter armament in the interests of better performance.
I guess they figured a shitload of firepower is no good if you can't bring the guns to bear on the enemy, and although armor is nice, it's better to be too quick to hit at all! The Zero was probably the most obvious example of this, as it was designed that way rather than modified, but it's the same idea. (Although one shouldn't forget that PART of the reason they never gave the A6M adequate protection was that there just wasn't an engine that could handle the extra weight).
I've been thinking about looking into the topic of the Zero and it's armament...perhaps I should make it a new thread? Anyway, the Japanese pilots at the beginning of the war weren't at all worried about the lack of armor or self-sealing tanks. They didn't even want the 20mm cannon at first, they thought it was too heavy. And in fact, some pilots DID remove the cannons, figuring that two 7.7mm RCMG's were plenty. Apparently a good pilot in a agile, vulnerable plane with very light armament is dangerous enough! Let's say, the Spitfire probably COULD have fought the whole war with nothing but it's eight .303's...it just would have been a lot harder!
"Yawn." I'm digressing. I have a bad habit of that, and it always takes me way to long to finish a post! Anyway, yes many German Fw 190 pilots would remove the outer pair of MG 151/20's to save weight. At least the remaining two cannons and two MG's were easily sufficient, especially since the wing-root cannons are more like fuselage-mounted guns than wing guns.
I suppose there's no real reason to re-iterate the whole "fuselage vs wing-mounted armament" debate, but like you said, it's been going on a long time! Fuselage-mounting may seem ideal in many respects, but it has it's drawbacks as well. I think that first, and perhaps most importantly, a single engine fighter must either: a.)synchronize the guns to fire through the prop, which decreases the rate of fire and reliability of the weapon, or b.)set it up to fire through the hub, i.e. Bf 109, P-39, Dewoitine D.520, MS.406, etc.
Of course, this has it's own score of problems...the plane AND the engine must be specifically designed for it, and the Germans had several difficulties in making in work, first with the Bf 109E, then when they tried to fit the larger MK 103 cannon in the later 109 variants, and also trying to fit an MK 103 (and 108, I think) into the Jumo engine of the Fw 190 Dora...I don't think they ever actually succeeded in giving the Dora thru-hub armament, but DON'T quote me on that! They DID finally manage to cram a hub-firing MK 103 into the Dornier 335, but I think that was the only one.
Back to fuselage guns: Space is also at a premium in a single-engine fighters fuselage. It's hard enough to fit an engine, accessories, oil/coolant tanks, engine bearers, fuel tanks, etc into such a space without adding bulky guns and ammo-tanks as well.
Plus, any switching of armament calls for a lot more relocating and fiddling-with of equipment...as the Germans again found out when they went from the MG 17 to MG 131. Eventually, the only way they could do it at all was by making the fuselage a bit bigger to cover the spent-case chutes...and that was AFTER a lot of careful thinking. Going from .303's to 20mm's in the Spitfire was a lot easier (although not exactly a piece of cake!).
Guns vary in reliability, but all automatic weapons are liable to extreme heating when fired in any length...a barrel can get so hot that it actually "droops" and is ruined, and bores will erode quickly once the maximum practical rate-of-fire is exceeded. Most importantly, unless it is an "open-bolt" design, hot machine guns are liable to "cook off" a round if the camber get too hot...meaning that the barrel is so hot, the round fires even though the trigger wasn't pulled. And once a round is fired, the next is loaded, and cooks off, and so on. So the already-too-hot gun will fire until it runs out of ammo, and will certainly be ruined.
Also, since a synchronizer only controls the trigger, there is no guarantee that there won't be a prop blade in front of it when the bullet leaves the muzzle...especially if the gun just automatically empties it's magazine. You'd probably shoot your whole prop right off! An infantryman with a machine gun that "runs away" can just grab the belt and stop the feed, but I don't think you can do that in a fighter.
So, obviously placing a gun between the hot cylinder-banks of an engine, or behind a hot air-cooled radial will mean you can fire it that much less before it's in danger. Designers had to figure out clever ways of venting air over the guns and to the ammunition, to keep it cool. (Of course, with wing-mounted guns, the problem is the opposite...they need HOT air to keep them from freezing up!)
The vibrations of the engine can effect reliability, and accuracy too, so you need vibration-absorbing mounts that will ALSO keep the gun aligned on target.
The benefits of course are that you get a tighter pattern, and can fire from any range...wing guns need to "converge" at a certain distance, and trying to hit a target at less or more than this distance is difficult. Probably the most notorious for this is the eight-gun Spitfires, who's guns were spread out along almost the entire length of the wing. Not only is convergence a problem, but an airplanes wings flex a considerable amount during maneuvers (you don't have to twitch very much to miss a target at 250yds with a rifle!). The further out on the wing, the more the gun will flex.
And then there's the whole issue with some guns freezing and not firing, so the designers have to pipe hot air to keep them warm, and the red squares around the muzzles of RAF fighters is actually tape, to keep condensation and cold air out of the gun bay until it fires. Maybe that's common knowledge to most people, but I only learned that myself a year or two ago.
And of course, like you said, having the weight out in the wings means the plane is less "snappy" in a roll. That's one major reason that the P-38 couldn't keep up with single-engine fighters...it rolled fast enough once it got going, but it took longer to "get moving" when the yoke was turned. (Of course, I'm speaking of the weight of the engines, not of guns...the P-38's centerline-mounted guns were just about ideal, but only because it wasn't competing with and engine for space)
So you could more or less say that no-one will ever agree to a "best" one...it's all a matter of perspective. In pure performance, fuselage guns were the best, providing a tighter pattern, reducing flex, no convergence, etc. But this superior performance was balanced against the difficulty of installation, and they tended to be less reliable and rate-of-fire was reduced. More or less, you could get the same effectiveness with only 2/3 or 1/2 of the number of guns needed to get the same effect from wing-mounted guns.
Simply put, one could say that for fighter-vs-fighter combat, fuselage guns gave an edge, less so for shooting down bombers, etc. But for a plane mostly used for strafing and ground attack, the convergence, etc was less of a problem. Mostly the targets were stationary, and an attack run would generally be made without much violent maneuvering.
Sigh...I said I wasn't going to go over all that! Why do I do these things to myself? I wonder what the maximum length of a post can be, anyway?
BTW...you really said "Haynes manual" for a Hurricane? LOL, the only "Haynes manuals" I've ever seen around here are the ones for home-mechanics who want to work on their own cars! Is this by any chance the same "Haynes"? Or is that just a coincidence?

Okay everyone...sorry for making it so long. I'll try to keep it shorter in the future...its just too much to absorb at once!

Cheers,
Johnny .45

[Johnny .45]

Originally Posted by Pilot

I have one cutaway of c model and it show drum with cannon. When airplane have drum you could note bulge on the top of the wing (I talk about the Spitfire and Hurricane).

Cheers

Do you mean you have a cutaway of a Hurricane Mk IIC on your website, or do you mean at your home? I looked around your aviation website, but I didn't see anything like that (although there's a lot of other great stuff). I liked the parts about the Serbian air-forces...I've always had a lot of respect for the Serbs fighting qualities.
Anyway, very interesting stuff on that site...I bookmarked it, because I haven't got to check it all out yet.

Cheers!=)

[Pilot]

I hope you are talking about a specific TYPE of bulge

Yes, just like that. About cutaway- I have it at home, stored. Thank you for the comments about our web site, there is plans to place there from 8000 to 15000 of archive images with various text... long time project.

Cheers