WWII aircraft armament

[gagenater]

I meant that it was not the kind of range where people expected to shoot effectively, though I'm sure there were number of kills even past such extreme ranges. The convergence of the guns was usually set between 200-300m. Some aces preferred even closer (and indeed, it's in Dicta Boelcke to only fire at close range).

Which brings up another issue which hasn't been mentioned in this thead yet, and that is gun placement. If you have guns in the wings, then convergence matters quite a lot, and evasive maneuvers by you or the enemy can get your bullets very far off their intended target. However guns mounted in the nose of the plane don't have these sorts of issues.

BUT

there isn't much space in the nose of a plane, so you had better make that gun count - the Germans routinely tried to get a 20, 25 or 30 mm gun in that spot. The Americans had a few attempts too, notably the early war P39 air-cobra with a 37 mm nose gun that had the engine built around it. However for the most part the American 'solution' was to line up a bunch of guns in each wing. These guns were necessarily limited in size by the width of the wing, and the .50 cal machine gun was the best compromise out there. In theory you could put 20 mm guns in the roots of the wings, 0.50 cal's further out, and 0.30 cals' on the edges, but that's a horrible mess for trying to set up all the different gun and bullet firing characteristics, ranges, ammunition capacities, and firing switches. Using all one caliber eliminated all those issues. The Germans and to a lesser extent the Russians stuck with a few high powered guns at center (or wing root) and 0.30 cal's other places as a backup.

 

[mccarty.geoff]

Like I said before the convergence angle would be the tightest grouping of rounds at range. Setting a P-47s .50s at 1000 feet would allow for effective fire out to an 1800 foot spread in a 30 foot killbox indicated by the target reticle. I find people over estimate musket ranges and under estimate semi-modern weaponry for some reason.

 

[gagenater]

Like I said before the convergence angle would be the tightest grouping of rounds at range. Setting a P-47s .50s at 1000 feet would allow for effective fire out to an 1800 foot spread in a 30 foot killbox indicated by the target reticle. I find people over estimate musket ranges and under estimate semi-modern weaponry for some reason.

Those are the ranges with the plane flying straight and level, and shooting at a static target. Now start whipping the plane around in a series of banking maneuvers which constantly change the angle and direction of the wings (as well as introducing some serious flexing of the wings which is easily visible in slo mo hi speed camera footage) while climbing or diving, and shooting at a target doing the same, while the wing droop/angle constantly changes as the wing mounted fuel tanks are depleted and the size of the killbox and # of bullets that get into it shrinks dramatically. There are physical and technical 'trick's' to try and correct for these problems but they aren't perfect by any means. There are very major advantages of having the gun(s) mounted as close to centerline as possible. The absolute worst position to put a gun in is on the wingtip. You can see/watch the wings on a modern jet airliner wobbling and flexing from crosswinds on a flight. Now scale that to an airframe going through G force maneuvers at higher speeds. Yes - the fighter is (hopefully) very strongly constructed, but this is still a pretty big technical issue. So large that the major air forces engaged in WWII were more or less evenly split between trying to figure out how to solve them, and how to figure out ways to avoid them.

 

[Antediluvian Monster]

Like I said before the convergence angle would be the tightest grouping of rounds at range. Setting a P-47s .50s at 1000 feet would allow for effective fire out to an 1800 foot spread in a 30 foot killbox indicated by the target reticle. I find people over estimate musket ranges and under estimate semi-modern weaponry for some reason.

At the same time, there are 3.24 times more potential points of aim in space at 1800 feet than 1000, the time to target will increase, dispersion will increase and the fire will become more converged on the less vulnerable wings.

 

[Acheron]

The same situation could have applied if the Germans had fielded heavier bombers, but as pointed out, a .50 cal has over 2-1/2 times the hitting power of a .303, and that extra weight means that it also loses less velocity due to air friction over the same distance, and can hit with the same velocity at a longer range. Some of the armored components (such as the heavy plates behind the pilots' seat) might not be penetrated at longer ranges, but the .50 cals would still have been effective at closer ranges, unlike the British .303 and American .30 caliber machineguns (which were still used as defensive armament on many aircraft).

Holes in the wings and tail surfaces, unless the round hits a control cable or some other useful item, really don't do much, whether you fire a .30 caliber or a 37mm round. The round just passes through, leaving a small hole. The heavier shells were normally packed with explosives, but not likely to be set off by the thin aluminum skins (or even fabric in places on some planes during the first couple of years of the war) if they didn't hit a structural component. Patching up a few bullet holes wasn't the most complex or expensive thing in the world, and the planes would usually be able to fly the next day.

Thank you again Kovax. Are you sure aircraft cannon shells would not be set off by light alumunium aircraft skins? I would have thought these to have a sufficiently sensitive trigger, what point would there be to ignite only against something harder?

You give me the impression that six or eight M2 Brownings might have made a decent impression on a bomber, given their combined rate of fire (and heavier damage than rifle-caliber bullets) something seems likely to have hurt.

Probably one of those Japanese ones having it's torp warheads blown up due to strafing attack.

Could be the famous Long Lance torpedoes of the IJN. Very deadly when they made contact with an opponent, but if they got set off on their own ship...

 

[Kovax]

Thank you again Kovax. Are you sure aircraft cannon shells would not be set off by light alumunium aircraft skins? I would have thought these to have a sufficiently sensitive trigger, what point would there be to ignite only against something harder?

You give me the impression that six or eight M2 Brownings might have made a decent impression on a bomber, given their combined rate of fire (and heavier damage than rifle-caliber bullets) something seems likely to have hurt.

Could be the famous Long Lance torpedoes of the IJN. Very deadly when they made contact with an opponent, but if they got set off on their own ship...

Not positive about how much force it took to detonate a shell, but they used a percussion cap, and like a kid's toy cap pistol, it required a hard enough impact to detonate the primer. I've seen pictures of what happens when a 37mm shell hits a wing spar, and it does a number on the wing, and seen images of a wing with different sized holes through it, some of which MIGHT have been 20mm rounds. This question probably requires someone more familiar with the actual ordnance, not just a general enthusiast.

I would assume that six or eight .50s would have had a high chance of doing serious damage to a bomber, even though the rounds are not explosive. The rate of fire would probably make up for the lack of blast damage, whereas .30 caliber rounds would be more likely to be defeated by armor, or not do enough damage to vital parts to break them.

 

[Acheron]

Another question, the original article claimed among other things "Germans either went for shell weight and muzzle velocity and sacrificed rate of fire or went for shell weight and rate of fire and sacrificed muzzle velocity". The later I do not quite understand, I would have assumed that heavier shells would be the limiting factor for rate of fire. If this is true, how did one make a gun that fired big heavy shells at acceptable rates of fire, albeit while sacrificing muzzle velocity?

EDIT: Checked wikipedia on the MK 108, apparently, in case of that gun, they could have used a "heavy bolt" and a long barrel for a high muzzle velocity, but a lowered rate of fire. Instead, they opted for a "light bolt" and a short barrel for high rate of fire but lowered muzzle velocity. I guess a heavy bolt takes more time to move around. Does anyone know a good introduction to gun mechanics?

 

[kaoss]

That: A heavier bolt needs more time to move back and forth, thus increasing cycle time and decreasing rate of fire. If I recall correctly, the MG34 had two bolts for different rates of fire.

 

[Denkt]

Another question, the original article claimed among other things "Germans either went for shell weight and muzzle velocity and sacrificed rate of fire or went for shell weight and rate of fire and sacrificed muzzle velocity". The later I do not quite understand, I would have assumed that heavier shells would be the limiting factor for rate of fire. If this is true, how did one make a gun that fired big heavy shells at acceptable rates of fire, albeit while sacrificing muzzle velocity?

EDIT: Checked wikipedia on the MK 108, apparently, in case of that gun, they could have used a "heavy bolt" and a long barrel for a high muzzle velocity, but a lowered rate of fire. Instead, they opted for a "light bolt" and a short barrel for high rate of fire but lowered muzzle velocity. I guess a heavy bolt takes more time to move around. Does anyone know a good introduction to gun mechanics?

More muzzke velocity mean more force which in turn may stop the Aircraft dead in the air. There was a test done by the Swedish airforce around late 1940s in which a J21 which was armed with 13 guns due to additional guns by carry a gunpod which when fired produce so much force the Aircraft more or less stopped.

More powerful Engine mean more powerful guns could be carried on ligther Aircrafts. A Spiteful I think would be armed with 4 20 mm guns which give it huge firepower while being able to outrun majority of the enemy Aircrafts. In comparison the spitfire mark I only carried 8 times 7.7 mm guns while being much slower.

 

[Henry IX]

Based on reading various British pilot's recollections from the first few years of the war, the only reliable way to shoot down a bomber with .303 MGs was to hit the engines. Most WW2 era twin engine aircraft were hard to fly on one engine - I believe a powered glide was essentially the best you could do, and that required throttling the remaining engine down, a generally bad idea if there is a hostile fighter attacking you. In this situation the crew have 3 options: parachute out, controlled crash landing or try to escape the pursuing fighter by flying level and slowly.

The large four engine bombers favoured by the western allies were much more stable and shooting one of them down with light MGs would require a lot of hits or a lot of luck...

 

[Acheron]

@Henry IX some credit is due to the designers of the heavy western bombers IMHO, somehow, I suspect the He-177 wasn't very stable or resilient to shooting.

 

[Kovax]

German engine designs lagged behind their British counterparts, perhaps most notably in the development of superchargers for high-altitude performance. Hitting the engine of a German bomber likely meant a forced landing or crash, or else a major drop in altitude (where the remaining engine could operate more efficiently) at the very least. Hitting the engine of a British bomber was more likely to result in breaking off the mission, dropping the bomb-load immediately to reduce weight, and limping home at severely reduced speeds while becoming an easy target for anything at that altitude with a gun on it.

Radial air-cooled engines could sometimes be damaged without quitting completely (one cylinder dysfunctional), while water-cooled engines were prone to losing coolant from hits to the engines, radiators, or water lines between. The B-17, 24, 25, and 29 all utilized air-cooled radial engines, making them relatively tough targets. The Heinkel and Dornier bombers used extensively by Germany during the Battle of Britain were all water-cooled and reliant on both engines, so it didn't take all that much damage to prevent them from crossing back over the Channel.

 

[Valhallas Call]

@Henry IX some credit is due to the designers of the heavy western bombers IMHO, somehow, I suspect the He-177 wasn't very stable or resilient to shooting.

My great uncle was a B-17 pilot who on one particular mission over Germany had a heavy-caliber AA shell (either 88mm or 105mm) punch through his starboard wing without detonating. No extensive damage to the aircraft, but it went right through a fuel tank, so it was leaking large amounts of fuel and eventually both starboard engines sputtered out. He and his co-pilot managed to get the aircraft back to England and landed safely on only their port-side engines. That's a testament not just to their flying skills (both he and his co-pilot got DFCs for that), but also to how tough and versatile those big bombers could be.

 

[Henry IX]

The Lancaster was certainly built with the lessons learned from the battle of France in mind, where the vulnerability of the existing twin engine bombers was exposed. It was deliberately designed to be durable and hard to shoot down. I assume the B-17 incorporated the same lessons as well.

 

[gagenater]

The Lancaster was certainly built with the lessons learned from the battle of France in mind, where the vulnerability of the existing twin engine bombers was exposed. It was deliberately designed to be durable and hard to shoot down. I assume the B-17 incorporated the same lessons as well.

Nope- the B17 design was complete and on the air in 1935.

 

[Kovax]

Later B-17 designs incorporated numerous and constant changes to compensate for weaknesses discovered during the war, including more forward firepower and some frontal armor plates. Both the Germans and the Japanese learned quickly that the best way to engage a B-17 was head-on, where the majority of its defensive turrets were ineffective, and the clear Perspex nose offered no real protection against shots to the front traveling the entire length of the fuselage. The addition of a chin turret, modifications to the dorsal turret, and some armor in the control consoles made them a lot less vulnerable, and quite capable of shooting back. A few B-17s were also refitted with "cheek" guns, two on either side of the cockpit. The combined forward firepower of those models was a rude surprise for the first opponents to encounter them.

As said, the original B-17 design pre-dated WWII by several years. The plane was modified rather extensively over the course of the war.

I believe it was the UK's Sterling bomber which incorporated diagonal fuselage stringers, giving it an incredible amount of resilience against flak and cannon fire. That, of course, still offered no increase in protection for the engines, which were water-cooled.

 

[Henry IX]

Nope- the B17 design was complete and on the air in 1935.

Thanks. I should have known that, but my plane-nerd days were a long time ago...

With some extra research, it appears as though the B-17 was always designed to be able to engage in aerial combat with a concept of a massed fleet of will armed bombers able to destroy attacking fighters with massed heavy MG fire. Whilst the effectiveness of the defensive armament proved to be lacking and escorts needed the design was always intended to be able to fight, and hence its toughness. The ability of the B-17 to survive hits was improved with numerous upgrades throughout the war.

 

[gagenater]

Later B-17 designs incorporated numerous and constant changes to compensate for weaknesses discovered during the war, including more forward firepower and some frontal armor plates. Both the Germans and the Japanese learned quickly that the best way to engage a B-17 was head-on, where the majority of its defensive turrets were ineffective, and the clear Perspex nose offered no real protection against shots to the front traveling the entire length of the fuselage. The addition of a chin turret, modifications to the dorsal turret, and some armor in the control consoles made them a lot less vulnerable, and quite capable of shooting back. A few B-17s were also refitted with "cheek" guns, two on either side of the cockpit. The combined forward firepower of those models was a rude surprise for the first opponents to encounter them.

As said, the original B-17 design pre-dated WWII by several years. The plane was modified rather extensively over the course of the war.

I believe it was the UK's Sterling bomber which incorporated diagonal fuselage stringers, giving it an incredible amount of resilience against flak and cannon fire. That, of course, still offered no increase in protection for the engines, which were water-cooled.

Thanks. I should have known that, but my plane-nerd days were a long time ago...

With some extra research, it appears as though the B-17 was always designed to be able to engage in aerial combat with a concept of a massed fleet of will armed bombers able to destroy attacking fighters with massed heavy MG fire. Whilst the effectiveness of the defensive armament proved to be lacking and escorts needed the design was always intended to be able to fight, and hence its toughness. The ability of the B-17 to survive hits was improved with numerous upgrades throughout the war.

Yep yep. Wasn’t meaning to imply that the B17 didn’t receive many upgrades during the war. Just trying to point out that the 4 engine configuration, wing and fuselage arrangement were set up well before war broke out.

The original requires the from the US army air corps was for a plane that could perform precision bomb raids in Europe from the continental US and then return without refueling. This proved overly ambitious for the technological constraints of the day, but the requirement and the large procurement order that followed stimulated the development of some bomber aircraft that turned out to ‘set the standard’ for their types.

 

[Jopa79]

Last weekend I was watching Hercule Poirot - what a nice Belgium fellow, if you happen to know him But seriously, this is related to the subject. In the 8th episode on the first season 'The Incredible Theft' Poirot investigates a crime touching espionage and military secrets. The British have on development phase this incredible and superb aircraft desing 'Mayfield Kestler' (surprisingly similar in compare with the Spitfire -fighter) This desing has among other capabilities enormously strong wing spar (one reason why the Germans want the blueprints of this model) and it handles well the recoil generated by the machineguns on the design's wings.

So, my question is: Can someone explain the idea of wing spar? How was the wing framework designed in WW2 -fighters to handle the recoil of the armament?

 

[Kovax]

A wing spar is just the name for the frame members running from fuselage to wing tip. A stronger or more resilient wing spar is definitely an advantage, and various designs were used, with I-beam style caps and webs with holes to save weight, tubular designs, and various other ideas which were mostly tried and quickly abandoned.