Centerline Guns configurations

[drgondog]

Originally Posted by therritn

IMHO, I think that what makes the difference is the type of weapons as opposed to the position. With both wing and nose mounted weapons..they're usually boresighted to converge at a certain distance. It all depends on the type of weapon or weapon group

For example: the P-38 Lightning has four .50 caliber MGs and a 20 mm cannon in the nose. If you subtract the cannon, a plane with 4 .50s mounted in the wings would do as much damage.

There are three issues between fuselage mounted and wing mounted guns.

1.) it is much easier to boresight the nose mounted package
2.) wings flex under load, and the flex varies with the G forces... torsion and vertical deflection
3.) the wing mounted guns will NOT converge to small pattern except for one range and even that is suspect for manuevering fight do to wing loading deflection/torsion - whereas fuselage is much 'stiffer' to line of sight.

So in a fight in which deflection is present (assuming pilots of equal skill) wing mounted 50's in both a P-47 and 51 would be unlikely to even converge at the boresight range (or any other range) whereas the P-38 would be concentrating its fire to limit of combination of mount stiffness and ballistics of the weapon.

I suspect the inboard mounted 20mm on the Fw 190 would be more accurate than the outboard (propeller arc) mounted weapons because the wing root would be far stiffer and less subject to the load deflections as the mid wing mounts. The nose package on both the 109 and 190 would be a better arrangement than the 51/47.

Henning probably has the data but I wouldn't be suprised if 3 weapons on the 109 would consistently put more weight on target at all ranges than either the 51 or 47.

[HoHun]

Hi Renrich,

>Obviously what a tracer is doing at say 200 or 300 yards is different than the solid bullet since the tracer will have lost mass and shape. Any research on that?

Tracer round had ballistically different properties, to the point of being considered misleading. It seems to be very difficult to discern whether tracers pass in front of or behind a target, and air gunners were warned to rely on the gunsight only and use tracers only as a secondary aid. I have read that B-17 or B-24 waist gunners were not provided with any tracers at all because the curved trajectories they'd give when firing abeam were just too confusing. (This might have been the practice in one particular unit only, unfortunately I don't remember where I read this.)

An additional problem was that tracers "extinguished" after a short time (in order to reduce the possible confusion), and if they "disappeared" on the sight line to the target, this could give the impression of the target being hit when in reality, the bullets where nowhere close. The Luftwaffe used a share of "observation rounds" in air gunners' belts to combat this impression - they worked a lot like the famous de Wilde ammunition, which blew up with a visible flash when it struck the target. While the chemical content of rifle-calibre explosive ammunition is not very impressive, this effect seems to have greatly contributed to the usefulness (and popularity) of the de Wilde ammunition

It was not so bad for forward firing guns as the "sidewind" component was (almost) zero, but still tracers had disadvantages as well as advantages. Shooting by tracers alone was considered pointless, and proper use of the gunsight was drilled into the fighter pilots trainees. The advantages must have outweighed the disadvantages in the end, as tracers were kept in use universally (as far as I can tell ... I'm not sure about the Soviets, for example

>Also did anyone have tracer rounds for the cannons?

It's my impression that everyone had tracer rounds for cannon. The Luftwaffe certainly had them for 15 mm, 20 mm and 30 mm, and they were available for the Hispano 20 mm cannon as well. The Japanese had tracer cannon rounds, too. The typcial tracer round was a high-explosive incendiary tracer which had a larger chemical content than needed for the tracer job alone. (I'm not sure if these "extinguished" - that might have been a feature of rifle-calibre bullets only.)

Regards,

Henning (HoHun)

[renrich]

I read somewhere that some USAAF pilots did not want tracers loaded because the tracers gave warning to the enemy pilot that he was being shot at. Makes sense to me in that most air to air shoot downs I believe were from the six o clock position and the downed AC was not aware of his attacker until it was too late.

[drgondog]

Originally Posted by renrich

I read somewhere that some USAAF pilots did not want tracers loaded because the tracers gave warning to the enemy pilot that he was being shot at. Makes sense to me in that most air to air shoot downs I believe were from the six o clock position and the downed AC was not aware of his attacker until it was too late.

I've heard the debate both ways - my father's preference was to put several tracers at the 30 round mark to warn him when he was running out. Henry Brown and Kinnard had same preference.

[renrich]

Hope the Germans did not catch on about the tracers showing the ammo was about used up. I also read that some of the Corsair pilots, since the F4U had separate gun switches would cut off two of the guns, going with four until the ammo ran out on them, leaving them two guns with full ammo for a reserve.

[Tony Williams]

Actually the Germans did catch on to the "load a few tracers at the end of the belt" approach.

I have read that wartime experience among USAAF fighter units in Europe revealed that squadrons which used tracers suffered more losses and scored fewer kills than those which didn't.

OTOH, tracers were popular with bomber gunners as the sight of the tracers flying towards them might make the attacking fighters flinch. The US even developed a special .50 cal tracer round, the ""Headlight", which was designed to be extra-visible from the front in order to emphasise this effect.

[renrich]

Another point to consider on wing mounted versus nose-fuselage mounted guns. A stoppage in a wing mounted gun, especially a cannon can cause the AC to yaw badly. A stoppage in a nose monted weapon will not have much effect.

[HoHun]

Hi Renrich,

>Another point to consider on wing mounted versus nose-fuselage mounted guns. A stoppage in a wing mounted gun, especially a cannon can cause the AC to yaw badly. A stoppage in a nose monted weapon will not have much effect.

Good point! At least the P-51 manual warns against firing anything but short bursts if one wing gun is jammed because its impossible to compensate accurately for the yaw by the use of rudder. I think Freeman's "Combat Profile: Mustang" actually features a combat report from a fighter pilot who had an asymmatric jam (of several guns, if I remember correctly).

Regards,

Henning (HoHun)

[Burmese Bandit]

Another point regarding centerline gun mounting on aircraft performance (and I am surprised that the extremely knowledgeable people on this forum have not commented on this before) is that all other things being equal, not mounting guns in the wings makes an aircraft more responsive to rolling manuevers and holds open the possibility of designing the wing to be lighter, therefore increasing the manueverbility of said plane.

Furthermore, why has no one pointed out the fact that very powerful wing-mounted guns firing heavy bullets and shells can flex the wings when firing, leading to ammo dispersion problems and heavy plane vibrations?

[Burmese Bandit]

Er, just noticed that drgndog has pointed out that second point in his post, though only in passing, and he didn't mention the handling problems caused by flexing wings.