PLS HT look into Breda MG modelling!

[HoHun]

Hi Gripen,

>IIRC Galland claimed that he keeped Bf 109E long time in his memories

Galland stated that he scored 28 victories in one particular Me 109E-4, but I didn't get the impression he stuck to the type after the Me 109F appeared.

>And I believe that for large majority of the pilots later combimation was better simply because better firepower, therefore shotgun example is also very valid.

The point is that the better firepower of wing cannon only materialized at convergence range, while at all other ranges, the firepower of centreline armament was superior. With the sight on target, wing guns could still miss the target to the left and right if it wasn't exactly at convergence range. Firing centreline armament with the sight on target, it was likely that the entire burst was on target, too. Centreline armament made shooting easier - that's what Riemensnider is referring to.

When Galland advocated firepower, he meant firepower - not wing guns. As far as I know he never opposed Mölders' "One in the nose is better than two in the wings", but he was neither content with one in the nose nor two the wings but wanted to get all of them, and heavier machine guns as well.

Regards,

Henning (HoHun)

[GRUNHERZ]

Hooligan:

Not german guns modeling at all.  But I dont think the advantages of center mounted guns transfer well from RL to AH.
This gous for all the planes with central armament.

Why in gods name do you allieds always think its a german plane whine?

[gripen]

Hohun,
In the Caidin's Messerschmitt book Galland states that probably Mölders was only one in the Luftwaffe who was happy about the change from 2x20mm MG FF to 1x15mm MG 151.

And for one reason or another you don't seem (or want) to understand my point (and actually Gallands point) that for  an average pilot amount of firepower (in what ever position in the plane) was more important than concentration of the firepower because average shooting skills were quite poor (shotgun effect). Also it should be noted that centerline armament has advantage from short range but from long range it's pretty much same because shooting was very unaccurate anyway even in the case of the best shooter.

There were pilots who could shoot very well with the Spitfire like Beurling. Generally skill of the pilot and amount of the firepower are more important issues than optimal position of the armament in the plane.

gripen

[HoHun]

Hi Gripen,

>In the Caidin's Messerschmitt book Galland states that probably Mölders was only one in the Luftwaffe who was happy about the change from 2x20mm MG FF to 1x15mm MG 151.

Caidin states that several pilots, among them Mölders, preferred the new armament, while other considered it too light. As I mentioned initially, this opinion was formed by the comparison of 20 mm cannon to the lighter 15 mm cannon. Later this cannon was replaced by a 20 mm, and the only complaints about Me 109 firepower from then on concerned effectiveness against heavy bombers.

Remember that we were talking about the RAF pilots' view who said they'd have preferred the Me 109's armament over the Spitfire's. In January 1942, they were facing Me 109s armed with 20 mm cannon, and they reached the same conclusion as Mölders had reached before.

>And for one reason or another you don't seem (or want) to understand my point (and actually Gallands point) that for  an average pilot amount of firepower (in what ever position in the plane) was more important than concentration of the firepower because average shooting skills were quite poor (shotgun effect).

Since Caidin quotes Galland's comparison as one of "rapier" and "broadsword", Galland's point was power even by that source. Galland's first conversion, the Me 109F-2/U, boosted firepower as well, and without relying on wing guns. Wing guns  would have been easier to implmeent and would also have provided greater firepower since the MG17 cowl guns could have been retained, yet Galland had the centreline guns upgraded.

I'm afraid your point and Galland's point are not quite identical.

I know what you mean by "shotgun effect", but the problem is that not only the density of fire decreases, but that for most distances, the centre of gravity of each wing's guns is laterally off target. Luftwaffe pilots sometimes witnessed tracers missing their aircraft narrowly on both sides of the fuselage - that's what happened when the enemy had his sights on them perfectly, but wasn't exactly at convergence range.

Centreline armament made hitting easier even for inexperienced pilots as it eliminated the convergence-induced range problem entirely. This was quite valuable as an inexperienced pilot could close in to compensate for poor marksmanship without having to deal with lateral strike point offset and two separate centres of gravity for his fire.

Regards,

Henning (HoHun)

[Tony Williams]

Originally posted by HoHun
>but it seems that in 1942, two years after deciding to harmonise RAF day fighter guns at 250 yards (night fighters at 150) a decision was taken to spread rather than concentrate fire, with the guns set to deliver a cone of just under one degree.

I've to admit that I'm surprised to hear that: With a cone of fire of one degree, the pattern at the 250 yards distance would have a 4 m diameter. Assuming the normal dispersion was 0.5 degrees, the bullet density - and accordingly, the lethality - would be just 25% of what it was before. Even comparing it to the Me 109F with half the number of guns, it would only be 50%.

To me, this order sounds like it was born out of desperation. Do you have any information on how long that order remained standard procedure?

There was no indication of any change from that point on. However, it was a large and messy file, full of correspondence, diagrams and so on, and I was (as always) pressed for time at the PRO. So much to see, so little time!

Incidentally, some very interesting points were made about the sighting issue. One was that positive or negative G in combat also caused guns to shoot low or high. This was another reason given for widening the spread of fire. Diagrams showed the cones of fire from concentrated and spread guns in various circumstances.  Reading between the lines, I guess that the RAF found the Hispano so devastatingly effective against fighters that two or three hits would usually do the job, so it was better to spread the fire and score a couple of hits than concentrate it and miss entirely.

Another interesting point of detail concerns harmonisation for range. It was pointed out that the guns could be set to fire "level", which means that the sights would be aimed downwards to harmonise with them, or the sights could be set level and the guns aimed up. The latter was recommended as more useful in dogfighting (although obviously not in ground attack).

Another point at random was that the harmonisation diagram for the Spitfire with two 20mm and four .303 had the Hispanos harmonised at different ranges; drawings at different ranges showed a vertical as well as horizontal dispersion. Then there were the early 8 x .303 diagrams - did you know that four different harmonisation patterns were being tried by different squadrons in early 1940? The problem was, as Dowding dryly observed in a note, that the Luftwaffe refused to cooperate in the experiment, as they would insist on crashing their planes into the sea so they couldn't examine the wreckage....

Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://website.lineone.net/~a_g_williams
Gun and ammunition discussions at:
http://www.delphi.com/autogun/messages

[gripen]

HoHun,
I dug a bit and it's a Joe Christy's book (Luftwaffe Combat Planes and Aces) which contains Gallands and also Walter Oesaus views:

"But with only a single nose cannon and pair of rifle caliber machine guns, it (F) did not have the firepower of the E. Veterans like Mölders and Udet prefered that way. The F climbed well, turned tightly and was the last classic Messerschmitt dogfighter. This was fine, if one were an experienced ace, but Adolf Galland and Walter Oesau clearly saw that as the war progressed the number of veteran marksmen would dwindle, while the ranks of raw recruits, many of them product of accelerated flying school crash programs, would swell. These new pilots would know very little of unerring marksmanship. They would have their hands full just flying the airplane. They would invariably be outnumbered, and  Galland and Oesau didn't want to be outgunned too. They demanded that the new 109s carry more firepower, at the expense of performance, and Oesau went so far as to refuse to fly the 109F for several months, even though his wing, JG 1 had already  re-equipped with it."

Galland and Oesau certainly knew the advantages of the center line armament and knew that ace level pilots (like themselves and Mölders) could utilise these advantages (note that this had been my point right from the beginning). But for an average pilot (who certainly was not an ace)  armament of the E was better because firepower was better and therefore possibilities to got hits were better too (because firepower is better then Gallands shotgun for the flying targets claim fits here well). I afraid that  my points are quite identical with not only Galland but with Oesau too. Also I don't see any reason why Galland would have wanted centerline cannon removed from his plane when he got wing cannons (also for center of gravity reasons), he wanted firepower and he also saw firepower of the E better than the F's (despite better fire rate and muscle velocity of the MG 151, 15 or 20mm).

I remember well that we are comparing the Spitfire and Bf 109. Some  good shooters in the RAF might have benefited from the 1x20mm + 2x7,7mm in the centerline at close range shooting but most would not. And at higher range there is not much difference, because then shooting is very unaccurate anyway. The firepower of the Spitfire  was about twice as large than the F's or early G's so for an average pilot possibilities to get hits were therefore better.

Generally I see your views about accuracy of the air  gunnery quite strange, even in the case of the best shooters accuracy was very bad, only small percentage of the bullets hit the target. In the Finnish Air Force main difference between the aces and average pilots was shooting range; the aces were good shooters and shot from very close range and therefore they could benefit from centerline weapons. Average pilots shot from higher range and and were not so accurate shooters, therefore higher firepower is better for them (despite what ever convergence). Also your claim about LW pilots witnesing bullets missing their planes on both sides is quite questionable; how about opinions of those pilots who witnesed hits...

I quess you can't never admit that you are wrong on this but lets try to hit 100!

gripen

I noted that Oesau served  in the JG 51 or JG3 that time. He was KIA in the JG 1 at 1944.

gripen

[HoHun]

Hi Gripen,

the point you seem to fail to appreciate is that more weight of fire isn't equivalent to more firepower or easier aiming. Having the armament out in the wings creates an aiming problem, and this is the problem Riemensnider mentioned.

If we'd choose to ignore this problem, it would be a clear issue, and I'd have to agree with you.

However, at least Mölders, Tuck and Riemensnider thought it was a problem. Mölders and Tuck even thought it was worth sacrificing half the weight of fire to avoid it!

How about the other aces?

Galland didn't actually state an opinion on the matter. However, his Me 109F-2/U with increased centreline armament shows his preferences were not focused on wing guns.

And while Oesau favoured the Emil's armament, don't forget that its powerful 20 mm mine shells stood against the far less lethal 15 mm projectiles of the early Friedrich. As a result, Oesau's decision to keep the Me 109E is not particularly useful for comparing different 20 mm cannon arrangements.

Regards,

Henning (HoHun)

[HoHun]

Hi Tony,

>Incidentally, some very interesting points were made about the sighting issue. One was that positive or negative G in combat also caused guns to shoot low or high. This was another reason given for widening the spread of fire.

I'd guess this might result from the wings flexing under the loads. You wouldn't see that effect with centreline armement.

>Another interesting point of detail concerns harmonisation for range. It was pointed out that the guns could be set to fire "level", which means that the sights would be aimed downwards to harmonise with them, or the sights could be set level and the guns aimed up. The latter was recommended as more useful in dogfighting (although obviously not in ground attack).

Different settings with seem to have been common with the USAAF, too, greater elevation being used for air-to-air combat to improve the view over the nose, and alignment with the fuselage datum line to facilitate low-level strafing runs.

By the way, it's my impression that the British referred to "harmonisation" as the coincidence of sightline and trajectory in the vertical plane, and "crossover" as the coincidence of fuselage axis and trajectory in the horizontal plane. Unfortunately, the actual elevation of the sight line is seldom mentioned.

>Then there were the early 8 x .303 diagrams - did you know that four different harmonisation patterns were being tried by different squadrons in early 1940?

With the poor placement of the Spitfire's guns, I'm not suprised :-) I'd say you could still tell it was orginally meant to carry 4 guns only.

The Hurricane's firepower was acknowledged to be superior even with the same number of guns as they were concentrated right outside the propeller disk.

>Reading between the lines, I guess that the RAF found the Hispano so devastatingly effective against fighters that two or three hits would usually do the job, so it was better to spread the fire and score a couple of hits than concentrate it and miss entirely.

My way of reading between the lines is that they were considering the probability of hit being close to nil and widened the cone of fire just to get any hits, whatever the probability of kill might be :-)

Is there any information on how many hits the RAF considered as necessary to ensure a kill? I think the Luftwaffe arrived at 6 20 mm hits to kill a fighter. It was easier for them to find out, though as they weren't as hard pressed by the Dowding Syndrome as the British ;-)

Regards,

Henning (HoHun)

[gripen]

HoHun,
Well, I have admited several times that aiming problem existed and  benefits of the fuselage armaments were signifigant specially for a good shooter at short range. But also you should admit that for an average pilot firepower (in what ever location in the plane)  was more important than concentration of the fire. And this is clearly the idea what Galland and Oesau were promoting.

And I fully agree that the MG 151/20 was a much better weapon than the 20mm  MG FF. But again  to really utilize these benefits  (ie to substitute weight of fire of two MG FFs with one MG 151/20) the pilot should be a good shooter. Therefore quoting just aces is a bit misleading. The case of the  Spitfire vs Bf109 armament comparison is easier because the HS 404  performed about as well as the MG 151/20 and in addition there were 2 mgs more in the Spit.

Just two posts more...

gripen

[HoHun]

Hi Gripen,

>Well, I have admited several times that aiming problem existed and benefits of the fuselage armaments were signifigant specially for a good shooter at short range.

The benefits of the fuselage armament was that it hit the aiming point no matter what the range is. You don't need to be a good shooter to exploit this - you can be an inexperienced pilot and just concentrate on bringing the sight on target and push the button.

With wing guns, you've to be aware of the range, how it translates into lateral offset of the strike points, keep the relative orientation of the aircraft in the rolling plane in mind, be prepared to aim next to the target to compensate for the lateral offset, or even to push the rudder to yaw one or the other wing's guns on target if you're close.

It should be obvious that this does not make hitting easier, it makes it more complicated. A good shooter might be able to consider all of it and act accordingly without missing his shooting opportunities, but for an inexperienced pilot, guns that hit the aiming point are a big advantage.

Regards,

Henning (HoHun)

[gripen]

HoHun,
Once again: You dont need to prove advantages of the fuselage armament every time. The purpose of the weapons in the plane was to hit the enemy plane and this required good shooting (and flying) skills ie ability to maneuver the plane to the right position and ability to choose right target point. Shooting skills of the average pilots were quite poor and they tended to shoot from longer range than aces, thenefore it was better to have more firepower in the what ever location in the plane than less  firepower in the  optimal location.

Generally if the target  point is not very accurate it is better to have more convergence and more bullets in the air for better hitting possibilities. At short range advantages of the fuselage armament are signigant  ie the advantages can substitute firepower but at long range firepower is more important because shooting is unaccurate anyway (even in the case of the ace).

100!

gripen

[HoHun]

Hi Gripen,

>Generally if the target point is not very accurate it is better to have more convergence and more bullets in the air for better hitting possibilities.

You're neglecting that by spraying a large area, you'll only get few impacts in any part of that area, and accordingly the probability of kill drops.

Let's assume Gaussian distribution of the pilot's aiming error and homogeneous distribution of the bullet density within the pattern radius.  

Let's have our pilot open fire at a range where he has a 67% chance of having aimed correctly. Additionally, let's assume that if he aimed correctly, bullet density will suffice to give him a 40% chance of a hit on the target aircraft for each bullet fired.

Firing 25 shots from a single accurate 20 mm gun, he'd score (long term average :-) 6.7 hits. That's a number the Luftwaffe considered high enough to kill a fighter reliably.

Now let's increase the pattern: At the range where the pilot can be expected to have his sights on target with a 67% chance only, increasing the pattern size might seem like a good idea. Doubling the pattern size will indeed give our pilot a 96% chance of being on target. However, bullet density within the pattern is down to one quarter of what it was before, meaning that with the pattern right on target, there'll be only a 10% chance of a hit for each bullet.

Firing 50 shots from his new twin guns of reduced accuracy, our pilot will now score (long-term average again) 4.8 hits only. That means by adding another gun and increasing the pattern size to increase hit chances, he's actually decreased firepower to just 72% of what he had before.

Of course, this is only a simplified example. It illustrates some of the factors whose combination determines firepower, though, and demonstrates how apparently logical measures to increase firepower can be foiled by numerical effects.

Regards,

Henning (HoHun)

[gripen]

HoHun,
I thought that 100 was enough   anyway...

First  it should be noted that  normally wing guns were harmonized for most common shooting distance (say 100-200m depending on the AF or pilot or what ever) so in this range (and say 50m more or less)  more armament in the what ever position will give more hits than less armament  in the optimal position. Also this probably covers more than 50% of all combat situation shooting in the case of the average pilot.

Then it should be noted probability of correct aiming was probably much less than 50% specially in the case of the average pilot and at longer range the error was probably partially systematic ie it did not behaved like Gaussian distribution (also other reasons could cause uneven distribution); the gyroscopic gunsight improved shooting very much...

Anyway, if aiming is correct then centerline weapons certainly gives relatively more hits outside and inside above mentioned range (depending on the size of the target and number of guns) but more armaments in the what ever position give better possibilities to get hits.

BTW I checked Galland's book again and at least in the finnish version he states that he thought that two cannons in the wings would have been better than one in the fuselage despite he knew advantages of the centerline weapons.

gripen

[Tony Williams]

There's a parallel discussion about this going on in the Military guns and ammunition discussion forum (see below - "Ideal WW2 Fighter Armament" thread).

Basically, centreline guns were more efficient than wing-mounted ones.  At short range, they provided concentrated fire, whereas wing guns could miss completely, with the two groups of fire passing each side of the enemy fuselage.  At long range, it was possible to angle the cowling or wing-root mounted guns outwards a fraction to increase the hit probability if required; the natural dispersion of the projectiles due to gun/mounting inaccuracy could prevent any gaps in the pattern from forming. Wing guns only achieved a good distribution of fire within a certain range band around the crossover point. Beyond that, you have a dumb-bell shaped distribution with a hole in the middle. You can get around this by setting the pairs of wing guns at different convergence distances, but then you don't have concentrated fire at any range.

Of course, the RAF and USAAF did pretty well with wing guns, but they had to carry a lot more of them to make up for the lack of efficiency, with obvious weight and performance penalties.

Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://website.lineone.net/~a_g_williams/index.htm
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages

[HoHun]

Hi Gripen,

>First  it should be noted that  normally wing guns were harmonized for most common shooting distance (say 100-200m depending on the AF or pilot or what ever) so in this range (and say 50m more or less)  more armament in the what ever position will give more hits than less armament  in the optimal position.

Wing guns work fine at convergence range. They don't work fine short of convergence range and beyond convergence range. Both estimation of range and the execution of the attack ("to aim at a piece of sky that will be full of aircraft when your bullets arrive there after you've fired from convergence range") are additional difficulties not present for centreline armament. This is the reason centreline armement is better for inexperienced pilots at any range.

>Then it should be noted probability of correct aiming was probably much less than 50%

The mechanism is the same for any hit probability. The poorer the aim of the pilot, the more you have to widen the pattern, the lower your bullet density becomes and the lower your probability of kill drops.

(Note the difference between correct aim and probability of hit in my example - random dispersion etc. lowered the probability of hit to just 27% for the centreline case.)

>BTW I checked Galland's book again and at least in the finnish version he states that he thought that two cannons in the wings would have been better than one in the fuselage despite he knew advantages of the centerline weapons.

How about a direct quote then?

Regards,

Henning (HoHun)