1944: Flak Alone Blasts the Allies out of the Sky

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Post by seppalar » 23 Jan 2005 01:04

There is another advantage in using smaller, lighter projectiles, either, as Tony suggests, in sub-caliber ammunition or in smaller bore AA guns - the ammunition is lighter and will fatigue the loaders much less. This means that during long engagements a high ROF can be maintained for a much longer time. I would suggest a gun like Italy's L/50 75mm piece, or even a 65mm gun might have been ideal under such circumstances.

Of course the 75 or 65mm ammo and guns would be less expensive than 88, 105 or 128mm stuff, even requiring less fuel to move them about.

On a critical note: does anyone out there have any evidence that lots of allied airplanes were returning to base after having been hit by heavy AA shels which passed through without exploding? It is possible the Germans were wrong in their analysis and the spike in aircraft losses was really the result of the increasing number of AA guns being concentrated in Germany plus the much increased number of allied aircraft flying over Germany in late 1944 - end of the war.

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Post by Tony Williams » 23 Jan 2005 03:34

seppalar wrote:On a critical note: does anyone out there have any evidence that lots of allied airplanes were returning to base after having been hit by heavy AA shels which passed through without exploding? It is possible the Germans were wrong in their analysis and the spike in aircraft losses was really the result of the increasing number of AA guns being concentrated in Germany plus the much increased number of allied aircraft flying over Germany in late 1944 - end of the war.
The time-fuzed shells had contact fuzes also, so I doubt that was a problem; the inefficiency associated with them was due to their exploding too early rather than not at all.

Time-fuzed AA shells had to explode very close in order to inflict fatal damage. It was common for RAF bombers to make it home despite having lots of small holes in them from Flak bursts.

TW

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Post by seppalar » 23 Jan 2005 21:02

Thanks Tony, does this mean that Lars' original post was incorrect in that double acting fuzes were in service much earlier than late 1944? Before reading this thread I had believed all heavy AA fuzes were double acting.

Are there any lessons which could have been learned from this, ie could anyone at the same or different time have switched to impact-only fuzes and been making a correct decision?

I believe that this is doubtful. To be able to get a direct hit on an aircraft flying at over ten thousand feet altitude one needed a really good idea of where the plane was. I would be surprised if pre-1944 radar or optical rangefinding equiptment could do this.

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Post by Lars » 24 Jan 2005 15:46

seppalar wrote:There is another advantage in using smaller, lighter projectiles, either, as Tony suggests, in sub-caliber ammunition or in smaller bore AA guns - the ammunition is lighter and will fatigue the loaders much less. This means that during long engagements a high ROF can be maintained for a much longer time. I would suggest a gun like Italy's L/50 75mm piece, or even a 65mm gun might have been ideal under such circumstances.
Seppalar,

IFAIK, Italy had two 75mm anti-aircraft guns, neither of which would fit the late-war German demands.

The 75mm mod. 35 had an effective ceiling of 9.3 km. The 6.5 kg shell was fired at 715m/sec.

The 75mm mod. 38 had an effective ceiling of 8.4 km. The 6,5 kg shell was fired at 975m/sec.

Neither gun fittet the German late war needs, IMO. Basically, the choice was between a high reacing shell (75mm/35) or a high velocity shell (75mm/38.). But feel free to disagree.

There was no Italian 65mm anti-aircraft that I know of.

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Post by seppalar » 25 Jan 2005 00:45

Lars, are you sure about your numbers? It looks like you are quoting the maximum ceiling of the mod. 35 and the effective ceiling of the mod. 38. The effective ceiling with impact fused shells will be higher than with timed shells because a longer time of flight is allowed.

While I was suggesting a hypothetical 65mm AA piece Italy did in fact have one; the 65 mm/64 Model 1939 did not enter service but fired a 4.08kg shell at 950m/s see

http://www.navweaps.com/Weapons/WNIT_65mm-64_m1939.htm

While this weapon did not have the performance to hit a bomber at 30,000 feet a higher velocity version with something like Probart Rifling could have been developed. Also a 65mm shell could have been fired from a 75mm gun using a sabot to give a very high muzzle velocity and a very streamlined design. Either solution would yield a cheaper, lighter gun than any of Germany's 88's that would get the job done just as well if direct fire was used. These guns and their ammunition would require much less steel to manufacture and feed and would probably be light enough to be towed by teams of horses - a real consideration in wartime Germany.

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Post by Lars » 25 Jan 2005 16:40

seppalar wrote:Lars, are you sure about your numbers? It looks like you are quoting the maximum ceiling of the mod. 35 and the effective ceiling of the mod. 38. The effective ceiling with impact fused shells will be higher than with timed shells because a longer time of flight is allowed.

While I was suggesting a hypothetical 65mm AA piece Italy did in fact have one; the 65 mm/64 Model 1939 did not enter service but fired a 4.08kg shell at 950m/s see

http://www.navweaps.com/Weapons/WNIT_65mm-64_m1939.htm

While this weapon did not have the performance to hit a bomber at 30,000 feet a higher velocity version with something like Probart Rifling could have been developed. Also a 65mm shell could have been fired from a 75mm gun using a sabot to give a very high muzzle velocity and a very streamlined design. Either solution would yield a cheaper, lighter gun than any of Germany's 88's that would get the job done just as well if direct fire was used. These guns and their ammunition would require much less steel to manufacture and feed and would probably be light enough to be towed by teams of horses - a real consideration in wartime Germany.

Rick Seppala
Rick,

The figures from the Italian 75mm are from the Oxford Companion to WWII, entry "Artillery". One motha****** of a book, 1,000+ pages, which I find is usually reliable.

Good point about horse-drawn guns. But why a 65 mm sabot shot, why not settle for a 50mm sabot shot? IIRC, one single 50mm hit anywhere(!) on a four engines airplane would bring it down, so everything over a 50mm shell is overkill.

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Post by Tony Williams » 26 Jan 2005 09:36

Lars wrote:
seppalar wrote:Lars, are you sure about your numbers? It looks like you are quoting the maximum ceiling of the mod. 35 and the effective ceiling of the mod. 38.
Rick Seppala
Rick,

The figures from the Italian 75mm are from the Oxford Companion to WWII, entry "Artillery". One motha****** of a book, 1,000+ pages, which I find is usually reliable.
I wouldn't trust a very general book to be necessarily accurate about specific technical detail. The difference between 'maximum altitude' and 'maximum effective altitude' is considerable, but only specialist books are likely to make the distinction.

For your entertainment, an extract from 'The Foresight War'. The historian from the present day, Don Erlang, is visiting Liverpool during the Blitz (and the Heinkels mentioned are not He 111s!):

Don and Johnson were walking back to their hotel through the blacked-out city when the air raid sirens began the unearthly wailing that sent shivers of dread up Don's spine. The few people left on the street headed for the nearest shelters, but to Don's surprise Johnson led him in a different direction. 'Something you'll want to see!' He called.
After a few hundred yards they were challenged by a sentry. Johnson spoke quickly to him and the sentry nodded. 'Right-oh, sir. You'll be needing these.' He reached down and held up two Army helmets. Don put his on, his perplexed glance at Johnson lost in the gloom.
'What do we need these for?'
Johnson bent down; 'These!' He held up a light, oddly shaped piece of metal. Don examined it but could make no sense of it.
'You ought to recognise it; you were responsible after all!'
This time Johnson didn't have to see Don's face. He chuckled and said, 'don't you remember some years ago describing the results of some German operational research to do with anti-aircraft fire against bombers?'
'I think so. You mean that time fuzes were a waste of time, so to speak?'
'That's right. Flak fuzes were set to explode the shells at the estimated height of the aircraft, but they had to explode so close to a big bomber to bring it down they virtually had to hit it. The trouble was, the fuzes weren't that precise, so almost half the shells burst before they reached the aircraft. The Germans found that they actually improved their strike rate by fitting simple contact fuzes.'
Don tapped the piece of metal. 'That doesn't explain this!'
Johnson continued, obviously enjoying the rare experience of telling Don something he didn't already know. 'We put that together with two other things you told us about; first, that if a flak shell scores a direct hit it can afford to be much smaller - about five pounds or so; and second, that very high velocity can be achieved by using discarding sabots.'
'But that was for anti-tank guns!'
'Principle still applies. We've designed a high-explosive discarding sabot shell to be fired from the big new four inch anti-aircraft gun; that's the four point seven inch sleeved down. Instead of the usual thirty-five pound time-fuzed shell, it fires a nine pound high-explosive discarding-sabot shell at a far higher muzzle velocity, which improves both the altitude performance and the accuracy, as the time of flight is much shorter. The only problem is that the light alloy sabot which holds the shell in the barrel falls back down again onto the gunners' heads. So we made it to break up into small pieces when it leaves the barrel. It's still advisable to wear helmets, though!'
Don thought for a moment. 'I'm impressed! That application never occurred to me. But don't you lose the morale effect of flak bursts near the aircraft?'
There was a grim smile in Johnson's voice. 'We thought of that as well. The reason the shell is a bit heavier than it needs to be is that it contains a big tracer, designed to ignite some way below the aircraft. There's nothing more off-putting to a pilot and a bomb-aimer than to see the shells curving up towards them – particularly in those German bombers where the crew all huddle together in the glazed nose! Of course, once the radar proximity fuze is perfected that will change matters, but for now this is doing pretty well.'
Ahead, there was a gleam of light reflecting from purposeful-looking machinery. They walked up to what was gradually revealed to be an anti-aircraft gun installation. After a few words with the crew, Johnson picked up something long and heavy and pushed it against Don's chest. He grasped the big case of a 4-inch round. At the business end, he made out the short, sharp point of the shell protruding from the cylindrical sabot.
'Any time now!' Johnson said. 'Stay and watch the fun!'
This was not Don's idea of fun but he could hardly make his own way back. One of the crew, who was wearing headphones, stiffened suddenly then called out, 'radar has them; they're coming right over us.'
'Load!' The command was immediate. Don heard the double metallic clang of the shell-case being flipped into the loading tray followed by the power rammer driving the case up into the breech. A loud electrical humming came from the mounting, which slewed suddenly, the gun elevating.
'Remote power control,' said Johnson, 'the nearby gun-laying radar provides height, speed, range, bearing and heading gen which are fed into a calculating machine which works out where the guns should be pointing. This then controls the gun aiming by signals sent over a land line. Each radar controls a battery of four guns, plus a searchlight.'
On cue, the searchlight snapped on just as the air raid sirens finally wound down. Don could faintly hear the distinctive, uneven drone of the German bombers at high altitude. The searchlight probed through the misty air, but Don could see nothing.
'The lights are more for morale purposes than anything else. On a night like this, they're not likely to spot a high-flyer, and the big Heinkels come in at well over thirty thousand feet.'
A brilliant flare suddenly illuminated the sky in the direction of the docks. Almost immediately, other flares became visible much further north.
'At least one of their marker planes got through,' commented Johnson. 'The others are probably our decoys. The Germans keep changing their flares and it's a constant battle to keep copying them. To confuse matters further we've even built a 'decoy city' a few miles to the south; lots of fuel pipes to produce spectacular fires.'
Don was reflecting on the irony of the reversed roles, with the Germans and the British both applying experience originally culled from the Allied bombing of Germany in 1944/5, when the gun fired with an ear-splitting crash. Even before he had recovered, the empty shell-case was automatically kicked out, the next round slammed into the breech and the gun fired again. Less than three seconds later, the third shot followed. Don looked up into the sky; far above, he saw a red flare curving gently away as it faded into the night. Much later, a brief flash indicated where the shell had self-destructed as the tracer burned through.
The noise seemed to go on for hours, the crew frantically running to and from the ammunition store, throwing shells into the mechanism as the gun relentlessly blasted skywards. Five times, Don saw a brighter glare high above them, followed by a tumbling fire as a stricken bomber fell to earth.
Sudden silence. As his ears recovered, Don heard the dull thuds of explosions from the docks, saw the glow of fires in the sky. Around him, the gun crew were draped in postures of exhaustion.
'Twenty minutes,' said Johnson judiciously. 'Just keeping us on our toes. They'll be back at least one more time tonight.'
Don walked back to the hotel in silence.

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Post by Tony Williams » 26 Jan 2005 09:40

And for the sake of balance, an extract from a later section of 'The Foresight War':

The Unteroffizier surveyed his crew with satisfaction, all poised in their allotted places around the FlaK. The Kanonier 1, whose job was to lay the gun in azimuth, K2 who set the elevation, K3 who loaded the gun and K4, 5, 6 who passed the ammunition. He looked around the platform of the huge concrete FlaK tower, raised high above the city in order to give an unrestricted field of fire. His gun and the other three of the battery were grouped around the Kommandogerät 36 director, which still relied on optical height and range setting in view of the intense jamming of the radar directors by the attacking Eloka aircraft.
The guns were the new 11 cm FlaK 43, developed from the 10.5 cm FlaK 39 by boring out the rifled barrel to create a smoothbored cannon designed to take the long, fin-stabilised Peenemünde Pfeilgeschoss arrow shells. These were not only fired at a much higher velocity of around 1,200 metres per second, but because of their shape did not slow down as quickly so reached the altitude of the bombers much sooner, greatly assisting accurate shooting.
The techs had been right about the fuzes, he thought. At first, the idea of using contact instead of time fuzes had seemed like madness, but as the techs pointed out, even the beautifully engineered clockwork fuzes were only accurate to half a percent. This meant that the vast majority of shells were bursting too high or low to do any damage, and in any case had to explode very close to the B-17s in order to bring them down. It was more effective to rely on direct hits, especially as this enabled smaller shells to be used which could be fired at much higher velocity. There had been some talk of tiny radar fuzes which would explode shells only when they were close enough to damage the target, but these were apparently all being reserved for the new anti-aircraft missiles just entering production.
The Unteroffizier looked hopefully at the sky. The cloud seemed to be clearing. Just a bit more, and the oncoming bombers would get a warm reception!

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Post by Lars » 26 Jan 2005 11:51

seppalar wrote:Lars, are you sure about your numbers? It looks like you are quoting the maximum ceiling of the mod. 35 and the effective ceiling of the mod. 38. The effective ceiling with impact fused shells will be higher than with timed shells because a longer time of flight is allowed.
Rick,

How much higher would the effective ceiling of impact fused shells be compared to time fused shells, and why?

I have info on a better range for the 75mm gun (12.5 km ) but that´s when used as ordinary artillery, not as flak.

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Post by Lars » 26 Jan 2005 18:34

Tony,

The Pennemünde Pfeilgeschoss was not a flak-weapon, IIRC. Are you saying the PP could have been a flak weapon if only given a smoothbored large gun, or did the PP need a modification in the flak role?
Last edited by Lars on 27 Jan 2005 10:22, edited 1 time in total.

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Post by seppalar » 26 Jan 2005 23:53

Lars,
the ceiling of an AA gun is quoted three ways. The maximum is how high the gun can throw the shell at 90 degree elevation. The practical ceiling is the height a shell can reach at the maximum time setting of its fuze - the powder train fuzes used by virtually everyone well into WWII had a maximum burn time of about twenty to twenty-five seconds which means a shell will explode before it gets to the maximum ceiling. The practial ceiling with such a fuse is about two thirds of the maximum ceiling. The third ceiling quotation is the effective ceiling - "this is best explained as the maximum height at which a gun can engage a target for a length of time sufficient to allow a reasonable number of rounds to be fired - usually twenty to thirty seconds. This again, is lower than the practical ceiling, a matter of simple geometry, by perhaps three to five thousand feet, depending on the gun's rate of fire and the engagement time you choose to stipulate."
The Guns 1939-45, Ian V. Hogg p. 83 (The rest of the above is paraphrased from the same page.)

The above would give a significantly higher effective ceiling for impact fuzed shells, because burn time would no longer be an issue and because rate of fire would increase.

Like Tony said, don't trust most mass publication books on military matters, I think the problem is that while the authors know their stuff the editors and typesetters don't . I have even found this to be common in books by authors like Hogg and others who definitely know their stuff, heck, Tony's website has a list of corrections as long as his arm.


BTW, how do you guys do that 'box' thing around your quotes?

Rick

[/i]

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Post by Lars » 27 Jan 2005 10:20

Rick,

Thanks for the explanation. While I get the three different ceilings, I´m afraid you lost me in the conslusion below. Can you develop this a bit more?

"The above would give a significantly higher effective ceiling for impact fuzed shells, because burn time would no longer be an issue"

To get the box-quotes, you press the "quote" button in the right upper corner of someone else´s post.

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Post by Lars » 27 Jan 2005 14:01

Tony,

Thanks for pointing out the Pennemünde Pfielgeshoss for me. I hadn´t given it a closer look before that. The original PP was 73 inches with 130mm warhead with a sabot ring at about the middle of the arrow-shaped missile and was fired from a large railway gun (31cm?). AFAIK, the Flak-PP to be fired from a smoothbored 105mm gun was ready before the war was over but it wasn´t put into production as there was no available production capacity. Shell velocity was 3500 ft per second. The Flak-PP to be fired from the 105mm gun must have been of a rather low calibre possibly 30-40mm, perhaps not enough to bring down a four-engined bomber in one hit.

Wouldn´t the sabot-PP fired from the 105mm gun be the "perfect" V-weapon also? It should be possible to shell Dover across the Channel with sabot shells from Calais. Perhaps it would even be possible to shell Folkestone and Canterbury also. This would be much cheaper than the V1 and certainly the V2.

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Post by seppalar » 27 Jan 2005 19:40

Lars wrote:Rick,

Thanks for the explanation. While I get the three different ceilings, I´m afraid you lost me in the conslusion below. Can you develop this a bit more?

"The above would give a significantly higher effective ceiling for impact fuzed shells, because burn time would no longer be an issue"

To get the box-quotes, you press the "quote" button in the right upper corner of someone else´s post.
Thanks for the explanation of the quote Lars.

The ceiling goes up because: 1) a fuze does not limit the height a shell can travel and 2) a guncrew can fire more rounds per minute if they do not have to set the fuzes. Number 2 is important because the definition of effective ceiling is based on firing a certain number of shells at the target - higher rate of fire means a higher effective ceiling. Number 1 helps because many shells could not even reach their effective ceiling because they would explode first. (Because the fuzes had a gunpowder train in them we call the time until a fuze detonates "burn time".)

I must say that what surprises me the most in this thread is that the Germans ever opted for a solution that made things simpler! Previously they had switched to clockwork fuzes to get a higher practical ceiling but, as Tony pointed out, these were still fairly inaccurate. Given the German preference for ever more complex inventions I am quite amazed that any evidence to ever convince them that a simpler solution was better.
:D

I hope this helps. BTW if you look at the velocity figures you quoted for the Italian AA guns it should be clear that the higher velocity gun should have a higher ceiling.

Respectfully yours
Rick

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Post by Tony Williams » 27 Jan 2005 22:36

Lars, the 11 cm PP shell in my novel was an invention - a scaled-down version of the PP artillery shell fired from the 31 cm K5 Glatt railway gun (which could range to 150 km).

When it comes to destructive effect, don't be fooled by the small diameter of the PP shell. It was several times the length of a conventional shell of the same diameter, and held far more HE. The PP shell for the K5 (only 12 cm in diameter) actually contained 25kg of HE, compared with 30 kg for the full-calibre 28 cm shell fired from the conventional K5 (E).

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