Flak-How does it truly work?

Just wondering if I could pick the brains of a few experts about some nagging questions I have regarding Anti Aircraft Artillery, or Flak. Talking large scale stuff here, not 20mm or 37mm or 40mm...

1) How do you get the shells to go off at the right alititude? Was it a timing mechanism incorporated into the warhead of each shell? If so, how long did it take to set it to the proper altitude?

2) For the US, I know they developed proximaty fuses for their 5 inch guns that worked wonders in the Pacific against the kamikaze aircraft. Can anyone explain how it exactly worked? It would seem to require a high degree of computing ability due to the short time involved regarding 2 objects moving together at high rates of speed.

3) Was Flak an effective use of men, munitions, and armament? I once read (if I recall correctly) that pre-war German thinking felt that it would require 50 88mm or larger shells or so to bring down a bomber. Reality soon showed it required over 10,000. (Again, final figure may be off due to fuzzy memory). How much more effective would it have been to have those shells and guns employed in anti-tank roles? Could the addition of those thousands of guns on the Eastern Front from 1942-1944 have made a real impact?

 

Good point, 9thWaffenSS. It's something I tend to take for granted without ever thinking how it works !

As I understand it, the effectiveness of 'Flak','Ack-Ack' etc went in tandem with the development of radar. During the 'Blitz' on Britain, radar development was in a very early stage and the 'Ack-Ack' was woefully ineffective.

But by 1943/44, the German 'Flak' defences were equipped with efficient radar. This would give precise data of enemy aircraft position and height, etc. This information was processed through a 'Predictor' ( the American called it a 'Director') which combined this information with other factors such as muzzle velocity, ambient temperature, wind direction, etc. This would determine a coinciding position for shell and aircraft; giving the necessary bearing, fuze setting and gun elevation. This is obviously very complex and 'dead-time' was a constant problem ; that is the time taken for the gunner to set the fuze by hand, load and fire which will nearly always vary.

The 'proximity fuze' moved the game ahead considerably. To put it very simply, the fuze contained its own tiny 'radio transmitter'. The fuze sends out a signal as it flies through the air; detonating upon receiving an 'echo' back from a target. Again, this is based on the radar concept.

Your last point is very good. Was it worth it ? I really don't know. Certainly, as mentioned above, AA during the Blitz was useless. It served to reassure the populace that 'something was being done'. A lot of Allied aircraft were lost to heavy flak over the Reich, but as you say, think of all those guns, shells and men.

What does everyone else think ??

[ 12 August 2002, 09:22 AM: Message edited by: Martin Bull ]

 

Good stuff...
Martin, you mention the time taken to set the fuse for AA rounds- was this done by hand, or did the Predictor system handle the fuses? That's one point I'm not clear on. Also, I wonder about the reliability of the fuses...
The Proximity fuse was HUGE as far as anti-aircraft fire goes. Martin hit it right on- a proximity fuse consisted of a very small, simple radio transmitter. The transmitter sent out a signal, and as soon as it recieved a signal back from a pre-set distance, the round would detonate. This made AA fire vastly more effective, as the shells would now detonate only feet away from the target.
Proximity fuses were in fact such a big deal, that the US did not even use them immediately, I'm pretty sure. When they were invented, I believe in late 42, the US did not want to use them for fear of one being captured. They figured the fuses would be more useful to Japan and Germany, both of whom were consistently being attacked by allied aircraft.
And on the question of more AA... to some extent, I'd say more AA fire would have helped both Germany and Japan. Since early on the idea was just to throw as much Flak up as possible, more guns would have probably meant more kills. And on the manpower issue, it would have been a tradeoff for Germany at least- more men manning FlaK batteries=less damage to germany's industry. An even bigger issue would have been had the Germans had invented the proximity fuse. Had this happened, the allied bomber offensive would have been far less effective, if even possible...

 

This is interesting stuff - I've been browsing around the 'Net on this.

I may be overestimating the importance of radar a little, certainly for the Germans. Although the Wurzburg A radar was developed for AA use, results proved disappointing so it seems that German flak batteries relied mainly on the Kommandogerat Optical Predictor for each 4-gun battery working in close conjunction ( at night ) with searchlights. They then relied on sheer firepower with heavy use of the dreaded 'box barrages' fired by multiples of up to 40 guns. Automatic fuze setters were used as an 88 could fire 15-20 shells per minute and even the 128mm could manage 12 per minute.

When I say 'sheer firepower', in January 1944 20,625 flak guns were protecting the Reich, and even a German Flak officer estimated 4,000 x 88mm shells were needed to down one bomber.

As for MORE Flak - in December, 1944, German Flak is said to have fired - wait for it - 3,175,000 shells !

 

So Martin- it seems according to those numbers, more Flak would probably have been useless overkill...
And we know the germans were NEVER guilty of anything like that...

I have read before (can't remember where) that the Radar used by the germans was generally inefficient. Maybe that explains the ridiculous ammo-kill ratio. By the time the Brits had better radar, I wonder what their ration was? Or was the battle of britian basically over by that point.
Come to think of it, did any other nations use FlaK in anywhere near the quantity Germany did? I can't think of any...

 

No - as I mentioned before, throughout the entire Battle of Britain period, British anti-aircraft was almost totally useless.Later in the war, German aircraft were almost totally left to nightfighters.
Then came the V1s, and AA was much more effective against these, and, I believe, the proximity fuze was used again.

[ 12 August 2002, 04:29 PM: Message edited by: Martin Bull ]

 

Found this on a site...

The German Flak arm was also being strengthened by increasing the size of the 88 mm light batteries from 4 guns to 8. To guard the more important targets Grossbatterien comprising 2 or 3 of the enlarged single batteries were created (up to 40 heavy flak guns) firing rectangular patterns of shells known as box barrages that proved deadly. Each battery, large or small, was controlled by a single predictor which meant that up to 18 guns might engage one bomber at a time. The firepower also increased as larger calibre guns were introduced including a 105mm weapon and the largest of all a massive 125mm gun.

In 1944 Flak accounted for 3,501 American planes destroyed, 600 less than planes lost to enemy fighters in the same time period. Constant demand for front line troops for the German army meant that many of the flak crews included elderly men, schoolboys, and even POWs. Heavier flak guns gradually appeared mainly the 105 mm (4.13 in) FLAK 38 and the 128mm (5 in) FLAK 40. The 128mm FLAK 40 consisted of two barrels 3 ft apart on a single mounting. German Flak accounted for 50 of the 72 RAF bombers lost over Berlin on the night of March 24th, 1944. An incredible 56 bombers were destroyed or crippled by flak during a B-17 raid on Merseburg in November of 1944.

A true proximity fuse or variable time fuse was never developed by Germany despite extensive efforts to do so. Allied planners estimated that German FLAK would be about three times more deadly if they had proximity fused shells
The guns were grouped in fours with a predictor (a device used to estimate where the aircraft would be by the time the shell reached it and thus provide information as to where to aim). The searchlights were sited in threes with a sound locator which, as its name implies, located the position of an aircraft by fixing on the sound of its engines. The range of the sound locators was about 6,000 yards but, in view of the time taken for the sound to reach the instrument, the calculated position of the target could be up to a mile behind its actual position, a discrepancy which had to be allowed for in aiming the guns.

When the flak batteries pinpointed an aircraft the guns were fired in salvoes designed to burst in a sphere of 60 yards in diameter in which it was hoped to entrap the target. Each gun, usually of 88mm calibre, could project a shell to 20,000ft and could knock out an aircraft within 30 yards of the shell burst. However, the shrapnel from the explosion was still capable of inflicting serious damage up to 200 yards.

In daylight the predictor crews followed the aircraft by telescope but at night the sound locators directed the searchlights (which had a range of 14,000 yards in clear weather). However, by night or day, the effectiveness of the flak arm in this early period was severely curtailed by clouds.

 

Martin

"Totally Useless"? Don't forget Civilian Morale! It may have been ineffective in shooting down aircraft in the Blitz but was a bolster to the civilians who were heartened by their guns firing back: after all they were not told how ineffective it actually was.

Jumbo

 

Thanks for all the info, guys, I appreciate it.

For the Germans, it still seems like a lot of effort for land based guns to be effective. Up to 18 guns aiming at one bomber seems like a tremendous volume of fire poured onto a single target. And even at 4,000 rounds per aircraft brought down, that still seems like a tremendous misappropriation of resources and effort.

Not saying I have a better alternative, just that it all looks very inefficient on the surface.

And I agree, while planes did fall to flak, I wonder how much of it was done as a "civilian pacification" effort-"See, we're doing all we can to keep the bombers away"...

Can you just imagine another 15,000 88's or better on the Eastern front?

Thanks again, everyone. Flak was something I knew existed, but didn't really understand too clearly.

 

9th W SS

I think there is a lot to be said for the pacification of civilians. Certainly German cities got very possessive about "their" Flak, especially the rail-flak which perambulated around the country.

I think it is easy to underestimate the effect of these outwardly impressive guns on the civilian population. After all, strategic bombing for the RAF was about breaking German morale, so anything that boosts that morale has to be a good thing.

Jumbo

 

Good points on the morale issue, Jumbo. Imagine how this must have effected germany though- keeping in mind Goering's "if one bomber appeared over germany" claim. In this case, it could have had almost an opposite effect- Goering had pledged that noone would bomb germany, but by 43 his claim had clearly failed. Would not the FlaK guns simply remind germans how foolish Goering's promise was?

Great post, RedBaron. In fact, which website? I'd like that bookmark. One small thing though- I wonder if the 128s were only used in double mounts? I've seen one of the double 128s at Aberdeen- WOW! Ive also read though that two sets of four 128s (total 8) were used in the Zoo Tower in Berlin.
One other interesting thing I've read (can't remember where)- apparently the 88 was actually more effective than the 128. Seems the 128 had loading problems, and while it had a higher theoretical ceiling, the maximum EFFECTIVE ceiling was actually less than the 88. I'll see if I can find my source tonight...

 

Jumbo - see my first item under this thread for the 'useless' qualification ( didn't want to go on repeating myself-myself-myself...)

( Later ) Didn't mean to be unduly harsh on British AA, Jumbo. But reading General Sir Frederick Pile's book, 'Ack-Ack', he mentions that the 'kill ratio' during the Battle of Britain and early part of the Blitz was one 'bird' (sic) per 6,000 shells. This improved from early 1941 to one per 4,100 thanks to improved radar and better inter-service co-operation. Pile makes it very clear that they were there to shoot German aircraft down - civilian morale-boosting was an incidental by-product.

[ 13 August 2002, 12:48 PM: Message edited by: Martin Bull ]

 

Damned, I should have taken this iBook to my trip...

Well, no, there were 128s single-mounted as regular guns. I have seen pics of it.

Jumbo is right about the AA guns and their effect on the morale, in the Battle of Britain and the battles over the Reich.

And I think that they were not useless. Even with the radars and more technology they were not as effective as they were supossed to be. By themselves, but along with fighters, radars, etc. they were quite effective. And I think that if we would have made a little push on it, to fly over the Reich would have been deadlier. But it is true that oftenly the AA units had to be used as field artillery and even infantry, and the AA men were replaced by women or prisoners... That gave those weapons less effectiveness...

But if there would not have been any hostile air-attacks on Germany, all those guns could have been used in AT or field artillery roles. And I think that could have made some difference.

Ah, it's nice to be back!

 

Read a recent magazine article on London Flak, concentrated largely on 'what goes up must come down' and includes a story of one returning AA shell that actually passed between a couple sleeping in bed!

Seems that the Guns were not always such a morale booster as the 'blitz-savvy' citizens of London realised how rarely they brought down a plane and how much damage they did to the city. There are personal accounts that the main reason for taking to the shelters was to avoid ack-ack splinters, windows being blown in by blast and even a tale of a unit being asked to move as their blast was cracking toilets across one estate. One welsh Royal Ordnance factory was hit by a returning shell in March 1944 and exploded, leading to 9 killed.

A report into an attack on 17th/18th January 1943 found that 20%-27% of dead or seriously wounded could be directly attributed to 'friendly' AA (this 20% figure seems to also apply to contemporary studies of raids on Pompey and Coventry).

The rough conclusion (while admitting we'll never really know) is that of 60,595 UK civillian deaths during ww2, using a worse case scenario of 27%, it's possible that c.16,360 were a result of their own defences.

I don't know enough to come to any conclusion on the 'worth' of flak, either in direct terms or in relation to morale but it's a very interesting subject and, as ever, more complex than it first appears.

Cheers,
Adam.

 

To answer the original question there are basically two methods for large guns to fire on aircraft: Aimed fire using a director and predicted fire using what is called a "box barrage."

The first method uses either an optical rangefinder or radar to determine the target aircraft's altitude, range, speed, etc. This is fed into an (for WW 2) electro-mechanical computer system that cranks out the necessary time for fuzes, the gun lead, etc. This information is fed to the guns electrically and automatically shows the pointer and trainer where to aim the gun in the battery. The US M2 90mm was a bit more advanced with on-mount power and automatically was slaved to the predictor in normal use.
The loaders then place the shells to be fired nose into a automatic fuze setter on the mount. This presets the shells to the proper time setting. The shells are then loaded and fired at the target.

The second method is the box barrage. Here, the normal optical or radar tracking systems are either not available, not working (cloud cover or jammed), or for some other reason cannot be employed. Instead, the battery director simply feeds their best guess as to the altitude and position of the target into the computer. Their guess is designed to mark out a particular "box" of sky in front of the expected path of the target.
The battery is then ordered to fire into this box filling it with flak. The expectation is that the target will have to fly through the box of fire. This method is extremely wasteful of shells using as many as 10 or more times the number predicted aimed fire would usually for about a tenth of the results. It is basically a last resort.

And, yes, all that flak produced alot of shell fragments falling. But, only the larger chunks really represent a threat to those on the ground. This is because these spent pieces of shrapnel are falling at the speed of gravity not with the velocity they had when they exploded. Therefore, their speed is much lower and this makes them less dangerous to those on the ground.
The same is true of bombers. The US found that flak that was high generally caused some damage to bombers but was far less likely to shoot them down than flak that was low. This is due to the same effect. In high bursts the fragments tended to lose velocity and fall on the bombers where the low ones were relying on initial velocity.

 

Great thread! Very informative.

 

I think the guns would of been better off pointing instead in the skies, horizontally, at a metal machine.

 

Here's an example of a box barrage late in the war where the Germans experianced overwhelming jamming and could not use optical ranging:

A US 720 bomber raid was run on Hamburg on 10/25/44 where the aircraft were flying above 9/10ths + overcast and bombing on BTO radar. They were fired on by 44 heavy flak batteries that expended 24,416 shells in a matter of minutes primarily in predicted box barrages as few batteries could locate targets on their radars due to heavy jamming and chaff. This massive barrage shot down 1 (one!) bomber.
The rate of ammunition expenditure could not be maintained and orders were issued prohibiting such barrages except in the most extreme circumstances. A side effect was that this also created a extreme shortage of artillery and even small arms ammunition for the army. German industry simply could not produce enough ammunition to keep up with use.

 

Flaks primary purpose was to protect. While shooting down enemy aircraft accomplished this it could be effective without doing so. Flack could disorder formations, decrease accuracy, and cause bombers to bomb from unfavorable angles or altitudes or with less favorable techniques.