A calculation Flak vs. B-17

[dov]

Hallo

I found a statistic about the German Flak in WW2. The result is so absurd, that I think it can not be true:

The Quartermaster General of the Air Force calculated a consumption of 16,000 rounds with the “8.8cm Flak 36” and 8,500 rounds with the “8.8cm Flak 41” for the downing of a four-engine bomber. The 10.5 cm Flak 38 required an average of 6,000 rounds and the heavy 12.8 cm Flak 40 3,000 rounds.

That means: To get a B-17 down you must shoot up 86,7 tons!

And please consider: The bomb load of a B-17 and 86,7 tons of grenades which will fall from the sky too!

This is idiotic ! Blank nonsense!

Happy modelling

[Graham Boak]

I doubt that it is far wrong, and a sign of the sheer wastefulness of war.  It was said that after the peak of London Blitz winter of 1940/41, there was more damage caused by AA shrapnel than there was from German bombs.  Similar comments were made in response to General Pike's plans for an intense AA barrage to stop V2s.

 

Remember that these would all be explosive shells, arranged to explode at specific heights, so there would be showers of metal shards rather than tons of grenades.  So roofs would suffer but buildings would not have been blown down nor firestorms started.

[Bozothenutter]

This seems like data taken out of context....

Makes more sense (possibly) if you know the number of B-17's shot down, number of flak rounds fired, numer flak guns, etc, etc....

[ckw]

I don't know for sure, but for things like this I try and apply some sensible figures to see if the numbers have any logic to them.

 

So lets consider the 88 alone

 

100 guns around Berlin seems low, but go with that

realistic rate of fire - 15 RPM

duration of bombers over Berlin - say 30 min

 

That gives you 45,000 88mm rounds alone for a 30 minute raid ... and I'm sure the real numbers were much higher

 

I have read that one of the aims of the bombing campaign was to divert German production into AA defences

 

Cheers

 

Colin

[GordonM]

Surely it depends over what period you're extracting this data? Early war flak was less accurate, by the end radar laying and proximity fuses improved the accuracy. Also by the time the 8th Air Force were putting thousand bomber raids it's reported the formation took over an hour to pass a point on the ground. 

[Graham Boak]

The Germans did not have proximity fusing.

[Jure Miljevic]

Hello

I vaguely remember reading somewhere about it, and IIRC correctly, an average number of grenades, necessary to down a heavy bomber was even higher. It must have been another study. However, FLAK barrage, which is another way of saying guns are firing blind, is a wasteful business. And many times there were not even any aircraft in vicinity and guns had been fired to boost morale of civilians. No wonder Germans started developing Enzian, Wasserfall, Rheintochter and other surface-to-air missiles. Cheers

Jure

[Vlad]

This does not seem as outrageous as you suggest. Numbers for US Navy 5"/38 fire are also in the region of a thousand rounds fired per aircraft shot down, even with VT fuse. And these guns were firing at small and flimsy Japanese attack aircraft, not B-17s that are known to be able to take a pounding.

[Giorgio N]

The page linked her contains a number of statistics for several types of AA guns installed on USN ships in WW2, and may be interesting to understand what kind of ammunition consumption was needed to shoot down an aircraft

 

https://www.history.navy.mil/research/library/online-reading-room/title-list-alphabetically/a/antiaircraft-action-summary.html

 

Of course these describe quite a different situation, where some aspects are in favour of the attacker and others in favour of the defender. The kind of attacking aircraft were very different and the attack profiles were also very different, so it's not directly comparable. Still, shows that downing an enemy aircraft can easily require hundreds if not thousand of rounds

[alt-92]

Where does the 86.7 (metric) ton come from?

Because 88 shells were 20lb/9.x Kg - so that's 9500+ shells which makes it a low estimate, even

 

 

[Jamie @ Sovereign Hobbies]

14 minutes ago, Giorgio N said:

shows that downing an enemy aircraft can easily require hundreds if not thousand of rounds

 

And this nicely sums up why the battleship was obsolete by WWII

[Doc72]

The numbers are really scary with hindsight. But keep in mind that not all of these shells were fired in vain or without effect. The purpose of Flak was also to make bombing less accurate by forcing the bombers to fly higher, faster and to take evasive maneuvers. 

Still, it is always staggering to realise how inprecise the whole AA effort was. Proximity fuses would have made a great difference, but this is one of the technological fields were the Allies clearly had an edge.

BTW: Consider that the vast majority of flak shells never hit a bomber while the vast majority of bombs dropped by those bombers never hit a target of military/economic importance. The whole thing was enourmously wasteful (but war in general is, of course).

[Denford]

Remember that Churchill was able to tell Stalin (when it was far too early to invade) that the Second Front has already been opened.  The anti-aircraft guns could otherwise have been deployed on the Russian front.

Others might comment on the 'cost effectiveness' of this.

[fubar57]

German Flak guns and ranges....https://masterbombercraig.wordpress.com/bombing-operations/flak/

[Giorgio N]

31 minutes ago, Doc72 said:

The numbers are really scary with hindsight. But keep in mind that not all of these shells were fired in vain or without effect. The purpose of Flak was also to make bombing less accurate by forcing the bombers to fly higher, faster and to take evasive maneuvers. 

Still, it is always staggering to realise how inprecise the whole AA effort was. Proximity fuses would have made a great difference, but this is one of the technological fields were the Allies clearly had an edge.

BTW: Consider that the vast majority of flak shells never hit a bomber while the vast majority of bombs dropped by those bombers never hit a target of military/economic importance. The whole thing was enourmously wasteful (but war in general is, of course).

 

The same could be said of many other weapons in war: the vast majority of small arms ammunition for example end up without hitting anything but walls and trees. Even artillery shells more often than not just make holes in the ground without hitting anyone or anything of value.

Of course there's the important aspect that a round fired without hitting anything can still be very useful ! As you said, the presence of flak barrage alone affected the effectiveness of the bombers, and in the end this is a result. Some bomber crews used to drop their bombs early as a result of the fear of flak and again any single event of the kind was a victory for the gunners. Same as in ground combat where ammo is often expended to keep the enemy heads down or artillery barrages are used to deny access to certain areas. I may not hit anything but it's still useful. Actually, it's more than useful, it's often vital.

 

[Giorgio N]

Another slightly OT observatoin on the relative importance of actually hitting an attacker in air defence, a video from one of my favourite Youtube channel:

 

https://www.youtube.com/watch?v=AirRXwbo8Mg

 

The author is a US tank officer that explains things in a wonderfully simple way. He makes perfectly clear how, when defending from an air attack, hitting the attacker is not the aim of the defender, his aim is to survive the attack by making things difficult for the attacker. And closer to the end of the video, he also mentions how the same is also true for the attacker, even if he doesn't hit his target he can still accomplish his mission by the simple fact of making the target's life more difficult...

[dov]

Hallo

8.500 rounds 8,8cm-Flak 41 / 10,2 kg per shell / this is the easy calculation. Maybe the weight is more precise from any other data, but this is my consideration.

In any way, absurd.

For the Navy, much easier, since the holes in the water will get easy repaired!

Happy modelling

 

[wombat]

This is why Milo Minderbender worked out it was much more cost efficient for each side to contract with the other to bomb themselves...

 

also of note in the majority of RAF bomber command raids casualties on the ground were exceeded by aircrew casualties. Every so often a mass event like Hamburg put a massive thumb on the scale.

[Hook]

Remember those enormous volumes of triple A the Iraqis threw up on those 1991 CNN broadcasts, for no hits at all..?

 

Cheers,

 

Andre

[Nev]

"Waste is the currency of war, and it must be spent for military objectives to be achieved"

 

General Dwight D Eisenhower.

[Geoffrey Sinclair]

Weight is one way to measure resources, the other is cost.  There is also the damage the guns did even if they did not bring the aircraft down.

 

For the effective accuracy of the  guns, "window" and the active jammers interfered with the flak radars whenever deployed, but at least by day you can still see the bombers, hence the RAF flak damage rates to the Ruhr by night in September 1944, 2.5%, but 36.7% by day.  Above the better allied counter measures it appears another reason the German flak declined in effectiveness was the use of partially trained crews and the failure to provide enough fire control equipment to all the guns.  Add the smoke screens generated to hide the target and the allies were flying in worse weather.  However the Germans learnt to range on the H2X transmissions, which were the pathfinder aircraft.  They also found that firing contact only fuse shells increased rate of fire and number of kills.  So in 1944 the 88s were requiring around 16,000 rounds per kill, the 128 mm 3,000 rounds per kill.  In the first 20 months of the war the heavy guns, 88mm and above were scoring a kill per every 2,805 rounds, in late 1943 it was every 4,000 rounds, the wartime average was apparently around 5,000 rounds per kill.

 

At 16,000 rounds of 88 mm fire per kill in 1944 the ammunition cost per kill was US $512,000, so over twice the cost of a B-17, but then add the cost of the trained crew.. 

 

Another cost is the guns wear out.  It seems the flak units were losing something like 380 88 mm guns per month in combat and to excessive wear during 1944.  With maybe cost wise 8 to 10 3.7 inch / 88mm / 90 mm guns to the B-17.

The most comprehensive set of figures for naval AA performance I can easily find is the set relating to the USN in the period 1 October 1944 to 31 January 1945, broken down into Kamikaze and non Kamikaze attacks, then by 5 inch common shells, 5 inch proximity fuse, 3 inch, 40 mm, 1.1 inch, 20 mm and 0.50 inch.

 

The following table is weapon or shell, (kills / ammunition use per kill for Kamikaze) / then for non Kamikaze actions.

5 inch common / (19/1,162)  / (33.5/960)
5 inch proximity / (24.5/310) / (20/624)
3 inch / (6.5/710) /  (4/752)
40 mm / (114/2,272 /  (46/3,361)
1.1 inch / (1/2231) / (no kills/4,764)
20 mm  / (62.5/8,972) / (50.5/7,152)
0.50 inch / (2.5/28,069) / (3/15,139)

 

To emphasise the way these are a guide the figures also give monthly average expenditure per kill, so for 5 inch common in non Kamikaze actions the figures range from
748 in October to 2,601 in November 1944.  The Kamikaze actions vary even more so, minimum 493 in December 1944 and maximum 2,675 in January.

 

It is interesting to note the way 5 inch proximity fuses were much better against Kamikazes nearly 4 times as good on average than the 5 inch common but only about 1.5 times as good for conventional attacks, showing the speed of the Kamikaze attack was stretching the fire controls.  The way the Kamikazes came closer to the ships helps explain the improvement in 3 inch and 40 mm kill rates, but the reverse is true of the 20 mm and 0.50 inch presumably for the reasons mentioned in many references, by the time the
lighter guns were in action the need was to destroy the aircraft, not bring it down and they were too light.

 

Note there are plenty of reports of USN warships being hit by friendly AA fire.

[Geoffrey Sinclair]

16 hours ago, wombat said:

also of note in the majority of RAF bomber command raids casualties on the ground were exceeded by aircrew casualties. Every so often a mass event like Hamburg put a massive thumb on the scale.

Plenty of the early Bomber Command raids saw more aircrew killed than people killed by the bombs.  Not the later ones.

 

Richard Sorge in the Other Price of Hitler's war claims 410,000 civilians killed and "hundreds of thousands" missing.  The 410,000 figure appears to be German civilians killed, then add 23,000 police and civilians working in the military, 32,000 foreign workers and PoWs plus 128,000 displaced persons, total 593,000.  This total is from the post war investigations of the German Statistical Office.  Late in the war air raids were killing large numbers of foreign workers, they had no or bad air raid shelters.

 

The really big fires killed people in what were normally well protected shelters, by the mass heat and/or consuming all/most of the oxygen.  This did not happen on anything like the needed scale for smaller fires, with some notable exceptions like fires in coal stores near shelters.

 

Death tolls, Hamburg around 40,000, Dresden 25,000, Pforzeim 17,600, Kassel (October 1943) 5,599 plus 3,300 missing as of end November, Darmstadt, 8,433 reported dead but many deaths probably not reported, present day city guide says 12,300 dead.  So if all the fire raids are correct, around 105,000 deaths, Which leaves the remaining deaths to be divided up caused by the 657,674 long tons of Bomber Command bombs, less the fire raids, and the 557,643 short tons of bombs dropped by the USAAF heavies on Germany, plus the allied medium bombers, fighter bombers and Soviet aircraft.

The averages cover an immense variation in bomb lethality. Ploesti at low level against quite large targets should have been a precision strike but if some of the bombs hit air raid shelters or the shelters were inadequate it could mean considerable deaths on the ground.  However raids away from the big cities with their warning and shelter systems were much more lethal on average.  Hence why the USSR had about as many killed in air raids as Germany.  If you are living in a small community near something tactically
important what chance you have no real warning or shelter the day the bombers turn up?  And most communities were tactically significant in and of themselves, the buildings.

 

Looking though the notes for Germany over the course of the war it was around 1 death per 2.2 short ton of bombs dropped on the country, or about 0.45 deaths per short ton.

 

In WWI about 300 metric tons of bombs dropped on the UK killed about 1,400 people, or about 4 deaths per short ton.  (See where the idea of 1930's  "modern" bombing effects came from?)

 

In WWII about 70,000 metric tons of conventional bombing killed 51,509 civilians in the UK, about 0.66 deaths per short ton of bombs.

About 3,600 tons of V1s killed 6,184 people, 1.5 deaths per short ton
About 1,100 tons of V2s killed 2,754 people, 2.2 deaths per short ton.

 

The 1,000 bomber raid on Cologne in May 1942 dropped 1,697.8 short tons of bombs, killing either 469 or 486 people including 52 military personnel, or about 0.3 deaths per ton of bombs.  This was a new high for deaths in a single raid.

 

The Mosquito only raid on Hamburg on 30 September 1944 dropped 65.5 short tons of bombs, 103 people were killed including some trampled to death in a panic, 1.6 deaths per ton of bombs.

 

Two USAAF raids,

The 5th April 1943 strike on Antwerp, 104 B-17s of which 82 were rated as effective, dropping 245.5 tons of bombs on the industrial area, as the primary target, 936 civilians killed or around 4 deaths per ton of bombs.

 

When the 15th AF attacked rail facilities in Marseilles on 27 May 1944 over 1,500 French civilians were killed, along with 500 houses destroyed. There had been an attack in December 1943.  According to the French report on the raid the population discounted the chance of further attacks and did not take good precautions.  Some 72 bombers attacked, dropping 177.5 short tons of HE bombs versus the French estimate of 130 aircraft attacking, so about 8.5 deaths per ton of bombs.

 

There are two factors in play here,

1) There is a good chance many civilians presumed the bombers were going somewhere else and so did not take cover, this would push the death toll up, like at Antwerp.

2) The USAAF was under strict instructions to only attack clearly identified targets in the low countries, which meant attacking in the best weather.  This would push the death toll down.

 

The raid that caused the Hamburg firestorm dropped 2,707.2 short tons of bombs, causing somewhere around 15 deaths per ton.

The raid that caused the Dresden firestorm dropped 2,978.4 short tons of bombs, about 8.4 deaths per ton of bombs.

[Graham Boak]

The economic cost of the bombing campaign runs to much more than the aircraft cost and that of their crews.  They required airfields to be built, using up valuable agricultural land that could otherwise have been productively used, and additional foodstuffs imported.  These airfields required manning, the men requiring training in newly-built training bases.  The fuel is required to be imported on tankers and transports through U-boat infested-waters, and then transferred by a new pipeline across the UK to the bases in the South East. Ditto their bombs and ammunitions, except they can't travel by pipeline but on railways, contributing massively to the over-use of the railway system that ended with it being severely run-down.  The use of green pigment in aircraft camouflage meant that it was banned from Army and Navy use: which presumably cost something in substitution and additional losses through the results being less efficient: although this would be incredibly difficult to measure.  All of this effort was directed away from productive use to fund the economy and hence pay for the war.  In a more direct manner, the diversion of more educated and ambitious servicemen meant a drop in the overall quality of the Army's personnel, and after D-Day a failure to maintain the strength of the Army on the Continent.  Montgomery's plans for the advance were thus crippled by shrinking means.  This was while unemployed airmen were sitting around unused in the UK because the suspension of the deep penetration raids had lowered the loss rate.  

 

Similar features can be seen elsewhere of course: the growth of the SS and other elite units in the Wehrmacht left the average German unit considerably weakened in the important junior NCO ranks.  It has been mentioned how the diversion of resources to flak guns meant fewer AT guns and tanks, although I must admit not seeing a simple relationship between the two, and feeling that a simple ton for ton exchange is too simplified.  A more complex relationship must exist, though probably too complex for reasonable analysis.

[Graham Boak]

On the British side, there is an excellent study AA Command, by Colin Dickinson for English Heritage.  This is one of a series of books on British defences. from decoys to the anti-Diver campaign.  Although the numerical references in it are more to the number of guns deployed, there is a quote from two months in early 1941 of 56 and a half aircraft destroyed for 3195 rounds per bird.  In the Little Blitz of 1944 33,854 rounds were fired on the night of 21/22 March, for 8 successes. "Seldom had so much AA ammunition been expended by so many on so few."  Which rather palls in comparison with the comment above of 16000 rounds per B-17.

[wombat]

There’s a strong argument that all the many compromises elsewhere made necessary by the strategic bombing campaign only made sense at the time the commitments were initially activated, when Britain “stood alone” and no other means of victory was available (however tenuous the likelihood of strategic bombing securing victory alone may have been). By the time the lead times of production had played through the strategic picture had altered to the point where the need was no longer there, but now we had to find a use for what we had. Did anyone except Bomber Harris still believe in the concept by, say, 1943, but how could you reverse the strategy? You can’t really use a Lancaster for close air support...