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How accurate was an allied bomber during WW2?

Discussion in 'Western Europe' started by Christian123, May 6, 2014.

  1. Fred Wilson

    Fred Wilson "The" Rogue of Rogues

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    Wish I knew the source for this:

    "In the fall of 1944, only seven per cent of all bombs dropped by the Eighth Air Force hit within 1,000ft of their aim point; even a fighter-bomber in a 40 degree dive releasing a bomb at 7,000 ft could have a circular error (CEP) of as much as 1,000 ft. It took 108 B-17 bombers, crewed by 1,080 airmen, dropping 648 bombs to guarantee a 96 per cent chance of getting just two hits inside a 400 by 500 ft area (a German power-generation plant.)"

    http://www.ww2aircraft.net/forum/aviation/bombing-accuracy-799.html
     
  2. GunSlinger86

    GunSlinger86 Active Member

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    The B-17 had the new Norden bomb sight that was one of the most accurate in the World for that time. A British documentary said it had almost pinpoint precision.
     
  3. Otto

    Otto No More Half Measures Staff Member WW2|ORG Editor

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    I seem to recall a thread by Adam (Von Poop) about rockets firing at a huge (100 yard?) trench of water or something similar, and only a tiny percentage of hits were registered. I can't imagine how difficult trying to hit a tank might be.
     
  4. Slipdigit

    Slipdigit Good Ol' Boy Staff Member Patron   WW2|ORG Editor

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    It varied throughout the war.

    Early in the war, it was not uncommon for the Germans to unaware of the target was for Bomber Command. To quote John Ellis (Brute Force, pg 171) "What to the Air Staff was a systematic strategic offensive was to the Germans merely a random bestrewal of HE devices most of which, obeying the laws of chance expectation, fell harmlessly into the German countryside."

    In 1941, after examining photos of 100 separate raids, War Cabinet Secretariat member, Mr. D.M. Butt concluded only one in four aircraft attacking Germany got within five miles of the target, and only one in ten when attacking the Ruhr. These numbers were only of those actually attacking the target. The actual number of aircraft actually getting to target (as opposed to attacking it) was only one in five getting within the 75 square miles around the target.

    In 1942, Captain Harold Balfour wrote a memo to the minster he worked for, Sir Archibald Sinclair (Parliamentary Under-Secretary), where he stated that only about 10% of the ordinance dropped actually fell within a target area.

    As aids to finding the target came into use, the number getting to the target improved but by Autumn, 1943 numbers hitting the target were still abysmal. The USAAF, just beginning to drop increasing number of bombs found that the average error was 450 yards in good weather and 1200 yards in poor. For the night bombers, the error was "more like three miles." But even with so-called pin point bombing from 20,000 feet or above, only about half the bombs landed within a quarter mile of the aiming point. Unless the target was circular and had a 3 mile or greater radius, more than 50% of the bombs landing in the surrounding fields.

    By June, 1944 around 50% of Bomber Command's bombs dropped on oil refineries fell within 500 yards from the center of the target. Bear in mind that we're talking about a 1000 yard diameter, roughly 2/3 mile.

    All number come from Brute Force, John Ellis, 1990. If you want specific pages, let me know.
     
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  5. Fred Wilson

    Fred Wilson "The" Rogue of Rogues

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    Here I think: http://ww2talk.com/forums/topic/4761-dive-bombing-vs-rockets/
     
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  6. gtblackwell

    gtblackwell Well-Known Member Patron  

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    The Norden bombsight may well have been the best in the world but that only says all the others were worst. As for pinpoint accuracy that is probably propaganda, perhaps to justify crew casualties or placate civilian complaints. Accuracy , let alone pinpoint, was an elusive thing.

    Thanks, Jeff, good post.

    Gaines
     
  7. LJAd

    LJAd Well-Known Member

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    Maybe a better question would be : how accurate was a bomber 75 years ago (historical perspective!) and the answer would be : not much (the report of 1941 was not much positive).

    On the second (but not asked) question :how accurate is a bomber today :the answer is : still not much,but more .
     
  8. ptimms

    ptimms Member

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    I can't remember where but I saw a stat that a salvo of 8 rockets from a Tiffie had about a 1-2% chance of scoring one hit! So 12 Typhoons firing all their rockets would average about one hit. Of course against a soft target like a truck or horse drawn cart you don't need a direct hit with a 24 pound (I think that's the warhead weight) rocket.
     
  9. phylo_roadking

    phylo_roadking Member

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    What a lot of commentators have failed to notice over the years was that in addition to ordnance that simply missed its target for a variety of reasons and killed more German farm livestock than Germans the effort Bomber Command was puting into....INTENTIONALLY doing just that! Bombing the German countryside...

    A sizeable percentage of raids in late 1940 and early 1941 (tho' thankfully the wasted effort was tailing off fast by1941...) were attempts to torch German forests and woodland with incendiaries! First using "normal" incendiaries, while a specific "incendiary wafer" was developed for the purpose - it would be fair to say that the effort expended on this brainchild of the MEW, the Ministry of Economic Warfare, was totally wasted!
     
  10. Slipdigit

    Slipdigit Good Ol' Boy Staff Member Patron   WW2|ORG Editor

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    The Norden was fairly accurate. I cannot remember the standards, but it could deliver the bomb surprising close to the target..er...uh..um...under pristine conditions such as found on a bomb range in front of a Congressional delegation. Over an actual defended target, well, the operator had to be rather skilled.

    By 1944, the 8th AF had abandoned individual toggling of the bomb load, deciding instead to have a lead bombardier for each bomb group. There were concerns that some of the bombardiers were not accurate enough. When the lead bombardier dropped his bombs, the rest of the aircraft dropped theirs. The theory was if he hit, then the all would. But, if he missed they all, uh, missed also.

    B-29s experienced very poor bombing accuracy in Japan due to the extreme jet stream winds at high altitude that the bomb sights could not allow for. By March, 1945, Curtis LeMay changed bomb loads and tactics. Instead of high explosive bombs, the aircraft carried incendiaries and flew at medium altitude, which just happen to be be higher than the range of small caliber Japanese AA guns and below the range of Japanese large caliber AA guns.
     
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  11. gtblackwell

    gtblackwell Well-Known Member Patron  

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    As luck would have it I was sitting at my drawing board this morning, yes I still work full time at 74 !, and "World at War' came on the Military Channel, the episode was "Whirlwin" The Bombing of Germany 1939-44.

    Nice program, not like the most recent stuff. there was a WW2 B&W film of an officer pointing to an aerial photos of Schweinfurt and the target was the ball bearing complex, very well shown. He pointed to a specific building on the far bend of the group of buildings as the bombing point. They did a good bit of damage at great cost and repeated at great cost.

    I do not doubt the accuracy of the Norden, it was precise, complex and had compensation for altitude, speed, trajectory, wind, etc. but when gravity bombs drop it seems a myriad of unintended activities influence it's path. It is just the nature of the beast and transends the sight.

    As a child I still remember "Norden bombsight" in many discussions of adults and the pickle barrel analogy was invariably included. I do not think it was quite that good.!!!
     
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  12. KodiakBeer

    KodiakBeer Member

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    Off and on during my life I've gotten into long distance shooting. That may seem like a very different thing, but it's not at all. All of the same variables are present. With a black powder cartridge like the 45-120, the bullet drop at 1000 yards is in the hundreds of inches - 600 inches? And even a mild wind can move it left or right by several feet. Within a thousand yards, the wind can change directions several times, or zero wind at the shooting point might be 5 or 10 mph out within the range, or vice versa. So even with the most carefully weighed slugs and powder charges, a perfect rifle bore, precise iron sights and a 4 ounce set trigger you have to be both talented and lucky to hit the iron at 1000 yards.

    All of those same elements are present in dropping a bomb from 25,000 feet. Your planes speed is probably never what it is measured to be because a head or tail wind will throw off the measurement. The wind direction at 25,000 will almost certainly change, perhaps several times, before it hits the earth. Even your altitude is not a given, since temperature and humidity affect that. And all of these mechanical devices that feed the info into the sight have their own minor calibration errors. Then, you get into the bomb itself. Nobody is carefully weighing and sizing these things like a distance shooter does with a slug. They are metal cans with fins welded on and each one is going to have it's own unique drift pattern.
    Then, then, let's look at the mechanical and human errors - there is no 4 ounce "hair" trigger with a known lock time. Even if the bombardier gets everything right (ignoring the errors in what is fed into the sight) his signal has to jump through a couple of mechanical relays and drop the bombs off a mechanical rack that is faster or slower depending on the temperature or the maintenance of that device - when was it last greased? Is the grease congealed because of the temps? Are there worn pins, bearings, some nut or bolt too tight or loose?

    Everybody else in the formation is just following his lead, with their own slight delays and mechanical differences.

    Then these rather poorly designed missiles drop though space, each with their own slightly different trajectory through various winds pushing them off track by some distance, to hit the earth and explode. And remember, to destroy an actual hardened cement or steel structure, you pretty much need a direct hit. 50 yards isn't going to do it. I suspect a lot of that aerial footage of bombs walking through a factory complex or rail yard, didn't do nearly as much damage as you'd think.

    If you stood on your roof and tossed a handful of pea gravel into the air to land in a teacup 15 or 20 yards out in your lawn, how many would land in the cup? How many handfuls would you have to toss to land one in that cup?
     
  13. phylo_roadking

    phylo_roadking Member

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    ...or you do what the RAF eventually did - come up with a bomb that undermines a concrete structure so that it falls into the hole you've created.

    The SOE reckoned that there was one or two critical machines in each factory or plant that if you took it out it stopped the entire production line until replaced - or that in a "tool room" served other machines in the plant. They reckoned their quite small demolition devices could take out such point-critical machines in the hands of a saboteur...even a blow from a large hammer splitting its brittle cast iron base would be enough to take it out of commission.

    So how much damage could a bombing raid do to a production line...as opposed to the mere fabric of the factory or plant? ;)


    Chosen by a rail transport expert - plenty. Especially if a few or a few dozen miles behind the front line of an ongoing campaign or offensive...and there's no more than one or maybe two at most alternative rail lines to route men and materiel to the front.

    Once again, it doesn't actually need to DO much - but rail yards, etc. weren't exactly "hardened" - you weren't just trying to destroy track - it would takes day to replace switch and signalling gear, especially big signal boxes controlling whole segments of network ;)
     
  14. KodiakBeer

    KodiakBeer Member

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    I used to work as a track laborer, then a switchman/brakeman when I was 18 - 21 years old. Tracks and manual switches can be replaced in hours. It's amazing too, how very complex signals can be sent just using a lantern at night or flag during the day. For example, a short arc (like an upside down U) meant 5 and two arcs meant 10 and then short vertical movements indicated 1's. It's like Roman numerals where two short verticals prior to the arc meant three and after the arc meant 7. A horizontal swipe across the waist meant "cut." In effect, the conductor could signal me at night from hundreds of yards away to cut the last 7 cars on track 2, then the next 4 cars onto track 7, then pick up the 7 cars on track 2, and on and on and on. A short circular motion over the head followed by a fast downward swipe was a "highball" - we're leaving, jump on the train.

    Anyway, I doubt a bombing raid on a rail yard did much beyond delay things for a few hours. You'd just route around bad tracks and so on, and you wouldn't need electric signaling gear to do that. I suspect low level fighter-bomber raids actually targeting trains were a lot more devastating in terms of stopping supplies from getting to the front.
     
  15. phylo_roadking

    phylo_roadking Member

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    But you do need alternative routes to be available etc. and preferably ones that didn't require hours and hours of extra travel...and through 1944 into the last full year of the war - increasingly the Germans were being forced to travel by night anyway...especially after June 6th 1944....which of course reduces the time they can use the network safely anyway.

    ...or "closing down" alternative routes - as medium bomber raids knocked holes in the network that increasingly couldn't be diverted round.

    Here's the thing though...

    ...yes, the rail crew themselves can handle the train - but you can't run/timetable for an entire network segment that way if a major junction box is knocked out ;) And those repairs etc. in the Occupied countries weren't being done by the Germans - think they were being done at top speed? That vital tools and spares didn't go missing, etc.? ;)

    Paralysing a rail network is a job done on many levels all functioning at the same time - but apart from the gross damage done by an enemy, all those other levels, the "petty" levels of minor resistance and sabotage, they have to be geared just at the right level so that there's no "ultimate sanction" by the Germans....remember Papa Bull in The Train? ;) ...what's important is the cumulative effect of all the minor sabotage and go-slows.

    I do agree that the sort of damage that daylight/night strategic bombing tried to do to rail networks through MOST of the war wasn't great, due to accuracy, the "distributed" effort of having large numbers of bombs scattered across a wide area, etc. - all the things we've been discussing - but don't forget the Allies finally took the RIGHT decision and let 617 Sqn loose on the French rail network ;) Both in "dedicated" 617 operations....and larger Lancaster raids in April, May and June 1944 where 617 Sqn "marked" the targets using everything from 1,000lb bombs right up to 12,000lb "cookies"! A whole slew of major French rail junctions and marshalling yards were hit during the campaign - Aulnoye, Rouen, Paris-Noissy, Paris-Ste Chapelle, Laon, Acheres, and Somain...but one stands out from all the others - the legendary Paris-Juvisy raid of April 18/19th 1944...

    Here's the "before"...

    [​IMG]

    Here's the "after"....!

    [​IMG]
    [​IMG]

    As you can see - THAT damage wasn't going to be eradicated in a few hours! ALL loco sheds and workshops were destroyed, most of the cross-over rail bridges, and more than half the rolling stock in the yard at the time. More than 92% of the tonnage dropped fell within the target area...

    ...and because of early warning slipped to the French Resistance, very few French civilians were killed!

    To repait the damage from THAT raid - you're talking about days of clearing the wreckage alone, followed by days or far more likely weeks of filling in the ground damage and re-grading/ballasting....then actually rebuilding the junction could easily use up available stocks of rail, sleepers, ties, switchgear....so what happens when the second, or third...or fourth junction is hit? ;)

    Sadly, this "before and after" pic of the Aulnoye raid of April 27/28th 1944 is small - but once again you'll get an idea of the level of damage done...

    [​IMG]

    Here's a better-sized version of the "after" pic - as you can see, it's virtually not there any more! And that's just a week after Paris-Juvisy - how many raids doing that level of damage could the French railway system absorb and repair at any one time???

    [​IMG]


    There's also the example of the Saumur railway tunnel raid by 617 Sqn three nights after D-Day, when they dropped the long tunnel blocking one of the last unblocked rail lines into Normandy ;) And ripped up several hundred yards of track.
     
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  16. gtblackwell

    gtblackwell Well-Known Member Patron  

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    KB, I started to include my bench resting information to explain bombing accuracy but your explanation is much better. In 1960 I has a 22-250, a fine cartridge then and now. I only shot at 300 yards but a 50 plus grain projectile going roughly 3800 fps was strongly influenced by temperature, wind, trigger pull, humidity, etc., in more or lesser degrees and greatly by me. Did I get my end correct. At 25,000 feet I think a direct hit would be amazing. Good look to9 the guys trying to bomb on me. I believe the Tirpitz was an unlucky ship even if it were at dock.

    Gaines
     
  17. KodiakBeer

    KodiakBeer Member

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    Phylo, yes they could certainly mess up a switching yard with a good concentrated bombing attack, but I still think you underestimate how quickly rail can be laid. Even in the old west, as much as 8 miles of track were laid in a day on virgin prairie. In Europe, with road networks and trucks and short distances to supply points, it wouldn't take long at all. As for timetables, I know that late in the war the Germans simply moved trains in one direction between certain hours and in the opposite direction during other hours. Delay, yes. Stoppage, no.
    The Germans moved an incredible amount of troops, armor, supplies from the east to the west in November, 44, to stage the Ardennes offensive. They did that in complete secrecy and (mostly) on schedule despite the skies over Germany being completely dominated by allied air.

    Gaines, yes, we certainly agree on this. All of the same variables apply. I would guess that less than 1% of those bombs dropped actually did real damage. Even when everything went right and the load went into the target zone, it still took a lot of luck to actually get a direct hit on a key structure.
     
  18. lwd

    lwd Ace

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    I think near the end of the war that US and British heavy bombers also had the capability of bombing by radar. I'm not sure if it was utilized much though but it was potentially much more accurate and allowed attacking in bad weather and at night without pathfinders.
     
  19. mcoffee

    mcoffee Son-of-a-Gun(ner) Patron  

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    The 15th AF began having H2X Mickey ships in the formations in April 1944. The 8th had them slightly earlier, but don't remember first usage. H2X was developed from the British H2S and RAF usage preceeded AAF use. Accuracy of PFF attacks improved as time went on but was not great. Best PFF accuracy was achieved as a combination of visual and radar bombing, i.e. bombing through the smoke screen at Ploesti, etc. If the course from IP to target could be flown visually most of the way, the Mickey operator had a much better chance of locating the aiming point on his screen, and some good results were achieved. Bombing entirely by PFF was generally not that accurate.
     
  20. phylo_roadking

    phylo_roadking Member

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    Yes, laying rail is the quick part...but before that - when its a network node I.E. a major junction that has been destroyed as opposed to just a straight section of line...there's the actual clearance to be done, the area re-graded etc BEFORE railcan be laid - plus the the issue of how much useable...."kit"?...the French railway system actually contained - and it's something I've never actually seen commented on. And I'll not even mention the problem with getting steam cranes to any derailed rolling stock or locos across a disrupted network!

    As in - if you replace a huge junction like Paris-Juvisy.....how does replacing all that eat into stocks of everything that makes up a switchable network - points, switch and signalling gear etc.? And when you've done it for half a dozen or a dozen major junctions in a short time - what about the next one? or the RAF returning within days to one of the others?

    As for transporting materiel for repair around by truck....trucks moving in Western Europe were, after June 6th 1944, fair game in the main...!

    Pus - I don't think you'll find many Allied commanders on the ground complaining about a mere delay in German troops and arms reaching a specific location... ;) Look how long some of those "delays" could be...http://en.wikipedia.org/wiki/2nd_SS_Panzer_Division_Das_Reich#The_Battle_of_Normandy_and_fighting_in_the_West_.E2.80.93_1944
     

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