How accurate was an allied bomber during WW2?

Please leave a source if possible

More specifically the bombers used by the RAF and USAF against Germany right after the Battle of Brittan

Type of bombers:

• B-17
• Lancaster

( I dont know if this is all, but just strategic bombers used by the allied against German infastructure)


If you have night and day statistics that would be great


(Also, when I say accurate I am the distance from the intended target such as a German ball bearing factory)

 

I have no idea how this blog thing works so I thought that was how it was done. If that somehow annoyed you I am sorry, and

"yes I edited it after you posted the post"
-You can use that as proof if needed

 

It varied with time, region, altitude, bomber type, and opposition. The standard measure of accuracy for bombers is refered to as CEP (circular error probability). Typically it's measured in a linear scale. I.e. a CEP of 50 feet means that there is a 50% chance of a bomb dropped by the stated plane type under stated conditions landing within a circle with a radius of 50 feet. Searching by year and plane type with CEP in the search string will get you some numbers. Here are a few I found:
http://en.wikipedia.org/wiki/Norden_bombsight
States the Norden bomb sight had a cep of 75 feet when tested but that was in the New Mexico desert I believe. Actual combat accuracy wasn't that good. The same article mentions the 1943 combat CEP of planes equiped with it as 1,200 feet.
There are a fair amount of numbers here:
http://www.warbirdsforum.com/topic/5358-low-altitude-bombing-raids/
On page 223 of http://www.ibiblio.org/hyperwar/AAF/Hansell/Hansell-6.html they mention a CEP of 1,600 feet and a bombing altitude of 26,000 feet. On page 243 a CEP of 1,250 feet is mentioned.

At one point I remember seeing more detailed reports, i.e. by plane, bombing altitude, and year. Can't seem to find it now though.

 

And target location and locating, navigation, weather (wind/cloud cover), quarter of moon, target marking etc.

Indeed - and as many pilots later joked, if only the Germans had mounted pickle barrels in top of factories they'd have hit them, NO problem! Several years ago now I read a VERY interesting article comparing the period Norden and Sperry bombsights, and the Sperry was apparently judged to be sightly more accurate...but not at the sort of high altitudes that the RAF were still bombing at with little or no low-level target marking; a useful comparison was the 20 or so B-17Cs sent to the RAF...but fitted with Sperrys...and at the high altitudes...up to 30,000 feet!...the RAF attempted to bomb from the temperature affected the Sperry's gyroscopes. So in RAF service the B-17 was pulled from service as a bomber and some were sent to the Middle East, and the rest used as anti-submarine aircraft where they were far more successful.


OP, one major issue with dropping ordnance from the sort of altitude that accuracy demanded was that shrapnel/bomb fragments could and would reach back up and damage aircraft. A 500lb bomb for example could loft bomb fragments 5,000 feet in the air!

It should also be noted that the Germans didn't enjoy brilliant accuracy either until the Revi bombsight was superceded...and they experienced ALL the same issues of spread of ordnance when dropped from medium and high altitudes. It was so prone to bad calibration that Luftwaffe FW200 Condors on maritime anti-shipping patrols...who depended on accuracy to be able to straddle a target with bombs and if not hit it at least get one close enough to stove in hull plating...carried a concrete bomb for dropping and calibrating the Revi at the start of every patrol sortie!

Just recently I came across the Station Operations Record Book for RAF Lympne for the months of July, August and September 1940...and on one medium altitude raid on the airfield, the two lines of bombs that fell across the airfield was spread out over two miles on the ground!

 

Sub question: generally, how many waves were used per bombing run?

 

I think there's even a picture of a low level bombing attack in the Pacfic (not dive bombers) where the bomb itself bounced high enough to hit the bomber. I think that's one reason they went to parachute bombs for low level attacks there.

 

I think it was very target dependent and perhaps dependent on how you define a wave. In Europe 8th AF bombers had a primary and a secondary target and on occasion would default to "targets of opertunity". In Europe I think for high level bombers they usually dropped by squadron but several squadrons could be fairly close together (often at different altitudes) and attacking the same target around the same time.

 

Yes, very target dependent. I can speak better about 15th AF procedures, but they were similar to the 8th. On large targets, the entire 15th AF might have the same target with Wings attacking at 10 minute intervals. (nominal 4 Groups per Wing, 4 Squadrons per Group) Other times each Wing might have its own target. Still others might have targets assigned per Group . Groups would generally be separated by 1-2 minutes. Squadrons were fairly much nose-to-tail.

Bomb aiming would vary by target also. Each Group would have either 3 or 4 sections (nominal Squadron) in the formation, depending on time frame. Bombing by PFF would generally have a PFF ship as the lead of the 1st and 3rd sections, and the 2nd and 4th would drop on the 1st and 3rd lead. Visual bombing would generally drop on the lead of each section. On targets such as bridges, the formation would break into trail of 4 ship boxes and bomb by box.

 

This has the making of a good thread. Tnx!

PS:
I like it when people edit posts to clarify them. Irks me at times when they do not. There are many posts here that could be improved by touch up editing.

Sub Questions. - Master Bomber / Marker Accuracy.

H2S Bombing Accuracy
H2X Bombing Accuracy
Gee Bombing Accuracy
Gee-H Bombing Accuracy
Oboe Bombing Accuracy
Pathfinder Bombing Accuracy.

What was average creep back?

Good overviews here.
Operations Analysis in the U.S. Army Eighth Air Force in World War II By Charles W. McArthur

By Dr, Tuttle's USAAF Report 11 July 1943 - (Geoffrey Tuttle. Correct?)

Lindemann's 1941 report was the critical moment. His analysis showed that only 1/5th of bombs fell within 5 miles of the target.

 

Graph of the gradual 1941 - 45 improvement in night bombing accuracy here:
http://www.nationalarchives.gov.uk/education/worldwar2/theatres-of-war/western-europe/investigation/hamburg/sources/docs/7/

Any particular reason why it would exclude Berlin? Anyone?

 

Another question I have always had.

How accurate were (Typhoon etc) rockets? What technical aspects were involved?
I can not imagine proximity fuses in them, but who knows?

 

When talking of strategic bombing we should not just consider the equipment's accuracy, there have been multiple instances where the bombers utterly failed to identify the target and bombed something else, IIRC the first civilian casualties from non tactical bombing where when a RAF bomber dropped his bombs by mistake over neutral Denmark in September 1939 and Swiss cities were hit more than once. In cases like this CEP is obviously irrelevant.

 

The distances involved for post-raid photo recce by day to assess damage!

Lindemann's Report involved re-investigating over 600 post-raid pics that had only been cursorily examined....or not at all AFTER him, there was far more emphasis put on post-raid analysis.

It's also worth remembering however that up until then NOONE was going to do much on the sort of targets the RAF was trying to hit, from the altitudes they were flying at...and the penny-packet raids they were flying! Squadron-sized raids, or more than one squadron, didn;t become common until very late 1940....until then flights were being sent here, flights there - and very often mecahnical failure rates meant that only half or three-quarters' a squadron's strength would be rostered for ops. I recently read Ward and Smith's history of No.2 Group Bomber Command....and the size of raids and the numbers of aircraft mustered in late 1940 and 1941 was a shock!

The first real, concentrated bombing the RAF carried out was the "bargebusting" handful of big-sortie number raids in September 1940....and then back to quite small raids on "normal" targets until the campaign against the Kriegsmarine at Brest at the end of 1941 Which was very much a "desperation" effort - it was WELL against the findings of Lindemann....as the pathetic results for the effort expended against Brest showed!

 

Awful. TRULY awful...

I found this out many years ago entirely by accident. I spent a wargaming weekend at a hotel run by the sainted Peter Gilder...the man behind Hinchcliffes 25mm miniatures...and he had been a National Service RAF pilot, being called up JUST after the end of the war. It turned out he trained on Typhoons and Tempests before they were withdrawn...and he said the first time he cleared his racks he got the shock of his life...

Frm HIS point of view in the cockpit, the rockets seemed to head off at random like the spokes of a wheel!

Concrete-headed practice rounds, "live" rounds...they were all the same...that's why you see film of pilots firing them in pairs, clearing the racks all at once meant their rocket plumes upset the path of other rockets in the cluster, the carrier rails flexed, all sorts of problems!

 

My impression was that an experianced pilot had a decent chance of hitting a ship as long as it didn't have much in the way of AA and he could close to fairly short range. Tanks on the other hand were almost pure luck.

 

Thanks for the input. This is one of those areas where I would like to expand my knowledge.

 

According to the National Museum of the US Air Force on the first Schweinfurt raid 10 % of bombs hit within 500 feet of the intended target.
60 planes paid for that information.