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"BOMBER STREAM DIMENSIONS and DENSITY" Topic


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1,429 hits since 22 Nov 2014
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Skarper22 Nov 2014 5:55 p.m. PST

I'm trying to figure how close an RAF bomber would be to another in the stream?

I have a figure that a Bomber Stream could be 70 miles long and 4000' deep – but nothing for width.

They have to be narrow to fit through a single 'box' so that is giving me an idea but if anyone can help pin it down a bit more precisely I'd be grateful.

Thanks in advance.

Great War Ace Inactive Member22 Nov 2014 6:01 p.m. PST

It must have been variable. The Bloody Hundredth in the US 8th Air Force was famed for taking higher casualties. The myth was started that the Krauts were picking on the 100th because of a grudge (how this came about is even more arguable). The real explanation of the 100th's higher than average casualty rate was that for a long time they did not fly in as tight of formation as other bomb groups, thus they were more vulnerable to fighter attack….

Mako11 Inactive Member22 Nov 2014 6:13 p.m. PST

It could vary greatly, depending upon the period, wind conditions, etc.

One reference I've seen mentioned the same 70 miles long, and 5 6 miles wide.

Later in the war, during the Berlin Raids campaign, the RAF tried to minimize the time over the target, in order to thwart the Tame Boar defenses over the cities. I suspect that's where the 70 miles long is derived from, since most attacks were conducted in the space of about 20 minutes, or so, flying at about 210 MPH.

On one very windy night, apparently the weather report was incorrect, and the Jetstream was blowing hard, so the bombers got spread over a 70 mile wide frontage on the way to the target, and 150 miles in length. On their return leg to their bases, the bombers got spread out over 130 miles. They still attempted to drop Window, but in those conditions it didn't work very well, if at all. Supposedly, the bombers were pretty easy for the Tame Boar fighters to locate, when they were spread so wide, since Window was ineffective at masking their positions then.

I've also seen reports of up to 12,000' in altitude separation, though suspect most of that is due to the Mosquitos flying very high, as either decoys, or to do target marking.

I think 4,000' to 6,000' deep streams would be more common.

For some of the really early raids, the bomber pilots could choose their own takeoff times, and routes, so there wouldn't really be a stream per se, during those, which would aid the Himmelbett defenders a bit.

wrgmr122 Nov 2014 6:20 p.m. PST

My understanding was that it was very long and not so wide. The idea being continuous bombing kept civilians awake so they could not work the next day. Also so emergency services would not so easily move about and perform their tasks. This tactic also accommodated bombers taking off every minute or so spacing them out, with no real formation.

I have read about bombers almost colliding in the night. Most likely taking off from various airfields and moving into the stream.

ChrisBBB Inactive Member23 Nov 2014 4:18 p.m. PST

There is a nice graph available here which shows the % of RAF bombers dropping their bombs within 3 miles of the target, from February 1942 (<25%) to April 1945 (>90%) (% is the average for the preceding 6 months):

link

It doesn't tell you how many of the aircraft missing by 3 miles dropped short or long rather than wide, but it gives you a clue to stream width. If 90% of bombers in the last 6 months of the war got within 3 miles of their target, then you know at least 90% of aircraft were in a stream not more than 6 miles wide. Earlier in the war, before aids such as Gee, Oboe, H2S Mk II were introduced and before the RAF got fully adept in their use, presumably aircraft wandered a little wider.

Chris

Bloody Big BATTLES!
link

troopwo Supporting Member of TMP23 Nov 2014 4:44 p.m. PST

It can really vary depending on target, numbers and year of the war.

In '42 you might have had 400-600 bombers spaced over the target for up to three hours or more.

By '45 you could have the same 400-600 bombers all over the target in a 45 minute timing.

They got better, 'more compressed' with practice and experience.

The US XXth air force using B29s against Japan had the same identical experience from their first night raids to the later raids, including daylight streams!

As a side note, by late '44 the RAF used identical streams for a few daylight raids with the same 'compressed times' as their night raids. Most crews were absolutely horrified to find how many other aircraft were around them and how close.

Many things made the time over the target a variable.
Type and size of target.
Bomb load, HE or incendiary.
Flak defenses.
Fighter defenses, radar, sound and observer integration.
Ability of the ground defense to overcome bombing, ie the proficiency of the fire services and the speed of starting fires.
et cetera,,,

Also, not all bombers actually followed the same stream.
Different groups may have differing streams and even altitudes to avoid congestion and collision. EG these 300 bombers followed this stream and at 17,000 ft with the following squadrons bombing at their own times. Another three or four hundred bombers from another group followed another stream pattern at 15,000 ft, with the following squadrons having their own individual bombing times.

Sometimes you might even have different targets within the same raid. Sometimes an MC would direct and correct the bombing.

Planning for a raid was an endless task.

troopwo Supporting Member of TMP23 Nov 2014 4:49 p.m. PST

If you are expecting some kind of a fixed distance, forget it.

Usually a pilot would only know if he was following too close to another bomber was when he suddenly lost control when he blundered into another bombers slipstream.

Mako11 Inactive Member23 Nov 2014 4:56 p.m. PST

That's an excellent resource, Chris.

Note, the percentages exclude Berlin, which was the subject of a major, months long bombing campaign, and which was never actually effectively dealt with. The RAF conducted 19 major raids on the city, but due to its large size, and other technical and tactical reasons, it was never really attacked very effectively, even with the "modern" bombing aids available at the time.

Due to high bomber losses, and the need to focus more on the support for the D-Day landings, the bombing campaign against Berlin was called off.

A lot of the bombing was far wider than 3 miles from the target, especially in the early to mid-war period, due to incorrectly forecast winds, poor navigation, decoy fires and target marking by the Germans, etc. In some cases, bombers (even with OBOE gear) might miss their targets by 30 miles, or more, even fairly late in the war (the Berlin Raids).

Of course, as mentioned, their overall effectiveness improved greatly over time, but on many raids, luck and sheer volume of attack aircraft seems to have played a larger role in knocking out some targets, than skill.

That is not meant to diminish in any way, the dedicated aircrews of the RAF, but does show how complex night area bombing could be in WWII.

Skarper23 Nov 2014 10:50 p.m. PST

Thanks to all. What I'm looking for is a rough idea which I realise will change according to time frame and circumstances.

From what I've been able to distill so far it seems there'd one bomber about every 1000-2000m. But of course – many would be closer than that because there was no way to correct the spacing unless one got close enough to be visible.

The later war multiple stream attacks seem to have been shorter rather than narrower.

That they switched to multiple smaller streams heading for different targets seems to confirm the '1000 bomber raid' idea was for propaganda more than any actual material reason.

Also – a single stream would draw night-fighters from all over and create the effect of synergy. This seems to be what happened to the 30/31 March 44 raid on Nuremburg.

I found this site which has some interesting photos and information.

link

About half way down is a picture of a bomber stream heading to Nuremburg.

If you go to the home page there are pages on individual squadrons and airfields.

BTW – I was born in Hull but left when I went to university.

Mako11 Inactive Member24 Nov 2014 11:51 a.m. PST

That sounds about right, since by the mid-later Berlin Raids, they were attempting to get all the Main Force bombers over the target in a span of 20 minutes.

Therefore, you're looking at about 25 40 bombers a minute across a target, during that period. That means that number in a rectangle about 3.5 miles long, say 6 miles wide, and whatever you like to think deep (say 3,000 – 6,000 feet, or so, depending upon the types of bombers in the force, period of the war, assigned altitudes, pilot deviations from plan, etc.)

I've also read the average navigator drift error rate would usually be about 0.5% 1% (I suspect usually due mainly to variations in wondspeed predictions). Of course, if/when they encountered a jet stream (which most people didn't even know occurred), it could be much higher. So, that means up to about a 3 6 mile drift to either side of the planned course, at Berlin (on a direct route to the city).

Some of the navigators, and/or their pilots couldn't believe the deviation numbers they were seeing, e.g. 100+ MPH windspeeds on some nights, from the jet stream, so they tended to discount, or reduce them to more reasonable numbers, causing major deviations in bombing accuracy.

As for bomber separation Skarper, I read one account recently of a bomber crew watching a bomber shot down 50m to port, and then 50m to starboard of their own position, over a span of just a few seconds. Luckily, they then evaded the third attack by nightfighter ace Wittgensayn, on their own bomber, shortly thereafter.

troopwo Supporting Member of TMP24 Nov 2014 12:48 p.m. PST

In RAF raids, the differences in altitude would vary by the type of aircraft used. Stirlings having the lowest ceiling, with Halifaxes above and perhaps Lancasters higher yet.

Other differences in altitude would be caused by engine difficulties, being overloaded or by the problems of icing.

For the RAF, yes winds could vary, but they really did not go anywhere near high enough to be affected by the jet stream.

The jet stream would certainly have hit the B29 daylight formation raids over Japan. Reports came back of estimated ground speeds over 550mph. Once the XXth air force struck at night or even their daylight stream type raids, the jet stream became insignificant as they dropped altitude to get higher bombload and performance.

You might want to check on any effects of jet stream on the daylight formation raids of the 8th and 15th air force. I don't know if the B17s and B24s could achiee enough altitude to get hit too severely.

Mako11 Inactive Member24 Nov 2014 4:39 p.m. PST

Actually, there were a number of occasions where the jetstream did hit the RAF bombers, with 100+ MPH winds.

Of course, the pilots thought the navigators were daft, so discounted some of their reports, but they were present during the Berlin Raids, as well as some of the others.

I think the were on the order of 120 150 MPH, which caused a lot of problems for the force.

Apparently, on some really cold nights, it dropped down more than normal. Same thing happened with contrails being reported on the Nuremburg Raid, at around 20,000 feet, or so, instead of the usual 28,000 feet.

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