Aerial Bombing Question (2 Viewers)

[Greg Boeser]

I got a couple of questions regarding aerial-bombing, particularly level-bombing with iron-bombs...

II. Bomb-Train/Track

This has to do with the fact that the bombs do not appear to all be released at the same time but over the course of a couple of seconds. Since each bomb follows a ballistic path after being released, would I be correct to assume that if one bomb is released a second ahead of the next they would land however many feet per second the bomber flies?

USAAF bombers were equipped with an intervalometer, which was set by the bombardier to drop the bombs in train at the selected interval. This was set by determining the ground speed of the a/c and the intended distance between bombs. The intervalometer calculated the time gap between bombs released. Alternatively, the bombardier could salvo the bombs, which would actuate the release sequence with the minimum time to complete the sequence. Each bomb shackle required approximately 1/20 of a second to operate, so a plane carrying 20 bombs would be rid of its load in about a second. Assuming the a/c was travelling at a ground speed of 220 mph, even a salvo would string 20 bombs over 100 yards.

 

[wuzak]

View: https://www.youtube.com/watch?v=4nfCdTRXj10


That is, literally, a tallboy bomb without the tail!

 

[wuzak]

One wonders if a high capacity blast bomb would have been better.

The 8000lb HC bomb had more explosive in a lighter weight.

 

[tyrodtom]

They used what they had. They really had no other use for a bomb that size during the Vietnam era.
Couldn't hardly load it on a F-4, or A1, they maybe could lift that much weight, but it was too big in size. It would fit in a B-52.

Actually we called any bomb with a fuse extended a Daisy Cutter, ( it took a special booster to transfer the detonation from the fuse to the bomb body) But when the Tall Boy was used, it was THE DAISY Cutter.

 

[Zipper730]

The bombs have a arming propeller on the fuse that doesn't arm until it's dropped what is considered a safe distance from the dropping aircraft.

That's actually what it's called, an arming propeller? I like to know the correct terms for things (saying thingamabob sounds foolish...)

It likely has a tail fuse

What's the advantages and disadvantages of a tail-fuse?

If you go to Joe Baugher's page and download his entire set of WWII serial number files, you can find a LOT of bombers that were damaged or lost from bombs exploding just beneath the aircraft, many with MACRs.

MACR = Missing Air Crew Report?

Certainly you've been in an aeroplane in some "bumpy" flights.

Yeah

Do you think that bombs are less subject to those "bumps" than you have been?

Okay, you're talking about a bomb being bumped around by turbulence... I'm not sure why I didn't understand the way you said it.

USAAF bombers were equipped with an intervalometer, which was set by the bombardier to drop the bombs in train at the selected interval.

I think that's what I saw on the Lancaster bombardier panel...

This was set by determining the ground speed of the a/c and the intended distance between bombs.

And the minimum interval was 1/20th for a salvo, and that would place all the bombs over 322'8" at 220 mph; 352'0" at 240 mph

Were salvo releases normal for attacks on specific targets?

 

[wuzak]

What's the advantages and disadvantages of a tail-fuse?

Tail fuses seem to have been used when delayed detonation was desired.

Also, obviously, when skip bombing the ground or water could, potentially, interfere with the fuse mechanism.

And the minimum interval was 1/20th for a salvo, and that would place all the bombs over 322'8" at 220 mph; 352'0" at 240 mph

Not all 20 bombs would be falling from the same rack.

I think that if this method was used all racks of bombs (2 or maybe 4) would drop at the same time.

 

[tyrodtom]

What I called a arming propeller was called a arming vane in the tech. manuals.

I don't think a tail fuse was a advantage, it was a failsafe. If the nosefuse didn't set the bomb off on impact, the tail fuse hopefully would. And both fuses had many delay options.
The tail fuses had a arming vane too that had to spin a set number revolutions before it armed.
I'm not acquainted with every US produced bomb from WW2, but the ones I have worked with all had 2 fuses, nose and tail.

The bomb in Greg's picture was not a finished ready for mission bomb, it had no fuse, nose or tail .

I can tell because I can see no arming wire, that was used to keep the arming vane from spinning.
The fuse was stored in a sealed container with a cotter pin thru the arming vane and a small hole in the fuse body.
After you installed the fuse in the bomb, you removed that cotter pin, and slid the arming wire thru the two holes, and secured the wire with a farnstock (sp) clip.
If the pilot or bombardier chose to drop armed bombs, the arming wire stayed attached to the bomb rack, and the arming vane was free to spin. If they wanted to drop unarmed bombs, the arming wire was released from the bomb rack with the bomb. The arming vanes couldn't spin. The bomb wouldn't explode on impact unless it hit something pretty solid.

And don't forget some fuses were designed to not explode on impact at all, but hours later to hamper recovery efforts. And some were designed with anti-withdrawal devices to kill bomb disposal personnel.

 

[stona]

The British Automatic Bomb Distributor, which didn't require a made up word, did the same job as the American 'Intervalometer'. It had some quite sophisticated options.

 

[stona]

USAAF bombers were equipped with an intervalometer, which was set by the bombardier to drop the bombs in train at the selected interval. This was set by determining the ground speed of the a/c and the intended distance between bombs. .

This is correct, and it was usually related to the mission type. For example, when bombing using H2X with poor or no ground visibility, which the 8th AF knew to be far less accurate than some other methods, the 'intervalometer' was set to give a longer gap between the bomb releases. The assumed pattern was consequently quite large, a circle (yes, a circle) 3,300 feet in diametre.

Post operational analysis bombing attempted to use the pattern centres to estimate accuracy. Through 10/10 cloud using H2X accuracy is not a word I would have used, only pattern centres within five miles of the aiming point were used, any other were discounted. Average range error was 1.74 miles, deflection 1.4 miles and circular error 2.4 miles. No pickle barrels troubled by those results, though blind bombing using rather primitive radar is a worse case scenario Through 4-5/10 cloud all those errors were roughly halved.

Cheers

Steve

 

[Greg Boeser]

Not all 20 bombs would be falling from the same rack.

I think that if this method was used all racks of bombs (2 or maybe 4) would drop at the same time.

The bomb shackles were wired to release in sequence. No shackle could release until the previous one had been activated, thus completing the circuit. This prevented the possibility of a bomb falling on a hung bomb. Hung bombs were fairly common.

 

[Greg Boeser]

Going back to my manuals, the bomb racks on a B-26 operated either electrically for bombing or mechanically for salvoing unarmed bombs. So what I said earlier is correct for live bombs, but not for unarmed bombs.
This makes sense in that crews that suffered a malfunction of the electrical bombing mechanism could mechanically salvo the remaining bombs.

 

[wuzak]

The bomb shackles were wired to release in sequence. No shackle could release until the previous one had been activated, thus completing the circuit. This prevented the possibility of a bomb falling on a hung bomb. Hung bombs were fairly common.

You misunderstand what I say.

Depending on bomb sizes being carried, a B-17, for example, has 2 or 4 racks being used. The bombs in each rack have to go sequentially, but I don't believe each rack has to go sequentially.

B17 bomb bay by Tom South, on Flickr

B-17 Bomb Bay by Rick Hawkinson, on Flickr

 

[Greg Boeser]

You are correct. Here's a picture of a B-24 releasing a mixed load of bombs from both bays.

 

[swampyankee]

Dragging it back to WW2.

With the lack of navigational aids, the CEP, be it 100m or 400, was frequently dwarfed by the navigational error of not finding the right city. Until there were better navigation aids, there were times when CEP had to include navigation errors of miles.

 

[Zipper730]

Tail fuses seem to have been used when delayed detonation was desired.

Okay

Not all 20 bombs would be falling from the same rack.

So, each shackle had to release from the bottom to the top in order?

What I called a arming propeller was called a arming vane in the tech. manuals.

Okay, so it's an arming-vane...

And don't forget some fuses were designed to not explode on impact at all, but hours later to hamper recovery efforts. And some were designed with anti-withdrawal devices to kill bomb disposal personnel.

Time-delay and anti-disturbance fuses...

The British Automatic Bomb Distributor, which didn't require a made up word, did the same job as the American 'Intervalometer'. It had some quite sophisticated options.

Such as?

This is correct, and it was usually related to the mission type. For example, when bombing using H2X with poor or no ground visibility, which the 8th AF knew to be far less accurate than some other methods, the 'intervalometer' was set to give a longer gap between the bomb releases. The assumed pattern was consequently quite large, a circle (yes, a circle) 3,300 feet in diametre.

How did they get a circle... the bomb release follows a line or a very narrow oval unless you're talking about the whole formation?

Post operational analysis bombing attempted to use the pattern centres to estimate accuracy. Through 10/10 cloud using H2X accuracy is not a word I would have used, only pattern centres within five miles of the aiming point were used, any other were discounted.

They assumed a pattern center 3300 feet in diameter within five miles of the aiming point and ignored those that fell outside that?

Average range error was 1.74 miles, deflection 1.4 miles and circular error 2.4 miles.

So they were on average 1.74 miles away from the target, had a CEP of 2.4 miles from the aiming point, and what's deflection? If I recall deflection has to do with leading a target by aiming ahead of it?

The bomb shackles were wired to release in sequence. No shackle could release until the previous one had been activated, thus completing the circuit. This prevented the possibility of a bomb falling on a hung bomb. Hung bombs were fairly common.

Is this like one of those old series circuits that people had on christmas tree lights where one light goes out and everything goes dead at once and you have to spend a month and a day figuring out which light burned out?

 

[BiffF15]

You are correct. Here's a picture of a B-24 releasing a mixed load of bombs from both bays.
View attachment 364780

Greg,

Are you sure of that? It looks to me that the "small" bombs are from the B-24 further away in the picture, and the "big" bombs are from the nearer aircraft.

Cheers,
Biff

 

[wuzak]

Greg,

Are you sure of that? It looks to me that the "small" bombs are from the B-24 further away in the picture, and the "big" bombs are from the nearer aircraft.

Cheers,
Biff

I agree.

It looks like the near B-24 has dropped 8 bombs, 2 lots of 4.

The far B-24 has also dropped 8, but earlier and they have fallen further.

It does show that one bomb was released from each of the 4 racks at the same time.

 

[wuzak]

So, each shackle had to release from the bottom to the top in order?

You would have problems if they released from the top first.

But it is still not what I was saying.

For a B-17 to have 20 bombs on board they would be held on 4 racks - possibly 6 each on the inner racks and 4 each on the outer racks.

So the time taken to drop all is not 20 times the interval between bombs. More like 6 times.

 

[stona]

Dragging it back to WW2.

With the lack of navigational aids, the CEP, be it 100m or 400, was frequently dwarfed by the navigational error of not finding the right city. Until there were better navigation aids, there were times when CEP had to include navigation errors of miles.

In the analyses 'gross errors' were usually discounted. How an analysis was done was dependent upon the type of mission and many factors. In the example I gave above (H2X through cloud cover) any bombs that fell more than five miles from the target were ignored. This figure for bombs that were simply ignored is substantial. In the worse case scenario, bombing blind on H2X through 10/10 cloud, 41.5% of bombs fell more than five miles from the aiming point and were discounted.

US analysis was in some ways more detailed than British analysis, principally because bombing in daylight meant that the Americans could often see (and photograph) where the bombs from a Group fell. The British relied largely on individual bombing photographs, and anyway every aircraft carried a bomb aimer (bombardier) who used a bomb sight (no toggling on the leader at night) and every aircraft bombed individually.
The Americans used 'Group Pattern ' analysis in which a single set of error measurements were calculated for the bombs dropped by an entire Group. The object was to establish how well the bombs were aimed. The Americans established a 'pattern center', defined as the centre of a circle with 1000' radius in which most of the bombs fell. It was the displacement of this point from the aiming point which was used to calculate the bombing errors.
Here again many raids gave results which were rejected for analysis. Of 398 VISUAL raids by the 8th AF analysed from strike photographs in 1943, raids in which the famous pickle barrel might have been expected to feature, 113 (nearly 30%) were rejected from the analysis because "no coherent compact pattern was formed."
The Americans had earlier attempted to use the Mean Point of Impact (MPI) to assess bombing errors. This was a method useful in some instances, like for example fighter bomber attacks on specific targets, but proved unsatisfactory for pattern analysis. The problem was that a relative few (2 or 3 from a Group of 21) stray 'sticks' of bombs falling outside the pattern might drag the MPI to the periphery of the main fall or even outside it.

It took some time for the British to realise that they simply couldn't navigate or bomb accurately by night, a lesson that in slightly different form had to be relearned by the Americans when they discovered that their results over continental Europe fell a long way short of those achieved on the practice ranges of the USA.

Cheers

Steve

 

[Milosh]

With bomber formations 500yd across and even wider, a lot of bombs are going to be spread out.