Comparing bomb load effectiveness

[wuzak]

How is it done?

For example, one comparison is made between a Mosquito and B-17. Often it states that they could take the same bomb load (ie 4000lb) to Berlin, but in actual fact the B-17 could take more (5000-6000lb).

In the case of the Mosquito the bomb load is one 4000lb HC (typically) or one 4000lb MC (rarely, I think).

The B-17 load can be made up of 2000lb, 1000lb, 500lb and smaller bombs.

The 4000lb HC bomb had around 75% of its weight in explosive material. The 4000lb MC bomb around 58%.

The high explosive US bombs were typically 50-55% charge to weight ratio.

So, a 6000lb B-17 bomb load would be approximately 3000-3300lb of explosives.
The 4000lb Mosquito bomb load would be arond 2300-3000lbs.

But which is more effective?

I suppose the effectiveness also is dependent on the accuracy of delivery, the type of target to be hit, etc.

I must admit it had never occurred to me to compare weight of explosives rather than weight of bombs, having thought about it when answering a question on another forum.

Is it best to compare explosives weight, assuming similar types of explosives, or the overall weight of bombs?

 

[Shortround6]

BOY OH BOY, is this a complicated question.

A lot depends on target type and placement.

You are trying to take out a large factory, ONE 3000lb charge at one end (or the middle) or 5-6 500lb charges spaced 100-150 ft apart down the length?

Now use multiple planes, 4 3000lb charges in a random distribution vs 20-24 (or so some parts of the 'strings' may be off target) 500lb charges.

the 4000lb cookies were supposed to be better at removing large portions of roof to let incendiaries in but the incendiaries aren't part of the 4-5000lb load.

Same with a rail yard. more "light" bombs spread damage over a wider area.

Against a BIG bridge, Multiple bombs give better chance for a hit but a single small hit may not be big enough to take the bridge down. Canal lock gates?

Blast damage goes down with the cube of the distance from the explosive, I believe, so you can definitely 'over kill' using a really big bomb but it was found that the 250-500lb bombs were not big enough to really damage heavy machine tools at much distance for the point of explosion.

I am not sure there is a simple answer although for building wrecking the HE may be the way to go.

Also remember that even against ships the whole purpose of AP bombs and Shells was to get explosives behind/under the armor.

 

[davebender]

Many of the larger RAF blast bombs were relatively inaccurate and therefore suitable only for area bombardment. Better to hit a bridge with an accurate 500lb bomb then miss with an inaccurate 4,000lb cookie.

 

[tyrodtom]

Who can determine why a bomb misses a target.
The bombadier is almost always going to blame the bombsite, the bomb itself, or external conditions he had no control over, ie, wind direction, or speed change after bomb drop, etc. So of course it's not his fault, it's the bomb.
The bombs blasted to tiny pieces, so there's no way to detemine if a error was made in manufactor.
Even if you drop a inert bomb, full of sand, and recover it later. It's so damaged by it's impact, there's no way to know if it's inaccuracy was inherit in it's design, or a result of faulty manufactor.

 

[davebender]

Properly conducted tests can determine bomb accuracy just as they can determine artillery accuracy.

 

[tyrodtom]

Properly conducted tests can determine bomb accuracy just as they can determine artillery accuracy.

Have you got any sources for those "properly conducted tests " ?

 

[Airframes]

So a 500 lb WW2 bomb is more accurate than a 4,000lb WW2 bomb?!!!!
The only thing that can be guaranteed about both (excepting acts of God) is that, once released, they'll both hit the ground!
And the whole idea of the 'many large RAF blast bombs' was just that - blast, to blow off roofs or knock down walls, allowing incendiaries to do their job, or to spread fires by blast. They didn't have to be accurate as such - just arrive in the middle of things!

 

[wuzak]

So, what of the 4000lb MC bomb Dave. Was that as inaccurate as the 4000lb HC?

It has been my thinking that it doesn't matter how aerodynamic the bomb is, so long as its flight is predictable. I haven't seen anything one way or the other to suggest whether the drop of the 4000lb HC cookie was predictable or not.

The 4000lb HC bomb was dropped in unison with a number of 500lb MC or GP bombs by Lancasters. I assume the object was to get them all in the same area?

 

[Greyman]

I haven't seen anything one way or the other to suggest whether the drop of the 4000lb HC cookie was predictable or not.

I don't have any real data on the subject but anecdotes from bomb aimers get the point across that it was definitely not a precision weapon.

 

[altsym]

Lotta carpet bombing in WWII. Accuracy wasn't a strong suit. That said, I think one would have much better luck dropping a string of 500 pounders
VS a single 4000lb cookie. Cookie missing a bridge by 75 yards minimal damage I would guess.. I think B-17s used 6 x 1600lb bombs also? Much better choise. But I suspose a Mossie can get relatively low when releasing the 4000lb to increase the accuracy.

 

[wuzak]

Lotta carpet bombing in WWII. Accuracy wasn't a strong suit. That said, I think one would have much better luck dropping a string of 500 pounders
VS a single 4000lb cookie. Cookie missing a bridge by 75 yards minimal damage I would guess.. I think B-17s used 6 x 1600lb bombs also? Much better choise. But I suspose a Mossie can get relatively low when releasing the 4000lb to increase the accuracy.

The Cookie wasn't best suited to bombing from low level. So they developed the 4000lb MC bomb (58% charge to weight vs 75% for the HC).

 

[altsym]

How accurate was the Mossie dropping the 4000lb hc bomb from altitude? Say as compared to the Lancaster.

 

[tyrodtom]

Even a guided bomb only had so much control authority.
The Fritz X when dropped from it most favored altitude of 18,000 feet could only have it's range adjusted by 1600 feet, and bearing by 1150 feet left or right. That's with full control deflection.
Just how far off course could a dumb bomb get just because it's tail fins bent, twisted, or whatever, out of shape and causes a eratic fall ?
But if a bombadier releases a bomb just 1 second late, or early, in a aircraft flying 300mph, that would effect the impact by 450 feet just by itself.

Not being accurate in knowing your groundspeed, not airspeed, is going to have a lot of effect also, and wind drift also.
I think the bombadiers might have shifted a lot of the blame, but they did have a very tough job.

In level bombing, I don't see that it matters what aircraft a bomb is dropped from. The bomb doesn't know what dropped it, another reason to call it a dumb bomb.

What matters is the bombadier and his bombsight.

 

[wuzak]

That said, I think one would have much better luck dropping a string of 500 pounders VS a single 4000lb cookie. Cookie missing a bridge by 75 yards minimal damage I would guess.. I think B-17s used 6 x 1600lb bombs also? Much better choise.

The B-17 was more likely to use 6 x 1000lb. The USAAF didn't use many 1600lb SAP bombs.

If 6 were dropped it is likely only one or two of them would hit the bridge. So, 500-1000lbs, approximately, of explosives on target.

I doubt Cookies would be used against bridges. More typically it would be 2 x 1000lb MC (or older GP) or 4 x 500lb MC bombs for Mosquitoes. And possibly a further two 500lb bombs on wing racks (depending on range to target). Alternatively it would be the 4000lb HC bomb.

 

[nuuumannn]

How accurate was the Mossie dropping the 4000lb hc bomb from altitude? Say as compared to the Lancaster.

We are getting a few things confused here; we are presuming accuracy has to do with the bomb size or the platorm that dropped it. It doesn't. Accuracy has to do with altitude, speed, wind direction, approximation of the bomb platform to the target etc. No matter what you are carrying in whatever platform; if you are nowhere near the target area, then you are not going to achieve your objective.

 

[altsym]

Yes I realize that, I was just wondering of the accuracy of one vs the other, with the same bomb load (if it can be answered)

 

[nuuumannn]

Sorry Altsym; I didn't mean to make an example of you or your post, but aircraft types have no bearing on accuracy. On the face of it, KGr 100's He 111s were more accurate at delivering their bombload on their targets in 1940 than 44 Sqn's Avro Lancasters were in 1942.

 

[altsym]

No need to apollogise friend.. if I say something stupid.. I can take a ribbing

 

[tyrodtom]

A certain aircraft may have a reputation for accurate bombing, but it the crews that really deserves the credit.

 

[nuuumannn]

To a certain degree Tom, but the actual credit for accuracy goes to the scientists who developed radio signals that guided the aircrew in their aeroplanes to the target area and the bomb release mechanisms, which determined precisely when the bombs were to be dropped.

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