Bomb and Bomb-Bay Sizes

wuzak said:

384th Bomb Group shows, for the aircraft I have looked at, 10 x 500lb GP for 17 August.

View attachment 794422

The maximum bomb load for a Mosquito in the period (August-October 1943) was 2,000lb (B.IV) or 3,000lb (B.IX, if any were around).

Schweinfurt should be well within range of a B.IV Mosquito with 2,000lb bomb load.

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Thanks. I did not realise the early Mosquitos did not have the later bomb load capacity. My memory is that the B-17 and B-24 bomb loads dropped on the later models as the empty weight grew from turrets and waist guns, Tokyo tanks, etc.

From the same chart for the B-17 it seems its heaviest internal load was 6 1600 lb bombs or 9600 lb but it may have been able to carry a couple of lighter bombs above the larger bombs. As someone already said tho, the 1600 lb bomb was rarely used.

EwenS said:

The normal B.IV usually carried 3x500lb & 1x250lb bomb due to it suffering fore and aft instability at altitude with 4x500lb and needed to be "flown" all the time, which was of course tiring for the pilot.

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Not heard/seen that before.

I always thought the standard bomb load was 4 x 500lb.

The 250lb could also be a TI, since TIs weren't available in 500lb.

The maximum internal bomb load for a B-17 was 8*1590lb AN-Mk1 AP bombs. It seems late in 1943 this was changed to six. Physically it was still capable of carrying eight. I assume it was related to the wing bending problem at high weights that required fuel to be left in the outer wing tanks to keep things in check. The six bomb configuration had better bomb release angles and about 50% more fuel at the typical maximum takeoff weight of 65,000lbs.

Mosquito IV finished production in June 1943, with 273 built as bombers, there were 54 mark IX bomber April to November 1943, mark XVI bomber production began in November 1943, with 109 built to end June 1944.

To start with Mosquito HE loads only, Bomber Command Mosquitoes dropped 758x250 pound HE bombs for the war and after dropping 10 of them on the night of 3/4 November 1943 only dropped another 21, the last on 11 March 1944. Mosquitoes first dropped Target Indicators on 27 January 1943.

1942 raids, ratio of 500 pound to 250 pound HE
May 1 to 1
June 1.1 to 1
July 1.7 to 1
August 2.3 to 1
September 20.6 to 1
October 31.9 to 1
November, December 341x500 pound and no 250 pound bombs dropped. January to May 1943 1,706x500 and 66x250 pound HE, 307x250 pound incendiary, 208 of the TI where no HE bombs were dropped. Also mostly in February 1943 loads of 3x500 pound were being carried.

The period June to October 1943 saw 2,050x500 and 535x250 pound HE bombs dropped or around 3.8 to 1, nightly figures routinely report a 3x500 and 1x250 pound load. Add the 681x250 pound target indicators and the ratio is 1.7 to 1. To type slowly, removing the 361 TI dropped on targets when there were no HE bombs dropped leaves a ratio of 2.4x500 pound to 1x250 pound. Given the number of nights when the Mosquito force was a mixture of bombers and pathfinders it seems clear enough most sorties with 500 pound bombs on board the ratio was 3 to 1 with exceptions, in November 1943 it was 1,263x500 to 15x250 pound and from then on HE loads were usually 4x500 pound unless a 4,000 pound bomb could be carried.

All this when from 1942 into early 1944 the majority of Mosquitoes with Bomber Command were mark IV and the arrival of the Canadian built types which were roughly mark IV equivalents.

As examples,
30 August 1943
11 Mosquito attacked Munchen-Gladbach,3x500, 1x250 pound HE, 32x250 pound TI (Main force target)
10 Mosquito attacked Duisberg 30x500, 1x250 pound HE, 2x250 pound TI
3 Mosquito attacked Foret D'Eperleques, 12x250 pound TI
For the night 33x500, 2x250 pound HE, 46x250 pound TI.

23 September 1943
6 Mosquito attacked Mannheim 24x250 pound TI (Main force target)
8 Mosquito attacked Darmstadt 24x500 pound HE, 8x250 pound TI (Diversion)
6 Mosquito attacked Aachen 18x500 and 6x250 pound HE

HE only raids 24, 25 and 26 September 1943
23 Mosquito attacked various targets 69x500 and 23x250 pound HE

From May 1944 onwards the reporting splits Mosquito sorties into Oboe and non Oboe.
Non Oboe 6,826x4,000, 14x1,000, 23,657x500 pound HE, 8x4,000, 347x1,000, 15x500, 3,928x250, 10x100, 4,340x4 pound incendiary
Oboe 1,106x4,000, 5,033x500 pound HE, 6x1,000, 10,319x250 pound incendiary

wuzak said:

Not heard/seen that before.

I always thought the standard bomb load was 4 x 500lb.

The 250lb could also be a TI, since TIs weren't available in 500lb.

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1942/43 there were only 4 Mossie bomber squadrons and their role changed over time.

105 - started receiving Mosquitos for training in Nov 1941 but it was the night of 30/31 May 1942 before they flew their first sortie.
139 - reformed 8 June 1942 and initially used 105 squadron aircraft until it began to receive its own in Sept.

These squadrons flew an increasing number of low level daylight bombing sorties from Sept 1942. So carrying 4x500lb would not have been such a problem at low level (note I said the instability problem was at altitude and it fits with Geoffrey's data about the ratio of 500lb to 250lb bombs). Then in June 1943 they were switched to 8 Pathfinder Group, where 105 became the second Oboe squadron (see below) while 139 continued night nuisance raids until acquiring other bombing aids like G-H (from Oct 1943) and then H2S (from March 1944)

109 - this unit was initially concerned with Wireless Development / Recce / Investigation. It began to receive some Mossies from Aug 1942 for Oboe development work and then concentrating on this bombing aid, flying its first Oboe mission in Dec 1942.

It was Nov 1943 before the next Mossie bomber squadron became operational, to be followed by another 6 during the course of 1944 and the last in Jan 1945.

Edit:- First operations by the various bomber Mossie versions were as follows:-

B.IV - 30/31 May 1942
B.IX - 13 July 1943
B.XVI - 10/11 Feb 1944
B.XX - 2 Dec 1943
B.XXV - 9 Oct 1944

Greg's Planes and Automobiles weighed in on the Mosquito vs the B-17 debate.


View: https://youtu.be/7Wdq0bkRdzE?si=8Hatj475yXgU7ONF
It is mostly fair.

To me it does seem like he suggests that the "cookie" was only used against cities, and the "cookie" was the only 4,000lb bomb that the Mosquito could carry.

And he seemed to suggest that it was only used against cities.

Also suggests that RAF accuracy was measured against the area of an entire city, compared to USAAF using a 1,000ft circle around the aiming point.

wuzak said:

Greg's Planes and Automobiles weighed in on the Mosquito vs the B-17 debate.


View: https://youtu.be/7Wdq0bkRdzE?si=8Hatj475yXgU7ONF
It is mostly fair.

To me it does seem like he suggests that the "cookie" was only used against cities, and the "cookie" was the only 4,000lb bomb that the Mosquito could carry.

And he seemed to suggest that it was only used against cities.

Also suggests that RAF accuracy was measured against the area of an entire city, compared to USAAF using a 1,000ft circle around the aiming point.

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The "Cookie" was the High Capacity 4,000lb bomb. The charge to weight ratio was 75%

When De Havilland designed the 4,000lb conversion, the RAF gave them both a "Cookie" AND a 4,000lb Medium Capacity bomb to play with. Dimensionally both are virtually the same length wise and exactly the same diameter, but their appearance is different, the latter more resembling a typical bomb with a tail fin rather than a dustbin. The MC bomb had a thicker case and therefore a reduced charge to weight ratio of 58%. But the MC bomb was able to be fitted with a delayed action fuse unlike the HC bomb

Unfortunately the data I have only refers to "4,000lb bomb" dropped without breaking it down between the two types. AIUI the "Cookie" was not fitted with delay action fuses as its thin case and Amatol filling were highly likely to explode on impact anyway! The MC bomb could be fitted with delayed action fuses.

A delayed action 4,000lb bomb was used by the Mossie. For example on 1 Jan 1945 16 aircraft from 571, 128 & 692 squadrons attacked railway tunnels in western Germany from altitudes of 100-200ft with the objective of slinging their delayed action bombs into the tunnel mouths. The delay was to ensure that they would explode in the tunnels if aimed accurately. They achieved some success, with some making multiple runs on their targets..

Arthur Harris despatch on operations has an accuracy graph, night raids on German cities excluding Berlin, percentage of bombs within 3 miles of aiming point in good weather (remembering pathfinders could mark the wrong aiming point and photographs of the ground were needed to measure individual accuracy), from 1942 to 1945. Starts at under 25%, to around 30% in May 1943, by June it was 50%, gets to over 60% in April 1944, then a general trend up to around 88% in December 1944.

When it comes to Bomber Command accuracy does the Greg "entire city" comment get qualified for the 262,078.1 tons of bombs dropped by day, or the 287,647 tons dropped on enemy occupied territory, the 122,532 tons dropped on troops and defences, the 97,918 tons dropped on oil targets, the 54,522 tons on V weapon sites. Or is it just the 430,747 tons of bombs dropped on towns, compared with 657,674 tons dropped on Germany. How about non Bomber Command RAF bomb raids?

Does the USAAF 1,000 feet comment apply for all methods of aiming? The USSBS has bombing accuracy reports. The USAAF one uses within 1,000 feet, 0.5 miles, 1 mile, 3 miles, 5 miles and over 5 miles, for the September to December 1944 period the best case of visual bombing in good to fair visibility, 30% within 1,000 feet, 91.5% within 3 miles, 7.8% over 5 miles, the worst case H2X in 10/10 cloud 0.2% within 1,000 feet, 39.8% within 3 miles, 41.5% over 5 miles.

The USSBS report Description of RAF Bombing has another graph of night bombing accuracy, different target selection but again in weather good enough to obtain photographs, which mainly follows the Harris graph, mostly better in 1942/43, worse in winter of 1943/44, then around Harris figures for 1944. A selection of 31 raids on German targets (3 on Berlin) October 1943 to October 1944 reports 38% of all bombs hit built up areas, worst 8% Duisberg 14 and 14/15 October 1944, best 91% Kassel 22/23 October 1943 (firestorm). The Duisberg figure includes the 14 October day raid, it was operation Hurricane, 9,034 tons of bombs dropped on the city in one day, nominal pre war population 440,000, Kassel had 175,000 people.

There are plenty of oboe controlled Mosquito only raids, are they supposed to be all against cities versus specific targets?

Mosquito 4,000 pound bombs dropped 776 HC, 141 MC, 7,469 M2 HE, 8 incendiary

Bomber Command 4,000 pound bombs dropped 10 SPEC, 54,587 HC, 253 MC, 19,049 M2, 202 GP, 3 RDX HE, 108 incendiary in night raids, 13,198 HC, 284 MC, 1,694 M2, 15 GP, 3 RDX HE in day raids

First usages HC 31 March 1941, GP 9 January 1942, RDX 13 July 1942, SPEC 24 August 1942, Incendiary 10 September 1942, MC 13 April 1943, M2 16 December 1943

Day 1 January 1945, 17 Mosquito sent, 16 attacked RR/Tunnels in Germany, area bounded by Coblenz-Kaiserslauten-Trier-St Vith-Euskirchen dropping 11x4,000 MC and 5x4,000 M2 HE bombs. The Mosquito reported missing is credited with attacking its target.

Also in 1 January 1945 number 5 group attacked the Dortmund-Ems Canal, there were 19x1,000 pound Target Indicators dropped by Lancasters and 4 by Mosquitoes but as route, not target, markers, 1 of the 2 Mosquitoes sent listed as an abort (627 squadron)

First Mosquito raids dropping 4,000 pound bombs, night of
23-Feb-44 Dusseldorf
24-Feb-44 Kiel
25-Feb-44 Saarbrucken
25-Feb-44 Mannheim
29-Feb-44 Dusseldorf
1-Mar-44 Stuttgart
2-Mar-44 Krefeld
2-Mar-44 Munchen-Gladbach
3-Mar-44 Krefeld
3-Mar-44 Dusseldorf
3-Mar-44 Berlin

Is the 4,000lb M2, a 4,000lb HC Mk.2? Or is it an MC?

The 4,000lb GP is a pre-war design, with low filling to weight ratio?

Arthur Harris, Despatch on Operations
4,000 GP "On the 28th of March 1942 I asked the Air Ministry to proceed with the development and production of 4,000 pound GP bombs. On 31st March 1942 a requirement was placed for 500 of these bombs to cover the next six months. By May 1942 4,000 pound GP bombs were coming off production."

"During the Autumn of 1944 4,000 pound MC bombs were used by Mosquito aircraft for high altitude night bombing, as the ballistics of these weapons are much superior to those of the 4,000 pound HC bomb" As noted above the Mosquitoes dropped a lot more 4,000 pound M2 than HC, for Bomber Command as a whole it was the other way around.

The 3 October 1944 attack on the Walcheren Dykes used 237 4,000 pound MC, no 4,000 pound M2 or HC, another 10 MC dropped in December 1944 and 11 in January 1945, out of 284 MC dropped in day raids. For some reason Bomber Command have the 4,000 pound MC, (last night raid usage on 12/13 August 1944) and the 4,000 pound M2 used from December 1943 onwards. So far no reference found to establish the difference.

So, M2 = MC?

wuzak said:

Is the 4,000lb M2, a 4,000lb HC Mk.2? Or is it an MC?

The 4,000lb GP is a pre-war design, with low filling to weight ratio?

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wuzak said:

So, M2 = MC?

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The largest British bomb in development at the start of WW2 was the 2,000lb Armour Piercing bomb which finally appeared in 1940 IIRC.

I mentioned the 4,000lb HC & MC in my last post but there was also a 4,000lb GP developed as noted by Geoffrey. Charge to weight ratio was 30%. But it seems only 217 of these were dropped by Bomber Command, per the article linked below. Details here

I'm not sure which weapon Geoffrey is referring to as the "M2". Doesn't sound like a British designation and I can't find a US weapon with that designation. The only US 4,000lb bomb i can find is the AN-M56, a light case weapon whose effect would be similar to that of the RAF HC weapon. Initially thought it a typo, but on rereading his post #108 above I'm not so sure. That kind of error would be unusual for him.

This might help you with RAF bomb development.

I have seen the M2 referred to in a book about the Mosquito. Graham M Simons, "Mosquito: The Original Multi-Role Combat Aircraft".

It too is in a list of bombs used by the Mosquito, but no mention of the 4,000lb GP bomb!

I have an old spreadsheet given to me by a former member.

I don't know what his original sources were, but it has 2 sheets with the bombs dropped by the Mosquito during the war.

One one sheet it says the following 4,000lb bombs were dropped:
4,000lb HC: 776
4,000lb M2: 7,469
4,000lb MC: 141
4,000lb TI: 8 (I think that probably should be incendiary)

The other says:
4,000lb HC: 776
4,000lb HC Mk2: 7,469
4,000lb MC: 141
4,000lb TI: 8

Which would suggest that the M2 is the HC Mk.2.

Somebody may have been using 'short hand'.

A manual for British bombs and pyrotechnics dated Nov 1944 lists
A 4000lb GP bomb. 30% charge weight Mark I & II in service, normal tear drop shape.

A 4000lb MC bomb 58% charge weight (? 3 different fillings) Mark I & II in service. semi streamline

A 4000lb LC bomb 73% charge weight Mark I obsolescent.

A 4000lb LC bomb 75% charge weight (? different fillings) Mark II & III obsolescent
...4000lb LC bomb 75% charge weight (? different fillings) Mark IV, V, VI in service.

There is no indication of how many of each were actually built or exactly when unless someone wants to try and guess by using what they were filled with.
later LC bombs may have gotten Minol 2 or Torpex 2.


This is the 4000lb MC bomb unless the manual is wrong.

4000lb MC bomb is 109.5in long, max body diameter is 30in and max tail diameter is 30in.

the 4000lb HC bombs are the more familiar "can" peeking out on the left side of the picture.

The MK V and MK VI were made/filled in the US.

Shortround6 said:

A 4000lb LC bomb 73% charge weight Mark I obsolescent.

A 4000lb LC bomb 75% charge weight (? different fillings) Mark II & III obsolescent
...4000lb LC bomb 75% charge weight (? different fillings) Mark IV, V, VI in service.

There is no indication of how many of each were actually built or exactly when unless someone wants to try and guess by using what they were filled with.
later LC bombs may have gotten Minol 2 or Torpex 2.

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LC is an American designation.

Did you mean HC?

wuzak said:

LC is an American designation.

Did you mean HC?

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You are correct.

For some reason they spaced things out like 4000 LB. H.C.

I kept skipping over the capitalized LB and reading it as LC. as in 4000lb LC

other stuff should be correct.
It is a U.S.N.B.D. manual

Weekly average of 4,000 pound bomb casing production, months are exactly 4 or 5 weeks, total production divided by 4 or 5 and rounded.

Examples of monthly actual production

500 lb MC as of July 1945 production numbers come in 4 groups, 1) mark I, VI, VIII, 2) mark II, X, XIV, 3) mark III, VIII, 4) mark IV, IX
Picture 228 a from Air 14/930
Picture 454 for day raids 11 September 1944 from Air 14/3367.
The list in message 114 is probably from Appendix 24 of Mosquito by Sharpe and Bowyer

Re MC fillings - from USN OP 1665 June 1946

Back to the main target.
A comparison of bomb loads between AAF bombers.:
* These are my best guesses as I don't have the actual values. Largely based off of the fact that if a dimensionally larger bomb fits a smaller one will too.
! I put four but it might be two. I have little primary source material to go off of.
# The B-25 can actually carry six 1000lb M52 AP bombs. Due to its better release angles.
$ Conceivably, if the racks were strong enough, the early B-29 11 station 1000lb racks could have carried 16 Mk33 AP bombs.
? Means I'm not willing to make a guess.
Observations and notes:

The A-20 has the smallest bomb bay but can carry 80% of the largest (B-19) and 40% of the second largest (B-29) in 100lb bombs. Most A-20 had semi-permanent fuel tanks in the bomb bay with a pair of bomb carriers mounted below for a maximum of four 100lb to 500lb class bombs.
The A-20, A-26 and B-25 all have bomb bays about the same volume, but the latter two could hold significantly more large bombs.
The only difference between early and late B-17s was an increase in stations from 20 to 42. The actual available space wasn't all that much but it used it very effectively.
With a more sophisticated bomb rack system the B-19 could have been a lot closer to the B-29 and B-32 in medium and small bomb capacity.
The B-24 clearly has a significant advantage over the early B-17s. Add in its 1/3 greater fuel capacity and the B-24 is the clear winner over the early B-17.
The B-26 forward bomb bay was modeled off of the early B-17 but the high wing an slightly smaller fuselage had very negative impact on capacity.
The vast majority of B-29s had only eight station 1000lb racks and were never issued the six station center racks for 100/300lb bombs. This limited the B-29 to a maximum of 40 bombs.
The B-32 has a bomb bay that was on paper on par with the B-29. In practice it was far more cramped and rather difficult to mount many of the 500lb class weapons in a timely manner. On top of this the B-32 suffered from engineering and manufacturing defects that made switching racks difficult. On top of this the B-32 had five types of racks all with left and right handed versions. A complete set consisted of 28 racks. By comparison the early B-29 had two racks that were handed and two that were not. Total rack count was 20. Later reduced to 16.