Bomb and Bomb-Bay Sizes

MiTasol said:

I find the picture labelled B17F_bomb_load_1 most interesting as it infers that the B-17F had a maximum bomb capacity of just 2,000lb. I think that highly unlikely but I have never studied at the B-17 loads.

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If you look at the Data Card, the normal bomb load is 2064 #, and the alternate bomb load is 4128 #. So that implies that the maximum bomb load is 4128 #. Then to confuse things further, the bomb loading chart shows overload bombs, and adding in those can exceed that 4128 # limit, sometimes.

Here's the overload expansion: 24 - 100 # (2400 #); 16 - 300 # (4800 #); 12 - 500 # (6000 #); 6 - 1000 # (6000 #); 8 - 1600 # (12,800 #); 2 - 2000 # (4000 #).

We have to look at the stated "gross weight" and figure out how much fuel you could put in the plane and how many bombs.
Then we have the overload weights or max weights and the B-17 gets absolutely screwy here.
B-17E may have been 40,260 pounds gross, 53,000 pounds maximum.
B-17F may have been 40,437 pounds loaded, 56,500 pounds maximum.
B-17G may have been 55,000 pounds normal loaded, 72,000 pounds maximum.

There may have been in between loads and/or refits/upgrades.
How much was paper upgrades and how much involved new parts?
What were they actually operated at?
Some of the early ones had problems breaking landing gear while taxing on certain typed of air fields and/or were prohibited from doing pivot turns when over a certain weight.

However it does really leave us wondering what the bomb load of B-17 was
B-17G 32,720 pounds empty, no guns, oil crew and with ??? radios ??

It is a pity that Bill Runnels is long gone as he would have been able to solve this riddle.

Shortround6 said:

However it does really leave us wondering what the bomb load of B-17 was

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According to my calculations it's about 55,000 Mars Bars. Fewer if you're using clamshells.

We will use any measurement but metric!

SaparotRob said:

We will use any measurement but metric!

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Managing a gas station, I had a clerk who would complain about customers who came to his register and ask for "ten gallons of gas".

"Why can't they just say thirty bucks?!" he'd complain.

So one day about a few weeks later, going home for the day and filling up, I went up to his register and asked for 42,000 kiloergs of gasoline.

Jimmy stinkeyed me for a hot second and then asked, deadpan, "What grade?"

MiTasol said:

An excellent post as it answers the un-asked but important related question of what the aircraft pitch angle limits were for safely releasing the bombs and partially answers the post 4 quetion on clearance angles.

This incidentally means the B-17 could not be used, like the Pathfinder Lancasters were, as a dive bomber for target marking. There may, of course, have been mods to those aircraft but because it is a long wide bay I would expect there were just limitations on which locations the markers could be carried.

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It wouldn't matter to be honest, as the B-17's controls would become very stiff as the airspeed builds up (Eric "Winkle" Brown noted this when he evaluated the B-17 and Lancaster).

MiTasol said:

An excellent post as it answers the un-asked but important related question of what the aircraft pitch angle limits were for safely releasing the bombs and partially answers the post 4 quetion on clearance angles.

This incidentally means the B-17 could not be used, like the Pathfinder Lancasters were, as a dive bomber for target marking. There may, of course, have been mods to those aircraft but because it is a long wide bay I would expect there were just limitations on which locations the markers could be carried.

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Generally, Pathfinders level bombed for target marking, as they relied on the electronic aids - Gee, Oboe, Gee-H, H2S.

617 squadron in 5 Group pioneered marking at low level and dive bombing, which used visual aiming.

Leonard Cheshire started low level marking with the Lancaster, but then changed to the Mosquito and finally to the Mustang, when the Mosquitoes were taken away.

wuzak said:

Leonard Cheshire started low level marking with the Lancaster, but then changed to the Mosquito and finally to the Mustang, when the Mosquitoes were taken away.

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A great man who did so much post war for orphans and others

I picked this one up in a book store yesterday

This video talks about the Mosquito could carry the same bomb load to Berlin as the B-17 myth.


View: https://youtu.be/SSlxqpl-p6w?si=XJ6BcXB6V_EyBVv-

These mission reports confuse me.





12 x 1,000lb bomb load seems unlikely, especially with additional incendiary bombs.

12 x 1,000lb + 38 x M47A1 (nominally 100lb) seems impossible.

Are these the load across the group?


Other reports and the 303rd BG seem to show individual aircraft loads:






I have also been looking at some reports from the 384th Bomb Group for the Schweinfurt Missions.

For the August 17 mission, the 384th Bomb Group aircraft looked to have been loaded with 10 x 500lb GP bombs, and the Octiber 14 mission they had 3 x 1,000lb GP bombs and 5 x 65lb (incendiaries I assume).

Reports I have seen from the 384th BG and 351st BG for the October 4 1943 mission show 42 x 65lb incendiary bomb loads.

wuzak said:

These mission reports confuse me.

12 x 1,000lb bomb load seems unlikely, especially with additional incendiary bombs.

12 x 1,000lb + 38 x M47A1 (nominally 100lb) seems impossible.

Are these the load across the group?


Other reports and the 303rd BG seem to show individual aircraft loads:

View attachment 794414

View attachment 794413


I have also been looking at some reports from the 384th Bomb Group for the Schweinfurt Missions.

For the August 17 mission, the 384th Bomb Group aircraft looked to have been loaded with 10 x 500lb GP bombs, and the October 14 mission they had 3 x 1,000lb GP bombs and 5 x 65lb (incendiaries I assume).

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From the chart in post 43 the maximum number of 1000 bombs that can be carried internally is 6,000 lb. Add two externally and the absolute max number of 1,000 bombs per load is 8,000lb if you are willing to accept the performance and range penalties of the external load. To fit the incendiaries it is necessary to leave out some of the 1,000 lb bombs to provide space.

17 Aug raid shows that each 303rd aircraft only carried 4,000 lb, same load as a mossie*

14 Oct raid shows that each 303rd aircraft only carried 3,325 lb, 675 lb less than a mossie*

*conditional on the mossie having that range.

According to the 303rd BG (H) website, on the 14 October Schweinfurt raid they carried a long range tank in one side of the bay, with 3x 1000 lb HE and 5x 100 lb M47 Incendiary in the other side of the bay.

I suspect that the 10 October Coesfeld raid bomb load is supposed to 1x 1000 lb HE and 38x 100 lb M47 Incendiary - with the 12 being a typo.

NOTE that the later B-17F and (all?) the G models could carry upto 42x 100 lb M47 Incendiary if that was all they carried. If they carried only 1x 1000 lb HE - on the lowest 1000 lb station of one of the inner racks - then there was room/clearance for the 38x 100 lb M47 Incendiary.

ThomasP said:

According to the 303rd BG (H) website, on the 14 October Schweinfurt raid they carried a long range tank in one side of the bay, with 3x 1000 lb HE and 5x 100 lb M47 Incendiary in the other side of the bay.

I suspect that the 10 October Coesfeld raid bomb load is supposed to 1x 1000 lb HE and 38x 100 lb M47 Incendiary - with the 12 being a typo.

NOTE that the later B-17F and (all?) the G models could carry upto 42x 100 lb M47 Incendiary if that was all they carried. If they carried only 1x 1000 lb HE - on the lowest 1000 lb station of one of the inner racks - then there was room/clearance for the 38x 100 lb M47 Incendiary.

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That makes sense.

MiTasol said:

17 Aug raid shows that each 303rd aircraft only carried 4,000 lb, same load as a mossie*

14 Oct raid shows that each 303rd aircraft only carried 3,325 lb, 675 lb less than a mossie*

*conditional on the mossie having that range.

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



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.

17 August 1943, total incendiary tonnage dropped on Schweinfurt 128 tons, if the 303rd had 27 aircraft attacking as per Roger Freeman, that comes to 432x250 pound or 54 tons, Richard Davis says 40 tons dropped on V.K.F 1 works, Roger Freeman gives a summary of 1,017x250 pound incendiary bombs dropped on Schweinfurt, total 127.125 tons.

4 October 1943
Frankfurt-am-Main/Heddern 78 attacking, 186 tons HE, 33.3 tons Incendiary, total 219.3 tons, average load 5,623.1 pounds.
Wiesbaden 16 attacking, 46 tons HE, 0 tons Incendiary, total 46 tons, average load 5,750 pounds.

15 attacking 303rd BG times 6 tons is 90 tons, plus incendiaries, leaving the other 63 aircraft to drop at most 129.3 tons, around 4,100 pounds each.

Roger Freeman lists the load dropped Frankfurt as 372x500 pound, 180x1,000 pound HE, 666x100 pound incendiary, total 183 tons HE, 33.3 tons incendiary, by 77 aircraft, while Wiesbaden was attacked by 15 aircraft dropping 90x1,000 HE, so 92 attacking, but 92nd BG 17 sent, 17 attacking, 303rd 19/15, 305th 17/15, 306th 16/14, 379th 18/16, 384th 17/16, total 93 attacking.

10 October 1943,
Coesfeld 68 attacking, 116 tons HE, 71.4 tons Incendiary, total 187.4 tons, average load 5,511.8 pounds.
Dulmen 1 attacking, 3 tons HE, 0 tons Incendiary, total 3 tons, average load 6,000 pounds.
Munster 138 attacking, 207.5 tons HE, 143.5 tons Incendiary, total 351 tons, average load 5,087 pounds.
Enschede 29 attacking, 55.3 tons HE, 31 tons Incendiary, total 86.3 tons, average load 5,951.7 pounds.

20 attacking 303rd BG times 6 tons is 120 tons, plus incendiaries, leaving the other 48 aircraft to drop at most 67 tons, under 2,500 pounds each. 20 aircraft dropping 8.9 tons in total is also obviously wrong.

Roger Freeman lists the load dropped on Coesfeld as 396x500 pound, 34x1,000 pound HE, 1,428x100 pound incendiary, total 116 tons HE, 71.4 tons incendiary, 92nd BG 19 sent, 15 attacking, 303rd 20/20, 306th 18/18, 384th 18/15, total 68 attacking.

14 October 1943,
Schweinfurt/Kugelfisher 81 attacking, 165.7 tons HE, 0 tons Incendiary, total 165.7 tons, average load 4,091.4 pounds.
Schweinfurt/VKF 1 61 attacking, 63 tons HE, 74.1 tons Incendiary, total 137.1 tons, average load 4,495.1 pounds.
Schweinfurt/VKF 2 86 attacking, 166.5 tons HE, 13.5 tons Incendiary, total 180 tons, average load 4,186.1 pounds.

The 303rd would be below average with 3,500 pounds on board, possibly from still flying the shorter range early F models.

Roger Freeman lists the load dropped as 663x500 pound, 459x1,000 pound HE, 1,751x100 pound incendiary, total 395.25 tons HE, 87.55 tons incendiary, 229 aircraft attacking.

MiTasol said:

17 Aug raid shows that each 303rd aircraft only carried 4,000 lb, same load as a mossie*

14 Oct raid shows that each 303rd aircraft only carried 3,325 lb, 675 lb less than a mossie*

*conditional on the mossie having that range.

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Actually it was conditional on the Mossie holding a 4000lb bomb.
Which it didn't (in service) until February 23/24th 1944

Unless a Mossie, with bulged bomb bay doors, was carrying a 4000lb cookie it was limited to four 500lb bombs (with cropped fins) in the bomb bay and one 500lb bomb under each wing.
The Mossie's bomb bay simply would not hold more than about 2000lbs of normal GP bombs with the existing racks. And it was really lousy at carrying a number of lighter weight bombs. Like eight 250lbs or the American 100lb incendiaries.
The Mosquito was certainly one of the outstanding aircraft of WW II but the myth of the 4000lb bomb load rests squarely on the ability of later models of the Mosquito to carry a single 4000lb cookie using a bulged bomb bay and a few other modifications starting in Feb/March of 1944.

I believe the B MK XVI was the first to get the bulged doors with many Mk IXs and a few MK IVs getting them retrospectively in 1944. The larger doors did nothing for carrying more 500lbs in service (prototype 6 bomb racks were built/tested?) except for providing room for 1000lb target marking bombs for pathfinders.

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.

Plans for the bulged bomb bay doors on the Mossie B.IV arose in April 1943, with a prototype conversion, DZ594, flying in early July. Trials revealed more stability problems resulting in larger elevator horn balances being fitted as well as 60lb of ballast in the nose. 20 aircraft in total were modified to carry the 4,000lb bomb. 692 squadron began receiving these on 4 Feb 1944 and on 23rd Feb it dispatched 3 on the first ever Mossie mission to drop 4,000lb bombs.

While there were to be another 10 conversion kits produced only 1 seems to have found its way into a B.IX airframe.

All B.XVI (as opposed to PR.XVI) were to be equipped with bulged bomb bay doors on the production line. The first flew on 1 Jan 1944. The first deliveries were made to the Oboe equipped Pathfinder squadrons, where the increased altitude performance could be put to best use. The first use of this version was on the night of 10/11 Feb 1944, but it was March before they began to be used to drop 4,000lb bombs, by the units of the Light Night Striking Force.

It was the night of 13/14 April 1944 before Mossies (with 2x50gal drop tanks) began to drop 4,000lb bombs on Berlin or any other such distant target.