RAF bomb load item question

[33k in the air]

While looking at the ORBs for 77 Squadron, I came across this item in the bomb load for the Whitley V on the 23/24 April 1942 mission to Rostock. Here is exactly how it is listed:

8 S.B.C. (4 x 30, 4 x 20)

My first thought is that this means four SBCs filled with 30-lb bombs and four with 20-lb bombs. This suspicion is reinforced by the listing for the 26/27 April 1942 mission, also to Rostock, which included the item:

6 S.B.C. (8/20 lbs)

I do not believe there was a 20-lb incendiary bomb used by the RAF. Presumably, then, this is referring to the 20-lb fragmentation bomb, but SBCs normally carried 12 such bombs, not 8. Was this an SBC filled to less than full capacity? Or was it indeed a 20-lb incendiary? Or perhaps that first item description means four SBCs filled with 30 x 4-lb incendiaries and four filled with 20 x 4-lb incendiaries? If so, those are uncharacteristically light loads for SBCs in use at that time.

I tried to cross-check these loads by looking at the ORBs for 51 Squadron, which also flew the Whitley V at this time, and to the same target on the same days. That first Rostock mission lists the load as including "8 containers of incendiaries", which does not help clear things up. (Indeed, it would seem to point more to a 20-lb incendiary.) The second mission doesn't help either, as it was carrying fewer SBCs that the 77 Squadron aircraft, with the description being only "2 containers of incendiaries".

So, anyone have any info that might help clear this up?

 

[Greyman]

It's possible they meant the 25-lb incendiary bomb, which was carried 8 x per SBC.

 

[EwenS]

While looking at the ORBs for 77 Squadron, I came across this item in the bomb load for the Whitley V on the 23/24 April 1942 mission to Rostock. Here is exactly how it is listed:

8 S.B.C. (4 x 30, 4 x 20)

My first thought is that this means four SBCs filled with 30-lb bombs and four with 20-lb bombs. This suspicion is reinforced by the listing for the 26/27 April 1942 mission, also to Rostock, which included the item:

6 S.B.C. (8/20 lbs)

I do not believe there was a 20-lb incendiary bomb used by the RAF. Presumably, then, this is referring to the 20-lb fragmentation bomb, but SBCs normally carried 12 such bombs, not 8. Was this an SBC filled to less than full capacity? Or was it indeed a 20-lb incendiary? Or perhaps that first item description means four SBCs filled with 30 x 4-lb incendiaries and four filled with 20 x 4-lb incendiaries? If so, those are uncharacteristically light loads for SBCs in use at that time.

I tried to cross-check these loads by looking at the ORBs for 51 Squadron, which also flew the Whitley V at this time, and to the same target on the same days. That first Rostock mission lists the load as including "8 containers of incendiaries", which does not help clear things up. (Indeed, it would seem to point more to a 20-lb incendiary.) The second mission doesn't help either, as it was carrying fewer SBCs that the 77 Squadron aircraft, with the description being only "2 containers of incendiaries".

So, anyone have any info that might help clear this up?

You are correct, no 20lb incendiary for the RAF. The RAF did have a 20lb Fragmentation bomb dating from pre-war that was fitted with a normal or parachute tail unit. As well as being fitted directly to a light bomb rack, they could be fitted in SBCs as follows:-

8 in a 160lb SBC
12 in a 250lb SBC

This is a 1946 manual that contains details. Page 8 of the .pdf

https://bulletpicker.com/pdf/OP%201665,%20British%20Explosive%20Ordnance.pdf#page=202

This came from this site.

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bulletpicker.com

 

[33k in the air]

You are correct, no 20lb incendiary for the RAF. The RAF did have a 20lb Fragmentation bomb dating from pre-war that was fitted with a normal or parachute tail unit. As well as being fitted directly to a light bomb rack, they could be fitted in SBCs as follows:-

8 in a 160lb SBC
12 in a 250lb SBC

This is a 1946 manual that contains details. Page 8 of the .pdf

https://bulletpicker.com/pdf/OP%201665,%20British%20Explosive%20Ordnance.pdf#page=202

This came from this site.

Home

Ordnance, Explosives, and Related Items The Bulletpicker site or software is not to be considered Demining, Unexploded Ordnance (UXO), or Explosive Ordnance Disposal (EOD) inf

bulletpicker.com

Thanks! That seems to answer the question.

I've downloaded quite a few manuals from the Bullet Picker site, including the one you mentioned, but I'd never read the details in that part of it. I guess I'm going to have to go through it again more carefully.

 

[Geoffrey Sinclair]

Bomber Command Monthly Summaries, the tables do not mention bomb containers.

23/24 April 1942, Whitley 19 despatched, 16 attacked primary target, 3 no attack, 2x1,000 pound GP, 6x500 pound GP, 30x250 pound GP, 7,830x4 pound incendiary, 1 Whitley missing. 1 category B damage, not enemy action.

26/27 April 1942, Whitley 7 despatched, 6 attacked primary target, 1 another target, 5x1,000 pound GP, 5x500 pound GP, 39x250 pound GP, 96x30 pound incendiary, 360x4 pound incendiary, 1 Whitley missing. 1 category A and 1 category AC damage due to enemy action.

There were 216x30 pound incendiary dropped on 23/24 April 1942 by Wellingtons.

Other Whitley incendiary bomb totals for April 1942, 5th 2,000x4, 12th 1,440x4, 24th 2,160x4, 25th 26x250, 88x30 and 3,180x4 pounds

 

[33k in the air]

23/24 April 1942:

51 Squadron dispatched 12 Whitley V (11 attacked)
. . . 2 aircraft carried 1 x1,000-lb GP, 3 x 500-lb GP, 2 x 250-lb GP
. . . 9 aircraft carried 2 x 250-lb GP, 8 containers of incendiaries

77 Squadron dispatched 7 Whitley V (5 attacked)
. . . all aircraft carried 2 x 250-lb GP, 8 x SBC (4 x 30, 4 x 20)

26/27 April 1942:

51 Squadron dispatched 3 Whitley V (all attacked)
. . . all aircraft carried 1 x1,000-lb GP, 1 x 500-lb GP, 4 x 250-lb GP, 2 containers of incendiaries

77 Squadron dispatched 4 Whitley V (1 attacked Rostock, 2 attacked Dunkirk)
. . . 1 aircraft carried 1 x 1,000-lb GP, 1 x 500-lb GP, 6 x SBC (8 x 20-lbs) (Rostock)
. . . 2 aircraft carried 14 x 250-lb GP (Dunkirk)

The above is according to the ORB of the respective squadrons. I'm not sure how to reconcile these with the Bomber Command Monthly Summaries figures.

 

[Geoffrey Sinclair]

according to the ORB of the respective squadrons. I'm not sure how to reconcile these with the Bomber Command Monthly Summaries figures.

So am I to an extent.

In 1941/42 the 4 pound incendiaries tended to be dropped in groups of 60. The next size up I know of is the number 14 cluster carried 106, the 17 with 110 and the 15 with 158. Similarly the 30 pound incendiaries tended to be dropped in groups of 8 or 16. Given 8x30 = 240, 16x30 = 480, 60x4 = 240, 106x4 = 424, 110x4 = 440, roughly 250 or 500 pounds after adding container weight. Of course there are exceptions to this due to things like hang ups, Wellingtons on 14/15 April 1942, 47,141x4 pound, next night 11,295.

I do not have the night raid sheets for early 1942, just the preliminary reports.

23/24 The preliminary raid report has 16 Whitley attacking Rostock, 2x1,000, 6x500, 30x250 HE and 7,700x4 incendiary, which became 2x1,000, 6x500, 30x250 HE and 7,830x4 incendiary in the final report. So 2x250 pound bombs not dropped to reconcile with the ORB HE totals but no mention of this in the ORB.

The incendiaries are the problem, the monthly summary says no 30 pound ones dropped, while the 7,830 four pound reported dropped is 130.5 containers of 60 while the 112 containers of 60 carried comes to 6,720, or 1,110 less, if 20 containers are bigger they would need to carry 115.5 incendiaries each, the number 14 cluster carried 106, the 15 carried 110. Assuming the containers are 60x4 pound the HE only aircraft had 3,000 pounds of bombs, those carrying incendiaries 2,500 pounds, adding one extra incendiary container to each aircraft already carrying incendiaries makes the total 126 containers, still leaving the 4 pound incendiaries dropped 270 short of the official total, adding 2 extra containers gives 570 more than the official total. More information is needed.

26/27 April The preliminary raid report has 5 Whitley bombing Rostock, 5x1,000, 5x500 HE plus 16x250, 48x30, 480x4 incendiary and 2 Whitley bombing Dunkirk with 27x250 pound HE. The missing Whitley is credited with attacking Rostock. Z9261 of 77 squadron reports the hang up and subsequent jettison of a 250 pound HE bomb. According to Richard Davis 1 aircraft bombed Calais with around 800 pounds of HE bombs, this is not in the preliminary raid report.

The 51 squadron ORB notes the 250 pound bombs carried were incendiary, which agrees with the preliminary raid report but not the monthly summary. The 4 and 30 pound incendiary loads in the preliminary report are another matter.

As two 77 squadron carried the 1,000+500 HE bombs +6 incendiary containers load it would be 77 squadron carried 12x8x30 pound (but 8/20 pound in the ORB), while the 51 squadron aircraft carried 6x60x4 pound, assuming uniform squadron loads. 51 squadron had around 3,000 pounds of bombs, 77 squadron incendiary carriers 3,000 pounds, the all HE loads 3,500 pounds.

So the 26/27 April raid reports seem to be reconcilable.

How are the incendiary loads for the other April 1942 raids described? Versus the monthly summary totals.

 

[MiTasol]

 

[33k in the air]

In 1941/42 the 4 pound incendiaries tended to be dropped in groups of 60. The next size up I know of is the number 14 cluster carried 106, the 17 with 110 and the 15 with 158. Similarly the 30 pound incendiaries tended to be dropped in groups of 8 or 16.

From what I've come across, there was a smaller SBC developed for the Hudson (160-lb class) which carried 40 x 4-lb incendiaries. The 250-lb class SBC, as shown MiTasol's post, carried 60 x 4-lb incendiaries, but this was later raised to 90. If you look at the diagram, you can see empty space above the 60 x 4-lb arrangement, which presumably got used up in a revision to increase the capacity to 90 overall, with each compartment holding 30 instead of 20 of the 4-lb incendiaries. (A similar expansion in capacity seems to have happened with the 40-lb GP bomb, with it originally holding 3 per compartment, or 6 in total, but with space apparently available to add more, according to the diagram. Overall capacity was apparently raised to 8 x 40-lb GP bombs, with 4 per compartment.)

There was a larger SBC introduced later which held 150 x 4-lb incendiaries (although on occasion it seems it was only filled with 100 bombs, according to a few ORB entries).

The 250-lb class SBC held 8 x 30-lb incendiaries. There were also SBCs holding 12 x 30-lb and 16 x 30-lb, but i don't know if these were separate containers or the same container with a lighter load of 30 pounders.

The '17' cluster is a confusing point, because there was the No. 17 Cluster Projectile from the RAF which held 26 x 20-lb fragmentation bombs, and the U.S. AN-M17 aimable cluster which held 110 x 4-lb incendiaries. Fragmentation bombs were sometimes dropped by heavy bombers (a couple of PFF missions have these mentioned in the bomb load).

 

[PETERTHEEATER]

While looking at the ORBs for 77 Squadron, I came across this item in the bomb load for the Whitley V on the 23/24 April 1942 mission to Rostock. Here is exactly how it is listed:

8 S.B.C. (4 x 30, 4 x 20)

My first thought is that this means four SBCs filled with 30-lb bombs and four with 20-lb bombs. This suspicion is reinforced by the listing for the 26/27 April 1942 mission, also to Rostock, which included the item:

6 S.B.C. (8/20 lbs)

I do not believe there was a 20-lb incendiary bomb used by the RAF. Presumably, then, this is referring to the 20-lb fragmentation bomb, but SBCs normally carried 12 such bombs, not 8. Was this an SBC filled to less than full capacity? Or was it indeed a 20-lb incendiary? Or perhaps that first item description means four SBCs filled with 30 x 4-lb incendiaries and four filled with 20 x 4-lb incendiaries? If so, those are uncharacteristically light loads for SBCs in use at that time.

I tried to cross-check these loads by looking at the ORBs for 51 Squadron, which also flew the Whitley V at this time, and to the same target on the same days. That first Rostock mission lists the load as including "8 containers of incendiaries", which does not help clear things up. (Indeed, it would seem to point more to a 20-lb incendiary.) The second mission doesn't help either, as it was carrying fewer SBCs that the 77 Squadron aircraft, with the description being only "2 containers of incendiaries".

So, anyone have any info that might help clear this up?

It should be helpful to understand that early war the 4 pound IB was supplied in hermetically sealed cans of 20 later superseded by cans of 30. Bombs were not supplied as individual units but in quantities of 20 or 30 pre-packed at the factory. The bombs were packed in such a way that the spring-loaded Safety Plunger of each bomb was kept in place by an adjacent bomb.

SBCs were loaded in the bomb store using a cradle in which they could be rotated 180 degrees so that the open (bottom) faced upwards. The Drop Bars were rotated away and cans of IBs placed into the SBC. The covers of the hermetically sealed cans were ripped off and discarded and the Drop Bars rotated into position and locked to the Release Units. The SBC could now be rotated back to its normal position, suspension lug uppermost and removed from the loading cradle ready for transportation to the aircraft.

Imperial War Museum website has some images to help explain this:

ROYAL AIR FORCE BOMBER COMMAND, 1942-1945.

Armourers preparing fire-bombs at RAF Marham, Norfolk. Having secured three cases of 4-lb incendiaries in the Small Bomb Container, airmen roll the SBC through 180 degrees in order to secure the carrier to the top.

www.iwm.org.uk

ROYAL AIR FORCE BOMBER COMMAND, 1942-1945.

Armourers preparing fire-bombs at Marham, Norfolk. Here, two airmen place the tinned plate case of 4-lb incendiaries into a Small Bomb Container (SBC). The lifting handles, when reversed, secure the case in the container.

www.iwm.org.uk

ROYAL AIR FORCE BOMBER COMMAND, 1942-1945.

Armourers preparing fire bombs at RAF Marham, Norfolk. Here trolleys loaded with Small Bomb Containers (SBCs) with their carriers attached, are awaiting delivery to aircraft.

www.iwm.org.uk

 

[MiTasol]

You might find more info in this book if the RAF Museum or the Brit Archives have a copy.

 

[MiTasol]

Scrub the above - found out more on that particular unit

 

[Geoffrey Sinclair]

The bigger (100+) incendiary containers only appeared in 1944.

So the 250 pound SBC could at times be loaded with 360 pounds of 4 pound incendiary bombs and the container could cope with the extra weight? Or was a mistake made or a trial run with all 3 compartments with filled 30 bombs when it normally should have been 2 compartments. Mathematically to obtain 7,830 incendiaries from 112 containers you need 27x90 + 75x60.

Now for unsupported speculation, 77 squadron, 5 aircraft each with 4x30 and 4x20, assuming the 30 and 20 refer to the number of 4 pound bombs in each SBC compartment, gives 20 of the heavier containers, the 9 aircraft of 51 squadron each had 8 containers of incendiaries. Assume each 51 squadron aircraft had 1 heavier container and to reconcile the different reports it requires 1 group of 60 incendiaries not dropped. Alternatively 51 squadron did not achieve a uniform load across its aircraft and only 7 carried a heavier incendiary containers. Maybe.

According to the the Bomber Command Wartime Summary the Whitley in 1942 dropped 50x250, 1,898x30 and 67,459x4 pound incendiaries, out of a wartime total of 50x250, 290x50, 1,898x30 and 851,495x4 pound. In January 1942 Whitleys are credited with dropping 14,940x4 pound incendiaries, which equals 249x60, no incendiaries dropped in February and March, then 16,970 in April which is not divisible by 60, falling 10 short. The incendiary totals dropped in May and June are NOT divisible by 60, those in July and September are.

Of the 6 nights Whitleys dropped incendiaries in April 1944 the 5/6th with 2,000 and the 23/24th with 7,830 are not divisible by 60. Is it worth checking the ORBs for the number of incendiary containers carried during April 1942? Also for the record the January dates are 2/3, 5/6, 7/8, 8/9, 10/11, 15/16, 17/18.

On the 23/24th of April 1942 Wellingtons dropped 27,540x4 pound incendiaries, Hampdens 360, both divisible by 60 and 90.

 

[33k in the air]

It should be helpful to understand that early war the 4 pound IB was supplied in hermetically sealed cans of 20 later superseded by cans of 30. Bombs were not supplied as individual units but in quantities of 20 or 30 pre-packed at the factory. The bombs were packed in such a way that the spring-loaded Safety Plunger of each bomb was kept in place by an adjacent bomb.

Ah, okay. I wasn't aware of the shipped container arriving with 30 instead of 20. That would explain the rise in capacity. (There is still the increase from 6 to 8 x 40-lb GP bombs).

The AP 1661B Vol. 1 manual can be found online at the Bullet Picker website.

Now for unsupported speculation, 77 squadron, 5 aircraft each with 4x30 and 4x20, assuming the 30 and 20 refer to the number of 4 pound bombs in each SBC compartment, gives 20 of the heavier containers, the 9 aircraft of 51 squadron each had 8 containers of incendiaries.

That does fit. Although when I saw the later explicit reference to 20-lb bombs, that's what made me question the earlier listing. But perhaps that later reference to 20-lb bombs is a typo or misunderstanding in the ORB, and it was actually supposed to be a reference to compartments containing 20 x 4-lb incendiaries instead of 20-lb bombs.

 

[MiTasol]

The AP 1661B Vol. 1 manual can be found online at the Bullet Picker website.

Interesting, Thank you - my web search only found the electric detonators on that site and missed the other two.

 

[33k in the air]

Interesting, Thank you - my web search only found the electric detonators on that site and missed the other two.

There are a lot of WW2-era ordnance manuals on that site. It's well worth looking through its library.