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Selwyn

Blenheim Bombloads

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Selwyn    1,308

The Blenheim maximum bombload was 1000lb and was usually carried as 4 x250lb bombs.

Could the Blenheim carry 2 x 500lb?, I have had a look but I haven't come across any references or images of this bombload configuration.

The only other bombload variation I have found is the Aircraft carrying Small bomb containers with the Bomb doors removed.

Any Ideas?

Selwyn

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Kari Lumppio    50

Hello!

At work now and will not have time to check at home either so this comes from memory. Caveat!

I believe RAF Blenheims could not carry 500 lb bombs and Finnish Blenheims cannot really be compared to.

Finnish-built sarja II Blenheims could carry 250 kg (~500 lb) bombs but these had deepened bomb bay and AFAIK the well was also lengthened forwards up to the pilot seat mounting (some 10 cm ~4 in???). I do not remember offhand if the bomb bay roof was higher (in any case it was strengthened) or if the doors were made deeper only. It may be the latter case. In the sarja V (short nose) and sarja VI (long nose) Finnish built serieses the bomb bay doors were given yet another form and shape and these could also take the 250 kg bombs.

Sarja I Blenheims were built in Britain to Finnish specification and did have the open bomb bay seen in the linked photos. Eight 100 kg plus four smaller (12,5 kg?) total in the wing lockers (two in each side) was the maximum. I am pretty sure this version did not have bomb racks capable to take 250 kg bombs.

As a curiosity can be mentioned that Small Bomb Carrier and the incendiary bomb cassette within the rear fuselage (dropping through the bottom hatch opening) were used operationally in Finland.

Bye for now,

Kari

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Test Graham    275

This is only memory, and therefore unreliable, but I recall comment on Blenheims with two 500lb bombs providing the bombbay doors were removed. Certainly not four - that would require a longer bombbay as described for the Finish ones. This in itself is somewhat surprising, as presumably the space was used for something on the standard type?

Under normal British practice the carriers would not be part of the permanent bombbay structure, so perhaps the Sarja 1 order simply didn't request them? (Or perhaps the Blenheim was different in that respect?)

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Nick Millman    1,752

Surprising what they dropped. When they attacked Mingaladon on 21st March 1942 some of them dropped anti-submarine bombs which the crews reckoned were more effective against the parked Japanese aircraft than GP bombs.

Sqn Ldr Hughes of 45 Sqn wrote in his journal on 20th Feb 1942:-

"Any and every kind of bomb is used: 11 sec delays ran out long since; 250lb GP, ASP and AS have been used up and now 500 pounders are being carried."

Z7892 was recorded as being armed with four 250 pounders and eight 40lb incendiaries whilst the crew heaved another eight 40lb HE and forty 4lb incendiaries out of the camera hatch for a total of 1,800 lb, almost twice the normal bomb load. In the desert 45 Sqn's standard load was 4 x 250lb but they also carried 40lb GP, 20lb fragmentation and 25lb and 4lb incendiaries "and the occasional 500 pounder".

I seem to recall an old set of plans in Scale Models that showed the Blenheim bomb bay load configurations - I'll have a look.

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Procopius    16,848

I'd have to go back and look, but I'm pretty sure 11 Squadron used 500-pound bombs when they attacked the Japanese carriers in the Indian Ocean.

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JohnT    2,016

From Bristol Blenheim In Action Squadron /Signal publications Page 28

Blenheims of Number 2 Group were involved in attacks on Germany proper. On 4th July 1941 12 blenheim MkIVs led by Wing Commander "Hughie" Edwards of 105 Sqn bombed Bremen. All hit the target but 4 were shot down. Edwards got the VC. On 12 August 54 Blenheims attacked the power stations at Quadrath and Knapsack outside Cologne.

"Carrying two 500 pound bomb each, the Blenheims inflicted moderate damage to the targets however ten of the Blenheims were lost to enemy action"

also the Crowood book on the Blenheim tells of 18 and 82 Sqns attacking Keil and has a report from Tony Mee, a Sgt WO/ air gunner who says of the attack "....as we bore down on them and Bill (the pilot) dropped the two 500 pound armour piercing bombs with their 11 second delay fuses just before passing low over the vessel."

Look like they did indeed carry 500 pounders then

Edited by JohnT

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Selwyn    1,308

Thanks for all the info guys, (BTW I should have specified RAF Bombloads)

I could only find one image on line of the Bomb bay with bombs which shows 2x 250lb loaded. these were side by side in one of the two sections, not one behind the other which was my impression. A 500lb bomb must have just have fit in there, it must have been tight length wise.

Selwyn

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Test Graham    275

Just to back the last comment up: The Mosquito bombbay was designed for 4x250lb, and could only carry 4x500lb if the tail fins/ring was shortened. Such shortened tails can also be seen on Typhoons, so I suspect it became the new standard, but would have been too late for the Blenheim.

Does your photo show doors?

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Selwyn    1,308
Just to back the last comment up: The Mosquito bombbay was designed for 4x250lb, and could only carry 4x500lb if the tail fins/ring was shortened. Such shortened tails can also be seen on Typhoons, so I suspect it became the new standard, but would have been too late for the Blenheim.

Does your photo show doors?

Graham

Yes the doors are in place but propped open (I know that they were held closed normally by bungee cords)

Blenheim bombing up

The bombs look to be 250Lb using a rough estimate of the Groundcrewmans open hand a 250LB bomb was 10.2 inches wide at its maximum point.

Selwyn

Edited by Selwyn

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Nick Millman    1,752

There is a website here that has full details of Blenheim armament but currently it won't load as the server is not responding. It says:-

"Blenheim armament

Bombs, bombs, bombs...

The following discussion derives from many sources, primarily official (the once secret RAF Armament Volume I: Bombs and Bombing Equipment (Air Ministry 1954), its companion Volume II: Guns, Gunsights, Turrets, Ammunition and Pyrotechnics (Air Ministry 1954) and a selection of the various Armament Air Publications); and the personal records, photographs and recall of the participants. The better published works have also been drawn upon.

The sharp end (RAF official)

A 250lb GP Mark IV bomb, still nose-lugged (ie unfused), in the standard mustard yellow of the early war years, with tin fins attached but apparently unpainted, sitting on a bomb trolley. In the original, it is possible to read the stencilled bomb type.

The sharp end: prime armament

From 1935 onwards, development of the Mark IV series of General Purpose (GP) bombs included new 40lb, 250lb and 500lb armament, and the 20lb (F) anti-personnel fragmentation bomb. The Mark IV series, approved from September 1936, saw two notable improvements from the Armourer’s point of view:

Snap-on tail units (where spring clips in the tail unit engaged a mounting groove on the bomb casing) replaced the old screw-on type. To prevent accidental damage on the ground (leading to poor ballistic performance in the air), the tail units were stored in individual canisters and attached by the armourers as part of the fuzing process.

For fusing, the now built-in exploders required only arming by pistol and detonator, nose or tail.

Having devoted a lot of effort in the late 1930s to redevelopment of the Mark IV GP series of medium capacity general purpose bombs, the RAF found it difficult (both doctrinally and in squadron operations) to surrender this smaller armament, let alone accept the relative ineffectiveness of the small charge-to-weight ratios employed (around 30%) and their high detonation-failure rate (10-15%).

The size of bomb-bays in RAF aircraft and the perceived chance of a hit were both real considerations in this early period. During 1940, use of the smaller ordinance (over 2,000 20lb F; over 26,000 40lb GP; nearly 62,000 250lb GP) far outstripped that of the 500lb GP (just over 20,000).

It was late 1942 before development of the Medium Capacity series bore fruit, with their higher charge-to-weight ratios of 40% or more and better filling, while the much larger High Capacity series, with ratios in the 80% plus range, took rather longer to perfect.

Bomb loading

The Bristol Blenheim bomb-bay was divided into two cells laterally by a full-depth vertical bulkhead, fore-and-aft along the fuselage centreline. Mounted on the Type A universal carrier, 500lb GP or 250lb GP bombs were winched into place in the bomb-bay. The 20lb F and 40lb GP bombs might be mounted either individually on the external Light Series Carrier (the LSC), or in the Small Bomb Container (the SBC, the rectangular, re-usable alloy canister winched directly to the bomb-bay). Possible internal bomb loads included:

2x500lb (one per cell) or

4x250lb (two side by side, each cell) or

4xSBC (two side by side, each cell) or

Standard Small Bomb (SSB) load: 2x250lb plus 2xSBC of 12x20lb, as 1x250lb and 1xSBC side by side in each cell, the SBCs mounted inboard.

The 4xSBC arrangement necessitated removal of the bomb-bay doors.

Bristol Blenheim bomb-bay loadings (D Clark)

The diagram (not to scale) shows three examples:

4x250lb, left

4xSBC, centre

SSB load: 2x250lb plus 2xSBC, right.

The Type A universal carrier

The Type A universal carrier (RAF official)

The fitting of either the 500lb GP or 250lb GP bomb represented: fuzed and securely “in the jaws”, attached by its casing lug to the slip-catch of the Universal Carrier, and snug against the carrier’s adjustable crutches once hand-winched into place in the bomb-bay.

The Light Series Carrier (LSC)

In the Mark I Blenheim, there were mountings for two LSCs under the fuselage, installed fore-and-aft just aft of the bomb-bay. It is occasionally reported that some Mark IVs also had under-wing hard-points for LSCs (yet other sources report a wing-root cell for two 4FL flares or practice bombs, abaft the main spar).

Light Series Carrier (RAF official)

Capacity 4x40lb or 4x20lb bombs.

The Small Bomb Container (SBC)

The SBC was a practical but still tedious and potentially dangerous solution to the armourer’s problems of bombing-up with small ordinance and their safe release or retrieval.

The SBC was capable of carrying a wide variety of weapons. It was produced in various sizes: the two-partition 160lb Hudson unit, the 3 or 4 partition 250lb unit commonly used in Blenheims and shown below, and a larger unit used in the Lancaster. Intentionally light in construction and with relatively complex electrical and mechanical fittings, the SBC needed careful handling and storage and was not to be found lying around in outdoor bomb-dumps.

250lb SBC Mark 1A (RAF official)

The illustration from Air Publication AP 1664 Bomb Carriers shows the 250lb SBC as used in the Blenheim, viewed from the underside as for loading by the armourers.

Key:

1 EM Unit [the Type L slip-catch release];

2 Partition;

3 Drop bar;

4 Link plate;

5 Dropbar bracket;

6 Locating plates.

Forward is to the left. The arrowed instruction inside the empty front partition reads “Bombs to point in this direction”. A single canister of incendiaries has been loaded in the centre partition, located with the aid of the movable partition plate and locating plates. The contents are secured with a single drop bar, locked in its EM electromagnetic release at one end and in the hinge bracket at the other. On release, the EM unit will activate its Type L slip release catch, leaving the drop bar free to fall clear away under the weight of the ordinance. Crews occasionally resorted to dropping 250lb loads “safe” on the ground. The technique for jettisoning SBCs and LSCs required the attentions of the “plumbers” and rather more care.

Once prepared for the required bomb-load, with the correct number of partitions and release catches arranged to match, the container was placed, open side up, in its detachable two-piece loading cradle. With ordinance loaded and retaining drop bars engaged, a separate lifting cradle or frame was then also attached. Next, the loading cradle was used to roll the entire assembly over. The loading cradle was now detached, leaving the SBC “right side up” with respect to the bomb-bay and ready to be carried, by its lifting cradle, to the aircraft by hand or by bomb-trolley. Once winched into place in the bomb-bay, the lifting cradle was removed.

The bomb load of the open-faced SBC, however made up, was packed horizontally fore-and-aft into the container. The number of partitions, drop bars and internal packing pieces varied according to the make-up of the bomb load. The maximum load per 250lb SBC was either

6x40lb GP bombs (three per partition, two bars employed) or

12x20lb F bombs (four per partition, three bars employed), or

3 cans of 20 Mark 1E (or later Mark) 4lb incendiary sticks (one can per partition, three bars employed).

For the 20lb and 40lb bombs, purpose-made packing pieces secured the individual bombs as a cluster within each partition. The 4lb hexagonal incendiary sticks came pre-packed in tin-plate boxes or “cans”, with a tear-off lid, 20 per box (80lbs). In each case, the loaded SBC carried 240lbs of armament.

Air Publication 1664 Bomb Carriers, Vol I Ch 3 The 250lb Container for Small Bombs (circa 1939) gives a full description of the 250lb SBC, with packing methods and diagrams for the various types of armament. The SBC is also covered by the Armourer’s Handbook circa 1942.

Other Marks of the SBC could carry more ordinance, and for example the incendiary canister later came to be packed with 30 4lb sticks (360lbs per SBC), rather than the 20-pack (240lbs per SBC) used for Blenheim operations."

Bristol Blenheim Armament

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Selwyn    1,308

Thanks for that Nick, just the information I require. I have a lot of imformation on the 250/500lb stores anyway it was just the confirmation of the 2 x 500lb fit.

I have two Frog Mk 1 Blenheims in build. One I intend to depict with a Bombload ready next to the aircraft the other I am seriously looking at the SBC load. I think it will look good with the SBC showing and no bomb doors. but it looks like I will have to Scratchbuild as the only SBC's available (Belcher bits) are the larger type used on Lancs.

The main reason for removing the bay doors was that the larger bombs when dropped just pushed past the doors against the bungee tension and into the airstream, and the doors then sprung closed. There was no facility for the Blenheim pilot to "open bomb doors" in flight. If they had tried this while dropping small AP bombs or 4Lb incendiaries there was a potentially fatal risk that the stores would be caught or trapped by the sprung loaded doors, hence their removal.

From the one image I have seen (of a Mk 1 Blenheim) of the SBC fit I also suspect that the doors could not close flush over the SBC anyway. I have heard that the outer doors were sometimes left on as they were held open by the SBC sides, but I think that they would probably have vibrated badly in the airstream in flight.

I also have doubts on using a 4lb incendiary loaded SBC in the Desert. My logic says that incendiaries are used to set fire to things and the desert is not a place where there is a lot to burn! So I may build the SBC's with Frag bombs instead, as I feel that that may be a more appropriate load for that theatre.

I won't be using the Light series carriers that come with the kit as these are not just a poor depiction of the carrier, they are effectively just a row of small bombs with a locating pin! Saying that these bombs might look good seperated individually in the SBC's!

I do have access to dimensional drawings of the light series carriers and type A EMRU that is used on this carrier so that would not be a problem if I did change my mind and decide to go down that route.

Selwyn

Edited by Selwyn

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Nick Millman    1,752

Don't be so sure about the incendiaries in the desert! 45 Sqn again:-

"During the five days that the squadron had operated in close support of the 7th Division they had flown seventy-one sorties in the course of which they had delivered a total of 53,560 lbs (about 24 tons) of ordnance comprising 124 x 250 lb bombs, 510 x 40 lb bombs and 540 x 4 lb incendiaries."

In other words they dropped more incendiaries than 250 pounders!

The more I read about Blenheim ops in relation to other studies the more admiration I have for the aircraft and its crews. Unsung, under-rated and definitely under-represented on the modelling tables. I do hope Airfix see fit to rectify this in due course.

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Selwyn    1,308
Don't be so sure about the incendiaries in the desert! 45 Sqn again:-

"During the five days that the squadron had operated in close support of the 7th Division they had flown seventy-one sorties in the course of which they had delivered a total of 53,560 lbs (about 24 tons) of ordnance comprising 124 x 250 lb bombs, 510 x 40 lb bombs and 540 x 4 lb incendiaries."

In other words they dropped more incendiaries than 250 pounders!

The more I read about Blenheim ops in relation to other studies the more admiration I have for the aircraft and its crews. Unsung, under-rated and definitely under-represented on the modelling tables. I do hope Airfix see fit to rectify this in due course.

Nick thanks for the Pictures. I already have some of these but the others are still interesting.

In the first picture have you noticed that they are winching two different sizes of SBC together? one is definately shorter in length than the other and contains a different type of bomb. I know that there were several sizes of SBC but it looks like there was far more variation in this than I realised.

As an ex RAF Armourer (and still in the same line of work) I am very interested in the history of British air dropped weapons. To me one of the greatest scandals of WW2 that has never been properly brought to life was the saga of the development of British GP bombs, which were manufactured in great numbers despite being woefully under tested. These bombs under operational conditions proved to be horrendously unreliable in operation, regularly broke up on impact, and when they did explode did not do much damage. It was reckoned that the equivelant German 250 KG bomb produced twice as much damage as the British 500Lb GP. which was eventually the main driver for the hurred development of the wartime MC class bombs.

I too have deep admaration of the Blenheim (and Battle) Crews especially in the early part of the war. My heart goes out to those poor light bomber crews in France in 1940 who took tremendous risks and too often lost their lives against impossible odds to stem the german advance, and if they got through they were too often dropping sub standard weaponry that had little or no hope of damaging the designated target.

I don't you know if you have read a book called " On Valiant Wings" By Norman Franks. its the story of the RAF in the Battle of France. Essential reading for a student of the Battle or Blenheim. They were very brave men.

Selwyn

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The Wooksta!    1,576

The Graham Warner book on the Blenheim is well worth reading. And weep at the waste of crews.

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Nick Millman    1,752
Nick thanks for the Pictures. I already have some of these but the others are still interesting.

Selwyn

Pics kindly posted by hwallen1410 not me! Thanks for the tip about the Valiant Wings book - I have not read it but will try to do so.

Regards

Nick

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Selwyn, you may find these three graphics out of AP1530B Vol 1 of interest.

bombbay3.jpg

bombbay2.jpg

bombbay1.jpg

The Blenheim definitely could carry 2 x 500lb, the pick up point for the bomb carrier was located centrally in each of the two bays. 250 lb ordnance was carried in pairs on a special frame as detailed in the drawings. 250 lb ordnance could be either GP or AP or AS bombs or SBC's or any combination of these.

Removal of the bomb doors was only required when carrying the so-called "B" or buoyance bombs (as per AP1530 B but I am not sure that this type of bomb was ever used operationally) and when carrying SBC's.

I initially thought the door removal was necessary because of the doors interfering with the SBC's release bars but have since seen photos that clearly show that the SBC's protrude out of the bomb bays far enough for the doors not to be able to close at all.

Also, when carrying a mixed load of say 2 x 250 lb GP and 2 x SBC, the SBC's would be carried innermost, next to the so-called keel plate that divides the bomb bay in two compartments and as far as I have been able to find out, only the inner doors would have to be removed, the outer ones could stay in place.

Finally, the Mk I and Mk IV Blenheims have a total of 8 bomb doors, each door consisting of a front and rear section connecting via a male/female "V" join in the middle so actually 4 doors per bay. I know from a former 18 Sqn Cpl airframe rigger, sadly now deceased, that it was a hell of a job to remove those doors. On the Mk V the bomb bay set up is similar but they added even more doors, each door now consisting of four parts, the front and rear portions being smaller and just long enough to cover the gap between the bay ends and the protruding SBC's.

Cheers,

Walter

Edited by Walter Lindekens

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Selwyn    1,308

Cheers,

Walter

Walter

Thanks very much for this information its just what I was looking for!

Selwyn

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