Talk:Grand Slam (bomb)

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The original design plans are important[edit]

The original design plans are important, and these were for a bomb designed to use the earth underground as a shockwave transmission medium. This scomes form the paul brickhill book on the dambusters.

"The design was very aerodynamic with a tail which caused it to spin. This allowed it to break the sound barrier as it fell."

How? - Omegatron 03:16, Apr 25, 2005 (UTC)

No expert on aerodynamics, but I'd take a guess there are two factors. Firstly, and most importantly, the spin produces a gyroscopic effect so that the bomb is kept upright as it falls. If this did not happen then the very high turbulence experienced as the speed of sound is approached would cause the bomb to tumble off its axis and to slow. Secondly, I think the spinning will probably produce some sort of effect around the bomb that will reduce the resistance to the fall. That second point may be wrong, though.

Your second point is incorrect, I think, but you're spot on wit hthe first. To say "it allowed" it to break the sound barrier is a little misleading, though, since the spinning slowed the bomb directly (resistance with the air is used to produce rotational motion), but the consequences of that spinning (not tumbling as it falls, as well as being less vulnerable to drafts and breezes) would probably improve the top speed. Of course, it it was dropped in dead air and from a stationary position such as a tower or zeppelin, it would fall faster with regular flights. This is an unliekly situation, so I'll exclude it for now. Oceanhahn 05:29, 25 May 2006 (UTC)Reply[reply]

The article also quotes 2,358kg of explosive, the same number as for the Tallboy bomb. Is that right?

-- 03:45, 24 May 2005 (UTC)Reply[reply]

Grand Slam contained approx 9,200 lb of Torpex. Tallboy, 5,200 lb. — Preceding unsigned comment added by (talk) 11:50, 20 February 2015 (UTC)Reply[reply]

Different facts[edit]

As so often, regarding the Valentin submarine pens, the german article claims they only had 5 metres thick roofs and the Grand Slam bomb could not break through them (and the RAF website times out). -- Darklock 00:55, 26 June 2006 (UTC)Reply[reply]

Duplicated content[edit]

"he redesigned the Tallboy accordingly. The design was very aerodynamic with a tail which caused it to spin. This allowed it to reach supersonic speeds as it fell. It had a much thicker case than the typical World War II bomb so that it would survive the impact of hitting a hardened surface. Its hardened casing was cast in a single piece in a sand mold, using a concrete core. When dropped onto compacted earth it would penetrate over 40 meters into the ground. The explosion would leave a 'cavern' which would undermine foundations of structures above causing collapse."

This is a bit misleading. It reads as if this description relates specifically to the Grand Slam, but most of it also features in the Tallboy article. TheMadBaron 09:27, 13 August 2005 (UTC)Reply[reply]


keep separate as different weapons with different missions. GraemeLeggett 20:06, 13 August 2005 (UTC)Reply[reply]

Definitely keep separate[edit]

They are different bombs. If we merge these, then we must merge Fat Man and Little Boy to be consistent. Does not compute./ Moriori 22:18, August 13, 2005 (UTC)

Not a good analogy: those used radically different bomb architecture (plutonium/implosion and uranium/gun), while Grand Slam was just an upsized version of Tallboy.
Try the .50 calibre round and .30-06. Virtually the same, except one is larger. Should they be merged? Moriori 19:43, August 14, 2005 (UTC)
Was one literally an adaptation of the other, a development by the same designer? I haven't said Grand Slam and Tallboy should be merged, just that the duplication because of common origin should be snipped. Tearlach 23:50, 14 August 2005 (UTC)Reply[reply]
Yes, I think one would have been literally an adaptation of the other, but I don't know which was chicken or egg. ):- Moriori 00:00, August 15, 2005 (UTC)
I'd say keep them separate, but cut the duplicated material in Grand Slam and refer to Tallboy for the general background principles. Tearlach 19:04, 14 August 2005 (UTC)Reply[reply]

Keep then seperate do not cut the duplicate material as it is not a lot and was true for both bombs. It is not as if it uses either a lot of disk space, bandwidth or screen space. PBS 00:47, 1 September 2005 (UTC)Reply[reply]

Also the paragraph mentions the only type of British bomber which could carry the Grand Slam.I have also mentioned that the fist use against the enemy involved destroying the foundations by a proximity drop not a direct hit. PBS 01:19, 1 September 2005 (UTC)Reply[reply]


I don't think that tagging on to the bottom of this page, "the US developed an even bigger bomb"(that was never used operationally)serves any useful purpose. I'll remove it unless some one can justify it's relevance. Uncool 1 17:44, 25 September 2005 (UTC)Reply[reply]

Last one detonated[edit]

See RAF_Scampton for a short bit on the last Grand Slam to be detonated after it was discovered that one loaded with torpex had been put on display as a gate guardian at the airbase.

The source for this story doesn't give a reference, and the paragraph in question begins "Apparently...", so I'm not sure how much credence should be given to it.VirtualDave (talk) 09:17, 20 October 2008 (UTC)Reply[reply]

Farge U-boat Pen[edit]

The Bombs did not hit that part of the Pen with the 7 m roof as the text seems du say. So the Grand Slams "only" penetrate 4,5 m of concrete (as the subtitle of the Pcture correctly sais)--WerWil 20:19, 31 August 2006 (UTC)Reply[reply]

Source? --PBS 18:36, 6 April 2007 (UTC)Reply[reply]

I know only german sites: [1][2] --WerWil 17:40, 7 April 2007 (UTC)Reply[reply]

30 meters or 40?[edit]

The development history section says both that the grand slam would detonate "some 30m" below the ground and "over 40m". What is the real fact here? I imagine it is a fuzzy range and dependant on the ground material but please...--Lomacar 18:57, 22 September 2006 (UTC)Reply[reply]

Vídeos with this bomb[edit]

These sites: and have this bomb.Both have sound in English.Agre22 (talk) 01:41, 28 August 2008 (UTC)agre22Reply[reply]


< After the Allied Operation Undergo[8] captured the Watten V-2 rocket facility in October 1944, a single Avro Lancaster attempted to bomb the bunker's dome from 10 November-20 November with a Grand Slam at precisely midday.[9] >

This is impossible to believe and should in my view be deleted. The first, trial, drop of a Grand Slam was not until 13th of March 1945. —Preceding unsigned comment added by (talk) 02:33, 18 October 2010 (UTC)Reply[reply]

Deleted. (talk) 22:56, 31 October 2010 (UTC)Reply[reply]

What does "live" mean?[edit]

The article says: "A live Grand Slam bomb was accidentally displayed as a gate guardian at RAF Scampton for over a decade before the mistake was realised. It was gingerly removed (by crane and low-loader) to the test range at Shoeburyness, where it was detonated.[25]"

I'm not sure what "live" means. Does this mean it contained a charge or was it also armed with detenators? (talk) 11:47, 12 March 2012 (UTC)Reply[reply]

It almost certainly means the former, i.e., containing explosive but un-fuzed. Non-'live' munitions usually are empty cases or contain an inert filling.
The arming pistols would have been inserted into the tail pockets upon bombing-up shortly before flight, so unless the bomb had been loaded onto an aircraft and the operation then subsequently cancelled, it is unlikely that the bomb had ever been fuzed. So it was probably 'safe-ish' while a gate guard.
Grand Slams were built in relatively small numbers and so it is likely that very few 'practice' examples (used for ballistics testing and for armourers' training) were made, at least before 1945. Hence the likelihood of the Scampton example being the 'genuine article'.
A bomb is said to be 'live' when it contains explosives but is un-fuzed. When fuzed and ready to go it is said to be 'armed' - that's why the detonators/fuzes are also sometimes called 'arming pistols', especially in the navy.
BTW, the term 'pistol' used for a detonator comes from the times when to scuttle a ship a barrel of gunpowder was stowed below decks and then detonated by a flintlock pistol fired by a long string tied to the trigger. — Preceding unsigned comment added by (talk) 14:50, 21 October 2012 (UTC)Reply[reply]
Is the Australian Armourers Association article reliable? See for a discussion. cmɢʟee୯ ͡° ̮د ͡° ੭ 18:52, 16 May 2013 (UTC)Reply[reply]

Medium Capacity?[edit]

Just curious - if this was the biggest bomb around, why was its official name 'Bomb, Medium Capacity'? Were there plans for something even bigger? (talk) 13:36, 1 February 2014 (UTC)Reply[reply]

Medium Capacity refers to the ratio of bomb case to explosive filling, not the absolute size of bomb . See Blockbuster bomb for British "High Capacity" bombs. this website has articles on the various bombs. GraemeLeggett (talk) 13:55, 1 February 2014 (UTC)Reply[reply]
I went ahead and incorporated this as a parenthetical footnote in the main body of the article (and also in the article on the Tallboy). (talk) 18:54, 14 March 2019 (UTC)Reply[reply]

The sentence: "Like the Tallboy, because of the low rate of production and consequent high value of each bomb, aircrews were told to land with their unused bombs on board rather than jettison them into the sea if a sortie was aborted" even though there is a source, is incorrect.

The undercarriage is only designed to take the stresses of landing a Lancaster 'dry' ie without its bomb load. Hence an unused Grand Slam bomb would have to be jettisoned before attempting a landing otherwise the landing gear would collapse with the additional weight of c10 metric tonnes of Grand Slam. 2A02:8420:4AAD:AE00:70DA:2812:19DB:AFF0 (talk) 10:14, 14 March 2015 (UTC)Reply[reply]

No. The Lancaster B.I Special had the undercarriage reinforced precisely so that it could land with the bomb still on board.Khamba Tendal (talk) 17:20, 25 August 2015 (UTC)Reply[reply]

Aircrew were told to land ..... etc[edit]

The sentence: "Like the Tallboy, because of the low rate of production and consequent high value of each bomb, aircrews were told to land with their unused bombs on board rather than jettison them into the sea if a sortie was aborted" even though there is a source, is incorrect.

The undercarriage is only designed to take the stresses of landing a Lancaster 'dry' ie without its bomb load. Hence an unused Grand Slam bomb would have to be jettisoned before attempting a landing otherwise the landing gear would collapse with the additional weight of c10 metric tonnes of Grand Slam. Boatman (talk) 10:21, 14 March 2015 (UTC)Reply[reply]

617 Squadron by Osprey disagrees. It's amazing what aircraft and crews can do if the motivation is there. GraemeLeggett (talk) 12:42, 14 March 2015 (UTC)Reply[reply]
Quite so. The stresses on landing need be no greater than those on take off, it depends on the skill of the pilot to be able to touch down gently enough and to allow the wings to gently unload the weight to the wheels. The stopping distance will also be greater, so a runway of adequate length is required. For a ham-fisted one the comment would otherwise be true.
If an undercarriage will support a weight on take-off, it will also support the same weight on landing, but many pilots will not be able to touch down gently enough for this to be advisable, perhaps due to lack of skill, weather, etc,. Hence recommended maximum landing weights. — Preceding unsigned comment added by (talk) 16:49, 18 April 2016 (UTC)Reply[reply]
No, safe take-off weight and safe landing weight are not the same, the downward velocity of the aircraft on landing imposing a greater load. And, as I noted above, the Lancaster B.I (Special) was specifically adapted to land with the Grand Slam on board if necessary, owing to the exceptionally high cost of the bomb.
Safe landing weight for the standard Lancaster was 55,000 lb. (Air Publication 2062A, Pilot's and Flight Engineer's Notes: Lancaster I, III & X, Air Ministry May 1944, p.29.) The aircraft had an empty weight of 31,242 lb and a tare weight with fixed military load of 35,831 lb. In 1945 it was rated for a maximum operational load (crew, fuel, oil, ammunition and bombload) of 36,169 lb, making for an all-up take-off weight of 72,000 lb. (Harry Holmes, Avro Lancaster, Airlife 2002, ISBN 1 84037 376 8, table p.79. The author spent his career with A.V.Roe & Co. and British Aerospace.)
I don't know the exact figures for the B.I (Special), but its empty weight and tare weight were reduced by several thousand pounds compared to the standard Lancaster because the front and mid-upper turrets, the outer wing tanks and the bomb doors were all deleted. The safe landing weight was increased by the fitment of the reinforced undercarriage. The standard B.I could land at almost 20,000 lb above tare weight; about 1,000 lb would be crew and most of the rest would be fuel and ammunition. The B.I (Special), being much lighter and fitted with a tougher undercarriage, would have a considerably larger margin, allowing it to land with a 22,000 lb Grand Slam as long as enough fuel had been burned off or jettisoned.
Crews of 617 Squadron did in fact land back with Grand Slams still aboard on a number of occasions. Notably, five crews brought their Grand Slams back to Woodhall Spa after the Nienburg raid of 22 March 1945. Twenty Lancasters launched, six with Grand Slams and fourteen with Tallboys, to destroy a rail bridge near Bremen, but the CO, Wg Cdr JE Fauquier DSO** DFC, ordered just four crews to attack -- with one Slam and three Tallboys -- while the rest circled in reserve. The Slam and two Tallboys scored direct hits, destroying the bridge, so all the other bombs were returned to store. (Paul Brickhill, The Dam Busters, Pan 1983, ISBN 0-330-37644-6, p.257; Jon Lake, Lancaster Squadrons 1944-45, Osprey 2002, ISBN 978 1 84176 433 7, p.60.) Khamba Tendal (talk) 17:48, 23 June 2019 (UTC)Reply[reply]

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CE, added references, citations, homogenised citation style. Auto edded and rm dupe wikilinks Keith-264 (talk) 22:03, 12 November 2019 (UTC)Reply[reply]

Added more detail but wonder if anyone has Flower, Stephen (2004). Barnes Wallis' Bombs: Tallboy, Dambuster & Grand Slam? Cooper gets a little vague about which hits were Slams and which were Tallboys. Regards Keith-264 (talk) 23:29, 19 November 2019 (UTC)Reply[reply]


It mentions the difference between GP and MC many times, word for word. — Preceding unsigned comment added by 2A02:2788:1008:2C3:E2CB:4EFF:FE88:1A2C (talk) 07:12, 27 January 2020 (UTC)Reply[reply]

Where? Keith-264 (talk) 19:55, 27 January 2020 (UTC)Reply[reply]

URL for citation[edit]

@Keith-264:Why did you remove URL to cited page? --Happyseeu (talk) 22:16, 8 July 2021 (UTC)Reply[reply]

No need since you gave the page number. Regards Keith-264 (talk) 22:20, 8 July 2021 (UTC)Reply[reply]
@Keith-264:Template:Sfn#Adding_a_URL_for_the_page_or_location says "If a specific link to the page or section is available, a URL can be added to the location or page number. " So there is nothing against including a page URL. --Happyseeu (talk) 00:06, 10 July 2021 (UTC)Reply[reply]
@Happyseeu: There's nothing for it either. They aren't included in the other sfns so it goes against the article style. Regards Keith-264 (talk) 09:19, 10 July 2021 (UTC)Reply[reply]

Recent edits[edit]

I have a new source which promises to resolve some of the citation and detail failings of the eisting article. More to follow tomorrow. Keith-264 (talk) 17:59, 16 January 2022 (UTC)Reply[reply]

More to mine from Flower 2013 on the bombings and revision to the lead to follow. Keith-264 (talk) 11:49, 19 January 2022 (UTC)Reply[reply]
Three more raids and the lead to complete. Keith-264 (talk) 10:33, 24 January 2022 (UTC)Reply[reply]

Hamburg, 9 April[edit]

I'm unconvinced that April 9th is indeed “Poets Day” in Germany, and reckon this ought to be referenced. In Britain “POETS Day” is an irreverent term for Friday, meaning “Piss Off Early, Tomorrow’s Saturday”; however April 9th 1945 was a Monday. Mr Larrington (talk) 22:47, 29 April 2022 (UTC)Reply[reply]

I didn't write that bit and would be happy to see it go. Thanks for repairing the typos Mr L. Regards Keith-264 (talk) 06:10, 30 April 2022 (UTC)Reply[reply]

"The most effective bomb" in lead[edit]

I don't think this should be said in the lead without defining to what standard effective refers to. Typically the effectiveness of a munition refers to its Circular error probability, which this sentence does not seem to make reference to. I think the sentence should be eliminated from the lead or context be given. Personnongratia (talk) 23:33, 7 November 2022 (UTC)Reply[reply]

The lead reflects the information in the article, it isn't the place to discuss niceties. Regards Keith-264 (talk) 04:47, 8 November 2022 (UTC)Reply[reply]
I wouldn't characterize this as a nicety. Does "most effective bomb" refer to explosive power, circular error probability, minimization of civilian casualties, or the total strategic effect of its use? All are plausible definitions... All I ask for is some reference to what "effective" refers to. Yes the lead should not contain specifics, but this is not an excuse to use ambiguous terminology in ways that can cause a reader to jump to an incorrect conclusion about this specific weapon. The "effectiveness" of a bomb has no standard definition and can be interpreted in multiple ways, so it is our duty to inform a reader about what we mean we use the term. Personnongratia (talk) 05:06, 10 November 2022 (UTC)Reply[reply]
What readers have jumped to wrong conclusions? Keith-264 (talk) 08:03, 10 November 2022 (UTC)Reply[reply]
Asking that question misrepresents what the OP said. I'm with the OP here. Yes, the claim of "most effective" is repeated later in the article, in the Analysis sub-section, but it's not explained or defined there either. There's a link to a source, but it's a book; not easy for most readers to access. One assumes the book makes that claim, but we still have no idea what it means. HiLo48 (talk) 08:45, 10 November 2022 (UTC)Reply[reply]

What would you prefer? Keith-264 (talk) 14:21, 10 November 2022 (UTC)Reply[reply]

That's where the difficult to access source becomes a problem. I don't know what it actually says. Guessing is dangerous. It would at least be better explicitly assigning the claim to the author rather than writing it as an absolute claim in Wikipedia's voice. HiLo48 (talk) 22:15, 10 November 2022 (UTC)Reply[reply]
I have the source so probably paraphrased that bit but it's an e-pub and I can't copy it; I'll have to transcribe it tomorrow so you can have a look. Regards Keith-264 (talk) 22:49, 10 November 2022 (UTC)Reply[reply]