Most of the "High Capacity" bombs had slightly domed front ends and flat sheet steel back ends with flat sheet steel rolled to form a cylinder. These bombs did not make any significant fragments and thus their only effect was "Blast" against soft targets. Their bombing accuracy was abysmal, even from the low altitudes they were mostly used. CEP = 1/2 mile from 10,000'! The higher they went, the more exaggerated the dispersion, IE almost one mile from 15,000'!
The tallboy/grand slam streamlined bombs had good aerodynamic properties, but the Lancaster's dropping latches/mechanisms were very un-reliable, and the scatter was huge!
Define "very un-reliable"?
Tallboy & Grand Slam were supported in the bomb-bay by a ML sling made up of a series of interconnected links. The top ends were fixed to the bomb bay roof. The other ends came together in a heavy duty electro-magnetic release unit under the bomb. There were some late releases reported and this unit was investigated but no specific faults were found. It can't have been too much of a problem or it would have been pursued further or changed. There was a manual release cable that ran alongside the electric release wiring.
Incidentally, the USAAF adopted that equipment for dropping the atomic bombs from the B-29s
As for "scatter was huge!", you are aware that the 617 squadron did not approach a target singly, line up and drop their bombs? Their approach to the target was in a "gaggle formation". So the aircraft were spaced laterally, longitudinally & vertically to minimise collisions while allowing them to cross the target in the shortest space of time. In some cases that could be in the order of 1 minute. So some spacing of the bombs was inevitable. 9 squadron adopted a line astern attack for some of its missions otherwise it also used the gaggle formation.
The two squadrons were also using different bomb sights. 617 used SABS while 9 used the Mk.XIV. And there was rivalry between the squadrons as to which wwas the more accurate!
But these bomb weren't designed to cause their effect by a direct hit. A near miss was intended to be adequate by exploding underground and creating a "camouflet", a large hole that would undermine the foundations of the target. One of the best examples of this were the Wizernes V2 launch site where the concrete dome of the site was not hit, but near misses destroyed the foundations in front of it. Another was the Bielefield Viaduct where some of the arches of the viaduct collapsed into the Grand Slam crater.
en.wikipedia.org
In actual use however it came to be used to penetrate large concrete structures like U boat pens etc and armoured targets like warships.
Both long and short and side to side! Look at the map of bomb impacts from the Tirpitz raids! One hit and two near misses, IIRC, out of over thirty drops??? Some 1-1/2 miles away from the target from 17-19,000'???
The experience from WW2 was that using a level bomber, 4 engined or not, to attempt to hit a ship, stationary or not, and regardless of the size of bomb used, was not as easy as you might think. Near misses, especially from large weapons as Tallboy, could add significantly to the damage caused.
Firstly lets look at the Tirpitz dimensions. Length overall 823 feet. Beam 118 feet. Then consider how high you would be dropping from. 14-18,000 feet. It only takes very slight distractions from weather, smoke, AA fire to cause a miss.
There were 3 Tallboy raids against the Tirpitz.
Operation Paravane 15 September 1944 from bases in USSR. 21 of the 27 aircraft carried Tallboys but only 15 were dropped and another was a hangup that after 3 runs dropped 4 miles away. There were to be 4 waves of 5 Tallboy carriers with each wave flying as a gaggle on slightly converging courses, and
aiming to put their bombs into a 750 yard square box with Tirpitz at the centre. The attack was along the length of the Tirpitz. Bombing was from 14-18,000ft. The target was gradually covered in smoke meaning that 3 aircraft followed orders and, not being able to see the target, took their bombs home. The rest were bombing into the smoke using mastheads & gun flashes for aiming points. The flak from ships and shore was described as intense but mostly burst below the bombers, but still some aircraft suffered damage. As a result the bombing was not very accurate and only a single hit on the bow and several near misses were achieved.
However the damage finished Tirpitz as a fighting vessel. As a result she was moved to a position near Tromso, which was within range of bases in Britain if the Lancasters were modified to maximise their range, to act a floating gun battery. Unfortunately all the defences she had in Kaa Fjord (smoke generators, flak batteries) were not moved with her.
Operation Obviate 29 Oct 1944. 20 aircraft from 9 Sdn & 19 from 617 Sqn. Each squadron was to compress its attack into a one minute time window spaced 5 minutes apart. Bombing heights were supposed to be between 13-16,000ft. Unfortunately the weather changed just as the raid went in, bringing with it a changed wind direction and cloud to interfere with sighting the target. Again bombs had to be aimed at gun flashes. 6 took their bombs home in accordance with orders.
Operation Catechism on 12 November 1944. 31 aircraft + a film unit Lancaster were dispatched. 2 did not bomb. Clear weather encountered for the first time. Attack altitude was c16,000 feet. 617 Sqn bombing was descibed as "very concentrated". That of 9 Sqn who were following was affected by smoke from the hits already obtained and the last few fell well away from the target. The attack lasted 3 minutes.
Just by way of comparison, on 28th July 1945, 11 B-24 flying from Okinawa attacked the Japanese carrier Amagi from high altitude. She was moored close to shore near the Kure IJN base. This is what her TROM from the Nihon Kaigun site has to say:-
"- 1200 Eleven B-24s carry out level bombing of AMAGI and KATSURAGI from high altitude. Though none strike directly near-misses land close alongside to port, detonating below the waterline, whose fragments riddled the port shell in places."
Katsuragi was undamaged by this attack.
Late in the war, we rigged a couple of B-29s to carry two Tallboys on inboard wing pylons, or one Grand slam/T12? Cloud maker with cut away bomb bay doors. Bombing accuracy Varied from less than 100' or so to over 500' CEP from 20-30K'. After the war, we installed racks for all three types of bombs in the B-36 and dropped two T-12?s from 30K' and 40K' or three to four Grand slams, or Tall boys per mission. Minimum bombing altitude was over 30K' and maximum was over 45K' for the last Tall boy! Accuracy ranged from under 100' to under 600' CEP!
The first USAAF Tallboy tests were authorised in Feb 1945 at which point a single aircraft 42-63577 was being modified by Bell to carry a single Tallboy in a modified bomb bay with cut-away doors. By the time the final report was produced on 15 June 1945 it was noted that the AAF Proving Ground was testing an aircraft modified to carry both Tallboy & Grand Slam. "
should this new installation prove to be functionally reliable, it is believed that this installation would be more desirable than the B-29 modified to carry only the 12,000lb Tall Boy bomb". 3xB-29A modified to carry a single Tallboy or Grand Slam (45-21747, 45-21750, 45-21751) were sent to Britain in March 1946 to participate in Projects Ruby and Harken.
T10 & T14 were the US designations for Tallboy & Grand Slam respectively. The T12 Cloudmaker was a 43,600lb weapon meant to be dropped by the B-36.
The underwing bomb racks for the B-29 were, AIUI, developed by Boeing to carry 4x4,000lb each but were also capable of carrying a Grand Slam. The photos of a test B-29 carrying two Grand Slams dates to the post war period appear on the internet quite frequently. What is unknown is what weight of fuel was being carried by this test aircraft.
Starting in Feb 1945 the VB-13 Tarzn was developed (basically a Tallboy with an aerodynamic shroud, a new tail section and radio guidance in both range & azimuth). Again a single weapon was carried in the modified bomb bay of the B-29 carrier aircraft. The 19th BG began operations in Korea between Dec 1950 & March 1951 with at least 3 B-29 Tarzon carriers. Of the first 10 drops only 1 hit was achieved and it didn't seem to get any better, hence its early withdrawal from service.
So the question really is with these big bombs, are they inaccurate weapons in themselves or are there a multitude of factors related to dropping such weapons from high altitudes that make them next to useless if the objective is to hit a very small target?
