Greg Boeser
2nd Lieutenant
Great Yarmouth: Huge blast after unplanned WW2 bomb detonation
Norfolk Police say the bomb detonated unplanned during an attempt to defuse it.
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Ka-Booom!
- Thread starter Greg Boeser
- Start date
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fubar57
General
Jaysus
yosimitesam
Airman 1st Class
Since the majority of German bombs used electrical fuses, could it even be possible that the capacitor in the fuse held a charge all these years? Or was this a delayed-action bomb that would have an anti-handling fuse and just never went off until now? You have to have an explosive train (fuse+booster) to set off these large bombs so I wonder what specific fuse it had.
Snautzer01
Honourably banned
- 42,964
- Mar 26, 2007
This is why you dont take ancient explosives to your home
https://www.nu.nl/298203/video/wo-ii-bom-in-engeland-ontploft-onverwachts-bij-ontmanteling.html
ww2aircraft.net
250 kg aircraft bomb.
I am not an expert on this and the EOD details are almost never disclosed. However, I believe the standard SC250 with DA did have a mechanical anti-defusing capability. The UK news was that they were going to use a saw to remove the filling, so I guess that they were worried about the Fuse. They also saw it as too dangerous to move the totally exposed bomb onto a barge and move it, even though it was right at the waterside. It is reported that the watercooling for the remote saw was washing away the blastproofing bund so, they stopped that and were trying to do a "controlled burn" instead. Then it went BNAG!
Eng
yosimitesam
Airman 1st Class
From what I've read, the Germans used some electrical fuzes/fuses because (1) they were cheaper due to not having precision machined mechanical parts and (2) they could change the fuzing from "instantaneous" for some targets and "delayed" for other targets, and could do this via switches in the cockpit. This would make them very good for tactical bombing wherein the pilot or commander could decide on the spot what would be more effective. They did use some mechanical fuzes, though, because I read that one method of handling unexploded bombs was to drill a small hole in the fuze then fill it with a liquid plastic material that hardened over a short period of time and "froze" all the components in the fuze in place (and this could be done remotely). Also, for most TNT based explosives, if you could safely create a hole in the bomb case you could then "steam" the explosive out of the bomb and render it safe. I wonder if one of the fuzes in this bomb was an "anti-tamper" fuze.
Info on German bomb electrical fuzes: LINK .
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Yes, a good link.
Some very hard-won info on those fuses, and some original detailed German documentation. In fact, I think that document is based on an original German guide. Makes me wonder what our Bomb Disposal guys were working with earlier in the war? In fact, if you know of the recovery of the magnetic mine, they only defused that because the fusing was not properly armed by the armourers.
I note that the DA fuzes (17, 17a, 17b) were clockwork with electric impact arming. They are the ones with the Zus 40 anti-handling. Lots of other nasty anti-handling on other fuses in the list. Out of interest, my Father was nearly hit by German bombing of Nottingham in May 1941, missed him by 20 yards. Next day, he and his mate went to look in a hole with a DA bomb up the road while the air raid warden was having a cuppa. He got chased off by the warden! That bomb exploded later that day, about 12 hours after bombing, so probably a type 17 fuze.
Eng
special ed
2nd Lieutenant
- 5,667
- May 13, 2018
As an aircrew member, I would be very apprehensive when switching from delayed action to instantaneous from the cockpit.
That really applies to modern systems where there are electronic arming delays. The delays in old fuses were purely for post-impact delay, either for penetration, or self protection at LL, or for enhanced denial with long/variable delay, or for EOD attrition with booby traps or anti-handling. AFAIK, those WW2 were pretty much fixed fusing when armed on the ground, the final safety-pin was a fixed arming wire. Some bombs had air spinners that had an arming function. However, mistakes can still happen, and have!
Eng
Ooops!
yosimitesam
Airman 1st Class
The delay/instant switch didn't charge the firing capacitor(s). Neither of the firing capacitors was charged until after the bomb was dropped. One of the two firing capacitors (delay/instant) charged up on the way down so that the bomb was several hundred feet (at least) below the aircraft before it was charged enough to fire the "squib" that started the detonation train. The cockpit switch just changed the circuit to one of the two firing capactitors that were charged on the way down. A "master" capacitor (as I understand it) was charged instantly (from the aircraft electrics) in the fraction of a second after the "bombs away" was thrown and this capacitor charged one of the firing capacitors (delay or instant) very slowly through large resistors, and only after a safety pin was removed by the drop. It took some time before there was enough charge in either firing capacitor to initiate the detonation train in the fuze. This prevented any premature in the aircraft, no matter what. One document I read stated that the Germans claimed (after the war) they had no prematures or any other troubles with the electrical fuzes, except for the occasional "dud". The electrical fuzes were a clever design and seemed to be as foolproof as mechanical fuzes. The info I read also stated they tested the fuzes (before the war) using high voltage testing equipment and they were considered safe from any accidental "spark" from static or lightning, etc. BTW, the 'delayed' function only delayed the detonation by a fraction of a second, e.g. .05s or 0.1s or something on this order.
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