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Falklands - Bomb Fusing

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Falklands - Bomb Fusing

Old 26th Oct 2020, 10:05
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Falklands - Bomb Fusing

We all know about the early Argentine bomb failures attributed to excessive fusing delays, delays which undoubtedly saved a number of RN ships from destruction, but were the timing specifics ever revealed. What fusing delay did they start with and what did they finally reduce it to ?

If youíre coming in at 400 knots and 60ft and release at 300 yards youíre playing with what, 2 seconds ?

Anyone have the full story.
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Old 26th Oct 2020, 13:16
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The fusing 'delays' were not excessive per se and the Argentinians were well-aware that they were dropping ordinance outside of the normal self-frag avoidance criteria. Indeed, from the outset they set the fusing at quite an aggressive arming profile. They were technically proficient, they knew the attack profiles being used and the pilots themselves displayed an incredible amount of skill and accuracy during weapon delivery. Hitting a stationary vessel with a good CCIP + height-sensor with a dumb bomb is not a given during academic range work. Doing it against a ship underway, under fire, from a dynamic profile with visual aiming only is just incredible.

Bomb fusing is not just timing either. My knowledge of their fuses used has faded with time but in essence there was either a mechanic or a combined electro-mechanical fuse arming wire / wires. At weapon release these are pulled from the fuse arming vane as the other end is attached / connected to the aircraft pylon. Airflow is then free to drive the arming vane and the constant-arming governor until the preselected arming delay elapses (I think they had 2 to 18 seconds available). Only then is the arming train in mechanical alignment and able to function. At impact (as they only had impact fusing) there is then an additional delay set for correct weapon effect (impact, relay, detonator, lead, booster then main explosive charge).

Even without the folklore of the 'BBC commentary' the Argentinians had wound the arming delay back to minimum (2 seconds?) and way below the safe level given in the tables and even shortened the arming wire routing, to bring the weapon arming process uncomfortably close to the aircraft. The failing to arm or failing to fuse was primarily due to 2 factors caused by the out-of-envelope delivery profile. First was a known phenomenon of weapon instability in pitch when ejected from the pylon, causing brief arming vane stalls, which is not usually a factor during normal deliveries. The second was from the nose fuse collar shearing due to either impact grazing angle or surface skip. The collar shear was another safety feature designed to reduce the chances of unintended detonation should the weapon be dropped during loading etc but it also worked against them.

It's best to think of the Argentinean efforts as a technically proficient operator pushing the weapons to the very edge or even beyond their capabilities. As an example of their skills and knowledge the mechanical re-gearing of fuses to allow for slow-speed arming when delivered from Hercules wing pylons will give you an idea of what they could do, even in a hurry.

I think the folklore is just too strong to be overtaken by reality though and it is simpler to state or imply that they didn't know what they were doing. But they did.
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Old 26th Oct 2020, 13:53
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Originally Posted by Fonsini View Post
We all know about the early Argentine bomb failures attributed to excessive fusing delays, delays which undoubtedly saved a number of RN ships from destruction, but were the timing specifics ever revealed. What fusing delay did they start with and what did they finally reduce it to ?

If you’re coming in at 400 knots and 60ft and release at 300 yards you’re playing with what, 2 seconds ?

Anyone have the full story.
I cannot quote the precise settings used by the Argentine aircraft but in general terms the weapons used had a safety delay after release, before the fuses could arm. This was to allow safe separation between the aircraft and the weapon and was usually achieved by a mechanical vane rotating in the airflow. For "slick" bombs, delivered in a high-angle dive or climbing (loft or toss) manoeuvre, we used a long delay (in excess of 10 secs) to allow the aircraft to achieve separation by manoeuvre. For a low-level delivery this was not feasible and a very much shorter safety delay was used, combined with a retardation device on the weapon, to achieve safe separation. Depending on the weapon, this could be a set of drag-plates or a parachute.

Once armed, the weapon was fused to give a delay to detonation of between a few milliseconds and 30 minutes, once it had hit its target. If you were attacking a ship, the delay would be quite small so that the bomb exploded inside the target, if you were aiming to penetrate a runway, the delay was longer.

Mog

Sorry, crossed with Just this Once, who has provided a much more eloquent answer!

Last edited by Mogwi; 26th Oct 2020 at 13:58. Reason: Crossed with Just this Once
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Old 26th Oct 2020, 16:27
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Salute!
Good poop from Just this once

I dropped many Mk-81 and Mk-82 slicks in SEA with the 904 nose fuze and you can see more here, plus the delay element that Mog talks about.

https://bulletpicker.com/nose_-impac...-m904e2_-.html
https://bulletpicker.com/delay-element_-m9.html

We also had tail fuzes that had a few millisecond delay element, and our nose fuze usually had an "instant" delay element. Normal arming was 4 seconds for slicks and 2 seconds for the snake eye high drag versions. Later in life, USAF got nervous and increased the standard arming delay time to 6 seconds.

My closest call in two combat tours was dropping a MK-82 along with a nape can I had selected without de-selecting the MK-82. FAC asked for the nape to hit a group he finally spotted running down a dike, and I was already setup for the slick. "O.K.", Gums says, "ya got it". Dropped down, rolled in and had a good drop with the nape down in the weeds. When going back to the slicks, the station switch was already selected. Sure enuf, I looked out on the wing and the bomb was gone. The 4 second delay had saved me, as it had not had time to arm. I would have been blown outta the sky with a 500 pounder going off a hundred feet below me ( 200 ft release in shallow dive, then 4 gees pull up).

Some units did not allow mixed loads, but the Huns and we slower A-1 and A-37 folks almost always carried mixed loads due to the missions, weather and terrain considerations. e.g. 2 x MK-82 slicks, 2 x big napes and 2 by Mk-81 or rocket pods or CBU. [Never ] Only carried mixed loads in the SLUF on second tour when flying Sandy or Hobo missions, and finally had chance to carry the huge MK-84 2,000 pounder on several missions.

Gums sends...

Last edited by gums; 26th Oct 2020 at 17:53. Reason: correction of loadouts
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Old 26th Oct 2020, 17:00
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I do enjoy your posts, gums!

They remind me of something I once read from a pilot who'd been flying in Viet Nam and was getting frustrated with inactivity:
"There I was, laden with Snake and Nape and the goddam grunts couldn't find me no commies to kill!".

Ae all those USAF magazines still published? Some were good, but those featuring the missile silo crews were perhaps less so....
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Old 27th Oct 2020, 09:52
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gums,
like BEagle I too enjoy your posts. Keep them coming.
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Old 27th Oct 2020, 11:50
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Gums, great post as ever. Mogwi, thanks for adding your own personal delay to the bomb fusing process.

JTO, I have waited nearly 40 years to finally have that explanation - to this day most people believe that the Argentinians forgot to reduce the arming delay on their bombs. Great technical explanation, thank you.
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Old 27th Oct 2020, 13:54
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I read somewhere that on the 25th May they had changed the type of nose unit and were particularly disappointed that the bomb that hit Broadsword didn't cause severe damage. They believed it didn't strike anything substantial enough to trigger it before it bounced off. I have no evidence to hand but the fuse change might be why the bombs that hit Coventry were so effective.

The RE bomb disposal team member killed on Antelope was Staff Sergeant James Prescott of 49 EOD Squadron who was awarded a posthumous CGM. His colleague WO II John Philips lost an arm and was awarded the DSC which was believed to be unique on two counts, first to a non-commissioned rank and possibly the first to a soldier. He was later commissioned.

Some of the bombs were definitely British the one defused on Antrim was clearly marked Made in Derby.

On the subject of the Fleet Clearance Diving Teams, about twenty years after the war I had the privilege of having a drink with the late Lt Cdr Brian Dutton, who commanded FCDT 1. He was, as one might expect, very modest about his bravery, I learnt recently that he was recalled, to go South, from terminal leave prior to retirement.

(This may seem a bit odd as I was referencing a now deleted post)

Last edited by SLXOwft; 27th Oct 2020 at 14:14. Reason: JTO's deleted post.
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Old 27th Oct 2020, 17:33
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One good reason for the SHAR using a long safety fusing on slick bombs was the fact that VT fuses (radio altimeter) could sometimes "ladder" on the one ahead, causing them to go bang in turn back towards the aircraft. OO-ERR!!

😳
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Old 27th Oct 2020, 18:28
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In light of the above and the dangers and shear bad luck, is this how Gordy Batt was taken on the 23rd May 82?. I’ve heard enthusiasts suggest it but from the people that were there.........
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Old 27th Oct 2020, 19:39
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No - but my reply has to have at least 10 characters, so - No.
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Old 27th Oct 2020, 22:35
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Originally Posted by Just This Once... View Post
Sorry, I decided my post on the FCDT / RAF BD / RE BD didn't do enough justice for the incredible work done by those brave souls. The perils of posting from a phone with a failing memory.
Indeed. An RE Operator was awarded a rare CGM (posthumously) and his colleague the DSC for their attempts to make safe a 1000lb bomb on HMS Antelope. An RAF operator was awarded the QGM for his several BD actions during the campaign; in particular the incident at the Ajax Bay Commando Logistics Hospital. Two colleagues were Mentioned in Dispatches.
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Old 28th Oct 2020, 01:53
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Indeed. An RE Operator was awarded a rare CGM (posthumously) and his colleague the DSC for their attempts to make safe a 1000lb bomb on HMS Antelope.
As already mentioned by SLXOwft the colleague was Warrant Officer J.H.Phillips, RE. I met him one day in my militaria shop in Falmouth where he came in to browse through my stock of medals When he told me he had the DSC I was disinclined to believe that an army warrant officer would receive what is essentially an RN officer's award, (you get a lot of Walts in militaria shops) but on hearing the whole story I altered my opinion, especially when he described how he had been seriously injured when the bomb explosion blew a steel door off its hinges. It was only at that point that I noticed that the sleeve of the man I was talking to to was empty.

WO Phillips medals were sold at auction in 2011 and achieved a hammer price of £120,000.
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Old 28th Oct 2020, 02:30
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Rockets (2 in, 68mm or SNEB) I would have thought would have been far more effective (than bombs that didn't explode)

Could have been fired at extreme range to reduce vulnerability to the ship's air defences.

Unlikely to sink anything - but only takes a few hits to the destroyers or a frigates superstructure and it's most likely out of the battle (maybe temporarily) or at least degraded.



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Old 28th Oct 2020, 13:38
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Originally Posted by typerated View Post
Rockets (2 in, 68mm or SNEB) I would have thought would have been far more effective (than bombs that didn't explode)

Could have been fired at extreme range to reduce vulnerability to the ship's air defences.

Unlikely to sink anything - but only takes a few hits to the destroyers or a frigates superstructure and it's most likely out of the battle (maybe temporarily) or at least degraded.
There seems to be little general knowledge of how many ships actually were "most likely out of the battle (maybe temporarily) or at least degraded" by hits from UXBs. In my view, in addition to the bravery of the bomb disposal teams from all services, without the repair efforts of those onboard MSV Stena Seaspread the outcome could have been an even closer run thing than it was.
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Old 28th Oct 2020, 15:36
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Salute!

While I like the idea of using RX for boats, their accuracy is highly dependent upon release parameters like gee and AoA of the attack jet.

That being said, my #2 sunk a Cambodian PT boat with RX during the Mayaguez incident of 1975. Our SLUF's had the computed inpact mode for the 2.75" RX with an "in-range" cue at 8,000 feet. As Sandies, we used the RX for both marking tgts and the other pod loaded with HEAP wrhds. His RX went thru the PT boat and blew out the bottom! By the time he could look back the water was already flooding the boat.

The problem is that you had to be very "gentle" to get the advertised acuracy. The slightest gee would result in a piss poor shot. Also, a low AoA was desireable so the RX would be aligned with the airflow. The CRV-7 that came about in the 70's was far superior to what I used from 1968 - 1975. Nevertheless, it still had the same launch requirements to get the advertised dispersion.

Using a decent impact fuze with slight delay, RX would be good for small boats if you survived the pass. Being "gentle" for launch is not good for your survival. Bombs are 100% ballistic and your CCIP or DTOS mode doesn't need "gentle" gee or low AoA to get great bombs. Those modes use your "instantaneous" flight path ( which is same as bomb you are carrying, heh heh) so the only correction is for time that the release mechanism needs. The DTOS mode of the SLUF would have been a killer for the Argies using their pig iron with good fuzes - point, designate and follow steering for a brief time with pickle button depressed.

Gums opines...

Last edited by gums; 29th Oct 2020 at 01:16.
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Old 28th Oct 2020, 17:52
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Originally Posted by NIREP reader View Post
In light of the above and the dangers and shear bad luck, is this how Gordy Batt was taken on the 23rd May 82?. Iíve heard enthusiasts suggest it but from the people that were there.........

I agree with EFJ, the VT fuses could not have operated until post the 11-Sec safety delay, even if they had been dropped live. In fact, GB had only been airborne for seconds and was still at low-level, close to the ship, when it happened.

Sad

Mog
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