Falkland Islands, Artillery & Thermite

Hello, I am new here and I attempted to find this information via google, yahoo, snopes, and other search engines before searching through the archives here. I hope that someone can help me.

Basically, in my undergrad days, my classical mechanics professor told a story to my class explaining the results of the Coriolis effect by stating that during the battle for the Falkland Islands in the 80’s, the British neglected to correct for the effects of being beneath the equator. Hence when they would dial their heavy artillery, they found that their shells would fly in a different direction than expected, thus missing their intended targets.

Furthermore, when I spoke of this to a co-worker in my lab, he recounted a tale from the Falklands that his chemistry professor related to him. Apparently, he was told that the British had intended to make faster, lighter ships by making them of an alloy of aluminum and iron. Unfortunately, when the iron oxidated, it reacted with the aluminum to produce thermite. When these ships were hit, attempts to put out fires with water resulted in a greater explosion!

I am curious, are either of these stories based upon fact? I know that the physics is correct for the first possibility, but I am unfamiliar with the chemistry for the second. Furthermore, I do not know whether the events (or something like them) ever occured or whether they were simply anecdotes related to aid the teaching of college students. Please help me if you can.

Thank you. :slight_smile:

The second one is basically true. The * Sheffield * was hit by a single Exocet missile and the resulting fire was exacerbated by the aluminum armor.

Well, a bit more research indicates that the second one is widely believed to be true, but there’re some conflicting opinions. It’s possible that the aluminum superstructure just melted rather than burnt and that the fire was due to a combination of rocket fuel from the missile and other flammable materials on the Sheffield. In any event, aluminum turns out to be a fairly risky material to construct fighting ships with.

This claims this is a myth… However what is interesting is it talks about **World War One ** naval battle that occurred near the falklands NOT the 1982 conflict:


The fact it was originally talked about in one context and is now discussed in another seems very typical of an urban legend to me (like those anti-clinton stories that are now anit-bush stories).

The first one may be true, I can’t find any specifics. But, it IS true that long-range artillery is affected to some extent by the Coriolis force, and corrections may need to be made, depending on the direction of the shot, the range and the latitude. The farther from the Equator, the greater the effect. Right at the Equator, the Coriolis force is zero, and is at a maximum at the the poles.

Forgot to mention that the Coriolis force does act in opposite directions in one hemisphere than it does in the other. This is why Northern Hemisphere cyclonic storms rotate counterclockwise and Southern Hemisphere ones rotate clockwise.

Well aluminum burns on its own but I don’t think it’s specifically because of it’s combination with iron.

It’s not metallic iron that’s the problem. Aluminum reacts with iron oxide in what’s called an aluminothermic reaction; the iron oxide acts as an oxidizer in a reaction that releases so much heat that one of the byproducts is molten iron. This is called thermite. Among other purposes, it finds use in welding applications and cutting through materials like concrete.

I would be very surprised about the inacurracy of the 4.5" guns, since we were hitting our targets in three rounds or less.

HMS Ardent took out an Argentine supply vessel in Falklands sound in only a few rounds.

One Exocet was taken down by a 4.5" shell.

Those guns were extremely accurate, far more so than the Army field pieces, but given the systems behind the Navy guns, this sould not be too surprising.

As for the ally superstructure, we had loads of other problems long before the Falklands war.

One big problem is that is does not flex like a steel hulled vessel, the older Rothsay and Leander frigates were superb sea keeping ships, part of that was the way the bows were built, the profile of them, and one other part is that they were designed to flex just aft of the bows and just in front of the forward superstructure.

The ally ships, largely built by Yarrows, did not have the same flexing point built in, and the high superstruture, relative to the older leanders actually made them less flexible.
The only way they could be built so tall was to reduce the suprestructure weight, this was done using alluminium.

Trouble with this is that the sea found its own ways to force the type 21 frigates and the type 42 destroyers to flex (the type 42 were a bit more flexible and so din’t suffer as much - especially the llater lengthened ones)

The result was that although the Yarrow built ally superstruture ships looked nice, they had the unfortunate habit of work hardening, and carcking the superstructure about two thirds along it. It meant that they had to weld large girders across the cracks, but that tended to just move the cracking problem elsewhere.

This used to cause me endless problems, as the telephone exchange room where I did most of my work from used to get the benefit of sea water leaking in, not really all that good for the equipment in there.

When HMS Ardent(type 21 frigate) was destroyed, the thing that did for her was the fire in the helo hanger.
Helo fuel burns hot and the fire crew couldn’t get the blaze under control, if they had been able to do this, she would have probably retained a significant part of her fighting ability.

When she went down, the crew was evacuated to other ships, so word got around about what ocurred.

The fire could not be brought under control because of the superstructure in that area, though it has to be also said that she was hit again and again, and its a testament to the modern methods of design and construction that she remained afloat having taken so many hits.

I’m not sure that the ally superstructure was the main culprit, it played a part, but you have to also consider that running from stem to stern, there are miles of cabling with copper conductors, and these will melt at a lower temperature than ally does, and this would make life hard for any firefighter.

The main problem, certainly in the case of HMS Sheffield, was the loss of firemain pressure when it was breached.
Protocol demands that when sailing in a hot zone, the firemain is isolated into sections, with three out of the four fire pumps running and the main divided into 3 sections.
At the time of the Exocet strikes, Sheffield was cruising with just one pump running, to for a while the only way to fight the fire was with handheld appliances.
The time lost getting the other pumps running and isolating the damaged section of firemain pipework may well have been critical to the loss of the ship.
Its noteworthy that her skipper Capt Salt didn’t recieve a campaign medal when all the other CO’s did. This might have been rectified since, but I do remember it being commented upon when the original Falklands medal was handed out.

If my calculations are correct, for a 10 mile artillery shot the Coriolis Effect would result in an difference of between 5 and 6 feet in where the shell hit between northern and southern hemispheres… That’s about .11 milliradians.

This site gives thetypical dispersion of artillery as about .158 mils. I don’t know whether that is milliradians or gunnery mils. If it is milliradians then not taking account of Coriolis would almost double the error (about 5 or 6 ft.) expected from dispersion. If the dispersion is in gunnery mils, which are 1/1000 of a circle, then the Coriolis error would be insignificant. My WAG is that the quoted dispersion number is gunnery mils giving a probable dispersion error of about 30 ft. on a 10 mile shot.

Somewhere in my calculations I dropped a factor of 10. Coriolis effect would be about 10 times the dispersion if the dispersion is quoted in milliradians and about 1.5 times if the dispersion is in gunnery mils.

For land artillery the sighting shots could have been well off, but forward observers would rapidly bring them on target. For naval action, the British have had considerable experience in the sourthern hemisphere and I expect they have firing tables for both areas.

Thank you one and all. :slight_smile: