The British army used heavy artillery to kill thousands of Londoners in the early 1940s

[wm]

Jack Allen, who was working on the proximity fuze et the Cavendish Laboratories, said at the time that half the fuzes currently used in British artillery were defective end caused shells to explode only when they landed. 

He claimed that these shells might be killing as many Londoners as German bombs.

If this was true, what would it mean in practice?
A total of 60,595 civilians were killed in the United Kingdom over the course of the Second World war by enemy action. Of this total, we can at once remove 8,042. These are the people killed by V Is and V 2s. As we know, the AA guns which shot down these weapons were usually operating outside cities and so there are likely to be few, if any instances of friendly fire among them.
This leaves us with a total of 52,553 who were killed during air raids or other enemy action.
If as many civilians really were being killed by anti-aircraft shells as were being killed by German bombs, that would mean that British artillery accounted for over 26,000 civilian deaths in Britain between 1939 and 1944.
Secret Casualties of World War Two: Uncovering the Civilian Deaths from Friendly Fire by Simon Webb

[PunctuationHorror]

Let's do some math:

Assume there were 1000 air raids and 10,000 AA grenades were fired on each raid.
Results in a total of 10,000,000 fired AA grenades.
A dud rate of .01 gives 100,000 duds; a rate of 0.1 gives 10,000 duds.
Kill rate of .01 per dud yields 1,000 and 10,000 deaths respectively.

So, 'thousands killed by AA FF' sounds plausible.

Now, let's fill in the real data...

[Richard Anderson]

Most of the 68 killed and 35 wounded were the result of anti-aircraft shells which detonated on hitting the ground.

There were 49 civilians killed and 35 wounded on Oahu. Of those, 32 dead and 12 wounded were in Honolulu. Errant shells accounted for 12, 4, and 3 in just three instances. I suspect the primary culprit were the 150 rounds of 5"/51 fired. However, a total of at least 6,143 3" to 5" rounds were fired and given the then expected failure rate of 5 to 10 percent in the standard Mk 18 time fuze, as many as 614 may not have exploded on time.

Of course, I doubt the standard of manufacture for British time fuzes was much different, so the notion that 50 percent of those failed is probably horse pucky.

[Knouterer]

There has never been any dispute about the fact that more British civilians were killed by the artillery than German aircrew. The estimates range from perhaps 10 percent to as many as 50 percent of the deaths on the ground during air raids being the result of British forces, rather than the Germans.

This latter figure was one favored by the men working frantically on the development of the proximity fuze, which would ensure that a shell exploded only when it was near enough to an aeroplane to cause serious damage to it. A scientist working on this idea at the Cavendish Laboratories calculated that half the time-fuzes used in anti-aircraft shells were defective and that as a result, they might be killing at least as many people during an air raid as were dying from the German bombs.

That doesn't make much sense either. Proximity or "VT" fuses would only function if the shell passed (very) close to an aircraft, which in the large majority of cases would not happen, so a time fuse (or self-destruct fuse) would still be needed to prevent the unexploded shell falling back to earth.
That would not be a concern at sea, which is why such fuses were mostly used in AA shells fired by USN and RN ships. It was also not a concern when such shells were fired by the guns of the "Diver Belt" in 1944, which tried to shoot down V1 flying bombs over the sea.
In any case, it seems highly unlikely that AA Command all through the war would fail to notice that half its time fuses were defective. In fact the fuses were continually improved and replaced by new models. And anyway, how would "a scientist" calculate the failure rate? What data did he have? From whom?

As to the notion that "as many as 50%" of casualties were caused by AA shells and fragments: that may have happened on specific occasions when a lone raider dropped a few bombs and a couple dozen HAA guns started blasting away, but it's certainly not true for the war as a whole.

I haven't read the book, and I'm not going to, but it seems to contain a whole lot of muddled thinking and hopeless confusion.

[Knouterer]

"There has never been any dispute about the fact that more British civilians were killed by the artillery than German aircrew. The estimates range from perhaps 10 percent to as many as 50 percent of the deaths on the ground during air raids being the result of British forces, rather than the Germans."

How does this even get published? It refutes itself within the space of a sentence - states that there is no dispute that more civilians were killed by British artillery than the Germans but then gives a starting figure of 10% which would mean 90% were killed by the Germans (and 20%:80%, 30%:70% and so on).

The quoted paragraph confuses or conflates two things. It is clear that the AA guns brought down relatively few German bombers and killed relatively few German airmen. Maybe three hundred in the BoB period, with about as many baling out and being taken prisoner (the numbers brought down by RAF fighters were much higher of course). It has in fact been argued that the purpose of the guns was not so much to bring down bombers, but rather to force them to take evasive action and fly higher, making accurate bombing impossible. It is therefore possible, if the truth were known, that shells and fragments falling down to earth caused a comparable number of civilian casualties.

But how many civilians were killed by German bombs, and how many by said shells and fragments, is an entirely different question.
As I wrote before, muddled thinking.

Let's assume, for the sake of argument, that the AA guns killed 1,000 German aircrew and 1,200 British civilians in the course of the war. The statement that "more British civilians were killed by the artillery than German aircrew" would thus be correct.
But that would be only 2% of the 60,000 civilians killed in air raids. Still tragic, but most people at the time would consider it acceptable, under the circumstances. The blackout too directly caused very many fatal accidents.

I would also assume that a good part of the casualties were men who knew the risks of being outside when guns were firing, but accepted them as part of their duties: air raid wardens, firemen, policemen, etc.

[Aber]

"There has never been any dispute about the fact that more British civilians were killed by the artillery than German aircrew. The estimates range from perhaps 10 percent to as many as 50 percent of the deaths on the ground during air raids being the result of British forces, rather than the Germans."

How does this even get published? It refutes itself within the space of a sentence - states that there is no dispute that more civilians were killed by British artillery than the Germans but then gives a starting figure of 10% which would mean 90% were killed by the Germans (and 20%:80%, 30%:70% and so on).

I think you may have misread this. The comparison is probably:
Civilians killed by AAA vs German aircrew killed by AAA

[hucks216]

"There has never been any dispute about the fact that more British civilians were killed by the artillery than German aircrew. The estimates range from perhaps 10 percent to as many as 50 percent of the deaths on the ground during air raids being the result of British forces, rather than the Germans."

How does this even get published? It refutes itself within the space of a sentence - states that there is no dispute that more civilians were killed by British artillery than the Germans but then gives a starting figure of 10% which would mean 90% were killed by the Germans (and 20%:80%, 30%:70% and so on).

I think you may have misread this. The comparison is probably:
Civilians killed by AAA vs German aircrew killed by AAA

Now you point it out, I see what you mean.

[wm]

Jack Allen (who said at the time that half the fuzes currently used in British artillery were defective) was a physicist, one of those who discovered the superfluidity of liquid helium.
And:

One of Jack’s contributions to the war effort was a new accelerometer to measure artillery shells’ typical accelerations of 150,000g within gun barrels.
...
He and his student Pat Willmore established that shells often suffer transverse acceleration (so-called side-slap) of 50,000g or more, which was ample to shear the pivots off the gears of a conventional clockwork fuse.
It explained the unreliability of ordinary fuses and paved the way for Merle Tuve’s radar proximity fuse.

[Richard Anderson]

So it took a physicist designing a new accelerometer to alert engineers testing fuzes on proving ground ranges that their fuzes were not going BANG? Good to know.

In reality, fuzes were tested regularly for functionality and reliability. For example, APG Firing Record No. 6693 tested powder-train time fuzes fired from the 3" AA Gun M1917. In 33 rounds fired there were two failures (94%) and time variability averaged about 0.79 seconds from the setting. The major reason for the development of the VT fuze was the lack of timing precision in mechanical and powder-train time fuzes rather than because they did not explode.

[wm]

I suppose the story was the clockwork fuses were unreliable, they asked him for help, and he was able to find out why.

[Richard Anderson]

I suppose the story was the clockwork fuses were unreliable, they asked him for help, and he was able to find out why.

Sure, but the idea they did not explode half the time is utter nonsense. They were unreliable in two ways. They failed to explode at all between 5 and 10 percent of the time. Or they failed to explode on time by between 0.5 and 1.5 seconds. If they failed to explode they can't kill civilians from hitting the ground - they weren't contact fuzed. If they failed to explode on time they could kill civilians if the delay was long enough for the round - fired to explode at altitudes of c. 18,000-20,000 feet - to free-fall all the way back down before exploding. That would mean the fuzes were set for incredibly long flight times. I suspect that most of the casualties in Honolulu were actually caused by the Army 3" battery on Sand Island firing at low angles of elevation, although I still think it likely a 5"/51 was the culprit...why 150 rounds were fired from those is beyond me - they weren't AA guns.

[ROLAND1369]

The probability was that the 5 inch 51s were fired at the low flying torpedo planes to create a water detonated barrage fire for them to fly thru in the vain hope the water would knock them down. This was a prewar tactic used throughout the war. When at sea it was not uncommon at least for the Japanese to fire the main battery to attempt to create such a barrier.

[wm]

"They weren't contact fuzed" is important here because proximity fuses were very "contact."
The fuses being exceedingly dumb (only five tubes), would explode approaching ground at the (deadly) height of a few meters.

[reedwh52]

"They weren't contact fuzed" is important here because proximity fuses were very "contact."

No it is not important to this discussion. Per General Pile, Commander AA Command, proximity fuses were initially used after July 14, 1944. Most UK civilian casualties were before that date. (paras 78-80.)
http://www.ibiblio.org/hyperwar/UN/UK/L ... /38149.pdf

[wm]

The point is unexploded proximity fuses were more dangerous than clockwork fuses.

Simon Webb seems to believe that proximity fuses solved the problem of the unreliable self-destruction mechanism of clockwork fuses when in fact, proximity fuses required a self-destruction mechanism too.