Exactly. The original proposal for Delhi, for example, was to arm her with 4.5in twin mounts and UK AA FC, but these couldn't be produced in the UK
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Glider, I did not know that there was a supply / demand problem with the 4 inch.
Is it possible then that the RN were trying to buy any gun that had some potential as an AA weapon?
Actually, the 40mm HV pom-pom had a MV of 2400fps. I afraid you ran afoul of Navweaps dissing RN equipment again.
It isn't that I don't accept solutions, what I do not accept are solutions that lack logic or support. You rightly say that the Admiralty took steps to improve short range weapons. But then ignore the fact that the 4in isn't a short range weapon. Its a long range weapon that would be of little use against a dive bomber. The first steps taken to improve short range defence was the swapping out of 0.5 mg and replacing them with 20mm. To say that installing a 4in helps short range defence is wrong, plain and simple.1) I have answered this several times and even produced and RN document to back up my case:
"9. It appears that enemy aircraft wait about overhead where they are impossible targets for destroyers and difficult for any ship. Steps are being taken to strengthen the short range armament of destroyers who have to operate within the range of dive bombers. It is to be recalled however that except for special aircraft for steep dive bombing and level bombing from considerable heights enemy aircraft must come within the envelope of a 40 degree gun when approaching for an attack."
I think you should, rhetorically, speak to the Admiralty who wrote the above excerpt, and not to me. I have explained why they added a 4in twin - you can choose not to accept my explanation, or the Admiralty's explanation which is summarized above. You keep repeating that the twin 4.7in was a SP gun, even though I have very patiently produced reams of documentation to proof otherwise, including an Admiralty memo, which explicitly states that the 4.7in gun was intended for use against aircraft although the fact that the 4.7in twin had an on mount fuze setter which was directly linked to the AA FC computer should have ended any doubts that you might have had. The 4.7in/50 twin on the LM wasn't dropped, the UK simply couldn't build enough of these complex mounts fast enough to meet demand - heck they were arming some destroyers (OP class) with WW1 vintage 4in MK V single mounts, out of shear desperation and many others with the 40deg 4.7in single.
Wrong. Lend lease was not free and nearly all US weapons were under lend lease and they had every intention of getting as many as they could.2) The RN had no intention of buying USN 5in guns or MK37 FC systems - they wanted to acquire them for free under lend-lease, for the simple reason that you yourself have pointed out: "demand outstripped supply" and the UK armaments industry, simply couldn't supply enough UK built guns and FC systems, forcing a request for US supply. Unfortunately, the USA would not build any weapon to UK specs unless it was approved for use by the the US Military (AFAIK only the 6pdr ever met this requirement) which is why Canada built RN spec weapons but not the USA - if the RN wanted to acquire DP naval guns in the USA they had to be USA spec weapons. See North American Supply by Hall for more information on this aspect of lend-lease. For example the RN wanted the USN to adopt the pom-pom so that both navies could have these weapons produced quickly in the USA, but this was turned down and the delay in producing the Bofors 40mm meant that very few USA built Bofors guns were provided to the RN, under lend-lease.
I will follow this up3) All Mk 33 class USN destroyers used a fuze setter (the shell was put in the fuze setter nose first and then had the timing set) which was very similar to that used on RN 4.7in twin mounts. It seems that you don't understand how AA fuze setting works; a shell is placed in the fuse setter, the FC computer predicts the time of flight needed to hit the target and sends this data to the fuze setter and the FC computer predicts far enough in advance to allow to shell to be fused, loaded and then fired according to the salvo interval selected. For an explantion of how RN AA worked, please read: The Gunnery Pocket Book - Part 4
Interesting5) Yes, and the practical RoF, as used in combat was 10-12rpm for the RN twin, 12-15 for the USN Mk 33 5in/38 and 15+ for the USN Mk 37. Robert Hughes, an RN gunnery officer gave a real life example of the RN 4.5in twin being fired at 16rpm in predicted fire where each shell had to be fuzed in the fuze setter, and Campbell quotes Illustrious' action report as stating that she fired 3000 4.5in rounds at an average of 12rounds per gun per minute. March reports that HMS Kimberly fired 180 salvos at Narvik, with most having a 5sec firing interval.
6) Vian accomplished just that with his Tribal class destroyers while defending a 5 knot convoy from a day long luftwaffe attack.
Agreed it does depend on the bombers elevation but also on the guns elevation. If you look back at the chart you posted the 40 degree elevation gives you approx 40 seconds to fire at a level bomber before you can no longer fire at it. The 80 degree elevtation doubles that time. A destroyer is lucky to hit another ship within 40 seconds let alone a small aircraft. Equally important by ceasing fire you let the bomber concentrate for a precious 40 seconds and significantly improve their accuracy. Having an 80 degree elevation stops that happening. That is my undersanding is why the Tribals were given a twin 4in instead of the twin 4.7. It had nothing to do with improving the short range weapons.7) It all depends on the bomber's elevation. At very high altitudes they couldn't hit ships either.
-You are verging on fantasy here. Please read:No, you have not. according to Terry Giulan (In an essay dated 2009, entitled "The British High Angle Control System", reproduced in NW, but not where i found it), he provides a clue on the differencews between cyclic rate (or as I call it max rof), and max sustained rof (which I and some others refer to as practical rof). He says:
"Almost all destroyers with 4.7-inch guns had the HE time fuzes set by hand. This affected the firing solution not only by the time setting itself, but also in that the fuze setter became the critical time factor. No matter how fast the guns could fire or how quickly ammunition could be supplied to the mountings, even a well-trained fuze setter needed about 4 to 5 seconds to handle the round and set the fuze properly. Faster speeds invariably resulted in improper fuze settings and loss of effectiveness. These factors encouraged the use of barrage firing as it meant that all fuzes were set the same, thus requiring less time by the manual fuze setters.11 Most larger ships used fuze setting machines, but all of these could only handle one round per barrel at a time, thus slowing the practical rate of fire. An interesting but unfortunate side effect of these fuze setting systems was that the "dead time" between the point that the shell left the fuze setting machine and the point it was fired out the gun needed to be calculated based upon the slowest gun crew on the ship. As the guns were fired by remote control, this effectively meant that all salvos had but a single time setting. Again, this slowed the practical rate of fire".
On top of that, the redesignof the mounting itself wqas not conducive to fast loading. In a static situation, with the gun not moving, I have no problem in accepting 10-12 rpm. But in a real combat situation you have two major constraints that are not present for the 5/38. Firstly you have this manual fuze setting, which at minimum adds 4-5secs to the theoretical max rof. Then you have the poor design of the turret. relative to the gunner, the ammunition supply point was fixed, making it easy to become disoriented. For the single mounts you had a further complication, the hand ramming.
If the theoretical max rof was 12rpm, or 5 secs, you must then add 5 secs for the manual fuze setting and then some unknown time for the turret issues....say 2 secs per round. That reduces the practical rof for the 4.7 down to about 6 rpjm, or more approximately 4-8, which is a better way of describing it, gieven the variable human factors at work.
Now, neither of those constraints affects the Mk 30 5/38 turret. So its practical rof fire is going to be much closer to the max rof. The max rof is not 12rpm for the mk 30, as you are still saying....its 24 rpm. But the practical rof is somewhere between 15-22 rpm. I suspect the director issues you mentioned are the main cause for this downgrading in efficiency. but a more realistic comparison, if we want to use practical rofs, is to estimate the 4.7 at 4-8 rpm, and the 5/38 at 15-22 rpm.
-I'm looking at the 5in without integral hoists because that was the only USN DP gun in service in April 1940 (Norway) and we know that Mk 37 had major teething troubles, so it would not have been a servicable weapon system for sometime after it's first introduction.no. Clear evidence that they have supporting material to inidicate lower standard of efficiency for the 4.7, in comparison to the 5/38. this is not a popularity or political excercise. i think it an excercise in trying to give an accurate assessment of true capabilities of each gun, taking into account various hidden factors. .
.
The operational results that we have dont support that claim. US destroyers seem to have been more survivable and achieved overall more efficient standard of fleet and unit protection with their weapons than the RN was able to achieve. There may be good mitigating circumstances for that, but given the FC system is so critical to getting decent results I think it entirely reasonable for NW to take the position they do. Others can perhaps explain the technical side better than I, but the operational results speak to me better than any theoretical technical analysis. the USN destroyers did better than the RN destroyers. Its as simple as that.
The higher standard of CIWs was theoretical rather than actual, but was more or less forced on the RN because of the failure of their 4.7s as a true DP weapon. I say the CIWs were theoretical because really if we are talking British CIWs we are talking 2 pounder guns. these lacked satisfactory performance to be really held up as good or efficient. No tracer, effective range of about 1700m (according to the RN) too many stoppages no relaiable explosive shell. All adds up to an inneffective CIW. So, whereas the USN entered the war with at least a good and true DP main, the RN went to war with neither a good DP main, or a decent CIW either.
No need to apologise. its allo good. we are still rexchanging information and not insults. Dont agree that NW has much bias, for reasons already given. You are looking at the 5/38 without integral hoists, which makes a huge difference. Its pronbaly no exaggeration to say that more than 80% of 5/38 mounts built were mk 30 hoists with integral hoists. I think it far more relavant to the topic to look at the typical or prevalent type rather than pick an islated or minority failure. and as ive tried to show previously, 10 rpm for the 4.7 is not a realistic estimate of the real rof for this weapon
The report you posted does not say what you are claimimg for it. It say, essentially, that those types of attacks that fitted within the envelope they specified, could be countered. It goes on to say, virtually, that in other situations....panic, because you will not be able to hit anything with the equipment we have given you. You cannot make any claims about the 5/38 because it was not engaged in Norway. We need to keep opinion out of the way of known facts.
Nope, dont agree. Previously posted why, due to slow training rates and rofs, and the short range of the ciws, could not be effectively engaged in many situations. Lucky for the RN, the Germans were even more remiss in not having an effective air launched torp until later in the war.
I dont know that we can nail a typical approach altide too well. Even at 3-4000 m there would be difficulties for the RN. but even if it was possible, the option was there for the LW simply to fly above the effective ceiling of the gun
- They "gained" the survival of their ship and after their first taste of RN AA, the Stukas never again attacked Illustrious with the same fervour.Regardless, they exopended huge amounts of ammunition for virtually no gain. In any even, wiki suggests thats not the case.....they say that 30000 rounds were expended in the 1st attack. if youve got better, would be great to see it.
It isn't that I don't accept solutions, what I do not accept are solutions that lack logic or support. You rightly say that the Admiralty took steps to improve short range weapons. But then ignore the fact that the 4in isn't a short range weapon. Its a long range weapon that would be of little use against a dive bomber. The first steps taken to improve short range defence was the swapping out of 0.5 mg and replacing them with 20mm. To say that installing a 4in helps short range defence is wrong, plain and simple.
Lendlease meant that the UK could acquire US hardware with no capital outlay - effectively free. There was some reciprocal obligations but these were not directly tied to UK acquisitions so if the USN released 500 5in/38 guns to the RN, it did not require a direct obligation for compensation in kind. All lend-lease required from the UK was the obligation to provide what ever it could, that was surplus to it own requirements. The RN never dreamed of purchasing 5in guns and USN FC because the UK simply didn't have the hard cash needed to do that. Acquiring 5in guns only became feasible after lend-lease. Nelson to Vanguard, p156 states that the original intention was to arm the D class cruisers with 4 x 4.5in twin mounts each but upon the outbreak of war in 1939 this was no longer possible, probably because of a lack of yard space. The two sets of 4.5in guns that were ordered went into Scylla and Charybdis, because of a shortage of 5.25in mounts. The UK naval armaments industry was badly overstretched during WW2 and many of the plants working on RN weapons and FC were bombed in 1940/41 further adding to the backlog.Wrong. Lend lease was not free and nearly all US weapons were under lend lease and they had every intention of getting as many as they could.
Hello RCAFSon
if RN thought that 40deg was enough why then the last 4.7" DD mount had 55deg max elevations as had the 4.5" mounts which were the main gun armaments of the late war RN DDs? And IMHO it was a sign of desperation to halve torpedo armament of Fleet DDs during early war years just to get one 12pdr/3" (on pre-Tribal DDs) or 4" (on J-M classes) HA gun capable only local control firing onboard.
Juha
You are verging on fantasy here. Please read:
http://www.admirals.org.uk/records/a...adm186-339.pdf
starting at PDF page 142, for an explanation of maximum and usable RoFs for RN 4.7 and 4in HA mounts. The deadtime is not additive to the cyclic rate of the gun, it is part of it. Please if you don't understand this, then don't try to wing it, because it just confuses all concerned. I've done a lot of reading about this subject lately, and it takes some time to grasp the concepts involved.
I used your own scenario to show how the RN would fire just as many rounds as the USN destroyers in the same time frame - the problem is that to make your argument work you have to cut the RoF of RN guns by half and you refuse to present any supporting data for this rather startling conclusion.
At 12 rpm the rof for the gun is 5 secs. Di Giulan says that fuze setting takes 5 secs. If that is part of the firing cycle, that leaves 1 second to traverse the turret, get instructions from the director, collect the shell, load the weapon, aim the weapon and then fire it. Some of the timesetting the time fuze can be done wholst other things are happening. But some things have to be done sequentially. Seting the fuze by hand, in the turret, is amajor constraint on the weapon system efficiency.
Glider made a better explanation than i
No, you made assumptions that are still being debated
This is an RN document from 1935-36, which I had requested that you read, Progress in Naval Gunnery, 1914-36, p142.Dead Time
6. Dead time is made up from:
(a) Time to predict and transmit a new fuze by voice - say 1.5 seconds.
(b) Time to receive and set this fuze at the fuze setting position- say 1.5 seconds.
(c) Time to load, lay the gun from loading elevation and fire it.
Notes. - (a) and (b) are fixed factors which, with hand fuze setters, cannot be reduced and may be exceeded.
(c) is a variable factor depending on the firing elevation. At the easier loading elevations from 2 to 3 seconds is the minimum.
Luftwaffe in Norway website, as best as I can tell the LW suffered the following losses
13.9.42
at about 16.00 hrs torpedo attack of I./KG26 - four He 111s were hit by naval flak and must be ditched. Two crews (He 111H-6 2./KG26 W.Nr.4727 and 1H+BK W.Nr.4535) were rescued by air sea rescue aircraft.
The crew of 1H+NK W.Nr.7567 was rescued by U-457. The crew of 1H+DH W.Nr.7076 was not found.
Next attack had been flown by 18 Ju 88s of III./KG26 - Ju 88A-4 W.Nr.142018 1H+KS was shot down by naval flak, crew posted MIA.
Two Ju 88s: W.Nr.2097 and 1536 were hit and damaged - they crashed on landing at Banak.
At 16.15 hrs the convoy had been attacked by 9 He 115s of K.Fl.Gr.406. One Sea Hurricane of 802 Sqn FAA was forced down by German air gunners.
At 20.35 hrs 12 He 115s of 1./906 arrived. He 115 W.Nr.2247 8L+FH was brought down by naval flak as first. Three MIA.
At 21.00 hrs Ju 88As of I./KG30 bombed the convoy. All returned but two from 3./KG30 collided on landing at Petsamo: W.Nr.1007 written off and W.Nr.2064 45%.
I count 6 losses at the scene, and a further 2 crashing on landing due to flak damage. There were other non-combate related losses that i have not inlcuded.
Also on 13 September the convoy was again sighted by a reconnaissance aircraft, a BV 138 from Banak. The air forces at Banak mounted a full assault on the convoy, using a new anti-convoy tactic, called the "Golden Comb". This involved a mass torpedo attack by full group of torpedo bombers, and resulted in the sinking of eight ships from the convoy. Two more air attacks followed, but failed to score any hits. In all eight aircraft were shot down on this day.
The following day, 14 September, the attack was repeated; on this occasion, however, the escort force had developed counter-measures to the form of attack, and the massed AA fire from the convoy and fighter attacks, the result of aggressive handling by the carrier Avenger and the AA cruiser Ulster Queen, saw the attack broken up. Three air attacks saw one ship hit and sunk, while 21 aircraft were shot down. The 14th also saw further U-boat attacks. The tanker Atheltemplar was torpedoed by U-457; she was abandoned and sank later. In counter-attacks U-589 was destroyed by Onslow.
On 15 September there were further air attacks but these were again beaten off, without loss. After this there was a pause in the air offensive, as the official despatch states:
"During the whole period, just over two days, of concentrated air attack, the enemy lost at least forty aircraft: there can be little doubt that these heavy casualties, especially among his limited supply of really skilled torpedo pilots, was largely responsible for the steady decline in the size and vigour of his attacks." [2]
[2]http://www.ibiblio.org/hyperwar/UN/UK/LondonGazette/39041.pdf
Convoy PQ 18 - Wikipedia, the free encyclopedia
Well we are going to have to differ.I'm sorry but you're wrong. Most destroyers had 4in guns added in lieu of a set of TTs; these guns were aimed and fired over open sights, and thus they were additions to the CIWS. The Tribals were a happy exception as the 4in twin could be coupled to the AA FC system, but when countering dive bombers they were used with short range "barrage" fuze settings, and they probably engaged the DBs over open sights as well, and their effective range in that mode was hardly greater than a pom-pom.
I think you will find tha the Delhi had her stern blown off in action which was why she was not available. Many ships were repaired and refitted in US shipping yards there was nothing special about the Delhi just that she was given US guns.Delhi is often held up as a shining example of superior USN guns and AA FC, but AFAIK, Delhi was a bit of a bust in actual service and she was held back from the really critical Malta convoys in June and August 1942 , when the RN had no problem committing 4in armed C class AA cruisers to defend those convoys and 40 deg elevation destroyers...
Well we are going to have to differ.
My definition of a short range AA gun is a fast firing HMG/20mm/40mm ect. My definition of a Heavy AA is a 3in upwards that fires shells
Your definition of a short range AA gun is something that fires over open sights. So a 4in linked to a fire control on an AA sloop/ Hunt is presumably a Long range heavy AA gun. The same gun fired over open sights is a short range AA gun.
Your definition is so wrong its untrue. Some of the RN AA sloops were originally armed with 8 x4in but had one taken out and replaced with a quad 2pd because it lacked short range defence. The JKN class had by the standards of the day quite effective short range weapons with a quad 2pd and the 0,5 replaced with 20mm but had a 4in added instead of the TT not because they needed short range defence but because they needed a HA heavy gun with a long range.
I think you will find tha the Delhi had her stern blown off in action which was why she was not available. Many ships were repaired and refitted in US shipping yards there was nothing special about the Delhi just that she was given US guns.
The link didnt work for me....
An eyewitness account by John Manners who was the First Lieutenant on HMS Eskimo i found interesting
"...The situation was depressing with a fifth of the convoy having been lost and nobody in Eskimo saw any enemy planes destroyed. Two further desultory bomber attacks took place"
On the basis of the eye witness account RN flak was inneffective on this occasion.
...German aircraft destroyed, taken from their records were: 44, including 38 torpedo bombers and surely a large number more must have been damaged. Of their 12 submarines 3 were sunk, another 5 were damaged. They therefore suffered quite substantially...
well, i think between the thee of us we have tried our very best to get some consensus but unfortunately just cannot reach agreement. Some believe RN AA was okay to good, others of us believe it was a weakness in their Destroyer designs. I think we need to move on now and let the other guys have a go and make their own minds up.
With regard to the subsequent days of PQ18 , my sources are slightly different...
Try this:
http://www.admirals.org.uk/records/adm/adm186/adm186-339.pdf
From the same account by John Manners:
RCAF that is a great piece of information, and i see why you are saying what you are. I want to thank you for the trouble you have gone to in posting this stuff
In these situations there is always or invariably a "however" and I have several"howevers" on this document. Its clear that by 1936 at normal elevations a rof of 12 rpm for the 4.7 was expected, however, this was only at certain optimal elevations. The report specifically states "the rates of fire and dead times commented on in section 1 (which is what you have already posted) can only be adhered to between certain elevations....." the report does not further investigate this issue.
So at higher elevations, the rof was not 12 rpm. maybe at 40 degrees or below, though I am doubtful. For a gun like the 4.7 I would say the target had to be stationary and not changing position and the gun elevation below 30 degrees to achieve that optimum rof.
The second "however" is that this report is still drawn up in peacetime conditions and assumes near perfectly trained crews. it says that repeatedly in the report. That means ships steaming at a leisurely pace, with no changes to elevation or traverse. Wartime conditions were very different. Moreover the amount of "deatime was for an aircraft travelling at 100knots. By 1940 this was greatly exceeded, meaning that dead times would also increase. The old perrennial problem of slow traverse and elevation times again begins to dog the 4.7.
As a corollary to the second point, this report was prepreed at the time Chatfield was in charge, a time when the RN grossly over-estimated its AA abilities.Chatfield told Churchil that a single 4in gun would be suficient to protect most Destroyers from even the heaviest air attacks......
So this report, in my opinion, whilst certainly opening my eyes to some issues, does not prove your position. quite the opposite really...it shows that 12 rpm could only be achieved under ideal conditions. And warime conditions against aircraft were anything but ideal for the 4.7.....
Its also clear why the 4in was favoured the main AA weapon....its much higher max elevation and rof...around 20 rpm and more like 55 deg elvation. still not enough to be fully effective, but better, much better.
You will note that page 142, section two is dealing with the 4in gun. This gun doesn't have a loading tray, therefore it gets more difficult to load at both low and high angles. The power rammed 4.7in single and twin did not have this problem. Dead time has nothing to do with target speed - it is solely a problem of setting the MT fuze and loading the gun.