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
Destroyers.....
- Thread starter Lucky13
- Start date
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
cherry blossom
Senior Airman
- 556
- Apr 23, 2007
I was trying to be careful. I knew that NW gave the new gun velocity for American and the average gun velocity for British guns, so I gave the British average gun velocity for the Bofor as a comparison. If you look at the Bofor entry Sweden, Britain, USA, Germany and Japan Bofors 40 mm/56 (1.57") Model 1936, you find:
"One firm rule adopted early in the redesign process was that any new Allied munition for these weapons needed to be completely interchangeable with existing designs. This allowed ammunition produced by any American or British ordnance manufacturer to be used with any weapon produced by either country, thus greatly simplifying the logistics problems of a world-wide war."
and
"USA Marks 1 and 2: 2,890 fps (881 mps)
UK Mark NI: 2,720 fps (829 mps)"
Which illustrates how interchangable ammunition gives different velocity in USN and RN publications.
Campbell:
"The gunnery report of Illustrious on the attacks of January 1941 is of interest...altogether about 30,000 rounds were expended." So the report covers the entire 13 day period of Jan 10 to 23 when she suffered numerous air attacks.
"The gunnery report of Illustrious on the attacks of January 1941 is of interest...altogether about 30,000 rounds were expended." So the report covers the entire 13 day period of Jan 10 to 23 when she suffered numerous air attacks.
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Glider
Major
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.
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.
I will follow this up
Interesting
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.
-You are verging on fantasy here. Please read:
http://www.admirals.org.uk/records/adm/adm186/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'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.
-The report is pretty clear in stating that most attacks would have to come within the envelope of a 40deg gun, and for dive bomber attacks, the pom-pom is always available.
- 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.
-The Stuka didn't have an unlimited ceiling except, apparently, against RN destroyers! The Stuka struggled to carry a 500kg bomb above 12000ft, and even then it meant a very short range. This has been gone over in the aircraft forum. Most IJN Val attacks were from 10-12 thousand ft. IJN level bomber attacks were typically flown at 9000ft.
j
- 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.
An appeal to all concerned:
Please read:
HMS Scylla Story, 1942 - 1943
which is an excerpt from Robert Hughes' book, Flagship to Murmansk. It is a very good summary and intro to RN AA during WW2. Hughes was an RN gunnery officer on the AA cruiser Scylla and I guess he never read through the Navweaps site because he seems to have felt that RN AA was very effective and provides real life examples to prove it. Hughes was the man controlling Scylla's gunfire during this film clip showing the defence convoy of PQ 18, where RN AA fire cut the luftwaffe to ribbons:
CONVOY TO RUSSIA - British Pathé
Please read:
HMS Scylla Story, 1942 - 1943
which is an excerpt from Robert Hughes' book, Flagship to Murmansk. It is a very good summary and intro to RN AA during WW2. Hughes was an RN gunnery officer on the AA cruiser Scylla and I guess he never read through the Navweaps site because he seems to have felt that RN AA was very effective and provides real life examples to prove it. Hughes was the man controlling Scylla's gunfire during this film clip showing the defence convoy of PQ 18, where RN AA fire cut the luftwaffe to ribbons:
CONVOY TO RUSSIA - British Pathé
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.
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.
Nelson to Vanguard states further that the USN offered not only to release the guns and FC systems for HMS Delhi but also to do all the work, including a general refit and the addition of a UK supplied CIWS at the same time - all in a US yard!. The yard situation in the UK was so tight at that time (mid 1941) that even if the USN had delivered the guns directly to the UK, the work could not have been done, except at the expense of other vital repait work. The 5in/38+Mk37 would have had to have been pretty terrible for the UK to turn down this offer, but IMHO, Delhi with 4 x 4.5in twins and RN FC would have been a better AA cruiser.
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...
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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
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
I never said that the RN thought that 40 degs was enough!
What I've been saying is that 40degs is not useless and that most air attacks could be engaged by destroyers with 40 deg guns - anyone who takes the time to read Lundstrom and First Team will know that in almost every case USN destroyers with 40 deg elevation could have provided the exact same AA support as they did in 1942. The problem is that most people seem to think that aircraft simply materialized directly over destroyers (but only RN destroyers), and they were helpless if they couldn't shoot straight up! Of course this is complete nonsense.
It certainly was a sign of desperation, to add single 3in or 4in guns - the problem being that the 20mm oerlikon was not yet in UK or Cdn production, nor was the Bofors 40mm in a naval mounting, and the quad pom-pom was in very tight supply, whereas these 3in and 4in guns were sitting around gathering dust...and so they were hauled out of storage and added to RN Fleet destroyers. Later in the war, most of these ships had the gun removed and replaced by TTs once again along with a greatly strengthened CIWS.
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parsifal
Colonel
The link didnt work for me....
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
I pretty much disagree with everything else that you are posting, but have made promises to other memebers not to hijack this thread any further. you might want to consider that as well.
XXXXXXXX
Im not saying that RN AA was not effective. I am saying that ton for ton, it was not as effective as USN AA. I am not looking at an isloated time frame, but overall and not hypothersiing too much about what if scenarios. Dollar for dollar, maybe a different story compared to the US. The RN was very good at getting the absolute best out of equipment that was often second or even third rate.
The criticism, and the topic, is about Destroyers, not the RN overall. It is not about a specific point in time, just the war overall. There are some pretty spectacular failures for the RN in terms of AA, but there are also some impressive victories as well. especially later in the war, just as the USN enjoyed its greatest successes later on.
Glider hit the nail on the head by describing the primary mission of Naval AA as preventing ship losses, not inflicting aircraft losses. Aircraft losse are a bonus, unfortunately we are often forced to rely on loss rates as a surrogate measure for overall performance, because thats al we have to go on. In the case of PQ18, RN flak was not effective. according to the 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.
In exchange for that the Lutwaffe torepedoed 8 ships, of which 7 sank. An eyewitness account by John Manners who was the First Lieutenant on HMS Eskimo i found interesting
"Then came September 13 when the Luftwaffe really went into action. There were continuous alarms starting with what we now know as diversionary attack by a number of high-level bombers. With misty conditions and a large amount of low cloud they had no success. Later at a crucial moment there were no Hurricanes airborne. With so few planes it was impossible to give air cover all the time.
Suddenly there was one of the most horrifying sights of the war. Along the whole horizon were aircraft flying just above the waves wing tip to wing tip and below radar cover. This was the German 'Golden Comb' attack in which all the planes released two torpedoes each at the same time. Records show there were forty-two Heinkel torpedo bombers and a number of Junkers 88′s.
Everything was happening – as soon as they were seen the commodore of the convoy ordered an emergency turn away in order to comb the tracks of the torpedoes but unfortunately the two starboard columns did not comply. Like all the others Eskimo put the helm hard over and increased speed, which made the ship list and heel over. These frantic manoeuvres made it impossible for any accurate gunfire. However, every ship blasted off with everything and the air was thick with bullets.
The Eskimo was in the starboard column of the screen and this menacing swarm passed a few feet overhead and as the aircraft were travelling at about 250 miles an hour they were gone before you could say 'Jack Robinson'. We were not their prime target and shortly after passing us they released no less than a 110 torpedoes.
In no time eight ships were hit, some sank at once and in one case, there was a gigantic explosion sending a column of black smoke vertically upwards and the ship vanished completely. The barrage that was fired at the attackers was terrific, but according to German records only five planes were shot down though many more must have been damaged.
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. Certainly the Luftwaffe had not taken serious losses as a result of the attack, and their attacks had not been seriously disrupted. By either measure of success...a/c losses or protection of ships, the RN could not claim success for its Aa on that day. Strategically the convoy was a success. Tactically for its flak forces, it was a defeat. The Luftwaffe was not cut to pieces, on the basis of its own records. Sheer dogged courage by the RN and the merchant crews ensured continued allied control of the sea space, but it was not a resounding success for RN flak by any stretch
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Fuze setting takes a fraction of a second with a machine fuze setter. By hand with the data transmitted by phone it takes:
This is an RN document from 1935-36, which I had requested that you read, Progress in Naval Gunnery, 1914-36, p142.
With machine fuze setters and direct data transmission from the FC computer as in the RN 4.7in twin mount, fuze setting was done very quickly, probably on the order of a second. In AA fire the guns are, of course being directed by the FC computer continuously and the layer/trainer will stay on target by matching their pointers throughout the loading cycle. This is how Hughes was able to report 16rpm while engaging high level Luftwaffe bombers with predicted fire.
The above example is also for a hand rammed 4in gun, but the increase in loading difficulty is not applicable to guns like the 4.7in or 4.5in twin that had a loading tray and power ramming.
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That's the losses for one day. If you continue reading from the same source:
http://www.luftwaffe.no/SIG/Losses/tap422.html
you will see how the Lufwaffe suffered severe losses on further attacks (not that shooting down 8 aircraft is a bust!).
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Glider
Major
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. When RN destroyers went to the Pacific they were given additional short range guns and you guessed it, they had 20mm/40mm/2pd added not 4in over open sights
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.
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The RN didn't have pom-poms, 20mm and 40mm bofors guns gathering dust that could be used to quickly augment destroyer AA, but they did have lots of older 3in and 4in guns that were not being used - sorry but that is the way it was. A 3 or 4in gun fired over open sights against an aircraft is no more accurate than any other gun fired with the same method; a pom-pom or bofors would have a much better hit probability because of the high RoF.
Here's Delhi's service record:
HMS Delhi, British light cruiser, WW2
note how she was tucked away in the Irish Sea during HARPOON and PEDESTAL. Hardly what you'd expect if she was supposedly the best AA ship in the RN...
parsifal
Colonel
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. In the early afternoon of the 14th the air battle around the convoy was renewed by a torpedo attack similar to that which had wrought such destruction the previous day, but smaller. This time the torpedo-bombers concentrated against the CVE Avenger and the escorting warships. This was significant to the air battle, because it allowed a concentrated defence to be mounted, and further, because the target was really just one ship (the Avenger), forced the LW to pass in close proximity of some defenders (ie a version of the "ideal scenario I posted) . However, despite at least 16 DDs being involved in the defence, the lions share of the defence was borne by the carrier and the A.A. ship Ulster Queen. these ships (and their escort) stood out from the convoy to gain freedom of manoeuvre, and the former flew off half a dozen Hurricanes. The fighters drove off some enemies which in turn assisted in their dedstruction , while the escorts' gunfire forced others to drop their torpedoes at long range. This was clearly a success for the AA, because the early release minimised convoy losses. However the actual aircraft losses does not seem to have had much to doo with the DDs efforts. At best we can say that the DD effects were inconclusive, at worst, that once again they were inneffective, at least in the kills they achieved (and this suggests inneffective LR DP armament) . No ships were hit and thirteen torpedo-bombers were shot down. 'It was a fine sight', wrote Admiral Burnett, 'to see [the] Avenger peeling off Hurricanes whilst streaking across the front of the convoy . . . Altogether a most gratifying action'.
Next came more bombing by Ju-88s. Though some ships, including the invaluable carrier, had narrow escapes, none was hit. Then more torpedo-bombers arrived, and again they made a dead set at the Avenger; but she was ready for them, and by clever organisation managed to get ten of her twelve Hurricanes in the air at the critical moment. They and the escorts' guns destroyed nine enemies. Once again the lions share of these credits were to the escorting cruiser and the carrier. several were credited to the CAP. I can find no special mention of DDs having much effect at all, but will stand corrected on this dayas action if you have specific information that credits them. I would say this days action is still inconclusive re the DDs effectivesness, but trending to support some effect.
One merchantman-again in the ill-fated starboard wing column-was torpedoed and blew up, and three Hurricanes were lost when they most gallantly accepted the risk of flying through the ships' barrage. Note the use of the word "barrage" which suggests directed fire was inneffective or not available. All the pilots were rescued. The last event of the day was another ineffectual bombing attack.
Next day, the 15th, was comparatively quiet-if such an expression can ever be used to describe a day with a Russian convoy in the Barents Sea. desultory attacks by a few enemy a/c amounting just over 50 sorties attacked, and they were well harried by fighters and gunfire. No ships were hit, but they were also no aircraft losses. Probably a success i guess for the escorts, and probably including the DDs. A lull in the air battle followed.
That same afternoon Admiral Burnett and the greater part of his force left PQ 18, to take over protection of the homeward convoy. PQ 18 received, however, a welcome reinforcement of four Russian destroyers by way of replacement. On the 18th, when at the entrance to the White Sea, the convoy was again attacked by a combination of bombers and torpedo-bombers. One ship was lost, but four enemies were destroyed-one of them by the Hurricane of the C.A.M. ship Empire Morn. The fighter pilot (Flying Officer A. H. Barr) then drove off other enemies by making dummy attacks, and finally flew 240 miles to an airfield near Archangel. He landed with four gallons of petrol left. A last enemy attempt was made on the 20th while the convoy, as though it had not already endured enough, was trying to shelter from a full gale which had blown up. Luckily no damage was done.
So, whilst losses were indeed heavy, there is no real evidence (as yet ) that such losses or defensive successes were attrributable to the DDs. so does nothing to support the notiuon that DD AA fits were satisfactory. probably the opposite in fact.
With regard to the subsequent days of PQ18 , my sources are slightly different. In the early afternoon of the 14th the air battle around the convoy was renewed by a torpedo attack similar to that which had wrought such destruction the previous day, but smaller. This time the torpedo-bombers concentrated against the CVE Avenger and the escorting warships. This was significant to the air battle, because it allowed a concentrated defence to be mounted, and further, because the target was really just one ship (the Avenger), forced the LW to pass in close proximity of some defenders (ie a version of the "ideal scenario I posted) . However, despite at least 16 DDs being involved in the defence, the lions share of the defence was borne by the carrier and the A.A. ship Ulster Queen. these ships (and their escort) stood out from the convoy to gain freedom of manoeuvre, and the former flew off half a dozen Hurricanes. The fighters drove off some enemies which in turn assisted in their dedstruction , while the escorts' gunfire forced others to drop their torpedoes at long range. This was clearly a success for the AA, because the early release minimised convoy losses. However the actual aircraft losses does not seem to have had much to doo with the DDs efforts. At best we can say that the DD effects were inconclusive, at worst, that once again they were inneffective, at least in the kills they achieved (and this suggests inneffective LR DP armament) . No ships were hit and thirteen torpedo-bombers were shot down. 'It was a fine sight', wrote Admiral Burnett, 'to see [the] Avenger peeling off Hurricanes whilst streaking across the front of the convoy . . . Altogether a most gratifying action'.
Next came more bombing by Ju-88s. Though some ships, including the invaluable carrier, had narrow escapes, none was hit. Then more torpedo-bombers arrived, and again they made a dead set at the Avenger; but she was ready for them, and by clever organisation managed to get ten of her twelve Hurricanes in the air at the critical moment. They and the escorts' guns destroyed nine enemies. Once again the lions share of these credits were to the escorting cruiser and the carrier. several were credited to the CAP. I can find no special mention of DDs having much effect at all, but will stand corrected on this dayas action if you have specific information that credits them. I would say this days action is still inconclusive re the DDs effectivesness, but trending to support some effect.
One merchantman-again in the ill-fated starboard wing column-was torpedoed and blew up, and three Hurricanes were lost when they most gallantly accepted the risk of flying through the ships' barrage. Note the use of the word "barrage" which suggests directed fire was inneffective or not available. All the pilots were rescued. The last event of the day was another ineffectual bombing attack.
Next day, the 15th, was comparatively quiet-if such an expression can ever be used to describe a day with a Russian convoy in the Barents Sea. desultory attacks by a few enemy a/c amounting just over 50 sorties attacked, and they were well harried by fighters and gunfire. No ships were hit, but they were also no aircraft losses. Probably a success i guess for the escorts, and probably including the DDs. A lull in the air battle followed.
That same afternoon Admiral Burnett and the greater part of his force left PQ 18, to take over protection of the homeward convoy. PQ 18 received, however, a welcome reinforcement of four Russian destroyers by way of replacement. On the 18th, when at the entrance to the White Sea, the convoy was again attacked by a combination of bombers and torpedo-bombers. One ship was lost, but four enemies were destroyed-one of them by the Hurricane of the C.A.M. ship Empire Morn. The fighter pilot (Flying Officer A. H. Barr) then drove off other enemies by making dummy attacks, and finally flew 240 miles to an airfield near Archangel. He landed with four gallons of petrol left. A last enemy attempt was made on the 20th while the convoy, as though it had not already endured enough, was trying to shelter from a full gale which had blown up. Luckily no damage was done.
So, whilst losses were indeed heavy, there is no real evidence (as yet ) that such losses or defensive successes were attrributable to the DDs. so does nothing to support the notiuon that DD AA fits were satisfactory. probably the opposite in fact.
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Try this:
http://www.admirals.org.uk/records/adm/adm186/adm186-339.pdf
From the same account by John Manners:
OK, I'll bow out for a while, but Avenger was given AA support by two Hunt class destroyers, WHEATLAND and WILTON. They had essentially the same AA FC as a Tribal or JKMN destroyer. Without reading all their action reports, it is impossible to draw any conclusions as to destroyer effectiveness however, it certainly was an overall victory for RN AA under rather trying conditions.
parsifal
Colonel
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. The other thing to remember is that when the target gets really close, the gunners switched over to "barrage fire" where the fuse was preset to ~2 seconds (typically a supply of prefused ready use ammo was kept handy) and the gunners loaded and fired as fast as they could. At longer ranges, (~6000 yards, for example) the target has relatively little apparent motion and the layer/trainer have a relatively easy time keeping on target, and there is very little movement of the gun - at 6000 yards a 270 knot crossing target would have an apparent motion of only 1.5 degrees/sec, and much less if the target is flying partly or directly towards the firing ship.
Chatfield was optimistic, but then so was the USN who made much the same assumptions, with similar results - the only problem is that we are told that the USN did much better than it really did and so we find the RN wanting, when it really wasn't, relatively speaking.
BTW, this is a very interesting website dealing with the RN in Norway:
http://www.royal-naval-reserve.co.uk/rutlandshire/default.htm
specifically the loss of the Rutlandshire, but it has some RN action reports and a report by the Norwegian pilot who creditted RN destroyers with effective AA, that greatly reduced the intensity of Luftwaffe attacks, and it also details the loss of the He-111 which bombed Rutlandshire (and was probably fatally damaged in return) - a loss which doesn't show up on the Luftwaffe Norwegian loss list.
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parsifal
Colonel
I was aware that section 2 does deal with the 4in gun, but this particular extract refers to all dead times, for both claibres, , not just not just the 4in.
We dont know about the 4.7 twin, but it has the same published rof as the 1936 models. Power ramming still requires hand loading and can involve innefficiencies because of the poor placement of the shell hoppers, so I have to disagree with you. the power rammer might add or improve fireing cycle by 1-2 seconds over the older mounts but that still brings it in at somewhere below 12 rounds per minute. Given that 12 is already an indaequate number, the conclusion whether it be twin mounting or no, remains the same.
If as I suspect the older models at non-optimal elvations can only fire at around 6 rpm, and power ramming improves that practical rof by say 1-2 secs, then you might get 8 rpm. still within the original estimate for practical rof of 4-8 rpm. 4 for the really old versions, 8 for the newer twins.
Sorry, still dont agree with you. Far too rose coloured a view of the RN capabilities in my book.
