Im afraid I agree with glider on this one (and no, we are not conspiring against you RCAFson) . The article you posted from wiki includes some comments from Vian about the inneffectiveness of the 4.7" DP mount against aircraft. Not a complete waste of time, i will grant you, but not greatly effective either. As i recall Cunningham was similar in his view, though I cannot find at the minute his exact comments.
There were a number of problems with the 4.7" but more particularly its mount and support equipment. Some of these problems had little to do with the actual gun or the mounts. The RN adopted a faulty method of HA fire control for its medium and heavy batteries. i confess im not 100% certain of the specific types of directors used in given Destroyer classes, though I do know that the Battles were fitted with a "Mk VI" director and another apparatus called a "Mk XL corrector". However Campbell is pretty damning of all British pre-war direectors because of their methods of stabilization....in practice they proved incapable of dealing woith aircraft that were chamging course and or speed or altitude. they were better than nothing, but compared to the USN HA directors, were pretty average affairs.
For HA Short range weapponary, most work was done as over open sights until late in 1942. After that date , RN DDs began to receive some elementary beam switching gear. Dont ask me to give a detailed explanation, all I know is that it was linked to radars to give a pretty good indication of deflection and other corrections to the gunners of the LAA batteries. But in 1939, director control for the LAA in the RN was almost non existent.
The other problems with the 4.7 in mountings are squarely to with the gun and the mounts they were put into. The gun mounts, to put it mildly were simply too slow in both training speed and elevation to be effective, and as i suspected, the gun could not be loaded above 40 degrees elevation. The best turrets housing the 4.7 had a training sppeed of 10 degrees per secons and a max elevating speed that was the same. by comparison, the 4.5s in the battles were nearly twice that speed. The USN 5/38 had a traverse speed of 34 degreees per second and and elevating speed of 18 degrees per second. put simply the 4.7 was too slow to be effective, and wasnt well directed until later in the war
Vian states that AA fire from 4.7in guns prevented a single hit from an attack lasting many hours, on a whole convoy moving at 5 knots, through narrow waters - if RN destroyer AA was so ineffective why didn't the bombers press in to low altitude and annihilate the convoy? What was the luftwaffe afraid of? Do you really think that USS Maury could have done any better? Mk 37 wasn't even service in April 1940, and the Mk 33 system on Maury and most of the prewar USN destroyers was an obvious failure as the USN itself admitted.
I have a feeling that the effectiveness of USN AA systems has been greatly exaggerated and this has given the impression that if only the RN had similar systems that all would have been well...yet a read of the two volumes of
First Team, will show you that USN AA simply didn't do well and was hardly a factor in the first year of the war, until Santa Cruz, and then it was massed CIWS fire that proved effective, not 5in Mk 37 fire.
I think XL means "cross level" as GXLC means "Gyro cross level corrector" and Campbell states that it was part of the director, not a separate unit. Cross level correction was only really important at very high angles while firing far forward of the beam, and so was not an issue for Tribal class AA although there was a cross level corrector in the LA firing circuit.
No WW2 AA system could deal with aircraft that were changing course or speed and/or changing altitude since all WW2 AA computers could only predict straight-line target motion, and assumed that the target would fly at a steady speed during the prediction cycle. Mk37 could predict motion based upon a steady rate of climb or descent, but only if the target flew level in a straight line at a steady speed. As for 10degs/second traverse, it was plenty to track low elevation targets:
A 270 knot (500 km/h) target crossing the line of sight at right angles, at 2000 yards (1829 m) range, will move across the line of sight at 4.5 degrees per second. This simple fact of geometry appears to contradict the assertion that a 10-degree-per-second traverse rate was too slow to track a high-speed aircraft.
Higher speeds were only needed against very close range targets ( AFAIK higher speeds are only needed to engage dive bombers that are nearly directly over the ship) but the AA computers, including MK 37 were not effective at such high angles anyways because they were to slow to compute the needed corrections, and MK 37 was not accurate above 70 degs due to it mechanical limits:
Historic Naval Ships Visitors Guide - Computer Mark 1 and Mark 1A
http://www.hnsa.org/doc/computermk1/pg380.htm
After the war electrical computers could do much better.
Beam switching refers to a method of getting accurate bearing information from a radar; the radar beam is switched rapidly between the left and right sides of the antennae and if the radar antennae is not centered on the target, the target will flicker on the display tube. After 1942 beam switching was introduced on type 285 and type 282 radar.
Most RN destroyers used eye shooting for CIWS AA until late war when the Simple Tachymeyric Director ( similar to Mk 51) began to be fitted to some destroyers to control CIWS guns, and some pom-poms were fitted with gyro gunsights similar to the USN Mk 14. USN destroyers began to receive Mk 51 in 1943 to control twin bofors mounts, although the RN Hazemeyer was theoretically far more accurate, it was not very reliable. Almost all RN cruisers and larger ships had director control of pom-pom mounts starting around 1930, where the USN didn't have director control of 1.1in or Bofors guns until 1942.
The USN admitted that MK 33 was a very poor director:
The USN never considered the Mk 33 to be a satisfactory system, but wartime production problems, and the added weight and space requirements of the Mk 37 precluded phasing out the Mk 33: "Although superior to older equipment, the computing mechanisms within the range keeper (Mk10) were too slow, both in reaching initial solutions on first picking up a target and in accommodating frequent changes in solution caused by target maneuvers. The Mk 33 was thus distinctly inadequate, as indicated to some observers in simulated air attack exercises prior to hostilities. However, final recognition of the seriousness of the deficiency and initiation of replacement plans were delayed by the below decks space difficulty, mentioned in connection with the Mk28 replacement. Furthermore, priorities of replacements of older and less effective director systems in the crowded wartime production program were responsible for the fact the Mk 33's service was lengthened to the cessation of hostilities."[19]
Ship gun fire-control system - Wikipedia, the free encyclopedia
and:
From the "Sham battles" we had with our own carrier planes, it became clear that in war we would be subjected to attacks which broke very quickly, seldom with any warning. When an incoming plane was sighted, we would struggle to get our director's sights on target, measure the rapidly closing range, adjust the Mk-10 to a solution and simulate opening fire before the attacker could complete his attack. Frequently we'd still be "slewing" the director to get on target when he roared overhead, attack completed. We held tracking drills at every opportunity to improve our ability to acquire targets quickly, but we had no mechanism to point out the target to the men on the director's telescopes—the control officer had to coax them on by voice. I became seriously concerned that we couldn't handle incoming dive or strafing attacks.
http://destroyerhistory.org/goldplater/ussmaury/index.asp?r=40130&pid=40131 (the MK 33 director contained a Mk 10 rangekeeper (computer) )
but one would never know about these problems by reading Campbell because he glosses over defects in the USN AA firecontrol, while being highly critical of less serious problems in RN AA fire control.
