British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Guns, torpedoes, mines, bombs, missiles, ammunition, fire control, radars, and electronic warfare.
wmh829386
Member
Posts: 139
Joined: Mon Oct 04, 2021 5:43 pm

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by wmh829386 »

dunmunro wrote: Tue Jan 18, 2022 9:07 am
dunmunro wrote: Sun Jan 16, 2022 10:04 am
wmh829386 wrote: Sun Jan 16, 2022 3:05 am

You are quoting AFCC manual, but the data flow diagram from Tribals shows the FKC directly generate gun elevation order, bypassing AFCC. There is no wind input at the FKC so elevation is not corrected. You might want to check it again.
https://www.kbismarck.org/forum/downloa ... hp?id=3921

There's three inputs:

Gun deflection = wind input
Gun elevation
Gun range = Wind input. Gun range is a modifier to gun elevation.
From the FKC Handbook:
In ships carrying the A.F.C.C. Mark 1 the total elevation correction found by the fuze
keeping clock is added to director elevation in the fuze keeping clock and then transmitted
through the gun elevation synchronous unit direct to the guns. In later ships carrying the
A.F.C.C. Mark 1** the total deviation correction is added by follow-through magslip to director
elevation in the gun elevation synchronous unit.
In ships carrying the transit the total elevation correction found by the fuze keeping clock
is transmitted electrically to the transit which produces gun elevation and transmits it to the guns.
In ships carrying the fire control box the total elevation correction found by the fuze
keeping clock is transmitted mechanically to the fire control box where it is added to director
elevation and transmitted as gun elevation to the guns.
Thanks again. That's good information.
So only AFCC MkI** contribute elevation corrections which includes wind. Just one more question, does AFCC Mk1** has shore bombardment/HA settings that allowed for height of targets? If it doesn't, the wind correction will be off for higher angles.
dunmunro
Senior Member
Posts: 4229
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

wmh829386 wrote: Tue Jan 18, 2022 6:51 pm
dunmunro wrote: Tue Jan 18, 2022 9:07 am
dunmunro wrote: Sun Jan 16, 2022 10:04 am


There's three inputs:

Gun deflection = wind input
Gun elevation
Gun range = Wind input. Gun range is a modifier to gun elevation.
From the FKC Handbook:
In ships carrying the A.F.C.C. Mark 1 the total elevation correction found by the fuze
keeping clock is added to director elevation in the fuze keeping clock and then transmitted
through the gun elevation synchronous unit direct to the guns. In later ships carrying the
A.F.C.C. Mark 1** the total deviation correction is added by follow-through magslip to director
elevation in the gun elevation synchronous unit.
In ships carrying the transit the total elevation correction found by the fuze keeping clock
is transmitted electrically to the transit which produces gun elevation and transmits it to the guns.
In ships carrying the fire control box the total elevation correction found by the fuze
keeping clock is transmitted mechanically to the fire control box where it is added to director
elevation and transmitted as gun elevation to the guns.
Thanks again. That's good information.
So only AFCC MkI** contribute elevation corrections which includes wind. Just one more question, does AFCC Mk1** has shore bombardment/HA settings that allowed for height of targets? If it doesn't, the wind correction will be off for higher angles.
The FCB also introduced wind correction. I don't have a manual for AFCC1**.
dunmunro
Senior Member
Posts: 4229
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

wmh829386 wrote: Tue Jan 18, 2022 6:44 pm 2) According to Friedman, it's not a simple FtP. Rather a feedback process more similar to rate control with the unfortunate caveat that it is subjected to the limitations of HACS assumptions (and god help you if a fictitious input have been used for wind correction)
Ships completed in 1940 had a new Gyro Rate Unit (GRU) mounted on the director, to measure horizontal and vertical angular rates directly. Although this measurement might be described as tachymetric, it could not transform the HACS into something capable of dealing with climbing or diving targets. Nor did it solve the problem of measuring target inclination. That was still fed in by the control officer.
The Gyro Rate Unit Box (GRUB) in the calculating position below decks received the two rates and the angle of presentation from the GRU, ultimately to feed data into the HACT nearby. This was still a feedback process. The assumed target ground (plan) speed was set on the GRUB. Given an angle of presentation and a target height and range, this speed implied particular vertical and horizontal rates. It was adjusted until these rates matched the observed rates, the GRU acting in effect as a feedback mechanism.
Your quote of Mk37 manual just shows the time for FC solution to converge in Automatic mode for Mk37 is typically faster tham matching rates even when looking directly at the target.

3) This is hilarious. :lol:

The mode of operation without GRU:
HACS output director sight angles and (clock=radar) range to electric height finder. So the GO adjust the speed and angle of presentation until the electric height finder stays on target. In other words, rate control without provision of climb rate.

4)According to Mk37 manual, automatic mode is more suitable for manuvering targets anyway.

5)With that in mind, I doubt he is calculating for targets that violates assumptions of HACS, a case which is amost impossible to quantify.
2) it is basically FtP because the operators are matching rates and the machine is doing the calculation just as Mk1 does the calculations in rate control the difference being that GRUB was optimized for this one process using relative rate linkages (as in HACS/FKC) rather than linear rate as in Mk1. In practise Mk33/37 could not deal with turning, climbing or diving targets either (ToF, target maneuver and computer lag times defeated accurate FC solutions) and we know this for a fact from the drone trial results and real world results

3) see 4.

4) If the target changes course/accelerates/changes altitude/the layer and/or trainer allow their sights to wander due to ship motion/etc. the Automatic Rate Control is then presented with an unsolvable problem. Real world results show that Mk37 was ineffective when firing MT ammo and applying MT fuze and DT errors to drone trial results verify this. Friedman:
...In this connection it was argued that long range fire had inherent limitations; a pilot could
always steer away while the shell was in the air. New bombsights drastically reduced the time he had
to stay on course before dropping a bomb. On that basis DNO wrote in 1942 that there was little point
in adding a tachymetric element to the HACS and FKC (actually, to replacing them)...
Ivan Getting (helped develop SCR584 and Mk56):
Between World War I and I1 this range-keeper had been modified
for antiaircraft use by adding the third dimension airplane
altitude. But the Mark I computer or range-keeper in use with
the Mark 37 director and the FD radars had all the limitations
built into the system. For example, the equipment was so large
that only one could be installed in a destroyer which usually
had three twin gun turrets. So, while the guns could in principle
engage three different targets, the overall system was limited
to one attacking plane at a time. It was necessary to insert the
estimated heading and speed of the aircraft; and, even though
the radar could provide bearing, elevation and range, the computer
arrived at the solution exponentially. If the airplane
changed course, or if the original estimates of course and speed
were in gross error, the correct solution was not available until
the airplane had released its weapons. Many of these deficiencies
of the Mark 1 range-keeper turned up when a dynamic
tester developed by Section D-2 of NDRC was made available
to the Radiation Laboratory. These tests further demonstrated
that in the interval between World War I and 11, when the modifications
had been made to adapt the range-keeper to three-dimensional
use, simplifications in the computation of the roll
of the ship resulted in substantial errors. These limitations were
not fully understood within the Navy; and, in any case, for substantive
reasons, the Bureau of Ordnance was loath to make
any changes in the combination of the FD radar, the Mark 37
director, Mark 1 computer directing the five-inch guns. These
not fully understood within the Navy; and, in any case, for substantive
reasons, the Bureau of Ordnance was loath to make
any changes in the combination of the FD radar, the Mark 37
director, Mark 1 computer directing the five-inch guns. These
equipments were in large production, all the ships at sea had
been equipped, training schools had been established and spare
parts and maintenance were available. Ships return only every
two years or so for major overhaul and the prospect of making
any serious changes in such a complicated and integral system
was more than the Bureau of Ordnance was willing to accept.
5)Pout started his analysis by making a series of estimates for the various errors that effect the accuracy of HAA fire using an unstabilized HADT. These include range errors (no radar), stabilization errors, layer and trainer errors and MT fuze timing errors, etc. He arrived at a number which roughly matched actual HACS performance at long range before radar:

Case1
First, experience in the field. An operational analysis of the performance
of ships carrying the HACS, which were generally of light cruiser size
upwards, during the early years of the war suggested that about 10000
shells were fired per kill achieved, that is, Pk = 1 in 10000. The analysis
has been related to the light cruiser situation with a future range of 6kyds
in moderate sea states, and should therefore not be too far removed,
on average, from this result.
And by definition these are maneuvering targets that were trying not to get hit, and many of which were high altitude, high speed targets. Therefore Pout greatly exaggerates the various errors to match observed kill rate (Pk) results which he states as:

ToF
16 sec = 1/10k Pk (Rp=7.6K yds and Rf=6K yds)
10sec = 1/3.2K
_6sec = 1/2K

Pout then analyses various improvements in ranging, stabilization, etc to come up with his estimates in later Cases. Given his starting point the analysis includes all targets, even those not flying straight and level, [which is also the case for Lundstrom's analysis cross referenced with 5in ammo expenditure per engagement. But we already agree on this, right?

I can understand the appeal that Mk37 must have had to the RN, as it seemed to solve so many problems, and was so well engineered that it just had to better than HACS/FKC, and BuOrd claimed it to be so...yet it wasn't because the fundamental issue centred on MT fuze errors and ToF, which allowed a target to evade predicted fire. Even after VT was introduced ToF defeated Mk37, if the target didn't cooperate.
wmh829386
Member
Posts: 139
Joined: Mon Oct 04, 2021 5:43 pm

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by wmh829386 »

dunmunro wrote: Tue Jan 18, 2022 7:12 pm
wmh829386 wrote: Tue Jan 18, 2022 6:51 pm
dunmunro wrote: Tue Jan 18, 2022 9:07 am

From the FKC Handbook:

Thanks again. That's good information.
So only AFCC MkI** contribute elevation corrections which includes wind. Just one more question, does AFCC Mk1** has shore bombardment/HA settings that allowed for height of targets? If it doesn't, the wind correction will be off for higher angles.
The FCB also introduced wind correction. I don't have a manual for AFCC1**.
It is explicitly stated that FCB just adds FKC HA elevation correction to director elevation. No correction is added. It should be expected as it is a minimal system.
dunmunro
Senior Member
Posts: 4229
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

wmh829386 wrote: Tue Jan 18, 2022 10:31 pm
dunmunro wrote: Tue Jan 18, 2022 7:12 pm
wmh829386 wrote: Tue Jan 18, 2022 6:51 pm
Thanks again. That's good information.
So only AFCC MkI** contribute elevation corrections which includes wind. Just one more question, does AFCC Mk1** has shore bombardment/HA settings that allowed for height of targets? If it doesn't, the wind correction will be off for higher angles.
The FCB also introduced wind correction. I don't have a manual for AFCC1**.
It is explicitly stated that FCB just adds FKC HA elevation correction to director elevation. No correction is added. It should be expected as it is a minimal system.
FCB accepts wind input via an associated wind dumaresque and applies it as a spot correction.
wmh829386
Member
Posts: 139
Joined: Mon Oct 04, 2021 5:43 pm

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by wmh829386 »

dunmunro wrote: Tue Jan 18, 2022 9:22 pm 2) it is basically FtP because the operators are matching rates and the machine is doing the calculation just as Mk1 does the calculations in rate control the difference being that GRUB was optimized for this one process using relative rate linkages (as in HACS/FKC) rather than linear rate as in Mk1. In practise Mk33/37 could not deal with turning, climbing or diving targets either (ToF, target maneuver and computer lag times defeated accurate FC solutions) and we know this for a fact from the drone trial results and real world results
A. Normal FtP follower takes have one input an match one pointer.

B. the deflection screen operator have two inputs to match one point on the deflection screen. The two inputs are linear to the motion of cross wire

You cannot be serious for thinking that taking two inputs that are coupled in nonlinear function that produce two rate outputs is "basically FtP".

3) see 4.

4) If the target changes course/accelerates/changes altitude/the layer and/or trainer allow their sights to wander due to ship motion/etc. the Automatic Rate Control is then presented with an unsolvable problem. Real world results show that Mk37 was ineffective when firing MT ammo and applying MT fuze and DT errors to drone trial results verify this. Friedman:
There's a reason why Mk37 is stabilised. Perhaps you are not familiar with computation. The automatic rate control of course never attempts to solve the problem of accelerating motion nor does relative rate systems. It just updates the velocity of the target for the latest observation. Mk1 is slower to update because as a mechanical system it has friction band inertia. Calling this "unsolvable problem" mischaracterise the issue.

The point is, if the target don't accelerate fast enough or frequent enough the FC will be close enough.

We know in practice, automatic mode in Mk37 is faster than rate control. We even have test data on its the probabilities for TTB in automaic mode using VT ammo. You are exaggerating to say that manuvers always defeat the FC solution of by Mk37. With gun crew with good dead time discipline, we can scale the kill probability of the test results.

The HACS will be slower and less accurate. Using the its version of rate control.

Fun fact there's a limit to acceleration to planes, so modern FC computer use linear rates too. With radar, it can update target motion in millie seconds instead of seconds. It is not important to get acceleration: it can change freely and abruptly at any moment. But velocity always changes smoothly: acceleration is limited.
5)Pout started his analysis by making a series of estimates for the various errors that effect the accuracy of HAA fire using an unstabilized HADT. These include range errors (no radar), stabilization errors, layer and trainer errors and MT fuze timing errors, etc. He arrived at a number which roughly matched actual HACS performance at long range before radar:


Case1
First, experience in the field. An operational analysis of the performance
of ships carrying the HACS, which were generally of light cruiser size
upwards, during the early years of the war suggested that about 10000
shells were fired per kill achieved, that is, Pk = 1 in 10000. The analysis
has been related to the light cruiser situation with a future range of 6kyds
in moderate sea states, and should therefore not be too far removed,
on average, from this result.
And by definition these are maneuvering targets that were trying not to get hit, and many of which were high altitude, high speed targets. Therefore Pout greatly exaggerates the various errors to match observed kill rate (Pk) results which he states as:

ToF
16 sec = 1/10k Pk (Rp=7.6K yds and Rf=6K yds)
10sec = 1/3.2K
_6sec = 1/2K

Pout then analyses various improvements in ranging, stabilization, etc to come up with his estimates in later Cases. Given his starting point the analysis includes all targets, even those not flying straight and level, [which is also the case for Lundstrom's analysis cross referenced with 5in ammo expenditure per engagement. But we already agree on this, right?

I can understand the appeal that Mk37 must have had to the RN, as it seemed to solve so many problems, and was so well engineered that it just had to better than HACS/FKC, and BuOrd claimed it to be so...yet it wasn't because the fundamental issue centred on MT fuze errors and ToF, which allowed a target to evade predicted fire. Even after VT was introduced ToF defeated Mk37, if the target didn't cooperate.
I really hate to say this again. RPK is a terrible metric.
Given his starting point the analysis includes all targets,
This should alarm anyone with statistic training. What weighting did he put in various types of targets? How he treats targets that cannot be shot down at all because of the engagement envelope?
It is even more alarming when his starting point is early war statistics, meaning for that figure, the implied target types are different from the Pacific.
Therefore Pout greatly exaggerates the various errors to match observed kill rate (Pk) results which he states as:
This is a problem. That means he cannot arrive to operational error by analysing the inherent accuracy of the system. Part of it must be due to manuvers by targets. To exaggerate the errors as means to model it, is understandable. But the relative factors of exaggeration for each error is also target specific. Worse still, that implies the time to update/reached a solution is not in the matric, but the factor of exaggeration must be a function of that time.

Let me be clear, I am not saying he makes some terrible mistakes.
I think he tried his best. But there must be a long list of details that must be put in place before trying to cross reference one "RPK" to another "RPK". Especially mapping on theoratical results for one system with empirical data of other system.

Furthermore, if GRUB carried ships did not see the improvements with VT fuse in reality, what should we make of the accuracy of his calculation?
wmh829386
Member
Posts: 139
Joined: Mon Oct 04, 2021 5:43 pm

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by wmh829386 »

dunmunro wrote: Tue Jan 18, 2022 11:23 pm
wmh829386 wrote: Tue Jan 18, 2022 10:31 pm
dunmunro wrote: Tue Jan 18, 2022 7:12 pm

The FCB also introduced wind correction. I don't have a manual for AFCC1**.
It is explicitly stated that FCB just adds FKC HA elevation correction to director elevation. No correction is added. It should be expected as it is a minimal system.
FCB accepts wind input via an associated wind dumaresque and applies it as a spot correction.
Too bad spotting correction is not added to gun elevation according to the manual. I am just understanding it literally. In AFCC1** it is explicitly stated correction is added
dunmunro
Senior Member
Posts: 4229
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

wmh829386 wrote: Wed Jan 19, 2022 12:10 am

We know in practice, automatic mode in Mk37 is faster than rate control. We even have test data on its the probabilities for TTB in automaic mode using VT ammo. You are exaggerating to say that manuvers always defeat the FC solution of by Mk37. With gun crew with good dead time discipline, we can scale the kill probability of the test results.
OK, please do.
Steve Crandell
Senior Member
Posts: 872
Joined: Wed Feb 05, 2014 7:05 pm

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by Steve Crandell »

I was just reading on the armoredcarriers.com web site about the design of the Audacious class. I found the following sentence:

"Fire control system was also improved: It was a grafting of the US Navy’s Mark 37 director with a modified Royal Navy Type 275 radar set."
dunmunro
Senior Member
Posts: 4229
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

Steve Crandell wrote: Sat Jan 22, 2022 2:36 am I was just reading on the armoredcarriers.com web site about the design of the Audacious class. I found the following sentence:

"Fire control system was also improved: It was a grafting of the US Navy’s Mark 37 director with a modified Royal Navy Type 275 radar set."
As I stated earlier, MK37 was replaced, in the Audacious class, as the primary AAFC system by MRS3 (similar to MK56). Mk37 was supplied for free at a time when the MK6 director was in short supply. According to Porteous Mk6 and GRUS/GRUDOU and/or Flyplane was superior to Mk37.
Steve Crandell
Senior Member
Posts: 872
Joined: Wed Feb 05, 2014 7:05 pm

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by Steve Crandell »

dunmunro wrote: Sat Jan 22, 2022 10:15 am As I stated earlier, MK37 was replaced, in the Audacious class, as the primary AAFC system by MRS3 (similar to MK56). Mk37 was supplied for free at a time when the MK6 director was in short supply. According to Porteous Mk6 and GRUS/GRUDOU and/or Flyplane was superior to Mk37.
I don't think you pointed out earlier the part about "Fire control system was also improved". That it was improved again later is beside the point; the USN did that also. The point is that the British chose the Mark 37 as an improvement over what they had. And please ... I just don't believe that they would saddle these brand new carriers with substandard equipment because better stuff was in short supply. These two new CVs would have had top priority for anything that was superior at the time.
dunmunro
Senior Member
Posts: 4229
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

Steve Crandell wrote: Sat Jan 22, 2022 6:10 pm
dunmunro wrote: Sat Jan 22, 2022 10:15 am As I stated earlier, MK37 was replaced, in the Audacious class, as the primary AAFC system by MRS3 (similar to MK56). Mk37 was supplied for free at a time when the MK6 director was in short supply. According to Porteous Mk6 and GRUS/GRUDOU and/or Flyplane was superior to Mk37.
I don't think you pointed out earlier the part about "Fire control system was also improved". That it was improved again later is beside the point; the USN did that also. The point is that the British chose the Mark 37 as an improvement over what they had. And please ... I just don't believe that they would saddle these brand new carriers with substandard equipment because better stuff was in short supply. These two new CVs would have had top priority for anything that was superior at the time.
Eagle was first to complete in 1951, although laid down in late 1942. When Eagle and Ark Royal were laid down it was obvious that there would be a shortage of Mk VI directors, and since the MK V director couldn't accommodate type 275 radar, if was Mk37 or nothing, if they were to complete in 1946, which was the planned year. By the time they did complete Mk37 was clearly obsolete, but being free I guess they decided to retain it rather than redesign everything and replace it when the post war UK was basically bankrupt; the actual AA duties were taken over by MRS3.

Again, I would argue that if BuOrd had conducted and published a proper and honest evaluation of Mk37 AA efficacy, that the UK could have avoided, what turned out to be a costly mistake.
Steve Crandell
Senior Member
Posts: 872
Joined: Wed Feb 05, 2014 7:05 pm

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by Steve Crandell »

dunmunro wrote: Sat Jan 22, 2022 6:37 pm
Again, I would argue that if BuOrd had conducted and published a proper and honest evaluation of Mk37 AA efficacy, that the UK could have avoided, what turned out to be a costly mistake.
And you are claiming that in 1950 the British still didn't know the actual capabilities of the Mark 37.

Why was it a costly mistake if it was "free"?

The USN still thought the Mark 37 was a worthwhile system late in the war after shooting down thousands of Japanese aircraft and not having a clue that it didn't work? They figured out the torpedo problem in 1943, but in 1945 were still installing Mark 37 on US ships. And don't tell me they were too poor to change if it was necessary. It obviously DID work, but was inherently limited by the delay from solution to target impact. If you fire enough shells, one or more are likely to get close enough. It's the same principle as when you have main battery salvos who's pattern is too tight.

That doesn't mean you don't upgrade your system when technology advances to the point where it's worthwhile. Of course, you still have the problem with an unpredictable target, and only a missile comes close to solving that problem while introducing others at the same time.
Byron Angel
Senior Member
Posts: 1376
Joined: Sun Mar 06, 2011 1:06 am

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by Byron Angel »

dunmunro wrote: Sat Jan 22, 2022 10:15 am According to Porteous Mk6 and GRUS/GRUDOU and/or Flyplane was superior to Mk37.

Interested readers might wish to access the on-line (Navweaps) copy of the document "From Fellside to Flyplane" by Roger Porteous and read for themselves what was written; see Chapter 10 - "Sea Trials in HMS Broadsword" (pg 49). These initial sea trials of Flyplane took place in 1949 - 13 years AFTER development of the Mk37 GFCS had been commenced and 10 years AFTER Mk37 series production had commenced.

If anyone can identify the passage where Mr Porteous (either Iville or Roger) stated that "Mk6" or "GRUS+GRUDOU" was superior to Mk37, please let me know; I cannot seem to locate it.

Meanwhile, for reference -

> The first prototype GRUDOU (Gyro Rate Unit Deflection Oil Unit) was tested at Frazer Battery at the end of 1942 or early 1943. After a successful series of tests, GRUDOU was approved for production and fitting to all RN warships already fitted with HACS+GRU; this production and installation effort was finally completed by the end of 1944.

> The first prototype GRUS (Gyro Rate Unit Stabilizer) was not fitted to a RN warship (HMS Implacable) for testing until 24 Sep 1944; the test was successful and a production order for 25 units was consequently issued. The GRUS+GRUDOU combo did see action in the PTO aboard HMS Implacable, but it is quite uncertain whether any other British carriers in the Pacific were fitted with GRUS (see Admiral Vian's report; "From Fellside to Flyplane", page 39).

> Per "Naval Weapons of World War Two" by NJM Campbell (pp 18-19), the latest model Mk VI director with the latest Type 275 radar and the latest NRS (Naval Reflector Sight) Mk 2G was found to have unexpected problems. According to Campbell - "The original NRS (Naval Reflector Sight) Mk 2G, known in a later version as Gyro Deflection Sight (GDS Mk 1), was intended to put nearly all trajectories through the VT fuze circle up to at least 4000yd but trials in 1944-45 indicated that the limit was about half the above. The Simple Electric Deflection Calculator (SEDC) could provide a measure of tachymetric computation to 4000-5000yd and GRU to about 3000yd but the former was not immediately available and GRU had to be fitted below the director."


Byron
dunmunro
Senior Member
Posts: 4229
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

Steve Crandell wrote: Sat Jan 22, 2022 7:42 pm
dunmunro wrote: Sat Jan 22, 2022 6:37 pm
Again, I would argue that if BuOrd had conducted and published a proper and honest evaluation of Mk37 AA efficacy, that the UK could have avoided, what turned out to be a costly mistake.
And you are claiming that in 1950 the British still didn't know the actual capabilities of the Mark 37.

Why was it a costly mistake if it was "free"?

The USN still thought the Mark 37 was a worthwhile system late in the war after shooting down thousands of Japanese aircraft and not having a clue that it didn't work? They figured out the torpedo problem in 1943, but in 1945 were still installing Mark 37 on US ships. And don't tell me they were too poor to change if it was necessary. It obviously DID work, but was inherently limited by the delay from solution to target impact. If you fire enough shells, one or more are likely to get close enough. It's the same principle as when you have main battery salvos who's pattern is too tight.

That doesn't mean you don't upgrade your system when technology advances to the point where it's worthwhile. Of course, you still have the problem with an unpredictable target, and only a missile comes close to solving that problem while introducing others at the same time.
I have given ample info from civilian scientists who plainly stated that Mk37 was inefficient and obsolete, but this is what the USN itself stated:
The post-war (USN- 1945!) Pacific Fleet lessons-learned board asserted that Mk 37 and other heavy gun fire
control systems were inefficient against fast manoeuvring aircraft such as Kamikazes. ‘The
introduction of the VT fuse was a shot in the arm to the basic system which enabled it to stagger
through the war by partially concealing its inherent weakness...’ (Friedman)
The RN ships that were given MK37 were designed around and wired for Mk37; to install something else would require a lot of expensive redesign with expensive replacement hardware at a time when the RN was undergoing a rapid contraction in personnel and funding. The RPC used in Mk37 was very different from the metadyne control systems used in RN designed FC systems. The displacement expended on the MK37 GFCS meant that there was less displacement left over for other things.

Mk37/33 didn't shoot down thousands of IJN aircraft. The vast majority of AA kills were via the close range autocannon, 5in/38 guns controlled via relative rate directors, the director slew sight, barrage fire and local control....Mk37/Mk1 computer kills were way, way down the list amd downed a few hundred aircraft at most. The USN claimed 2056 AA kills for all of WW2. Of these about 35% were attributed to 5in fire, but as we know from 1942, 5in AA kills were very rare (yet Buord claimed 60 at 252RPB!!!), and probably actually contributed about ~10-15% of total kills, and total kills were way less than 2056 because these numbers are based solely on USN kill claims. A more likely estimate is ~700 with Mk37 accounting for 70-100.

http://www.ibiblio.org/hyperwar/USN/rep ... ex.html#II

BuOrd was a deeply flawed organization and their handling of the torpedo scandal, and what should have been an AA scandal, was deeply prejudicial to the Allied cause and BuOrd was directly responsible (via the torpedo scandal) for dragging out the war in the Pacific for ~1 year longer than necessary.
Last edited by dunmunro on Sat Jan 22, 2022 11:10 pm, edited 1 time in total.
Post Reply