How close was the final battle?

[dunmunro]

Hello all,
according to KGV GAR (https://www.kbismarck.org/forum/downloa ... hp?id=4164), the 284 operator "continued to look for Bismarck at round about 25.000 yards". Therefore he could only have transmitted this range pressing his footswitch when getting a range of around 25.000 yards (most probably KGV was firing constantly at around 24.000 -

hans

No. He could not transmit a range where there was no target! The range rate was quite high (~800yds minute) and by ~0849 range would have fallen to under 24k yds.

[dunmunro]

(most probably KGV was firing constantly at around 24.000 - 25.000 yards from open fire and BS range was taken on her own fall of shot instead than on Bismarck, while corrections were done based on Rodney fall of shots. Had operator pressed it when getting intermittent "correct" decreasing ranges (as per above post supposition), no such statement would have been necessary in GAR and in its enclosure II (https://www.kbismarck.org/forum/downloa ... hp?id=4169).

We would need KGV salvo plot to confirm my above assumption, but comment about operator error in GAR and in its enclosure clearly imply that KGV was not having a correct range plot until very first reliable and continuous range of 20.500 yards was obtained, transmitted and accepted by AFCT personnel at 08:53 only. Emphasis on this 20.500 yards range implies that a large error was present in KGV range plot at T.S. before it was got.

hans

Type 284 could not range on fall of shot at ~25k yds; again there is data being received by the AFCT team (transmitting station) from multiple sources including the spotters in the DCT and if they were claiming that salvo were falling short then they would probably ignore radar ranges that conflicted with the optical spots.

[hans zurbriggen]

Hello all,

"No. He could not transmit a range where there was no target!"

Instead of underlying personal speculations with pointless screams, I would kindly suggest to post evidences that AFCT was actually fed with a different range than 25.000 yards, (25.000 is range clearly implied by KGV GAR (https://www.kbismarck.org/forum/downloa ... hp?id=4164)). Echo at 25.000 yards could have been just peak of noise (see Byron's most useful links) that confused operator, or KGV own fall of shot.

Had AFCT been fed with any different range, Gunnery Control report would have mentioned them. Instead, only ranges mentioned are 25.100 (08:48) and 20.500 (08:53), in addition to 25.000, as result of operator error. All other ranges are within R.D/F officer's report only (https://www.kbismarck.org/forum/downloa ... hp?id=4168), to which a plain comment was added, making clear that Gunnery Control did not "get full value from R.D/F ranging" . That means logically that no intermediate range (echoes from Bismarck) was communicated to / entered into AFCT. (https://www.kbismarck.org/forum/downloa ... hp?id=4169).

"The range rate was quite high (~800yds minute) and by ~0849 range would have fallen to under 24k yds."

Correct. However, as corrections were wrongly based on Rodney's salvo fall of shells and Rodney was firing much short of target (see her salvo plot), KGV possibly fired initially even longer than 25.000 yards.

"Type 284 could not range on fall of shot at ~25k yds"

50 meters high water columns might have generated intermittent echoes, wrongly 'preferred' to also intermittent Bismarck echoes, or it may have been just a noise peak on operator panel. GAR is clear: 25.000 yards was retained as Bismarck range until 08:53 by R.D/F operator.

hans

[hans zurbriggen]

Hi Byron,

"Her target echo would have been constantly changing in strength as she transitioned back and forth from an end-on aspect to a broadside aspect."

you are absolutely right. This aspect may have had an influence on the "intermittent" echo received by 284, at least over 21.000 yards. After that, possibly signal was strong enough to be detected continuously, despite change in strength, by a set considered in "first class working order" by R.D/F officer in his report.


hans

[dunmunro]

Hello all,

"No. He could not transmit a range where there was no target!"

Instead of underlying personal speculations with pointless screams, I would kindly suggest to post evidences that AFCT was actually fed with a different range than 25.000 yards, (25.000 is range clearly implied by KGV GAR (https://www.kbismarck.org/forum/downloa ... hp?id=4164)). Echo at 25.000 yards could have been just peak of noise (see Byron's most useful links) that confused operator, or KGV own fall of shot.

Had AFCT been fed with any different range, Gunnery Control report would have mentioned them. Instead, only ranges mentioned are 25.100 (08:48) and 20.500 (08:53), in addition to 25.000, as result of operator error. All other ranges are within R.D/F officer's report only (https://www.kbismarck.org/forum/downloa ... hp?id=4168), to which a plain comment was added, making clear that Gunnery Control did not "get full value from R.D/F ranging" . That means logically that no intermediate range (echoes from Bismarck) was communicated to / entered into AFCT. (https://www.kbismarck.org/forum/downloa ... hp?id=4169).

"The range rate was quite high (~800yds minute) and by ~0849 range would have fallen to under 24k yds."

Correct. However, as corrections were wrongly based on Rodney's salvo fall of shells and Rodney was firing much short of target (see her salvo plot), KGV possibly fired initially even longer than 25.000 yards.

"Type 284 could not range on fall of shot at ~25k yds"

50 meters high water columns might have generated intermittent echoes, wrongly 'preferred' to also intermittent Bismarck echoes, or it may have been just a noise peak on operator panel. GAR is clear: 25.000 yards was retained as Bismarck range until 08:53 by R.D/F operator.

hans

When we understand Type 284's capabilities and what it can and cannot do then we gain some insight into what was being reported.

KGV's GAR reports that it's Type 284 detected Rodney at 23800 yds on 26 May, and that final tuning adjustments were made after that. There's no indication that spurious ranges were ever detected with KGV's Type 284. The GAR clearly states that Type 284 ranges were obtained after the 25100 yd range and the 24600 initial range: "...Type 284 reported short..." and what the type 284 must have been reporting was the range to Bismarck, but the AFCT team must have rejected that range and subsequent type 284 ranges until the range fell under 22K yds. Even Type 284M was not capable of detecting fall of shot at ~25k yds (the limit for DoY with Type 284M3 was ~21k yds) and limit for Type 284 was about 15-16K yds; water is not highly reflective.

If the radar operator was searching at ~25k yds, then he would not be reporting any ranges, because there's nothing to range on.

[hans zurbriggen]

Hello all,

"what the type 284 must have been reporting was the range to Bismarck, but the AFCT team must have rejected that range"

This is just one possibility/supposition, no proof. Other possibility is that operator did not pass any range different from 25.000 yards to T.S. This second possibility seems to be well confirmed by GAR statement: https://www.kbismarck.org/forum/downloa ... hp?id=4164) because no mention to any AFCT personnel error is made, just to radar operator error.

"If the radar operator was searching at ~25k yds, then he would not be reporting any ranges, because there's nothing to range on."

I'm afraid this is another supposition, not backed up by any evidence. Noise and noise peaks are always present in a radar panel. If operator was thinking Bismarck was at 25.000 yards, he would not have passed other ranges to T.S. , else GAR would have said he was unsure about BS range and passed inconsistent ranges not mentioning only 25.000 yards.

the 24600 initial range: "...Type 284 reported short..." “ 284M was not capable of detecting fall of shot “

This confirms (even without need for bold, instead posting full sentence from GAR would be more significant), that KGV initially fired upper ladder (at 25.000+ ?) after first salvo (as I was saying in my last post) and that noise at 25.000 yards could well come from her own fall of shot (surely not sufficient for full blind fire but apparently enough to confuse operator with BS aspect changing so rapidly as Byron suggested). This also confirms that in first minutes they were spotting on Rodney’s fall of shot and we know, from Rodney salvo plot, that Rodney was firing much short.

Also, this confirms that both Spotter and 284 Operator reported first salvo as short, thus fall of shot was actually giving a kind of echo on radar panel of 284, please see below, my underline for clarity only).

KGV Gunnery Control_1.jpg (15.3 KiB) Viewed 114184 times

hans

[dunmunro]

the 24600 initial range: "...Type 284 reported short..." “ 284M was not capable of detecting fall of shot “

This confirms (even without need for bold, instead posting full sentence from GAR would be more significant), that KGV initially fired upper ladder (at 25.000+ ?) after first salvo (as I was saying in my last post) and that noise at 25.000 yards could well come from her own fall of shot (surely not sufficient for full blind fire but apparently enough to confuse operator with BS aspect changing so rapidly as Byron suggested). This also confirms that in first minutes they were spotting on Rodney’s fall of shot and we know, from Rodney salvo plot, that Rodney was firing much short.

Also, this confirms that both Spotter and 284 Operator reported first salvo as short, thus fall of shot was actually giving a kind of echo on radar panel of 284, please see below, my underline for clarity only).


KGV Gunnery Control_1.jpg


hans

Typical A and B salvos would be plus and minus 200yds from plot range (as at 0853) but the time of flight would be ~40 seconds for the first salvos and an error in the plot's range rate (plus ballistic factors) would give a range for Bismarck that might appear be a salvo falling short, but was a brief echo of Bismarck itself. A report of a salvo falling short from radar and optically doesn't mean that both agree on how far short the salvo was as the optical spot might have ~1000 yds short (as per Rodney's salvos) but the radar range might have been ~500 yds short (Bismarck's actual range along with the A or B salvo of the 14in salvos) which was the correct range but seemed short due to an incorrect range rate on the AFCT plot.
Experience with Type 284 salvo spotting was very limited in May 1941 and the maximum ability of Type 284 to range on 14in salvos was an unknown at that time; we now know that Type 284 could not produce a radar echo from a salvo at that range.

[hans zurbriggen]

Hello all,

"we now know that Type 284 could not produce a radar echo from a salvo at that range"

This is not what is written in GAR and usage of this aftermath info is supposition. Please let's try to stick to evidences: 284 radar operator reported fall of shot of first salvo as short, thus fall of shots was generating an echo (or noise was interpreted as echo, or Bismarck was misidentified as fall of shot...).

Despite lack of experience, 284 operator looked for and reported fall of shot and it was in agreement with Spotter observations. They both reported "short". Therefore corrected gun range after spotting was longer than predicted range at AFCT with first range rate (approximate one, most probably). Please see (https://www.kbismarck.org/forum/downloa ... hp?id=4180)

hans

[hans zurbriggen]

Hello all,
this is my two cents opinion (I don't pretend to be right) of what might have happened at (e.g.) 08:50 on KGV 284 panel (based on analysis of Rodney's GAR and salvo plot, KGV GAR and its enclosures and estimated Bismarck course/range rate). Thanks to Byron for providing link I used for example diagram (https://www.ibiblio.org/hyperwar/USN/re ... 08-05.html) below. My input in red and green and distances not in correct scale.

panel.jpg (29.3 KiB) Viewed 114135 times

Operator mistook noise and/or KGV own fall of shots for a Bismarck echo (around 25.000 yards), while enemy was already much closer (around 23.000 @ 08:50) and Rodney's salvos were falling at 22.000 yards (assuming KGV and Rodney distance from enemy was almost same, as already discussed). Spotter had continued spotting on Rodney's salvo (short), thus KGV continued to fire to around 25.000, increasing gun range despite rate was actually closing.

We don't know which ranges were passed by operator to T.S. (only 25.000 ? All of them from 21.100 to 25.000 ? Some of them ?) but what is evident (not, as it was above, my poor speculation anymore) from GAR (https://www.kbismarck.org/forum/downloa ... hp?id=4164) and Enclosure 3 Section II (https://www.kbismarck.org/forum/downloa ... hp?id=4169) is that AFCT was not profitably tuned to deceasing R.D/F echoes ranges below 25.000 (had they been communicated to T.S. or not) until later (20.500 @ 08:53).


hans

[dunmunro]

Hello all,

"we now know that Type 284 could not produce a radar echo from a salvo at that range"

This is not what is written in GAR and usage of this aftermath info is supposition. Please let's try to stick to evidences: 284 radar operator reported fall of shot of first salvo as short, thus fall of shots was generating an echo (or noise was interpreted as echo, or Bismarck was misidentified as fall of shot...).

Despite lack of experience, 284 operator looked for and reported fall of shot and it was in agreement with Spotter observations. They both reported "short". Therefore corrected gun range after spotting was longer than predicted range at AFCT with first range rate (approximate one, most probably). Please see (https://www.kbismarck.org/forum/downloa ... hp?id=4180)

hans

We know that Type 284 could not range on salvos at that range! Even Type 284M3 with 6 times the power output couldn't range on salvos at that range. To spot on a salvo, both the target (Bismarck) and the salvo have to be visible on the radar display tube. However, a single range from Bismarck might have been misinterpreted by the AFCT team, as a spot if it coincided with the expected fall of shot.

[dunmunro]

Hello all,
this is my two cents opinion (I don't pretend to be right) of what might have happened at (e.g.) 08:50 on KGV 284 panel (based on analysis of Rodney's GAR and salvo plot, KGV GAR and its enclosures and estimated Bismarck course/range rate). Thanks to Byron for providing link I used for example diagram (https://www.ibiblio.org/hyperwar/USN/re ... 08-05.html) below. My input in red and green and distances not in correct scale.


panel.jpg


Operator mistook noise and/or KGV own fall of shots for a Bismarck echo (around 25.000 yards), while enemy was already much closer (around 23.000 @ 08:50) and Rodney's salvos were falling at 22.000 yards (assuming KGV and Rodney distance from enemy was almost same, as already discussed). Spotter had continued spotting on Rodney's salvo (short), thus KGV continued to fire to around 25.000, increasing gun range despite rate was actually closing.

We don't know which ranges were passed by operator to T.S. (only 25.000 ? All of them from 21.100 to 25.000 ? Some of them ?) but what is evident (not, as it was above, my poor speculation anymore) from GAR (https://www.kbismarck.org/forum/downloa ... hp?id=4164) and Enclosure 3 Section II (https://www.kbismarck.org/forum/downloa ... hp?id=4169) is that AFCT was not profitably tuned to deceasing R.D/F echoes ranges below 25.000 (had they been communicated to T.S. or not) until later (20.500 @ 08:53).


hans

That example is from a USN radar! It is NOT applicable to RN Type 284/5 radars because they have a much lower noise display. One of the problems with the USN Mk3 and, especially, Mk4 radars was excessive noise at low angles of sight, and this rendered Mk4 radar almost useless when the target was under ~10 degrees angle of sight. To overcome this, the Mk4 radar had to be limited to 10deg elevation when tracking surface targets.

I have read through much data on Type 284/5 radars and spurious (false) ranges were not an issue and there are no reports of this during development or actual use of service radars. The example of Hood's ranging on KGV is a good example; all the ranges reported, even when the echo were intermittent were accurate.

This video shows real world examples of a Type 284M display, and the Type 284 display was very similar:

https://youtu.be/t-fJ255jMH4?list=TLPQM ... uNxh_GAXjA

[Byron Angel]

Go here - https://www.smecc.org/mcmahon%27s_radars!.htm

FIRE-CONTROL RADARS
Earlier work with the XAF showed great promise for gunfire control ("fire control") radars. They could work equally well in any weather and any time of day or night. Ranging accuracy could be almost exact, compared to the well-known inaccuracies of optical ranging; the first salvo of shells could bracket the enemy ship, rather than being "walked in".

NRL developed an accurate "range only" radar set, the CXAS-1, which became the FA, or Mark-1. The 500 MHz, 2 KW transmitter, using old-style vacuum tubes, was inadequate. Work was begun on the more powerful set, under the name FB, or Mark-2. Then the news of the wondrous Magnetron hit, with stories of 40 KW output at 700 MHz. FB was immediately dropped, and development started on the FC or Mark-3, magnetron-powered gun-laying radar. The prototype was installed on the U.S.S. Philadelphia in October, 1941, with great success. Immediate orders were placed for 125 production units, which were installed on capital warships.

Use of the F-series radar for anti-aircraft fire control was another obvious opportunity. What was most-needed was antenna lobing in the vertical direction for accurate elevation information. Development of the FD, or Mark-4, anti-aircraft radar was conducted along with the FC, and was tested aboard the destroyer U.S.S. Roe in September, 1941. Full production started by the end of 1941, and 375 units were delivered to the fleet. These sets saw heavy combat duty through the end of the war. (Mark-4 is discussed in some detail later in this article.)

- - - - -

Mk 3 (FC), with the 3' x 12' "snowplow" antenna and lateral lobe-switching was the radar employed for control of BB main battery and other surface gunfire roles.

Mk 4 (FD), with a pair of stacked 3' x 6' antennae for vertical lobe switching to aid in height-finding was a follow-on development employed for control of all dual purpose gun batteries (DD up to BB/CV classes). See the following books by Crenshaw: "South Pacific Destroyer" and "The Battle of Tassafaronga". Interestingly enough, Crenshaw (gunnery officer aboard DD401 USS MAURY) fails to mention any "grass" problems in connection with Mk 4 FD (Go here - http://www.navsource.org/archives/05/pix2/0540109.jpg - to note the unusually LOW mounting of the antennae on the face of the director; later FD-equipped DDs had the antennae mounted on framework well above the roof of the director).

- - - - -

Here is the section of the radar operator's manual for Mk4 FD radars - https://maritime.org/doc/radar/part4.php#pgMK3MK4-1 .

I was unable to locate any mention of a serious performance defect.

- - - - -

Here is the NavSource write-up on Mk4 FD - http://www.navsource.org/archives/01/57o.htm

"Operation of Mark 4 (“FD”) and Mark 12 radars.
The Mk.4 radar was used for control of heavy A.A. batteries.
It was effective against both air and surface targets but had certain limitations in both instances. Range accuracy of the “FD” was very good and constant for all ranges. Bearing accuracy was reasonably good but not as good as optical bearing (Same for elevation, except for targets between 50 and 1300 feet altitude which were within a range of 8000 yards.) Range discrimination was fairly good, being about 200-300 yds. between targets at approximately the same bearing. Bearing discrimination was not so good for closely grouped targets at approximately the same ranges. If two targets were at the same range and within about 15 degrees of the same bearing or less, the trainer could train to a point between the targets.
Mark 4 radar was used in Mark 37 gun directors on battleships. This radar was the oldest type of radar used aboard capital ships at the time of writing (1944) and for that reason lacked many of the refinements of other radars developed largely during the war. It was more difficult to operate, more frequently subject to casualties. However, with a great deal of training for crews that operated and serviced it, it was a powerful weapon and had accounted for many Jap planes both at night and day. It was equally effective against light surface forces.
The Mk.12 soon replaced the Mk.4 and had the same general characteristics, was better engineered and easier to operate due to improved methods of indication and also easier to service.
All indicating units of the Mk.4 radar were located in the director. Transmitter and other units were usually located within 100 feet of the director in a space for one “engineer” of the equipment, just as important as a good operator for optimum performance.
The radar operator in the director was captain of his four man team. He selected the target by his control and indicator and determined range by his range unit. The target then appeared for the trainer and pointer, two other members of the team, the fourth being the “engineer”. The trainer and pointer each had scopes with “matched pips” indication. By this method, the trainer trained the director to left or to right to maintain both pips the same size. When they were the same size, the director was on target in train. The same applies to the pointer for elevation.
The utmost coordination between radar operator, director trainer and pointer was absolutely necessary for optimum performance of that radar. It was the paramount duty of the director officer to see that this coordination had been attained.
The MK.4 radar could detect large planes as far as 80,000 yds., small planes at 50,00 yds. These ranges were frequently exceeded.
The range accuracy was excellent, being constant for all ranges and errors normally did not exceed plus or minus 50-100 yds. Bearing and elevation accuracy were reasonable good and an experienced crew could stay on target without deviating more than plus or minus 1- to 2 degrees from optical bearing and elevation. At the time (1944) radar ranging was far superior to optical ranging but optical training and pointing superior to radar training and pointing.
When visibility permitted, radar ranges were always used in conjunction with optical training and pointing for optimum performance."

- - - - -

There may well have been a problem, but it appears that the problem was either resolved or found to be insufficiently discomfiting to warrant much excitement. I'd be interested to read your source documentation on this.

[hans zurbriggen]

Hello all,
I feel everything has been well documented. I won't answer anymore to screams (repeated annoying "!"), speculations (sold as truth) and hindsights ("we now know...") that have nothing to do with what is clearly written in GAR and Enclosures re. actual KGV personnel errors/lessons learned.

By now, everyone should be able to make up his mind and evaluate what could have happened on KGV in first minutes fire, even missing KGV salvo plot.

hans

[dunmunro]

I was unable to locate any mention of a serious performance defect.

This is from the Mk3/4 operator's manual:

Below 12 degrees of elevation, the ED cannot be relied upon to give accurate position angles. With surface targets we know what the position angle is, and so are not concerned about the inability of the ED to give an accurate position angle...

https://maritime.org/doc/radar/part4.php#pgMK3MK4-1 (PAGE 4-9) (ED = elevation display)

and

Mark 4 is used on the all-purpose directors Mk. 33 and Mk. 37 with 5-inch guns. It furnishes elevation, bearing, and range, though at elevation angles below 10° the elevation angle is likely to be in error. Set is useful in getting a solution into the computer before the target gets into the range of visibility. Mark 12 will be a higher-powered set which will replace the Mark 4 in the Mark 37 director (square-backed type).

https://www.history.navy.mil/research/l ... ation.html (page 32)

and from the url provided by you:

(FC = Mk3 and FD = Mk4)

FD’s only real problem was elevation inaccuracy at with low flying targets such as torpedo planes, due to radar reflections from the surface of the ocean. To correct this, the FM (Mark-12), was developed, with horizontal lobing only. It was co-mounted with the Mark-22, a 10,000 MHz elevation-finding radar with a nodding segment-shaped antenna. This combination was excellent, and 700 units were produced starting in 1943.

https://www.smecc.org/mcmahon%27s_radars!.htm

[dunmunro]

Hello all,
I feel everything has been well documented. I won't answer anymore to screams (repeated annoying "!"), speculations (sold as truth) and hindsights ("we now know...") that have nothing to do with what is clearly written in GAR and Enclosures re. actual KGV personnel errors/lessons learned.

By now, everyone should be able to make up his mind and evaluate what could have happened on KGV in first minutes fire, even missing KGV salvo plot.

hans

You are making things up, that don't correspond to the known limitations of Type 284 radar.