USS Washington radars

[Dave Saxton]

With all the talk about the USS Washington's radars, it might be a good idea to know what the Washington was equipped with, and when.

During 1941 after comissioning it was not equipped with any radar, until it may have received a CXAM metric air warning radar very late in 1941. The CXAM operated on a wave length of 150cm and used a large square mattress stepped off the Washington's foremast. The Washington retained this antenna until at least 1946. CXAM became the SK with the addition of a PPI indicator.

In spring 1942 when the Washington operated with the British Home Fleet it was equipped with two sets of FC (Mk3) and four sets of FD (Mk4). The FC sets used the small square antennas mouted directly to the main fire control directers on the foretop and aft. The FD's or MK4's were mounted to the Flak directors, port, starboard, aft, and on the conning tower. The aft mounting was extended higher by a tripod extension. The FD's used two square shaped but curved antennas mounted on top of each other to facilitate lobe switching on the vertical as well as the horizontal axis. Range accuracy was 0.1% of the range, plus or minus 40 yards. Bearing/elevation accuracy was within 0.2*. Range to a medium bomber flying at high altitude was 40,000 yards. Range of the 40cm radars to surface ships was 27,000 -28,000 yards to a BB and 16,000- 18,000 yards to a DD.

The Washington was also equipped with an SG search radar. The SG antenna was mounted on a small platform in front of the forward tower. This created a blind spot aft of some 80*. This was one reason that Washington had to delay opening fire on Kirishima, because the South Dakota was operating in the SG's blind spot and the Washington had lost track of the South Dakotas relative location. There was some concern that the large radar contact the SG had tracked for several minutes may have been the SD. It wasn't until the Kirishima identified itself as the enemy by switching on its search lights and opening fire that it was known that the radar contact wasn't the South Dakota.

The Washington retained these radars into 1943, but the short antennas for the Mk3's were replaced with the long Mk3 antennas by mid or late 1943.

In Feb, 1944, when the Washington collided with the Alabama, it was still equipped with MK3 FC radars.

In April 1944 it emerged from Bremerton repair yard with Mk8 radars having replaced the Mk3's on both main fire control directors.

During 1945, the aft Mk4 was upgraded to MK22 (33cm) specs, with Mk12 owls ears also added. There was an additional SC radar added to the head of the main mast by the summer of 1945. It appears that the SO radome has also been added to the head of the foremast by this time as well.

[Karl Heidenreich]

Dave,

Two questions here:

1. If the previous arragement was for Washingotn´s which was the one for the newer South Dakota during the November 14-15 engagement at Guadalcanal?

2. Which was the reason of Washington´s and South Dak´s openning barrage for failing to hit Hashimoto´s vessels?

Best regards,

[Dave Saxton]

The South Dakota had bassically the same setup. The South Dakota's Mk3's seem to have always used the "long antennas" though. These longer antennas would have provided improved bearing resolution compared to the "short antennas".

As to why they failed to score direct hits, there are at least three possible factors.

1) Bad Luck. Most accounts indicate that, the Washington's shooting in particular, wasn't really that bad. It was obtaining straddles and thats really about as good as you can do. It becomes largely a matter of luck after that.

2) Minor firing solution or MPI errors. I recall that years ago George Elder had found evidence that there were bugs in the new American fire control computors that needed to be worked out. As I recall there was a tendency to over shoot the target. This could be corrected through careful spotting and this may be the reason the USN seemed to place a lot of emphasis on spotting and correcting the fall of shot.

3) Insufficient range resolution to correct minor MPI errors. The range resolution of the 40cm FC radars was 400 yards. Near misses would probably appear as hitting the target on the radar scopes, so that no correction would appear to be needed. Indeed Capt Gatch mistakenly assumed that the SD was obtaining several direct hits based on the radar observations.

The range was probably near the maximum to small warships (16k reliable range to DDs) for the MK3, so failing to hold or track the targets (particularly if the target is being observed on a fine range indicator ) was to be expected as Hashimoto opened the range.

[tommy303]

...or all of the above. An old addage holds, 'good gunnery gives straddles, but only God gives hits.' As quaint as that may seem, there is an element of truth. A larger vessel such as a battleship might well get hit by a straddling salvo simply because it occupies a very large horizontal and vertical space, while a destroyer is much smaller both in length and height above the water. The situation is not unlike a using a shotgun load for pheasant or turkey, which are large birds, on a dove which is quite a bit smaller. Turkey or pheasant loads have fewer but relatively large shot and produce a pattern dense enough for you to hit if your aim is good. The same load at the same range on a smaller dove, even with perfect aim, may not score a hit at all. The smaller bird may simply be able to fly between the shot in the pattern unharmed.

Moving the MPI through observation of fall of shot was also highly important in any gunnery exercise where salvos are fired. This keeps the target in the middle of the pattern where it is most likely to be hit by at least one round. If one cannot accurately assess the MPI, one may be getting straddles but no hits as the target may lie in the fringes of the pattern. As Dave points out, the resolution of the sets in use was such that near misses could easily be mistaken for hits if one did not have a good visual spot and had to rely completely on radar.

[Karl Heidenreich]

What we are talking is that, even with RDFC in late 1942, there is no clear shooting superiority? On the other hand the Japanese ships did fire, on the same circumstances to the US destroyers (also small targets) and not only straddled but did hit and sunk them in a reduced amount of time.

[Bgile]

Which US Destroyer was hit and sunk by Kirishima's 14" guns?

How many hits did the IJN cruisers achieve on South Dakota? IIRC very few, and an "easy" target.

Jesse Oldendorf had West Virginia, Tennessee, California, Pennsylvania, Mississippi, and Maryland at Suriago strait. Which ones were able to fire effectively at Yamashiro, and why?

[Dave Saxton]

What we are talking is that, even with RDFC in late 1942, there is no clear shooting superiority? .......

The superiority probably wasn't as pronounced as has been reported on the internet. Most navy's that possessed radar technology tended to use it in combination with the optical equipment, unless conditions forced them to use radar exculsively. The greatest weakness with the optics in most cases was the optical range finders. Radar could provide range to target measurement that was far more accurate compared to what optical rangefinders could provide. At best, and this was not the norm, optical rangefinders provided a range to target accuracy of about 1% of the range. In many cases optics did not come close to that performance. By contrast radar, such as the Washington's Mk3 and Mk4 for example, provided a range accuracy that was 0.1% of the range +/- 40 yards.

Although the range accuracy of radar allowed the gunners to more quickly put the MPI on target and hopefully keep it there, it doesn't change the hit % per salvo, per range, assuming the MPI is correctly placed, by whatever method. Nonetheless, I have found that when conditions forced the Germans to rely more fully on radar their shooting was more accurate. The Hipper's radar reliant shooting in late 1942 was deadly, even at ranges that were more than 50% of it's 8" guns' maximum range.

[Karl Heidenreich]

Bgile:

Which US Destroyer was hit and sunk by Kirishima's 14" guns?

How many hits did the IJN cruisers achieve on South Dakota? IIRC very few, and an "easy" target.

Jesse Oldendorf had West Virginia, Tennessee, California, Pennsylvania, Mississippi, and Maryland at Suriago strait. Which ones were able to fire effectively at Yamashiro, and why?

I´m refering to the Japanese ships that fire and hit Preston, Walke, Gwin and Benham. Not South Dakota nor Washington.

[Karl Heidenreich]

Bgile:

Jesse Oldendorf had West Virginia, Tennessee, California, Pennsylvania, Mississippi, and Maryland at Suriago strait. Which ones were able to fire effectively at Yamashiro, and why?

Let´s not mix things here, please. We are refering to the Washington radars and the scenario at November 14-15 at Guadalacanal. It´s obvious that two years later (which is an eternity in war) the allies will have develop more accurate fire control systems. We can refer to them later, but now it´s Washington and South Dak at Guadalcanal 1942.

[Bgile]

What we are talking is that, even with RDFC in late 1942, there is no clear shooting superiority? On the other hand the Japanese ships did fire, on the same circumstances to the US destroyers (also small targets) and not only straddled but did hit and sunk them in a reduced amount of time.

Absolutely there was no clear superiority due to radar. The mk3 wasn't that capable and the situation was too confusing ... there were radar contacts all over the place and the US ships had little experience with night combat, unlike the IJN. It didn't go all one way though, and they were somewhat lucky they weren't hit more often. From Mike Swain's piece on Bob Henneman's site (begin quote):

At 2252 Lee gave the executive order for a wheel to the west, and Walke led the column around. Eight minutes later, as Washington completed her turn, she picked up a radar contact just under 10 miles to the north-northwest.

Lee held his fire while his flagship searched for more targets; he was sure they must be out there, as this first contact did not indicate the size of the force reported by Trout. By 2317, however, no other radar contacts had been made, and both battleships had Sendai fixed in the optical sights of their main battery directors; Lee gave the order to open fire, with the range to Sendai a little over 6 miles.

Washington's first 16-inch salvo was a straddle, as was that of her 5-inch secondary battery. South Dakota's 16-inch shells landed all around Shikinami, and the Americans were sure they had hit and sunk her.

Hashimoto did not hesitate: he ordered his flagship's skipper to open the range - fast! Sendai heeled over in a hard port turn as the engineers spun their throttle wheels to bring the cruiser up to full speed; Washington's second salvo landed exactly where Sendai would have been had she maintained her southerly course.

As soon as she saw her flagship put her whell hard over, Shikinami did likewise, turning inside the cruiser just as South Dakota's second salvo of seven shells flung huge columns of dirty water upwards only 100 metres off her starboard bow.

The size of the shell splashes prompted Hashimoto to revise his contact report, and signalled Kondo that the two cruisers reported earlier were "possible battleships".
(end quote)

Then a bit later in the engagement (begin quote):

Ayanami and Uranami had done well, but they had not had it all their own way. The American flagship eventually ranged on them with her secondary batteries, and along Washington's starboard side the five twin 5-inch mounts began pouring out a steady stream of fire at the two elusive destroyers.

The radar-controlled guns soon began hitting, and fires broke out in both Japanese ships. At 2330 they launched a Parthian salvo of torpedoes, then turned away to the northeast. Ayanami was worst hit, having taken more than twenty 5-inch shells above and below the waterline. She gradually slowed to a halt as her machinery spaces were flooded, and Uranami stood by, ready to take off her crew.

(end quote)

I sure don't argue that US radar was decisive (obviously it wasn't) in this confusing night engagement.

[Brad Fischer]

Dave your dates are a bit off here. Washington had her first Mk 8 install on Spot II in July 1943. She lagged the rest of the fast battleline by several months. Here is the install times for the rest:

BB57- 2/43 & 8/43
BB58- 9/42 & 10/43
BB59- 1/43 & 8/43
BB60- 11/42 & 8/43

The Iowas were all delivered with the Mark 8 mod 1s installed on both directors. Note the second date includes the second installation (if the ship didn't have two from the original install date) as well as the upgrade to the Mark 8 Mod 1. I don't have access to all of my files as they're packed away in aticiaption of moving so I don't have North Carolina's installation dates on hand.

Brad Fischer

[Dave Saxton]

Hi Brad,

By Spot-II do you mean the aft position? I really couldn't tell for certain about the aft position from photos. The foretop position still has a Mk3 in Feb 44 without question.

[Brad Fischer]

Yes, Spot I is the Fwd MB director and Spot II is the aft director. Yes you are correct, Washington didn't have a yard period with sufficient time to install the Mark 8 in Spot I until April or May 1944 IIRC. She was the last of the 27kt BBs to get a full compliment of Mark 8s.

Brad Fischer

[USS ALASKA]

In spring 1942 when the Washington operated with the British Home Fleet it was equipped with two sets of FC (Mk3) and four sets of FD (Mk4).

Question sir – do you know if any official, or unofficial, side-by-side comparisons were done with the Royal Navy radar equipments while she was based with Home Fleet? Would be curious to know what each nationality thought about the other’s set-up and results. And no, not trying to start a RN / USN fight…

[Byron Angel]

Greetings, gentlemen - newbie here.

Mk3/Mk4 fire control radar had very good range discrimination, as has been pointed out by other posters. However, bearing discrimination was not completely suitable for truly accurate full blind fire. The most accurate fire results were achieved using radar ranging with target bearing maintained by optical means. The typical engagement sequence was as follows:

(a) target detected and plotted by surface search radar.

(b) fire control radar/gun director coached onto correct bearing to acquire target.

(c) target optically detected by range-finder operator.

It was possible to conduct blind fire (radar control in both range and bearing), but the fire effect was considerably reduced due to unavoidable lateral deviation of salvoes.

Another aspect of radar controlled gunfire in this historical timeframe was the difficulty in maintaining a good lock on the target after fire was opened. In order to spot fall of shot by radar, the operator to set his system into a "range gate" mode. This setting restricted the display of radar returns on the screen to only those originating from a zone of about +/- 500 yards about the target pip in range. Once fire was opened, the target pip could quite often be obscured or even lost within the returns from shell splashes. This was an especially common problem in the case of 6/47 or 5/38 batteries in rapid fire. A close reading of contemporary action reports suggests that it was a practice of ships so armed to fire in rapid mode for a minute or so, then cease fire in order to re-acquire the target. In many such cases the radar display would show no target pip after fire had been ceased, creating the impression that the target had been sunk when in fact evasive maneuver by the target vessel (usually making smoke as well) had simply caused it to run beyond the limited coverage of the radar's range gate setting.

As to George Elder's comments about perceived technical "bugs" in US fire control computers, I offer a rather more prosaic explanation. When spotting fall of shot by radar, it was quite possible for the radar returns of short shell splashes to block out the returns of overs. With his display showing splashes short of target and none over, the radar operator could easily be misled into the belief that the ship was firing short and that an "up" correction was necessary. Late war gunnery manuals promoted the use of laddering fire in half-pattern increments, which I suspect was implemented to resolve this problem.

While wartime reports were dramatically over-optimistic about the effectiveness of radar-controlled night gunnery, it simply cannot be denied that it conferred upon the USN an important advantage to which the IJN had no effective counter.