Pearl Harbor with different priorities

Discussions on alternate history, including events up to 20 years before today. Hosted by Terry Duncan.
Post Reply
alecsandros
Member
Posts: 298
Joined: 23 Jun 2010, 09:37

Re: Pearl Harbor with different priorities

#331

Post by alecsandros » 18 Jan 2017, 09:50

glenn239 wrote: Let's try this again. Here's the scouting plan at Midway,

https://www.google.ca/search?q=nagumo+s ... F7tydGM%3A

See how it's to 300nm with 60nm doglegs? That's what the B5N2's did during the battle, and they had plenty of range to do it.
Well, my impression is that in this drawing, the Mobile Fleet is moving from west to east. If the scouting duration is 4 hours, then the Mobile Fleet isn't standing still for 4 hours waiting for them - it's moving at some speed towards the east. What speed ? I don't know, let's say 20kts, or 36km/h.
That means space traveled on water in 4 hours = 36 x 4 = 144 km.

I see the 2 Kates sent on patrol are sent to the south, with search direction to the north. That could mean they were helped by the movement of the MObile FLeet, which was somewhat approaching them, and shortening the return leg of their journey.

In this line of thoughts, check the northern-most floatplane, which was sent to scout for only 150nm. His search direction apparently puts him "behind" the movemetn of the Mobil Fleet, thus requiring more time (and thus space traveled) to get back to the carriers.

---

Nonetheless, scouting does appear to have been a big weakness of Japanese carrier operations...

alecsandros
Member
Posts: 298
Joined: 23 Jun 2010, 09:37

Re: Pearl Harbor with different priorities

#332

Post by alecsandros » 18 Jan 2017, 13:02

Getting back to the original thread,

I am working on the PH fuel tanks map. I will be posting the details in a few days.

Best,


glenn239
Member
Posts: 5862
Joined: 29 Apr 2005, 02:20
Location: Ontario, Canada

Re: Pearl Harbor with different priorities

#333

Post by glenn239 » 18 Jan 2017, 20:32

alecsandros wrote:
I see the 2 Kates sent on patrol are sent to the south, with search direction to the north. That could mean they were helped by the movement of the MObile FLeet, which was somewhat approaching them, and shortening the return leg of their journey.

The 300/60nm search pattern for the Kates was ordered by 1st Air Fleet HQ on June 2nd. The next day, June 3rd, HQ issued this order for fleet movements,

For three hours and 30 minutes following the first wave's take-off, the fleet will proceed on course 135 degrees, speed, 24 knots. Thereafter, if the prevailing winds are from the east, course will be 45 degrees, speed 20; if west winds prevail, course will be 270 degrees, speed, 20 knots.

The Akagi Kate was flying south, doglegging left, then back towards its launch point. Nagumo's intention if the wind was coming from the east was to sail 135 degrees for 3.5 hrs, then turn 45 degrees (north east) and run at 20kt. The Akagi Search aircraft would presumably break for the expected location of the carriers after about 150 miles flying north into its return route. Call it 150 miles at course 350 then altering to course about 25 degrees to catch Nagumo. About 650nm total. Then, another 120nm (or so) because the Akagi search aircraft had to wait over the fleet before landing on Hiryu after 11am, for a total trip of about 770nm.
In this line of thoughts, check the northern-most floatplane, which was sent to scout for only 150nm. His search direction apparently puts him "behind" the movemetn of the Mobil Fleet, thus requiring more time (and thus space traveled) to get back to the carriers.
The shortened route for the last search line was because a short ranged seaplane was flying that mission. It only had about half the range of the other scouts.

Also, don't forget that all scout planes were expected to 'work' any contact discovered for over an hour. So, Tone 4 radioed the fleet at 0834 "I am homeward bound". This was after adding an hour to its flight time to look at the discovered contact. Tone then orders (8:55 and 9:07am) Tone 4 to not return and maintain contact. Tone 4 does so until 0930am, then radios it's fuel supply is low and it is returning. So Tone 4's scout added 2 full hours flight time to the scheduled mission. This reserve was built in for all the scouts - had Akagi's search aircraft spotted US carriers, it too would have had to work the contact for up to 2 hours.
Nonetheless, scouting does appear to have been a big weakness of Japanese carrier operations...
By the choice of the staff of the 1st Air Fleet itself, not because any higher HQ, doctrine, or equipment issue prevented the adaptation of better tactics.

alecsandros
Member
Posts: 298
Joined: 23 Jun 2010, 09:37

Re: Pearl Harbor with different priorities

#334

Post by alecsandros » 18 Jan 2017, 22:04

glenn239 wrote: For three hours and 30 minutes following the first wave's take-off, the fleet will proceed on course 135 degrees, speed, 24 knots. Thereafter, if the prevailing winds are from the east, course will be 45 degrees, speed 20; if west winds prevail, course will be 270 degrees, speed, 20 knots.
Very good point.
Nagumo was able to do that because he didn't have other aircraft in the air.
At Hawaii he did - 2 full strike waves - that would have precedence over any scouts sent anywhere. Thus, he couldn't manouvre to "help" by shortening the return dogleg of the scouts.
Then, another 120nm (or so) because the Akagi search aircraft had to wait over the fleet before landing on Hiryu after 11am, for a total trip of about 770nm.
Fact is the return leg was 230nm or so...

glenn239
Member
Posts: 5862
Joined: 29 Apr 2005, 02:20
Location: Ontario, Canada

Re: Pearl Harbor with different priorities

#335

Post by glenn239 » 18 Jan 2017, 22:49

alecsandros wrote: Very good point.
Nagumo was able to do that because he didn't have other aircraft in the air.
At Hawaii he did - 2 full strike waves - that would have precedence over any scouts sent anywhere. Thus, he couldn't manouvre to "help" by shortening the return dogleg of the scouts.
There was nothing preventing a search mission to 300nm. Nagumo simply chose not to conduct one and his command had chosen not to train for it.
Fact is the return leg was 230nm or so...
The search pattern on the return leg had to follow the pattern, not the most direct course back to the ship. This, until it overlapped with the line of sight on the leg taken on way out. Then the plane could break off to the northeast for landing. So no, more than 230nm on the return, plus an hours loiter time over the fleet. The range of the plane was over 1,000nm - the rest was built-in margin of error against bad navigation.

alecsandros
Member
Posts: 298
Joined: 23 Jun 2010, 09:37

Re: Pearl Harbor with different priorities

#336

Post by alecsandros » 19 Jan 2017, 07:57

Alternatively, Nagumo could have brought 1 seaplane tender with him, and assign scouting to that ship.
He put to much emphasis on the perfect surprise...

alecsandros
Member
Posts: 298
Joined: 23 Jun 2010, 09:37

Re: Pearl Harbor with different priorities

#337

Post by alecsandros » 19 Jan 2017, 18:35

First,
I'd like to add 2 pages from the transcripts of the Congressional Hearings, volume 2:
Attachments
PH fuel problems.PNG
PH fuel problems.PNG (257.2 KiB) Viewed 398 times
fleet back to west coast.PNG
fleet back to west coast.PNG (265.51 KiB) Viewed 398 times

alecsandros
Member
Posts: 298
Joined: 23 Jun 2010, 09:37

Re: Pearl Harbor with different priorities

#338

Post by alecsandros » 19 Jan 2017, 18:56

2 more small paragraphs concerning situation of fuel at the start of the war, and consumption of reserves in the first 6 months:
Attachments
PH full of fuel.PNG
PH full of fuel.PNG (260.8 KiB) Viewed 395 times

alecsandros
Member
Posts: 298
Joined: 23 Jun 2010, 09:37

Re: Pearl Harbor with different priorities

#339

Post by alecsandros » 19 Jan 2017, 18:57

.
Attachments
PH full of fuel 2.PNG
PH full of fuel 2.PNG (22.91 KiB) Viewed 395 times

glenn239
Member
Posts: 5862
Joined: 29 Apr 2005, 02:20
Location: Ontario, Canada

Re: Pearl Harbor with different priorities

#340

Post by glenn239 » 19 Jan 2017, 19:22

alecsandros wrote:Alternatively, Nagumo could have brought 1 seaplane tender with him, and assign scouting to that ship.
He put to much emphasis on the perfect surprise...
Seaplane tenders and carriers were more subject to adverse weather in the open sea, I think.

alecsandros
Member
Posts: 298
Joined: 23 Jun 2010, 09:37

Re: Pearl Harbor with different priorities

#341

Post by alecsandros » 20 Jan 2017, 10:42

Map of Pearl Harbor fuel storage before 1938, according to:

HISTORIC AMERICAN BUILDINGS SURVEY
U.S. NAVAL BASE, PEARL HARBOR, FUEL FACILITIES BEFORE 1938
(U.S. Naval Base, Pearl Harbor, Naval Supply Center)
(U.S. Naval Base, Pearl Harbor, Pre-WWII Fuel Facilities)
Attachments
fuel tank position at PEARL.png

alecsandros
Member
Posts: 298
Joined: 23 Jun 2010, 09:37

Re: Pearl Harbor with different priorities

#342

Post by alecsandros » 20 Jan 2017, 10:50

Working with "HISTORIC AMERICAN BUILDINGS SURVEY U.S. NAVAL BASE, PEARL HARBOR, FUEL FACILITIES BEFORE 1938 (U.S. Naval Base, Pearl Harbor, Naval Supply Center) (U.S. Naval Base, Pearl Harbor, Pre-WWII Fuel Facilities)", that , allthough the name doesn't imply it, also includes details of fuel facilities built in the war years, I separated the tank farms into working units, and , using Google Maps, tried to measure the surface each tank farm occupied.
The main results are written in red in the map above.

Total number of functional targets is 60 (27 in the Lower Tank Farm, 7 in the Middle tank farm, 17 on the Upper Tank Farm, 9 on Ford Island).

Not included in the measurements are: 3 assimetrical positioned fuel tanks in the Middle Tank Farm (with combined capacity of approx 26670 cubic meters), 1 x 1916-built gasoline tank (approx 335 cubic meters capacity), 1x1916-buiult diesel tank (aprox 1100 cubic meters capacity), the underground fuel oil storage tank completed in 1919 (which doesn't appear anymore on the 1938 map, allthough I think it was still functional at the time), capacity ~ 23500 cubic meters, the fuel pumps houses (about 8 in total), the mineral oil fuel storage (56 small containers in the middle tank farm).

alecsandros
Member
Posts: 298
Joined: 23 Jun 2010, 09:37

Re: Pearl Harbor with different priorities

#343

Post by alecsandros » 20 Jan 2017, 10:56

According to the same source, total storage capacity (of all the fuel tanks in the map) was around 727049cubic meters. With various densities of fuels, this translates into various tonnage held.

Total capacity of the fuel tanks marked with red on the map is around 675444 cubic meters (93% of total storage capacity).

The upper tank farm alone (17 tanks) had capacity of approx 400350 cubic meters (55,06% of total storage capacity).

alecsandros
Member
Posts: 298
Joined: 23 Jun 2010, 09:37

Re: Pearl Harbor with different priorities

#344

Post by alecsandros » 20 Jan 2017, 11:27

Dimensions (approx): (Diameter in meter x Height in meters)
Lower Tank Farm: 32 x 9
Upper Tank Farm: 50 x 12
Middle tank farm: 32 x 10
Ford Island: 11 x 9

alecsandros
Member
Posts: 298
Joined: 23 Jun 2010, 09:37

Re: Pearl Harbor with different priorities

#345

Post by alecsandros » 20 Jan 2017, 13:36

Approx occupied surface by actual fuel tanks inside the total surface of the tank farm:
1) Practical surface of the fuel tanks inside tank farm: 9%
2) Surface of fuel tanks with 5 meters tolerance around them for damaging near misses: 16%
3) Surface of fuel tanks with 10 meters tolerance around them for damaging near misses: 24%

Post Reply

Return to “What if”