Alternatives to Pearl Harbour?

[Saphroneth]

Pearl Harbor Papers, At Dawn We Slept. Keep an eye out for a book on PH by Mark Wenger in the next few years. Long delayed, it will be the Shattered Sword of that battle, and will superceed Prange as the premier account.

...er, hold on. How the heck do you know that?

 

[Glenn239]

Because oil tanks are hard targets, and not very large ones at that

The oil tanks were area targets, large fields, like airfields, or the naval yard. When 5th CAR DIV level bombed Hickam, it didn't aim for individual planes, it pattern bombed the area. So too an oil tank farm - it was a question solely of landing the bombs in the target area, not hitting individual tanks.

(Heck, the Kate's service ceiling was only 27,000 feet, which suggests that it's going to be hard pressed to even reach 25,000 feet at a carrier strike range.) I also don't think a Kate had a bomb sight, though I could be wrong.

It had a bomb sight on the floor - the battleships were much smaller targets than an oil tank field.

 

[Tallil2long]

Glenn, I have a question. At Pearl, Fuchida was the last to land on Akagi, and I know he'd loitered a few minutes before returning, to assess strike results. Do you have any idea of the total duration of Akagi's recovery? At Midway she recovered her strike from 0837 to 0900. Do you have such info for the recovery of her second wave at Pearl?

 

[Glenn239]

...er, hold on. How the heck do you know that?

Mark posts occassionally over at Combined Fleet (so does John Parshall and Anthony Tully). He's been talking about it every now and again since I think before 2010. Unfortunately, he had a serious accident at a Civil War reenactment some years ago - the book was originally supposed to be out by now. From everything I've heard, it's going to be freaking awesome.

 

[Tallil2long]

Pearl Harbor Papers, At Dawn We Slept. Keep an eye out for a book on PH by Mark Wenger in the next few years. Long delayed, it will be the Shattered Sword of that battle, and will superceed Prange as the premier account.

I read At Dawn We Slept back in high school, maybe 1984. Good book as I vaguely recall.

 

[Glenn239]

Glenn, I have a question. At Pearl, Fuchida was the last to land on Akagi, and I know he'd loitered a few minutes before returning, to assess strike results. Do you have any idea of the total duration of Akagi's recovery? At Midway she recovered her strike from 0837 to 0900. Do you have such info for the recovery of her second wave at Pearl?

None, but I suspect that at Pearl Harbor the recovery time was much longer in duration than at Midway, since the attacking forces seemed more dispersed at Oahu and my impression is they departed back to the carriers in small groups. If Nagumo had hit Oahu again, I think they'd have just closed the decks and launched when ready - and either the aloft stragglers could wait or they would ditch. In relation to that, note that Fuchida was 1st Wave, while I would assume most of the stragglers would be 2nd Wave, launched an hour later.

 

[Saphroneth]

Huh, found a useful potential source about the oil tanks:

Tomioka Sadatoshi, chief of the Operations Section of Navy General Staff, had told Nagumo to get his ships home at all costs. In any case, the effects of an attack on the facilities may not have been so great as postwar historians believed. Zimm (2011) has concluded that a third wave attack concentrated on the Navy Yard would not have destroyed more than 12% of the facilities even under the most optimistic assumptions, while the oil tanks would have been relatively easy to replace.

 

[Saphroneth]

None, but I suspect that at Pearl Harbor the recovery time was much longer in duration than at Midway, since the attacking forces seemed more dispersed at Oahu and my impression is they departed back to the carriers in small groups. If Nagumo had hit Oahu again, I think they'd have just closed the decks and launched when ready - and either the aloft stragglers could wait or they would ditch. In relation to that, note that Fuchida was 1st Wave, while I would assume most of the stragglers would be 2nd Wave, launched an hour later.

...which would mean dumping half the original strike force, since they were low on fuel when they arrived back as the strike was made from long range.

 

[Tallil2long]

Huh, found a useful potential source about the oil tanks:

Yah, I just picked up his book on Kindle.
He also pointed out that the sides of the tanks tapered from 1.5in thickness at the bottom to .75in at the top. And each was surrounded by its own berm. Not sure how much damage fragmentation would do, so I dunno if just dumping bombs anywhere within the grounds is going to get all that many. Especially when the standard 250kg bomb had a .2 second delay.

 

[Glenn239]

Launch and recovery are two separate things. You can do one of them with a given deck park position - you cannot do both.

Shattered Sword explicitly stated that the carriers did not launch CAP with a deck park, correct? Upon what basis did they make that claim?

Shattered Sword explicity stated that carriers did not recover aircraft with deck parks, but Fuchida's Pearl Harbor account says that when he landed, it was doing just that.

Do you have any evidence to contradict this? That is, an example of either fighters taking off with the front of the deck explicitly obstructed, or fighters landing on with the back of the deck explicitly obstructed?

This is the 20 million dollar question - could and did IJN carriers recover and launch CAP with a deck park? Answer - I don't know Fuchida's Midway account indirectly says 'yes', but he never explicitly stated as such, and his account had the first strike lowered around 0830, which was clearly wrong. For Shattered Sword, they say no - using the B-17 photographic evidence that the decks were clear.

The physical evidence available is the layout of the Akagi- page 464 of Shattered Sword if you have it. Beside the bridge is the launch point for the CAP Zeros - where the Zeros are pictured. The rear crash barrier is just behind the midship elevator. The space between the crash barriers is where a deck park could be while launching and recovering Zeros. If the park is not to be moved, and if the fighters are going down the center lift then being pushed foward (the Akagi's DB's were attacking Midway, so the admiship hanger was empty) then it appears any park must be small - maybe 6 aircraft. If pushing the park back and forth a bit were acceptable, then maybe 12 aircraft could be accomodated. Since elevator times were an issue, there would be an incentive to maintain even a 6 plane park. But did they actually do it? I have no idea. All we know for sure is that at 0800-0830, they didn't.

 

[Saphroneth]

Well, Akagi was the longest IJN aircraft carrier. EVEN IF she could fit a dozen of them, none of the others could fit any because the launch distances would be the same. Maybe Sho and Zui could fit a few IF Akagi could fit six.
Akagi - 260 m.
Hiryu and Soryu - 227 m.
Kaga - 247 m.
Shokaku and Zuikaku - 257 m.
Further IJN carriers were Unryu,which means repeat Hiryu. If they found the extra length vital, they certainly didn't build further carriers with it.

 

[TFSmith121]

Just as an FYI, oil storage tanks are commonly a) reveted, and

Huh, found a useful potential source about the oil tanks:

Just as an FYI, oil storage tanks are commonly a) reveted (i.e. surrounded by berms), and b) built atop pavement, for the obvious reasons...

See below for an (granted, single) example of what a refinery and tank farm complex struck by a heavy level bombing attack looked like:

Destroying a tank farm - or even damaging it heavily - through aerial bombardment was far from simple in the 1940s, given conventional bombs aimed visually.

Best,

 

[Tallil2long]

Shattered Sword explicitly stated that the carriers did not launch CAP with a deck park, correct? Upon what basis did they make that claim?

Shattered Sword explicity stated that carriers did not recover aircraft with deck parks, but Fuchida's Pearl Harbor account says that when he landed, it was doing just that.



This is the 20 million dollar question - could and did IJN carriers recover and launch CAP with a deck park? Answer - I don't know Fuchida's Midway account indirectly says 'yes', but he never explicitly stated as such, and his account had the first strike lowered around 0830, which was clearly wrong. For Shattered Sword, they say no - using the B-17 photographic evidence that the decks were clear.

The physical evidence available is the layout of the Akagi- page 464 of Shattered Sword if you have it. Beside the bridge is the launch point for the CAP Zeros - where the Zeros are pictured. The rear crash barrier is just behind the midship elevator. The space between the crash barriers is where a deck park could be while launching and recovering Zeros. If the park is not to be moved, and if the fighters are going down the center lift then being pushed foward (the Akagi's DB's were attacking Midway, so the admiship hanger was empty) then it appears any park must be small - maybe 6 aircraft. If pushing the park back and forth a bit were acceptable, then maybe 12 aircraft could be accomodated. Since elevator times were an issue, there would be an incentive to maintain even a 6 plane park. But did they actually do it? I have no idea. All we know for sure is that at 0800-0830, they didn't.

On page 229 of Shattered Sword, the authors state:
"While fighters could theoretically take off from the bow during spotting, in practice we know of no instances where this was done."

As the authors made heavy use of 'Senshi Sosho' in writing the book, as well as air group records from the Japanese carriers, and consulted heavily with Japanese experts on carrier ops, this seems fairly authoritative.

As for deck parks (as opposed to merely pushing excess landed aircraft forward of the barrier while waiting for elevators to strike them below, in order to let more aircraft land), Shattered Sword notes that the only times the IJN used deck parks was during the Pearl op (when carrying larger than normal air wings), and CarDiv 5 during the Indian Ocean (authors do not say why in this case).

Again, given the thoroughness with which the authors mined Japanese sources, this seems fairly authoritative.

Edit:
Below I reproduce the chart of Akagi's air ops during Midway provided by Parshall and Tully in Doctrine Matters, a NWCR article (Summer 2001), available online.

0655—launch CAP (three fighters)
0659—recover CAP (three fighters)
0710—launch CAP (five fighters)
0720—recover CAP (one fighter)
0726—recover CAP (one fighter)
0736—recover CAP (three fighters)
0750—recover CAP (two fighters)
0808—launch CAP (three fighters)
0832—launch CAP (four fighters)
0837–0900—recover Midway attack force plus three CAP fighters 0910—recover CAP (one fighter)
0932—launch CAP (five fighters)
0945—launch CAP (three fighters)
0951—recover CAP (two fighters)
1010—recover CAP (three fighters).

For whatever it's worth, Akagi could recover CAP as quickly as 4-6 minutes after launching CAP, but it took 11-18 minutes to launch CAP after recovering CAP.

Small sample size, and we don't know what other factors were involved, but this is somewhat suggestive. It looks as if recovering fighters had to wait just long enough for the launching ones to get out of the way. While launching planes had perhaps to be pushed around a bit (spotting further aft?) after the recovering planes were handled (stricken below or pushed to a safe spot).

 

[Tallil2long]

This is the 20 million dollar question - could and did IJN carriers recover and launch CAP with a deck park?

The physical evidence available is the layout of the Akagi- page 464 of Shattered Sword if you have it. Beside the bridge is the launch point for the CAP Zeros - where the Zeros are pictured. The rear crash barrier is just behind the midship elevator. The space between the crash barriers is where a deck park could be while launching and recovering Zeros. If the park is not to be moved, and if the fighters are going down the center lift then being pushed foward (the Akagi's DB's were attacking Midway, so the admiship hanger was empty) then it appears any park must be small - maybe 6 aircraft. If pushing the park back and forth a bit were acceptable, then maybe 12 aircraft could be accomodated. Since elevator times were an issue, there would be an incentive to maintain even a 6 plane park. But did they actually do it? I have no idea. All we know for sure is that at 0800-0830, they didn't.

Your plan certainly looks workable, yet from Akagi's flight log at Midway it is apparent that they weren't doing this: that log lists discrete time frames for recovery and launch, separated by several minutes lag.

Why didn't they do it? I don't know. Two guesses come to mind.

First, airspace conflicts. A recovering Zero that overshot and was waved off would have to immediately get airspeed up a bit, which is best done flying straight. Meanwhile, a Zero taking off is ahead of the carrier trying to get its speed up and gain altitude. Perhaps the potential for collision was considered unacceptable?

The second notion is that both recovery and launch required considerable attention from flight ops personnel located on the small island. Perhaps dividing their attention wasn't considered workable. Note that in Sunburst, Peattie asserts that IJN carriers did not use LSOs -- the flight ops officer on the island did the job.

 

[Carl Schwamberger]

I'm trying to sort out the conversation here on the deck spotting/use/cycle. One thing that comes to mind is that I've been told the Japanese did all the servicing & arming of the aircraft below deck. Is this correct? If so then could there have been ready strike groups below deck that could have been launched in approx 20-30 minutes after the order to move them to launch positions?

Or am I incorrect on where they aircraft were prepared?