How ship bombing changed during the course of WW2

[oldcrowcv63]

Attached is a dramatic circa 1945 photo of a presumably lone B-25 bombing and sinking a maneuvering IJN destroyer Amatsukaze which IIRC had an incredible wartime career which exemplified the general prowess of IJN destroyer operations. The images of so many sailor-survivors struggling in the water evokes more sympathy today than it may have during the war… It looks like the photo bird (probably another B-25) didn't score a hit. There are also lots of what appear to be splashes in the photo indicating the presence of other allied a/c.
The fact that this sequence almost certainly didn't happen in the time it took to take three successive photos suggests a/c were hanging around to see the results of the strike.

Considering the horrible record of (not dive-bombing torpedo) aerial attacks against maneuvering Axis and allied marine targets, this seems to me to be a true image of one of the lessons learned during the war and how the evolution of tactics made all the difference in improving the general effectiveness of attacks. Level bombing from altitude in excess of 15,000' was pretty worthless but probably a bit safer for the aircrew facing ship borne AAA, while approaching the target and dropping ordnance at masthead height provided a higher hit probability but increased the crew to the possibility of a AAA Hit. Wonder if there might be an analogy here to the evolution and longevity of aerial torpedo attacks and also with the RN's experience during the Falkland Island campaign. Just wondering….

source: http://imgur.com/a/BQvIr#7T8dvfQ

 

[Glider]

Its a remarkable set of photos no doubt but that isn't the Amatseukaze, this vessel is a lot smaller. Probably an escort of some type or a converted minsweeper

 

[bobbysocks]

think if i were doing the bombing run i would come in from the front or rear of the ship. coming in from the side you are a target for way more AA and your target is narrow. coming the other way you would contend with less AA and your target gets a lot bigger. now if i was carrying a torpedo that would be different....but i might be missing the big picture....

 

[GrauGeist]

A bomb-run that carries along the centerline of the target can produce considerable damage, but getting the bomb to strike the hull at or below the waterline is amplified because of hydraulic pressure. So the higher risk of a side-on attack yeilds higher rewards.

Here's a great photo of a Japanese Frigate under attack by a B-25 http://www.ww2aircraft.net/forum/ww2-general/picture-day-39445-60.html#post1109536

 

[vikingBerserker]

I believe they were skip bombing which you really need to do from the side.

 

[oldcrowcv63]

Its a remarkable set of photos no doubt but that isn't the Amatseukaze, this vessel is a lot smaller. Probably an escort of some type or a converted minsweeper

After a cursory search, it looked like you were correct, especially after I checked photos of the ship (see below) and the vessel sunk is clearly smaller than the original Amatsukaze. However, it appears the story is not straightforward and is pretty interesting

(put title here) states (among other relevant text regarding the damage inflicted during her battle with the USS Redfin, SS-272):

11-16 January (1944):
With YUKIKAZE and CHITOSE, escorted high-speed tanker convoy (HI-31: OMUROSAN MARU, TATEKAWA MARU, ITSUKUSHIMA MARU, GENYO MARU, KUROSHIO MARU, HOKUROKU MARU) from Moji bound for Singapore. Heavy damage: torpedoed north of the Spratly Islands by USS REDFIN (SS-272). Magazine explosion forward severed bow and killed 80, including Comdesdiv 16 (Captain Furukawa Bunji [49]). Presumed sunk by convoy, left adrift for six days until discovery by patrol plane.

15 November (1944):
Arrived in Singapore for fitting of temporary bow, then local escort dut

6 April (1945):
Sunk: in air attack by U.S. Army B-25s, six miles east of Amoy (24-30 N, 118-10 E). Hit by three bombs; crew managed to beach ship, but storm foiled salvage attempts on 7 April and wreck largely abandoned ashore. 44 dead, but Lieutenant Morita among survivors.


Wikipedia also explains:

On 11 January 1944, while escorting a convoy of four ships in the South China Sea, Amatsukaze was torpedoed by the submarine USS Redfin. The resulting magazine explosion severed the bow of the ship and killed 80 crewman. Miraculously, the ship did not sink. Presumed sunk, the ship was not discovered for six days until she was spotted by a patrol plane. Amatsukaze was eventually towed to Singapore where a temporary bow was rigged.

On 6 April 1945, Amatsukaze was attacked by USAAF B-25s, six miles east of Amoy (24°30′N 118°10′E). Her crew managed to beach the ship; salvage attempts were abandoned on 8 April. On 10 April, the ship was scuttled by charges placed on the ship.

from

MaritimeQuest - Daily Event for October

I found another similar photo showing what appears to be major changes to the ship's profile… What happened to her stacks?

From the first web site listed above:

[2] Editorial Note II - Spectacular photographs taken during Amatsukaze's final action reveal the character of her transformation. Her hull had been cut off at the former location of No.1 TT mount, and a temporary bridge and snub-nosed bow fitted there. Her No.2 stack became her only stack, and was just abaft the temporary bridge. Perhaps not surprisingly, in this case No.2 5-inch turret was not removed, and she retained both aft turrets. From No.2 stack aft, Amatsukaze thus remained a normal looking Kagero-class destroyer.

The absence of the two aft turrets would suggest this is NOT the Amatsukaze and was a misidentified corvette or frigate escort.

Also the ship targeted in the photos turns turtle and is almost certainly sunk thus unlikely to have been beached as described in the above.

 

[Koopernic]

At what distance from target and at what range was bomb release during a skip bombing attack?

Using high school physics I am assuming that if release was at 100m (330ft altitude) the fall of the bomb would be 4.5 seconds. Assuming an attack run at 220mph (100m/s) the bomb release would have been at 450 meters. Raising the attack run altitude to 200m (660ft) gives a 6.5 second bomb fall time and potentially a 650m standoff distance.

All are within range of Light AAA.

Fw 200C condor attacks must have had a similar profile, rather than skip bombing they had an anti bounce ring on the bomb to ensure the bomb sank. A time fuze then detonated the bomb under the ship and broke its back. Three bombs were released in sequence to ensure that at least one 'hit'.

Fw 200 Condor attacks were eventually thwarted. How could B-25 be so much more survivable that the USAAF is taking this kind of risk against an IJN destroyer?

These B25'x' seem to have a solid 8 gun nose, suggesting AAA suppression (killing the AAA gun crew) was part of the strategy.

The amount of AAA that needed to be fitted to a ship to provide credible defense must have been very high. The navweaps.com website suggests Japanese AAA fell behind. Not enough computing capability in the gun sights and a lack of AAA in the 40mm class. (they used 25mm)

 

[BiffF15]

Koopernic,

They should have 12 forward firing fixed .50's (remember the four cheek mounted guns, two on each side) plus the top turret. I would thinkt he concentration of fire would be enough to put large holes in the side of smaller ships (guess'tamation).

Cheers,
Bif

 

[GrauGeist]

If you guys take a look at the Japanese Frigate getting worked over in the link I provided above, you can see that the B-25 was hosing the deck with it's forward weapons as it was making it's bomb run. There is also airborn debris and missing defenders at various gun stations...that Frigate was having a very bad day...

 

[nuuumannn]

The absence of the two aft turrets would suggest this is NOT the Amatsukaze and was a misidentified corvette or frigate escort.

Yep, quite a difference in size and profile when you compare pictures of the two ships together. Based on a couple of books I have the ship under attack is likely to be an Improved Type B escort, the one that Dave linked to in the Picture of the Day thread was a Type D escort. In the pic with the B-25, the funnel has been shot away; it was forward of the aft mast that can be seen dangling just forward of the gun emplacement on the after superstructure. The Improved Type Bs were built between 1944 and '45 and were built of prefabricated sectionas, taking as little as four to five months to complete. Eight of them were lost during the war to enemy action, two, of which this is one, were sunk by US aircraft, Okinawa and Inagi.

you can see that the B-25 was hosing the deck with it's forward weapons as it was making its bomb run.

That probably explains the missing funnel in the picture above.

Just a bit of interest on skip bombing, the Italian Picchiatelli (Ju 87) used skip bombing for the sinking of enemy shipping. This from an article I wrote about the Picciatelli once.

"Capitano Guiseppe Cenni of 97° Gruppo persued an alternative method to sinking enemy shipping to tactics suggested by the Germans. Ships were attacked by means of a shallow dive to very low level, then Cenni would release his bomb near the water, whereupon it would skip across the water's surface and strike the enemy vessel. This method proved successful during the Greek campaign; a freighter and gun boat being sunk by this method. The Greeks initially suspected the Stuka had sunk the freighter Susanna with a torpedo."

 

[GrauGeist]

And it was a combination of being lazy and being on an ipad that kept me from reposting the photo in my earlier post

Now that I'm on my computer, I'll post it.

Note the bomb has just been released from the B-25, seen below the B-25's port wing, superimposed against the geyser of water.

And as a bonus, here's the zoom view of the crew aboard the Frigate. Notice some missing crewmen, others between stations and even a few that look to be wounded.

 

[Koopernic]

It's very hard to tell what is going on in terms of the relative position of bomb splashes, aircraft and the destroyer. This was clearly photographed using a telephoto lens from quite far off. The failure of Navies to provide adequet Armour for their AAA gunners seems unbelievable. I'd hesitate to call the ship under attack a "Destroyer" it looks like a smaller weaker unit such as an escort Frigate.

Torpedo boat was a small boat that was designed to torpedo a Dreadnaught etc, they eventually grew 10 fold to nearly 1000 tons.

Destroyer was designed by the RN to protect battleships by "Destroying" torpedo boats. They were larger and faster than a torpedo boat and capable of keeping up with a fast fleet actions though they were short on range. The British needed a lot so they got down to 1500 tons. The Germans needed high performance so they got to 4500 tons.

Frigate is not as fast as a destroyer and designed to escort convoys that it never detaches from.

A Cruiser is a fast ship, large enough to offer great range and speed for carrying out reconnaissance, shadowing the enemy by keeping out of range using its speed. They became essential for escorting Fast Carriers since destroyers lacked the range though they might have the speed.

 

[cherry blossom]

There is a post http://www.ww2aircraft.net/forum/aviation/swedish-turnip-attack-method-22658.html on German efforts. Both Germans and Americans chose to approach at low altitude and high speed with delayed action bombs but possibly the Germans were aiming at sinking the bomb below the ship. The ultimate development of the German approach was to design a bomb to travel underwater and curve upwards.

edit: I finally found details of the BT series bombs at http://www.secretprojects.co.uk/forum/index.php/topic,18301.msg185794.html#msg185794 and Deutsche Abwurfmunition des Zweiten Weltkrieges ? Wikipedia

 

[Glider]

Getting back to the original question the UK originally used low level bombing (Blenheim) and torpedoes (Wellington, Beaufort and Hampden). This developed into a reliance on Rockets (Beaufighter, Typhoon and Mosquito) and Torpedoes (Beaufighter). The US seemed to concentrate on low level and skip bombing, they didn't use rockets as an anti shipping weapon and seemed to have turned away from torpedoes (B26) which were used in the early days of the pacific war.

Germany originally used Dive Bombers and Torpedoes. As the war progressed they developed a range of guided weapons. I think you could say that Japan followed the German route but using suicide attacks instead of guided weapons.

 

[cherry blossom]

The USAAF turned away from torpedoes, possibly because American torpedoes were very poor until 1944. The USN finally produced very good torpedoes just in time to sink Musashi and Yamato
View: https://www.youtube.com/watch?v=R552QfbD8AU.

The Germans similarly started with very bad torpedoes and had to buy reasonable ones from Italy. However, none of the German or Italian torpedoes could be dropped at the speeds of late war USN or IJN (45 cm Type 91 Mod 3 Strong and later Japan Torpedoes of World War II) torpedoes.

 

[m37b1]

At what distance from target and at what range was bomb release during a skip bombing attack?

Using high school physics I am assuming that if release was at 100m (330ft altitude) the fall of the bomb would be 4.5 seconds. Assuming an attack run at 220mph (100m/s) the bomb release would have been at 450 meters. Raising the attack run altitude to 200m (660ft) gives a 6.5 second bomb fall time and potentially a 650m standoff distance.

All are within range of Light AAA.

Fw 200C condor attacks must have had a similar profile, rather than skip bombing they had an anti bounce ring on the bomb to ensure the bomb sank. A time fuze then detonated the bomb under the ship and broke its back. Three bombs were released in sequence to ensure that at least one 'hit'.

Fw 200 Condor attacks were eventually thwarted. How could B-25 be so much more survivable that the USAAF is taking this kind of risk against an IJN destroyer?

These B25'x' seem to have a solid 8 gun nose, suggesting AAA suppression (killing the AAA gun crew) was part of the strategy.

The amount of AAA that needed to be fitted to a ship to provide credible defense must have been very high. The navweaps.com website suggests Japanese AAA fell behind. Not enough computing capability in the gun sights and a lack of AAA in the 40mm class. (they used 25mm)

IIRC Skip-Bombing was done @ 200mph - 200ft Alt - 200ft distance to target. "Triple Twos"

 

[Koopernic]

There is a post http://www.ww2aircraft.net/forum/aviation/swedish-turnip-attack-method-22658.html on German efforts. Both Germans and Americans chose to approach at low altitude and high speed with delayed action bombs but possibly the Germans were aiming at sinking the bomb below the ship. The ultimate development of the German approach was to design a bomb to travel underwater and curve upwards.

edit: I finally found details of the BT series bombs at http://www.secretprojects.co.uk/forum/index.php/topic,18301.msg185794.html#msg185794 and Deutsche Abwurfmunition des Zweiten Weltkrieges ? Wikipedia

Fleischers "German Air Dropped Weapons" has an illustration of the bombs used for what I think is the so called 'turnip attack': the bombs often had a 'prall scheibe' or 'impact disk' added to the nose of the bomb to prevent the bomb from bouncing. The bomb would aimed well ahead of the ship and decelerate rapidly due to the flat disk and perhaps move forward underwater about 40ft and sink to approximatly 40ft-60ft with about a 5.5 second delay and then detonate sending a shockwave upwards into the hull of the boat. A blast in this position is apparently very serious, in general a depth charge underneath a submarine near the surface was far more deadly than one detonated above it when at depth due to a focusing effect caused by the lower upward impedance towards the surface of the sea.

I'll edit in a scan when I get home.

The BT series of Bord Torpedos eg eg BT1000 (the number is the proximate weight but really indicates the bomb shackle type required) was a similar but highly refined idea. Instead of a "Prall Scheibe"/"Impact Disk" the Torpedo bomb was made highly conical with only a small flat nose section so as to pierce the water without bouncing and then continue on under water for hundreds of meters simply on the basis of kinetic energy and its streamlining, something that appears initially quite surprising. These bombs were built and test dropped and this aspect worked. I'll provide some photographs as well. A key aspect of the technology was an influence or proximity fuse so as to trigger the BT underneath the ship, such fuzes had been unreliable in conventional torpedo's at the beginning of the war but achieved reliability towards the end.

Although it was intended to aim these BT "Bord Torpedo" using the TSA2D computing toss bombing sight (which worked through the conventional reflector site of a fighter and by automatically releasing the bomb during a pullup). The aiming the bomb, however, could be as simpe as approaching level, at high speed and releasing without the constraints of torpedo in terms of release limits of height and speed. Accuracy was not required as even if the bomb impacted 100m or more ahead of the target ship it would pierce into the water and continue till it passed underneath the ship and detonated. The smaller ones, eg BT200, could even come with a rocket booster. The use of the TSA2D would have allowed a wider attack profile such as shallow dives and considerable standoff distance achieved by tossing the bomb upwards. The TSA2D kept track of the fighter bombers position using an accelerometers from the point that the pullup was commenced, it was found that the Me 262 jet was more accurate than the Fw 190 due to lack of vibration from the piston engine. The trials show the TSA2D was quite accurate.

You'll find the BT was a very important weapon that figured prominently in Luftwaffe plans.

I've just finished reading "Wolfgang Fischer's" "Luftwaffe Fighter Pilot" and he describes attacking and hitting a Victory Ship during the Normandy landings using the Werfer-Granate 21 or WGr.21 tube launched rockets that had been used against USAAF heavy bombers. That's all they had. He had to use the drop tank release on the fighter dash to fire it as the joystick gun trigger hadn't been wired in yet. The weapon was idiosyncratic since it had been designed for a army artillery bombardment indirect fire trajectory, when used in a relatively flat trajectory one had to aim 80m to the left at 1km. Presumably due to the spin the magnus effect curved the rocket as it started falling.