The Bouncing Bomb Used In The Pacific

Pursuing a new air attack technique, Allied bombers in the South-West pacific were increasing their toll of Japanese merchant vessels and warships. The method was known as "skip bombing," in which the aircraft came in on its target at a very low altitude, usually about 50 feet, travelling at high speed and releasing its bombs when close to the objective; the bombs travelled forward horizontally for a distance before hitting the water just in front of the vessel, then bounced up from the surface of the sea against it. The R.A.F was the first to employ this ingenious plan, against land targets in Northern France, in 1941. The Americans adopted it, experimented with it for both land and sea attack, and found it successful against Japanese shipping.

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In Diagram 1, attacking planes are approaching their objective low above the water, thus presenting difficult targets for enemy fire (A). In Diagram 2 the bomber pilot (B) is aiming his plane at one of the merchant vessels; it was the pilot, judging the crucial moment, not the bomb-aimer (C) who actually released the bombs. When the appropriate striking distance had been reached, the bombs leave the plane, hit the water's surface a glancing blow (D) and then bounce on into the hull or super-structure of the vessel. By this time the plane (E) had passed over the ship and is clear of the danger area. Delayed action bombs were sometimes used; these gave the attacking plane more time to get away from the target before the dropped bombs exploded.

Any type of aircraft may skip-bomb. Flying Fortresses have been known to carry out the manoeuvre successfully; but best for the purpose was a medium bomber, such as the Mitchell or Marauder. Bombs used ranged in weights up to 1,000 lb. Beyond that weight, their shape altered considerably and was not adaptable to the bouncing-bomb technique; 250-1b, and 500-lb bombs were mostly used. In misty or cloudy weather, low-level reconnaissance followed by surprise skip-bombing had proved particularly deadly. The main purpose behind the low level method of attack was that the vessels presented a bigger target than they did from a height; it was in fact, a combination of dive-bombing and aerial torpedo attack.

 

.....what were the advantages or disadvantages of skip bombing vs dive bombing and also torpedo bombers?
...they used the skip bombing to great effect at the Battle of the Bismarck Sea
..they used the B-25s...so I take it they could not convert these for torpedo attacks....
...for torpedo attacks, they had to go slower/etc?
...with skip bombing, couldn't they make more than one run?
....with skip bombing, or bombing, the bomb went off even with a near miss---this wasn't true for torpedoes?
....bombing more of a sure hit or near miss?

 

The only disadvantages of skip homing were that you had to fly low(250-300 feet down to masthead height) and you aircraft might get clipped by part of the explosion. Advantages were it was probably the most accurate type of bombing at the time. Training time was fairly quick relative to other bombing styles.

Dive bombing had it's own disadvantages. It required a fairly skilled pilot to achieve desired accuracy. Further, the aircraft needed to be stable in a dive. The advantage was that unless the bombers were shot down before entering the dive, they were relatively unstoppable until the attack was completed.

US Torpedo bombing in 1942...Well, the only advantage was that it could apply a lot of explosive directly to a ship hull...If it hit. The disadvantages were many. The torpedo had to be dropped very low & slow(100 knots & 50 feet - not that a loaded TBD could go much faster), lest the torpedo be damaged hitting the water. The torpedoes were of dubious quality in terms of construction and detonation(although Shoho was the exception to the rule.). The torpedoes were slow, often giving the enemy time to evade. The pilot also needed to be highly trained.

That is where skip bombing made it's mark in the Pacific. But, had been used many times before in the Pacific against single ships.

Lots of aircraft skip bombed; B-17s, PBYs, A-20s, etc.

I don't recall seeing any evidence of fitting a torpedo to a B-25...But, hey, I just came across an early P-38 fitted with 2 torpedoes(experimentally). But, probably it was many things; lack of torpedo availability to Army aircraft, lack of a reliable torpedo,lengthy pilot training, low hit probability, etc.

They could make as many runs as they had bombs. However, SOP was to drop 2 bombs per run, all but guaranteed one would hit.

Early on one 5-second fuse were used. Later on three fuses of 4- & 5-second delay were used. They should initiate on the first skip.

Skip...more of a sure hit...Even surer with 2 on the same run.

 

This thread is slightly OT in as much as "Skip bombing" as practiced by aircraft against ships using ordinary bombs is not what might be taken to be the same as THE bouncing bomb, which was the Upkeep bomb which was famously used on the Dams raid and launched with a spin already imparted.

The British did build a smaller Upkeep bomb codenamed Highball and trained a 618 squadron to use it as an anti shipping weapon against the Tirpiz.


No 618 Squadron was trained to use the Highball and to operated the dH Mosquito from aircraft carriers. It was deployed to the Pacific in December 1944.
No. 618 Squadron RAF - Wikipedia
They trained for carrier landings at RAF Beccles (Ellough) with a painted carrier deck marked on the runway.

 

..I don't recall the navy using skip bombing....
..I would think with skip bombing, you could '''jink'' more so than with a torpedo attack

 

what did they use against the Amiens Prison?

 

Once they added all the machine guns to the nose, you didn't jink. You nudged the rudder a little left, then a little right, and hosed the ship from stem to stern an back again.

As to the Navy, I don't recall the carrier types skip bombing. The PBYs did, but I am not sure about the PBJs(Navy B-25s).

 

500 lb. Bombs with 11 second fuses.

 

roger that..I did a quick search, but did not see it

 

..I meant if they were taking heavy fire/etc--and how long were torpedo runs vs skip bombing?
...also, they didn't have dive bombers too much in the 5th AF, I thought--so necessity the mother of skip bombing ?
..I guess the MGs kept the AAA fire down......

 

here it says 100 feet away from the target!!!??

damn!
WWII Pioneers of Skip Bombing - Warfare History Network

 

here page 32 talks about skip bombing with diagrams

https://www.airuniversity.af.edu/Portals/10/AUPress/Books/B_0096_RODMAN_WAR_OF_THEIR_OWN.pdf

 

The USN refers to masthead or skip bombing in the USF-74 (1944) as low level bombing. Attacks are recommended not to exceed three planes at any one target at any one time and are noted as a good tactic for night attacks.

The USN identified four different attack profiles
- dive bombing
- glide bombing
- level bombing
- low level bombing

Dive bombing was defined as occurring at angles of attack ranging from 90° down to 60°. These attacks fell easily in the realm of the SBD and the SB2C, both of which were equipped with bomb displacement gear which ensured the bomb, carried centerline for aiming purposes, cleared the propeller arc on release at the high end of the angle range. High end means anything over 70° may be cause for concern. A dive bombing attack, correctly executed, especially when in the 70° plus angles was very difficult to defend against.

Glide bombing was defined as occurring at angles of attack ranging from 55° down to 30°. Glide bombing by attack, as opposed to fighter, aircraft was where one could expect to find torpedo-bombers as no displacement gear is required. Glide bomb, however, remained a very dangerous way of doing business. Although one keeps one’s speed up, it requires a straight in approach on a target which, if shooting back, is straight into the optimal angle of defensive fires. This is similar to the torpedo attack profile which was not known for happy outcomes. The only advantage over the torpedo approach was speed, the more the better. More below.

Level bombing is usually, and correctly, thought of as being in the province of the multi-engine bomber. What is often forgotten is that both the TBD and the TBF/TBM were equipped with Norden bomb sights (after all, the Norden bomb sight was developed for the USN long before the USAAF ever got their hands on one). One might note that TBDs carried out level bombing attacks during the Lae-Salamaua raid of 10 March 1942. What should be remembered is that the USN was well aware that level bombing of moving ships was pretty much an exercise in futility. Level bombing by torpedo bombers was pretty much limited to shore targets and usually from higher altitudes. At the end of the war it was not unusual to see flights of TBMs unloading their ordnance on stationary targets such as the ferry docks at Hakodate on Hokkaido while the dive bombers and fighter-bombers went after the ferries themselves.

Low level bombing was originally the preferred method for fighters, back in the days of F4Fs carrying itty-bitty bombs. At least on early fighter squadron, VF-42 comes to mind, dispensed with the idea entirely and removed the bomb racks from under the wings of their aircraft. No racks, no low level bombing. All that said, the advent of the rocket for low level attacks reopened the field to just about anyone who wanted to play. All the active carrier aircraft by the end of the war, F6F, F4U, FM-2, TBM, TBF, carried and dispensed rockets with great abandon at maritime and land targets. One F6F driver even was able to down a Japanese plane with a rocket. Napalm was another interesting capability brought increased usage of low level bombing in support of ground forces.

And then there were the variations on a theme. Fighters such as the F6F and F4U, by the end of the war were known for their bomb hauling ability. In fact, by the end of the decade, the pure dive bomber equipped with displacement gear would go away forever. It is oft bandied about that these fighters, when not performing more glamorous fighter type shooting up the bad guys’ airplanes duties or even those pesky low level attacks, executed dive bombing attacks. Well, yes, and no. A more correct description was a very steep glide bombing profile or, perhaps, a not so steep dive bombing attack. The truth to the matter was these attacks were usually conducted at attack angle ranging from about 45° up to around 65°. While still facing the potential problem of traveling through some prime defensive fire terrain, the speeds at which such attacks could be executed paid off more for the attacker then the angle of approach did for the defender . . . not to mention that Japanese AA fire had its, ummm, problems which only got worse as time went on.

NAVAER 00-805-46 “Glide Bombing - how to do it . . .” (May 1945) mentions low level attacks in it's dicussion of the subject:

“INTRODUCTION

“WHAT IT IS

“The most direct method of bombing is to carry the bomb personally right down to the target, dump it in the enemy’s lap, and get away fast. That, roughly, is the idea behind glide bombing, a form of attack conceived by pilots flying many different types of planes. It is an effective standard maneuver that pays off in a substantial percentage of hits at low cost.

“The term “glide bombing” does not mean dive bombing or mast head bombing. These are excellent forms of attack under certain conditions, but they differ in essentials from glide bombing.

“Glide bombing is a high-speed attack delivered with accelerating motion at angles of 30° to 55° without the use of dive brakes, flaps, or other speed-retarding devices.

“Get these differences in mind:

“Dive bombing is undertaken from high-angle dive, usually 60° to 70°, braked by flaps and/or wheels to maintain a constant medium speed (about 280-300 knots) during the latter part of the dive.

“Masthead, skip, or minimum altitude bombing involves drops from level flight or a very shallow glide (under 30°) at extremely low altitude and short range. The approach may or may not be made from a steep dive or glide.

“Horizontal bombing, of course, is done from steady level flight, usually at medium to high altitudes.

“Glide bombing is primarily a high-speed maneuver designed to capitalize on the element of surprise by getting the plane down to the target quickly and get HITS. The angle of an attack, normally 50°, pus the build-up speed makes a glide bomber a difficult target for antiaircraft gunners, but favorable for accurate sighting by the pilot. After bombs are away, the glide bomber has the advantage of great speed for swift retirement from the range or enemy antiaircraft fire."

 

..also used by the 5th, I thought were para-frags..not a bombing tactic--but again, a difference from the Navy?..of course the Navy did not have big carrier based bombers.....
any other differences?
AN-M40 Fragmentation Bomb

 

..thank you Leonard...seems like rockets are ''more accurate''' ..not as much punch, but more accurate...especially by ''untrained'''/etc pilots on bombing

 

Once rockets came into use, a lot of time, at least in the USN & USMC, was spent training in their use and in practice to achieve a reasonable level of accuracy.

 

Let me correct that for you....

The chance of hitting a target with a rocket was quite small. The big advantage of a rocket was that the pilot didn't have to overfly the ships oh so nasty AA guns

Highball was interesting because it could be launched at 350mph whereas torpedoes needed to be dropped at a fatally slow speed.

 

..seems like with rockets they were aimed ''like'' the guns--straight on where as with bombs, you had to release at the time, the right height/etc--much harder ...easier to hit with rockets than with bombs, unless well trained?

 

Performance envelope for the Mk XII improved as time went on, and actually fairly early according to the date on this memo . . .

Your opinion on employment of rockets is duly noted, but I'd suggest there were more than just a few Japanese on more that just a few vessels, warships and merchants, who might disagree. To paraphrase what Stalin supposedly once said, "quantity is sometimes a quality all its own"

 

Well, on paper they were improved, however, combat performance was still far below expectations.
U. S. Navy Bureau of Ordnance in World War II

You would not happen to have a copy of the 1943 torpedo study would you?
I have been looking for it off and on online, but have never come across it.

Combat performance did not really improve until 1944.