Dive bomber accuracy in perspective.

Shortround6 · Nov 19, 2017

You have to remember that the US Torpedoes weren't much good at the Battle of Midway (and for over a year after) which rather skews the results. While aerial torpedoes weren't quite as bad as the submarine torpedoes running too deep (under the target) means a miss that should have been a hit. Defective exploders (fuses) means hits that were duds.

The Arizona was sunk by level bombers using armor piercing bombs dropped by torpedo bombers as the Val couldn't carry the weight.

To sink a ship you have to hit it. Then the hit has to cause fatal damage. In the 1930s the dive bombers could not inflict fatal damage on battleships. Send them to ship yards for months, yes, but not sink them. For the US that capability came with later models of the Dauntless with higher powered engines and the Curtiss SCB2 that could carry 1000lb GP bombs and 1000lb &1600lb AP bombs.
Some books and web sites list some fairly outrageous bomb loads for the Dauntless and while I have no doubt the plane/s could get of the ground/deck with them i doubt they were going very far.
SBD-3 had a 1000hp engine and the manual lists a variety of loads. Like a 1000lb bomb with 100 gallons of fuel, and a 500lb with 140 gallons of fuel. For scouting work the plane could hold 180 gallons or more. (up to 310 gallons if the fuel tanks were unprotected)
SBD-5s got 1200hp engines and SBD-6s got 1350 engines so obviously capability increased but the load of one 1600lb and two 325lbs sometimes listed should be viewed with suspicion as an operational load.

stona · Nov 19, 2017

Also, since this thread is about dive bombing, I would like to point out that by the US inter-war definition, attacks using angles of approach between 40 and 70 degrees were classified as 'glide bombing'. Only those with angles of attack between 70 and 90 degrees were classified as 'dive bombing'.
These classifications had broadened somewhat by WW2, and diving attacks at very moderate angles of 40 to 50 degrees were considered to be dive bombing.

The issues for the Americans in the 1930s were that dive bombers could hit ships, but rarely sink larger ones. They were the least vulnerable, most accurate, but least deadly. In terms of relative accuracy they were by far the best of the three options available.

Torpedo bomber could hit ships where it really counted, below the water line, but the torpedoes were hopelessly unreliable and some required tactics for dropping which were little short of suicidal. The Mark XIII was supposed to be dropped at a speed of less than 100 knots, from 80 feet and at 1,000 yards from the target (and then it was unlikely to work properly). They were potentially the most deadly, but also by far the most vulnerable.

Level bombers, despite a huge investment in bomb sights and other technology and the development of tactics like pattern bombing simply couldn't hit a ship. They were the least vulnerable, the most inaccurate and therefore not at all deadly.

Cheers

Steve

Shortround6 · Nov 19, 2017

The US was using 18in Bliss-Leavitt MK 7 torpedoes (of several different models) for air dropping until 1938-39 when the MK 13 was issued (first in 1938, how long to fully equip all carriers?).
Since just about all drops were from biplanes the drop 'envelope' was probably no better than the MK 13. Unfortunately the drop envelop of the MK 13 was more suited to biplanes than to monoplanes and was most certainly not adequately tested.
This was the latested torpedo bomber the USN had when it was replaced by the Devastator.

it and it's nearly identical predecessor would have been the planes the navy was using for level bombing in the 1932-37 trials.

RCAFson · Nov 19, 2017

stona said:
The relationship between dive angle and height of release is also vitally important.

For bombing angles from 50-90 degrees, up to a release height of about 5,000 feet the accuracy was not markedly different.

I've attached this diagram, a poor picture taken with my phone as I'm not at home but happen to have my copy of 'America's Pursuit of Precision Bombing' with me! It is just about legible.

View attachment 472590

It was the dive bombers, not the torpedo bombers which were decisive at Midway. 42 attacking Devastators failed to score a hit (and many (36?) were lost. However, the USN launched 1,287 aerial torpedoes during the war of which 514 struck their target, a success rate of 40%. Several of those targets were already dead in the water.

The percentage of hits to bombs dropped by the Dauntless dive bombers and Midway makes for better reading.
5 out of 9 hit the Kaga (44.4%), 2 of 3 the Akagi (66.7%), 3 of 8 the Soryu (37.5%) and 4 of 7 the Hiryu (57.1%).

Arnold claimed that the Army dropped 322 bombs in level bombing at Midway, scoring 22 hits and 46 near misses. In fact Japanese records later confirmed that they suffered no hits and no damage from high level bombing. The only major warship confirmed sunt by Army Air Forces during the war was the Japanese light cruiser Abukuma, already disabled by PT boats. She was sunk on 27th October 1944 by 44 B-17s and B-24s of the 5th and 13th Air Forces.

Cheers

Steve

Unless torpedo hit stats are compiled based upon post war enemy records, they have to be taken with the same large grain of salt as per the USAAF bomb hit claims at Midway.

Zipper730 · Feb 17, 2019

Peter Gunn said:
As far as I recall, they dropped the practice bombs on the ship and if I'm not mistaken, UTAH was actually radio controlled for the exercises, both bombs and gunnery until she was sunk at Pearl Harbor.

They had the whole ship unmanned and running on radio?

Greyman · Feb 17, 2019

re: effect of AA fire earlier in the thread; came across some figures from ORS reports on Allied dive bomb attacks vs. road and rail bridges in Italy.

Effort in Relation to Direct Hits (Bridge Size 225' x 30').
A.A. Opposition. ---- Effort per Direct Hit.
Zero or Slight (e.g. 3 L.A.A.) ---- 1 direct hit per 30 bombs
Medium (e.g. 3 L.A.A. + 6 H.A.A.) ---- 1 direct hit per 100 bombs
Intense (e.g. 12 L.A.A. + 6 H.A.A.) ---- 1 direct hit per 150 bombs

fliger747 · Feb 18, 2019

It seems as if everyone had torpedo exploder issues early in the war, except for the Japanese. Combined arms often were the combo that proved fatal warships, Dive bombers with some degree of distraction, distraction of topsides AA and fire control. or just slowing a ship could make the task of the "Torpeckers" more achievable. Yamato and Musashi died agonizing deaths by the Lilliputian swarms. With a strong list Yamato probably took some torpedo hits on her bottom, the most vulnerable area.

Peter Gunn · Feb 19, 2019

Zipper730 said:
They had the whole ship unmanned and running on radio?

Correct, there was a radio control station on another ship that was able to manipulate the engines and rudder, I'm not sure if she shipped a crew standing out of harbor and then they left via small craft and returned to take her back in after the exercise was over, or if she was remote controlled for the entire exercise.

From Wiki (FWIW):
"On 7 April, Utah left Norfolk for sea trials to train her engine room crew and to test the radio-control equipment. The ship could be controlled at varying rates of speed and changes of course: maneuvers that a ship would conduct in battle. Her electric motors, operated by signals from the controlling ship, opened and closed throttle valves, moved her steering gear, and regulated the supply of oil to her boilers. In addition, a Sperry gyro pilot kept the ship on course. She passed her radio control trials on 6 May, and on 1 June, the ship was operated for 3 hours under radio control. On 9 June, she again left Norfolk, bound for San Pedro, California, where she joined Training Squadron 1, Base Force, United States Fleet. Starting in late July, the ship began her first round of target duty, first for the cruisers of the Pacific Fleet, and then for the battleship Nevada. She continued in this role for the next nine years; she participated in Fleet Problem XVI in May 1935, during which she served as a transport for a contingent of Marines.[5] In June, the ship was modified to train anti-aircraft gunners in addition to her target ship duties. To perform this task, she was equipped with a new 1.1-inch (28 mm)/75 caliber anti-aircraft gun in a quadruple mount for experimental testing and development of the new type of weapon."

fliger747 · Feb 19, 2019

Someone once described attempting to level bomb ships at sea maneuvering as trying to drop a ball bearing on a mouse scurrying around on the floor. Dive bombing did bring the chances of a "hit" up considerably. For vulnerable ships such as carriers, destroyers and even cruisers chances of considerable damage with a hit are excellent. Certainly Battleships weren't immune but several hits weren't likely to be fatal. The main issue of the effectiveness of a strike by a dive bomber is the low release altitude, which isn't an issue for an HC bomb, but deprives an AP bomb of necessary kinetic energy.

A Japanese Destroyer captain, whose ship was sunk in the Solomons by level bombers said (more or less) "Even the B-17's get lucky once in a while".

From altitude, surrounding a ship with near misses such that the ship disappears in a shower of spray is very spectacular and looks like a certain "kill". USAAF took much of the credit for the Midway victory!

stona · Feb 20, 2019

Dive bombing was by far the most effective way of bombing a ship. It was something that exercised the minds of the Admiralty, particularly after many destroyers were damaged by bombing during 'Dynamo'.

This graph is compiled from an Admiralty report and includes all ships damaged by bombing in the period. A successful attack was classified as one that damaged a ship, not necessarily sinking it. It includes ships attacked while stationary or in port.

In a 1942 newspaper article no less a figure than Dowding recognised that events in the war so far had shown that air power had become an essential adjunct to sea power. He was a career airman, and stopped short of admitting that it was British sea power which had prevented an invasion and was keeping open the possibility of liberating Europe at a future date. Dowding never really bought into the popular myth of the BoB, but he would hardly publicly undermine it at the height of a world war.

Cheers

Steve

parsifal · Feb 20, 2019

I stumbled onto this report concerning US torpedoes

A Brief History of U.S. Navy Torpedo Development - Part 1

Despite the bad press US torpedoes have generally received over the years, th eir torpedo success rate was actually not too bad. At Page 43 of that report, it is stated....."the overwhelming majority of torpedoes fired during World War II were from submarines in the Pacific theater. Approximately 14,750 torpedoes were fired from submarines at 3184 of the approximately 8200 ships sighted. Of these, 1314 ships were sunk for a total of 5,300,000 tons. In addition, submarines received "probable" credit for another 78 ships of 203,306 tons. The confirmed total included one battleship, eight aircraft carriers, three heavy cruisers and eight light cruisers. These Joint Army Navy Assessment Committee (JANAC) confirmed sinkings (1314) accounted for 55 percent of all Japanese ship losses. The remaining 45 percent were lost to Army and Navy aircraft bombs, mines, and other causes".

People often carry on about how effective the SBD was, but really in comparison to the various torpedo carrying vehicles, the a/c was small potatoes

Zipper730 · Feb 20, 2019

fliger747 said:
Someone once described attempting to level bomb ships at sea maneuvering as trying to drop a ball bearing on a mouse scurrying around on the floor.

Interesting way to look at it, but when you have a whole bunch of dive-bombers dropping all at once (and possibly from different axes), the odds go up greatly. And if I recall the USN would use multiple aircraft at once.

tomo pauk · Feb 20, 2019

parsifal said:
People often carry on about how effective the SBD was, but really in comparison to the various torpedo carrying vehicles, the a/c was small potatoes

Out of Japanese CVs sunk in crucial year of 1942, SBD sunk perhaps 80%? While subs sunk none?

fliger747 · Feb 20, 2019

Comment above was for LEVEL bombing. Ships could and did appraise the fall of bombs and maneuver out of the way. Level bombers could not really follow the maneuvers of a ship and maintain any sort of aiming integrity. A formation might have some better chance just due to the shotgun effect.

Especially in the Med the RN suffered badly from the Stukas.

michaelmaltby · Feb 20, 2019

... likewise the Soviet navy in the Black Sea

Peter Gunn · Feb 20, 2019

fliger747 said:
Comment above was for LEVEL bombing. Ships could and did appraise the fall of bombs and maneuver out of the way. Level bombers could not really follow the maneuvers of a ship and maintain any sort of aiming integrity. A formation might have some better chance just due to the shotgun effect.

Especially in the Med the RN suffered badly from the Stukas.

Re: the shotgun effect.
I think it was on the Hyperwar site that had the USAAC doctrine for level bombers attacking a moving ship and you're right, the idea was a formation left right and center over the ship so no matter which way it turned you'd stand a good chance of getting a hit. However there were VERY few instances in the Pacific where there was a large enough (and more importantly, trained to hit moving targets) formation to succeed.

At midway, Colonel Sweeney had 15 fortress's in the morning attack on the Japanese carriers, he chose to split his force and have ~3 attack each CV, had he kept all 15 together and attacked one CV there is a good possibility they could have put down a carrier. Heck, even with only three Forts, one of his formations only missed Hiryu by less than 500 meters.

But yes, I agree, dive bombing is the best way to put a bomb on a moving target like a ship.

parsifal · Feb 20, 2019

tomo pauk said:
Out of Japanese CVs sunk in crucial year of 1942, SBD sunk perhaps 80%? While subs sunk none?

1942 was the year of Japanese successes asa far as sunk or damaged naval assets were concerned…..two USN CVs sunk outright, one CV heavily damaged (twice)……..USN subs came into their own in 1944. Two subs sank more CV tonnage than more than 1000 USN carrier a/c could manage for the entire year.... IJN was not defeated solely by the USN carrier fleet. With access to less than 2% of the USN resources, the Submarine arm sank more than 0% of Japanese merchant fleet and from memory 60% of the IJN naval tonnages lost.

tomo pauk · Feb 20, 2019

parsifal said:
1942 was the year of Japanese successes asa far as sunk or damaged naval assets were concerned…..two USN CVs sunk outright, one CV heavily damaged (twice)……..USN subs came into their own in 1944. Two subs sank more CV tonnage than more than 1000 USN carrier a/c could manage for the entire year.... IJN was not defeated solely by the USN carrier fleet. With access to less than 2% of the USN resources, the Submarine arm sank more than 0% of Japanese merchant fleet and from memory 60% of the IJN naval tonnages lost.

Nobody said that IJN was solely defeated by USN carrier feet. I've just pointed out that in 1942 SBDs sunk perhaps 80% or IJN carriers, 0% was sunk by subs.

Brooke · Feb 21, 2019

stona said:
This is correct, but it was not obvious at the beginning of the war. The Royal Navy's "Air Defence Instructions, 1939" forbade fast avoiding action against dive bombers. Many ships' commanding officers took a different view and the matter was referred to the director of the Naval Air Division in 1940. He conceded that avoiding action might cause a reduction in bombing accuracy because it would cause the pilot to adjust his aim, which was not regarded as easy, but in conclusion reinforced the official view that avoiding action should not be taken at the expense of throwing off the ship's AA fire.
Maneuverable ships, like destroyers, might be better able to 'dodge' bombs than others. It has been suggested that the destroyer Gurkha was lost to air attack in the Norwegian campaign because her Captain was a 'gunnery officer' who believed in the efficacy of AA fire and chose to keep a steady gun platform without weaving, thereby also presenting a steady target.
Later 'dodging' became the norm.
Alec Dennis was on board the destroyer Griffin as part of Force B off Crete when attacked (along with Greyhound, Gloucester and Fiji) by JU 87s. Twenty Ju 87s made the first attack comingdown in,
"groups of three, one after the other, dividing their attention among all four ships. It was a classic attack, technically interesting, physically terrifying and, actually, ineffectual."
Dennis described how all the bombs missed as they weaved about at full speed with the cruisers (Gloucester and Fiji) throwing up large amounts of flak.
Clearly evasive action did work. Fiji would later endure nearly 13 hours of air attack before finally being hit. She had run out of ammunition and was defiantly firing practice ammunition, solid shot, at the attacking aircraft!
The destroyer Kipling was attacked 83 times in one three hour period, but was not hit.
The light cruiser Naiad managed to dodge 36 near misses in one ten minute period before eventually being hit.
It was these stories, and many like them, that led Cunningham to write (in 'A Sailor's Odyssey'):
"The hasty conclusion that ships are impotent in the face of air attack should not be drawn from the Battle of Crete."
His colleagues in the USN would soon find reason to agree.

Cheers

Steve

The hit probability of AA fire depends a lot on what type of fuze is used. It a "timed" fuze the probability of a hit is very low (see any W.W.II movie showing "flak"). However, if a proximity fuze is used you have a much better chance. I would expect the best strategy would depend on the fuze type. China Lake holds many patents related to proximity fuzes.
China Lake Patents

It turns out that the sight on the A-1 is for use with guns, bombs or rockets (GBR) but it's called a "gun sight". This makes sense since all of these look forward, unlike horizontal bomb sights which look down and forward. There is what amounts to an elevation adjustment that needs to be set depending on which munition is being used.
Mk 20 Mod 4 Gun-Bomb Sight

Does anyone know what sight is used on the A-10 for dive bombing?

Brooke · Feb 21, 2019

tomo pauk said:
Nobody said that IJN was solely defeated by USN carrier feet. I've just pointed out that in 1942 SBDs sunk perhaps 80% or IJN carriers, 0% was sunk by subs.

For the first half of W.W. II the Navy torpedo had multiple design defects to the point that they did NOT work. In the book "Pig Boats" a mission is described where every shot fired by a sub hits the target ship, but none exploded. They saved one torpedo and returned to base.
Torpedoes

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