Dive bomber accuracy in perspective.
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Reading these accounts of successful dive bomber attacks, mainly by the Japanese, what I find remarkable is how ineffective the ships anti aircraft defences were. Was there some tactic such as a simultaneous attack that split and saturated the defences the IJN aviators were good at.
The enemy of the dive bomber was the fighter not AAA it seems.
Dive bombers shot down by AAA in the dive should count as misses because a tactic of releasing a bomb at greater range and altitude would naturally produce more misses but also more successful releases by bombers that have escaped damage or destruction by AAA.
parsifal
Colonel
The magic and usual drop altitude was about 5000 ft for skilled crews. They could drop from that altitude on a normally manouvering ship and stood a reasonable chance of hitting it . That was above the effective ceiling of most fast firing Lt AA except the bofors.
However by slight increases in the spacing of ships, it was found that hit percentages dropped away. Further, Task Groups began to form specif defensive groups to protect high value targets like carriers. Each carrier, or carrier group would be assigned both an inner screen 9with ships as close as 700 yards from the target) in which both Lt and Hy AA could be brought to bear..
The outer screen was generally a couple of thousand meters from the primary target, and tended to concentrate on its long range AA fire to disrupt the incoming attack.
Advances in gunnery fire control, radar direction but most importantly the introduction of the 40mm bofors on a massive scale made divebomber attacks far more difficult. add to that the falling training standards of the air crew, and the introduction of kamikaze tactics, made the final approach runs of tahe attackers a lot lower in altitudes than previously was the case. By the latter part of 1942, attackers from all sides would regulalrly press onto point blank range
Japanese defences were more based on manoeuvre, probably because of the limited ranges of their primary weapon against a/c, the 25mm. I'm not certain what DKM tactics were, for the british it tended to follow USN practices later on, which were superior anyway to the home grown tactics.
However by slight increases in the spacing of ships, it was found that hit percentages dropped away. Further, Task Groups began to form specif defensive groups to protect high value targets like carriers. Each carrier, or carrier group would be assigned both an inner screen 9with ships as close as 700 yards from the target) in which both Lt and Hy AA could be brought to bear..
The outer screen was generally a couple of thousand meters from the primary target, and tended to concentrate on its long range AA fire to disrupt the incoming attack.
Advances in gunnery fire control, radar direction but most importantly the introduction of the 40mm bofors on a massive scale made divebomber attacks far more difficult. add to that the falling training standards of the air crew, and the introduction of kamikaze tactics, made the final approach runs of tahe attackers a lot lower in altitudes than previously was the case. By the latter part of 1942, attackers from all sides would regulalrly press onto point blank range
Japanese defences were more based on manoeuvre, probably because of the limited ranges of their primary weapon against a/c, the 25mm. I'm not certain what DKM tactics were, for the british it tended to follow USN practices later on, which were superior anyway to the home grown tactics.
Japanese Navy Bomber Tactics. Bombers entered a shallow dive, then a steep 55 degree dive from 1500m followed by release at around 600m. Doesn't look like they used the full Vertical attacks of the Ju 87. The Japanese attacks were highly coordinated.
View: https://www.youtube.com/watch?v=MLfbYHPWx2o
This video has an analysis of the attack on Yorktown.
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The main purpose of the flak is to protect the target, if it does so by disrupting the attack run and causing a miss it did achieve its purpose.
Of course, when you are dealing with higly trained and determined pilots the flak loses quite a bit of its disuasive and disruptive qualities and the target is down to hoping their flak crews shoot them down, which is something thay may diminish the effects of the strike, but never prevent them. AT least back then and in spite of the IJN pilots presing to within 300m-400m before droping.
I think the IJN simply expected enemy pilots to do as theirs did and disregard flak, in which case drastic maneuver is the only real option leading to their open AA formations with plenty of space for the carriers to turn as they pleased. Besides, it seems they were quite happy with the 25mm until the realities of war showed them otherwise.
Shortround6
Major General
Just about everybody's light AA was woefully inadequate to the needs/requirements of actual combat in the early years.
and many Navies had designed ships to strict weight limits (even if cheating was more or less rampant in some navies) which means you have to sacrifice surface weapons for AA weapons or A/S weapons for AA. There is only so much top weight you can put on a ship before stability becomes an issue. A pre war destroyer may be able to have a few few swinging heavy machineguns/20mm added without much problem but large mounts, especially powered, were a problem. Especially as they usually had to mounted high up.
The US being one of the few navies to actually take dive bombing seriously from both offensive and defensive points of view.
The US 1.1 in machine cannon and mount being one of the few combinations to really try to counter dive bombing. Please note I said TRY as neither the gun or the mounting turned out to be all that successful in service.
Please note the geared rack in line with the guns which allowed for a small amount of "slew" independent of the normal traverse/turning of the mounting. This was to allow the guns to follow the path of a dive bomber at high angles of elevation when traversing the entire mount would throw the guns off. This may be the only mount that allowed that type of motion and shows that the US Navy was thinking about the problems of high angle gunnery.
The gun and the mounting were over complicated and required large amounts of maintenance.
Weights went form 4.7 to 6.25 tons and while late mounts lost the slewing feature they gained remote power control.
Scale of issue was 4 mounts for large ships and 1 or 2 for destroyers which is almost laughable compared to the outfits of 40mm Bofors guns later in the war. Especially when you consider the next step below these guns was the .50 cal machinegun and not the 20mm in the the late 30s through 1942.
and many Navies had designed ships to strict weight limits (even if cheating was more or less rampant in some navies) which means you have to sacrifice surface weapons for AA weapons or A/S weapons for AA. There is only so much top weight you can put on a ship before stability becomes an issue. A pre war destroyer may be able to have a few few swinging heavy machineguns/20mm added without much problem but large mounts, especially powered, were a problem. Especially as they usually had to mounted high up.
The US being one of the few navies to actually take dive bombing seriously from both offensive and defensive points of view.
The US 1.1 in machine cannon and mount being one of the few combinations to really try to counter dive bombing. Please note I said TRY as neither the gun or the mounting turned out to be all that successful in service.
Please note the geared rack in line with the guns which allowed for a small amount of "slew" independent of the normal traverse/turning of the mounting. This was to allow the guns to follow the path of a dive bomber at high angles of elevation when traversing the entire mount would throw the guns off. This may be the only mount that allowed that type of motion and shows that the US Navy was thinking about the problems of high angle gunnery.
The gun and the mounting were over complicated and required large amounts of maintenance.
Weights went form 4.7 to 6.25 tons and while late mounts lost the slewing feature they gained remote power control.
Scale of issue was 4 mounts for large ships and 1 or 2 for destroyers which is almost laughable compared to the outfits of 40mm Bofors guns later in the war. Especially when you consider the next step below these guns was the .50 cal machinegun and not the 20mm in the the late 30s through 1942.
In pre-war exercises from 1932 to 1940 the USN ran comparisons of the accuracy of dive bombing and level bombing against ships taking various evasive actions (simple, radical, unrestricted, zig-zag etc.).
Dive bombing was invariably more accurate, the percentage of hits being remarkably consistent in all scenarios, between 12% and 23%.
For level bombing the results were almost invariably a single figure percentage of hits, typically between 1% and 4%. In 1933 and 1934, from 8,000 feet, no hits were scored. In 1937, against a ship making 'steady' manoeuvres, from 10,000 feet a high of 11.1% of hits were achieved. This was comparable with the 12.7% achieved that year by dive bombing, but stands out in the tables as an anomaly.
Cheers
Steve
Dive bombing was invariably more accurate, the percentage of hits being remarkably consistent in all scenarios, between 12% and 23%.
For level bombing the results were almost invariably a single figure percentage of hits, typically between 1% and 4%. In 1933 and 1934, from 8,000 feet, no hits were scored. In 1937, against a ship making 'steady' manoeuvres, from 10,000 feet a high of 11.1% of hits were achieved. This was comparable with the 12.7% achieved that year by dive bombing, but stands out in the tables as an anomaly.
Cheers
Steve
Shortround6
Major General
That is a real problem with limited tests and statistics.
11.1% is one bomb out of nine. or 10 bombs out of 90. The first could obviously be a fluke. The second is probably well in excess of the number of bombs actually dropped in such a peace time test. Even two hits out of 18 dropped doesn't really give you a good basis to extrapolate from as the sample is too small.
also to be considered is what was considered a hit? and on what?
US target ship in the 30s
Or were the practice bombs dropped on a towed raft with observers judging hits and misses?
11.1% is one bomb out of nine. or 10 bombs out of 90. The first could obviously be a fluke. The second is probably well in excess of the number of bombs actually dropped in such a peace time test. Even two hits out of 18 dropped doesn't really give you a good basis to extrapolate from as the sample is too small.
also to be considered is what was considered a hit? and on what?
US target ship in the 30s
Or were the practice bombs dropped on a towed raft with observers judging hits and misses?
The target ship was the USS Utah, what was dropped I have no idea. I don't even know if there was consistency, year on year. All I have is a table of results.
There would be more in the Army Air Corps Board, Report No.4, Vol.4 of 1941. That's the source of the table.
Cheers
Steve
There would be more in the Army Air Corps Board, Report No.4, Vol.4 of 1941. That's the source of the table.
Cheers
Steve
Shortround6
Major General
Thank you,
I was just pointing out that such tables could have some rather scattered results due to small number of samples.
You have done a great job of bringing up such subjects and data.
I was just pointing out that such tables could have some rather scattered results due to small number of samples.
You have done a great job of bringing up such subjects and data.
Steady maneuvers would go under simple right?
The manoeuvres are different, year by year.
1932 Simple 18.2% hits dive bombing, 5.6% level bombing from 8.000 feet
1933 Radical 20% hits dive bombing, 0 hits level bombing from 8,000 feet
1934 Radical 13% hits dive bombing, 0 hits level bombing from 8,000 feet
1935 Restricted 17.3% hits dive bombing, 9.4% level bombing from 8,000 feet
1936 Radical 23.7% hits dive bombing, 8.3% level bombing from 10,000 feet
1937 Sharp Turns 11.3% hits dive bombing, 5.6% level bombing from 10,000 feet
1937 Steady 12.7% hits dive bombing, 11.1% level bombing from 10,000 feet
1938 Steady 13.9% hits dive bombing, 4.1% level bombing from 12,000 feet
1938 Sharp Turns 14.5% hits dive bombing, 2.4% level bombing from 12,000 feet.
1939 Zig Zag 21.8% hits dive bombing, 4.4% level bombing from 17,000 feet
1939 Unrestricted 18.1% hits dive bombing 1.1% level bombing from 17,000 feet
1940 Zig Zag 19.1% hits dive bombing, 1.9% level bombing from 17.000 feet
1940 Unrestricted 23.1% hits dive bombing, 1.9% level bombing from 17,000 feet.
About the only conclusion to de drawn is that dive bombing was usually more accurate than level bombing, whatever the target was doing.
In the confusion it is hardly surprising that a unified doctrine was never formed. The Navy had established three ways of attacking ships (including torpedo bombers) and would not give up any of them. The Air Corps was too young to be bound by traditions and a hierarchical rank structure, it was relatively young officers who developed the doctrine of 'high' altitude precision bombing. The Navy's inability to develop a unified doctrine left hundreds of torpedo bomber crewmen vulnerable and exposed to enemy defences and caused the Navy to hold on to thousands (yes, thousands) of Norden bomb sights at a time when the Air Force had a critical need for them. I know we Brits sometimes say that the Americans don't get irony, but surely the irony of the failure of the USN in WW2 to use the bomb sight which it had developed, while the US Army, which did use the sight but had to subordinate its needs for the device to the Navy would not be lost on them
Cheers
Steve
1932 Simple 18.2% hits dive bombing, 5.6% level bombing from 8.000 feet
1933 Radical 20% hits dive bombing, 0 hits level bombing from 8,000 feet
1934 Radical 13% hits dive bombing, 0 hits level bombing from 8,000 feet
1935 Restricted 17.3% hits dive bombing, 9.4% level bombing from 8,000 feet
1936 Radical 23.7% hits dive bombing, 8.3% level bombing from 10,000 feet
1937 Sharp Turns 11.3% hits dive bombing, 5.6% level bombing from 10,000 feet
1937 Steady 12.7% hits dive bombing, 11.1% level bombing from 10,000 feet
1938 Steady 13.9% hits dive bombing, 4.1% level bombing from 12,000 feet
1938 Sharp Turns 14.5% hits dive bombing, 2.4% level bombing from 12,000 feet.
1939 Zig Zag 21.8% hits dive bombing, 4.4% level bombing from 17,000 feet
1939 Unrestricted 18.1% hits dive bombing 1.1% level bombing from 17,000 feet
1940 Zig Zag 19.1% hits dive bombing, 1.9% level bombing from 17.000 feet
1940 Unrestricted 23.1% hits dive bombing, 1.9% level bombing from 17,000 feet.
About the only conclusion to de drawn is that dive bombing was usually more accurate than level bombing, whatever the target was doing.
In the confusion it is hardly surprising that a unified doctrine was never formed. The Navy had established three ways of attacking ships (including torpedo bombers) and would not give up any of them. The Air Corps was too young to be bound by traditions and a hierarchical rank structure, it was relatively young officers who developed the doctrine of 'high' altitude precision bombing. The Navy's inability to develop a unified doctrine left hundreds of torpedo bomber crewmen vulnerable and exposed to enemy defences and caused the Navy to hold on to thousands (yes, thousands) of Norden bomb sights at a time when the Air Force had a critical need for them. I know we Brits sometimes say that the Americans don't get irony, but surely the irony of the failure of the USN in WW2 to use the bomb sight which it had developed, while the US Army, which did use the sight but had to subordinate its needs for the device to the Navy would not be lost on them
Cheers
Steve
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That I didn't know, but I'm guessing you don't know what they meant by steady?
A pattern I notice is that level bombing is very ineffective when maneuvers are unrestricted!
Ironically, it gave them great versatility. Though I would personally say that level bombing would be largely useless for attacking ships, though against harbors & shipyards it'd probably work well enough.
Their idea of level bombing was to avoid being attacked by guns on the ground. It's of course not as accurate...
I think they should have used dive-bombers more liberally if you ask me, though I'll admit that the torpedo bombers did prove useful for certain things (air-borne battle-control, anti-sub, etc)
The US Navy used it on the Catalina, and the Avengers sometimes (bombing Japan)
Peter Gunn
Master Sergeant
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.
Shortround6
Major General
I would note that at any given time during the 1930s and very early 40s that the dive bombers were rather restricted in the size/weight of the bomb they could carry. The torpedo bomber, if used as a level bomber, could either carry multiple bombs or a single of much larger size than the dive bomber.
Armor piercing bombs needed to be dropped from certain altitudes to achieve max penetration and in the days of biplane dive bombers, the speed achieved in the dive wasn't enough to compensate for the lower release altitude.
It wasn't until 1943 or early 44 that the Japanese battleships ceased to be a large bugaboo to allied naval forces.
Armor piercing bombs needed to be dropped from certain altitudes to achieve max penetration and in the days of biplane dive bombers, the speed achieved in the dive wasn't enough to compensate for the lower release altitude.
It wasn't until 1943 or early 44 that the Japanese battleships ceased to be a large bugaboo to allied naval forces.
vikingBerserker
Lieutenant General
For level bombing by both the Navy and Air Corps, practice bombs were dropped on the USS Utah, they were normally US Navy Mark VII water fillable bombers weighted to 50lb bombs after being filled with water which could be colored to track the aircraft or squadron that made hits. The Utah had double layers of timber placed on top of her deck to prevent damage from them. I'm not sure how they handled Dive Bombers
Here is a view of her front:
Here is a view of her front:
Shortround6
Major General
As a note to the bombing results so kindly provided Stona the Douglas TBD torpedo bomber was only issued to the first two squadrons to use it in Oct and Dec of 1937. First monoplane on american carriers.
The first US monoplane dive bomber was the Northrop BT
only 55 built and deliveries didn't start till 1938.
So the tests in 1932-37 would have been done by a variety of biplanes. How many of the later tests were done by biplanes I have no idea but the Hornet still had 2 squadrons of Curtiss SBC-4s aboard in Dec of 1941.
In regards to another thread note the auxiliary fuel tank
The first US monoplane dive bomber was the Northrop BT
only 55 built and deliveries didn't start till 1938.
So the tests in 1932-37 would have been done by a variety of biplanes. How many of the later tests were done by biplanes I have no idea but the Hornet still had 2 squadrons of Curtiss SBC-4s aboard in Dec of 1941.
In regards to another thread note the auxiliary fuel tank
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.
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
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.
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
