How Accurate Was Dive Bombing

[kitplane01]

Suppose you have a reasonably competent pilot, with reasonable hardware, on a reasonable day, an no one shooting at him (so maybe in training). How accurate was dive bombing? How likely would it be to hit a ship, or a pill box?

 

[Shortround6]

a ship, or a pill box

Ship?
Small destroyer was about 340ft by 35-38 ft but moved pretty fast. Leander cruiser was about 550 ft by 55 ft.
A Victory ship hull was around 550ft by 62 ft but moved slower.

Pill box is how big??? But stationary.
Pill box tends to blend into the surrounding terrain (depends?) Ships, aside from smoke, tend to stand out on the ocean.

 

[Greyman]

For the Royal Navy, 920 (training) dive bomb attacks were studied at the Naval School at the accuracy was 30 yards for a 50% zone -- with 13 bombs required to hit a target 10 yards radius. Not sure when all of these training attacks were but the report was July '45.

 

[RCAFson]

"The Swordfish was also capable of operating as a dive-bomber. During 1939, Swordfish on board HMS Glorious participated in a series of dive-bombing trials, during which 439 practice bombs were dropped at dive angles of 60, 67 and 70 degrees, against the target ship HMS Centurion. Tests against a stationary target showed an average error of 49 yd (45 m) from a release height of 1,300 ft (400 m) and a dive angle of 70 degrees; tests against a manoeuvring target showed an average error of 44 yd (40 m) from a drop height of 1,800 ft (550 m) and a dive angle of 60 degrees." (wikipedia via Smith, Peter C. Dive Bomber! )

 

[A.G. Williams]

A decent Ju 87 Stuka pilot was said to be able to keep the bombs within 30m of the target.
The closer to the vertical they dived, the more accurate they were.

 

[WATU]

Not sure how predictive training bomb runs were for results against a real evading ship firing AA. AA against dive bombers was relatively ineffective as aiming techniques could not cope with the rate of descent but the pilot was unlikely to want to rely on that fact if indeed he was aware of it.

 

[Leonidas]

A decent Ju 87 Stuka pilot was said to be able to keep the bombs within 30m of the target.
The closer to the vertical they dived, the more accurate they were.

Because then the bomb won't continue moving forward as much. If that makes sense

 

[waroff]

Do you know this dive bombing US Navy training film?

 

[pbehn]

The closer you get to vertical the more you eliminate errors from the trajectory of a bomb. Small boats like trawlers could change direction quicker than a Ju 87 in the English Channel. The drawbacks are you give an easy shot to any defenders, you need increasingly specialised planes to do it, no plane can escort a dive bomber when it is diving and then there is the little thing about the pilot blacking out needing an automatic dive pull out system.

 

[tomo pauk]

The closer you get to vertical the more you eliminate errors from the trajectory of a bomb. Small boats like trawlers could change direction quicker than a Ju 87 in the English Channel. The drawbacks are you give an easy shot to any defenders, you need increasingly specialised planes to do it, no plane can escort a dive bomber when it is diving and then there is the little thing about the pilot blacking out needing an automatic dive pull out system.

A dive bomber that is well into it's dive might give a good shot to the defenders closest to the target. Not just for any defender in range.
AA gunners from Akagi and Kaga and ships in range killed just 1 dive bomber during the Battle of Midway.

 

[Admiral Beez]

A dive bomber that is well into it's dive might give a good shot to the defenders closest to the target. Not just for any defender in range.
AA gunners from Akagi and Kaga and ships in range killed just 1 dive bomber during the Battle of Midway.

IJN AA was rubbish. No radar, small guns (25mm), no proximity fuses, crap ROF due to only 15 round drums, etc. Here's their main weapon Japan 25 mm/60 (1") Type 96 - NavWeaps

 

[Shortround6]

At Midway the main anti-dive bomber gun (almost the only anti-dive bomber gun) was the 25mm.

Kaga had eleven twin mounts at Midway?
Practical rate of fire was around 110rpm because of the need to change the 15 round magazines. cycle rate was about 220rpm or just over 3 1/2 rounds per second. Magazine would last just over 4 seconds. Judge the dive bomber attack well because the gunners might only get one magazine per barrel fired at one attacking airplane. Then a 3-4 second pause while new magazines are fitted. Mount is hand powered in traverse and elevation. Gun is too short ranged for nearby ships with 25mm guns to have much effect. Japanese had loose formations so ships could maneuver.

Some ships had a few 13mm machine guns or even 6.5mm/7.7mm machineguns but hits by them are going to be too late (bomb already released)

 

[Admiral Beez]

That skinny twin Japanese mount just can't compare with the quad 40mm Bofors, especially with dopler proximity fuses.

 

[Shortround6]

problem for the Americans is that the 40mm won't get doppler proximity fuses (or any kind of proximity fuse) until WW II is well over, in fact well after the Korean war.

They had enough trouble trying to fit a proximity fuse into a 3in (76mm) shell and didn't achieve that until around two years after they got one in a 5in shell.

Americans shifted to twin 3in guns replacing the quad Bofors post war simply because the 3in gun could use proximity fuses and the 40mm could not.

 

[Admiral Beez]

Pill box is how big??? But stationary.
Pill box tends to blend into the surrounding terrain (depends?) Ships, aside from smoke, tend to stand out on the ocean.

I remember some propaganda or television history special showing a Stuka hitting a moving tank, and at the time I thought that's unlikely. Then again, they claimed thousands of kills in Russia.

 

[Koopernic]

That skinny twin Japanese mount just can't compare with the quad 40mm Bofors, especially with dopler proximity fuses.

View attachment 620574

No proximity fuses for the 40mm boffors in WW2. That came latter, much latter, probably the 1970s. It was trouble fitting the proximity fuse to anything smnaller than the US 5" DP but it was eventually transferred to the British 4.7,4.5 and 4 inch guns and US 90mm.

The British 40mm POM POM despite its low velocity had a big round which could carry a time delay fuse hence the masses of black smoke puffs. It was a bit of a scarry munition. I read of a round exploding at the muzzle killing the gun crew.

The power of the Boffors was its big high velocity round that allowed it to engage at large distances.

The smallest radio proximity fuse that saw service was probably 90mm or perhaps some odd 75mm weapon.

In the 1980s the Ford Aerospace M247 Sergeant York with twin Boffors 40mm L70 was probably out performed by 35mm hit to kill weapons.

It pitted against General Dynamics' entry also mounted twin Oerlikon KDA cannons, but mounted them side by side in a new aluminum turret, as opposed to either side of the turret as in the Gepard. They could be fired in either the automatic or semiautomatic mode, and their combined rate of fire was 1,100 rounds per minute from a 600-round magazine. The radar and fire control systems were derived from their Phalanx CIWS system, with the tracking radar mounted on the front of the turret, beside the guns, and the search radar on top. The turret also included independently stabilized optical sights and a laser range finder for manual engagements.

Hit to kill is probably better than proximity.

 

[Glider]

IJN AA was rubbish. No radar, small guns (25mm), no proximity fuses, crap ROF due to only 15 round drums, etc. Here's their main weapon Japan 25 mm/60 (1") Type 96 - NavWeaps

IJN was below par compared to most navies I agree, but to call it rubbish isn't correct. Their radar was well behind in both development and distribution I agree but at the start of the war is wasn't that common in other navies. The 25mm is often rubbished but it compared well to the the German 20mm C30 which only had a 20rd magazine and apparently was also prone to jamming. The 25mm had a similar rof, a better MV and a bigger warhead.
It wasn't a match for the allied 20mm agreed, but it wasn't rubbish.

 

[Koopernic]

IJN was below par compared to most navies I agree, but to call it rubbish isn't correct. Their radar was well behind in both development and distribution I agree but at the start of the war is wasn't that common in other navies. The 25mm is often rubbished but it compared well to the the German 20mm C30 which only had a 20rd magazine and apparently was also prone to jamming. The 25mm had a similar rof, a better MV and a bigger warhead.
It wasn't a match for the allied 20mm agreed, but it wasn't rubbish.

The C30 remained in service throughout the war but the "30" indicates its acceptance in 1930. It was replaced by the C38 in 1938 ofcourse which had twice the rate of fire and was more reliable. These guns had excellent ballistics, better than the Oerlikon. The C30 is probably what mostly shredded the French Air Force and RAF in ground attack in the Battle of France so it wasn't that bad.

The French 25mm Hotchkis and Japanese 25mm were the same gun and had excellent ballistics but a moderate Rate of Fire. The weakness of both was the poor and unsteady mount.

By contrast the German C30 and C38 guns had solid, accurate and vibration free hand cranked mounts that gave them greater accuracy and range.

The C38 came into its own in the quad mount. The 20 round magazine was not so bad. It auto ejected when emptied and could be easily replaced by one man. By contrast the 60 round Oerlikon was a bigger job to replace. In practice two of the C38 in a quad mount were fired while the other two were getting reloaded and cooling off.

The 3.7cm FLAK 37 was supposed to replace the 2.0cm C38 but its weight and ROF were a little disappointing and production was modest in part because the quad mount 2.0cm C38 was so effective. However the 3.7cm FLAK 42 using the 30mm MK 103 gas operated mechanism doubled ROF and had a travelling weight of only 1.2 tons making it quite mobile and deadly.

The German navies 3.7cm SK30 had excellent ballistics as good as the Boffors but only had a semi automatic mechanism. War time pressure prevented an auto loader being developed. The FLAK 3.7cm guns were used instead.

 

[A.G. Williams]

In the 1980s the Ford Aerospace M247 Sergeant York with twin Boffors 40mm L70 was probably out performed by 35mm hit to kill weapons.

It pitted against General Dynamics' entry also mounted twin Oerlikon KDA cannons, but mounted them side by side in a new aluminum turret, as opposed to either side of the turret as in the Gepard. They could be fired in either the automatic or semiautomatic mode, and their combined rate of fire was 1,100 rounds per minute from a 600-round magazine. The radar and fire control systems were derived from their Phalanx CIWS system, with the tracking radar mounted on the front of the turret, beside the guns, and the search radar on top. The turret also included independently stabilized optical sights and a laser range finder for manual engagements.

Hit to kill is probably better than proximity.

Actually, the 35mm contender which was beaten by the Sgt York was also firing prox-fuzed ammo - its the smallest round that has used that, I think, and it was evidently considered too small as it never entered service. In part, this was because Oerlikon had a better idea and introduced the AHEAD ammo in 35mm; basically like a shrapnel round which was timed to burst open just in front of the target aircraft or missile, showering it with a shotgun blast of tungsten pellets. This works well and is still in service today.

The 3.7cm FLAK 37 was supposed to replace the 2.0cm C38 but its weight and ROF were a little disappointing and production was modest in part because the C30. However the 3.7cm FLAK 42 using the MK 103 mechanism doubled ROF and had a travelling weight of only 1.2 tons making it quite mobile and deadly.

The German navies 3.7cm SK30 had excellent ballistics as good as the Boffors but only had a semi automatic mechanismm. War time pressure prevented an auto loader being developed. The FLAK 3.7cm guns were used instead.

It's a bit more complicated than that. Rheinmetall developed an automatic naval AA gun in 3,7cm, the SKC/36, which fired its own unique ammo. The gun seems to have been a copy of the Bofors. It wasn't successful but was revived (presumably with improvements) and entered service as the Flak M42. The Flak M43 was the one with the MK 103 mechanism and was adopted by all of the services, but didn't have the time to prove its worth. The earlier army/Luftwaffe 3,7cm Flak guns were also mounted on ships.

 

[Koopernic]

Yoji Ito had invented at multicavity magnetron with circular cavities and narrow slits about a year earlier than Randall & Boot and the Japanese had a working microwave search radar by 1942 type 22 radar they used for surface search on their cruisers.

Oddly the Japanese Navy Never shared with the Germans, this may have been due to communication difficulties and it seems never with the Japanese Army who struggled to copy German Wurzburg radars for AAA defense.

Derivatives of Type 22 radar had lobe switching for blind fire.

Type 22 General Purpose Radar:
Wavelength10 cm
Pulse Width10 microsecond, Pulse Repetition Frequency 2500 Hz
Scan rate 5 rotations per minute
Power 2 kW
Range:
20 nautical miles (35 km) aircraft group
10 nautical miles (17 km) single aircraft
13 nautical miles (24 km) battleship
Antenna Horn
Display A scope
Accuracy 220 yards/3 degrees
200 meters/3 degrees
Resolution 1600 yards/40 degrees
1500 meters/40 degrees
Weight
2910 lb (1320 kg) as installed on surface ship
4717 lb (2140 kg) as installed on submarine
Production: 300 sets. Fitted to modern destroyers in summer 1942, to Kongo-class battleships 1942-10, to light cruisers 1943-6, to the Yamatos 1943-10, and to other destroyers 1944-9.


The Japanese Type 22 radar, also known as Mark 2 Model 2, saw wide operational use in the war, being installed on surface ships and submarines. Though nominally a surface search radar, it was also used for air search and for fire control. It was based on an early Japanese version of the cavity magnetron, the M-312, used 40 vacuum tubes, and had limited power. Quality control during production was a serious problem: Of the first sixy sets built, only about six actually worked. The chief difficulty was achieving adequate precision in machining the oddly-shaped cavities in the M-312 magnetron to achieve the precise frequency required to match the magnetron with the M-60 vacuum tube used in the receiver.

The first set was tested in October 1941 and a pre-production version called the Model 103 was experimentally shipped on Hyuga just before the battle of Midway. With its dual steerable horn, it was nicknamed "Bluefin Tuna" or "Horse Mackerel." Mass production was authorized by the end of 1942 but no materials were allocated. One of the Army technicians on the project proceeded to acquire materials through the black market, which led to some of the accountants on the project being arrested and held by the police for a month. Its first operational triumph was allowing the evacuation flotilla for Kiska to navigate under cover of heavy fog. Because of continuing difficulty matching components, production never came close to the target of 150 sets a month.

An improved version, the Mod 1, with a more stable heterodyne receiver, was rushed to the fleet in time for the Battle of the Philippine Sea. Another version, the 22-Kai-3, was designed for submarines and differed in having a pulse repetition rate of 600 Hz.