Improved Skua for FAA?

[Shortround6]

Maybe the RNs concentration on torpedo attack instead of dive bombing is not as backward as sometimes suggested.

It is not backwards, it does limit options however.
For the US the MK 13 torpedo meant the dive bomber was the primary ship killer (although the Navy didn't know it at times) until late 43 or 1944(?).

And while carriers were most important target they were not the only targets.

The Story of the dive bomber is also somewhat tied to the story of light automatic cannon for AA guns.

Not everybody's AA defenses were the same, Japanese were rather poor in AA defense of most of the war.


Not everybody's bombs were the same (and it is the bomb that kills the ship, not the airplane) and the Japanese were late developing large bombs.

Using AP bombs was not easy. Depending on how much armor you want to go through you need to drop from a higher altitude than an HE bomb making hits more difficult. If you drop for a lower altitude and/or a slower speed the bomb won't go through and armor and may bounce or break up. Bomb specifications are not always easy to get.
However the US 1000lb AP bomb was supposed to penetrate 5in of deck from 10,000ft from a level bomber or from 6500ft in a 300kt 60 degree dive. Please note that anything less in any of the 3 conditions means less penetration and dropping with two conditions not met is really going to screw things up. Also note the AP bomb carried about 150lbs of HE.
The Famous US 1600lb AP bomb (and most of you know I think it was over rated, fame wise) Could defeat 7in of deck armor, drop height not given. It's extra weight allowed it defeat the same 5in deck armor as the 1000lbs bomb but do it from 7500ft from a level bomber or from 4500ft in the 300kt 60 degree dive. The 1600lb bomb carried a bit lower percentage of HE for around 205-215lbs of HE.

The 1000lb AP bomb was trying to punch a 12in hole.
The 1600lb AP bomb was trying to punch a 14in hole.
The US 1000lb SAP bomb was trying to punch a 15in hole. The SAP bomb was carrying about 300lbs of HE. Or about what a British 1000lb GP bomb carried. the British 1000lb GP bomb was NOT an SAP bomb. It was about 16in diameter and the bomb body wasn't strong enough for armor punching without breaking up, might nave been dandy for unarmored or lightly armored ships though.


You need impact speed for AP bombs (or SAP bombs) to penetrate armor. You can't get the speed needed if you are dropping low and slow.
You also may have more trouble with the fuses.

When comparing naval dive bombers to Army fighter planes, Bridges and dams don't move.

But diving bombing land targets also means coping with the AA defenses. By 1944 the Germans, Americans and British were fielding much greater AA batteries than they had just a few years early which made the classic dive bomber attack profiles of 1940-41 near suicidal. AA guns on land were easier to camouflage/hide/spread out over wider area.

 

[EwenS]

And the problem is that as you increase the drop height the more the variables highlighted in the video in the above post come into play, even against a stationary target, let alone one that is manoeuvering or shooting back.

I've posted before about Operation Bronte before. This was a series of dive bombing tests carried out in 1948 against HMS Nelson moored out in the Firth of Forth with 1,000lb and 2,000lb bombs.

The original orders for one series of tests called for the Barracudas to drop 2,000lb Mk.IV AP bombs (with reduced charges for test purposes so that the damage could be evaluated) from 8,000 ft. They had 39 straight misses. So the dropping height had to be reduced to 6,500ft at an intended speed of 285 knots "to give a reasonable chance of hitting" (Burt "British Battleships 1919-1945"). They got a hit with bomb 42 (actual dropping height 5,900ft at 280 knots).

The conclusions from these tests were:-
1. All bombs needed to be dropped from at least 5,000ft to be effective.
2. Dropped from 3,000-4,000ft, in practice the bombs only penetrated 2.95-4.75in
3. It was not easy to hit the ship from these heights and certainly not from 5,000ft
4. It was noted that the ship was a stationary target
5. Piercing Nelson's 6" deck had not been easy but it had been pierced.

From the information I have SBD pilots were usually dropping from 1,900-2,500ft altitude.

Very few of the accounts I can immediately put my hands on have much detail of both bomb and drop heights. Looking at some of the action reports for the Battle off Cape Engano in Oct 1944, in one case the Helldivers were carrying 1,000lb SAP or 2x1,000lb AP bombs. Dives were started around 10,000ft, dropping height around 3,000ft and pullout at 2,500ft.

As for the bombs themselves I came across these documents a while ago which may be of interest if you have not seen them before.

 

[Shortround6]

Thank you.

The development of dive bombers (and bombs) has a lot of zig-zags, even in the American and Japanese service.

Both of them had troubles with their intended dive bomber aircraft.
The Japanese D4Y first flew in Dec of 1940 but troubles with both the air frame and the engine delayed things significantly.
The SB2C project started before the Avenger and it's prototype also first flew in Dec 1940.

Speculate if you will on the Pacific war in 1942 if both sides had significant numbers (not total replacement of the older aircraft) at Midway and later.

The Japanese and the Americans were both planning on planes with double the bomb load (in single bombs) of their earlier aircraft and planes with much better ability to penetrate a CAP screen and spend less time within the range of AA guns.

Obviously it didn't turn out that way and the Aichi D3A and the SBD bore the brunt of the dive bomber work until well into 1943.

Trying to bomb modern battleships was hard, you do need AP bombs dropped from altitude. However those ships are not common and the Carriers and Cruisers (the latter being much more common) are vulnerable to smaller/lighter AP or SAP bombs dropped from lower altitudes. Destroyers and transports have no deck armor.

Trouble is with training. The different bombs don't follow quite the same trajectory and need different aiming points, especially if you are trying to drop from the heights the AP bombs need in order to deal with a battleship. Were the pilots "trained" to use the different bombs (not just briefed) or were the drilled using one bomb and approach/technique?

Earlier I mentioned the change in AA.
Extreme examples are things like the USS North Carolina class. They went to the Pacific with 6 quadruple 1.1 guns (upgraded from 4) in late 1942 with an assortment of of .50 cal MG and 20mm. By late spring or summer of 1943 both ships had the 1.1s landed and 10 quadruple 40mm Bofors guns replacing them and by August of 1943 both ships (?) had 15 quad mounts. The .50 cal MGs had pretty much disappeared and the number of 20mm guns were around 50+ to 64. A lot of the ships newer than the North Carolinas got pretty heavy AA batteries to begin with and a number of the older ships saw extensive changes.
The 5in guns were getting an increasing supply of proximity fused projectiles.

The Japanese never saw such extensive upgrades. They tried to do what they could but they didn't have the manufacturing base.

Since the "bomb" was pretty much a ballistic weapon there was no good way to change the attack profile/s. You could fly a bit faster and perhaps the newer, faster planes offered a bit more scope for maneuver on the way out.
Torpedo bombers could and did adapt the torpedoes to higher and faster drop envelopes that gave the TBs a bit better chance of survival than the early war attacks. By late 1944 or 45 the Americans were able to drop from high enough and fast enough that the actual torpedo drops are very difficult to pick out from the other planes firing around.


The British got a bit "lucky" in that they developed airborne radar before anybody else did and this allowed them to attack under the cover of darkness better than some other countries. Certainly not fool proof in the early years and needing skill and training but it did allow tactics that other nations could only use with much more difficulty.

The zig-zags were bad enough, stops and starts in doctrine and training can be even more disruptive.

And some countries were not doing enough testing or relying on guess work and theory a bit too much?

From Wiki so who knows.
"Before the Indian Ocean raid, the established doctrine regarding attack against ships was to arm all D3A1 dive bombers with semi-AP bombs. On 5 April 1942, an IJN carrier force attacked Colombo on Ceylon with half of its complement, while the other half was kept in reserve for strikes against ships. Since a second strike against Colombo was deemed necessary, the dive bombers of reserve force were rearmed from semi-AP bombs to land bombs. When British heavy cruisers were spotted soon afterwards, the reserve force was sent with a portion of D3A1 dive bombers armed with land bombs. In the subsequent attack, land bombs unintentionally proved very effective in suppressing the anti-aircraft fire from the ships. As a result, the doctrine was modified in order to intentionally equip the first few D3A1 dive bombers with land bombs. This new method was already implemented for the attack that sank HMS Hermes just four days later, and continued to be used from then on.[7]"​

Might very well be wrong. I don't know what the Germans and Italians were using in the Med but it may have been an assortment. The damage assessment of the Illustrious tends to say that 3 different sizes of bombs were used from 250kg to 500kg with one 1000kg bomb. The types may also have been mixed. ​

 

[yulzari]

When considering ship borne dive bombers one can see the load being proportional to the engine power, as the decks remain little changed. When the Skua was conceived it had about as much power as one could get off the shelf at the time. As engine grew larger the loads also grew. Different priorities affected individual choices (compare the Dauntless with the Albacore bomb loads against cruising speeds on not vastly different power) but the trend is clear. From 500+lbs under a Skua to 2,000lb under an Albacore. Curiously it stalled by the time of the Fairey Spearfish which carried the same load as the old Albacore on twice the power, albeit faster and further.
Thus one may criticise the Skua's bomb load but it was in line with that which could be carried at the time and compared well with peers. To get more load off the same deck with the same power means more wing area. Hence the biplane choice for TSR types at the time. In many ways the Skua was an attempt to build the smallest airframe around a 500lb bomb for dive bombing using Mercury/Perseus power.

 

[EwenS]

Earlier I mentioned the change in AA.
Extreme examples are things like the USS North Carolina class. They went to the Pacific with 6 quadruple 1.1 guns (upgraded from 4) in late 1942 with an assortment of of .50 cal MG and 20mm. By late spring or summer of 1943 both ships had the 1.1s landed and 10 quadruple 40mm Bofors guns replacing them and by August of 1943 both ships (?) had 15 quad mounts. The .50 cal MGs had pretty much disappeared and the number of 20mm guns were around 50+ to 64. A lot of the ships newer than the North Carolinas got pretty heavy AA batteries to begin with and a number of the older ships saw extensive changes.

The 5in guns were getting an increasing supply of proximity fused projectiles.

The Japanese never saw such extensive upgrades. They tried to do what they could but they didn't have the manufacturing base.

Well here I would distinguish between calibres and numbers of weapons.

The US recognised early on that the 0.5" and 1.1" were inadequate. US production of the 20mm Oerlikon had begun in mid-1941 and the first twin Bofors was produced in Jan 1942 and the first quad in April with the first ship fittings in June/July.

Britain began with 0.5" and 2pdr Pom-Pom (40mm). It had placed orders with Oerlikon in Switzerland for large numbers of 20mm in 1939 but the German advance in May/June 1940 cut off supplies with few delivered. Licence production here took some time to set up and it was late in 1941 before they began to become available in quantity. Licensed production of air cooled Bofors began in Britain pre-war but most went to the Army and only a few to the RN (see PoW late 1941 with a single mount for example). Britain adopted and produced the complex but stabilised and radar equipped Dutch Hazemeyer twin water cooled 40mm from late 1942.

Only Japan did not increase the calibre of its A.A. weapons. It went to war with the 25mm based on a Hotchkiss design and end the same way.

But all navies, including the Japanese increased the numbers of weapons carried. You have mentioned the US but here is the British equivalent
King George V -1940 4xoctuple Pom-pom & 4xUP projectors (rocket batteries)
Anson & Howe - 1942 6xoctuple Pom-Pom & 18 single 20mm
Howe - Sept 1945 8xoctuple & 6xquad Pom Pom, 2xquad & 18 single 40mm Bofors & 4 twin 20mm

And for Japan
Yamato - 1941 on completion 6 twin 5" plus 24x25mm in 8 triple mounts and 2 twin 13.2mm
Yamato - 1945 12 twin 5" plus 162x25mm mostly in triple and single mounts and 2 twin 13.2mm (but after sacrificing 2 of her triple 6.1" turrets)

As well as many more 25mm barrels, Japanese carriers that survived to the latter part of 1944 had their AA armament augmented by 6x28 barrelled AA rocket launchers

Japan 12 cm (4.7") AA Rocket - NavWeaps

www.navweaps.com

But to carry the heavier A.A. armament there were choices and sacrifices to be made.

USA - in larger ships the sacrifice was reduced stability margins not acceptable to the RN. From 1942 destroyers sacrificed sets of torpedo tubes to get 2 twin 40mm. In 1945 the anti-kamikaze AA refits saw the sacrifice of yet more torpedo mounts in early destroyers and even one mount in Fletcher & Sumner classes. Even cruisers up to the Cleveland class were losing one of their two catapults in 1945 to save weight for more AA and radar.

RN - in 1944/45 many cruisers lost a turret to gain additional Pom-Poms and other light AA and aircraft facilities had been removed earlier. As the war went on 0.5" was replaced by single 20mm was replaced by twin 20mm was ultimately replaced by single 40mm

Japan - Yamato I noted above. But even their fleet destroyers were losing a turret to gain more light A.A.

And it was not only light AA but weight for radars and other electronics high up in the ship.

The US proximity fuse programme was inspired by British work begun in 1939 and passed to the US by the Tizard Mission in 1940. Testing took place from early 1942 and it was first used in action by the cruiser Helena on 5 Jan 1943 with her 5"/38 guns. By mid-1944 they were available for a variety of both British & US guns from 3"/50 through to 6"/47. Initial teething problems were largely overcome by 1945. For example, the RN found the batteries in early versions apt to deteriorate quickly in tropical conditions.


Shortround6 said
"The British got a bit "lucky" in that they developed airborne radar before anybody else did and this allowed them to attack under the cover of darkness better than some other countries. Certainly not fool proof in the early years and needing skill and training but it did allow tactics that other nations could only use with much more difficulty."

Getting "lucky" had nothing to do with it. Night flying from carriers had been practiced by the FAA from the mid-1920s, long before radar had even been thought of. It was part of the standard training for FAA pilots. The first radar sets were fitted to Swordfish in early 1941. Too late for Taranto and just in time for the Bismarck. All the Swordfish on Victorious were equipped with ASV.II in May 1941 but only some of those on Ark Royal. Due to technical problems Albacores weren't fitted with it until late in 1941 and only a few had it on Formidable and none on Indomitable in April 1942 in the Indian Ocean during Operation C. That was the reason for the Indomitable borrowing a couple of Swordfish for her air group.

From Wiki so who knows.
"Before the Indian Ocean raid, the established doctrine regarding attack against ships was to arm all D3A1 dive bombers with semi-AP bombs. On 5 April 1942, an IJN carrier force attacked Colombo on Ceylon with half of its complement, while the other half was kept in reserve for strikes against ships. Since a second strike against Colombo was deemed necessary, the dive bombers of reserve force were rearmed from semi-AP bombs to land bombs. When British heavy cruisers were spotted soon afterwards, the reserve force was sent with a portion of D3A1 dive bombers armed with land bombs. In the subsequent attack, land bombs unintentionally proved very effective in suppressing the anti-aircraft fire from the ships. As a result, the doctrine was modified in order to intentionally equip the first few D3A1 dive bombers with land bombs. This new method was already implemented for the attack that sank HMS Hermes just four days later, and continued to be used from then on.[7]"​

I recommend reading Rob Stuart's 6 articles on the Japanese activities in the Indian Ocean in 1942. He is currently the foremost researcher on this, from both British and Japanese sources, and his articles do cover the Japanese bomb loads. I have noted previously that only 6 of the 85 aircraft dispatched to sink Hermes got land attack bombs. That piece of information came from one of Rob's articles.

Articles

Might very well be wrong. I don't know what the Germans and Italians were using in the Med but it may have been an assortment. The damage assessment of the Illustrious tends to say that 3 different sizes of bombs were used from 250kg to 500kg with one 1000kg bomb. The types may also have been mixed. ​

The Germans were using a mix of bombs and when they went after Illustrious & Formidable they did use some 1,000kg bombs on the Stukas. Illustrious suffered one such hit and Formidable 2. You will find details of these and the various damage reports over on the Armoured Carriers website.

Armoured Aircraft Carriers in World War II

Action reports and battle damage for the armoured aircraft carriers HMS Illustrious, Formidable, Victorious, Indomitable, Indefatigable and Implacable in World War II, 1940-1942

www.armouredcarriers.com

But to carry a 1,000kg bomb a Ju87 Stuka had to leave the gunner behind and I believe operate at lighter fuel loads and had a much longer take off run. So they were not an everyday weapon.

Edit:- AIUI the first USN Carrier borne aircraft to go to sea with radar were the TBF-1 Avengers of VT-10 when the parent air group arrived on the Enterprise in Oct 1942. That was with the ASB-1 set roughly equivalent to the British ASV.II.

 

[Reluctant Poster]

My understanding, and I'm certainly amenable to correction, is that the RN pioneered radar-vectoring of carrier-borne fighters, prior to any other navy in the world. If memory serves, one of the lessons the USN picked up from USS Robin was the more efficient use of radar in this mission.

The Royal Navy was a full 2 years ahead of the USN. I have posted this link before in which Commander Taylor describes his experiences in the RN in 1939 and 40

PROCEEDINGS OF THE HART INQUIRY: THIRTIETH DAY

www.ibiblio.org

USN fighter direction was copied from the Royal Navy. To this day the jargon used is what the British taught them.

 

[MikeMeech]

The Royal Navy was a full 2 years ahead of the USN. I have posted this link before in which Commander Taylor describes his experiences in the RN in 1939 and 40

PROCEEDINGS OF THE HART INQUIRY: THIRTIETH DAY

www.ibiblio.org

USN fighter direction was copied from the Royal Navy. To this day the jargon used is what the British taught them.

Hi
Louis Brown's 'A Radar History of World War II, Technical and Military Imperatives', page 371 mentions the introduction of US version of ASV Mk. II and radar fits for carrier aircraft. However, note the last paragraph stating that the USN was four years behind the RAF in introducing VHF radio systems:

Mike

 

[Admiral Beez]

The US air attacks reduced the 4 carriers at Midway to little more than smoking wrecks but they were all still afloat and theoretically could have been saved.

Was Hermes the only carrier at sea sunk only by dive bombers?

List of sunken aircraft carriers - Wikipedia

en.wikipedia.org

Of course, thirty-two dive bombers vs. a CVL without fighter cover will get the job done.

 

[EwenS]

Was Hermes the only carrier at sea sunk only by dive bombers?

List of sunken aircraft carriers - Wikipedia

en.wikipedia.org

Of course, thirty-two dive bombers will get the job done.

Hermes is the only confirmed direct loss to dive-bombers alone. Detailed article on her loss here

Articles

See my post #358 re the Japanese ships. As noted there is doubt about Chitose and whether the 3 waterspouts were from near misses by bombs or from torpedo hits. To me the latter seems a much more likely cause of her loss.

 

[Reluctant Poster]

The big advantage the USN possessed in the SBD was it had a good enough performance to act as a secondary fleet defence 'fighter' which was indeed one of its its secondary roles.
It was more than good enough to tangle with confidence with enemy bombers - and had a good ability to defend itself against fighter types. Its performance in the role was good enough to instil confidence in its pilots to 'have a go'.

Fleet defense was not one of its secondary roles. It was tried as an experiment at Coral Sea. It was not considered to be a sucess and the experiment was not repeated.

 

[Macandy]

Fleet defense was not one of its secondary roles. It was tried as an experiment at Coral Sea. It was not considered to be a sucess and the experiment was not repeated.

Yes, it was such a non secondary role, many pilots felt confident to haver a go as a'fighter' when coming across Japanese aircraft, even willing to mix it with the A6M

 

[Shortround6]

Yes, it was such a non secondary role, many pilots felt confident to haver a go as a'fighter' when coming across Japanese aircraft, even willing to mix it with the A6M

Coming across enemy aircraft is different than being assigned a sector of the air defense.
Like F4Fs will take medium and high altitudes and SBDs will take low altitudes or F4Fs will take a certain arc of coverage of expected enemy routes and the SBDs will take the flank areas to guard against surprises.

Part of the confidence may have been the over claiming in the Coral Sea battle.

 

[Reluctant Poster]

I have found the USN statistics for bombs dropped by size and type. As suspected AP is quite rare

 

[Shortround6]

I would note that the Americans had both a 1000lb AP bomb (MK 33 introduced in Oct 1942) and the famous 1600lb AP bomb (MK 1, Introduced in May of 1942) and the 1250lb AP with rocket assist (Mk 50), introduced (?) was from 1943 but not known if it was actually used.

The line for AP bombs could apply to either of the first two or for both combined.
But yes, the true AP bomb, didn't see very much use.