Swordfish vs Devastator

RCAFson said:

Yes, the USN's ASW Mk 24 'mine', but no air dropped antishipping homing torpedoes, AFAIK.

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The "Fido" or MK 24 "Mine" was in all senses a homing torpedo but I suspect it got called a "mine" because it didn't run a set depth or because of security attempting to keep its existence a secret.

The Germans also used acoustic homing torpedo's the G7es series which came in a versions to home on to merchant ships and escorts (which were likely cavitating). More advanced versions that would do a dog leg around a seductive noise source such as foxer came in to service near the end of the war and there was a wire guided version called spinne (spider). The Germans never air dropped these though.

Acheron said:

I got the impression that torpedo bombers had a harder time hitting a ship compared to dive bombers but if they did, they could deal more damage. Maybe the explosive shock wave of a detonation is more powerful in water?

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There are obviously many types of ship. A battleship like the Bismarck could withstand several hits by torpedo, on the armoured belt. Bismarck was hit 3 times, two damaged it but the third was a lucky strike that crippled the steering. Gneisenau took one repairable hit that gave it a 2 degree list. An Aircraft carrier can be in serious trouble with one bomb penetrating its decks while one bomb or torpedo can sink a freighter or oil tanker.

Elvis said:

Yeah, but isn't that of any kind of bombing scenario?
Without fighter cover, they're just sitting ducks.
I think with torpedo bombing, it becomes a bit redundant, considering one sub can carry a bunch of torpedo and launch multiple strikes simultaneously.
With torpedo bombers, you need a whole squadron, supported by an aircraft carrier, to achieve the same end.
Seems like after Midway, you don't hear a whole lot about Torpedo bombing, although the practice remained though out the rest of the war.

Elvis

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Bombing is more efficient if it can achieve accuracy because you can carry 4 x more explosives. The Luftwaffe started using the "Turnip Planting Method" to get destructive hits on to a ship below the waterline and it kind of was the equivalent of the skip bombing technique the US used. (At one point Europeans worked out how to plant turnips in winter which lead to a massive increase in food production, cows produced milk in winter). The turnip planting method is described in Fleischer's "German Air Dropped Weapons". If done from a Ju 88 the StuVi 5B computing slide/dive bombing sight it used. The bomb is aimed at just ahead of the waterline (the sight computes a continuous impact point into the reflector sight). When the bomb is released it impacts the water and then detonates with a 5.2 second delay which means it blows up about 20m below the ship breaking its back, A direct hit is also useful.
If an Me 109 is used then the pilot calculates the desired dive angle and speed. He sets a second reticule on the Revi gun sight to toss the bomb at the correct angle after a short pullup. He uses the stedometric range finder to pullup and release at the correct angle or an alarm set into the altimeter. The idea was to ultimately use the TSD 2D toss bombing sight which released duing the pullup automatically irrespective of angle or speed or altitude. That sight was being used operationally with evaluation squadrons.

Toss bombing could get a fair amount of stand off distance if released at high speed. The Germans were developing a special type of bomb they called BT or Board Torpedos eg BT700, BT1000 etc with a highly elongated shape that would penetrate and spear under water perhaps 150m. A shock hardened version of the two coil metal detector proximity fuse used in German torpedos post 1942 was to be fitted backed up by impact, time and probably depth fuses.

It was attractive because it could be used from jets and there were even plans to use it on the Me 163 as a pair of BT200 or BT400 under each wing.

There is no way you can use a torpedo from a jet travelling at full speed although torpedo release limits did improve massively.

The Germans did persist in using torpedo's but I think the focus was to be on night attacks. The Ju 188A3 below is carrying a FuG 200 Hohtenweil radar which was widely used on Fw 200 condors and Ju 290and could in theory carry out blind attacks at night You can see 3 aerials, the one in the centre was the transmit aerial and the ones splayed to the left and right are receive aerials. By alternately switching and comparing signals not only could the target be centred but its position could be accurately measured. The bigger aircraft had an array running along the wings to measure for targets out to side as it flew along.



The daylight use of torpedo bombing doesn't seem to have been attractive because it was downright dangerous if the ships had escort carriers around. A variant of the Fw 190D was being developed to carry a torpedo. The latter version of the aircraft probably could have moved at 400mph as sea level and maybe I imagine 10%-15% less (350mph) with. a big torpedo attached That at least gives it a chance to get to the target even if it needs to slow down to 180 knots (200 mph to release) plus the aircraft could of course attack with bombs and use the torpedo to finish of an damaged ship.

Acheron said:

I got the impression that torpedo bombers had a harder time hitting a ship compared to dive bombers but if they did, they could deal more damage. Maybe the explosive shock wave of a detonation is more powerful in water?

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It can be, it depends on the depth of the water. A bomb exploding on the surface (unlikely to explode at the exact surface) of the water has much of it's force dissipated into the air. Much more than 50% because the air offers a path of less resistance than the water does. As the bomb (or torpedo) explodes further beneath the surface more of the force goes into the surrounding water but a fair amount still goes up until you get deeper than most ship hulls.

If the explosion takes place next to the ships hull much of the force is directed against the ships hull as that, depending on it's construction, is the path of least resistance for the explosion.

Note the straight line of the lower edge of the armor plate. a torpedo exploding 15 ft below the surface is trying to lift about 960lbs of sea water per square foot of the explosion area.

Water is technically incompressible but you can put it under a huge amount of pressure. It is not just the shock wave but the venting of the gases generated by the explosion. Which way is the fastest, easiest way for the gases to vent?

Please note that torpedoes for much of the war carried more explosives than common bombs. British 18 in aerial torpedo normally used 388lbs of TNT in the warhead. A British 1000lb GP bomb was around 330lbs of TNT, The 500lb SAP bomb used by the Skua held 90lbs of TNT.

For the US the MK 13 aerial torpedo started with 401lbs of TNT and ended the war with 600lbs of Torpex. American GP bombs held about 50-52% of their weight in explosive.
A near miss by a large bomb could be quite damaging but problem is what is meant by "near" a few hundred feet might as well be a mile.

A single hit by a torpedo could let thousands of tons of water into a ship, and the water could flood vital compartments (like engine rooms or machinery spaces) while a bomb exploding on the deck or even two decks down on a large ship may not let any water into the ship directly. Fires, disruption of fire control equipment, damage to weapons and sighting systems and even damage to machinery could be done by bombs but the bombs needed to be suited somewhat to the ship. Small unarmored ships hit by 500lb Semi AP bombs might wind up with a 12-15in hole right through the ship with no explosion. the same bomb might not make it though the armored deck of a battleship.

I believe the saying goes...

"if you want to let a lot of air into a ship, bomb it, if you want to let a lot of water into a ship torpedo it". Or something like that.

According to Shattered Sword, one of the three bombs that were dropped at Akagi (1,000 pounders I believe), one pierced the either the edge of the flight deck or the gun gallery aft, kept going and exploded either under the rudder(s)/props or next to them. They theorize that the water hammer effect is what put the kibosh on the steering/propulsion and began flooding of the engineering spaces.

Re the Channel Dash, there is no WW2 torpedo aircraft carrier- or land-based of which six could have successfully attacked that fleet in daytime against the whole of JG26 and more. Not Devastator, not Kate, Jill or Grace, not Avenger, Beaufort, Ju-88 or anything else you can think of. That was a suicide mission. It doesn't count as a black mark for Swordfish.

Swordfish, being so slow, had the option to approach higher and dive into its torpedo run, which did not need to be a long run with the RN torpedoes, unlike the Bliss-Leavitt in its early form.

buffnut453 said:

Swordfish had a range of 522 miles with normal fuel and carrying a torpedo. Devastator range was 435 miles with a Mk13 torpedo. Also note the Swordfish could have a long-range tank installed at the expense of the third crewman, which would further increase the range.

Based on these figures, it would seem the Swordfish was appropriate for the Pacific.

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Which would give the Swordfish a combat radius of less than 250 miles - That is an inappropriate range for the Pacific. It's probably a lot less than than Japanese torpedo bombers - which would put a British carrier force at a disadvantage to a Japanese carrier force.

Ovod said:

Which would give the Swordfish a combat radius of less than 250 miles - That is an inappropriate range for the Pacific. It's probably a lot less than than Japanese torpedo bombers - which would put a British carrier force at a disadvantage to a Japanese carrier force.

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So the Devastator, with an even shorter range, is appropriate for the Pacific?

The Kate had a range of 608 miles which isn't a tremendous advantage over the Swordfish...oh, and the Kate couldn't operate as effectively at night due to the lack of radar. Plus radar offers longer detection ranges in poorer weather conditions whereas the Kate capability rests on the "Mk.I Eyeball" enhanced by binoculars. Any Allied carrier force is only at a disadvantage if it is spotted first by the Japanese fleet. Operation of radar-equipped aircraft by the Allied carrier fleet would greatly reduce that risk.

Bottom line is that the Swordfish with radar was a much more capable and dangerous torpedo platform than anything operated by the USN or IJN in mid-1942.

I have found a range carrying a torpedo for the Nakajima B5N2 of 528 nautical miles. Same source gives a range of 454 nautical miles with a torpedo for the Swordfish.

buffnut453 said:

*SNIP*

Bottom line is that the Swordfish with radar was a much more capable and dangerous torpedo platform than anything operated by the USN or IJN in mid-1942.

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I would agree with this with one proviso, adding "at night". I wouldn't give it much of a chance in a daylight attack on Kido Butai.

Peter Gunn said:

I would agree with this with one proviso, adding "at night". I wouldn't give it much of a chance in a daylight attack on Kido Butai.

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With a heavy fighter escort they might have a chance. AA defence of the Japanese navy in 1942 wasn't particularly strong. Still going to have massive losses.

Peter Gunn said:

I would agree with this with one proviso, adding "at night". I wouldn't give it much of a chance in a daylight attack on Kido Butai.

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Agreed.

fastmongrel said:

With a heavy fighter escort they might have a chance. AA defence of the Japanese navy in 1942 wasn't particularly strong. Still going to have massive losses.

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At night? How capable was the IJN fighter force at night operations? How would the IJN defensive fighters locate an attacking formation at night given that the IJN lacked radar and had virtually non-existent fighter control (the latter even in daylight)?

Ovod said:

Which would give the Swordfish a combat radius of less than 250 miles - That is an inappropriate range for the Pacific. It's probably a lot less than than Japanese torpedo bombers - which would put a British carrier force at a disadvantage to a Japanese carrier force.

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The Swordfish could carry a aux internal fuel tank or an aux external tank (in lieu of the torpedo), and this would extend the combat radius. However, as I've stated, it's a bit unfair to compare the Swordfish to the TBD, because the Swordfish had largely been replaced by the Albacore by Midway (June 1942) and both of Somerville's fleet carriers were equipped with Albacores. The Albacore could also carry internal and/or external aux fuel tanks.

buffnut453 said:

At night? How capable was the IJN fighter force at night operations? How would the IJN defensive fighters locate an attacking formation at night given that the IJN lacked radar and had virtually non-existent fighter control (the latter even in daylight)?

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Sorry should have said daylight. Going to be a massacre but at least the torpedo would go bang

fastmongrel said:

Sorry should have said daylight. Going to be a massacre but at least the torpedo would go bang

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Which is precisely why I was recommending the Swordfish operate at night, with the torpedo-carriers led by a radar-equipped Swordfish.

pbehn said:

There are obviously many types of ship. A battleship like the Bismarck could withstand several hits by torpedo, on the armoured belt. Bismarck was hit 3 times, two damaged it but the third was a lucky strike that crippled the steering. Gneisenau took one repairable hit that gave it a 2 degree list. An Aircraft carrier can be in serious trouble with one bomb penetrating its decks while one bomb or torpedo can sink a freighter or oil tanker.

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You can damage or cripple an aircraft carrier or battleship with dive bombers, but to sink them you need to let the water in, and that needs torpedoes. IIRC, no carrier was ever sunk by dive bombers.

Admiral Beez said:

You can damage or cripple an aircraft carrier or battleship with dive bombers, but to sink them you need to let the water in, and that needs torpedoes. IIRC, no carrier was ever sunk by dive bombers.

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HMS Hermes (and several other ships) was sunk by D3As on 9 April 1942.
IJN Ryujo by SBDs on 24 August 1942.
USS St. Lo was sunk on 25 October 1944 by an A6M2 Kamikaze that dove on it, the 1,000 pound bomb penetrating belowdecks. Not a dedicated dive-bomber, granted, but the execution and results are comparable.
IJN Zuiho's loss on 24 October 1944 was credited to attacks by SB2Cs.

Also, if a carrier is damaged beyond saving by dive-bomber and has to be scuttled as a result, which happened to a quite a few carriers during the course of the war, then they have accomplished their objective.

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