Why the Skua Only Carried a 500lb Bomb

[RCAFson]

The Taurus had several problems and in early days was quite unreliable in the Beuaforts. Solved by changing the crankshaft clamping method. However that left the cooling problems.
They "fixed" those enough to make it reliable at very low altitude. 1130hp at 3,500ft using 100/130 fuel from a 1330lb engine was a very average return on investment.

We have to remember that the Taurus had a displacement of 1550in3 versus 1830in3 for the R-1830. Additionally, the early variants of the R-1830 (and R-1820) had their own fair share of reliability problems, and these delayed the F4F's own development and acceptance into service; This allowed the F2A to get the first USN contract for a monoplane carrier fighter. By 1942 when both designs were reasonably developed, the Taurus XII had a TO power of 1090hp and a static war emergency rating of 1130hp at 3500ft versus 1200hp for the R-1830-86 at TO and a military rating of 1135hp at 3400ft/1150hp at 11500ft. The low altitude engine rating was also a function of the Albacore's intended role as a low altitude strike aircraft.

 

[Shortround6]

We have to remember that the Taurus had a displacement of 1550in3 versus 1830in3 or the R-1830.

That was the advantage of the two American engines. They didn't have to be 'tricky'. P&W had make an R-1535 (after they made the first R-1830s) because the navy wanted a small dimeter engine for good pilot view. Turns out the commercial market wasn't interested in it. It was too big for single engine private/commercial planes and two small for twins where they didn't care as much about the view from the cockpit as the engines were out on the wings and they wanted more power for planes like the DC-2/3 anyway. Army didn't want it either, they weren't lading on carrier decks.

Additionally, the early variants of the R-1830 (and R-1820) had their own fair share of reliability problems, and these delayed the F4F's own development and acceptance into service; This allowed the F2A to get the first USN contract for a monoplane carrier fighter.

Yes a lot of the early versions weren't very good but the two American companies kept developing them. Bristol just updated them enough to sell them while they poured money into the sleeve valve hole. The Wright engine dates back to the R-1750 of the late 20s and the first R-1820 came out in 1932. There were a number of radically different R-1820 engines with few, if any, interchangeable parts. Same for the R-1830 but not quite as many changes. Again, they were not quite running in parallel. The Buffalo got a production contract for 54 planes (June 11, 1938) well before the XF4F-3 (ordered 10/1938) showed up with the two stage engine, the XF4F-2 used a single stage/single speed engine. The engine in the F2A-1 didn't even use a reduction gear for the prop. That meant it could be light. They could shoe horn the next R-1820 into the Buffalo, they could not stuff the R-1830 in without more work. (several hundred pounds heavier)
Now during the early to mid 30s both Wright and P & W used externally lubricated valve gear. They both not only fully enclosed the valve gear but changed to using the engine oil to lubricate the valve gear. No grease guns or pulling the rocker boxes and putting oil on cloth pads/wicks every so many hours. Wright was using two speed single stage engines several years before P & W. There was a lot of back and forth. The US also moved to higher octane fuel ahead of the British, I am talking about 91 and briefly 95/96 before the US 100 octane fuel came out which did help the US engine makers some what.

Taurus XII had a TO power of 1090hp and a static war emergency rating of 1130hp at 3500ft versus 1200hp for the R-1830-86 at TO and a military rating of 1135hp at 3400ft/1150hp at 11500ft.

The R-1830 never got a war emergency rating, unless it was very late in the war. However even if we throw out the R-1830-86 with it's two stage supercharger the R-1830 that was showing up end of 1940 (and was later used the Australian Beauforts) was good for 1200hp for take off, 1200hp/2700rpm at 4900ft, 1050hp/2700rpm at 31,000ft 5 min rating and 1100hp/2550rpm at 6100ft, 1000hp/2550rpm at 1250ft, max continuous. with a single stage, two speed supercharger, granted it was about 150lbs heavier than the Taurus. R-1830 development pretty much stopped at this point while the work on the R-2800 took over (and the R-2000) , In 1944 they started using some trickle down stuff from the R-2800 like new cylinders with improved cooling fins and that let them get 1350hp at very low altitudes.

The low altitude engine rating was also a function of the Albacore's intended role as a low altitude strike aircraft.

It is also an admission that the engine either won't make power at altitude or won't cool properly at higher altitude or both.

You can plot on engine on graph and run a line from it's peak power (full throttle height) up to about 55,000ft where it will be zero power and back done to sea level to what the engine will give you if you could use full throttle at sea level. This may not be exact but it is close enough for estimates. The R-1830 had problems of it's own. The two stage supercharger improved things but in high they usually didn't let them run it at 2700rpm for military power. They kept it at 2550rpm. The engines in the B-24s were allowed to use 2700rpm. There are a few differences, one was that the B-24 engines may have had larger intercoolers and the engines intake air was cooler, the other thing was that the engine was wasn't working quite as hard. The turbo is powering the aux supercharger. If you want to use 2700rpm in the mechanical two stage supercharger and go for 1100 hp or so instead of 1000hp the engine was trying to make over 1200hp in cylinders to power the supercharger with the higher heat. They tried to use 2700rpm limit it tests but they didn't much difference is power/speed and they gave up. Maybe they need more cooing fins? maybe they needed better intercoolers? The two stage engine was better than the single stage but it wasn't as good as the Merlin two stage set up.

getting back to the Taurus, an 1130hp engine at 3500ft is going to loose at least 20% of it's power when it hits 13,500ft. Yes you can change the supercharger gear but now you have the classic trade off, more power going to the supercharger and a hotter intake charge temperature which means less power for take-off and at low altitude. And you are not going to get 1130hp at 13,000ft.

 

[RCAFson]

That was the advantage of the two American engines. They didn't have to be 'tricky'. P&W had make an R-1535 (after they made the first R-1830s) because the navy wanted a small dimeter engine for good pilot view. Turns out the commercial market wasn't interested in it. It was too big for single engine private/commercial planes and two small for twins where they didn't care as much about the view from the cockpit as the engines were out on the wings and they wanted more power for planes like the DC-2/3 anyway. Army didn't want it either, they weren't lading on carrier decks.

Yes a lot of the early versions weren't very good but the two American companies kept developing them. Bristol just updated them enough to sell them while they poured money into the sleeve valve hole. The Wright engine dates back to the R-1750 of the late 20s and the first R-1820 came out in 1932. There were a number of radically different R-1820 engines with few, if any, interchangeable parts. Same for the R-1830 but not quite as many changes. Again, they were not quite running in parallel. The Buffalo got a production contract for 54 planes (June 11, 1938) well before the XF4F-3 (ordered 10/1938) showed up with the two stage engine, the XF4F-2 used a single stage/single speed engine. The engine in the F2A-1 didn't even use a reduction gear for the prop. That meant it could be light. They could shoe horn the next R-1820 into the Buffalo, they could not stuff the R-1830 in without more work. (several hundred pounds heavier)
Now during the early to mid 30s both Wright and P & W used externally lubricated valve gear. They both not only fully enclosed the valve gear but changed to using the engine oil to lubricate the valve gear. No grease guns or pulling the rocker boxes and putting oil on cloth pads/wicks every so many hours. Wright was using two speed single stage engines several years before P & W. There was a lot of back and forth. The US also moved to higher octane fuel ahead of the British, I am talking about 91 and briefly 95/96 before the US 100 octane fuel came out which did help the US engine makers some what.

The R-1830 never got a war emergency rating, unless it was very late in the war. However even if we throw out the R-1830-86 with it's two stage supercharger the R-1830 that was showing up end of 1940 (and was later used the Australian Beauforts) was good for 1200hp for take off, 1200hp/2700rpm at 4900ft, 1050hp/2700rpm at 31,000ft 5 min rating and 1100hp/2550rpm at 6100ft, 1000hp/2550rpm at 1250ft, max continuous. with a single stage, two speed supercharger, granted it was about 150lbs heavier than the Taurus. R-1830 development pretty much stopped at this point while the work on the R-2800 took over (and the R-2000) , In 1944 they started using some trickle down stuff from the R-2800 like new cylinders with improved cooling fins and that let them get 1350hp at very low altitudes.

It is also an admission that the engine either won't make power at altitude or won't cool properly at higher altitude or both.

You can plot on engine on graph and run a line from it's peak power (full throttle height) up to about 55,000ft where it will be zero power and back done to sea level to what the engine will give you if you could use full throttle at sea level. This may not be exact but it is close enough for estimates. The R-1830 had problems of it's own. The two stage supercharger improved things but in high they usually didn't let them run it at 2700rpm for military power. They kept it at 2550rpm. The engines in the B-24s were allowed to use 2700rpm. There are a few differences, one was that the B-24 engines may have had larger intercoolers and the engines intake air was cooler, the other thing was that the engine was wasn't working quite as hard. The turbo is powering the aux supercharger. If you want to use 2700rpm in the mechanical two stage supercharger and go for 1100 hp or so instead of 1000hp the engine was trying to make over 1200hp in cylinders to power the supercharger with the higher heat. They tried to use 2700rpm limit it tests but they didn't much difference is power/speed and they gave up. Maybe they need more cooing fins? maybe they needed better intercoolers? The two stage engine was better than the single stage but it wasn't as good as the Merlin two stage set up.

getting back to the Taurus, an 1130hp engine at 3500ft is going to loose at least 20% of it's power when it hits 13,500ft. Yes you can change the supercharger gear but now you have the classic trade off, more power going to the supercharger and a hotter intake charge temperature which means less power for take-off and at low altitude. And you are not going to get 1130hp at 13,000ft.

I don't disagree with any of the above, but the Taurus, as stated, only had a single stage, single speed supercharger. It had nearly 20% less displacement and weighed less. I think it's important that we all understand this when we compare the two engines.

 

[Reluctant Poster]

In the Taurus' favor is that it had the same bore as the Sabre and that allowed Bristol's sleeve valve technology to adopted by Napier.

 

[marathag]

I don't disagree with any of the above, but the Taurus, as stated, only had a single stage, single speed supercharger. It had nearly 20% less displacement and weighed less. I think it's important that we all understand this when we compare the two engines.

Let's look at another small engine derived from the 'crude' American Tech, the Japanese Sakae from Nakajima, here the early Ha 35-11
It's based off Pratt&Whitney design theory, pushrod and poppet valves from the Hornet and Wasp families

Using wiki layout, but info from the wiki of Japan for the earlier engine

General characteristics

• Type: 14-cylinder air-cooled two-row radial engine
• Bore: 130 mm (5.1 in)
• Stroke: 150 mm (5.9 in)
• Displacement: 27.86 L (1,687 in³)
• Length: 1,472 mm (58 in)
• Diameter: 1,150 mm (45 in)
• Dry weight: 530 kg (1,166 lb)

Components

• Valvetrain: Overhead valve
• Supercharger: Gear driven, single stage, single speed. 280mm(11") impeller dia
• Fuel system: updraft 2 BBL Float Carb.
• Fuel type: 92 Octane
• Cooling system: Air-cooled

Performance

• Power output:Takeoff 986HP@2550rpm/Nominal 967HP@2500rpm
• Specific power: 0.58 hp/in³
• Compression ratio: 6.7
• Power-to-weight ratio: 0.758 hp/lb

What was this early Sakae? Small diameter, compact, light weight, and Reliable as it wasn't spinning at crazy high RPMs like the Taurus. Later version went to two speed blower, higher C/R and RPMs to 2700 where is retained decent power at altitude

 

[Geoffrey Sinclair]

Well, in theory. In practice, I've seen no realistic (deep load) performance metric for the Iowa class that gives them more than a fraction of a knot over the South Daks. All you really get for 25% more hull-length and 60% more horsepower is a pretty ship.

The Iowa class were, as advertised, several knots faster than the 35,000 ton battleships. The USN wartime fleet, Essex, Baltimore, Cleveland class were all designed for 33 knots, generally made that and the Iowas could keep up.

Times below are when the RAF began use in production types,

Perseus sleeve 24.9 litre, around in the mid 1930's, the 1937 Vildebeeste IV Incidentally there were 17 of them, not 18. Engine stayed in production until May 1942. The Skua and Roc were 1938/39, the Lysander II 1938/40 the Botha 1939/42. Around 700 Bothas were cancelled, starting in 1940.

I have no information why the Lysander II switched engines. It could be the plan, it could be the increase in Blenheim orders, coupled to the delays in Botha and Albacore production. The change from Lysander mark I to II was in December 1938, the last mark II in May 1940, the first mark III in June 1940, and there was a batch of 68 mark I May to July 1940. Then comes the Canadian built ones, 75 mark II September 1939 to April 1941 then 150 mark III in 1942.

Taurus sleeve 25.4 litre, around in the late 1930's. Stayed in production to August 1943. Used in the Beaufort 1939 to end 1944, Albacore 1939 to end 1942
Hercules sleeve 38.7 litre
Centaurus sleeve 53.6 litre

Pegasus poppet 28.7 litre, around early 1930's. As per the 1932 Westland Wallace. Stayed in production until September 1943, given use in Swordfish and Sunderland.

Mercury poppet 24.9 litre, around mid 1930's, in the 1934 Gloster Gauntlet, Stayed in production until October 1944. The Miles Martinet went out of production in May 1945, the Queen Martinet in August 1946. A month after the end of Sea Otter production.

From the above it looks like Bristol made a decision in the early 1930's to offer both types of engines. Britain like everyone found it easier to expand airframe than engine production, which played a part in what engines were fitted to what aircraft, and while we know of the various engine cancellation decisions there were also the ones to limit production and the changes when various aircraft were ordered or cancelled. The understood technology Pegasus and Mercury became the standard engines for the 900-1,000 HP sort of output, the Perseus seems to have been the loser, probably hastened by the Taurus problems and that it had the lowest production numbers but more probably as its major customer was a failure, the Botha, and known to be so in 1940, while its second customer, the Albacore, was not a great success and was due for replacement by the Barracuda "soon". The RN was a big victim of 1940, delaying its next generation of aircraft.

Production June to December 1939 1,682 Mercury, 972 Pegasus, 71 Hercules, 389 Perseus, 143 Taurus
Production in 1940, 3,733 Mercury, 3,579 Pegasus, 636 Hercules, 807 Perseus, 1,046 Taurus

The Sea Otter was partly the victim of the Walrus success but also of the early war shock to the British production system, 3 built January to July 1943 then series production began, all up 28 built in 1943, Walrus production ending in January 1944. Sea Otters were built until July 1946, not surprisingly there were large numbers of cancellations in 1945. The RAAF, which had been responsible for the Walrus design evolving out of the Seagull, had placed an order for the Sea Otter "S12/40" to replace its diminishing stocks, as of end 1941 it was reported production was expected in early 1943. Later that became in 1943, and by early 1943 it was "Aircraft not expected to be produced in quantity until 1945." In September 1943, the until 1945 became until early 1946. In October 1944 the order is no longer reported in the Chiefs of Staff reports.

RAF Squadrons has the Sea Otter arriving at 276 squadron on February 1944, 277 squadron in November 1943, 278 squadron in May 1945, 279 squadron in July 1945, 281 squadron in May 1945, 282 squadron in March 1945, 292 squadron in November 1944.

 

[RCAFson]

Let's look at another small engine derived from the 'crude' American Tech, the Japanese Sakae from Nakajima, here the early Ha 35-11
It's based off Pratt&Whitney design theory, pushrod and poppet valves from the Hornet and Wasp families

Using wiki layout, but info from the wiki of Japan for the earlier engine

General characteristics

• Type: 14-cylinder air-cooled two-row radial engine
• Bore: 130 mm (5.1 in)
• Stroke: 150 mm (5.9 in)
• Displacement: 27.86 L (1,687 in³)
• Length: 1,472 mm (58 in)
• Diameter: 1,150 mm (45 in)
• Dry weight: 530 kg (1,166 lb)

Components

• Valvetrain: Overhead valve
• Supercharger: Gear driven, single stage, single speed. 280mm(11") impeller dia
• Fuel system: updraft 2 BBL Float Carb.
• Fuel type: 92 Octane
• Cooling system: Air-cooled

Performance

• Power output:Takeoff 986HP@2550rpm/Nominal 967HP@2500rpm
• Specific power: 0.58 hp/in³
• Compression ratio: 6.7
• Power-to-weight ratio: 0.758 hp/lb

What was this early Sakae? Small diameter, compact, light weight, and Reliable as it wasn't spinning at crazy high RPMs like the Taurus. Later version went to two speed blower, higher C/R and RPMs to 2700 where is retained decent power at altitude

I'm not really sure where we're going with this, but the Ha 35-11 has ~8% less power and ~10% more displacement than a Taurus II/87 oct. I doubt it would have been suitable as a replacement for the Taurus II.

 

[planespotting]

You have done a nice job of going through some of pathways. Some of which are nearly incomprehensible to some of us today.

I'm glad you find it worth replying to, but I know what you mean about "nearly incomprehensible"!!

Fedden and his fixation on the sleeve valve seem to had had a very large hand in this. Apparently there is no surviving accounting of the cost of the various engines in either pounds Sterling or man-hours. Fedden had nearly bankrupted the company by the time the sleeve valve engines were a viable product. Please note there were two phases of this so some accounts are a little unclear. First phase was just getting the Perseus into production.
View attachment 717640
Visually this was a look into the future for British radial engines, at least it used a long cord cowl. However it seems the Pegasus was not quite ready for prime time. This has to be seen in context as the the other main contender, the Armstrong Siddeley Tiger was sliding into obsolescence.
From Wiki so...............
"The Mark IV introduced the much more powerful 825 hp (615 kW) Bristol Perseus sleeve valve radial engine enclosed in a NACA cowling which significantly improved performance, increasing maximum speed to 156 mph (251 km/h) and rate of climb to 840 ft/min (4.3 m/s).[7] In this version, the Perseus had overheating problems and was deemed unsuitable for tropical service[8] with production limited to 18 aircraft, all of which served with the home based squadrons"

When I was trying to find out if there's any information on the original narrow-body fuselage design for the Botha (there isn't!), google bounced me up a remark saying that the Perseus struggled with dust as well...

The Perseus went through 4 or 5 different cylinders with increasing fin area from 1932 to 1940.
The 2nd phase was 1939-40 with the Perseus in large scale production and the Hercules (using the same cylinders) also going into large scale production. This is when they discovered that they could not make the sleeves stay round in mass production and the engines (mostly Hercules?) were using excessive oil in as little as 20 hours of operation.

The main demand for the new designs down to 1940 seem to have been for the Persus, principally the Botha, which used nearly 1200 engines in total, but I've not found when their production-run was complete; the only other significant early number was for the Lysander, with about 500 Perseus-engined airframes down to August 1940, with the Skua and its turret-fighter variant taking another 300-odd in the same timeframe; by contrast, the Hercules seems to have only flown in very limited numbers at first, with the four-engined short S.26 flying-boat, of which just three were built, and about twenty of the twin-engined Saunders-Roe Lerwick, which between them account for around fifty motors...

The first really serious Hercules production is for the Beaufighter, which starts deliveries in July/August 1940, but even this needs no more than 200-odd engines in 1940 (the hundredth Beau completed in December '40 and that presumably includes some early Mk. IIs with Merlins), and rather less than 2000 engines by the end of 1941 (there are less than 1000 Beau Mk. Is in total, though I can't find precise dates, and some percentage of them are likely later); the Short Stirling only runs to a handful of machines in 1940, and around a hundred and fifty in 1941: total Hercules numbers across the two types from mid-1940 to end 1941, a maximum of about 2500, don't seem out-of-step with the 2000-odd Perseus motors in a comparable period 1939-1940...

Hercules machines only seem to really kick in around 1942, and then they really kick in, with the Beaufighter Mk. VI, the Armstrong-Whitworth Albermarle, and the engine swapped onto the Wellington, the Halifax, and even a few hundred Lancasters, with a total of maybe 40k motors on these types by 1945, which makes even Mercury production in '37-'41 look rather modest, and then after that it's on a whole range of British and French cargo types...

I wouldn't be completely surprised if there was a hard-swap around August 1940 from serial production of the Perseus to the Hercules, but for whatever reason, it seems to be 1942 when things get going...

They were also realizing that 900hp engines were not actually going to power war winning aircraft. Why this was so surprising is a little hard to figure out. The Sleeve valve program at Bristol was always a little behind the curve. The backwards Americans were building 30 liter engines that made 900hp in the mid 30s when the Pegasus was struggling to make 800hp. By 1940 the American engines were making 1000-1100hp (the American 1200hp was pretty much sea level for take-off). Less said about the Aquila the better, The Americans were using engines of that size to power trainers in tier below the AT-6.
The British were forced to keep making Mercuries because they didn't have much else. They needed the Pegasus cylinder production to make Hercules engines. They had only made about 4-5 of Aquila engines despite all the press. And the Taurus was another lost cause. 5/6th size of twin wasp, over heating problems as it was and the sleeve valves didn't like high boost (high cylinder pressures) left few, if any, options.

Basically the engines didn't make enough power and no amount of fooling around with skinny fuselages was going to solve that. They were building Blenheims by the hundreds and they should have had a pretty good idea of what kind of power they needed to get the desired performance from a plane of that size. Clip the wing, take the turret off, fair the wheels over. See what it actually took instead of assuming that sleeve valves were going magically sprinkle unicorn poop on the aircraft they were dreaming up and take them to next level of performance.

I'm prone to defending faintly absurd causes like the viability of a narrow-body Blackburn Botha (obviously, removing that appalling dorsal-fuselage drag-brake with the Lewis guns in it would help too; "would be significantly improved by the turret off the Defiant/Roc" is not something you can say about that many aircraft), and more generally I have an amateurish sense that smallish radials might make more sense in pairs than they do individually, but you're not wrong; the question is, why were they wrong?

1. Presumably they thought drag was prohibitive on a big blunt radial - it's quite puzzling reading narratives surrounding the Short S.30 that emphasise the minimal diameter of the NACA cowling on the Perseus, which suggests they didn't really understand what it could do...

2. Was there some perceived advantage in cruising range? The RAF seems to have emphasised an economical trog at 10,000ft, and they thought - rightly or wrongly - that the Perseus would be more able to heft freight cargo across the Atlantic than the Pegasus...

This is probably the best data on Iowa speeds that exists
http://www.navweaps.com/index_tech/tech-003.php#:~:text=Iowa's%20Speed,to%20perform%20measured%20mile%20tests.

During Operation Hailstone (the raid on Truk in Feb 1944) Iowa and New Jersey were reported as running at 30 knots while chasing escaping Japanese ships.

www.navweaps.com/index_tech/tech-029.php

Note how big an increase in shp is required to raise the speed of the vessel from around 25-26 knots to about 30 knots. Providing that extra power alone means a bigger ship.

Subsequent trials in the 1980s seem to verify that the Iowas were capable of 32.5 knots at 212,000shp at near full load displacement of 56,900 tons.
www.navweaps.com/index_tech/tech-104.php

The thing that is usually forgotten is that in WW2 ALL 10 US fast Battleships spent the majority of their time from mid-1943 onwards as escorts to the carrier groups. From mid-1943 new procedures were laid down covering the operation of these groups. Operating speeds were in the range 15-25 knots and the whole task group would generally manoeuvre as a single entity. If a carrier needed to operate its aircraft outwith a normal planned operating sequence, either the whole group would alter course and speed or the individual carrier would manoeuvre as far downwind as possible while remaining within the screen of escorting destroyers. It would then operate as fast as necessary to launch/recover aircraft before taking up its designated position in the TG again, all the while remaining within the destroyer screen.

For that reason an Iowa was bound to be operating at the same speed as a North Carolina or South Dakota for the vast majority of its time at sea.

Aye, I'm aware it takes an awful lot of extra horsepower to brute-force even a small speed increase out of a big ship that's trying to power through the water it's piling up in front of it - the approximate equivalent of transonic drag in aviation; but while some ships did get something out of lean proportions and/or big boilers, I've not seen any evidence the Iowa class was one of them...

The claim of over thirty knots in 1944 was based on the bridge speedometer - an unreliable instrument, especially at high speeds; this is the equivalent of IAS on an aircraft...

In 1985, as the article notes, what was actually achieved on trials was just under 29½ knots at a little over 140,000 shp; this was combined with an (unreliable, unspecified) bridge speedometer reading from an earlier engine-power trial which had reached over 185,000 shp, which was then adjusted, based on the (questionable) assumption that you could calibrate it by scaling 140,000 shp to 29½ knots, to give a (theoretical) speed of 31 knots at around 185,000 shp; the numbers thus produced were then adjusted again for a (theoretical) maximum output of 212,000 shp; this is an old-established technique for estimating theoretical maximum speeds for capital ships. The only real number here is 29½ knots.

A good example, because it's entirely explicit, is provided by the 1916 "large light cruisers", which happen to be favourite ships of mine; Courageous reported a speed on her sea trials of just below 31 knots, perhaps measured by the ludicrously unreliable old-fashioned method of throwing a log on a string off the back of the ship and seeing how fast the rope payed out; this unreliable result was achieved off what was said to be just over her notional 90,000 shp design power, and more certainly at a little over 22000t displacement and 25'8"ft draft, and on this basis she was allowed to be capable of 32 knots off 110,000 shp overload power at her design parameters of 19000t and 22'8", in order to say that the engines met the official performance requirements - though these were all unrealistic figures for the ship as-built; without derailing the discussion with more detail, the only clearly reliable figure for the type I've seen is a fraction above 30kts on the measured mile, and with a length:beam ratio of 9:1 and a deep-load draught of scarcely 25ft, these are the most innately streamlined capital ships to ever swim...

Similar examples can be multiplied - typical giveaways are the quoting of design displacement/draft figures rather than as-built ones, which imply that the speed has also been adjusted, or results based on power trials rather than speed trials, where it's sometimes obvious that design power is being artificially assumed to produce design speed and maximum overload is being attributed a scaled-up rate of knots...

In practice, there seems to be a fairly consistent "wall" for real speeds for battleship-shaped ships around 29½ knots, as that's where practical trials reports for pretty much all the WW2 types max-out regardless of length/beam ratio, horsepower and draught; I'm prepared to believe that one or two might have done a little better, more from hull configuration than power (e.g. the Italian Littorio class at their very light trials draught/displacement, and HMS Vanguard with her big forecastle and transom stern); but even those numbers I'm wary of, as they simply lack obvious artifice, and I've not seen anything reliable for the Iowa class...

This isn't to say I'm an expert! As with anything I say here, you should consider me as towing a large gunnery target...

Ordered as an Amphibian Boat Reconnaissance aircraft for the FAA, Supermarine couldn't build them in 1940 due to demand for Spitfires. Production had to wait until new contracts were placed with Saunders Roe in Jan 1942 with the first production aircraft flying in Jan 1943.

Wikipedia mentions an earlier contract with Blackburn that was issued in 1940 and cancelled in 1941, information it says comes from a 1981 history of Supermarine; supposedly that was to do with airframe capacity, but the intended Perseus engine wasn't in production after August 1940 for anything except perhaps the Blackburn Botha (and I say perhaps because I'm simply not sure when production was done there); or was it the other way up, and the Sea Otter was an attempt to find a use for Perseus engine-manufacturing capacity?

But their first operational service was with the RAF in the Air Sea Rescue role from Nov 1943, alongside many aircraft types including the Walrus. When the FAA began to form squadrons on the Sea Otter in Nov 1944 it was again in the Air Sea Rescue role. Immediately postwar one squadron used them minespotting in the clear waters of the Med.

Postwar each RN carrier generally had one, again for Air Sea Rescue duties. That continued until the Korean War when they were replaced by Westland Dragonfly helicopters.

Fascinating. ASR makes sense as a main role at that date... I simply hadn't really realised how much the Sea Otter was used like that, and of course it does make a little flying-boat relevant; but I'm pretty sure it wasn't designed primarily for that role...

Incidentally, the FAA began removing the catapult flights from its cruisers from late 1942 / early 1943. As a measure of the speed with which that happened 700 squadron, responsible for training crews and managing individual flights, reduced from 63 aircraft at its peak in June 1942 to just 20 in July 1943. Amongst the very last catapult flights were the Curtiss Kingfisher flights on Emerald and various AMCs in spring 1944. Blame radar and the fact that the role of the cruiser changed from patrolling the sea lanes (something taken over by long range flying boats and land based aircraft) to escorting the fleet. The hangar space freed up was used for a lot of purposes, not just cinemas, on pre-war designed ships whose crews had increased dramatically with all those new electronic devices and much heavier AA armaments.

Oh, definitely because of radar. The cinema on HMS Renown is just a symbol of the way the whole midships floatplane aparatus on RN capital ships was suddenly no longer needed...

Though the cruisers did continue to be used on patrol until 1944 - with several of the Italian co-belligerents taking up the South Atlantic slack; I'd guess that Emerald - which still had an old-fashioned charthouse and topmast, not a tower bridge - simply didn't have much useful space for radar, her Kingfisher presumably being because she wasn't really designed for anything as hefty as a Walrus or an Otter (she seems to have used a Seafox with the rest of the smaller RN cruisers until they went out of style)...

The USN retained its floatplanes on cruisers and destroyers right to the end of the war and beyond (around 1948 IIRC). In June 1942 it issued a requirement for a new "observation seaplane". That became the Curtiss SC-1 Seahawk. A production order was issued in June 1943 and the first flights went aboard the USS Guam in Oct 1944.

Compare the IJN's active enthusiasm for replacing half the guns on battleships and heavy cruisers with a seaplane deck, which makes more sense when you realise they've become a search-radar platform, and the reduction in main armament is practical because the fire-control radar removes the need for large randomized salvos...

The RN's contrasting rejection of the floatplane is, therefore, the more curious decision; obviously they'd found masthead radar more useful than the Walrus in the Bismarck chase in North Atlantic conditions, and as you say they'd expended the effort on convoy shadowing so they generally had shore-based overflight, but carriers also seem to be more integrated with their capital ships (to the extent that Cunningham literally had Formidable in the battle line at Cape Matapan), so perhaps they don't perceive the need to give a battleship force a large screen of seaplane radar pickets sans carrier in quite the same way...

... because their carriers are providing the battle squadron radar pickets...

And (thinking out loud) this might suddenly make sense of the peculiarly large two-seater carrier-fighters the Fleet Air Arm is getting. The Fulmar is, perhaps, designed in anticipation of ASV, though in the end, of course, it inevitably ended up being flown by the Swordfish instead...

Yes. Aircraft would lose lots of speed in dogfights, and/or lose altitude to convert potential energy into kinetic energy (speed).

Aircraft coming out of dogfights were vulnerable because they were slow. Not only were they easy targets for slashing attacks, the maximum Gs that you can pull depends on your speed (and air density, and is limited by structural strength or the pilot blacking out, etc., etc.).

That certainly explains the limits of the Skua, if the airframe simply wasn't able to stay flying at the speeds it would need to drop to during combat, and was going to suddenly fall sideways out of the sky mid-manoeuvre...

That was the advantage of the two American engines. They didn't have to be 'tricky'. P&W had make an R-1535 (after they made the first R-1830s) because the navy wanted a small dimeter engine for good pilot view. Turns out the commercial market wasn't interested in it. It was too big for single engine private/commercial planes and two small for twins where they didn't care as much about the view from the cockpit as the engines were out on the wings and they wanted more power for planes like the DC-2/3 anyway. Army didn't want it either, they weren't lading on carrier decks.

I'd never thought that the Skua's nose configuration might be seen as an advantage for the cockpit view. I'm not sure I want to think that it was designed that way deliberately...

 

[marathag]

I'm not really sure where we're going with this, but the Ha 35-11 has ~8% less power and ~10% more displacement than a Taurus II/87 oct. I doubt it would have been suitable as a replacement for the Taurus II.

That was the early engine for IJA and IJN, but replaced by the -21 in 1940, with two speed blower, slightly increased compression and RPM that's on the main Sakae wiki page Taurus II values in Red

This-21 Sakae on 92(87) Octane and 2700(3225)rpm, for 1300(1301) pound engine weight.

Performance

• Power output: 842.64 kW (1130hp) at altitude(1050hp)
• Specific power: 30.2 kW/L (0.66 hp/in³) 30.83 kW/L (0.68 hp/in³)
• Compression ratio: 7:1 (7.2:1)
• Power-to-weight ratio: 1.428 kW/kg (0.869 hp/lb) 1.33 kW/kg (0.81 hp/lb)

So still has 10% more displacement. Same power at SL, better at altitude

But has reliability, and can perform at 24,000 feet. Easy to build, important given Japan's Industrial situation.

Simple, robust, easy to make

That's what you want for radial engine, not one that tweaked to be on the edge of reliability, and hard to manufacture.

More Displacement is the easy way to more power

 

[RCAFson]

That was the early engine for IJA and IJN, but replaced by the -21 in 1940, with two speed blower, slightly increased compression and RPM that's on the main Sakae wiki page Taurus II values in Red

This-21 Sakae on 92(87) Octane and 2700(3225)rpm, for 1300(1301) pound engine weight.

Performance

• Power output: 842.64 kW (1130hp) at altitude(1050hp)
• Specific power: 30.2 kW/L (0.66 hp/in³) 30.83 kW/L (0.68 hp/in³)
• Compression ratio: 7:1 (7.2:1)
• Power-to-weight ratio: 1.428 kW/kg (0.869 hp/lb) 1.33 kW/kg (0.81 hp/lb)

So still has 10% more displacement. Same power at SL, better at altitude

But has reliability, and can perform at 24,000 feet. Easy to build, important given Japan's Industrial situation.

Simple, robust, easy to make

That's what you want for radial engine, not one that tweaked to be on the edge of reliability, and hard to manufacture.

More Displacement is the easy way to more power

Manufacturers specs for the Taurus II as quoted by Lumsden (page 290) was 1060hp/TO/3100rpm and 1110hp at 4000ft/3100rpm (static). (Lumsden, British Piston aero-engines and their aircraft) The Wikipedia article is incorrect in regards to the 1050hp peak output as the claimed 1050hp at 3225rpm doesn't appear anywhere in Lumsden. This is a quote from Lumsden giving the (Bolded) A&AEE measured power curve:

TAURUS II, 1,060 bp, (1940) single-speed, . medium
supercharged. Geared, epicyclic 44411 LH. tractor-drive. (The
basic Taurus sleeve was used in the Napier-Halford Sabre), Power
Curve at rated altitude 5,000 ft from A.& A.E.E., Martlesham,
Report M.740, dated 26.10.39. Boost, rated +2.75 Lb/sq inch.

RPM 3225 3000 2800 2600 2400
BHP 1140 1048 958 848 760
BOOST +4.33 +3.51 +2.88b +2.03 +1.47lb

Max boost +4.25 th/sq inch. 1,140 bhp, 3.225 rpm take off to 1.000
ft or one minute. All-out level flight (five mirtutes), +4.25 1b, bby.
3225 rom. Fue! 87 Octane (DTD 230).

However the max 5 minute limit RPM according to the Albacore Pilot's Notes was 3100. It's possible that there was a WEP rating that was omitted from my copy of the PNs but that seems unlikely.
The 100 oct Taurus XII is more contemporary to the later Sakae -21 2spd variants and had 1090hp at TO and 1130hp at 3500ft (static)

The TAIC data (drawn from IJ documentation) for the Sakae -21 is 1115hp for TO and a peak Military rating was 1085hp at 9350ft. TAIC estimated WEP was 1180hp at 7500ft.

 

[elbmc1969]

I'd never thought that the Skua's nose configuration might be seen as an advantage for the cockpit view. I'm not sure I want to think that it was designed that way deliberately...

The view over short nose of the Skua Mk.I prototype must have been excellent for taxiing, landing, and searching for ships or other aircraft.


Incidentally, I suspect that the flat windscreen section on the Skua reflected worries about optical distortion. The SBD had a through windscreen sight, so there was no distortion. I believe that the D3A had an external telescopic sight and I hope that the optical designers would cancel any distortion from the canopy .

 

[elbmc1969]

IAnd (thinking out loud) this might suddenly make sense of the peculiarly large two-seater carrier-fighters the Fleet Air Arm is getting. The Fulmar is, perhaps, designed in anticipation of ASV, though in the end, of course, it inevitably ended up being flown by the Swordfish instead...

No. The reasons for two-seat fighter-reconaissance aircraft are well-established.

 

[Reluctant Poster]

The view over short nose of the Skua Mk.I prototype must have been excellent for taxiing, landing, and searching for ships or other aircraft.


Incidentally, I suspect that the flat windscreen section on the Skua reflected worries about optical distortion. The SBD had a through windscreen sight, so there was no distortion. I believe that the D3A had an external telescopic sight and I hope that the optical designers would cancel any distortion from the canopy .

The SBD telescope gunsight had problems with fogging and was replaced with a reflector sight.

 

[Shortround6]

I don't disagree with any of the above, but the Taurus, as stated, only had a single stage, single speed supercharger. It had nearly 20% less displacement and weighed less. I think it's important that we all understand this when we compare the two engines.

A problem was the smaller displacement. It means any increases in performance either take more work or your performance increase is going to be smaller (less actual power, not percentage). The R-1830 gave a bit more power several thousand feet higher up. 1050hp/2550rpm at 7500ft was fairly common for the 1940 and later R-1830s and the weight was about 150lbs more.
The R-1820s were fatter but weighed almost exactly (10-20lbs ?) the same as the Taurus.
The enemy and indeed even the local aircraft designers didn't care about a few percentage points of power to weight or a some of the other sleeve advantages, they cared about raw power and the Taurus didn't have it and was unlikely to get it.

P & W and Wright both made mistakes, P & W wasted some effort on the original R-2180 engine (14 cylinders of the same size as the R-2800) with about 30 built, contract for the 80 Republic P-44 Rockets were canceled. 4 engines went to Japan with the Douglas DC-4E airliner prototype and several US attack/medium bomber prototypes used them. P & W realized it was better to cancel it an use the production/engineering capacity for the R-2800.

Wright dove into the R-2160 rat hole. A 42 cylinder (yes 42 cylinder) 2160 cu in engine that was going to run at 4150rpm. How much this delayed the R-3350 is unknown but it must have been substantial. Over 6.5 million dollars dumped into the project. The early R-2800 program (A and B engines) cost about 8 million.

 

[elbmc1969]

The SBD telescope gunsight had problems with fogging and was replaced with a reflector sight.

Yeah, but that doesn't contradict the idea that the Brits were worried about optical distortion years earlier.

 

[Reluctant Poster]

Yeah, but that doesn't contradict the idea that the Brits were worried about optical distortion years earlier.

I just thought it would be an item of interest. Incidentally the USN used licensed British sights so the SDB ended up with the same sight as the Skua.
I would also note that optical distortion has nothing to do with being vertical. Look at the Spitfire.

 

[EwenS]

Though the cruisers did continue to be used on patrol until 1944 - with several of the Italian co-belligerents taking up the South Atlantic slack; I'd guess that Emerald - which still had an old-fashioned charthouse and topmast, not a tower bridge - simply didn't have much useful space for radar, her Kingfisher presumably being because she wasn't really designed for anything as hefty as a Walrus or an Otter (she seems to have used a Seafox with the rest of the smaller RN cruisers until they went out of style)...

No. Emerald, having spent the first part of 1942 in the Indian Ocean, returned to Portsmouth in Aug for a refit that lasted through until April 1943. During that refit she was fitted with:-
Type 281 air warning radar (aerials on both masts - the after one becoming a tripod to support the aerial)
Type 273 centimetric surface search (lantern on bridge)
Type 285 main gunnery radar
Type 282 x2 for the pom pom directors (she had 2 quad pom-poms fitted during this refit)
And Kingfisher replaced the Osprey

Following that refit she went back to the Indian Ocean until March 1944. At that point she returned home and her catapult & aircraft facilities were removed and her AA armament further strengthened before D-Day.

The old WW1 vintage cruisers operating in the Indian Ocean were amongst the last to be fitted with radar due to the low priority that theatre had for the equipment. By the end of 1942 most either had or were being taken in hand to fit radar of some kind as part of the regular refit process.

Emerald was refitted 1934-36 as part of which she received SIIL catapult and subsequently operated Hawker Osprey (1934-37), Fairey Seafox (1937-42) and finally the Kingfisher (1943-44). The catapult was not powerful enough to launch a Walrus, so hence the need for the Kingfisher in 1943.

Compare the IJN's active enthusiasm for replacing half the guns on battleships and heavy cruisers with a seaplane deck, which makes more sense when you realise they've become a search-radar platform, and the reduction in main armament is practical because the fire-control radar removes the need for large randomized salvos..

Different navies had different doctrines about the use of seaplanes / flying boats on capital ships and cruisers.

For the Japanese the seaplane carried on their 8" cruisers was the eyes of the fleet to find the enemy, not the carrier aircraft. Those cruisers would be operating with the fleet alongside the carriers. Take a look at the early carrier operations in WW2. It was Midway before Soryu carried a pair of D4Y-1C Suisei (Judy) aircraft for reconnaissance and 1944 before the C6N Saiun (Myrt) appeared, by which time it had no carriers to operate from.

As for Tone & Chikuma the plan for them was modified while they were building and they were redesignated "scouting cruisers" intended to carry 2 types:-
1. long range for scouting (2 or 4 3 seat aircraft) and
2. shorter range for spotting and AS work (4 2 seaters).
i.e. 6-8 aircraft instead of the usual 4 carried by the heavy cruisers.

To ensure that this increased aircraft complement wasn't damaged by the ship's own guns (more aircraft meant more space required midships to aft) the main armament was concentrated forward. They spent a large part of their wartime careers working with the Japanese carriers. Pearl Harbour & operations in the Indian Ocean in 1942 for example.

Japanese operations in 1942 revealed major weaknesses in their scouting capacity and procedures. Look at operations in the Indian Ocean and at Midway for the proof. One reaction was to see the need for another scouting cruiser. As Mogami had been so heavily damaged at Midway, losing one of her after turrets, she provided an excellent opportunity and platform to augment the scouting forces. As reconstructed she had a capacity of 11 aircraft but initially only carried 7.

As for the conversion of the battleships Ise & Hyuga, the Japanese intention was completely different and had nothing to do with scouting. Their conversion was a reaction to the loss of the carriers at Midway and an attempt to replace them i.e converted battleships as auxiliary carriers not as an increase to the scouting capacity. Various proposals were considered involving full conversion to flush deck carrier with island, removal of 4 turrets and rebuilding aft of the funnel or removal of just turrets 5 & 6. The latter route was chosen because:-
1. shorter time required for conversion
2. minimal effect on other warship construction
3. moderate material & labour cost.

As completed they were intended to operate as a pair as part of a larger carrier group with Junyo & Ryuho, each with 11 modified D4Y2 Suisei (Judy) dive bombers and 11 E13A Zuiun (Paul) floatplanes. Once launched the Judys would either land on a carrier in the group or fly to a land base. Cranes were provided to recover the floatplanes. Although completed in late 1943, their intended airgroup, the 634th Air Group, did not form until May 1944, so too late for the pair to participate in the Battle of the Philippine Sea. They only once seem to have embarked part of their air group for training. When they sailed in Oct 1944 as bait for Japanese operations in the Philippines they sailed without aircraft.

The full story of their conversion was set out in an article by Hans Lengerer, an expert in Japanese warships, in Warship 2009 published by Conway.

In the USN, aircraft like the SOC Seagull, OS2U Kingfisher and later SC-1 Seahawk had a mix of roles including recce (increasing the horizon of the cruiser force), gunfire spotting for the battleships and even AS work. For the USN pre-war doctrine called for the limited number of carriers to operate individually and separately from the battleships. But the main scouting force was contained in the 18 plane VS scout squadrons on the carriers themselves.

For the RN many of the cruisers would be operating alone, patrolling the sea lanes and a spotter plane increased those horizons in pre-radar days. As WW2 went on that patrol function was taken over by aircraft like the Sunderland, Catalina and Liberator. The best examples are the sea lanes of the Indian Ocean. But in a fleet scenario, with a carrier involved the main search activity was carried out by its aircraft, not the spotters on the battleships and cruisers. That way the recce effort could be directed more efficiently and was not so reliant on the sea conditions.

The RN's contrasting rejection of the floatplane is, therefore, the more curious decision; obviously they'd found masthead radar more useful than the Walrus in the Bismarck chase in North Atlantic conditions, and as you say they'd expended the effort on convoy shadowing so they generally had shore-based overflight, but carriers also seem to be more integrated with their capital ships (to the extent that Cunningham literally had Formidable in the battle line at Cape Matapan), so perhaps they don't perceive the need to give a battleship force a large screen of seaplane radar pickets sans carrier in quite the same way...

... because their carriers are providing the battle squadron radar pickets...

The first airborne radar available to the FAA was ASV.II which began to be fitted to Swordfish in the Home Fleet and Force H in March 1941. By the time of the Bismarck chase all 9 aircraft in 825 squadron on Victorious had been fitted but only a handful in the squadrons on Ark Royal. As for not using a Walrus during the Bismark chase I suggest you take a look at the sea conditions that existed throughout most of the time. They were awful. There would have been no means of recovering any floatplane even if they could be launched. The Germans did not operate their Ar 196 aircraft either.

As for Formidable at Cape Matapan, her aircraft lacked radar. For technical reasons that I've never seen explained, ASV.II wasn't made to work on the Albacore until the latter part of 1941. The Swordfish she had on board had been collected in Egypt in February as replacements due to a lack of Albacores in theatre. And Matapan was a night action. Formidable's aircraft had already succeeded in torpedoing Vittorio Veneto in the afternoon and the second strike launched in daylight and went in just after dark to torpedo Pola.

Even in 1942 ASV.II was not a universal fitting. During Somerville's search for the Japanese fleet in April 1942 none of Indomitable's and only some of Formidable's Albacores were radar equipped. A few years ago during some research into this period I discovered a corelation between the aircraft production dates and the complement on each ship. Then in late April there was a reshuffling of airframes between the carriers for unexplained reasons. I suspect however that it might have been about spreading the radar equipped aircraft more evenly through the fleet. Illustious when she arrived in April brought radar equipped Swordfish.

The RN did not so much reject the floatplane as found it no longer had a purpose. Naval warfare had changed. Cruisers patrolling the sea lanes virtually ended in early 1944 for reasons noted above. The submarine not the raider was then the threat even in the expanse of the IO and cruisers made better targets than sub killers. Cruisers were operating almost exclusively as part of a fleet with an increasing number of carriers available to protect them. Those carrier aircraft provided all the air recce and gunfre spotting required (as during Operation Inmate in June 1945 when cruisers of the RN, RCN & RNZN bombarded Truk Atoll with spotting from aircraft on Implacable). Postwar battleships and then cruisers just faded away.

And (thinking out loud) this might suddenly make sense of the peculiarly large two-seater carrier-fighters the Fleet Air Arm is getting. The Fulmar is, perhaps, designed in anticipation of ASV, though in the end, of course, it inevitably ended up being flown by the Swordfish instead...

As pointed out above it could not be further from the truth.

The only Fulmars to get radar were those converted as night fighters.

 

[Reluctant Poster]

hopefully.
They take off early, cruising at 90 knots
View attachment 717496
What bearing? Radar gives around 60 miles notice, best case

Would VT8 still be bait to occupy the fighters to let the Divebombers thru? as it was for SBDs, 18 were lost from Fighters and Flak, around 40%
Could Swordfish do as well?

At full load of ordnance, you have 550 miles of range, but slower cruise than TBDs and SBDs

I have posted this before.
According to Lundstrom in "The First Team" "The Devastators at cruised at 105 knots." This was on their way to attack the Japanese at Midway.
Basically the Swordfish and the Devastator were in the same ballpark when carrying a torpedo.

 

[Ovod]

Let's replace the TBDs used at Midway with Swordfish (or better yet Albacores).

I don't think the USN would be interested in adopting an aircraft the RN had already declared as obsolete as a torpedo bomber in the same year. however, let's roll with your suggestion anyway.

The smaller footprint of the Swordfish will allow for more aircraft per squadron; say 18. About 5 hours before dawn, TF16 and 17 fly off 12 ASV equipped Swordfish with LR fuel tanks and (hopefully) locate the KB.

The rest of the Swordfish are then flown off for a predawn torpedo strike using their ASV radar to locate the KB, and they all return except for one or two unlucky enough to get hit by random flak.

The problem with using the Swordfish as a scout aircraft within the vast Pacific ocean is its poor range – in this respect the Vindicator and Dauntless certainly had the advantage. Why would the USN use the Swordfish – or TBD – as a scout plane when there are far superior aircraft for the role already available?

Alternately, they are flown off for a dawn dive bombing strike armed with ~1500lbs of bombs.

Alternately, they are flown off for a day torpedo strike using a dive bombing mission profile (as per FAA doctrine).

Alternately, they are flown off for a day dive bombing mission.

Each of these mission plans was unavailable to USN TB squadrons because the TBD was incapable of performing them.

Not true at all. I don't think the British used the Swordfish as against surface warships very much (apart from the ASW role perhaps?), and I certainly don't recall it being used as a dive bomber against German/Italian warships – could you provide more details on the Swordfish's divebombing record? The Swordfish was a bit slow to be flying over groups of Japanese warships, surely? In any case, most combat aircraft can be used as a dive bomber, the Spitfire was used as a dive bomber, as was the P-40 and Ju-88. Not that you actually need to carry out bombing attacks on enemy shipping using dive bombing tactics.

Why not rephrase your opening suggestion like so: "Let's replace the Swordfish used at used in the Atlantic and Mediterranean with Swordfish…"? Would the TBD not have performed equally as well as the Swordfish during the Battle of Taranto or during the sinking of the Battleship Bismarck or against all other Axis surface shipping (when carrying the right torpedoes)?

 

[Ovod]

If memory serves correct, the RN torpedoes actually worked.

RN torpedoes worked better than US torpedoes in 1942, that's true, although US submarines sank up to 200 enemy ships in the same year, which compares very well with the RN sub fleet. It makes you wonder what the USN submarine fleet could have achieved if they actually had reliable torpedoes at their disposal?