Why the Skua Only Carried a 500lb Bomb (1 Viewer)

[RCAFson]

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

At 0430 the KB was ~215nm from TF16/17, and USN intel gave Fletcher a very good idea of where to expect the KB. With ASV recon he can close earlier.

If the Swordfish (better still Albacores) recon locates the KB and then a night strike is sent in, the SBDs will know where to find the KB at dawn and all the SBDs can be sent in, in a single wave, with all the historical F4F escort with them. The KB would be obliterated in a single strike, regardless of the success or not, of the Swordfish strike.

If the ASV recon doesn't find the IJN then the more versatile strike options for the Swordfish would give them at least as good a chance, and probably better, of being as effective as the historical TBDs and probably equally successful as a distraction, although it's debatable whether that had much bearing on the success of the historical SBD strikes.

 

[ThomasP]

Swordfish at TOGW of ~9000 lbs (2x crew, 201 USgal normal + 72 USgal aux. fuel tank in navidator/observer position, 1x [1500 lb] torpedo and 4x 20 lb flares) with 60 minutes/42 USgal not available for range - had a range of about 750 miles at 105 mph best Vcruise for range.

Swordfish at TOGW of ~8250 lbs (3x crew, 201 USgal normal internal + 82 USgal external fuel tank on torpedo crutch, ASV Mk II radar and 8x 20 lb flares) with 60 minutes/42 USgal not available for range - had a range of about 820 miles at 105 mph best Vcruise for range.

edit: made a typo, the torpedo weight was 1500 lbs not 1600 lbs, corrected it.

 

[SaparotRob]

If memory serves correct, the RN torpedoes actually worked.

 

[ThomasP]

Addition to the above:

Before her refit in the US, HMS Illustrious (650' usable flight deck length) needed a 30 knot WOD to spot 12x Swordfish at 9250 lb TOGW and launch using rolling take-offs at an average of 45 sec between aircraft. The single catapult could launch Swordfish at upto 9100 lb TOGW at ~ 60 sec intervals. This allowed a total of 18x Swordfish to launch in a period of ~15 minutes.

Under good conditions the early ASV Mk II as installed on the Swordfish (ie Yagi aerials) and at a normal operating height of 2,000-5,000 ft could reliably(?) detect large ships at upto 36 miles, and coastlines at upto 65 miles. The average 'swath' along the flight path was considered to be 2x the detection range, so about 72 miles wide vs large ships. (from the ASV Mk II radar manual)

 

[planespotting]

Midway... I remember once reading online a very detailed after-action report that recorded cockpit observations of the sequence and relative position of the SBD attacks, written by a senior aviator who didn't get back to his carrier (I think most likely a preliminary report by Leslie of Bombing Three?), but I can't find a link now - anyone?

Longer fuselage will have the more favorable lenght/width ratio than a shorter fuselage that has the same width; we assume here a V12 powered ww2 fighter comparison, with crew one behind another. Cue the 20th century ships, where ~10:1 length/beam ratio was often used on fast ships (cruisers, battlecruisers), and 7-8:1 on not so fast ones ('normal' battleships). Also, cue the thickness to chord ratio on the fighters' wings, where 13-15% was a much better call than 17-19% wrt. drag of the wing (assuming same/similar profile series).

So a two-seat Spitfire should be perfect?

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.

And did a thick wing not have advantages in lift? The Wellesley and Lancaster seem to have thought so...

Hi
You appear to have missed that the Mercury was also used on the Gloster Gauntlet and Gladiator, Miles Martinet and all the British built Blenheims Mks. I, IV and V (Bisley) had Mercury engines, as did the Supermarine Sea Otter.

Mike

Not so much "missed" as left out because I was focusing on the period in 1937-1940 when the Perseus and Mercury were playing musical chairs...

And what you say deserves a reply, but now this has become a long, confusing and possibly boring ramble...

You are of course entirely right that there were earlier Mercury-engined types like the Gauntlet and the Polish PLZ P.11, but they were on the way out of production by about 1936, so didn't seem relevant to what I was trying to understand...

WIth the Blenheim, I took it for granted and left it in the background; I knew it dominated demand for the Mercury, but maybe that got too muted in my notes - wikipedia's numbers for the production Mk. Is and Mk. IVs imply that the type required around 10,000 Mercury engines between 1937 and 1941; and considering the huge scale of manufacture that this implies, did concern about capacity really prompt the switch to the Perseus for the production Skua and Lysander Mk II., which amounted to just 800-odd engines between them....?

The only plane I'd really missed out was the Gladiator, which was first delivered in 1937 and apparently continued in production until April 1940, with about 750 planes in total; I'm not sure whether production was evenly distributed across the span, but the number reinforces the point that there doesn't really seem to be a lack of Mercury engines. I assume the Dutch, who get several hundred more for the D.XXI and the G.1, were building them on their own line, but if they're imported from UK production, that would reinforce the point even more?

In the later period, from late 1940 (when the Perseus seems to be out of production except maybe for the Botha), there seems to be no problem switching the Lysander back to the Mercury and maintaining production for the Blenheim-derived Bisley and Bolingbroke, the Miles Master Mk. II and its Martinet variant, and the Sea Otter, a plane I admittedly had no idea about at all, but which doesn't fly until 1943...

So, the real question is why certain aircraft got the Perseus; setting aside one-offs, its first serial use seems to be on eighteen twin-engineed Vildebeest Mk.IV biplanes in 1936, followed by a whole lot of aircraft that have their first flight in the second half of 1938; it seems to be first-chocie for the eight four-engined Short S.30 flying-boats and fourteen two-Engined de Havilland Flamingo airliners, and of all things the prototype Sea Otter(!); but the Skua and Lysander Mk. II are told they can't have the Mercury, and the Botha is up-engined from the Aquila, and then refused permission to roll over to the Taurus...

Now, this invites wild speculation by the ignorant; was there a genuine enthusiasm for the Perseus which rapidly proved to be misplaced, or was there a lack of enthusiasm for the motor which required space to be made for it on airframes - active selection of the Perseus for production aircraft seems to be limited to the Vildebeest, S.30 and Flamingo, which struggle to reach a hundred engines between them, wheras its imposition on the Skua, Lysander and Botha accounts for around 95% of the respectable total of approximately 2000 units... though at one point, it seems there was a large, cancelled order for several hundred Perseus-engined Sea Otters?!

Sea Otters! Even by FAA standards, there's something impressively British about a catapult-launched gunnery-spotter/scout for battleships with added dive-bombing capability that had its first flight in 1938, and didn't enter squadron service until 1944, by which time the hangars it had been designed were being turned into cinemas...

Much more hypothetically, I wonder if they might have got a useful Perseus-engined aircraft if they'd kept the original narrow-body torpedo fuselage of the Botha, rather than insisting on a draggy hull and a level-bombing capability which they knew it was underpowered for; they might even have had the makings of a good night-fighter there...

 

[Shortround6]

focusing on the period in 1937-1940 when the Perseus and Mercury were playing musical chairs...

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

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.

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"
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.
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.

 

[marathag]

Swordfish at TOGW of ~9000 lbs (2x crew, 201 USgal normal + 72 USgal aux. fuel tank in navidator/observer position, 1x 1600 lb torpedo and 4x 20 lb flares) with 60 minutes/42 USgal not available for range - had a range of about 750 miles at 105 mph best Vcruise for range.

Swordfish at TOGW of ~8250 lbs (3x crew, 201 USgal normal internal + 82 USgal external fuel tank on torpedo crutch, ASV Mk II radar and 8x 20 lb flares) with 60 minutes/42 USgal not available for range - had a range of about 820 miles at 105 mph best Vcruise for range.

Where do these figures come from?

 

[EwenS]

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.

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.

 

[EwenS]

Sea Otters! Even by FAA standards, there's something impressively British about a catapult-launched gunnery-spotter/scout for battleships with added dive-bombing capability that had its first flight in 1938, and didn't enter squadron service until 1944, by which time the hangars it had been designed were being turned into cinemas...

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.

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.

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.

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.

 

[Juha3]

Swordfish at TOGW of ~9000 lbs (2x crew, 201 USgal normal + 72 USgal aux. fuel tank in navidator/observer position, 1x [1500 lb] torpedo and 4x 20 lb flares) with 60 minutes/42 USgal not available for range - had a range of about 750 miles at 105 mph best Vcruise for range.

Swordfish at TOGW of ~8250 lbs (3x crew, 201 USgal normal internal + 82 USgal external fuel tank on torpedo crutch, ASV Mk II radar and 8x 20 lb flares) with 60 minutes/42 USgal not available for range - had a range of about 820 miles at 105 mph best Vcruise for range.

edit: made a typo, the torpedo weight was 1500 lbs not 1600 lbs, corrected it.

In fact, it's so and so, NavWeaps gives the weight of the 18" (45 cm) Mark XII torpedo (the standard early war British aerial torpedo) as 1548 lbs.

 

[Shortround6]

This change took about 8 years or less. I would note that just about all other high powered (as opposed to trainer engines) engines showed a similar progression from 1932 to 1939/40 and the engines after 1940 also changed significantly to aid cooling if their power changed much. It was always a bit of race with one engine being ahead and then a competitor passing it out and taking the lead for while before an improved version the first engine came out. However, note that improvements came with a significant cost in tooling/manufacturing techniques.

 

[Simon Thomas]

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.
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).

The issue of roundness tolerance was solved in March 1938. ("The Bristol Sleeve Valve Aero Engines" Patrick Hassell Rolls-Royce Heritage Trust)

On the question of lack of power, bear in mind that the P&W and Wright engines have high TO powers, but their maximum continuous cruise powers are significantly less than TO power.
The Bristol engines have a lower TO power, but their max rich and max weak powers are a much higher % of their TO power cf P&W and Wright.

 

[Shortround6]

The issue of roundness tolerance was solved in March 1938. ("The Bristol Sleeve Valve Aero Engines" Patrick Hassell Rolls-Royce Heritage Trust)

Was it?
They were having a lot trouble with early Hercules engines with oil consumption, but maybe it was something Different?

On the question of lack of power, bear in mind that the P&W and Wright engines have high TO powers, but their maximum continuous cruise powers are significantly less than TO power.
The Bristol engines have a lower TO power, but their max rich and max weak powers are a much higher % of their TO power cf P&W and Wright.

I thought I took that into account with American engines were making 1000-1100hp (the American 1200hp was pretty much sea level for take-off).
The R-1820 and R-1830 could make about 1000-1050 hp at the rated altitude of the engines. Like the engine in the P-36 giving 1050hp at 6500-7500ft.
Nowhere near as impressive as the take-off power but let's be real. The two small 9s were were not going to equal the bigger American engines just due to displacement.
The Americans were 20% larger. They didn't have to cleverer.
The Taurus tried to be clever. Lost the advantage of light weight and had cooling problems which limited it to very low altitudes.

The Mercury was an amazing engine. It offered very good power for weight at 14,000ft, the trouble was trying to improve it ( sleeves took up most of the R & D) and the Perseus didn't give enough improvement for the time/money invested. Replacing an 840hp/14,000ft engine with an 880hp/15,500ft engine wasn't enough by the time it showed up. Especially without a 2 speed supercharger keep the T-O power up.

 

[Simon Thomas]

The accidental fix was good for less than a thou tolerance. Possibly one reason for the continued oil consumption issues was related to the ring sticking, which was fixed by the oil additive developed. There were must have been other hurdles they had to clear prior to ramping up production. I have not found any references which detail these difficulties. What we do know is that Bristol was missing expected delivery dates for the Hercules destined for the Stirling, and likely quite a few others.

My point was that the smaller Bristol motors are able to generate respectable max cruising powers, and due to their smaller size they weigh less than the US motors. The downside is the reduced TO and combat power.
Hawk 75A with GR-1820-G105A. TO power 1100 hp. Max cruising 625 hp. (Curtis manual 6895-A) 1287 lb 2.06 lb/hp (max cruise)
Pegasus XVIII. TO power 980 hp. Max power level flight periods exceeding 5 minutes 850 hp at 5000 ft. 1110 lb 1.31 lb/hp (max cruise)
Perseus XI, XII, XIV. TO power 830 hp. Max cruising & climb 745 hp at 6500 ft. 1025 lb. 1.38 lb/hp (max cruise)

The Taurus was a good concept on paper, but the vibrations were an insurmountable problem.

The Perseus 100 was a good 1200 hp 9-cyl radial, but it completely missed the bus. With Bristol having a chronic shortage of engineering staff, this one should never have been released from the department of good ideas.

 

[yulzari]

The Taurus has been criticised, and indeed, did not live up to the hoped for power, but it was principally used for long over ocean combat missions in the Beaufort and Albacore so cannot have been actually unreliable. It was still being used in RAF Albacores well past the end of the war.

The last, post war, Perseus at 1,200bhp was more a cut down Centaurus than Perseus. Bristol had planned to use a couple on the Bristol Freighter but wisely realised that they may as well save money and just sling on a couple of production line Hercules with more power.

 

[Shortround6]

Hawk 75A with GR-1820-G105A. TO power 1100 hp. Max cruising 625 hp. (Curtis manual 6895-A) 1287 lb 2.06 lb/hp (max cruise)
Pegasus XVIII. TO power 980 hp. Max power level flight periods exceeding 5 minutes 850 hp at 5000 ft. 1110 lb 1.31 lb/hp (max cruise)
Perseus XI, XII, XIV. TO power 830 hp. Max cruising & climb 745 hp at 6500 ft. 1025 lb. 1.38 lb/hp (max cruise)

I think there is a confusion in terminology on the Wright engine. 625hp would be about right for the max lean cruise. I don't know when in changed but the US engines didn't have a 5 minute max power rating in the 30s or maybe even 1940. 1941 may be different. They had a T-O rating that was at a higher RPM and could be a little as one minute. There were no "military" ratings. The Normal rating was often the max rich continuous rating, granted it sucked fuel like multiple holes in the fuel tank and was not practical. But all the other ratings when expressed as a percentage were based off this rating, as in a 60% rating was 60% of the normal rating and not the T-O rating.
I believe the max lean cruise for the Pegasus XVIII was 690hp 8000ft in low gear?

The Taurus was a good concept on paper, but the vibrations were an insurmountable problem.

The Perseus 100 was a good 1200 hp 9-cyl radial, but it completely missed the bus. With Bristol having a chronic shortage of engineering staff, this one should never have been released from the department of good ideas.

I am not sure the Perseus 100 even made it to the bus stop. I am not sure that a picture exists of it. It was announced in early 1946 (?) but after that???????It was gone from lists/publications in 1947.

The Taurus has been criticised, and indeed, did not live up to the hoped for power, but it was principally used for long over ocean combat missions in the Beaufort and Albacore so cannot have been actually unreliable.

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.

 

[elbmc1969]

Did the Fulmar get an "FR" designation for "fighter-reconaissance" the way that the Swordfish got the "TSR"?

Did the Skua ever get that sort of designation?

 

[Reluctant Poster]

?????????????????????????????????

I never said that the US system was in service when the Skua was designed.

Two statements, both true:

1. The British system was not user-friendly (based on accounts by FAA personnel)

2. The RN eventually adopted the US system

I didn't intend to direct my comment at you. I was pointing out the chronology which gets overlooked in any discussion about the Skua. The RNs complicated system was better than nothing at all which is what the USN had at the time.
I do wonder if the USN system was better than the later RN versions. HMS Victorious was converted to the USN system because it was to operate with USN aircraft and the Saratoga. As to the conversion of the other carriers later this could simply be a matter of commonality. It would be easier to convert 6 RN carriers than the dozens of US carriers.

 

[RCAFson]

Did the Fulmar get an "FR" designation for "fighter-reconaissance" the way that the Swordfish got the "TSR"?

Did the Skua ever get that sort of designation?

AFAIK the Skua was finally designated DBF:

The specification issued
On 12 December 1934, Specification O.27/34 was duly issued for a replacement FDB to replace the existing Hawker Osprey aircraft in the fleet. In the main, it followed the outline discussed already. The principal points were:

It was to be a single-engined ship-plane(17), either monoplane or biplane for the FAA to operate from carriers, and its role was defined as '(a) to disable the opposing FAA by dive bombing attacks on hostile carriers and other vessels, and to undertake such other dive bombing as may be required. (b) to engage hostile aircraft in the air'.
Dimensions to be a height of 14 feet 9 inches, a length of 33 feet, a wingspan of 46 feet, with wings folded this to be 16 feet only. The time given to fold the mainplanes to this dimension was 30 seconds.
Endurance, carrying a single 500lb bomb, to be 3 hours, extended to 5 hours fully economical speed....

...THE SKUA IS HATCHED
The Skua I as she finally emerged, was described as 'a two-seater dive-bomber fighter'(1) (note the reversal of priorities from the original designation), suitable for operation as a ship plane or landplane. (Smith, Skua!)

 

[elbmc1969]

And, again a question that shows that I know nothing, would planes decelerate that much in combat?

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.).