Rn vs IJN

[Glider]

I think the designers almost certainly could, the problem with the FAA seems to be at the spec level

Exactly. Give the designers their head and see what develops. Westland for instance had extensive experience in flaps and designing aircraft with low approach speeds, Fairy had extensive experience in Naval aircraft. Supermarine designed world class fighters but also flying boats, Hawkers robust aircraft with good performance and De Haviland and Miles could think outside the box. They could each play to their strengths, and if they wanted to pair up that would be their decision.
The trick is the spec level, just give them the minimum acceptable level, not want you want to get.

You would get six different aircraft but I bet all of them would have been a significant advance over the Albacore/Firefly.

I used a similar approach when I worked in IT. Each potential vendor had the same rough brief, they each had a meeting with the design/project team where they had the same presentation and the same opportunity to ask questions to the same people about the background and the objectives. They they all went away and prepared their own proposals.
It was a fair bit of additional work for us as we had to do the same preparation/presentation four or five times, but the results were worth it.

 

[RCAFson]

One source say that the M 21 would do about 1644nm (my calculation,,close enough) doing 200kts at 26.15 US gallons per hour. No altitude given.
Ranges without speed or fuel capacity are totally useless.
This is sort is a bit convoluted. The figures are in "Zero" by Robert C. Mikesh.
The figures are supposed to be from a captured Japanese document from Kwajalein Atoll. dated October 1943 Received by Joint Intelligence Center, Pacific Ocean Areas (JICPOA) Feb 19th 1944, and then published as JICPOA item #5891, using knots and metric system. The author of the book may have done the conversion from meters to ft.
So we have several steps in the chain and several sources of possible typos/conversion errors.
I am assuming the 'standard' fuel capacity if 215 US gallons for the M 21 Zero, However the 1644NM is just dividing the fuel capacity by the fuel per hour, not start, warm up, climb to altitude or reserve.
The published figures in the book also give fuel burns of 24.04 gal per hour at 190kts and 16.4 gph at 180 knts. for the truly phenomenal range, but it sure isn't at 251mph, again altitude not given so????
The book also gives the fuel burn at max hp of 91.14 GPH, and gives flying range with 30 minutes combat time, 20 minutes combat time and 10 minutes combat time.
These are
30 minutes..............774NM
20 minutes..............900NM
10 minutes..............1025NM

BUT they don't give the cruise speeds so we are tying to figure out what the difference in 30 minutes and 10 minutes is about 30.3 gallons of fuel equaling 251 NM of range comes close to 190kts cruise speed?????
Book says range and not radius. Error?
Does the flying ranges with combat time numbers include warm and take off climb and reserve?

Numbers are also given for the Model 22 and the model 32 (and this one has the range go to crap with the higher powered engine and reduced fuel)

Not saying these numbers are correct but they look better than some and do explain a few things.

From one of my previous posts in another thread:

Saburo Sakai:

From then on we flew literally day and night to stretch the range
of our planes. Apart from its range, the Zero was designed to remain
in the air on a single flight for a maximum of six or seven hours, We
stretched this figure to from ten to twelve hours, and did so on mass
formation flights. I personally established the record low consumption
of less than seventeen gallons* per hour; on the average our pilots
reduced their consumption from thirty-five gallons per hour to only
eighteen. The Zero carried a normal fuel load of some 182* gallons.

'To conserve fuel, we cruised at only 115 knots at 12,000-feet altitude.
Under normal full-power conditions, the Zero was capable of 275 knots
and, when over-boosted for short emergencies, could reach its
maximum speed of about 300 knots. On our long-range flights we
lowered propeller revolutions to only 1,700 to 1,850 rpm, and throttled
the air control valve to its leanest mixture. This furnished us the
absolute minimum of power and speed, and we hung on the fringe of
losing engine power at any time and stalling, (from: Samurai! page 38)

So Sakai and the IJN was able to establish a nominal, no allowance, no reserve, endurance of ~11 hours. If we assume that this was 115knots IAS we get 143knots TAS and a range of ~1573 NM. Subtracting 17IG for warmup, TO and climb, we get a range of 1430nm @ 143 knots at 12000ft for Sakai and about 1300nm for the average pilot.

However it could be 115knots TAS and this would give a range of ~1150nm for SaKai and ~1035nm for the average pilot.

*Imperial gallons, nominal full internal capacity and external (DT) = 186.5IG (Francillion)

 

[Wild_Bill_Kelso]

Exactly. Give the designers their head and see what develops. Westland for instance had extensive experience in flaps and designing aircraft with low approach speeds, Fairy had extensive experience in Naval aircraft. Supermarine designed world class fighters but also flying boats, Hawkers robust aircraft with good performance and De Haviland and Miles could think outside the box. They could each play to their strengths, and if they wanted to pair up that would be their decision.
The trick is the spec level, just give them the minimum acceptable level, not want you want to get.

You would get six different aircraft but I bet all of them would have been a significant advance over the Albacore/Firefly.

I used a similar approach when I worked in IT. Each potential vendor had the same rough brief, they each had a meeting with the design/project team where they had the same presentation and the same opportunity to ask questions to the same people about the background and the objectives. They they all went away and prepared their own proposals.
It was a fair bit of additional work for us as we had to do the same preparation/presentation four or five times, but the results were worth it.

I think a 20% smaller single seat Fulmar would be a good start early on....

 

[Wild_Bill_Kelso]

From one of my previous posts in another thread:

Saburo Sakai:




So Sakai and the IJN was able to establish a nominal, no allowance, no reserve, endurance of ~11 hours. If we assume that this was 115knots IAS we get 143knots TAS and a range of ~1573 NM. Subtracting 17IG for warmup, TO and climb, we get a range of 1430nm @ 143 knots at 12000ft for Sakai and about 1300nm for the average pilot.

However it could be 115knots TAS and this would give a range of ~1150nm for SaKai and ~1035nm for the average pilot.

*Imperial gallons, nominal full internal capacity and external (DT) = 186.5IG (Francillion)

The actual, real life operational range of aircraft like the A6M2, Seafire, Sea Hurricane, Swordfish etc., are known quantities. It's really not a mystery. Even if you try very, very hard to make it into one.

 

[Shortround6]

I think a 20% smaller single seat Fulmar would be a good start early on....

Start with the armament (variable), the pilot, radio gear, instruments are pretty much given.
Now start trading the speed and climb (engine power) with landing speed (wing size) and start figuring the fuel load.

Picking an external shape/size and trying to come up with the solution is going backwards.
Also beware the cube law.
scaling by length or span means you reduce the volume by the cube.
A 10% reduction in dimensions means a reduction of area of close to 20%.

A Fulmar I carried about 100% more ammo than Hurricane or Spit and it carried 155imp gallons of fuel (over 50% more)
it was good for a maximum still air range of approximately 950 miles (statute?) This was at 5000 ft using 1600 rpm and 2 lb/sq.in boost. The speed was 142 mph IAS, The maximum endurance about 6.18 hours.
If you cut the ammo and the rear seater you can make the plane smaller/lighter/ lower drag.
But you have to figure out the landing and take-off.
The take-off speed was around 63 mph IAS on a land strip.
"The stalling speeds with the flaps and undercarriage up and down were 72 mph IAS and 61 mph IAS respectively (4 mph higher with unsealed gun ports)"
slow speed turns could be done down to 76/66mph IAS.

So figure out what you really want and where you want to go. You can use a pantograph to make drawings fairly easy.

But you have to do all of calculations and you have build all new tooling.
Scaling doesn't really save that much.

 

[Glider]

I think a 20% smaller single seat Fulmar would be a good start early on....

You have basically outlined the spec.
Weapons - 8 x LMG with 500rpg, or 2 x 20mm with 120 rpg
Fuel - 150 gallons or 120 gallons plus two drop tanks
Take off landing speed 70mph max
Single seat

Its worth remembering that a Mosquito was converted into a single seat aircraft and the weight saving was quite significant, while doing nothing to the airframe. So a single seat Fulmar has a lot of potential.

Let the designers have their head and see what transpires

 

[Wild_Bill_Kelso]

Start with the armament (variable), the pilot, radio gear, instruments are pretty much given.
Now start trading the speed and climb (engine power) with landing speed (wing size) and start figuring the fuel load.

Picking an external shape/size and trying to come up with the solution is going backwards.
Also beware the cube law.
scaling by length or span means you reduce the volume by the cube.
A 10% reduction in dimensions means a reduction of area of close to 20%.

A Fulmar I carried about 100% more ammo than Hurricane or Spit and it carried 155imp gallons of fuel (over 50% more)
it was good for a maximum still air range of approximately 950 miles (statute?) This was at 5000 ft using 1600 rpm and 2 lb/sq.in boost. The speed was 142 mph IAS, The maximum endurance about 6.18 hours.
If you cut the ammo and the rear seater you can make the plane smaller/lighter/ lower drag.
But you have to figure out the landing and take-off.
The take-off speed was around 63 mph IAS on a land strip.
"The stalling speeds with the flaps and undercarriage up and down were 72 mph IAS and 61 mph IAS respectively (4 mph higher with unsealed gun ports)"
slow speed turns could be done down to 76/66mph IAS.

So figure out what you really want and where you want to go. You can use a pantograph to make drawings fairly easy.
View attachment 734661
But you have to do all of calculations and you have build all new tooling.
Scaling doesn't really save that much.

Ok but I don't think landing speed is necessarily going to be a problem with a 15-20% smaller wing. Wildcat had a 38' span with 260 sq ft wing area, A6M started with 39' / 241 sq ft, and went down to 36', and could still carry almost 200 gallons of fuel (counting the external tank). Hellcat was a bit bigger at 42', Corsair was 41'. All were good navy fighters as we know. The SBD Dauntless was 41' 6", carrying two people and a 1,000 lb bomb.

But it seems to me at 46' span, 342 sq ft wing area, the Fulmar was too big. It's enormous sitting behind me on my model shelf, almost as big as the Beaufighter. The problem with the whole bigger = more lift and more room for fuel and ammo thing is that bigger also equals more drag, which means more power is needed (and thus more fuel burned) to go the same speed. The sweet spot was a bit smaller. Especially in the early war when you probably only have about a 1,000 - 1,200 hp engine initially.

46' span also likely means pretty slow roll, which isn't good.

Give it a 40' span. That's about 87% of the actual wing size. In fact I think after they looked at it, that's what they did. The Firefly ended up being I think 41'. I bet you could get away with 38' for a single seat fighter and still get a good stall speed with flaps.

But I agree though, don't make the specs on that basis. Just tell the designers you need 330 mph, 800 mile range, 1 crew i.e. pilot. You don't need 750 rounds per gun either, they probably won't shoot that many without jamming anyway. Cut that in half. Carrier landings need to be calm and sweet. See what they come up with.

 

[EwenS]

The wingspan of the Firefly was originally 44ft 6in. It was only during the flight development of the prototype, and much modified (Griffon 72, leading edge radiators etc), Mk.IV in 1945/46 that it was reduced to 41ft 2in.

 

[EwenS]

It is all very well saying in 1938 "give the designers their head and see what they come up with" but whatever they do come up with has to be capable of being flown on and off the carriers you are already have or are designing and with the deck equipment (trolley catapult launch equipment, arrester gear etc) already in service or planned.

This is where carrier / carrier aircraft design gets interesting. The one directly affects the other. And for the RN until 1939 it only had full control one side of the equation, made worse by the deteriorating relationship with the RAF during the 1930s. Because the RN was not able to talk directly to the aircraft companies, that was the Air Ministry role, its knowledge base of what was possible in terms of aircraft design became increasingly outdated in a period of very rapid aircraft development. So the deck limitations it set out were too restrictive as the decade went on.

It is interesting that once it has full control in May 1939, it only took until Dec 1939/Jan 1940, with a few months war experience and changed circumstances, for the RN to start ditching some of the old concepts (turret fighters), relax some previous limitations (aircraft weight, take off distances, landing speeds) and request a single seat 400mph fighter (that was the target for the Firebrand).

Numerous things happened during WW2 to make flight deck operations easier. Longer effective flights decks (elimination of long round downs), uprated catapult and arrester gear, adoption of tail down launching from 1942 to accommodate operation of US types (the first British aircraft designed for tail down launch was the Seafire XV). Some of these are things that the USN also had to deal with as WW2 went on.

The Firebrand was a massive aircraft for a fighter. The Mk.I fighter version had a wingspan of 50ft (it was widened by 15.5in along the centreline in the following torpedo carrying versions to accommodate the torpedo). Length 38ft 2in. Max speed was 310 knots (357mph) at 18,000ft courtesy of the 2,305hp Sabre III engine. Sea level climb rate was 2,250ft/min. Take off distance into a 20 knot wind (important for carrier ops in a period when catapults were rarely used) 515ft. Gross weight 13,625lbs.

By comparison an F4U-1 Corsair II had a wingspan of 41ft and length 32ft 9.5in, weighed 11,878lbs with internal fuselage fuel. Speed 392mph at 24,000ft

 

[z42]

Speaking of knots and mph, did naval aircraft at the time already have speed gauges in knots, or was that a thing that was universally adopted post-war for both land and naval aircraft (as well as civilian ones)?

 

[Glider]

It is all very well saying in 1938 "give the designers their head and see what they come up with" but whatever they do come up with has to be capable of being flown on and off the carriers you are already have or are designing and with the deck equipment (trolley catapult launch equipment, arrester gear etc) already in service or planned.

That is what the briefings are for, to give them all the information they need, the opportunity to ask any questions and a contact point for further points

 

[Wild_Bill_Kelso]

It is all very well saying in 1938 "give the designers their head and see what they come up with" but whatever they do come up with has to be capable of being flown on and off the carriers you are already have or are designing and with the deck equipment (trolley catapult launch equipment, arrester gear etc) already in service or planned.

This is where carrier / carrier aircraft design gets interesting. The one directly affects the other. And for the RN until 1939 it only had full control one side of the equation, made worse by the deteriorating relationship with the RAF during the 1930s. Because the RN was not able to talk directly to the aircraft companies, that was the Air Ministry role, its knowledge base of what was possible in terms of aircraft design became increasingly outdated in a period of very rapid aircraft development. So the deck limitations it set out were too restrictive as the decade went on.

It is interesting that once it has full control in May 1939, it only took until Dec 1939/Jan 1940, with a few months war experience and changed circumstances, for the RN to start ditching some of the old concepts (turret fighters), relax some previous limitations (aircraft weight, take off distances, landing speeds) and request a single seat 400mph fighter (that was the target for the Firebrand).

Numerous things happened during WW2 to make flight deck operations easier. Longer effective flights decks (elimination of long round downs), uprated catapult and arrester gear, adoption of tail down launching from 1942 to accommodate operation of US types (the first British aircraft designed for tail down launch was the Seafire XV). Some of these are things that the USN also had to deal with as WW2 went on.

The Firebrand was a massive aircraft for a fighter. The Mk.I fighter version had a wingspan of 50ft (it was widened by 15.5in along the centreline in the following torpedo carrying versions to accommodate the torpedo). Length 38ft 2in. Max speed was 310 knots (357mph) at 18,000ft courtesy of the 2,305hp Sabre III engine. Sea level climb rate was 2,250ft/min. Take off distance into a 20 knot wind (important for carrier ops in a period when catapults were rarely used) 515ft. Gross weight 13,625lbs.

By comparison an F4U-1 Corsair II had a wingspan of 41ft and length 32ft 9.5in, weighed 11,878lbs with internal fuselage fuel. Speed 392mph at 24,000ft

This is a helpful reminder of how things got messed up with the aircraft procurement for the FAA. It's almost a less dramatic version of the rivalries between the IJA and IJN.

And the traits of the aircraft carriers themselves are also certainly worth keeping in mind. This is the sort of thing SR6 would often bring up. Could most 1939 era RN carriers launch and recover say, a Martlet?

 

[Wild_Bill_Kelso]

Wasn't there some kind of weird bureaucratic arrangement around the production of the torpedoes in the US as well? Was anybody ever courts martialed over that?

 

[MikeMeech]

Ok but I don't think landing speed is necessarily going to be a problem with a 15-20% smaller wing. Wildcat had a 38' span with 260 sq ft wing area, A6M started with 39' / 241 sq ft, and went down to 36', and could still carry almost 200 gallons of fuel (counting the external tank). Hellcat was a bit bigger at 42', Corsair was 41'. All were good navy fighters as we know. The SBD Dauntless was 41' 6", carrying two people and a 1,000 lb bomb.

But it seems to me at 46' span, 342 sq ft wing area, the Fulmar was too big. It's enormous sitting behind me on my model shelf, almost as big as the Beaufighter. The problem with the whole bigger = more lift and more room for fuel and ammo thing is that bigger also equals more drag, which means more power is needed (and thus more fuel burned) to go the same speed. The sweet spot was a bit smaller. Especially in the early war when you probably only have about a 1,000 - 1,200 hp engine initially.

46' span also likely means pretty slow roll, which isn't good.

Give it a 40' span. That's about 87% of the actual wing size. In fact I think after they looked at it, that's what they did. The Firefly ended up being I think 41'. I bet you could get away with 38' for a single seat fighter and still get a good stall speed with flaps.

But I agree though, don't make the specs on that basis. Just tell the designers you need 330 mph, 800 mile range, 1 crew i.e. pilot. You don't need 750 rounds per gun either, they probably won't shoot that many without jamming anyway. Cut that in half. Carrier landings need to be calm and sweet. See what they come up with.

Hi

We should also remember that the USN was ordering prototypes of large single-seaters, the Curtiss XF14C-2 with a span of 46 ft and wing area of 375 sq. ft., details from 'Warplanes of the Second World War Fighters Volume IV' by William Green:

This does show one line of thinking of the USN in June 1941 when they awarded the prototype development contract.

Mike

 

[SaparotRob]

Wasn't there some kind of weird bureaucratic arrangement around the production of the torpedoes in the US as well? Was anybody ever courts martialed over that?

View: https://youtu.be/eQ5Ru7Zu_1I?t=31

 

[RCAFson]

From one of my previous posts in another thread:

Saburo Sakai:




So Sakai and the IJN was able to establish a nominal, no allowance, no reserve, endurance of ~11 hours. If we assume that this was 115knots IAS we get 143knots TAS and a range of ~1573 NM. Subtracting 17IG for warmup, TO and climb, we get a range of 1430nm @ 143 knots at 12000ft for Sakai and about 1300nm for the average pilot.

However it could be 115knots TAS and this would give a range of ~1150nm for SaKai and ~1035nm for the average pilot.

*Imperial gallons, nominal full internal capacity and external (DT) = 186.5IG (Francillion)

On 7 Aug 1942 Sakai was in the air for about 8.5 hours and landed back in Rabaul with about 15IG less than ~5IG of fuel remaining. The outbound trip from Rabaul to Savo Island was achieved in about 3.5 hours after TO, for a nominal cruise speed of ~150-160kts. The return flight took about 4.5 hours. ( data from Lundstrom and Sakai) at minimum cruise speed but the course flown was not completely direct and Sakai was forced to switch to his reserve tank (32IG) east of the Green Islands (~120nm ~200nm from Rabaul) whilst flying at very low altitude. He then had to climb to clear terrain whilst proceeding to Rabaul.

Edit: My initial estimate of consumption from Green Islands to Rabaul was based upon the abridged account in Zero! by Caidan, however Sakai's Samurai!, gives a more detailed account and states he that switched to his reserve tank about 1 hour before sighting the Green Islands, and at that point Sakai estimated about 1.75 hours of flight time remaining at minimum cruise, and he landed at Rabaul was less than 5IG remaining.

 

[Wild_Bill_Kelso]

On 7 Aug 1942 Sakai was in the air for about 8.5 hours and landed back in Rabaul with about 15IG of fuel remaining. The outbound trip from Rabaul to Savo Island was achieved in about 3.5 hours after TO, for a nominal cruise speed of ~150-160kts. The return flight took about 4.5 hours. ( data from Lundstrom and Sakai) at minimum cruise speed but the course flown was not completely direct and Sakai was forced to switch to his reserve tank (32IG) east of the Green Islands (~120nm ~200nm from Rabaul) whilst flying at very low altitude. He then had to climb to clear terrain whilst proceeding to Rabaul.

Edit: My initial estimate of consumption from Green Islands to Rabaul was based upon the abridged account in Zero! by Caidan, however Sakai's Samurai, gives a more detailed account and states that switched to his reserve tank about 1 hour before sighting the Green Islands, and at that point Sakai estimated about 1.75 hours of flight time remaining at minimum cruise, and he landed at Rabaul was less than 5IG remaining.

These kinds of narratives are interesting and useful because they give us the details that act as a good reminder of what it really meant to fly a mission, especially a very long distance one, in terms of not only managing different fuel tanks (main, fuselage, external, reserve), but landmarks, weather, atmospheric conditions, prevailing winds, etc. etc. It's a lot more complicated than just estimating how far the engine will run at x number of RPM for x number of hours and minutes.

This is why when they calculated actual strike ranges they included wide margins for random problems - and 200 fewer miles for an A6M when flying from a carrier than a land base, because on the way home one had to find and line up with the carrier. And probably fly in circles for a while before it was your turn to land.

Of course, sometimes the planners did not take these things into account, or even the ideal range of the aircraft, such as when they sent Roald Dahl on that flight in his Gladiator...

 

[Shortround6]

Shifting back to ships.

The Japanese had 63 (?) Subs on active service on Dec 7th 1941.

There were about 5 boats at Kure assigned to training/local defense.

Combined fleet 14 boats
RO-33 & RO-34
1935-37, 700 tons, new torpedoes.

I-53 thru I-60 and I-62 and I-64 thru I-66
1927-32, 1575-1635 tons

3rd fleet had 4 boats assigned to blockade/transport
I-121 thru I-124
1927-28, 1142 tons, mine layers.


4th fleet had 9 boats assigned to the Japanese Mandate Islands RO-60 thru RO-68,
1923-27 boats of about 990 tons. old torpedoes.

5th Fleet had 26 boats.
I-1 thru I-6
1926-35, 1900-2080tons, two with float planes.

I-15 thru I-26
1940-41, 2184-2190 tons some with single floatplane.

I-68 thru I-75
1934-38, 1400-1420 tons

In Dec 1941 the Japanese had a further 29 boats under construction, to complete in 1942-43 and another 38 approved but not yet started.
The US had 111 boats in commission with 73 under construction but only 51 in the Pacific. 29 at Manila (6 S boats) and 22 at Pearl Harbor (6 S boats)
The Dutch had 12 boats of different ages.

The RN had 0.

 

[RCAFson]

The RN had 0.

The RN had 0 in the PTO!

 

[EwenS]

The RN had 0 in the PTO!

To go further, they had none east of Suez. The T boats Trusty & Truant were dispatched from the Med in the last few days of 1941/ first few days of 1942.