A WW2 fighter design for rugged areas

[HoHun]

Hi Pasoleati,

The Pe-2 had very large flaps and I don't recall Finns had much damage on them despite very sandy fields.

The Petlyakov Pe-2's wing layout was an analog to a mid-wing or maybe even shoulder-wing fighter, not a low-wing fighter. I'm not sure it had fowler flaps either - these move rearward and downward, and are closer to the ground than split flaps or chamber-changing flaps.

In which timeframe do you expect your fighter to be available?

Regards,

Henning (HoHun)

 

[tomo pauk]

Do we need to retract the tail-wheel on an airplane with a top speed of less than 400 knots?

400 kt = 460 mph; what actual speed figure is required again?
When?
With what engine?

Do we install a single, soft, large diameter tire on each main landing-gear leg?
… or do we install pairs of main-wheels in tandem (ala. C-130 Hercules)?
At what width do tires become too thick to retract into wings?

A normal undercarriage will do IMO.

A-26 Invader certainly double-slotted and I think the P-61 too.

Nakajima Saiun was also with the double-slotted flaps.

 

[isayyo2]

I'm surprised that the Hawk 75 by Curtis has yet to be mentioned...

The export models for China, Thailand, and Argentina featured fixed landing for "rough field operations and ease of maintenance." The Thai Hawk 75N attached below were fitted with podded 20mm Madsen cannons.

Hawk 75 Royal Thai Air Force cannon pods

Visible in this thread about the RTAF museum is a Hawk 75 with cannon pods: Royal Thai Air Force The Hawk 75 was offered with Madsen 20mm and Madsen 23mm in underwing pods. 1. Are these 20mm or 23mm? 2. Are the cannon pods in the museum original or reproductions? 3. How much did the cannon...

ww2aircraft.net

Curtiss Hawk 75N, Royal Thai Air Force (RTAF), Registrierung KH11, Seriennummer 12763, Copyright Karsten Palt, Foto ID 6412 - flugzeuginfo.net

flugzeuginfo.net das Flugzeuglexikon - the Aircraft Encyclopedia, Aircraft Photo Gallery, Flugzeugfotos

www.flugzeuginfo.net

 

[tomo pauk]

I'm surprised that the Hawk 75 by Curtis has yet to be mentioned...

The export models for China, Thailand, and Argentina featured fixed landing for "rough field operations and ease of maintenance." The Thai Hawk 75N attached below were fitted with podded 20mm Madsen cannons.

Kinda in collision course vs. the wishes of very, very high speed figures expected (320 mph at S/L; 400 kt)
Although the normal P-36 was a very maneuverable fighter, and appreciated for it's other qualities in combat, like docile and easy controls, and rate of roll.

 

[Scott Kenny]

Enough about guns and wing-flaps … let’s shift the conversation down to the landing gear.
My first guess is a conventional, tail-wheel landing gear.
Do we ask for a ribbed tail-wheel (ala. Lancaster) to improve steering on soft surfaces?
Do we need to retract the tail-wheel on an airplane with a top speed of less than 400 knots?

Yes, get a ribbed tailwheel.
No, I don't think we need to worry about retracting it.

Do we install a single, soft, large diameter tire on each main landing-gear leg?
… or do we install pairs of main-wheels in tandem (ala. C-130 Hercules)?
At what width do tires become too thick to retract into wings?

Yes, single brush tires, and if the tires are too thick bulge the wings like the F-4 Phantoms did.

But I strongly question getting 400 knots out of anything powered by a singlt R1820. It's going to take an R2600 or R2800 to pull that off!

 

[tomo pauk]

But I strongly question getting 400 knots out of anything powered by a singlt R1820. It's going to take an R2600 or R2800 to pull that off!

R-2800 + turbo + water/alcohol injection, and in 1945?

 

[blockhaj]

Shvak's ammunition was certainly weaker thna what the Western 20mm cannons were firing.
OTOH, Shvak was the only belt-fed 20mm cannon in mass service before mid-1941, RoF was very good, and was able to fire synchronized, unlike the Hispano.
Care to post definitive source that can confirm that Shvaks were unreliable?

Word of mouth and stories from the continuation war. ¯\_(ツ)_/¯

I dont have anything at hand but if u wanna dig on the subject i advice u look into the continuation war, as there are quite a few times the Finns found the Shvak too unreliable to use as aircraft armament. The same goes for the HS-404.

Belgian mechanical engineers working at FN Herstal were probably the cream of the crop in Belgium (similar with the best Czech and Swedish engineers, that worked at the gun-makers). Best American mechanical engineers probably worked in GE, P&W, Wright, Ford, Allison/GM - neither of whom were making automatic weapons, let alone the ones between 0.50 in and 57mm.

Passing of J.M.Browning left a void in the US design of heavy automatic weapons.

Indeed. US automatic weapons development was really behind the rest of the world at the end of the 30s throughout WWII. There is a reason they went ham with the 20 mm Oerlikon and 40/60 Bofors.

 

[blockhaj]

680 km/h with the Taurus - please, do tell.

Wishful thinking? XD

Im only quoting the designer Bo Lundberg, who managed to drive it 595 kph (4300 m alt.) with just 1000 hp from a Twin-Wasp (STW C-3). Doubtful if a Bristol Taurus II with 1400 hp would make it go 680 kph (looking in my notes actually 682 kph). Its possible he had some exhaust ejector in mind as such greatly effected the speed of the later FFVS J 22 depending on ejector type.

 

[sienar]

In theory. But they lacked the flaps I mentioned and apparently at least the Yak-3 (which achieved it's performance through small size) had bad stalling characterics in turn.

Regarding ŠVAK: According to Tony Williams's Autocannon there were problems with cartridge cases being broken in two when extracted (Williams says the gun has very fierce case extraction).

HoHun: Altitude range 0 - 6000 m. The history/variants of the R-1820 is surprisingly poorly covered in available sources. It doesn't help that the JAWA often uses civilian/factory designations in the tables.

Regarding Fowlers: Many Japanese aircraft used them while being taildraggers and the fields were definitely rough.

The big problem with fowlers is they drop the angle of stall much more than split or plain flaps. Because of that you really need tricycle gear to fully exploit them. If you put them on a taildragger, you have to choose one of two things;

- Accept wheels landings and all the issues that entails
- Limit the travel of the flaps

The latter is what the Japanese choose.

That's one of the reasons for discarding rifle-caliber MGs, yes. The bullets would just slide along the aluminum skin in most cases.

The head of armament at Messerschmitt suggested doing away with armor and simply making the aircrafts skin steel of ~5-12mm (going off of memory for thickness)

Some simple math+geometry shows that a thick steel skin like this would weight a bit more than the typical al skin steel armor arrangement.

Towards the end of the war the US did testing on aircraft armor and found normal Dural to be superior to steel at high angles of obliquity. This report goes on to suggest that making aircraft of thick Al skin without an interior armor may be the appropriate development path.

Simple napkin math shows that this approach is likely lighter than the normal one, with the added advantage of much better armor coverage and far fewer internal stringers/frames.

To improve things even further put a layer of 1-2mm of enamel over that thick Al skin...

 

[tomo pauk]

Wishful thinking? XD

Im only quoting the designer Bo Lundberg, who managed to drive it 595 kph (4300 m alt.) with just 1000 hp from a Twin-Wasp (STW C-3). Doubtful if a Bristol Taurus II with 1400 hp would make it go 680 kph (looking in my notes actually 682 kph). Its possible he had some exhaust ejector in mind as such greatly effected the speed of the later FFVS J 22 depending on ejector type.

Expecting from the Taurus to beat even 1200 HP mark was probably off the table, Bristol had a lot of problems making it run reliably even when making 1100-1180. And that is at low level; for 5 km we'd be happy with 1000 HP (= what the R-1830 already had on the J.22).
The Ki-44 was of similar size, even with 1500 HP on the -II it was still just beating 600 km/h mark.

The head of armament at Messerschmitt suggested doing away with armor and simply making the aircrafts skin steel of ~5-12mm (going off of memory for thickness)

Care to provide a source wrt. who was that guy, and when he suggested that, to whom?

 

[HoHun]

Hi Sienar,

- Accept wheels landings and all the issues that entails
- Limit the travel of the flaps

The latter is what the Japanese choose.

Quite interesting ... I was just looking at footage from the Nakajima Ki-44 taking off here ...

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Do you happen to have deflection values for the Japanese butterfly flaps?

Regards,

Henning (HoHun)

 

[Pasoleati]

Hi Pasoleati,



The Petlyakov Pe-2's wing layout was an analog to a mid-wing or maybe even shoulder-wing fighter, not a low-wing fighter. I'm not sure it had fowler flaps either - these move rearward and downward, and are closer to the ground than split flaps or chamber-changing flaps.

In which timeframe do you expect your fighter to be available?

Regards,

Henning (HoHun)

If you have seen a photo of the Pe-2 on ground with the flaps fully down, they hang very low.

 

[Pasoleati]

Yes, get a ribbed tailwheel.
No, I don't think we need to worry about retracting it.



Yes, single brush tires, and if the tires are too thick bulge the wings like the F-4 Phantoms did.

But I strongly question getting 400 knots out of anything powered by a singlt R1820. It's going to take an R2600 or R2800 to pull that off!

I never implied 400 kts in the original. I think 600 km/h at 6000 m would be OK.

 

[HoHun]

Hi Pasoleati,

If you have seen a photo of the Pe-2 on ground with the flaps fully down, they hang very low.

I have only found computer graphics. In these, the flap trailing edges come down to about the bottom of the fuselage, which is a lot higher than those of a low-wing aircraft where the trailing edges are at the bottom of the fuselage when the flaps aren't even extended.

Additionally, the Pe-2 is a larger aircraft than your typical WW2 fighter, and as the fuselage angle on the ground is pretty similar on all types, that means that the absolute height of the fuselage bottom over the ground is greater even if everything else where equal.

Anyway, when do you expect your fighter to be available?

Regards,

Henning (HoHun)

 

[Pasoleati]

When? Good question. Hopefully by January 1, 1944.

I'll check if I have a photo if the Pe-2 with flaps out. By the way, Lockheed Hudson, Electra et al: Fowlers and taildraggers.

 

[Arjen]

Image from Petlyakov Pe-2 'Peshka' by Peter C. Smith, Crowood Press 2003

 

[tomo pauk]

When? Good question. Hopefully by January 1, 1944.

Okay.

If 100+ oct fuel is no problem, 2-stage Merlin (63, 65), on something like the Fw 190 or P-51 (no worries, P-51s were used in SE Asia, so they will do in other rugged areas). That kind of engine will do well in a P-40, too, the P-40 being known as rugged. If hi-oct fuel is not available, DB 605A in the nose.
(rugged areas might have a problem with supply of vast quantities of fuel, so I'm not going to suggest something like the turboed R-2800; rugged countries mught have had a tough time to acquire that powerplant anyway)

Both of these aircraft might put the Fowler flaps in the good use, neither was much of a maneuverable fighter, but I have no problems in flaps staying as-is.

Guns - unless the 4-engined bombers are not expected, 2 20mm cannons + 2 HMGs will do. I'll avoid the weakest Oerlikon 20mm family by 1944, as well as the German and Italian HMG.

If the radial engine is wanted, probably go with the Ha 109, but with a bit greater valve overlap + fuel injection (= 1600+ HP on 91/92 oct), and the additional water-alcohol injection system (= another 200-250 HP), as well as with better layout of exhaust stacks. If someone can whip up a 2-stage S/C for the Ha 109, even better.
On a Fw 190 or P-51 would've result in a good weight save vs. the historical 190s or 51s.

 

[sienar]

Expecting from the Taurus to beat even 1200 HP mark was probably off the table, Bristol had a lot of problems making it run reliably even when making 1100-1180. And that is at low level; for 5 km we'd be happy with 1000 HP (= what the R-1830 already had on the J.22).
The Ki-44 was of similar size, even with 1500 HP on the -II it was still just beating 600 km/h mark.


Care to provide a source wrt. who was that guy, and when he suggested that, to whom?

I think it was a USSBS interrogation of the head of armaments at Obermagau. I can post the page in about a week.

Hi Sienar,



Quite interesting ... I was just looking at footage from the Nakajima Ki-44 taking off here ...

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Do you happen to have deflection values for the Japanese butterfly flaps?

Regards,

Henning (HoHun)

iirc, something like 30-35 degrees. Theory of Wing Sections and other books/NACA/ect show fowler max Cl increases linearly up till 50-60 degrees.

This might explain the issue a bit better; typical taildraggers have a ground angle of 10-12 degrees. If the plane stalls at 8 degrees flaps down then how can you land it safely?

Wheels landings are dangerous and likely a very bad idea for a high performance fighter landing on improvised strips and flown by conscript pilots. The other option is to limit the travel of the fowlers so the stall AoA is close to the ground angle.

There is a second less obvious issue as well. The point of landing flaps is usually to shorten the ground roll not just slowing the approach speed. With tricycle gear a fowler equiped plane can come in at near its max CL aoa, then all three gear contact the ground at nearly the same time and the pilot can then slam on the brakes and dump a bunch of energy quickly. This can't be done with a fowler taildragger. Stalling just above the ground in a three point landing does something similar for taildraggers, but then the plane must stall close to its ground angle.

 

[HoHun]

Hi Sienar,

This might explain the issue a bit better; typical taildraggers have a ground angle of 10-12 degrees. If the plane stalls at 8 degrees flaps down then how can you land it safely?

If the plane stalls at 8 degrees flaps down, the aircraft would be designed to give a corresponding ground angle to allow a safe landing. However, the full stall wouldn't really occur at the angle at which the flapped wing section stalls, as usually the outboard wing section with the ailerons doesn't have Fowler flaps. (The early He 177 had ailerons that doubled as high-lift flaps, but that was rather unusual and was changed to a more conventional setup on later versions.) You can probably even provide a non-uniform stall angle over the flapped section by shaping the flaps accordingly - now that I think it, that might be the reason for the tapering shape of the Japanese "butterfly" flaps.

In spite of this, there's still an issue for safe landings, and that's when the flaps don't extend, for example due to battle damage, as with a reduced ground angle, you can't stall the aircraft on landing without striking the ground tailwheel-first.

So with regard to the objective of creating a rugged aircraft operating from rough landing grounds, Fowler flaps do indeed have some drawbacks in addition to their mechanical complexity.

With tricycle gear a fowler equiped plane can come in at near its max CL aoa, then all three gear contact the ground at nearly the same time and the pilot can then slam on the brakes and dump a bunch of energy quickly. This can't be done with a fowler taildragger.

For some reason, my impression is that braking wasn't considered terribly important when operating from rough fields in WW2. I'm not sure at the moment what the reason was - I'd speculate that both the effect of braking on the individual wheels while bouncing over a rough surface was difficult (so as not to lock them inadventently when they're momentarily unloaded), and that skidding one wheel while braking the other might lead to a dangerous loss of directional control.

It's worth noting that Messerschmitt developed and tested a fast-acting variable speed propeller that also provided reverse thrust for braking on landing. Thinking about modern turboprop-powered STOL aircraft for operation from rough fields (like the Pilatus Porter), they also use this technique, so maybe wheel brakes aren't really the solution we're looking for. I don't know enough about this topic to state this with any kind of authority, though.

Regards,

Henning (HoHun)

 

[Pasoleati]

Propeller reverse would indeed be a big issue. There was an article on it in a 1945 Aircraft Engineering by a Swiss author working for Escher-Wyss. There were test figures of results achieved with reversible props and the impact was very great.

 

[red admiral]

For some reason, my impression is that braking wasn't considered terribly important when operating from rough fields in WW2. I'm not sure at the moment what the reason was - I'd speculate that both the effect of braking on the individual wheels while bouncing over a rough surface was difficult (so as not to lock them inadventently when they're momentarily unloaded), and that skidding one wheel while braking the other might lead to a dangerous loss of directional control.

The friction coefficient of the rough field is high so you stop pretty quickly anyway. And because it's a taildragger you can't apply too much brake force anyway without pitching the aircraft nose over.

Re reverse thrust propellers. The UK did this too but it was only postwar that they got adopted e.g. on the Beverley freighter which could taxi in reverse.

 

[riggerrob]

The friction coefficient of the rough field is high so you stop pretty quickly anyway. And because it's a taildragger you can't apply too much brake force anyway without pitching the aircraft nose over.

Re reverse thrust propellers. The UK did this too but it was only postwar that they got adopted e.g. on the Beverley freighter which could taxi in reverse.

I disagree about friction coefficients of rough fields … instead fc. vary widely depending upon whether you land on grass, sand, mud, snow, ice, etc.
Then fc. vary so widely that it becomes almost impossible to pre-judge cf.
This makes a reversible propeller more important.

 

[red admiral]

Friction coefficients have wide variation but a "rough field" will be significant ly.more than a paved or mown grass strip typical of the time. Only a smooth ice strip will be much lower friction.

 

[Pasoleati]

I have been thinking this project. First, I must revise the date of entry to January 1, 1943. This affects the engine choice. So, here are more detailed specs

Powerplant: Options are the Merlin, Hercules , R-2600, V-1710 and Mitsubishi Kasei. If a liquid-cooled engine is selected, radiator(s) must be arranged so that one punctured coolant radiator does not result in complete loss of cooling. Thus an arrangement with radiators of each wing leading edge are preferred. Water-injection may be used to meet performance requirements with either 87 octane fuel. Fuel system must be compatible with gasoline/alcohol blends.

Armament: 2 - 4 MG 151/20 cannon with 250 rpg. Must be able to carry 500 kg of bombs and release them in steep dive.

Protection: Self-sealing fuel tanks, protection for pilot and radiators.

Structure: Materials not limited, but must be suitable for cold winter conditions. Strength requirement with full internal load +9 g and -4.5 g with safety factor of 1.5. VNE 800 km/h IAS.

Maintenance and systems: Must have easy access to key equipment and structure. Systems must be suitable for operations down to -40 deg C.

Undercarriage: Must be suitable for grass, plowed/rolled snow and muddy conditions and be able to withstand frequent full-stall landings. No requirement for skis.

Handling: Handling must be such that average pilots with 150 hours total can handle it safely under normal Squadron operations. It must recover a 10-turn spin within 2 turns with standard anti-spin procedure. Normal stalls must have adequate warning and no tendency to spin. In accelerated stall there must be adequate war of approaching stall and the a/c must fall through (mush) when stalled; flicking out of turn not accepted.

Must be able to turn 360 degs within 18 seconds at 2000 m. Full aileron displacement must be possible by an average pilot at VNE. Minimum rate of roll at an optimum IAS at sea level 90 deg/s.

Performance: 520 km/h at sea level, 600 km/h at 6000 m (full internal load). Time to climb to 6000 m 6 minutes. Range 1000 km on internal fuel with warm up, take-off and climb to 6000 m at maximum allowed power, 15 minutes at WER, remaining at maximum air range conditions + 30 minute reserve at maximum endurance conditions.

Take-off distance to reach 15 m with full internal load no more than 350 m from grass. Landing distance from 15 m under the same conditions not more than 600 m. These must be achievable by an average pilot.

 

[HoHun]

Hi Pasoleati,

I have been thinking this project. First, I must revise the date of entry to January 1, 1943. This affects the engine choice. So, here are more detailed specs

I don't believe there was any fighter in January 1, 1943, that matched either your performance specifications, your strength specifications, or your ruggedness ideals, and certainly not one that matched all of them combined.

And carefree handling too ... I'd offer a re-engined Grumman F8F, but that one falls seriously short in the strength department.

Regards,

Henning (HoHun)

 

[tomo pauk]

Powerplant: Options are the Merlin, Hercules , R-2600, V-1710 and Mitsubishi Kasei.

Is this negotiable or not?

 

[Pasoleati]

Hi Pasoleati,



I don't believe there was any fighter in January 1, 1943, that matched either your performance specifications, your strength specifications, or your ruggedness ideals, and certainly not one that matched all of them combined.

And carefree handling too ... I'd offer a re-engined Grumman F8F, but that one falls seriously short in the strength department.

Regards,

Henning (HoHun)

Therefore the need for this project. Italian fighters had the strength. Unfortunately handling info is lacking, but it is known (Finnish flight test) that the Fiat G.50 partially met the accelerated stall as it mushed in turns to the right but flicked in left turns.

 

[Pasoleati]

Is this negotiable or not?

Negotiable as far as ruling out German, Italian and Soviet engines due to problems with reliability/durability.

 

[Pasoleati]

One additional requirement: oil cooler and coolant/cowl flaps must have automatic controls.

 

[HoHun]

Hi Jukka,

Italian fighters had the strength.

I'd be more ready to believe that this was an artifact of the Italian set of conventions used for strength considerations than that they built much stronger fighters than everyone else.

There's still no fighter on January 1, 1943 that meets your performance goals. The Me 109 will hit the speeds, but fail the turn rate. The Spitfire V will fail the speeds, the Spitfire IX will also fail the speeds since it reaches it top speed higher up. It will also fail the turn rate. The A6M will hit the turn rate, but fail the speeds. The F4F will fail everything. The Fw 190 will hit the speeds, but fail the turn rate, and like all the rest, the strength requirements.

Unfortunately handling info is lacking, but it is known (Finnish flight test) that the Fiat G.50 partially met the accelerated stall as it mushed in turns to the right but flicked in left turns.

If it doesn't flick, that only means your fighter doesn't have sufficient elevator control authority. You would need a low-aspect ratio wing to ensure it's truly flick-resistant, and that will kill your take-off and turn performance.

If you want to tame the flick, look at the Me 109 ... it was really hard to flick accidentally, thanks to the automatic leading-edge slats.

Regards,

Henning (HoHun)

 

[Pasoleati]

I don't get the need to list this and that aircraft failing to meet spec. The whole point here is not to list those but to design one that does.

And do you have any single piece of evidence to suggest that "Italian artefact" claim except "I feel so"?

 

[Scott Kenny]

We're really looking at two separate aircraft here. One for the early war, one for late war.

Bonus if we can modify the early war planes into the late war planes (FW190A versus D, for example).

Ordinarily, I'd suggest the F4F as the early war plane. Can't convert that into something that would meet the requirements of the late war plane, however.

And I don't get the need to list this and that aircraft failing to meet spec. The whole point here is not to list those but to design one that does.

Those specs are really high, though. I mean, a P-51D barely meets your Vne spec, so it'd take a very very sleek aircraft. Yet that very sleek aircraft works against the dive bombing requirement unless we add dive brakes, which generally add drag even when closed.

I'm thinking a turbocharged V1710 is out best bet to make the speed requirements.

 

[HoHun]

Hi Pasoleati,

Elevator authority is what enables you to increase the angle of attack. Angle of attack is what will make any wing stall. If the wings stall asymmetrically - and a turn is an asymmetric flight situation to begin with -, you flick.

The way you make this less likely to happen is to either design an aircraft that gives ample warning near the stall so that the pilot doesn't pull the elevator into the flick-stall range, or to limit elevator authority.

In the first case, you wouldn't say "the aircraft doesn't flick", because clearly, if the pilot would pull harder, it would flick just fine.

In the second care, you limit the angle of attack artificially to something below the maximum attainable, limiting performance. As this is not fly-by-wire with full sensors, it has to be a "good enough to work in all cases" limit, which means that you leave an ample margin of safety to guard against the worst case.

That's what you see in the Fiat G.50 case. It can't pull enough angle of attack to flick in one condition, but just enough to flick in the slightly worse condition resulting from turning in the opposite direction.

I don't get the need to list this and that aircraft failing to meet spec. The whole point here is not to list those but to design one that does.

That's called a trade study, a method recommended for example by Dan Raymer in his "Simplified Aircraft Design for Homebuilders". There are historical examples from the 1930s too, for example one conducted by Junkers for the A50.

If we'd manage to find an aircraft type that actually exceeds your specified performance, we could then "design" a type that trades off performance for all the extra requirements you have defined, since fulfilling these extra requirements will obviously only be possible at the expense of performance. The way to get a stronger aircraft of the same general layout as an existing type is to make all load-bearing members stronger, which if you're limited to the same materials as the existing type will result in a heavier aircraft, which kicks off the weight spiral. It's not by accident that the Mitsubishi A6M Zero ended up as a very light aircraft - they couldn't have built it like a Grummen F4F and expected the same kind of speed, range, and manoeuvrability on an engine of very modest power.

(You could try and break the mold by going to a radically different configuration than the historical WW2 fighters, ending up with something like a scaled-up Verhees Delta or a Waynfan Facetmobile. I don't think you're going to be able to meet your specifications with a conventional design, though.)

And do you have any single piece of evidence to suggest that "Italian artefact" claim except "I feel so"?

As it's you who has made a claim about the Italian aircraft, it's you who'd have to provide sources. Since this is your thread, I'll leave it to you if you'd actually like to try and convince me that you're right, and simply leave my doubts for the record.

Regards,

Henning (HoHun)

 

[Pasoleati]

We're really looking at two separate aircraft here. One for the early war, one for late war.

Bonus if we can modify the early war planes into the late war planes (FW190A versus D, for example).

Ordinarily, I'd suggest the F4F as the early war plane. Can't convert that into something that would meet the requirements of the late war plane, however.



Those specs are really high, though. I mean, a P-51D barely meets your Vne spec, so it'd take a very very sleek aircraft. Yet that very sleek aircraft works against the dive bombing requirement unless we add dive brakes, which generally add drag even when closed.

I'm thinking a turbocharged V1710 is out best bet to make the speed requirements.

Err, the P-39 meets the VNE spec (P-39 VNE is 523 mph) . Typhoon too. The level speed requirements are not stringent neither.

 

[Pasoleati]

According to your criteria, the F8F, P-38, P-61, Fiat C. R. 32, Fiat C. R. 42 had all "insufficient" elevator authority, as they all fell straight through on accelerated stall. Even more funny is that the pilot manuals of these aircraft have apparently not heard of your criteria as they shamelessly call such an accelerated stall an accelerated stall.

Aa for the Italian strength data, the source for the G.50 is an original Italian-language technical description brochure which I personally saw in a Finnish aviation museum. For the Macchi C.200 and C.202 the sources are the respective Aircraft in Profile booklets by Dr. Ing. Gianni Cattaneo who quotes Italian official figures ("Ministerio del something).

 

[Arjen]

Profile #28 gives an 'ultimate loading coefficient' of 15.8 for the M.C. 202, Profile #64 gives an 'ultimate loading coefficient' of 15.1 for the M.C. 200.
This still leaves the question under which conditions this 'loading coefficient' is determined.

Spitfire – The History by Morgan & Shacklady gives several numbers for 'load factor' in Specification No. F 7/30 to which the Spitfire was designed.

Structural Strength

(a) The strength of the main structure when carrying the load specified in paragraph 3, plus 100 lb shall not be less than as specified hereunder

Load factor throughout the structure with the centre of pressure in its most forward position 9.0.

Load factor for wing structure with the centre of pressure in its most backward position in horizontal flight 6.0

Load factor in terminal nose dive 1.75

Inverted Flight

(1) Load factor at incidence corresponding to the inverted stall and with C.P. at 1/3 of chord 4.5

(2) Load factor at incidence appropriate to steady horizontal inverted flight and at the maximum speed of horizontal normal flight 4.5

Assuming one of the specification's 'load factor' numbers is comparable to the 'ultimate load coefficient' numbers from the Ministerio dell' Aeronautica - which one?
In testing identical aircraft, would measurements methods of 'load factors' / 'ultimate load coefficients' by British and Italian establishments give identical results?

 

[HoHun]

Hi Pasoleati,

According to your criteria, the F8F, P-38, P-61, Fiat C. R. 32, Fiat C. R. 42 had all "insufficient" elevator authority, as they all fell straight through on accelerated stall.

With regard to the monoplanes, of course they could flick. They might not do so as easily as other types if the pilot recognized the incipient flick and reacted to it, which is something your "average 150 hours" pilot might not always manage to do on a P-38 for example, which according to your critera would make the type non-acceptable. A flick is just the first step to a spin, so if you can spin an aircraft, you can flick it too.

Biplanes have top and bottom wings that usually see different local angles of attack, which helps to make stalls more forgiving and easier to recognize and react to, but I suppose you don't seriously believe that your January 1, 1943 600 km/h fighter could be a biplane. Biplanes usually can be spun quite nicely, so they will flick as well.

If you're really going for absolute absence of flick stalls, you might have to look for a canard configuration. That's a configuration that wasn't particularly mature in WW2 though, and it came with other trade-offs which you're probably going to find unacceptable.

Aa for the Italian strength data, the source for the G.50 is an original Italian-language technical description brochure which I personally saw in a Finnish aviation museum. For the Macchi C.200 and C.202 the sources are the respective Aircraft in Profile booklets by Dr. Ing. Gianni Cattaneo who quotes Italian official figures ("Ministerio del something).

That doesn't alleviate my doubts, as individual figures don't mean that system of conventions under which they were determined was equivalent to that of the major nations (who all used different conventions, too).

Regards,

Henning (HoHun)

 

[HoHun]

Hi Arjen,

Spitfire – The History by Morgan & Shacklady gives several numbers for 'load factor' in Specification No. F 7/30 to which the Spitfire was designed.

Thanks for the reference point. The British 1.75 G at terminal speed obviously is much less demanding than Pasoleati's 9 G at 800 km/h IAS with a safety factor of 1.5.

One might be able to build a plane like a tank, but I doubt that when finished, it will still float like a butterfly to meet Pasoleati's take-off and turn rate requirements.

Regards,

Henning (HoHun)

 

[red admiral]

I don't think any of here are in a position to actually "design" such an aircraft. What we're really talking about is looking at historical near-neighbours and then theorising the impacts of changes to try and meet the requirements.

So given the 1943 date and the max speed requirement then I think we're largely forced to use a Merlin 60 series for max power, min mass/drag. Nothing historically powered by those radials was fast enough (?). V-1710 in P-63 was just about there, but dislike the unconventional configuration.

So from this then I'd take Spitfire VIII as the starting point with Merlin 60 series. A fair margin on the speed and time to climb requirements.

• We can design a lower drag airframe e.g. as per P-51. Given the requirement for battle damage redundancy I'd go for wing LE radiators instead of single ventral. Dual oil cookers as well. Reduced drag should increase max speed by 20-30kts and rate of climb a bit. At this point I'd also thicken up the wing a bit and move to inwards retracting main undercarriage. Slightly lighter structure, slightly reduced max Mach (in a very steep high altitude dive)
• Range is a bit under to meet the 30min endurance at range, although we have slightly lower drag from the above. Probably a few 10s gals extra needed. Call it 150gal ish. There's still plenty of internal volume for this; probably go for 20-30gal in rear fuselage. This extra mass reduces speed and time to climb a small amount.
• Turn rate needs to be slightly higher; the lower drag from the different wing radiators probably doesn't increase sustained turn rate enough. Maybe an airfoil/wing redesign with additional camber to trade off a little max speed for better sustained turn rate. Maybe need increased wing area - reduces max speed but there's loads of margin.
• Who knows on take-off and landing performance; it's complicated. There's probably enough performance margin elsewhere to add some big Fowler/Young man flaps for a mass/drag penalty if needed.
• Stronger airframe; difficult to tell which loads are driving mass. Maybe + a few hundred lbs to structure based on experience. This increased mass reduces performance in all the above areas. Turn rate is probably most sensitive.
• Otherwise, 4 x cannons in the outer wings. I don't think there's space in the forward fuselage and wing root. Single hard point on the Centreline, other hard points outboard of the main undercarriage
• Cut down rear fuselage with bubble canopy for improved visibility
• Speed brakes somewhere for dive bombing? Likely to be on wing upper surface inboard
• Handling qualities - not really a feasible way to assess these; I'd like automatic LE slats to maintain elevator effectiveness. A counter-rotating prop to minimise gyroscopic effects.

 

[GTX]

A fighter for rough conditions for low and medium altutudes
Specs:
-R-1820 H-series with water injection (1475 hp)
-wing area perhaps around 19-20 sq.m.
-Fowler flaps with a maneouver setting actuaed by a stick switch
-fuel load some 600 litres
-armament 2 x 20 mm cannon
-undercarriage suitable for fields

Almost sounds like an up-engined Curtiss Hawk 75N