WI Panic Fighter 1938?

[trurle]

More that Muntz wasn't as rich as Fuller, or he wouldn't have been flying an 8 year old airframe or to get a top line P&W engine.
While Fuller wasn't Howard Hughes kind of rich, was still heir to the Fuller Paint Company fortune

I will believe in Lockheed Orion capable of handling 1000hp+ engine only on seeing a proper historical record of such. Without proof, Orion-class airframe capable to fly with 1000hp+ engine remains merely a fantasy.
As i calculate from compression ratio and engine power/weight, 1200hp Twin Wasp was transmitting 2.77 times more high-frequency vibration energy to airframe compared to 750hp Wasp. Likely well beyond Lockheed Orion structural integrity limits.

 

[riggerrob]

Dear trurle,
Most of what you said was accurate and I can only disagree with your last paragraph: “........ Fitting P-35 with flaps&slats to give it higher climb rate may result in suitable interceptor. At least until 1941.[/QUOTE]”
————————————————————————————
Flaps and slats are most effective during landing and take-off but decrease the sustained climb rate of interceptors.

Consider that the first few notches of flaps (15 or 20 degrees) improve lift and reduce stall speed ..... great for slow touch-downs and lifting off at low airspeeds ..... to reduce runway length requirements. Flaps and slats are best at increasing ANGLE OF CLIMB, but reduce RATE OF CLIMB.

Sustained rate of climb is more important for interceptors. However, as the airplane accelerates faster and faster than the stall speed, drooping flaps and slats create more drag than lift. As airspeeds approach cruise speed, rate of climb increases as flaps are retracted.
The other issue is that fragile flaps are not strong enough to remain attached at cruise speeds, so are retracted soon after take-off .... after out-climbing obstacles.

 

[trurle]

Dear trurle,
Most of what you said was accurate and I can only disagree with your last paragraph: “........ Fitting P-35 with flaps&slats to give it higher climb rate may result in suitable interceptor. At least until 1941.
————————————————————————————
Flaps and slats are most effective during landing and take-off but decrease the sustained climb rate of interceptors.

Consider that the first few notches of flaps (15 or 20 degrees) improve lift and reduce stall speed ..... great for slow touch-downs and lifting off at low airspeeds ..... to reduce runway length requirements. Flaps and slats are best at increasing ANGLE OF CLIMB, but reduce RATE OF CLIMB.

Sustained rate of climb is more important for interceptors. However, as the airplane accelerates faster and faster than the stall speed, drooping flaps and slats create more drag than lift. As airspeeds approach cruise speed, rate of climb increases as flaps are retracted.
The other issue is that fragile flaps are not strong enough to remain attached at cruise speeds, so are retracted soon after take-off .... after out-climbing obstacles.

Yes, for majority part of climb flaps to be retracted. Flaps are still useful for climbing in lower atmosphere (below 3km) though, because speed (especially for older propeller aircraft) is lower. Basically flaps are useful for climbing if airspeed of aircraft is below 370 km/h. Sorry for not stating clearly.

The question is basically about optimal lift/drag airfoil shape which changes with speed. 370 km/h is roughly the point where concave-convex profiles (flaps extended) become less advantageous compared to convex-convex profiles (flaps retracted).

P.S. I vaguely remember the optimal flaps retraction profile on climb was never followed by most pilots in WWII. Required too much attention not available for single-seater aircraft pilot.

 

[riggerrob]

Dear trurle,
That makes more sense.
Too much workload for solo pilots.
Modern flaps and slats are structurally limited to less than 200 mph.
The finer points of flap operating speeds (Vso) were not discussed when (2001) I studied for commercial pilot licence. Candidates were simply told to only use them below 1,000 feet above ground level.

 

[yulzari]

If the flaps can take the forces then the extra lift can be translated not only into the climb rate but also the extra lift will tighten turning as demonstrated with the Ki43 and Fairey Firefly. Beware with the ROC. TheL/D ratio at different speeds also plays a part.

 

[Dynasoar]

trule said:

400mph groundspeed was achieved because of the 150-200mph wind (yes, Wiley Post may be the first pilot intentionally utilizing the jetstream).
Vega/Explorer/Orion design line (designed as flimsy high-altitude transports, not as fighter/interceptors) was never fitted with anything above 600hp and never reached airspeed above 250mph, therefore these may be inspiration but not the base for the fighter aircraft design of 1938.

While you are correct in noting that Post was a jetstream pioneer (along with Tomlinson of TWA), your'e apparently unfamiliar with the difference between indicated and true airspeed resulting from differences in air density with altitude and local temperature. My E6B computer is not handy, but there are any number of internet substitutes for you to check my numbers. At an altitude of 51,000 feet and a temperature of -55F Wiley's air speed indicator would show about 100 miles per hour (a small margin above stall- minimum total drag). True air speed, corrected for density, that is speed over the ground for the highly supercharged Vega, would be 271 MPH! No wind- in still air nearly 300 mph. Not much jetstream to reach 400!

For those who can appreciate this, the Pratt & Whitney Wasp was modified to increase the speed of its internal supercharger from 7X engine RPM to 13:1, increasing critical altitude to above 20,000 feet. Bendix Corp supplied experimental supercharger(s) mounted above and behind the engine, driven from from the starter mount. This supercharger has been variously described as single and two stage, simple centrifugal or oblique flow- so there must have been several iterations. Intercoolers were located on both sides of the engine, leading down to a bottom located injection carb. Critical altitude (at which the engine can develop sea-level power) was increased to over 35,000 feet.

Now, about the "flimsy" part- Airplanes of that period were designed to operate from rough grass fields- the Vega series with higher takeoff and landing speeds. This pounding alone resulted in stressing the airframe for high 'g' loads. The Bureau of Air Commerce specified minimum air loads for commercial certification- I believe Lockheed designed for 6 positive g (can't pin down negative). Maybe the "flimsy" part came when the casein glue weakened years later- but this wouldn't affect the emergency interceptors.

Dynasoar

 

[trurle]

True air speed, corrected for density, that is speed over the ground for the highly supercharged Vega, would be 271 MPH! No wind- in still air nearly 300 mph. Not much jetstream to reach 400!

Let`s stop "promotion" style talks. Would you been talking to my former military customers, your proposal would be blacklisted already..on the ground of not meeting even minimal specs, even without touching reliability issues. Making interceptor what cannot catch Soviet SB bomber (or similar fast bombers) is pointless, regardless of price tag.

P.S. I would set the absolute minimal speed specs of interceptor (fully loaded and armed) at 285 mph (460 km/h) in 1938. With 300 mph preferable.

 

[trurle]

The Hungarian engineer Gyorgy Jenndrasik has been invited to build an aero-engine factory in your small, second-world country.

With Axis ties (implied by Hungarian engineer cooperating), why not to try to purchase production license for Oerlikon FF 20mm cannon? With its low muzzle energy it may be ideal drop-in replacement of 12.7mm M2 for light interceptors - 23kJ muzzle energy vs 18kJ for M2. Accuracy (especially on standoff range) will be bad, but accuracy is a less issue for the attack on heavy bombers.

 

[marathag]

With Axis ties (implied by Hungarian engineer cooperating), why not to try to purchase production license for Oerlikon FF 20mm cannon? With its low muzzle energy it may be ideal drop-in replacement of 12.7mm M2 for light interceptors - 23kJ muzzle energy vs 18kJ for M2. Accuracy (especially on standoff range) will be bad, but accuracy is a less issue for the attack on heavy bombers.

The Madsen 23mm or it's parent 20mm, would be a lot better choice.

low MV makes it very difficult to get a good number of hits, unless you get close.
And close is where your pilot gets hit, and thse interceptors won't have much armorplate or armorglass, so every burst has to be from a good distance away. A flat shooting 50 is better than a rainbow arc 20mm like the FF

 

[trurle]

The Madsen 23mm or it's parent 20mm, would be a lot better choice.

low MV makes it very difficult to get a good number of hits, unless you get close.
And close is where your pilot gets hit, and thse interceptors won't have much armorplate or armorglass, so every burst has to be from a good distance away. A flat shooting 50 is better than a rainbow arc 20mm like the FF

Well, history of the MG 151 upgrade to the 20mm caliber shows exactly opposite - low-velocity high-caliber upgrade may be preferable against fat, low-manoeuvrability bombers.

I am not a fan of the Oerlikon FF too, but Madsen 20mm may be simply too large to fit into limited space of engine cowling of cheap, mass-produced interceptor. And the recoil problem only makes mounting of Madsen 20mm more problematic. You should remember how long (4 years) Japanese has struggled with upgrading Ki-43 from 12.7mm MG to 20mm Ho-3 (which was both lighter and had lower muzzle energy compared to Madsen 20mm).

Ki-43 was designed initially for the 7.7mm MG armament, and upgrading its weapons mounts to 12.7mm caliber was a stretch already though. If your initial interceptor had from the very beginning of design the 12.7mm mounts (like P-35 or P-36) then all depends on the strength and space margins available on 12.7mm mounts. I would estimate chances of bulky and over-powered Madsen to be successfully integrated in P-35 or P-36 less than 5% though (P-35 and P-36/P-40 never flew with 20mm guns IOTL).

 

[Dynasoar]

trurle,

Here, repeated for you convenience is my message #89, which presented the proposed performance of my 1938 small nation interceptor. Construction,like several record setting aircraft of that time was of readily available monocoque plywood.

Couldn't let this topic go by without comment.

Engine, Two stage supercharged and heat-pipe intercooled Napier Lion W-1460. Since this engine first ran in 1917, and still set speed records as late as 1947 (John Cobb land speed record 394 MPH) it should be elegible. Limit boost to develop only the specified 1000 HP. Meredith effect engine cooling/exhaust pumped ramjet cooling diffuser.

Airframe, Molded plywood sandwich construction- tooling consists of cheap concrete forms, like earlier Lockheed Orion etc. Simple Lockheed style retractable (1932) landing gear. Low wing, wide tread gear for pilot conservation. Ideally suited for cheap,quick manufacture without use of critical material.

Armament, Two fuselage mounted synchronized 20 MM. Better yet, consult with vending machine manufacturers and quickly develop engine driven ammunition handling devices (cannons) which would be inherently synchronized and jam proof.

Performance, Even with a relatively large wing area but thin, flapped airfoil (possibly tapered tubular spar/fuel tank), I'd expect at least 330-340 MPH. Takeoff, over 50 ft obstacle, in no more than maybe 2300 ft. Pilot friendly is a powerful force multiplier.

Dynasoar

My last post, #126 which elicited your strange response, was clearly a summary of the demonstrated performance of an airplane using this construction which, while already obsolete in 1938, was a record breaker. The purpose of my post was, along with those of several other contributors, an attempt to correct your misconception that for some reason, monocoque ply structure. must be heavier than aluminum airframe construction at the time under discussion.

Please, at least read the post you are attempting to quibble with!

Dynasoar

 

[marathag]

Well, history of the MG 151 upgrade to the 20mm caliber shows exactly opposite - low-velocity high-caliber upgrade may be preferable against fat, low-manoeuvrability bombers.

I am not a fan of the Oerlikon FF too, but Madsen 20mm may be simply too large to fit into limited space of engine cowling of cheap, mass-produced interceptor. And the recoil problem only makes mounting of Madsen 20mm more problematic. You should remember how long (4 years) Japanese has struggled with upgrading Ki-43 from 12.7mm MG to 20mm Ho-3 (which was both lighter and had lower muzzle energy compared to Madsen 20mm).

Ki-43 was designed initially for the 7.7mm MG armament, and upgrading its weapons mounts to 12.7mm caliber was a stretch already though. If your initial interceptor had from the very beginning of design the 12.7mm mounts (like P-35 or P-36) then all depends on the strength and space margins available on 12.7mm mounts. I would estimate chances of bulky and over-powered Madsen to be successfully integrated in P-35 or P-36 less than 5% though (P-35 and P-36/P-40 never flew with 20mm guns IOTL).

Those cannons worked late in the war as those fighters(along with reflector gunsights) had a huge speed advantage over the bombers, something our 300mph light interceptor won't have against early SB-2 or Do-17Ms in 1938.

The Ki-43IIIb had the Ho-5, an upscaled Browning derived 20mm, it was 83 pounds. the Madsen was 120.
The advantage of the Madsen, while heavy, was that it was belt fed and ammunition was an early type of 'mine' shell, having twice the HE over the 20mm, and was available in the '30s

export Hawk 75 had 23mm as an underwing option

 

[trurle]

Those cannons worked late in the war as those fighters(along with reflector gunsights) had a huge speed advantage over the bombers, something our 300mph light interceptor won't have against early SB-2 or Do-17Ms in 1938.

The Ki-43IIIb had the Ho-5, an upscaled Browning derived 20mm, it was 83 pounds. the Madsen was 120.
The advantage of the Madsen, while heavy, was that it was belt fed and ammunition was an early type of 'mine' shell, having twice the HE over the 20mm, and was available in the '30s

export Hawk 75 had 23mm as an underwing option

Again, which cannon do you prefer - the fine gun left on ground or poor gun in your interceptor?

About your photo:
"XP-36F
Production P-36A fitted with two 23 mm (0.91 in) Madsen autocannons under the wings, reverted to P-36A because guns imposed an unacceptable performance penalty with top speed of only 265 mph (426 km/h)."

P.S. B-29 cruised at 440 km/h at altitude 9100m.

 

[marathag]

Again, which cannon do you prefer - the fine gun left on ground or poor gun in your interceptor?

About your photo:
"XP-36F
Production P-36A fitted with two 23 mm (0.91 in) Madsen autocannons under the wings, reverted to P-36A because guns imposed an unacceptable performance penalty with top speed of only 265 mph (426 km/h)."

P.S. B-29 cruised at 440 km/h at altitude 9100m.

But we don't need to worry about B-29s in 1938. That a problem for a later day.
That was fighters sold to Thailand, and were successful against the French in the short war they fought.

A Hawk 75N would be ideal against those ugly Farman and Amiot Bombers

 

[trurle]

But we don't need to worry about B-29s in 1938. That a problem for a later day.
That was fighters sold to Thailand, and were successful against the French in the short war they fought.

A Hawk 75N would be ideal against those ugly Farman and Amiot Bombers

Thai used Hawk 75N as light bombers/ground support and bomber escort rather than interceptor. Actually, the selection of heavy armament in detriment of speed&climb performance make logical sense for Thai, because they expected to fight against enemies with small or no aviation, therefore dual use fighter-(ground attack) aircraft was preferable to interceptor. They did not even ordered retractable undercarriage option - because speed needed to be just matched with their fleet of O2U, Ki-21 and Ki-30 bombers.
The OP for Ruralia (fictional country) has different constrains - for Ruralian airforce the best may be nearly mythical Curtiss Hawk 75 Q with retractable undercarriage (2nd Chinese P-36 demonstrator) - it fits to 1000 HP engine (at the OP limit), and was fitted with unspecified cannon pods in wings. It was considered the flagthip of their fighter fleet.

I do not know which cannons Chinese used. Chinese had 20mm Madsens, but may be they even installed their Solothurn T-6-200 8mm machine guns in pods (no known records and photos)

Also, i also find the following text in Japanese, here the translation:
"Two Type 96 fighters (A5M) were fitted with Oerlikon FF cannons at wing, but the problems with both the gun itself and yawing at takeoff lead to the experiment termination"

Overall, mounting powerful guns in wings of light aircraft is solution asking for problems. Random dispersion increases, aim point shifts, roll-induced and acceleration-induced dispersion and finally yaw instability happens, which is aggravated in tail-wheel configuration - because tail-wheelers already taking off with significant sideslip. For WWII and afterward, basic rule was "accurate air-to-air cannon is fuselage-mounted cannon".

Therefore, may be better not to seriously consider 20mm cannons as interceptor weapon in 1938. Even very successful P-47 fought until end of WWII with 12.7mm machine guns. If some 20mm cannons will fit in cowling, fine. If not, just drop the idea.

More practical pathway of "panic fighter" upgrades may be to gradually add 12.7guns as more sturdy enemy bombers appear, and use unguided rockets at the very end of war. Rockets would be as bad for performance as 20mm guns, but at least rockets can be jettisoned.

 

[Paul_Sussex]

How about a licence built Ki-27 with an 825hp Bristol Mercury and two FN 13.2mm guns?

 

[marathag]

How about a licence built Ki-27 with an 825hp Bristol Mercury and two FN 13.2mm guns?

I believe neither the IJA or IJN allowed licensed production outside of Japanese held areas, would sell only completed units.

FIAT and Curtiss, though, were happy to sell up to near turnkey factories. Curtiss got pretty good at work arounds for the US ban on sales as the '30s went on

 

[trurle]

I believe neither the IJA or IJN allowed licensed production outside of Japanese held areas, would sell only completed units.

Yes. i must confirm. Last Japanese international sale of military aircraft type happened in 1932 by Aichi.

 

[tomo pauk]

I think I'm going with the Bf 109 airframe (in series production before the set year of 1938, contrary to the P-36 or Spitfire; Hurricane is too big & draggy for anything under a Merlin), HS 12Y engine with 'beard' radiator, an Oerlikon FFL (in-between the light FF and big & heavy FFS) with a 90 rd drum, plus a pair of any two LMGs that use same cartridge that I have in production (7.92, .303, 7.62x54, .30-06...).
As low drag as possible on the current level of aerodynamics, small, light, has plenty of punch, simple and suitable for series production.

 

[sdgottsch]

Since your country does not have a huge armaments industry, you are forced to buy critical components (engines, radios and armament) overseas. Awkward politics further limit arms purchases to second-string or “last week’s fashion.”

I agree with Tomo that the Bf 109 would be a great base-line platform but the restriction by the OP to limit arms purchases would mean the Bf 109 is ruled out. Maybe could use the He 112v4 as a baseline since it was flown in 1935 and could just get the plans (to build more) from Germany since they didn't want it anyway? Plus it had 2 fuselage mg and a 20mm FF in each wing to meet the intended spec.