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Kocur_
03-09-2008, 09:15 AM
In fall of 1934 program of modern Polish fighter was started. The plane was to be fast and armed with a powerful cannon, carry crew of two, and serve also as recon plane and dive bomber (single 300 kg bomb under fuselage, flaps as dive brakes). In plans for late 1930's the new plane was to replace both PZL P.11c fighters and PZL.23 Karas light bombers/recon planes, which would make the PZL.38 Wilk (Polish for wolf) not only the most numerous type in PAF but also something similar to what WW2 fighters like Spitfire, P-51 or Fw 190 became over time. All that forced twin engine layout and most unfortunately PAF leadership thought that developing an indigenous engine was possible. So the program of fighter actually started with program of the engine, known as PZL Foka. The idea was to have low drag of in-line and all pros of radial, so Foka was in-line, air cooled engine (popular idea in the era). Extremely low weight goal (around 200 kg) was to be reached by operating at extremely high rpm for the era (3800 rpm at full power, even Rapier engines of the mid 1930s had it lower) and using only 8 cylinders. Combination of extremely high rpm and too few, thus too heavy pistons, along with very limited experience of designers meant that the whole thing was *extremely* risky, if not doomed from the very beginning and eventually led to catastrophy of the whole thing (if only they did what thought of, i.e. bought French HS12X...). The engine was to develop 450 PS at 4000 meters. 900 PS for a figher sounded very well in 1934 and would be reasonable until say 1938. Limited power meant need for a very small airframe and such was bulit. Thus PZL.38 Wilk first flown in April 1938 powered by two Ranger V-770 engines (Foka engine was not yet airworthy, block cracking was not eliminated until summer 1939...) was a very small plane, actually smaller than Spitfire (11 m wing span, 8,35 m lenght, 20,4 m^2 surface) but overweighted (2160 empty, 2800 kg in flight with crew of two) in relation to power even though very efficient dural technology was used in the airframe. So even though one sees a twin engined plane, he should not think of say Bf 110 or Fokker G.I as things were about like that:
http://i194.photobucket.com/albums/z237/Kotsoor/th_Wilkainne.jpg (http://i194.photobucket.com/albums/z237/Kotsoor/Wilkainne.jpg)

Full testing was never done as at first Wilk had replacement engines, heavier, more draggy and less powerful than Foka, and when the latter was installed finally in second prototype, nobody cared much for the plane (as early as early 1937 Foka replacement - and improvement over - was searched and found in French GR14M small radials, which installed in Wilk with new wings and new nose with more guns produced PZL.48 Lampart, a prototype being built in summer 1939), so the actual performace is unknown. With Ranger engines the PZL.38 reached over 400 km/h at about 100 m, so projected top speed of 500 km/h (+/- 15 km/h) at altitude seems perfectly reasonable. The armament was two 7,92 mm mgs for observer and 20 mm cannon plus two 7,92 mgs fixed, in nose. The cannon was at first model A, fed from 100 rounds drum and low ROF of 320 rpm. It was not enough, so new PAF requrement issued in fall of 1937 called for belt feeding and 700 rpm (eventually model A standarised as wz.38FK was produced for the Army and used in TKS tanquettes). So in 1939 a better cannon was almost in production, known under factory designation of model D. It was belt fed (and magazine fed optionally) and had ROF of 600 rpm (model D already with 600 rpm but not yet with belt feeding was ready in June 1938). Both cannons were extremely powerful weapons in aerial 20 mm class, firing a round slightly more powerful than Swiss/German 'long Solthurn' (used in 2 cm Flak 30 and Flak 38), i.e. Polish 20 mm x 140B. Very flat trajectory projectiles (860 - 900 m/s) weighted from 134 (HE) to 155 grams (APIT).

All in all IF all that worked well and worked on time, in September 1939 PAF would have fighters very close in their abilities to MS.406: a little bit faster, almost identical in power loading, a little lower wingloading, similar armament, plus additional pair of eyes looking backwards and dive bombing capability.

I wouldn't write about that bitter flop if I hadn't come across THIS (http://www.youtube.com/watch?v=thFecaq-dfk) (the plane is in configuration known from 1938 Le Bourget exhibition, i.e. with Foka engines and model A cannon). Right after my jaw got back to its usual position I thought...
PZL.38 Wilk for SoW (what-if)! http://forums.ubi.com/images/smilies/winky.gif

Kocur_
03-09-2008, 09:15 AM
In fall of 1934 program of modern Polish fighter was started. The plane was to be fast and armed with a powerful cannon, carry crew of two, and serve also as recon plane and dive bomber (single 300 kg bomb under fuselage, flaps as dive brakes). In plans for late 1930's the new plane was to replace both PZL P.11c fighters and PZL.23 Karas light bombers/recon planes, which would make the PZL.38 Wilk (Polish for wolf) not only the most numerous type in PAF but also something similar to what WW2 fighters like Spitfire, P-51 or Fw 190 became over time. All that forced twin engine layout and most unfortunately PAF leadership thought that developing an indigenous engine was possible. So the program of fighter actually started with program of the engine, known as PZL Foka. The idea was to have low drag of in-line and all pros of radial, so Foka was in-line, air cooled engine (popular idea in the era). Extremely low weight goal (around 200 kg) was to be reached by operating at extremely high rpm for the era (3800 rpm at full power, even Rapier engines of the mid 1930s had it lower) and using only 8 cylinders. Combination of extremely high rpm and too few, thus too heavy pistons, along with very limited experience of designers meant that the whole thing was *extremely* risky, if not doomed from the very beginning and eventually led to catastrophy of the whole thing (if only they did what thought of, i.e. bought French HS12X...). The engine was to develop 450 PS at 4000 meters. 900 PS for a figher sounded very well in 1934 and would be reasonable until say 1938. Limited power meant need for a very small airframe and such was bulit. Thus PZL.38 Wilk first flown in April 1938 powered by two Ranger V-770 engines (Foka engine was not yet airworthy, block cracking was not eliminated until summer 1939...) was a very small plane, actually smaller than Spitfire (11 m wing span, 8,35 m lenght, 20,4 m^2 surface) but overweighted (2160 empty, 2800 kg in flight with crew of two) in relation to power even though very efficient dural technology was used in the airframe. So even though one sees a twin engined plane, he should not think of say Bf 110 or Fokker G.I as things were about like that:
http://i194.photobucket.com/albums/z237/Kotsoor/th_Wilkainne.jpg (http://i194.photobucket.com/albums/z237/Kotsoor/Wilkainne.jpg)

Full testing was never done as at first Wilk had replacement engines, heavier, more draggy and less powerful than Foka, and when the latter was installed finally in second prototype, nobody cared much for the plane (as early as early 1937 Foka replacement - and improvement over - was searched and found in French GR14M small radials, which installed in Wilk with new wings and new nose with more guns produced PZL.48 Lampart, a prototype being built in summer 1939), so the actual performace is unknown. With Ranger engines the PZL.38 reached over 400 km/h at about 100 m, so projected top speed of 500 km/h (+/- 15 km/h) at altitude seems perfectly reasonable. The armament was two 7,92 mm mgs for observer and 20 mm cannon plus two 7,92 mgs fixed, in nose. The cannon was at first model A, fed from 100 rounds drum and low ROF of 320 rpm. It was not enough, so new PAF requrement issued in fall of 1937 called for belt feeding and 700 rpm (eventually model A standarised as wz.38FK was produced for the Army and used in TKS tanquettes). So in 1939 a better cannon was almost in production, known under factory designation of model D. It was belt fed (and magazine fed optionally) and had ROF of 600 rpm (model D already with 600 rpm but not yet with belt feeding was ready in June 1938). Both cannons were extremely powerful weapons in aerial 20 mm class, firing a round slightly more powerful than Swiss/German 'long Solthurn' (used in 2 cm Flak 30 and Flak 38), i.e. Polish 20 mm x 140B. Very flat trajectory projectiles (860 - 900 m/s) weighted from 134 (HE) to 155 grams (APIT).

All in all IF all that worked well and worked on time, in September 1939 PAF would have fighters very close in their abilities to MS.406: a little bit faster, almost identical in power loading, a little lower wingloading, similar armament, plus additional pair of eyes looking backwards and dive bombing capability.

I wouldn't write about that bitter flop if I hadn't come across THIS (http://www.youtube.com/watch?v=thFecaq-dfk) (the plane is in configuration known from 1938 Le Bourget exhibition, i.e. with Foka engines and model A cannon). Right after my jaw got back to its usual position I thought...
PZL.38 Wilk for SoW (what-if)! http://forums.ubi.com/images/smilies/winky.gif

ElAurens
03-09-2008, 09:23 AM
Kind of along the lines of a Westland Whirlwind.

Too bad Poland could not bring some of their more modern designs to fruition.

They had some very clever designers working at the time.

Eustachy1980
04-16-2008, 04:39 PM
Don't listen Kocur. This Polish "modern" fighter had two important drawbacks:

- it could never be built in reality before September 1939 (it was only once flight-tested with target configuration which is oddly enough as for five years old project, additionally its prototypes proved to be much worse than initially expected - estimated max. speed was 465 km/h at 5000m altitude)

- anyway it would be shattered to pieces by German Bf-109 fighters in 1939 and later

Odin_Part_2
04-16-2008, 06:54 PM
You do realize of course that if you made that exact plane a Twin Boom Design & chopped off the Fuselage Body about a 1' - 2' Feet behind that rear window, you would essentially have the following airplane?

I affectionately call it The Fokker Lightning.

Watcha' want to bet mine could kill yours?

http://i38.photobucket.com/albums/e150/Odin1964/FokkerLightning.jpg

Skarphol
04-17-2008, 01:51 AM
Interresting read!
Threads like this is the only reason I still visit this forum!

Skarphol

DmdSeeker
04-17-2008, 03:48 PM
Tha twas a wonderfully well done film clip

HotelBushranger
04-17-2008, 10:06 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Odin_Part_2:
You do realize of course that if you made that exact plan a Twin Boom Design & chopped off the Fuselage Body about a 1' - 2' Feet behind that rear window, you would essentially have the following airplane?

I affectionately call it The Fokker Lightning.

Watcha' want to bet mine could kill yours?

http://i38.photobucket.com/albums/e150/Odin1964/FokkerLightning.jpg </div></BLOCKQUOTE>

+11111111 http://forums.ubi.com/images/smilies/agreepost.gif

Bestest twin boom plane ever!

Eustachy1980
04-19-2008, 12:05 PM
I forgot about the most important thing: this unfinished "modern fighter" effectively buried Polish fighter aviation before WW2 because no other "reserve" project was contemplated seriously. Therefore Polish aviation in September 1939 was plagued by two funny drawbacks:

1. No Polish fighter could catch-up any German bomber.

2. Poland was selling abroad more modern fighters than the Polish military had.