From: jfb200@cbnewsd.cb.att.com (joseph.f.baugher)
Newsgroups: rec.aviation.military
Subject: Polish PZL P-7/11/24 series
Keywords: P-24, flew on both sides in WW2
Date: 23 Dec 92 22:05:09 GMT
Organization: AT&T Bell Laboratories -  Naperville, Illinois

The P.Z.L. P-7/P-11/P-24 series of Polish gull-wing single seat 
fighters of the 1930s were the product of the P.Z.L. (*Panstwowe 
Zaklaty Lotnicze* or State Aircraft Factory) located in Warsaw, 
Poland.  All of them had a high-mounted gull wing with two parallel 
struts, the airfoil being thinnest at the fuselage join and thickest 
at the "break".  This wing came to be known as the "Polish wing", and 
was largely the inspiration of the famous designer and pilot Ing.  
Zygmunt Pulawski, the chief designer of P.Z.L.  Pulawski was killed in 
a plane crash in March of 1931, six months before the first P-11 
prototype flew.  

The first aircraft using the "Polish wing" was the P-1 which first 
appeared in 1929.  It was powered by a 600 hp Hispano Suiza V 
liquid-cooled engine.  The undercarriage was fixed, and the wing was 
supported by a pair of parallel external struts.  The open cockpit was 
located immediately behind the shoulder-mounted gull wing.  The P-1 
created an instant sensation and won first place in the 1930 Bucharest 
competition against such contenders as the Bristol Bulldog and the 
Dewoiting D.27.  The P-1 immediately placed Poland in the first rank 
of aircraft-building nations, at a time when most other nations still 
adhered to the biplane as a first-line fighter.  However, the Polish 
War Ministry objected to the Hispano engine on economic and practical 
grounds, and as a result all P-series aircraft powered by 
liquid-cooled in-line engines remained experimental only.  

The first radial-engined variant was the P-6, powered by a 500 hp 
Bristol Jupiter VI FH enclosed in a Townend antidrag ring.  This 
version suffered from engine overheating problems, which led to the 
P-7 version powered by the 585 hp Bristol Jupiter VII F.  Some 150 
were built, and remained in service with the Polish Air Force until 
1939.  Some thirty were still in squadron service when the German 
attack took place.  

The best-known version was the P-11, which flew for the first time in 
September 1931.  The first P-11 prototype was powered by a Gnome-Rhone 
(Bristol) Jupiter engine, similar to the engine of the P-7.  The 
second and third prototypes were powered by a Bristol Mercury engine.  
The sixth prototype was the production prototype, and was fitted with 
an exhaust collector ring.  The second P-11 prototype was exhibited in 
1932 at the Salon International d'Aeronautique in Paris and caused an 
immediate sensation.  The third prototype was entered in the 1932 
International Contest at Zurich, a speed contest for single-seat 
fighters.  It came in second, the winner being a Hawker Fury.  One of 
the later P-11 prototypes took place in the US National Air Races in 
1932.  

The initial production version was the P-11a.  All were completed in 
1934 and all were powered by the Bristol Mercury IV S2 built under 
license by the Polish Skoda works.  Armament consisted of a pair of 
7.7-mm Browning machine guns with 700 rpg mounted in side fuselage 
bays and synchronized to fire through the propeller arc.  Although by 
1939 most of the Polish Air Force's P-11a fighters had been relegated 
to training duties, a few of them actually saw combat during the 
German invasion.  

The P-11b was a variant developed specifically for export.  50 
examples were ordered by Rumania, and these were powered by the 
Rumanian-built Gnome-Rhone K.9 Krse engine of 595 hp and were fitted 
with Rumanian instruments.  The geometry of the tail assembly of the 
P-11b differed slightly from that of the P-11a.  First deliveries took 
place in 1934.  A license for the manufacture of the P-11 in Rumania 
was acquired by the I.A.R. (Industria Aeronautica Romana) concern 
located at Brasov.  The Rumanian-built version was named P-11f.  In 
spite of substantial Polish assistance, the rate of production of the 
P-11f by I.A.R. was extremely slow because of lack of experience by 
the Rumanian company in building all-metal aircraft.  All P-11f 
aircraft were equipped with four guns and all were fitted with special 
low-pressure tires for use from unprepared airfields.  Four squadrons 
of the Rumanian Air Force were still equipped with P-11f fighters as 
late as 1941.  

The next production version was the P-11c, which began to reach Polish 
fighter units during 1935.  A total of 175 were built before the type 
was replaced on the production lines by the P-24.  The major design 
change involved the redesign of the forward fuselage in an attempt to 
improve forward view.  This was done by lowering the thrust line of 
the engine and raising and moving aft of the pilot's seat.  The 
dihedral of the inboard wing sections was increased and a new tail 
assembly was fitted.  The armament was increased to four 7.7-mm 
machine guns.  Two guns were in the wing, mounted just outboard of the 
"break", and two guns were mounted in side fuselage bays, synchronized 
to fire through the propeller arc.  Wing guns carried 300 rpg, 
fuselage guns 500 rpg.  However, only about one third of the P-11c 
fighters were actually fitted with four guns, delays in gun deliveries 
necessitating most machines being fitted with only two guns.  Only 
about one in three P-11c fighters were equipped with radios.  

The P-11c was powered by a 645 hp P.Z.L.-built Bristol Mercury VI S2 
nine-cylinder air-cooled radial engine driving a wooden two-blade 
fixed-pitch propeller.  Maximum speed was 186 mph at sea level and 242 
mph at 18,000 feet.  Range at economical cruising speed was 593 miles.  
An altitude of 16,400 feet could be reached in 6 minutes, and an 
altitude of 26,240 feet could be attained in 13 minutes.  Weights were 
2524 pounds empty and 3960 pounds loaded.  Wingspan was 35 feet 2 
inches, length was 24 feet 9 1/2 inches, height was 9 feet 4 inches, 
and wing area was 192.7 square feet.  

In the spring of 1939, it was decided to boost the performance of the 
P-11, the goal being the filling of the interim gap caused by delays in 
the development of the P-50 Jastrzab.  The improved version was designated 
P-11g.  It was to be powered by an 840 hp Mercury VIII engine driving 
a larger-diameter propeller.  The undercarriage legs were to be 
longer, and four 7.7-mm machine guns were to be fitted.  Production 
was initiated at the PWS works in Biala Podlaska in July of 1939, but 
the German invasion brought the program to a halt before any aircraft 
could be delivered.  

128 P-11s were in service in Poland at the time of the German 
invasion.  The P-11 was definitely a "pilot's airplane" which had been 
a world-class fighting machine in 1934.  However, by 1939 it was 
definitely obsolescent, having remained in service long after more 
modern types had become available.  The P-11 could not even reach the 
Dornier Do 17 bombers which were intruding into Polish airspace even 
before the beginning of the September 1, 1939 offensive.  When the war 
began, there were ten German aircraft for every Polish plane.  The 
Luftwaffe's Bf 109E had a 90 mph speed advantage over the P-11 and a 
1200-foot higher ceiling.  Although the P-11 possessed superlative 
maneuverability, all German aircraft with the exception of the Hs 126 
and the Ju 87 could avoid combat with the P-11 at will.  Nevertheless, 
the Polish pilots of the P-11 achieved a reasonable number of kills, 
which can be ascribed to the determined fighting spirit of Polish 
pilots in the face of insurmountable odds.  The first German aircraft 
shot down during World War 2 was a Ju 87, brought down by P-11 pilot 
Lt. W. Gnys.  The first Allied pilot to score two kills in one 
sortie was Lt. Gedymin.  In the first three days of the battle, 46 
P-11s and P-7s were lost, but a large proportion were able to be 
repaired and returned to duty.  In the same time period, 60 Luftwaffe 
aircraft were shot down.  On the third day of the offensive, P-11s 
made the first attack on a German armored column, with small results 
and heavy losses.  

In a matter of days, it was all over.  Contrary to general knowledge, 
the main losses suffered by the Polish fighter units were NOT caused 
by destruction on the ground.  Of 166 Polish fighters of all types, 
116 were destroyed in combat, and 50 or so were evacuated to Rumania.  
Twelve pilots were killed, 15 injured, and seven were missing in 
action, rather low casualties when it is considered what these people 
went through.  

The P-24 was the ultimate development of Pulawski's gull-wing design.  
It was stressed to take advantage of increased engine powers, it being 
anticipated that radial engines of up to 1000 horsepower could be 
accommodated.  The P-24 was a private venture on the part of P.Z.L, 
and was intended strictly for export and never served with the Polish 
Air Force.  In some respects, it can be considered as the export 
equivalent of the Polish Air Force's P-11c, as the two fighters were 
evolved in parallel and had many features in common.  

The first prototype was powered by a 770 hp supercharged Gnome-Rhone 
14 Kds fourteen-cylinder twin-row radial and flew for the first time 
in March 1933.  The second prototype was powered by an unsupercharged 
Gnome-Rhone 14Kfs radial of 930 hp driving a three-bladed metal 
propeller.  This aircraft was fitted with a pair of 20-mm Oerlikon FF 
cannon which were mounted in fairings at the junctions of the wings 
and the bracing struts.  This plane was used as a demonstrator machine 
for several Balkan air arms in the hopes of soliciting orders.  In 
1934, P.Z.L.'s test pilot B. Orlinski established a F.A.I.-recognized 
speed record of 257.3 mph.  The third prototype carried an additional 
pair of 7.7-mm machine guns in addition to the twin cannon and was 
intended to be representative of the proposed production model and was 
designated P-24A.  The P-24A featured a tail assembly similar to that 
of the P-11c and had an enclosed cockpit.  The P-24B featured an 
alternative four machine gun armament.  

The first foreign customer for the P-24 was Turkey, which ordered 40 
examples under the designation P-24C.  Fourteen of these carried an 
armament of two cannon and two machine guns, but the rest carried four 
machine guns.  Structurally, the P-24C differed little from the A or B 
variants, but the fairings at the junctions of the bracing struts and 
the fuselage were omitted.  

The Turkish government acquired a license for the manufacture of the 
P-24C, and the first example rolled off the production lines of 
Tayyare Fabricasi at Kayseri in May of 1937.  Limited production 
continued under Polish supervision until 1940.  

The Rumanian version of the P-24 was designated P-24E, and was quite 
similar to the Turkish P-24C but had an I.A.R.-built Gnome-Rhone 14 
Kmc/36 engine of 930 hp and had an armament of two 20-mm Oerlikon 
cannon and two 7.7 machine guns.  Six airframes were supplied by 
P.Z.L, but the rest were built under license by I.A.R.  at Brasov.  
First deliveries began in 1937, and some fifty were built by I.A.R.  
between 1938 and 1939.  The P-24E provided the backbone for Rumanian 
fighter squadrons and saw action on the Russian front when Rumania 
joined Germany in the war against the USSR.  Surviving P-24Es were 
later replaced by German Bf 109E-4 fighters.  

The Rumanian P-24E was to have an interesting postscript.  The I.A.R.  
factory used the P-24E as the basis of an entirely new indigenous 
design, designated I.A.R.80.  The rear fuselage, tail surfaces, the 
engine, engine mount and cowling, and various other components of the 
P-24E were married to a new forward and center fuselage section and 
fitted with an entirely new low-mounted wing and a retractable 
undercarriage.  The I.A.R.80 replaced the P-24E on the Brasov 
production lines in 1941.  

Bulgaria and Greece also ordered the P-24 in 1937-38.  Bulgaria 
acquired 34 examples of the P-24F with two 20-mm cannon and two 7.7-mm 
machine guns.  and Greece ordered 30 P-24Fs and six P-24Gs.  The P-24F 
was powered by a 970 hp Gnome-Rhone 14 N-7 fourteen-cylinder 
air-cooled radial which was housed in a new low-drag cowling.  Maximum 
speed was 214 mph at sea level and 267 mph at 13,940 feet.  Normal 
range was 497 miles at 186 mph.  It could climb to 16,400 feet in 5 
minutes 40 seconds, and could reach 26,250 feet in 12 minutes.  
Service ceiling was 34,450 feet.  Weights were 2924 pounds empty and 
4232 pounds empty.  Wingspan was 35 feet 2 inches, length was 24 feet 
7 1/2 inches, height was 8 feet 10 1/4 inches, and wing area was 192.7 
square feet.  

Two squadrons of the Royal Hellenic Air Force were equipped with the 
P-24F, and these operated against both the Regia Aeronautica and the 
Luftwaffe when Greece was invaded.  

Until the advent of the Hurricane, Spitfire, and Bf 109E, the P-24 was 
considered to be a world-class fighter.  It had a high degree of 
maneuverability and possessed a rugged, all-metal structure.  However, 
it was approaching obsolescence when World War II began.  

Since the P-24 flew both with the Rumanian Air Force and the Royal
Hellenic Air Force, it joins the list of aircraft which flew on both
sides during World War II.

Sources: 

  The P.Z.L.  P-11, Witold Liss, Aircraft in Profile # 75, Profile 
  Publications, 1966.  

  War Planes of the Second World War.  Fighters Volume 3, William Green, 
  Doubleday, 1964.  

Joe Baugher			**************************************
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