PZL P.24

Monoplane fighter designed in the early 1930's by Zygmunt Pulawski, chief designer of Poland's Panstwowe Zaklady Lotnicze (State Aviation Factory).

Unknown to most people today, Poland's aviation industry in the 1920's and 1930's was on the bleeding edge of technology and aircraft design. Together with France, Great Britain and The Netherlands they took the aircraft industry from the Great War-era string and canvas aeroplanes, to all-metal, high-powered, fast and reliable machines of war. Everybody knows the glamorous Spitfires, Messerschmitts and Mustangs of World War II. You've seen it in countless movies and contemporary newsreels, usually shot through gun cameras or in neatly posed publicity shots. The Fokkers and the Sopwith Camels of The Red Baron and Lanoe Hawker are equally etched in our collective memory of wars none of us has seen.

But what came inbetween the 1917 Fokker Triplane and the 1935 Messerschmitt Bf 109? Surely, the Supermarine Spitfire wasn't designed on basis of a Sopwith Camel? What made Sydney Camm design his Hawker Hurricane the way he did? How did aircraft designers around the world come to the conclusion that a monoplane performed better than a biplane?

The answers to this are manifold, but one major source of inspiration for all european aircraft designers in the interwar period was the Polish pilot and engineer Zygmunt Pulawski and his line of P.Z.L. fighter planes.

Background
The P.24 was the ultimate in a series of single-seat fighters, all with a shoulder mounted gull wing that became known as "the Polish wing" throughout the aviation industry that slowly transitioned from biplanes to monoplanes.

The P.1 prototype
P.Z.L.'s first gull winged fighter was the P.1 prototype. From its first flight on September 25, 1929 it was regarded a sensational aircraft with its liquid-cooled Hispano-Suiza 600 horsepower engine, sleek lines and oustanding performance. At sea level, the P.1 could do 300 km/h, and its climbing abilities and handling were unmatched. At the International Fighter Competition in Bucharest in June 1930, the P.1 outclassed among others the Dutch Fokker D.XV, the British Bristol Bulldog and the French Dewoitine D.27, placing Poland firmly at the top of the class of aircraft-building nations. Because the Polish military authorities insisted on using air-cooled radial engines instead of the Hispano-Suiza V-engine, the P.1 never went into production.

The P.6 and P.7 prototypes
To meet the demand for radial engines, P.Z.L. built two new prototypes dubbed P.6 and P.7. The P.6 soon vanished because of engine overheating problems, while the P.7 with its rotary Bristol Jupiter VIIF engine had its maiden flight in October 1930, entering service with the Polish military in 1932. In 1933, Poland became the first country in the world with a front-line fighter force consisting entirely of all-metal aircraft. About 150 P.7's were built, and they remained in Polish service until 1939.

A little trivia: the P.6 prototype was sent to the United States in 1931 to take part in the Cleveland, Ohio National Air Races. Piloted by Boleslaw Orlinski, the P.6 won the fighter contest by a large margin.

The P.11
In March 1931, Zygmunt Pulawski died in a plane crash, leaving P.Z.L. with Wsiewolod Jakimiuk to develop the successor to the P.7; the P.11. The P.11 first flew in September 1931, powered by a 500 hp rotary Bristol Mercury IVS2 engine and with better armament than the P.7. The P.11 went into production, equipping 12 fighter squadrons with a total of 225 planes. The Polish Air Force lost 116 fighters to the German invasion force, shooting down about 120 enemy planes in the progress. Even though the P.11 was a nimble fighter and could outmaneuvre the Messerschmitt in certain flight regimes, the German planes had more power and a higher operational ceiling, meaning they got to pick the fights. Despite this, only 20 P.11 fighters were destroyed in air-to-air combat, the rest being destroyed on the ground.

The P.24
The P.24 was a private venture by P.Z.L. looking to secure export orders for aircraft. It was largely similar to the P.11 save for the fact that the P.24 could accomodate engines up to 1000 hp. Other than that, the new designation was little more than a marketing ploy by P.Z.L. The first P.24 prototype flew in March 1933, powered by a supercharged 760 hp Gnome-Rhône 14 Kds "Mistral Major" fourteen cylinder radial engine. The Gnome-Rhône engine was selected over the Bristol engine because of licensing restrictions imposed by the British engine makers.

The second prototype - also known as the Super P.24 - was fitted with dual 20 mm Oerlikon cannons and powered by a 930 hp Gnome-Rhône radial engine. Several Balkan air arms received demonstration flights by the second P.24 prototype during late 1933 and early 1934, but sales orders failed to materialize at the P.Z.L. headquarters in Warsaw.

In March 1934, the Super P.24 prototype set an international speed record, attaining 257.24 mph at a height of 100 feet.

Yet another prototype was built, this time with an additional pair of 7.7 mm cal machine guns and the designation P.24a or Super P.24bis. At the Salon de I'Aeronautique (Paris Air Salon) in 1934 it was marketed as the most heavily.armed fighter in the world, sparking considerable interest from air forces and air arms all over Europe. Orders for the P.24 was received from Turkey and Romania in 1936, as well as from Bulgaria and Greece in 1937.

Exports
The 40 planes on the Turkish order was to be designated P.24c; fourteen armed with two 20 mm cannons and two 7.7 mm machine guns, the rest with four machine guns only. Limited license production of the P.24c was done by the Turks from 1937 onwards, bringing the total number of P.24c's in Turkish service to 60.

Romania's P.24 variant was designated P.24e and was similar to the P.24c except for the engine, which was license built by the Romanian company I.A.R. The Romanian P.24es got their baptism of fire over the Russian front after Romania joined Nazi Germany in the fight against USSR. Thus, the P.24 was one of the very few aircraft types to fight on both sides during World War II.

Bulgaria had 30 aircraft of the P.24f variant delivered in 1938. Their armament had the same setup as the Turkish P.24c; two machine guns and two 20mm cannons.

Finally, the Royal Hellenic Air Force of Greece ordered 30 of the P.24f and six of the P.24g variant. The P.24g had a 970 hp Gnome-Rhône radial engine housed in a new cowling. This low-drag cowling type appeared on many aircraft designs in the 1930's and was based on research done by NACA. Armament on the P.24g was four 7.7 mm machine guns which also became standard on Greek P.24f variants after tests discovered that the cannons damaged the aircraft's structure when fired.

...and fade
From 1935 onwards new types of aircraft began to appear, and the once world-class P.24 was dethroned by the Messerschmitt Bf 109, Hawker Hurricane and Supermarine Spitfire. Even though the P.24 gave Italy's Regia Aeronautica a run for its money in the closing months of 1940, Greece was ultimately defeated by the steamroller Nazi war machine.

It is unknown to me whether any P.24 aircraft have survived in museums or in private collections, but a P.11c is on display at the Polish Aviation Museum in Cracow.

Technical specifications
Specs are for the P.24f

• Powerplant: 970 hp (723 kW) Gnome-Rhône 14N.07 14-cylinder two-row radial engine
• Speed: 430 km/h at 14765 ft (4500 m)
• Service ceiling: 34450 ft (10500m). Climb to 5000m in 5m 40s.
• Range: 700 km on internal fuel tanks
• Weight: Max. takeoff weight 2000 kg
• Dimensions: wingspan 10.7 m, length 7.6 m, height 2.7 m, wing area 17.9 sq m