PZL P.11

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PZL P.11c

The PZL P.11 was a Polish fighter aircraft, designed in early-1930s by PZL in Warsaw. It was, briefly, considered by many to be the most advanced fighter design in the world. It was the main fighter in the Invasion of Poland, but by this point was outdated due to rapid advances in aircraft design.

1 Development
2 Combat use
3 Technical description
4 Specifications (P-11c)
5 Operators
6 External link
7 Related content

[edit] Development

The history of PZL P.11 started in 1929, when a talented designer, Zygmunt Pulawski, designed an all-metal metal-covered monoplane fighter. While most of the world's forces were still using biplanes, the new P.1 used a high-mounted gull wing to give the pilot an excellent view. A second prototype, the P.6, was completed the next year. The design generated intense interest around the world, the layout becoming known as the "Polish wing" or "Pulawski wing". A further improvement, the PZL P.7, was built for the Polish Air Force in a series of 150.

After designing P.7, Pulawski started further developments with larger engines, leading eventually to the P.11. The first prototype P.11 flew in August 1931, after Pulawski's death in an air crash. It was followed by two slightly modified prototypes. The first variant ordered by the Polish airforce was P.11a, considered as an interim model and built in a series of 30. Otherwise similar to the P.7, it mounted the 575 hp (429 kW) Bristol Mercury IV S2 radial engine produced in Poland under licence.

The final variant for the Polish airforce, P.11c, had a new, refined fuselage, with the engine lowered in the nose to give the pilot a better view. The central part of wings was also modified. Production of P.11c started in 1934, and 175 were produced. The first series of approximately 50 P.11c were fitted with Mercury V S2 of 600 hp (447 kW), the rest with Mercury VI S2 of 630 hp (470 kW).

Such limited production may appear irresponsible on the part of the Polish government, with the Red Army aviation reaching into thousands and Germany ramping up production at unprecedented scale. Even without the new WP2 plant at Mielec the PZL works could produce at least 10 fighters every month. However, the Lotnictwo Wojskowe (Military Aviation) command was still studying different concepts of the use of fighters and bombers, while the Polish design bureaus were developing very advanced designs. The untimely death of Zygmunt Pulawski also complicated the matter.

Apart from Poland, Romania showed interest in the new design. Even before P.11a, 50 aircraft designated P.11b were produced for the Romanian Air Force and delivered in 1932. They were fitted with engines Gnome-Rhone 9Krsd Mistral 595 HP, otherwise similar to P.11a. After P.11c had been developed, the Romanians decided to buy a licence and produce the new model at IAR factory. As a result, from 1936 IAR built 70 aircraft as IAR P.11f with the slightly updated 9Krse of 610 hp. The Romanians then produced another Polish fighter, PZL P.24, developed from P.11 exclusively for export. Some other countries were interested in buying P.11, but finally Bulgaria, Greece and Turkey bought P.24 instead.

When P.11 entered service in 1934 it was arguably the most advanced fighter in the world. However, due to the quick progress in aircraft technology, they were obsolete by 1939. Unfortunately, they remained the only Polish fighters in service, totalling about 185, distributed within six air regiments and the aviation school in Deblin. Although they were aware that the P.11 was outdated, the Polish Air Force had pinned their hopes on the new PZL P.50 Jastrzab, which suffered extended delays. When it became apparent that the P.50 would not be in widespread service in time for a war that was clearly looming, consideration was given to producing an updated version with the 840 hp (626 kW) Mercury VIII and an enclosed cockpit, known as the P.11g Kobuz. Only the prototype of P.11g was flown before the war, in August 1939, increasing maximum speed to a still-slow 390 km/h (~240 mph).

[edit] Combat use

At the outbreak of the World War II, on September 1, 1939, the Polish Air Force had 109 PZL P.11c and 20 P.11a (and 30 P.7a) in combat units. Further 43 P.11c were in reserve or undergoing repairs. Only a third of P.11c were armed with 4 machineguns, the rest had only 2, even fewer had a radio. P.11 were used in 12 squadrons, each with 10 aircraft (two squadrons constituted a group, in Polish: dywizjon). Two groups - 4 squadrons - were in the Pursuit Brigade deployed around Warsaw, the rest were assigned to Armies. All of them took part in the Invasion of Poland. Apart from combat units, several P.11, including a prototype P.11g, were used in units improvised at air bases.

PZL P.11c from the Eagle Owls squadron. On 1st September 1939 Flight Lieutenant Hieronim Dudwał, flying this plane, shot down a German He-111 over Warsaw

By September 1, the fighter squadrons had been deployed to remote airfields, so they were not bombed by the Germans. During the campaign, P.11 fought against more modern German bombers and fighters. Not only were the German Bf 109 and Bf 110 faster and better armed, but also most German bombers were faster than P.11c as well. Since the planes were intensively used, their maximum speed was still lower than the theoretical 375 km/h. P.11a were in an even worse situation. Another serious defficiency was their small number which meant that missions involving groups larger than about 20 planes were rarely accomplished and reserve machines were practically unavailable.

On the other hand, Polish planes had better maneouvreability and because of its design it had much better vision, from the cockpit, than the German planes. P.11 had a strong construction, good rate of climb and could operate from short fields, even rough ones. It was also of a very durable construction and could dive at up to 600 km/h without risk of the wings falling apart. Theoretically the only limit in maneouvres was the pilots ability to sustain high G forces. Despite the German superiority, P.11 managed to shoot down a considerable number of German aircraft, including fighters, but suffered heavy losses as well. The exact numbers are not fully verified, but it appears that at least one German plane shot down for each P.11 lost (a figure of 141 German planes is often given as compared with 118 planes lost).

The first aircraft shot down in World War II, on September 1 at dawn, was a PZL P.11c of Capt. Mieczysław Medwecki shot down by a German Ju 87. The first Allied air victory was achieved 20 minutes later by Medwecki's wingman, Wladyslaw Gnys who shot down two Dornier Do 17E with his P.11c. It was also the first airplane to successfully ram an enemy plane in WWII. The first large air battle of World War II took place in the early morning of September 1 over the city of Nieporet in North-Western Poland when a German bomber group of about 70 Heinkel He 111 and Dornier Do 17 was intercepted by some 20 P-11 and 10 P-7 fighters and had to abandon their mission on Warsaw.

Most of P.11 were destroyed in 1939. 36 were withdrawn to Romania and were taken over by the Romanian Air Force. They were not used in combat, due to their obsolescence, and only small number was used for training while the rest were dismantled for spare parts. Some planes were used by the Germans for training. Two PZL P.11 were captured by the Red Army and used for testing. One landed in Hungary and was used as a glider towing plane by the University of Technology in Budapest. The sole surviving plane is on display in the Polish Aviation Museum in Cracow.

P.11 as on display in the Polish Aviation Museum

[edit] Technical description

The aircraft was conventional in layout, with high wings, all-metal, metal-covered. The cockpit was open. An internal fuel tank in a hull could be dropped in case of fire emergency. The armament was two 7.92mm machineguns on hull sides, some 1/3 of P.11c had additional two machineguns in wings. P-11c could carry four small 12.5 kg bombs (P.11a could not). The radial engines used were: P-11a: Bristol Mercury IV S2 (normal: 525 hp, maximum: 575 hp); P-11b: Gnome-Rhone 9Krsd (550 hp, max: 595 hp), P.11c: Bristol Mercury V S2 (565 hp, max: 600 hp) or Mercury VI S2 (590 hp, max: 630 hp), P.11f: Gnome-Rhone 9Krse (560 hp, max: 610 hp).

Note: the horsepower data of engines differ in publications.

[edit] Specifications (P-11c)

This aircraft article is missing some (or all) of its specifications. If you have a source, you can help Wikipedia by adding them.

General characteristics

Crew: 1
Capacity: Fighter
Length: 7.55 m (24 ft 9 in)
Wingspan: 10.72 m (35 ft 2 in)
Height: 2.85 m (9 ft 4 in)
Wing area: 17.9 m² (167 ft²)
Empty weight: 1,147 kg (2,529)
Loaded weight: 1,650 kg (3,638 lb)
Powerplant: 1× Bristol Mercury IV S2 or Mercury VI radial engine, 470 kW (630 hp)