PZL P.11

The PZL P.11 was a Polish fighter aircraft, designed in the early 1930s by PZL in Warsaw. It was briefly the most advanced fighter aircraft of its kind in the world. The PZL P.11 served as Poland's primary fighter defence in the Polish campaign of 1939, but with the rapid advances in aircraft design in the late 1930s (seen in such fighters as the Messerschmitt Bf 109, it proved outclassed by its rivals at the onset of the war.


PZL P.11
Class Aircraft
Type Fighter
Manufacturer PZL
Origin Poland
Country Name Origin Year
Poland 1931
Country Name Operational Year Retirement Year
Bulgaria View
Hungary View
Latvia View
Poland View
Romania View
Russia (USSR) View
ManufacturerName Production From Production To Quantity
PZL 325 View

The history of the PZL P.11 started in 1929, when a talented designer, Zygmunt Pulawski, developed 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 the P.7, Pulawski started further variants with larger engines, leading eventually to the P.11. The first P.11/I prototype flew in August 1931, after Pulawski's death in an air crash. It was followed by two slightly modified prototypes, the P.11/II and the P.11/III. The first variant ordered by the Polish Air Force was the P.11a, considered 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 air force, the 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 the wings was also modified. Production of the P.11c started in 1934 and 175 were produced. The first series of approximately 50 P.11c aircraft 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 an 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 the P.11a entered service with the Polish air force, 50 aircraft designated P.11b were ordered for the Romanian Air Force, while an agreement for licence production was agreed. Deliveries of Polish-built P.11bs to Romania commenced in October 1933. They were fitted with Gnome-Rhone 9Krsd Mistral 595 hp (444 kW) engines, otherwise they were similar to the P.11a. After the P.11c had been developed, the Romanians decided to switch the licence production to the new model. As a result, from 1936 IAR built 70 aircraft as the IAR P.11f, powered by the Romanian-built IAR-K-9 engine, which was a heavily modified version of the Gnome-Rhone 9K giving 640 hp (480 kW). The Romanians then produced another Polish fighter, the PZL P.24, developed from the P.11 exclusively for export. Greece, Portugal, Yugoslavia, Turkey and Republican Spain were interested in buying the P.11, but finally Bulgaria, Greece and Turkey bought the P.24 instead.

When the P.11 entered service in 1934, as a contemporary of the British Gloster Gauntlet and German Heinkel He 51 it was arguably the most advanced fighter in the world However, due to the quick progress in aircraft technology, the P.11 was obsolete by 1939, overtaken by cantilever designs with retractable landing gear such as the British Supermarine Spitfire and German Messerschmitt Bf 109. Together with the older P.7, both remained the only Polish fighters in service, however, with about 185 P.11s available, distributed within six air regiments and the aviation school in Deblin. Although aware that the P.11 was outdated, the Polish Air Force had pinned their hopes on the new PZL.50 Jastrzab, which suffered extended delays. When it became apparent that the PZL.50 would not be in widespread service in time for a war that was clearly looming, consideration was given to producing an updated P.11 version with the 840 hp (626 kW) Mercury VIII and an enclosed cockpit, known as the P.11g Kobuz. Only the prototype of the P.11g with a maximum speed increase to a still-slow 390 km/h (~240 mph) was flown before the war, in August 1939.

In light of the unavailability of PZL.50, the only hope of replacing the obsolete P.11 lay in acquiring modern fighters from abroad. In 1939, after receiving the necessary credits, Poland ordered from France 120 Morane-Saulnier M.S.406s, and from Britain, 14 Hurricane Is (the P.11's chosen replacement), plus one Spitfire I for testing, in addition to 100 Fairey Battle light bombers. None of these aircraft were delivered to Poland before September 1939.

At the outbreak of the Second World War, on 1 September 1939, the Polish Air Force had 109 PZL P.11cs, 20 P.11as and 30 P.7as in combat units. A further 43 P.11c aircraft were in reserve or undergoing repairs. Only a third of P.11c were armed with four machine guns, the rest had only two, even fewer had a radio. The P.11 were used in 12 squadrons, each with 10 aircraft (two squadrons constituted a group, in Polish: dywizjon). Two groups—four squadrons—were in the Pursuit Brigade deployed around Warsaw, with the rest assigned to various armies. All of them took part in the 1939 defense of Poland. Apart from combat units, several P.11 aircraft, including a prototype P.11g, were used in improvised units at air bases.

By 1 September 1939, the fighter squadrons had been deployed to remote improvised airfields and therefore protected from German air attack on the ground. The P.11 would be up against more modern German bombers and fighters— not only were the German Messerschmitt Bf 109 and Bf 110 faster and better armed, but most German bombers were also faster. Since the P.11 fighters had seen years of intensive use before the war, their maximum speed was even lower than the theoretical 375 km/h. The P.11a's were in even worse condition. In addition, their small total number meant that missions of groups larger than 20 aircraft were rarely undertaken, and reserve machines were practically non-existent.

On the other hand, the Polish fighter aircraft featured better maneuverability over their German counterparts and, because of their design, much better vision from the cockpit. The P.11 also had a durable construction, a good rate of climb and could take off from short airfields, even of the rough and improvised variety. It could also dive at up to 600 km/h without risk of the wings breaking off. Theoretically the only limit in maneuvers was the pilot's ability to sustain high g forces. Despite the German superiority, the 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. A total of 285 German aircraft were lost according to Luftwaffe records, with at least 110 victories credited to the P.11 for the loss of about 100 of their own. Some of the German aircraft shot down were later recovered and put back into service. This allowed German propaganda to claim smaller combat losses.

At dawn on 1 September, Capt. Mieczyslaw Medwecki flying a PZL P.11c was shot down by Rottenführer (Foreman Leader) Leutnant Frank Neubert of I./StG 2 (Stuka), having the dubious honour of becoming the first aircraft shot down in the Second World War. The first Allied air victory was achieved 20 minutes later by Medwecki's wingman, Wladyslaw Gnys who shot down two Dornier Do 17s with his P.11c. The PZL P.11c was also the first aircraft to successfully ram an enemy aircraft in the Second World War. The first large air battle of the War took place in the early morning of 1 September over the village of Nieporet just north of Warsaw, 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 to Warsaw.

Most of the P.11s were destroyed in 1939, though 36 were flown to Romania and taken over by the Romanian Air Force. Due to their obsolescence, these veteran aircraft were not used in combat; only a small number was used for training while the rest were dismantled for spare parts. Some aircraft were used by the Germans for training. Two PZL P.11s were captured by the Red Army and used for testing. One landed in Hungary (near the town of Hajdúböszörmény) and was used as a glider tow plane by the University of Technology in Budapest.

Role Fighter
Manufacturer PZL
Designer Zygmunt Pulawski
First flight August 1931
Primary users Poland
Romania
Number built 325
Developed from PZL P.7
Variants PZL P.24


General characteristics

  • Crew: 1
  • Length: 7.55 m (24 ft 9 in)
  • Wingspan: 10.719 m (35 ft 2 in)
  • Height: 2.85 m (9 ft 4 in)
  • Wing area: 17.9 m2 (193 sq ft)
  • Empty weight: 1,147 kg (2,529 lb)
  • Gross weight: 1,630 kg (3,594 lb)
  • Max takeoff weight: 1,800 kg (3,968 lb)
  • Powerplant: 1 × Bristol Mercury V.S2 9-cyl. air-cooled radial piston engine, 420 kW (560 shp) or 1x 481 kW (645 hp) Polish Skoda Works Mercury VI.S2
    P.11a - 370.6 kW (497 hp) – 385.5 kW (517 hp) Polish Skoda Works Mercury IV.S2
    P.11b – 391.5 kW (525 hp) Gnome-Rhône 9K Mistral or I.A.R. 9K Mistral
    P.11f – 443.7 kW (595 hp) I.A.R. 9K Mistral
    P.11g – 626.37 kW (840 hp) P.Z.L. Mercury VIII
  • Propellers: 2-bladed Szomanski fixed pitch wooden propeller

Performance

  • Maximum speed: 390 km/h (242 mph; 211 kn) at 5,000 m (16,404 ft), 300 km/h (186 mph) at sea level
  • Stall speed: 98 km/h (61 mph; 53 kn)
  • Range: 700 km (435 mi; 378 nmi)
  • Service ceiling: 8,000 m (26,247 ft) absolute ceiling 11,000 m (36,089 ft)
  • Time to altitude:
    5,000 m (16,404 ft) in 6 minutes
    7,000 m (22,966 ft) in 13 minutes
  • Wing loading: 91.1 kg/m2 (18.7 lb/sq ft)
  • Power/mass: 0.279 kW/kg (0.166 hp/lb)

Armament

  • Guns:
    P.11a,b,c - 2 x 7.92 mm (0.312 in) KM Wz 33 or KM Wz 37 machine guns with 500rpg.
    P.11c - optionally an extra 2 × 7.92 mm (0.312 in) KM Wz 33 machine guns with 300rpg.
    P.11f - 4 x 7.92 mm (0.312 in) FN Browning machine guns.
    P.11g - 4 x 7.92 mm (0.312 in) KM Wz 36 machine guns.

End notes