PZL P.11

PZL P.11c
PZL P.11c
Description
Role	Fighter
Crew	1
First flight	August, 1931
Entered service	1934
Manufacturer	PZL
Dimensions
Length	7.55 m (7.25 m - P-11a)
Wingspan	10.72 m
Height	2.85 m (2.69 m - P-11a)
Wing area	17.9 m²	ft²
Weights
Empty	1,147 kg (1,116 kg - P-11a)
Loaded	1,650 kg (1,580 kg - P-11a)
Maximum takeoff	1,800 kg (? kg - P-11a)
Powerplant
Engines 1 x	Bristol Mercury
Power 1 x	Mercury IV S2 (P.11a)
	429 kW max	575 hp
Power 1 x	Mercury VI S2 (P.11c)
	470 kW max	630 hp
Performance
Maximum speed	375 km/h (340 km/h - P.11a)
Combat range	550 km (480 km - P.11a)
Ferry range	km
Service ceiling	8,000 m
Rate of climb	12.4 - 14.5 m/s
Armament
Guns	2 or 4 x 7.92 mm machine guns
Bombs	50 kg	lb

The PZL P.11 was the Polish fighter aircraft, designed in early-1930s by PZL in Warsaw. It was the main fighter in the Polish September Campaign.

Contents

1 Development

2 Combat use

3 Technical description

3.1 Specifications (variant described)

3.1.1 General characteristics
3.1.2 Performance

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 PZL 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 changed 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).

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. 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.

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 Polish September Campaign. Apart from combat units, several P.11, including a prototype P.11g, were used in units improvised at air bases.

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.

On the other hand, Polish planes had better maneouvreability. P.11 had a strong construction and also could operate from short fields, even rough ones. It was also of a very durable construction and could dive even at 600 km/h without risk of wings falling apart. Theoretically the only limit in maneouvres was the pilots ability to sustain high G. 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.

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.

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.

Specifications (variant described)

General characteristics

Crew:
Capacity:
Length: m ( ft)
Wingspan: m ( ft)
Height: m ( ft)
Wing area: m² ( ft²)
Empty: kg ( lb)
Loaded: kg ( lb)
Maximum takeoff: kg ( lb)
Powerplant: Engine type(s), kN (lbf) thrust or
Powerplant: Engine type(s), kW ( hp)

Performance

Maximum speed: km/h ( mph)
Range: km ( miles)
Service ceiling: m ( ft)
Rate of climb: m/min ( ft/min)
Wing loading: kg/m² ( lb/ft²)
Thrust/weight: or
Power/mass:

Related content
Related development	PZL P.7, PZL P.24, IAR-80
Similar aircraft	Dewoitine D.371 - Loire 46 - Ikarus IK-2 - Polikarpov I-15
Designation series	PZL-6 - PZL P.7 - PZL P.8 - PZL P.11 - PZL-12 - PZL-19
Related lists	List of fighter aircraft