|First flight||October 1930|
|Developed from||PZL P.6|
The PZL P.7 was the Polish fighter aircraft designed in early-1930s in the PZL factory in Warsaw. A state-of-the-art construction, one of the first all-metal monoplane fighters in the world, in 1933–1935 it was a main fighter of the Polish Air Force. It was replaced in Polish service by its follow-up design, the PZL P.11c. More than 30 P.7 fighters remained in service in the Invasion of Poland, scoring several kills despite their obsolescence.
Design and development
The history of the PZL P.7 started in 1928, when a talented designer, Zygmunt Puławski designed an all-metal, metal-covered monoplane fighter, the PZL P.1. It introduced a high gull wing, giving a pilot an optimal view. The wing design was called the "Polish wing" or "Pulawski wing". The P.1 was powered by an inline engine, and developed a speed of 302 km/h, but remained a prototype, because a decision was made to use a licence produced radial engine in the Polish Air Force fighters. Therefore, the next model, the PZL P.6, flown in August 1930, was powered by the Bristol Jupiter VI FH radial engine. Both aircraft were well received in the aviation world with the press recognizing the P.6 as one of the world's top fighters; it won the American National Air Races in August–September 1931.
The PZL P.6 did not enter production, because the next variant, the more advanced PZL P.7 was developed. The first prototype was basically the P.6 with a more powerful Bristol Jupiter VII F engine. Due to the use of a supercharger, it had better performance at higher altitude. The prototype P.7/I was first flown in October 1930 by Bolesław Orliński. Initially engine cylinders had individual cylinder clearance fairings. After some changes, most noticeably adding a wide Townend ring to the engine and making the tail slimmer, the second prototype P.7/II, built in autumn 1931, was accepted for production with the designation P.7a. It also featured a redesigned wing with slightly increased span, taken from the PZL P.8, and featuring shorter ailerons and smooth upper surfaces instead of ribbed ones.
The first series P.7a were built in mid-1932, the whole series of 149 (plus two prototypes) was completed in 1933. They carried military serial numbers 6.1 to 6.150 (the first prototype P.7/I had no number assigned). The Polish Air Force received the P.7a in 1933.
After designing the P.7, Puławski started to develop his design with more powerful engines, and the result was the PZL P.11, built in a production series. Puławski personally was an inline engine fan, designing a new fighter, the P.8, with a slim silhouette, powered with an inline engine. It was able to reach a speed of 350 km/h. A planned variant was to be designated the P.9. Unfortunately, in March 1931 Puławski died in an air crash, and the inline engine fighter design was cancelled in a favour of the radial engined P.11. The P.11 became the standard Polish fighter. In parallel with the P.11, the PZL P.24 export variant was also developed in 1932.
The all-metal, duralumin metal-covered monoplane aircraft was conventional in layout, with braced, high gull wing and fixed undercarriage with a rear skid. The two-spar wing of trapezoid shape, thinner by the fuselage, was covered with a rimmed Wibault type duralumin sheet (upper surfaces were smooth) and supported by two struts on either side. The fuselage was framed in a front section and semi-monocoque in mid and tail sections, oval in cross-section. In keeping with the period, the pilot's cockpit was open with a windshield. The armament was two 7.92 mm machine guns mounted on the fuselage sides (initially 7.7 mm Vickers E, then re-bored to 7.92 mm). The aircraft was powered by the Bristol Jupiter VII F radial engine (normal power: 480 hp (360 kW), maximum: 520 hp (390 kW) and fitted with a Townend ring and two-blade propeller. A main 290 l fuel tank in the fuselage, behind engine, could be dropped in case of fire emergency. The second fuel tank was 7 l.
The PZL P.7a entered service in spring 1933, replacing PWS-A (licence Avia BH-33) and PWS-10 fighters. Consequently, the Polish Air Force became the world's first air force entirely equipped with all-metal monococque fighters. When the P.7 entered service, it was a modern fighter, comparable to or better than contemporary designs, but due to rapid progress in an aircraft technology, it became totally obsolete by 1939. From 1935, in most combat units the P.7 was replaced by the PZL P.11, which was only slightly more modern. The P.7as were then moved to air schools.
At the outbreak of the World War II on 1 September 1939, the Polish Air Force still had 30 PZL P.7a fighters in combat units. A further 40 were in air schools, 35 in reserve or repairs – a total of 106 available aircraft. The P.7as were used in three squadrons, each with 10 aircraft. The 123rd Squadron was in the Pursuit Brigade, deployed around Warsaw, the 151st and the 162nd Squadrons were assigned to land Armies. Despite being obsolete, they took part in the defence of the country during the German Invasion of Poland. Apart from combat units, at least 18 P.7a fighters were mobilized in units improvised at air bases in Dęblin and Ułęż.
Although the P.7 had better manoeuvrability than their German opponents and could operate from short fields (150 m to start), even rough ones, almost all the German aircraft were faster than the P.7a. Furthermore, the Polish aircraft and their engines were worn out from intensive service use. Their armament was also insufficient - only two Vickers machine guns in most aircraft, which had a tendency to jam (only from aircraft number 6.109 they were replaced with better PWU FK wz.33). For these reasons, the pilots flying the P.7a claimed shooting down only seven German aircraft (two He 111s, two Do 17s, one Hs 126 and two Bf 110s), suffering combat losses of 22 aircraft. An improvised task force of P.7a aircraft from units at air bases was rather to confuse and disturb the German bombing raids with their aggressive presence, than to shoot down bombers.
Most of the P.7a fighters were destroyed in 1939, in combat or on the ground, some dozen were withdrawn to Romania, but not used in combat there. Some captured P.7s were used by the Germans for training. Several aircraft were captured by the Soviets (exact number is not known) and were next assigned for training.
- First prototype.
- Second prototype equipped with Townend ring.
- Serial built version.
- Luftwaffe operated few captured aircraft for training.
- Royal Romanian Air Force operated few interned aircraft for training.
Specifications (PZL P.7)
- Crew: 1
- Capacity: fighter
- Length: 6.98 m (22 ft 11 in)
- Wingspan: 10.57 m (34 ft 8 in)
- Height: 2.69 m (8 ft 10 in)
- Wing area: 17.9 m² (193 ft2)
- Empty weight: 1,090 kg (2,400 lb)
- Loaded weight: 1,476 kg (3,254 lb)
- Useful load: 386 kg ()
- Powerplant: 1 × Bristol Jupiter VIIF 9-cylinder radial engine, 520 hp (388 kW)
- Maximum speed: 327 km/h (203 mph)
- Cruise speed: 285 km/h
- Stall speed: 104 km/h ()
- Range: 600 km (370 mi)
- Service ceiling: 8,500 m (27,900 ft)
- Rate of climb: 62.4 m/min (10.4 m/s) (2047.2 ft/min)
- Wing loading: 82.5 kg/m² ()
- 2 x 7.9 mm Vickers E machine guns (later series: PWU FK wz.33 machine guns)
- Related development
- Aircraft of comparable role, configuration and era
- Morgała, Andrzej (2003): Samoloty wojskowe w Polsce 1924-1939. Warszawa: Bellona. ISBN 83-11-09319-9, pp.48-54 (in Polish)
- PZL P.7/P.11/P.24 series Note: The P.11 was a natural progression of the P.7 series while not a true variant.
- Murphy and McNiece 2009, pp. 18–19.
- Kotelnikov, Vladimir. "Lotnictwo w wojnie polsko-sowieckiej we wrześniu 1939 r.(in Polish)" Lotnictwo Wojskowe, May 1999.
- Cynk, Jerzy B. History of the Polish Air Force 1918-1968. Reading, Berkshire, UK: Osprey Publishing Ltd., 1972.
- Cynk, Jerzy B. Polish Aircraft, 1893-1939. London: Putnam & Company Ltd., 1971. ISBN 0-370-00085-4.
- Eberspacher, Warren A. and Jan P. Koniarek. PZL Fighters Part One - P.1 through P.8. (International Squadron Monograph 2). St. Paul, MN: Phalanx Publishing Co., Ltd., 1995. ISBN 1-883809-12-6.
- Glass, Andrzej. Polskie konstrukcje lotnicze 1893-1939 (in Polish: "Polish aviation constructions 1893-1939"). Warszawa, Poland: WKiŁ, 1977. no ISBN.
- Glass, Andrzej. PZL P.7: Cz.1. Gdańsk, Poland: AJ Press, 2000. ISBN 83-7237-080-X.
- Kopański, Tomasz J. PZL P.7: Cz.2. Gdańsk, Poland: AJ Press, 2001. ISBN 83-7237-081-8.
- Murphy, Justin D. and Matthew A. McNiece. Military Aircraft, 1919-1945: An Illustrated History of their Impact. Santa Barbara, California: ABC-CLIO, 2009. ISBN 1-85109-498-9.
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