The P.Z.L. P.8 was a design for an improved inline engine powered of Zygmunt Pulawski’s gull wing fighters, but which never progressed beyond the prototype stage, and was abandoned in favour of the inline powered P.11.
The designer Zygmunt Pulawski’s first fighter design was the P.Z.L. P.1, which had introduced his distinctive gull wing design. The P.1 had been powered by an inline engine, and had a slab sided fuselage, but the Polish air force preferred radial powered aircraft, leading to the P.Z.L. P.7, which kept the gull wing but was powered by a licence built Bristol radial engine.
Pulawski was still interested in producing a more advanced version powered by an inline engine, which would allow for a narrower fuselage which would reduce drag and potentially improve the performance of the aircraft. He and his assistant Wsiewolod Jakimiuk continued to work on inline powered designs, and late in 1930 were give permission to built two prototypes of his new design, with the designation P.Z.L. P.8. The two aircraft kept the same basic layout of his earlier fighters, with a gull wing to give the pilot a better view, and a fixed undercarriage with part of the suspension mounted inside the fuselage. It had a slap sided fuselage with rounded tops and bottoms, and better streamlining than the original P.Z.L. P.1. Both prototypes were designed to carry twin 7.92mm machine guns.
The first prototype, P.8/I, was powered by a Hispano-Suiza 12Mc 12-cylinder supercharged water–cooled engine that had been supplied free by Hispano. This provided a maximum of 640hp, and was cooled by a ventral radiator bath carried underneath the fuselage, behind the wings. The engine cylinders were covered by a streamlined faring, with a gap between to give a view straight forward. It was lighter than the P.1. The P.8/I made its maiden flight in August 1931, and in tests reached a top speed of 205mph at sea level. This was almost 40mph faster than the P.7 at sea level, but the streamlined engine installation caused cooling problems which were never really solved.
The second prototype, P.8/II, was powered by a 500-800 Lorraine 12H Petrel water cooled engine that provided 675hp at 11,485ft. It was originally built with a radiator under the fuselage, but this was later replaced by two smaller flush fitting lateral panel radiators carried on the sides of the fuselage just behind the cockpit. It was modified to make it easier to produce. This second aircraft began its flight trials early in 1932.
The P.8/II won the Fighter Race at the International Aviation Meeting in Warsaw in June 1932, when it was piloted by Colonel Jerzy Kossowski. It was then entered into the 1932 Zurich Aviation Meeting, but developed problems early in the trip and had to make a forced landing. Her pilot, Captain Orlinski, returned to Warsaw to collect the P.8/I, but then crashed while landing at Innsbruck and the aircraft was written off. The P.8/II was repaired and went to the 1932 Salon International de l’Aeronautique in Paris, but that ended its career.
Sadly by the time the first prototype made its maiden flight Pulawski had been killed in an accident on 21 March 1931, while flying in the P.Z.L 12 amphibian. As a result the inline powered P.8 lost one of its main advocates. Even so the performance of the P.8/II was impressive enough for it to be considered for production. It could reach 217mph at sea level and 206mph at 12,467, significantly better than the 171mph at sea level and 197mph at 13,123ft of the P.6.
A number of inline engines were considered and two were selected for further development – the P.9 was to be powered by the Lorraine Petrel and the P.10 by the Rolls-Royce Kestrel. However the Polish aero-engine industry strongly objected to introducing inline engines after they had invested heavily in producing radial engines, and by the time the P.8/II appeared at Paris development of the P.9 and P.10 had been cancelled. Instead work moved onto the radial powered P.11, which was still in service when the Germans invaded in 1939.
Engine: Lorraine Petrel supercharged twelve-cylinder upright-vee water-cooled engine
Power: normal 500hp, maximum 80-0hp
Span: 34ft 5.5in
Length: 24ft 9.75in
Height: 9ft 0.25in
Empty Weight: 2,430lb
Loaded Weight: 3,467lb
Maximum Speed: 217.4mph at sea level, 206.2mph at 12,467ft
Climb rate: 7min 30sec to 16,404ft
Ceiling: 29,855ft (absolute)
Range: 310 miles
Guns: Two machine guns