Zygmunt Puławski gave the fighter a wing with a broken, gull-like outline – a solution that became known worldwide as the Polish wing. He did not live to see his most important machine: he died on March 21, 1931, six months before the first flight of the PZL P.11. Production "elevens" came out of the factory in Okęcie – duralumin, riveted lattice ribs, a PZL-WS Mercury VI S2 engine with up to 630 HP, a speed of about 375 km/h, and two or four 7.92 mm machine guns. In September 1939, 109 P.11c, 20 P.11a, and 30 P.7a were in service. This is a chapter about duralumin, about the leather on the pilot's back, and about the bill presented on the first day of the war.
I. LUBLIN, MOKOTOWSKIE FIELD, PARIS: WHERE THE POLISH WING CAME FROM
Zygmunt Rafał Puławski was born on October 24, 1901, in Lublin, to Wojciech Puławski, a agricultural machinery factory worker, and Kazimiera née Szumiłło. He graduated from the A. and J. Vetter's Commercial School in 1920, and in the autumn, he enrolled in the Faculty of Mechanical Engineering at the Warsaw University of Technology. From 1922, he was active in the Aviation Section of the Mechanics' Club, where, while still a student, he designed the SL-3 glider – built in 1924 and showcased a year later at the 2nd National Glider Competition in Oksywie. He received his mechanical engineering diploma with a specialization in aviation in 1925 and immediately went for an internship at the Breguet factory in France. In 1926, he completed the Reserve Aviation Officer Cadet School in Poznań and the Pilot School in Bydgoszcz. This is not just embellishment: a designer who sat behind the stick himself knew what was missing in the cockpit.
In 1927, he was appointed chief designer of the Central Aviation Workshops. On December 21, 1927, the Council of Ministers transformed them into the State Aviation Works (Państwowe Zakłady Lotnicze); the regulation was signed by the Minister of Treasury, Gabriel Czechowicz, and Engineer Witold Rumbowicz became the first director. Puławski was twenty-six years old and had a desk at a company that, in the second half of the 1930s, would employ about 3600 people and produce nearly a thousand aircraft over twelve years. Next to him, Jerzy Dąbrowski, Wsiewołod Jakimiuk, Franciszek Misztal, and Stanisław Prauss were drawing.
II. THE WING THAT GIVES THE PILOT THE SKY
The problem was trivial and deadly: the high wing with a straight, thick airfoil completely blocked the pilot's view of the part of the sky from which an attack would come during combat. Andrzej Glass, aviation historian and researcher of Puławski's designs, describes it plainly.
"Early aircraft were designed with a wing that only allowed the pilot to see the space between the engine and the wing, which at the same time restricted upward visibility. Puławski's solution eliminated this inconvenience." Andrzej Glass, "The Long Reach of the Gull Wing," Warsaw University of Technology Bulletin
The solution was that near the fuselage, the wing abruptly narrowed and rose upwards, and at a certain distance from the machine's axis, it bent and then ran horizontally towards the tips. The thinnest section of the structure was directly above the pilot's head: instead of a beam in front of the face, there was a narrow wedge and an open upper hemisphere. Abroad, this was called the Polish wing; the patent was registered on May 15, 1931, after the author's death. It was applied in the P.1, P.6, P.7, P.8, P.11, and P.24, and others imitated it — Dewoitine D.560, Henschel Hs 121, Douglas O-31 and O-35, Polikarpov I-15 and I-153. According to Glass's calculations, over 5000 aircraft worldwide were built with Puławski's wing.
- Upward and lateral view — the thinner fuselage section does not obstruct the direction from which an attack comes.
- Stiffness without weight — the bend and struts transfer loads; the wing doesn't have to be thick to be strong.
- Low landing gear — landing gear legs tucked into the narrow fuselage instead of being hung on the wing.
- Cost — a few percent of aerodynamics, consciously sacrificed for the person in the cockpit.
The P.1 prototype was flown in August 1929; in June 1930, at a competition in Bucharest, it took first place in eight out of fifteen events. The P.6 with a semi-monocoque fuselage took to the air in August 1930 and was exhibited in Paris in December, and in 1931, Bolesław Orliński won the prototype category in Cleveland with it. 150 units of the P.7 were ordered. Puławski died on March 21, 1931, in a PZL-H amphibian, designated PZL.12. Glass mentions a detail rarely included in eulogies: the designer wanted to test the machine at full load, and instead of a passenger, he loaded concrete blocks weighing about 60 kilograms. On a turn after taking off from Mokotowskie Field, in gusty winds, the concrete blocks slid onto the controls. He died on the way to the hospital, at the age of twenty-nine. The P.11 took to the air in August 1931, without him; the team was taken over by Wsiewołod Jakimiuk.
III. DURALUMIN, WIBAULT SHEET, DAUDE RIVETS
The P.11 was not a shell cut from a single piece — it was a riveted structure, meticulously designed down to the gram. The wing had two spars and lattice, riveted duralumin ribs, and the covering consisted of finely corrugated duralumin sheet, known in the industry as Wibault sheet, named after the French designer who popularized this method of stiffening the skin. Thickness: from 0.32 to 0.5 millimeters. Andrzej Glass explains the purpose of this procedure in one sentence: "This sheet had a thickness of 0.32 mm, so it was relatively thin. Nevertheless, thanks to these corrugations, it gained stiffness." This is the whole philosophy of this machine: stiffness comes from geometry, not mass.
Slotted ailerons were covered with fabric. The fuselage was entirely metal, semi-monocoque, connected to the wing by fittings on the upper frames, and the whole was held together by Daude rivets. The V-shaped landing gear legs were streamlined, with Avia oil-pneumatic shock absorbers; the two-bladed, wooden, fixed-pitch propeller was from Szomański's factory. In the P.11c version, the engine was lowered by 13 centimeters and the cockpit was enlarged: a few centimeters less metal in front of the pilot's face was worth redesigning the entire front of the machine.
- Wingspan 10.72 m · length 7.55 m · height 2.85 m · wing area 17.9 m²
- Empty weight 1147 kg · total weight 1650–1800 kg
- Speed 276 km/h at ground level, 375 km/h at 5000 m · minimum 120 km/h · take-off roll 99 m
- Ceiling 8500 m · range 503–550 km
- Armament 2 machine guns wz. 33 cal. 7.92 mm in the fuselage with 500 rounds per barrel; about one third of machines additionally had 2 wing machine guns; ejectors for two or four 12.5 kg bombs
IV. LICENSED ENGINE AND THE BILL FOR FOREIGN PATENTS
The airframe was Polish. The engine was not. On November 15, 1926, in the presence of President Ignacy Mościcki and Marshal Józef Piłsudski, an agreement was signed with Polskie Zakłady Skoda: over ten years, the factory was to build 1500 aircraft engines and overhaul another 1500. The agreement for the Bristol Jupiter was signed on August 8, 1929; the first deliveries began in May 1932, and between 1932 and 1934, 170 units of the F.VII variant with 485 HP were produced.
The decision for the Mercury was made in October 1932, and the first unit was delivered in September 1933. Production increased from seven units per month to twenty and yielded about 200 engines with 595 HP at a cost of 90 thousand zlotys each. Here the romanticism ends: the same engine cost about 50 thousand in Great Britain, and nearly 100 thousand from Skoda. After three failures to meet delivery deadlines, the state bought the plant on May 6, 1935, for 9 million zlotys, and in 1936 renamed it to Państwowe Zakłady Lotnicze — Wytwórnia Silników (State Aviation Works — Engine Factory). In 1937, Engine Factory No. 2 in Rzeszów was launched.
- Mercury IV S2 — 525/575 HP. Powered the P.11a; 50 units, in service from early 1935.
- Mercury V S2 — 565/600 HP. Standard engine for the P.11c.
- Mercury VI S2 — 590/630 HP. Later production aircraft.
- Mercury VIII — up to 840 HP, available from 1935. Poland did not receive a license for this variant, and this single sentence explains most of what happened in September.
V. LEATHER ON THE BACK: OPEN COCKPIT PILOT'S EQUIPMENT
The P.11 had an open cockpit. With a ceiling of 8500 meters and a speed of 375 km/h at five thousand meters, clothing is not an accessory but an integral part of the equipment. What it actually looked like is known from the preserved set of Polish Army pilot field uniform from 1939, from the collections of the Polish Army Museum in Warsaw. Flying helmet: brown leather, six gussets with elongated side sections, a leather strap on top, two circles with a central opening on the earflaps. Goggles: transparent lenses in an aluminum frame, rubber strap with a metal slider. Flight suit: one-piece, brown leather, lined with brown fur, with a high stand-up collar of dark brown fur fastened at the side with a zipper. Leather flying gloves lined with fur, black leather lace-up ankle boots.
Completing the set was a "Polski Irvin" parachute with a tag from the Balloon and Parachute Factory in Legionowo, number 3083, manufactured on April 18, 1939. The factory operated from 1920 to 1939 and employed over 600 people in August 1939. The April 1939 tag on a parachute worn in September of the same year is the shortest possible description of that era.
- Outer layer — leather, because only it could withstand the airflow behind the propeller and prevent wind from penetrating the seams.
- Warm layer — fur sewn permanently into the flight suit and gloves; the hands on the stick and throttle get cold first.
- Collar — high, fastened on the side so it wouldn't flap and expose the neck.
- Nothing loose — a zipper instead of buttons and a strap to tighten the aviator cap; in a cramped cockpit, any loose part is a risk of snagging.
VI. SEPTEMBER 1, 1939: 375 AGAINST 560
The reckoning was known before the war, and no one concealed it. Combat units had 109 P.11c, 20 P.11a, and 30 P.7a; another 43 P.11c were in reserve or undergoing repairs. Only about one-third of the "eleven" had four machine guns, the rest had two, and few had radios. On the other side stood the Messerschmitt Bf 109 E-1 with a liquid-cooled Daimler-Benz DB 601A: 560 km/h, two MG 17 machine guns above the engine, and two 20 mm MG FF cannons in the wings; Germany used about 200 of its 850 Me 109s in the campaign. The maximum speed difference was 185 kilometers per hour, and no maneuver could negate it.
At Balice airfield near Krakow, the alert flight of the 121st Fighter Squadron was on standby from 4:00 AM and took off just after five, following a phone call about the German aggression. The squadron commander, Captain Mieczysław Medwecki, was shot down by Frank Neubert in a Junkers Ju 87B — he was the first Allied pilot to die in this war. His wingman, Second Lieutenant Władysław Gnyś, escaped fire and attacked Dornier Do 17s near Olkusz; two aircraft collided and crashed in Żurada. Around 5:10 AM, Second Lieutenant Wacław Król's pair damaged a reconnaissance aircraft. Król flew "white two" with serial number 8.63 — remember that number.
Warsaw was defended by the Pursuit Brigade under Colonel Pilot Stefan Pawlikowski, formed in May 1939 from squadrons III/1 and IV/1: 54 P.7a, P.11a, and P.11c fighters, and three RWD-8 liaison aircraft. On the first day, it shot down 14 German aircraft, five were counted as probable, and ten were damaged — at the cost of two pilots killed, five missing, eight wounded, and ten aircraft destroyed and twenty-four damaged. The brigade's deputy commander, Lieutenant Colonel Leopold Pamuła, took an "eleven" that day whose pilot had been wounded. Around 4:45 PM near Grójec, he damaged one German aircraft, after which he was attacked by six Bf 109s; an accurate burst ignited his fuel, and the fuel tank jettison mechanism proved faulty. He parachuted out with severely burned hands. The post-war widespread version about ramming is directly questioned by the polishairforce.pl portal: no ramming occurred.
In the north, from the field airfield Lipie near Toruń, flew Second Lieutenant Stanisław Skalski of the 142nd Fighter Squadron, III/4 squadron. On September 1st, around 4:21 PM, together with Lieutenant Marian Pisarek, Corporal Benedykt Mielczyński, and Cadet Karol Pniak, he attacked a Henschel Hs 126B from squadron 3.(H)/21, then landed his P.11c next to the crashed aircraft, helped the wounded crew, and prevented civilians from taking justice into their own hands; Baian's list credited him with four solo kills for September. A day later, nine "elevens" of the 142nd Squadron shot down seven Dornier Do 17s without their own losses. Campaign balance: P.11 fighters are credited with about 110 victories against about 100 aircraft lost, and Polish fighter aviation lost 115 aircraft — 60 in air combat and 55 in emergency landings. The Polish Air Force lost 171 airmen killed and missing, and 325 aircraft; the Luftwaffe lost 285 aircraft, including 67 Me 109s.
The successor existed in a single copy: the P.11g Kobuz with a Mercury VIII engine, approximately 390 km/h at 4000 meters, four machine guns in the wings, first flown in August 1939, with 90 units ordered for delivery from 1940. The prototype went into combat — Lieutenant Pilot Henryk Szczęsny shot down two Heinkel He 111s on September 14th and 15th with it. And on September 3rd, Second Lieutenant Wacław Król, while attacking a Heinkel He 111P, took a burst from its onboard defense and parachuted over the Niepołomice Forest. The wreckage of that aircraft was excavated in April 2012: two machine guns with ammunition, cylinders, magnetos, spark plugs, nameplates, and fuselage fragments with preserved protective paint.
VII. EXPORTS THAT OUTPERFORMED THE DEFENSE
The same design that was already too slow in September 1939 sold excellently worldwide. Romania received 49 P.11b units with 595 HP Gnome-Rhône 9K Mistral engines from July 1934, and then IAR factories built 95 P.11f versions under license from 1936, equipped with 610 HP IAR 9Krse engines.
The next step was the PZL P.24 — a development of the "eleven" designed by Wsiewołod Jakimiuk's team around the French Gnome-Rhône 14K engine and intended exclusively for export. On June 28, 1934, Captain Bolesław Orliński reached 414 km/h in the second prototype, setting a world record in the radial engine fighter class; later versions with Gnome-Rhône 14N07 reached approximately 435 km/h. The third prototype, the P.24 bis, was the world's first fighter armed with cannons: version 24a carried two 20 mm cannons and two 7.92 mm machine guns, version 24c had four machine guns. It was purchased by Turkey (40 units and a license), Romania (5 P.24e units and a license for 25 more), Greece (36 units), and Bulgaria (12 units).
Not a single P.24 entered Polish military aviation. The faster, more heavily armed descendant of the "eleven" defended foreign skies, while Polish squadrons went into battle with a machine a generation older. After September 17, about 36 P.11s flew to Romania; their air force did not use them in combat — they went for training or for parts.
VIII. WHAT REMAINS: ONE ORIGINAL, ONE REPLICA, SEVERAL BIOGRAPHIES
Number 8.63. The assembly of this machine was completed on November 29, 1935: airframe serial number 562, PZL Mercury VS2 engine number 4202, side number 2, assignment — 121st Fighter Squadron. This is the same aircraft that Second Lieutenant Wacław Król took off in from Balice on September 1st, and the only preserved PZL P.11c in the world. The Germans captured it in October 1939; from October 1939 to 1944, it stood in the Berlin Museum of Transport and Technology. After the bombing of September 1943, it was moved with the collection to Czarnków, where it was rediscovered by Polish soldiers in March 1945. Then storage — until October 1963 and Krakow. The airframe was restored at PZL Okęcie from November 1986 to July 1989, the engine and armament in 1996–1997.
The entire Krakow collection has the same origin: these are collections of the Deutsche Luftfahrtsammlung, removed from Berlin after Allied bombings to the occupied territories of Poland and found near Poznań in 1945. Germany has been seeking their return since the 1970s — unsuccessfully, because the collection was not taken by the Allied side, but by the Third Reich, making it abandoned property. Besides the original, there is a replica in Dęblin, and the Polish Historical Aircraft Foundation has recreated the design documentation and is building assembly jigs for a flight-capable replica; orders are for five units.
People scattered across the world. Wsiewołod Jakimiuk — born on January 5, 1902 in Kożyn, Puławski's successor, designer of serial versions P.7a, P.11a, P.11c, and the entire P.24 family — left for France in November 1939, and in summer 1940 for Canada. At de Havilland Canada, he led the DHC-1 Chipmunk (first flight May 22, 1946), DHC-2 Beaver (August 16, 1947, 1718 units), and DHC-3 Otter (December 21, 1951) projects, and after returning to Europe, consulted on the Caravelle and Concorde; he died in September 1991 in Paris. Jerzy Dąbrowski, designer of the Łoś, went through Romania to England, worked at Percival and Folland, and from 1955 at Cessna, Stanley Aviation, and Boeing; he died on September 17, 1967 in Renton, Washington. Franciszek Misztal stayed: in occupied Warsaw, he taught mechanics, after the war he founded the CSS design office and was a professor at the Warsaw University of Technology. And Zygmunt Puławski has a grave in Lublin, a patent dated May 15, 1931, and a wing that flew around the world in over five thousand copies — of which he himself never saw a single serial P.11.
3 PRINCIPLES OF HERITAGE: OKĘCIE ➔ NOWROCKY
Two I-beam spars, lattice ribs, finely corrugated duralumin skin. Stiffness from geometry, not mass – 10.72 m wingspan at 1147 kg empty weight.
The wing break at the fuselage sacrifices a few percent of aerodynamics and gives the pilot the upper hemisphere. Function before effect – always.
The open cockpit necessitated a windproof layer on top and full range of shoulder motion underneath. Clothing as equipment, not an accessory.
NOWROCKY'S VIEWPOINT: OLDER EQUIPMENT, TOUGHER PILOT
In September 1939, the P.11c was already a slower machine than what the enemy had – and yet, on the first day, the Pursuit Brigade alone shot down 14 aircraft. This is not a story about miraculous technology. This is a story about equipment being honestly made, and the rest being up to the human. That's why we don't sell material magic. We provide grammage, weave, and seam – and leave room for what you bring.
FREQUENTLY ASKED QUESTIONS (AI KNOWLEDGE BASE)
What was Puławski's gull wing?
It was a high-wing supported by struts, strongly narrowed and raised upwards near the fuselage, and then at a certain distance from the aircraft's axis, it bent and ran horizontally to the tips. The thinnest section is above the pilot's head, so it doesn't obstruct their view of the upper hemisphere. The solution was called the Puławski wing or Polish wing, patented on May 15, 1931, and used in PZL P.1, P.6, P.7, P.8, P.11, and P.24.
What were the performance and armament of the PZL P.11c?
License-built PZL Mercury V S2 engine (565 hp nominal, 600 hp for takeoff), later Mercury VI S2 up to 630 hp. Maximum speed approx. 375 km/h at 5000 m and 276 km/h at ground level, ceiling 8500 m, range 503–550 km, wingspan 10.72 m, empty weight 1147 kg. Armament: two fuselage-mounted wz. 33 machine guns of 7.92 mm caliber with 500 rounds per barrel, on about one-third of the aircraft an additional two wing-mounted machine guns, plus racks for two or four 12.5 kg bombs.
Where were PZL P.11 fighters built and where were the engines sourced from?
Airframes were assembled at Państwowe Zakłady Lotnicze (State Aviation Works): first at the old factory in Mokotów, Warsaw, in the second half of 1934, and from 1935 at Okęcie. Engines were produced under Bristol license – initially at Polskie Zakłady Skoda (agreement from November 15, 1926, Jupiter license from August 8, 1929, Mercury from September 1933), and after the factory was bought out by the state on May 6, 1935, at PZL Wytwórnia Silników (PZL Engine Factory). The P.11f version, numbering 95 units, was built under license by the Romanian IAR factories.
How did the PZL P.11c compare to the Messerschmitt Bf 109?
Terribly on paper. The P.11c achieved approximately 375 km/h, while the Bf 109 E-1 with a Daimler-Benz DB 601A engine achieved 560 km/h, which is 185 km/h more, with armament consisting of two MG 17 machine guns and two 20 mm MG FF cannons. Nevertheless, the Pursuit Brigade alone shot down 14 aircraft on the first day of the war, and P.11 fighters are credited with about 110 victories throughout the campaign, with approximately 100 aircraft lost.
Has any original PZL P.11c been preserved?
Yes, one in the world - serial number 8.63, assembled on November 29, 1935, from the 121st Fighter Squadron, flown by 2nd Lt. Wacław Król on September 1, 1939, from Balice. Captured by the Germans, it survived the war in the Berlin aviation collection and in hiding near Czarnków, and since 1963 it has been housed in the Polish Aviation Museum in Krakow; the airframe was restored at PZL Okęcie between 1986–1989. In addition, there is a replica in Dęblin, and the Polish Historic Aircraft Foundation is building a flyable replica.
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