From the fall of 1932, three prototypes were built, marked with symbols: PZL - 23 / I, PZL - 23 / II and PZL - 23 / III. Strength and static tests of the PZL - 23 / I were completed in the second half of 1933. The prototype took off at the end of 1934. In subsequent experimental versions, many improvements were made, such as: elimination of vibration of the rear part of the fuselage and height tail, strengthening of the airframe structure, improvement visibility from the pilot's seat by increasing the cabin glazing, lowering the engine mounting place by 10 cm, the use of a new ring with a lower Cx coefficient, the bomb chamber in the fuselage was removed, ejectors were moved under the wings and under the fuselage, and many others. In total, over 100 changes have been made and several hundred bugs have been fixed. The model version under the name PZL - 23 Karaś A was introduced into production (from mid-1935) in the number of 40 pieces in the new PZL WP-1 plant (Podlaskie Zakłady Lotnicze - Wytwórnia Płatowców No. 1) and successively entered the armament of the 1st Aviation Regiment and were exported to Bulgaria. During the operation of this aircraft, new defects appeared (including too weak engine, reaching a low altitude with full weapons, low efficiency of the gills, etc.). As a result of the elimination of these defects, the second version of the PZL - 23 Karaś B aircraft was created. It had a more powerful engine (Bristol Pegasus VIII with 680 HP, gills were removed, improved profiling of the transition between the fuselage and the wing was introduced). The contract with PZL was for the production of 210 aircraft in version B. In the fall of 1936, they began to be delivered to aviation regiments. In the second half of the 1930s, the PZL - 23 B Karaś aircraft became the basic line aircraft, while the A version of the Karasie was withdrawn for schooling. While serving in the Polish Military Aviation, Karas was used in several larger actions. In 1937, the Karasi B squadron from 1 PL carried out a demonstration sharp bombing of a small railway station on the Chełm - Brest n / B line. Several line squadrons were concentrated at the Vilnius - Porubanek airport as part of a demonstration of strength against neighboring Lithuania, while in October 1938 a dozen or so Karas from various regiments were stationed at the airport in Aleksandrów, securing the capture of Zaolzie. According to the rules, the use of Karasi was intended for the performance of intervention tasks. In the September campaign, they performed some combat tasks and aerial reconnaissance. Airplanes included in the army squadrons bombed armored columns, carried out long reconnaissance raids on the territories of Germany, Slovakia and East Prussia. The first facility to be bombed on the enemy's territory was a factory near Oława. Strategic objects in East Prussia were bombed. A large number of tasks performed resulted in approx. 90% losses in airplanes. In total, 112 Karasi were shot down in the September campaign, and only 11 machines were evacuated to Romania (three from the 31 squadron and eight from the 24 reconnaissance squadron). In addition, there were 30 Karasi in version A with CWL - 1 in Romania (they crossed the border on September 16, 1939). After Romania was included in the Pact of Three, the interned Karas was exchanged for German weapons and a reconnaissance and training squadron was formed. The Romanians used Karasi on the Eastern Front. The last Karas was used in Romania until 1946 as an air target tugboat. Technical data (version B): length: 9.68 m, wingspan: 13.95 m, height: 3.3 m, maximum speed: 319 km / h, climb speed: 6.7 m / s, practical ceiling: 7300 m, maximum range: 1260 km, armament: fixed - 2 Vickers F machine guns cal. 7.7 mm, 1 machine gun wz.33 cal. 7.92 mm, suspended - up to 700 kg of bombs.The PZL P.11a (the so-called eleven) is a Polish, single-engine fighter plane with a metal structure with Puławski wings, a classic tail and a fixed landing gear. The flight of the prototype took place in 1931, but serial production continued in 1937-1939. The first serial version is the PZL P.11a powered by the Bristol Mercury IV S2 engine with a power of 550 HP. However, it was treated as a transitional version and only 50 were ordered. The most famous version of the "eleven" - PZL P.11c - appeared in the summer. It had an improved fuselage, wings and a vertical stabilizer. It all improved the aerodynamics of the plane. The drive unit has not changed. The interest in the construction was expressed by, among others, Romania, where 95 units of the licensed PZL P.11 were manufactured at the IAR plants. At the outbreak of the war, all versions of the P.11 were much slower than their German opponents, but at the same time had greater maneuverability, high rate of climb and a less emergency engine than German planes. They had many victories over the enemy during the September campaign, mainly as part of the Pursuit Brigade. Technical data (version P.11c): length: 7.55m, wingspan: 10.72m, height: 2.85m, maximum speed: 367km / h, rate of climb: 14.5m / s, maximum ceiling: 8000m, range maximum: 550 km, armament: fixed - 2 machine guns wz.33 cal.7.92 mm.