The PZL.23 Karaś (crucian carp) was a Polish light bomber and reconnaissance aircraft designed in the mid-1930s by PZL in Warsaw.

During the interwar period, the Polish High Command had placed considerable emphasis upon the role of armed aerial reconnaissance aircraft.

By the end of 1939, around 120 PZL.23s (86 per cent of the Polish Air Force's inventory of the type) were destroyed; however, of these, only 67 had been lost as a direct result of enemy actions.

B. Cynk, the role was recognised by the Polish High Command as being, aside from the basic fighter aircraft, the most important type of aerial unit in their doctrine.

As such, considerable resources and effort was placed upon the creation of sizable army cooperation escadrilles, which were initially principally equipped with foreign-built biplanes such as the French Breguet 19 and Potez 25.

[1] An advanced low-wing cantilever monoplane design proposal with an all-metal structure and a Pratt & Whitney Wasp radial engine was selected for further development, however during early 1931, the Ministry of Transport cancelled the project and terminated its sponsorship amid a lack of interest.

[1] Following a series of consultations between the company and the Aviation Department, it was decided to embark upon the design of a three-man armed reconnaissance-bomber, using the abortive PZL.13 passenger transport airliner as a starting point for the new aircraft.

[1] An early key design decision was the selection of the British Bristol Pegasus radial engine to power the type, which was domestically produced by Skoda in their Warsaw plant.

[1] The diverse requirements of the PZL.23 imposed considerable hurdles in the design phase; in order to produce a relatively fast aircraft, a heavy airframe was practically necessitated, however, it was also important for the type to be able to operate from constrained austere airstrips rapidly established on the front lines of warzones; producing a suitable compromise was not easy.

[2] Static testing by the Institute of Aviation Technical Research (ITBL) was both protracted and determined some components to process insufficient strength; these were not completed until 1933.

[3] The fuselage bomb bay of the earlier prototype was eliminated; instead, the entire payload was carried externally on racks fixed onto the underside of the wing's center-section.

[5] During mid-1935, the second prototype was lost in a crash shortly after a take-off conducted at the maximum loading weight, killing the crew on board.

[5] As a consequence of its favourable flight test programme, the aircraft was approved to enter full-scale production during the second half of 1935.

[6] However, since this engine proved to be unreliable during testing, the final variant, which was designated PZL.23B, was fitted with the newer Pegasus VIII model, which was capable of generating a maximum of 720 hp (537 kW) of thrust.

The pilot was positioned within a fully enclosed air-conditioned and heated cockpit, while the observer was seated directly behind him and could descend into the ventral gondola during applicable parts of a given mission.

[9] The fixed undercarriage comprised a pair of cantilever struts and single tail skid, all of which were outfitted with pneumatic shock absorbers built by Czechoslovakian company Avia.

[6] Early Polish-built engines had encountered several common issues, including crankshaft fractures and reduction gears jamming; the original engine manufacturer, Bristol, had not amended the drawings and specifications provided to Poland to incorporate their latest improvements to the Pegasus, which addressed these issues.

[2] The fuselage of the PZL.23 had an oval-section structure, composed of a mixture of duralumin frames and stringers, which were strengthened via several struts on the middle section.

[9] A cantilever structure composed of ribs and spars was used for the tail unit; the fin and tailplane were covered by duralumin sheeting, while the rudder and elevators had finely corrugated exterior surfaces.

While plans to incorporate the Swiatecki bomb-release gear had been mooted, however, they were eliminated from the design during the prototype stage due to disagreements between the Aviation Department and the inventor regarding the manufacturing arrangements.

[13] The main deficiency of the PZL.23 was its relatively low speed compared to newer aircraft that were then entering service with neighbouring nations.

Due to the plane's low speed, light armour and, perhaps most importantly, a lack of supporting protection from friendly fighter aircraft, the PZL.23 suffered heavy combat losses.

Despite the lack of protective armour, Polish aircrews often conducted attacks upon German columns while flying at low altitudes, which made their aircraft particularly vulnerable to anti-aircraft fire.