PWS-24

The PWS-24 was a Polish single-engine passenger aircraft for 4 passengers, built in PWS factory, used from 1933 to 1936 by LOT Polish Airlines. In spite of its limited capacity, it was the only series-built airliner of domestic design ever used by LOT

Development
The aircraft was a development of an unsuccessful PWS-21, utilizing its lightweight construction wing (weight 300 kg). A fuselage and stabilizers were new. The main designer was Stanisław Cywiński. The prototype (markings SP-AGR) first flew in August 1931 in Biała Podlaska. After trials and some modifications, it won a Ministry of Communication's contest for a successor of Junkers F-13 in LOT airlines, against Lublin R-XVI. In June 1932 it took the first place in a passenger aircraft race at the international air meeting in Warsaw.

Polish Ministry of Communication ordered a series of 5 aircraft for LOT airlines, built in 1933 (markings: SP-AJF, -AJG, -AJH, -AJJ, -AJK). In 1932, the prototype SP-AGR was fitted with a more powerful engine, the 300 hp Lorraine Algol, instead of the 240 hp Wright Whirlwind J-5. It was later tested with a 400 hp Pratt & Whitney Wasp Junior engine. Maximum speed improved from 185 to 225 km/h, comparing with the basic variant.

In 1934 a production of further 5 aircraft started, with Wasp Junior engines, designated PWS-24bis (markings: SP-AMN, -AMO, -AMP, -AMR, -AMS). Also one PWS-24 was converted to PWS-24bis (SP-ASY, ex. SP-AJH).

Usage
PWS-24 were put into use in LOT Polish Airlines from May 1, 1933 on domestic lines. Their flight characteristics and durability proved however worse, than of single-engined Fokker F.VIIa/1m, used by LOT, so their service was not long. In 1935 three PWS-24 (SP-AGR, -AJF, -AJJ) were converted to aerial photography variant, but in 1936 four PWS-24s were broken up. The last, SP-AJJ, was broken up in 1938.

PWS-24bis entered service in LOT in 1935. They were used there however only until 1936. PWS-24bis SP-AMR was next sold to the Polish Air Force and used as a staff machine, its further fate is not known. SP-ASY and -AMN were broken up in 1936-1937, SP-AMO was sold in 1936 to Naval and Colonial League paramilitary organization and soon crashed during propeller testing.

The remaining two PWS-24bis (SP-AMP and-AMS) were converted to aerial photography in 1936 and used by the outbreak of World War II in September 1939. After the German invasion, SP-AMP was damaged, while SP-AMS was evacuated to Romania, where it was taken over by the Romanian aviation and used by them to aerial photography.

Description
High-wing cantilever monoplane of mixed construction, with closed cab and single engine. A fuselage of a steel frame, covered with canvas on a wooden frame. Straight one-piece wooden wing, with elliptical endings, two-spar, plywood covered. Tailfins of steel frame, canvas covered. Crew of two (pilot and mechanic), in a cab before the wing, with twin controls. Next and below in a fuselage, under the wing, there was a cabin for 4 passengers, with wide rectangular windows and a door on the left side. Radial engine in fuselage front, fitted with a Townend ring. Two-blade metal propeller of variable pitch. Conventional fixed landing gear, with a rear skid; struts with shock absorbers joined the main gear with wings. Fuel tanks 260 l in central wing section (cruise consumption 50-58 l/h in PWS-24, 95 l/h in PWS-24bis).

Engine:
 * PWS-24 - 9-cylinder air-cooled radial engine Wright Whirlwind J-5 (240 hp take-off power, 220 hp nominal power)
 * PWS-24bis - 9-cylinder air-cooled radial engine Pratt and Whitney Wasp Junior TB (420 hp take-off power, 400 hp nominal power)