|First flight||21 July 1959|
|Primary user||LOT Polish Airlines|
Design and development
The aircraft was development as a successor to the Lisunov Li-2 on short domestic routes for LOT Polish Airlines. The plane was designed by a design bureau led by Franciszek Misztal in the Aviation Institute (Instytut Lotnictwa). The first design work started in 1954 (under the designation FM-12) and the final design MD-12 appeared in 1956, after Leszek Dulęba had joined (the designation apparently came from Misztal-Dulęba). Initially it was to be powered with two Soviet 615 hp ASh-21 engines, but because their production stopped, a four-engine configuration was chosen, with Polish 315 hp WN-3 engines. In December 1957 the bureau was moved to the OKL centre (Ośrodek Konstrukcji Lotniczych - Aviation Designs' Centre), created in the WSK-Okęcie factory.
The first prototype flew first on 21 July 1959 (registration SP-PAL), the second prototype, designated MD-12P (SP-PBD), and fitted with complete passenger cab, on 7 January 1961. There was a third airframe built for static trials. The plane underwent state trials in 1961, and the second prototype was evaluated by LOT Airlines in August–September 1961.
The passenger variant was evaluated as quite successful, being easier to fly, than the Ilyushin Il-14 and more economical, but it was not produced because LOT found it unprofitable to order special planes for domestic routes. The small production that would result would increase costs. Instead, less modern airliners were switched from international to domestic routes.
It was next decided to build an aerial photography variant MD-12F. It was fitted with several cameras and other equipment, including a darkroom. The fuselage nose was glazed, with a navigator post. Span increased to 23.6 m by adding longer wingtips. The MD-12F flew first on 21 July 1962 (apparently dates of MD-12 prototypes' flights were adjusted to add splendour to communist Poland's national holiday, 22 July). It carried the registration SP-PBL. The aerial photography variant was successful and countries, like the USSR, Hungary, Romania and Pakistan were interested in it, but its development was ceased along with a crash of the first MD-12 prototype on 17 September 1963 near Grójec. The plane crashed due to flutter of tail control surfaces and a crew of 5 were killed.
The prototype MD-12P (SP-PBD) was evaluated by the LOT Polish Airlines in August–September 1961, on Warsaw-Rzeszów route, carrying over 1700 persons. It was also used in 1961 and 1962 on Warsaw-Poznań route, taking trips to Poznań International Fair.
The MD-12 was a four-engined low-wing cantilever monoplane of all-metal construction, duralumin-covered. The fuselage was a semi-monocoque. The crew cockpit in front with a crew of two pilots. Passenger cab with 20 seats in three rows. In the rear there was WC. Fuselage had doors in front part. In a fuselage nose there was a baggage space for 200 kg. Trapezoid three-part wing. Single tailfin. Engine nacelles in wings. Two-blade wooden propellers WR-1A of a variable pitch, diameter 2.2 m (powerplants were adapted from the TS-8 Bies trainer). Retractable tricycle landing gear - main gear with single wheels retractable to inner engine nacelles. Fuel tanks 1160 l in wings (cruise fuel consumption 240 l/h).
- Prototype. One built, registered as SP-PAL.
- Passenger version. One built, registered as SP-PBD.
- Aerial photography version with glazed nose and increased wing span. One built, registered as SP-PBL.
The MD-12F is preserved in the Polish Aviation Museum in Kraków, from 1967.
Data from Jane's All The World's Aircraft 1965–66
- Crew: 4–7
- Length: 15.80 m (51 ft 10 in)
- Wingspan: 21.20 m (76 ft 1½ in)
- Height: 5.95 m (19 ft 6 in)
- Wing area: 57 m² (613.5 sq ft)
- Airfoil: NACA 23015 at root, NACA 23009 at tip
- Aspect ratio: 9.45:1
- Empty weight: 5,025 kg (11,080 lb)
- Max. takeoff weight: 7,000 kg (15,432 lb)
- Powerplant: 4 × Narkiewicz WN-3 air-cooled 7-cylinder radial engine, 330 hp (246 kW) each
- Never exceed speed: 370 km/h (200 knots, 230 mph)
- Maximum speed: 305 km/h (165 knots, 190 mph)
- Cruise speed: 280 km/h (151 knots, 174 mph)
- Stall speed: 100 km/h (54 knots, 62 mph)
- Range: 2,100 km (1,130 nmi, 1,300 mi)
- Service ceiling: 5,200 m (17,060 ft)
- Rate of climb: 5.8 m/s (1,140 ft/min)
- Aircraft of comparable role, configuration and era
- Taylor 1965, p. 112.
- Janusz Babiejczuk, Jerzy Grzegorzewski Polski przemysł lotniczy 1945-1973 (Polish aviation industry...), Wydawnictwo MON, Warsaw 1974 (no ISBN)
- Taylor, John W. R. Jane's All The World's Aircraft 1965–66. London: Sampson Low, Marston & Company, 1965.
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