The RMI-1 was a groundbreaking experimental aircraft developed in Hungary between 1940 and 1943. Designed by engineer László Varga, the aircraft was conceived as a three-seat fighter-bomber and heavy attack aircraft. It is historically significant for being the first Hungarian aircraft constructed entirely of metal and for its intended role as the world's first turboprop-powered aircraft, utilizing the Jendrassik Cs-1 engine—the first turboprop designed specifically for aviation use.
The aircraft was developed under the auspices of the Repülő Műszaki Intézet (RMI), a Hungarian technical institute rather than a commercial manufacturer. The design called for a low-wing, twin-engine configuration with a crew of three, consisting of a pilot, a navigator, and an observer/bombardier. Planned performance specifications were ambitious for the era, with a projected maximum speed of 540 km/h (approximately 340 mph), a service ceiling of 10,000 meters, and a range of 3,000 km. Its intended armament included four fixed forward-firing heavy machine guns in the wings, three rifle-caliber machine guns for rear defense, and an internal bomb bay capable of carrying up to 300 kg (660 lb) of bombs.
Technical challenges plagued the project, primarily due to the Jendrassik Cs-1 engines. While the design target was 1,000 hp (750 kW) per engine, bench tests revealed an actual output of only about 400 hp. Consequently, the Hungarian authorities cancelled the RMI-1 as an official operational program in 1942, opting instead to license-produce the German Daimler-Benz DB 605 piston engine and procure the Messerschmitt Me 210. Despite the cancellation, work on the prototype continued, and construction was completed by August 5, 1943. The aircraft underwent limited testing with the Cs-1 engines, achieving only a brief "hop" flight. In 1944, the sole prototype was re-engined with liquid-cooled V-12 Daimler-Benz DB 605 piston engines and conducted high-speed ground runs and taxiing trials.
The RMI-1 never entered series production, and only one airframe was completed. Its development ended abruptly in June 1944 when the prototype was destroyed by an Allied bombing raid before any full flight testing could be conducted. No examples of the aircraft survive today, but it remains a notable example of early propulsion innovation during World War II.