Experimental helicopter BŻ-1 SP-GIL

The first Polish helicopter: the BZ-1 SP-GIL was developed in the Technical Institute of Aviation in the 1950s. The history of trial and error and experience gained during the flight tests paved the way for other machines of this type.

The initiator of the construction of the experimental helicopter in 1947 was Eng. Zbigniew Brzoska, the then Head of the Endurance and Construction Department of the Technical Institute of Aviation. This idea was approved by the then director of the Institute Prof. Władysław Fiszdon. At the beginning of 1948 an engineering team was created, in which the main role was played by Eng. Bronisław Żurakowski, an ITL employee since 1947, who worked on the helicopter aerodynamics, its rotor and control system, Eng. Tadeusz Chyliński on hull design, and Eng. Zbigniew Brzoska on powertrain and endurance calculations. In mid-1949 a preliminary assembly of the helicopter was carried out, and workshop work was completed in the autumn of that year. They were led by the then head of the workshop, Eng. R. Berkowski.

The helicopter was marked with the letters SP-GIL (from the then present since 1948 until 1952 names Główny Instytut Lotnictwa (Central Institute of Aviation) was a one-seater two-bladed helicopter equipped with with an additional small two-bladed control rotor connected to the control system, and also stabilising the helicopter (Hiller system). The rotor blades had a wooden structure with a steel rod balancing the nose. The head of the helicopter was a vibration eliminator with a vangarde structure designed by Eng.  B. Żurakowski MA.

The tail rotor was two-bladed and wooden. The fuselage was lattice, covered with cloth with the beam tail made of plywood. The chassis was three-points. These were changed during testing (broadening, shock absorbing), as was the location of the exhaust pipe. The power unit was a German helicopter engine Hirth HM 504 with a power of 77 kW. It was designed for the transmission of the Zündapp motorcycle.

Testing of the helicopter began in early 1950, but before that a gust of wind had rolled the helicopter, which was damaged. After restoration, trials resumed in April 1950. The pilot was constructor Eng. Bronisław Żurakowski, who had never flown in a helicopter before. During its first flights, the helicopter received  a fair amount of damage. So it was repaired and improved. In autumn 1950 the blades were changed to more rigid, and the control vanes were expanded. During this time, Capt. pil. Wiktor Pełka joined the testing. He was a transport pilot, but performed experimental flights at the Institute. In Paris, with his own money, he made several training flights in a Hiller helicopter. This experience enabled the acceleration of test flights on the SP-GIL helicopter. He made 100 flights in it, and in 1951 demonstrated the helicopter before the civil and military authorities, and in front of an audience, during an air show at Okęcie airport, on 20 July 1952. That summer there was an accident capsizing the helicopter while landing and with subsequent damage. After the renovation, during training of the pilot Andrzej Abłamowicz, a gust of wind caused the tail boom to be cut off by the lifting rotor. Up to this point 169 flights had been made for a total time of 20 hours and 21 minutes. The helicopter was renovated after nearly three years (at the initiative of the experimental pilots R. Witkowski and A. Śmigiel) and another 185 flights totalling 12 hours and 30 minutes were made. These experiments were designed to facilitate the anticipated BZ-4 Żuk helicopter test flight. A failure in the transmission of the helicopter’s tail rotor finally excluded it from tests. Currently, after renovation, it is exhibited at the Aviation Museum in Kraków.

Text based on the book entitled “80 years of the Institute of Aviation” – Jerzy Grzegorzewski, Tadeusz Królikiewicz, Scientific Library of the Institute of Aviation, Warsaw 2006