I.L. BZ-1 Gil 'SP-GIL'
On display in the main display hangar at the Muzeum Lotnictwa Polskiego
The following info is taken from the museum website:-
"The idea of designing and building helicopters in Poland was born in 1946. Its author was Zbigniew Brzoska ph.D. However, on the way to the realisation of such a daring enterprise there stood the lack of appropriate scientific studies. The only source of knowledge was the aviation press concerned with technical novelties. First, the gathering of any information concerning this subject was undertaken. In 1947, a three man team was appointed. It included Zbigniew Brzoska, responsible for the helicopter's engine, Bronisław Żurakowski, responsible for the main rotor and Tadeusz Chyliński, responsible for the design of fuselage, tail boom, tail rotor and undercarriage.
In 1949, the design studies were completed and the construction of the prototype of an experimental machine started. The assembly ended in summer the same year. The machine received the SP-GIL, civil registration. No official name was appointed. The helicopter was designed in a "classic" configuration (a single main rotor plus a tail rotor). The main rotor, based on the American Hiller system, had two wooden main blades and two smaller steering blades. Such a configuration ensured self-stability and decreased the control force, which significantly made steering easier.
A fabric covered fuselage had removable aluminium engine doors. The airframe was made in a form of truss, welded with steel tubes. The cockpit was made for two persons, but practically, it was flown single handed. The nose wheel undercarriage had oleo-pneumatic shock absorbers. For propulsion, a very good German Hirth HM 504 inline engine was chosen. The intermediate tail rotor gearbox, taken from the German Zundapp motorbike, was used.
In April, 1950, in-flight tests started. The helicopter test pilot was one of the designers – Bronisław Żurakowski. It is worth mentioning, that he had no prior experience of flying a helicopter, not to mention doing so as a pilot. Several different engines failing made the tests difficult. Another serious problem was the vibrations, that were a serious mishap in helicopter development throughout the world.
In 1951, as a result of several repairs, designers managed to decrease vibrations by applying a special resonance absorber to the main rotor. The designer was Zbigniew Brzoska and the builder was Bronisław Żurakowski. However, after the helicopter's breakdown in 1953, tests were suspended. The machine was repaired but received no flight certificate. In autumn 1956, the helicopter was restored, a few changes and reinforcements being introduced. In February 1957, after another damage, flights were stopped and the helicopter was scrapped.
From the perspective of time, the helicopter's construction was very simple, if not primitive. It is worth noting, however, that it was just an experimental aircraft, intended to collect experience in the then still relatively unknown domain of rotorcraft. In addition, it appeared as a result of a low-budget enterprise, in a war-tormented country, where it was hard to find finance and resources for such experiments. As a pioneering construction, it did excellently. One can only regret, that it did not open the way to domestic helicopter construction. Helicopter production in Poland soon started on a grand scale, albeit on Soviet licence. It was an unfortunate turn of events for Polish aircraft industry, as it started to develop this subject virtually at the same time as the most famous designers and manufacturers in the world, who faced the same technical problems and breakdowns.
The SP-GIL helicopter never received an official name. In a few publications, the name BŻ-1 GIL (bullfinch) is used, but it is just a literary convention of sorts used as the type's designation."