In 1964, development work began at Bölkow upon the helicopter that would become the Bo 105, although work on the hingeless rotor it would use had begun earlier. On 16 February 1967, the second Bo 105A prototype conducted its maiden flight at Ottobrunn in Germany; the first public demonstration was held in May 1967. The test program was broken down into stages as the Bo 105 comprised a new airframe, new rotor system, and a new engine; thus the flying Bo 105 prototype was initially equipped with a main rotor from Westland Helicopter's Scout rotorcraft and a pair of Allison Model 250 turboshaft engines instead of their production counterparts. Sud Aviation worked with Bölkow on developing the rotorcraft; an Alouette II helicopter was modified with the Bo 105's rotor and used to test its performance envelope. The third Bo 105 prototype was equipped with the initial production standard MAN Turbo 6022 turboshaft engines; six pre-production Bo 105s were constructed for testing.