The MBB Bo 105 HGH achieves 250mph/218kts
Tuesday, March 4, 1975
The MBB Bo105 Hochgeschwindigkeitshubschrauber High Speed Helicopter (HGH) was an experimental compound helicopter used to test high speed flight.
For more details of the aircraft and it's achievements see the reference below,
Source: AHS History Calendar, March 2013