By Jeff Pardo

In April 27, 2000, a Canadian commercial helicopter pilot who was also a chief helicopter flight instructor took off on a test flight with a maintenance engineer in a Bell 206 JetRanger from an airport in Quebec. Five minutes later, they disappeared from radar. The Transportation Safety Board of Canada determined rather quickly that the main rotor hub and rotor blades had departed the aircraft in flight. What makes this accident worth discussing is that both individuals knew that the mast nut, which retains the rotor head in place atop the mast, had been removed two days earlier. In addition, two other individuals who actually took part in the removal…