Incident Overview
The operator reported that a pilot landed a helicopter on an offshore platform and shut down the engine. After landing, the pilot secured the main rotor system by attaching a tiedown to the forward left main rotor blade and then securing that tiedown to the left front skid cross tube.
Several hours later, the pilot entered the right front seat to begin the engine start sequence. According to the operator, the pilot started the engine and, a few seconds after initiating the start, heard an "unusual noise" and felt the helicopter begin to shake. The pilot promptly shut down the helicopter without further incident.
Damage and Mechanical Condition
A postflight inspection revealed substantial damage to the blue main rotor blade. The operator reported that there were no pre-impact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.
Manual Procedures
The Bell Helicopter 407 Rotorcraft Flight Manual, in Section 2 Normal Procedures, lists preflight check areas. Regarding the exterior check, the manual states: "2-3-B-1. Fuselage – Cabin Right Side. 1. All main rotor blades – tiedowns removed, condition." The section also includes a warning: "Failure to remove rotor tiedowns before engine starting may result in severe damage and possible injury."