Accident Details
On October 7, 2011, at approximately 1430 central daylight time, a Eurocopter AS350 B2 helicopter sustained substantial damage during an engine start on the South Pass 93A offshore oil platform in the Gulf of Mexico. The commercial pilot and two passengers were not injured. The helicopter was registered to and operated by ERA Helicopters under 14 Code of Federal Regulations Part 135 as an on-demand air taxi. Visual meteorological conditions prevailed, and the flight was operating on a company visual flight rules flight plan at the time of the accident.
Pilot Statement
According to the pilot, the helicopter's nose faced into the wind, measured by a velometer at about 23 knots. The pilot centered and locked the controls before engine start as per the helicopter's checklist. At approximately 22 Ng and three full main rotor rotations, the pilot felt chatter and vibrations. The engine was shut down, and inspection revealed damage consistent with a main rotor blade striking the tail boom. The tail rotor drive shaft was distorted and damaged.
Environmental Conditions
The helipad was elevated above the main platform, with a generator room located to the west (downwind). The pilot reported that when the wind came from the east, it contacted the generator room and occasionally caused updrafts on the helideck.
Flight Manual Procedures
The helicopter's flight manual, in the "Checks Before Starting the Engine" checklist, specifies that the cyclic should be in the neutral position with the cyclic stick friction lock adjusted. Note 1 of the "Starting" checklist states: "In strong wind, apply a little forward cyclic and accelerate the engine, up to approx. 320 rpm, as fast as is compatible with t4 limitations, then follow normal procedure."
Post-Accident Examination
An examination of the helicopter found no preexisting anomalies that would have prevented normal operation. It could not be determined whether the controls had been locked improperly or if wind displaced the main rotor blades during the engine start.
BEA Review
A review of accidents involving AS350 helicopters by the Bureau d'Enquêtes et d'Analyses (BEA) revealed that in all recorded tail boom strikes by main rotor blades during start, two conditions were present: cyclic not centered and air turbulence pushing strongly on the main rotor blades.