A report by the Transportation Safety Board says the unnamed man had a blood alcohol level of about .35 — more than four times the legal limit for driving a vehicle.
The board says the pilot made flight control errors that caused the helicopter's main rotor blade to contact the cabin and precipitate an in-flight breakup.
The chopper, owned by Gemini Helicopters of Grande Prairie, was monitoring well sites went it went down in a wooded area near Fox Creek on Jan. 27, 2013.
The board says the pilot also didn't file a flight plan that day and made an unauthorized trip with a passenger.
He had dropped his only passenger at an oil site, before flying off erratically, then crashed five minutes later.