Flight History
On December 1, 2008, a Bell 412 helicopter registered as JA6713, operated by the Japan Coast Guard's 11th Regional Coast Guard Headquarters Ishigaki Air Station, departed Ishigaki Airport at approximately 18:11 JST for a night patrol and picture-shooting training flight. The flight plan was filed under Visual Flight Rules (VFR) with an estimated off-block time of 18:00, cruising speed 110 knots, and a total endurance of 3 hours 30 minutes. Five crew members were on board: the captain (pilot flying, right seat) and the copilot (pilot not flying, left seat), along with three other crew members.
Sequence of Events
The flight proceeded smoothly to the Miyako Island area. The crew conducted hovering and picture-shooting training near the uninhabited island Fude-Iwa using the autopilot's SAR mode. After completing that exercise, the crew identified a patrol boat (the Boat) and coordinated with it to conduct picture-shooting training near the Boat. The captain attempted an approach to the back-left of the Boat using autopilot, but the Boat changed course, prompting the captain to abort and request the Boat maintain a northerly heading. A second approach was initiated around 19:38. During the final turn at 200 feet and 60 knots, the captain judged that there was insufficient distance to shift to hovering behind the Boat using autopilot alone.
The captain then applied manual control by pulling the nose up and lowering the collective lever while pushing the Force Trim Release (FTR) button. He instructed the copilot to engage VELOCITY HOLD (VELHLD) to maintain reduced airspeed. The copilot confirmed VELHLD on, but the captain later noted the copilot appeared to look down for a relatively long time. The captain sensed something unusual during deceleration, lowered the nose, and raised the collective lever to initiate a breakout maneuver. He observed downwash from the main rotor and intuitively felt the altitude had dropped to about 30 feet with reduced airspeed. While attempting to recover the aircraft's attitude, the helicopter entered the downwash splashes and ditched. The captain described a very short interval between noticing the low altitude and the impact.
After ditching, the captain inflated the emergency floats. The engines continued running, and there was no fire warning. Upon hearing a "fire" call from a mechanic, the captain pulled the fire-extinguishing handles, stopping the engines. The helicopter tilted slightly left initially, then later to the right. The crew deployed a lifeboat from the right cabin door, and all crew members evacuated. The Boat arrived, and the crew were rescued.
Statements
During the investigation, the captain stated that he may have momentarily pressed the standby button on the cyclic stick instead of the FTR button, which would cancel all autopilot modes including RADALT. The copilot later reported that RADALT was off when he turned VELHLD on. The captain noted that he had rarely mistaken the standby button for the FTR button during previous operations.
Damage
The aircraft was destroyed, but no fire occurred. The center float on the right skid ruptured after ditching, followed by the right front float.
Investigation
The Japan Transport Safety Board investigated the accident, with an accredited representative from Canada (State of Manufacture) participating. The United States (State of Design) did not designate a representative.