What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) Helicopter doing low level aerial mapping of unexploded ordinance on government contract. Task is to fly a precise centerline over mapping area at an average clearance height of six feet, with course reversal and adjacent mapping lane flown in opposite direction. A boom is installed on front of craft to detect ordinance. Boom extends out forward and horizontally from nose. While craft was on easterly course over map area (lake eire ft. perry area) at 25 knots over calm lake surface, a course correction to left was initiated with 2 degrees bank angle. This resulted in the boom lip touching the surface of the water, the nose pitching down causing the main rotor blades to strike the water. The helicopter became inverted, sinking within approximately 3 seconds. Pilot and equipment/camera operator were able to exit with minor injuries and swim to shore (.75 miles away). Aircraft had been fueled with 60 gallons, approx. 40 gallons of fuel was on board at time of accident. Helo within 150 pounds of gross weight with CG at 99.17 in. From datum, within limits. This operation, low level, is normally conducted over desert, in such conditions if the boom tip hits the ground it simply flexes. That did not occur with water.
As the FAA filed it
(-23) HELICOPTER DOING LOW LEVEL AERIAL MAPPING OF UNEXPLODED ORDINANCE ON GOVERNMENT CONTRACT. TASK IS TO FLY A PRECISE CENTERLINE OVER MAPPING AREA AT AN AVERAGE CLEARANCE HEIGHT OF SIX FEET, WITH COURSE REVERSAL AND ADJACENT MAPPING LANE FLOWN IN OPPOSITE DIRECTION. A BOOM IS INSTALLED ON FRONT OF CRAFT TO DETECT ORDINANCE. BOOM EXTENDS OUT FORWARD AND HORIZONTALLY FROM NOSE. WHILE CRAFT WAS ON EASTERLY COURSE OVER MAP AREA (LAKE EIRE FT. PERRY AREA) AT 25 KNOTS OVER CALM LAKE SURFACE, A COURSE CORRECTION TO LEFT WAS INITIATED WITH 2 DEGREES BANK ANGLE. THIS RESULTED IN THE BOOM LIP TOUCHING THE SURFACE OF THE WATER, THE NOSE PITCHING DOWN CAUSING THE MAIN ROTOR BLADES TO STRIKE THE WATER. THE HELICOPTER BECAME INVERTED, SINKING WITHIN APPROXIMATELY 3 SECONDS. PILOT AND EQUIPMENT/CAMERA OPERATOR WERE ABLE TO EXIT WITH MINOR INJURIES AND SWIM TO SHORE (.75 MILES AWAY). AIRCRAFT HAD BEEN FUELED WITH 60 GALLONS, APPROX. 40 GALLONS OF FUEL WAS ON BOARD AT TIME OF ACCIDENT. HELO WITHIN 150 POUNDS OF GROSS WEIGHT WITH CG AT 99.17 IN. FROM DATUM, WITHIN LIMITS. THIS OPERATION, LOW LEVEL, IS NORMALLY CONDUCTED OVER DESERT, IN SUCH CONDITIONS IF THE BOOM TIP HITS THE GROUND IT SIMPLY FLEXES. THAT DID NOT OCCUR WITH WATER.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.