What happened
Following a preflight inspection and refueling, the pilot departed the airport to perform banner-towing operations. During the cruise phase of flight, the aircraft began to lose altitude. The pilot attempted to recover the lost altitude by applying full power, but the descent continued for a period of time. The aircraft eventually stabilized and returned to normal flight. Because the pilot was accustomed to encountering downdrafts in the area, this initial event did not cause immediate alarm.
Later in the flight, the aircraft experienced a second period of altitude loss. In an attempt to maintain flight, the pilot applied full power, adjusted engine controls, and experimented with various combinations of airspeed and angle of attack. These actions had little effect on the descent rate. To avoid a potential impact with the large number of people present on the beach, the pilot elected to ditch the aircraft in the Atlantic Ocean.
The investigation
The aircraft subsequently sank in the ocean and was not recovered.