Accident Summary
The aircraft was engaged in a beachside banner towing operation when it encountered a strong downdraft from a thunderstorm and subsequently impacted the water. The pilot reported observing thunderstorms developing inland approximately half an hour prior to the accident. According to the pilot, the aircraft was 'overtaken' by the storms before he could return to his base.
Pilot Actions
Upon encountering the downdraft, the pilot added full power and released the banner in an attempt to mitigate the situation. However, he was unable to arrest the high sink rate that developed, leading to the water impact.
Thunderstorm Avoidance Awareness
The pilot was asked whether he was familiar with the thunderstorm avoidance procedures recommended in the Airman's Information Manual. He acknowledged awareness of these procedures but stated that he could not shut down banner towing operations simply because a thunderstorm was within 10 miles of his operations area.