Aircraft: Thorp T-18. Injuries: 1 Fatal. Location: Pahokee, Fla. Aircraft damage: Destroyed.
What reportedly happened: Family members notified authorities when the airplane was overdue. The wreckage was found in pieces along the route of flight the next day.
It was determined that the pilot was operating under visual flight rules while receiving radar traffic advisory service from an air traffic controller. The controller noticed a potential conflict with a Boeing 757 and acted to maintain traffic separation by instructing the 757 pilot to maintain 8,000 feet, asking the Thorp pilot to maintain at or below 7,500 feet, and provided an advisory for wake turbulence.
The Thorp was at 7,800 feet at the time, and the pilot advised that he was descending to comply with the controller’s instructions. When the two aircraft were separated horizontally by about one to two miles, the Thorp pilot reported the 757 in sight.
Radar data indicated that it passed directly beneath the 757, within 500 feet of vertical separation, traveling in roughly the opposite direction.
Investigators determined that although the geometry and the timing of the airplanes passing each other suggest the possibility of a wake turbulence encounter, the Thorp pilot made no comment about encountering turbulence.
Although radar data showed the Thorp turning left as if to get out from under the 757’s flight track, it then turned back to the right and continued climbing on a northwesterly heading for about 2-1/2 minutes until reaching 8,300 feet.
The airplane then turned right and descended to 7,200 feet before it was lost from radar. During the descent, the wings separated from the airplane due to overstress.
The reason for the descent and in-flight overstress of the airplane could not be determined.
The two aircraft were operating in class E airspace, and FAA directives do not require 1,000-feet separation for aircraft in this airspace.
Probable cause: The descent and over-stress of the airplane during the descent, which resulted in the in-flight breakup of the airplane.
NTSB Identification: ERA13FA071
This December 2012 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.