Amateur-built THORP T-18 N118GG accident near Pahokee, Florida

Probable cause

The descent and overstress of the airplane during the descent, which resulted in the in-flight breakup of the airplane.

NTSB analysis

Family members reported the airplane overdue for arrival, so an alert notice was issued. The local authorities located the airplane the following day. Air traffic control records indicate that, during the accident flight, the pilot was operating under visual flight rules while receiving radar traffic advisory service from an air traffic controller. The air traffic 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 accident pilot to maintain at or below 7,500 feet, and providing a wake turbulence cautionary advisory. The accident airplane 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 1 to 2 miles, the accident pilot reported the 757 in sight. Radar data indicated that the accident airplane passed directly beneath the Boeing 757, within 500 feet of vertical separation, traveling in roughly the opposite direction. Although the geometry and the timing of the airplane's passing each other suggest the possibility of a wake turbulence encounter, the accident pilot made no comment about encountering turbulence. Although radar data showed the accident airplane 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 in a positive direction. 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 Federal Aviation Administration directives do not require 1,000-feet separation for aircraft in this airspace.

Text from the NTSB. Open the NTSB docket for ERA13FA071 for the full record.