Witnesses to two fatal Hawaii powered glider air crashes have said they heard a loud "pop" prior to the aircraft plunging into the ocean.
Federal officials investigating one of the crashes have linked the popping sound shortly before the crash to the pilot’s in-flight maneuvers that probably exceeded the structural limits of the aircraft and resulted in a structural failure of the wings.
Pilot Ted Hecklin, 38, who was carrying passenger Kathryn Moran on April 21, 2010, banked steeply away from a cliff at Kealakekua Bay and rolled upside down before his powered glider fell several hundred feet, according to the finding. Hecklin and Moran were both killed.
"Witnesses reported hearing a loud ‘pop’ and the wings folded around the fuselage (pod)," according to the National Transportation Safety Board finding released Tuesday.
"The pilot likely exceeded the manufacturer’s operating limitations for the aircraft, which specifies a maximum pitch limit of 45 degrees and a maximum bank angle of 60 degrees." The "probable cause" finding said the operating handbook warned that exceeding these flight limits put the aircraft out of the pilot’s control.
The Airborne WindSport Edge XT-912-L, made by an Australian-based firm, was assembled by a certified representative in Kona on Nov. 18, 2009.
Hecklin was certified as a sport pilot able to fly a weight-shift control aircraft on March 10, 2007, and was authorized as a flight instructor on Nov. 29, 2009, according to the documents obtained by the board.
Safety board spokesman Keith Holloway said investigators are looking into whether structural failure occurred in a separate crash that killed two people on Kauai on May 17.
"How much weight that issue has is yet to be determined," Holloway said Friday.
Holloway said federal officials were still investigating the cause of the crash on Kauai.
Witnesses to the Kauai crash said the powered glider banked and then they heard a pop like a rifle shot, then the aircraft went out of control and fell full speed into the ocean.
"He was really going fast," Robert "Captain Sundown" Butler has said in an interview.
Killed in the crash were pilot Steve Sprague, 48, and passenger Ray Foreman, 53, of Vista, Calif.
The aircraft was a Pegasus Quik 912S, manufactured by the United Kingdom-based P&M Aviation Ltd.
According to the P&M webpage, the Quik is a micro-light with a top speed of 100 mph and a cruise speed of more than 80 mph.
But the P&M website also warns that the maximum pitch limit is 45 degrees and maximum bank angle is 60 degrees, and to avoid aerobatic maneuvers.
Hawaii has had three fatal trike, or micro-light, crashes in less than a 13-month period, including a Feb. 15 crash in waters off Hanapepe on Kauai that killed pilot Jim Gaither and passenger Kim Buergel of Spokane, Wash.
That crash is still being investigated as well.
The aircraft involved in the three fatal crashes are commonly known as powered gliders, or air trikes. They look like hang gliders with a small fuselage under the wings and two open cockpit seats.
Under the Federal Aviation Administration classification of a weight-shift control aircraft, the pilot is allowed to fly the aircraft with a student pilot for instruction but not to operate commercial tours.
In at least a couple of the crashes in Hawaii, close friends who were with the victims have said they were never told about the flight restrictions and were doing it for sightseeing.
Friends said Moran, a Kona resident, was taking the flight to celebrate her 37th birthday.
The Federal Aviation Administration in September announced it would increase inspections of trike operations in Hawaii and monitor advertising on websites.
