A small plane that crashed in Wisconsin, killing six people, including a child, had plummeted toward the ground at a rate of up to 4,000 feet per minute after its pilot reported ice accumulating on the wings, according to newly released flight data and federal investigators.
The National Transportation Safety Board (NTSB) said the pilot of the Piper PA-46 Malibu was flying at 24,000 feet on Tuesday night when he alerted air traffic control to ice building up on the aircraft’s wings and requested permission to descend.
Air traffic controllers approved the request, but the plane entered a descending right turn that became increasingly sharp before communications and flight tracking data were lost, investigators said.
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Data from FlightRadar24 showed the plane’s airspeed nearly doubled to 340 mph as it descended at a rate of up to 4,000 feet per minute, according to The Associated Press.
“It has all the earmarks of an icing-related loss of control,” aviation safety expert Jeff Guzzetti, a former investigator for both the NTSB and Federal Aviation Administration (FAA), told the outlet.
Ice accumulation poses a serious threat to aircraft because even a thin layer can disrupt airflow over the wings, reducing lift and making a plane more difficult to control.
The six-seat, single-engine aircraft was traveling from Kenosha to Menomonie when it crashed shortly before 10 p.m. in a wooded area of Sauk County near Mirror Lake State Park, about 10 miles west of Wisconsin Dells, authorities said.
Rain was falling as a thunderstorm moved through Dellona at the time of the crash.
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All six people aboard were killed. Authorities said no structures were damaged and no one on the ground was injured. The identities of the victims had not been publicly released.
The Piper Malibu model has previously faced federal scrutiny over crashes involving icing conditions.
The NTSB conducted a special safety review of seven icing-related crashes involving Piper Malibu and Mirage aircraft between 1989 and 1991, several of which involved relatively inexperienced pilots unfamiliar with handling the sophisticated planes in icy conditions.
The review prompted recommendations for changes to pilot training, aircraft checklists and operating manuals, as well as the addition of an indicator light for systems designed to prevent ice buildup in pitot tubes, which help provide accurate airspeed readings.
The NTSB is leading the investigation into Tuesday’s crash. Investigators have not determined an official cause.
The Associated Press contributed to this report.