NTSB: Pilot error cause of fatal 2021 plane crash

Sep. 16—A Muskogee man who was piloting a plane that crashed and killed him and his three passengers was at fault in the crash, according to a report from the National Transportation Safety Board.

Tim Allison, of Allison Aviation in Muskogee, had been piloting a plane April 23, 2021, that belonged to Dr. Mark Andregg, a Tulsa orthodontist. Andregg, his wife Shannon and their son Nathan, all of Mounds, were killed in the crash.

According to the NTSB report, weather forecasts indicated the accident site was in an area where moderate icing conditions, embedded thunderstorms and hail were forecast.

"Review of preflight weather information received by the pilot indicated that he was aware of the conditions forecast on the route of flight before initiating the flight," the report states. "Freezing drizzle conditions were likely present along the flightpath."

The plane was equipped for flight in icing conditions, but the pilot's operating handbook contained a warning about ice build-up could exceed the capability of the ice protection system.

The plane, a single-engine Piper PA-46, crashed after leaving Muskogee-Davis Regional Airport. The plane was registered to Mark Andregg, who also was a licensed pilot.

The plane was on course for Williston, Florida, at 20,000 feet before a rapid descent and crash, with thunderstorms in the area. The FAA lost radar contact with the aircraft about 100 miles northwest of Little Rock about 5 p.m., when nearby residents reported hearing an aircraft in distress and the sound of a crash.

"It was a very dense part of the Ouachita National Forest, and the road had to be built to get into the wreckage," said Yell County, Arkansas, Sheriff Bill Gilkey, at the time of the crash.

Approximately 70 different search and rescue and law enforcement helped in the search.

Allison's pilot records were reviewed and those records "revealed multiple certificate application failures" for "inadequate knowledge of cross-country flight planning, aircraft performance, and stalls. Review of the pilot's airman knowledge written tests found areas answered incorrectly over multiple exams included meteorology, aircraft performance, aeronautical decision-making, and stalls."

Additionally, the plane, at the time of departure, would have been "361 pounds over maximum gross weight."

The NTSB determined the probable cause of the crash to be:

"The pilot's improper decision to continue flight in an area of moderate-to-heavy icing conditions, which resulted in exceedance of the airplane's anti-icing system capabilities, a degradation of aircraft performance, and subsequent aerodynamic stall."