'Rogue' wind, not pilot, caused Little Rock police helicopter crash, investigation finds

Retired officer William (Bill) Denio was seriously injured after a straight line wind caused a helicopter undergoing a test run to tip off of the staging area where it was sitting. (Photo Courtesy: Little Rock Police Department)

A crash that destroyed one of the Little Rock Police Department's two observation helicopters in August was caused by a "rogue" wind and not the pilot, a police investigation found.

As one witness told investigators, the crash at a training center on Aug. 16 was caused by a "perfect storm" of conditions, according to records released under the Arkansas Freedom of Information Act. The helicopter was idling on a flatbed trailer, blades spinning, when it was hit by a "rogue burst of strong wind" and began to hover. Pilot and retired officer William "Bill" Denio tried to regain control of the aircraft but it collided with the trailer, rolled to the right and crashed into the ground.

The crash knocked Denio unconscious, according to the police files. He suffered a separated sternum, broken ribs and head trauma. Denio's legs were pinned under a section of the aircraft, so officers cut away pieces of the helicopter to get him out.

Denio was reportedly unable to recall what happened in the weeks after the crash.

A mechanic and an officer who witnessed the crash told investigators there was a strong gust of wind before the helicopter began hovering. Officer Matthew Smith said a heavy beating sound came from the helicopter blades as the aircraft started "getting lift." Smith said the helicopter shifted forward and Denio turned down the throttle very quickly, as if he was trying to shut if off, but the aircraft kept hovering. It then hit the trailer and crashed.

Smith, who has military aircraft experience, told investigators he didn't believe Denio, the trailer or a mechanical error caused the crash, according to a transcription of the interview. He said it "was just the sheer force of the wind and low RPMs of the aircraft created a perfect storm to where it just -- it just moved and it was the beyond the pilot's control ... ."

Smith told police a new battery had been installed in the helicopter that day and had been operating normally. He and a mechanic, Nicholas Franke, had been letting the helicopter run at idle speed and monitoring its gauges and fluids. Franke had reportedly been inspecting and replacing bolts on the helicopter's flight control system. They both said weather conditions were calm before the wind gust. Northeast winds of 9 mph were recorded before the crash happened at 10:20 a.m.

Franke told investigators he was inside a hangar when he heard something that sounded like the helicopter was running "higher than idle," according to the police files. He said the wind was "a little gusty" when he went to check on the aircraft. He saw "the blade was tilt a little further than it should've been." The helicopter then lifted off and crashed.

When investigators asked Franke for his opinion about what caused the crash, he said he didn't want to speculate.

Federal Aviation Administration officials went to the crash scene but decided not to investigate because there was "no intention of flight," a letter from the administration says.

Little Rock police Sgt. Roger Snook, who supervises the department's aviation unit, wrote in a memo that he did not find "any clear evidence that indicates the crash is a result of pilot error." He called Denio a "very cautious" pilot with 46 years of aviation experience. An insurance form filed in March 2018 says Denio had logged 8,000 hours as a pilot without an accident.

Little Rock police acquired the helicopter, a 2001 Bell 206B TH-67, in 2015 through a federal military surplus program. Police mostly used the helicopter, known as Jet Ranger, to keep an eye on the city's largest events, including the Arkansas State Fair, Riverfest and the Little Rock Marathon.

Police spokesman Lt. Michael Ford said Wednesday that the department had no plans to acquire a replacement helicopter.

Ford said he was not able to immediately answer questions about aviation unit operations since the crash.

Follow Scott Carroll on Twitter.

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