Investigators have blamed a sudden downdraft for causing a helicopter to crash on Pikes Peak while filming an experimental car on the mountain in September.

The Aerospatiale AS 355F1 helicopter came crashing down the morning of Sept. 17 as it filmed the Autonomous Audi TTS Pikes Peak, a driverless car, as it made a sharp turn on the Pikes Peak Highway. 

To film the maneuver, the pilot tried to fly away from the mountain before gently banking 180 degrees to put the car into focus, according to a report by the National Transportation Safety Board.

When it turned back to the mountain, however, the downdraft forced the helicopter into the mountain. The pilot could not “power out” of the wind, the report said, because of the high altitude.

Instead of risking a turn down the mountain slope, the pilot landed the helicopter near the road, where it rolled onto its left side. He suffered minor injuries in the crash while his three passengers were unharmed, the report said.

The helicopter was a twin-engine, five-passenger 1982 Aerospatiale owned by JBD Enterprises in Eugene, Ore.

The Audi crew has been in the area since Sept. 6, checking conditions of the Pikes Peak Highway and adjusting the GPS mechanism inside the car. It was the first day the film crew had used a helicopter.