By Dan Lamoth

It was a routine evening in Afghanistan when Marines and contractors with Lockheed Martin launched an unmanned K-Max drone helicopter from a major base in Helmand province to carry food rations to a smaller outpost. The aircraft had made hundreds of similar trips for the Marines since first being deployed in 2011, and it looked like this would be like any other.

Something went seriously wrong the evening of June 5, 2013, though. As the helicopter closed in on its destination, the Marine lieutenant commanding the mission and Lockheed contractors operating the aircraft remotely expected 15 mph headwinds. Instead, it got a tailwind, shaking up the drone.

The pilots employed a technique known as the “weathervane” effect in an attempt to gain control, allowing the pilots to turn the aircraft into the wind and gain control. But it didn’t work. The oscillation of the 2,000-pound load swinging beneath the helicopter in a cargo net grew increasingly worse, bringing the 52-foot-long helicopter, valued at $11.1 million, down in a heap on the landing zone. No one was injured, but the laptop computer collecting information about the flight was ejected out the left cockpit window, and the tail burst into flames.

The crash report, released to The Washington Post through the Freedom of Information Act, illustrates the dangers that can occur when a drone operator does not realize the peril their aircraft is in.

Military investigators found that the mishap was preventable and occurred because the pilots did not intervene quickly enough when the helicopter experienced unexpected wind, according to documents released by the Marine Corps. Accident investigators also determined that U.S. personnel on the ground near the landing zone should have provided an updated weather report, and also sent a warning back to the pilots at Camp Bastion to let them know it was out of control.

http://www.washingtonpost.com/news/checkpoint/wp/2014/08/07/exclusive-why-pilots-couldnt-stop-a-marine-corps-drone-helicopter-from-crashing/