December 24, 2011
The drone had been in the air for close to five hours before its mission crew realized that something was wrong. The oil temperature in the plane’s turbocharger, they noticed, had risen into the “cautionary” range. An hour later, it was worse, and it just kept rising as the minutes wore on. While the crew desperately ran through its “engine overheat” checklist trying to figure out the problem, the engine oil temperature, too, began skyrocketing.
By now, they had a full-blown in-flight emergency on their hands. “We still have control of the engine, but engine failure is imminent,” the pilot announced over the radio.
Almost two hours after the first signs of distress, the engine indeed failed. Traveling at 712 feet per minute, the drone clipped a fence before crashing.