Just after dawn on May 22, Facebook reached another exciting and important milestone for the Aquila program — completing the successful second full-scale test flight of the aircraft. The aircraft flew for 1 hour and 46 minutes, and landed perfectly on our prepared landing site. In order to launch right after sunrise, which was at 5:15 am, we showed up at the gate to Yuma Proving Ground in Arizona at 12:30 am. While some members of the team began to open the hangar and lift the airplane onto its takeoff dolly, the rest of us prepared the ground control station and engineering station. And pretty much everybody studied the wind forecast. Aquila’s second test flight took into account the lessons we learned from our first flight. In advance of the second flight, we incorporated a number of modifications to Aquila, including: Adding “spoilers” to the wings, which help to increase drag and reduce lift during the landing approach; Incorporating hundreds of sensors to gather new data; Modifying the autopilot software; Integrating new radios for the communication subsystem; Applying a smoother finish on the plane; Installing a horizontal propeller stopping mechanism to support a successful landing. At 5:27 am, the sun was just above the horizon, and the aircraft had passed all our preflight checks. The radio links (redundant uplinks and downlinks are installed both for extra bandwidth and for redundancy) were functional, the control surfaces and spoilers were free and correct, and all four motors responded to commands properly. After completing our pre-takeoff checklist, our brief wait was rewarded with low measured winds as well as low forecast winds. A quick poll of the pilots and engineers resulted in a “go for launch” call. The launch speed was calculated at 27 mph and this was passed to the operators of the tow vehicle. The crew closely watched the displays, awaiting the signals that the autopilot had commanded release and that the airplane was climbing away from the dolly. Takeoff was normal. It also quickly became apparent that all the systems were functioning normally: The motor current, the airspeed tracking, the heading tracking, the radio links, and the differential GPS all showed nominal behavior. The only surprise was a happy one: The climb rate – at 180 ft/min - was nearly twice as fast as on our first flight. We attribute this to the numerous refinements to Aquila — especially a smoother finish — that were based on learnings from our first flight.”

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