The airplane was not equipped with a flight data recorder, and so investigators reconstructed the accident sequence from the cockpit voice recorder. Thirty-seven minutes after takeoff, the pilot requested and received clearance to climb to FL 230 to get out of the clouds. He started the climb on autopilot, evidently using the vertical speed, or V/S, mode. Significantly, he did not use the flight level change, or FLCH, mode. In FLCH mode, the autopilot holds airspeed; the rate of climb to a target altitude depends on the power setting. In V/S mode, the pilot selects a climb rate and the autopilot adjusts speed — that is, angle of attack — to maintain it. According to the Air Force accident report, V/S is habitually used by “half the pilots” — presumably meaning MC-12W pilots — for altitude changes even though there is a slight risk that with insufficient power the autopilot will maintain the climb rate by raising the nose until the wing stalls.