a risk factor for VRS in helicopters. Subsequent testing showed that the V-22 and other tiltrotors are generally less susceptible to VRS than helicopters; VRS entry is more easily recognized, recovery is more intuitive for the pilot, altitude loss is significantly less, and, with sufficient altitude ( or more), VRS recovery is relatively easy. The V-22 has a safe descent envelope as large as or larger than most helicopters, further enhancing its ability to enter and depart hostile landing zones quickly and safely. The project team also dealt with the problem by adding a simultaneous warning light and voice that says "Sink Rate" when the V-22 approaches half of the VRS-vulnerable descent rate. December 2000 On 11 December 2000, a V-22 had a flight control error and crashed near Jacksonville, North Carolina, killing all four aboard. A vibration-induced chafing from an adjacent wiring bundle caused a leak in the hydraulic line, which fed the primary side of the swashplate actuators to the right side rotor blade controls. The leak caused a Primary Flight Control System (PFCS) alert. A previously-undiscovered error in the aircraft's control software caused it to decelerate in response to each of the pilot's eight attempts to reset the software as a result of the PFCS alert. The uncontrollable aircraft fell and crashed in a forest. The wiring harnesses and hydraulic line routing in the nacelles were subsequently modified. This caused the Marine Corps to ground its fleet of eight V-22s, the second grounding in 2000. March 2006 A MV-22B experienced an uncommanded engine acceleration while turning on the ground at Marine Corps Air Station New River, NC. Since the aircraft regulates power turbine speed with blade pitch, the reaction caused the aircraft to go airborne with the Torque Control Lever (TCL, or throttle) at idle. The aircraft rose into the air (initial estimates suggested 20 to 30 feet) and then fell to the ground, causing damage to its starboard wing; the damage was valued at approximately US$7 million. It was later found that a miswired cannon plug to one of the engine's two Full Authority Digital Engine Controls (FADEC) was the cause. The FADEC software was also modified to decrease the time needed for switching between the redundant FADECs to eliminate the possibility of a similar mishap occurring in the future. The aircraft was found to be damaged beyond repair and stricken from Navy's list in July