DRIVE SYSTEMS & DUCTED FANS
The Drive System survivability is integrated with the aircraft design to allow continued aircraft operation with one fan operating or with both fans inoperative with the main gearbox functioning normally. The fans may be damaged or the center and/or either fan gearbox may be damaged or have the lubrication lost and the main gearbox can power the aircraft back to a safe landing site using the main rotor controls and power to the main gearbox.
The main transmission is designed to continue to rotate without lubrication but the gearbox may lose power.
The gearbox is designed so it will not jam if lubrication and power is lost so the aircraft can operate similar to a gyrocopter with the fans providing the propulsion and the main rotors providing the lift. This allows the aircraft to find a suitable landing site and auto rotate to the ground.