Tilt-rotor

An aircraft whose rotors point upward for vertical takeoff and landing, then tilt forward to act as propellers in wing-borne flight.

• Wings make lift far more efficiently than rotors in cruise, so tilting combines helicopter-style access with aeroplane speed and range.
• The V-22 Osprey is the best-known military example; Joby's air taxi tilts all six of its propellers.
• The transition between hover and cruise is the hardest phase to control, as lift shifts from the rotors to the wings.
• Tilt mechanisms add weight and new ways to fail, and each must be shown to be extremely reliable to win certification.