An aircraft is provided including an airframe, an extending tail, and a counter rotating, coaxial main rotor assembly including an upper rotor assembly with a plurality of blades rotating in a first plane and a lower rotor assembly with a plurality of blades rotating in a second plane, each of the blades having a root end, a midpoint, and a tip end. A translational thrust system positioned at the extending tail, the translational thrust system providing translational thrust to the airframe. The blades of the upper rotor assembly and the blades of the lower rotor assembly are indexed to improve tip end clearance between pairs of tip ends in the crossing plane as the tip ends move in respective first and second sinusoidal paths.

An aircraft is provided including an airframe, an extending tail, and a counter rotating, coaxial main rotor assembly including an upper rotor assembly with an upper blade and a lower rotor assembly with a lower blade. A first antenna in one of upper blade and the lower blade, and a second antenna in the other of the upper blade and the lower blade. An oscillator to apply an excitation signal to the first antenna. A blade proximity monitor to monitor a magnitude of the excitation signal and an output signal from the second antenna to determine a distance between the upper blade and the lower blade.

A propeller blade is provided including a leading edge and a trailing edge. The trailing edge is arranged opposite the leading edge to form an airfoil there between. At least one of the leading edge and the trailing edge include at least one facet.

A system and method to tilt coaxial counter-rotating rotor hub assemblies relative to a fuselage. The system includes a first rotor hub assembly and a second rotor hub assembly spaced apart from the first hub assembly and carried by the fuselage. The method includes pivotally attaching the first rotor hub assembly and the second rotor hub assembly to a pivot joint and thereafter tilting the first rotor hub assembly and the second rotor hub assembly about the pivot joint with a driver.

A propulsion system for a ducted fan vertical takeoff and landing aircraft (VTOL) powered by multiple electric motors with two, counter rotating electric motors comprising the primary thrust generation within a ducted fan component and 3 or more external electric motors providing lift, stability and directional control of the aircraft. Through the use of counter rotating ducted fans, the aircraft does not require the need for internal statorseither fixed or adjustable angle. Power to the electric motors is sourced by either onboard batteries, a ground based power source via a ground to aircraft tether, or an on board fuel cell or combustion engine driving an alternator.

An embodiment flying vehicle includes a fuel cell installed in a fuselage and configured to supply power to the fuselage and an auxiliary thruster installed in the fuselage and configured to provide an auxiliary thrust force by ejecting combustion gas generated by burning a portion of fuel to be supplied to the fuel cell.

An assembly is provided for a rotorcraft. This rotorcraft assembly includes a fuselage, a tail structure, an air system and a plurality of tail rotors. The tail structure is configured as or otherwise includes a tail boom. The tail boom projects longitudinally along a centerline out from the fuselage to a distal end. The air system includes an air flowpath. The air flowpath passes from the fuselage into the tail boom and extends longitudinally within the tail boom towards the distal end. The tail rotors are connected to the tail structure at the distal end.

The aircraft includes a fuselage, an engine disposed in the fuselage, an exhaust outlet provided at a tail of the fuselage for discharging exhaust gas from the engine to the outside, and a cruise rotor positioned rearward of the exhaust outlet and generating horizontal thrust on the fuselage. The exhaust outlet and the cruise rotor do not overlap each other when viewed from the direction in which the exhaust gas is discharged.