To provide: a silicon nitride sintered body having excellent mechanical property, in particular fracture toughness, and having long lifetime of a product into which the silicon nitride sintered body is processed; a rolling element using the silicon nitride sintered body; and a bearing. The silicon nitride sintered body contains a rare earth element and an aluminum element. The silicon nitride sintered body contains 6-13 wt % of the rare earth element in terms of oxide, and 6-13 wt % of the aluminum element in terms of oxide, relative to the total weight of the silicon nitride sintered body. The silicon nitride sintered body contains an inclusion (I) in a surface layer portion that is a region within 2 mm from a surface of the silicon nitride sintered body. A ratio of a total sectional area of the inclusion (I) to a total sectional area of the surface layer portion is 0.05% or more.

Provided in this disclosure is a dual-motor propulsion assembly, and corresponding methods of operation, that is configured for use in an electric aircraft. Dual-motor propulsion assembly provides redundant systems by including vertically stacked motors, wherein one motor may still power a propulsor of the assembly if the other motor malfunctions or becomes inoperative.

The present disclosure provides systems and methods for predicting ground effects along a flight plan. The systems and methods provide a processor executed process including the steps: receiving a flight plan for a vertical take-off and landing (VTOL) aircraft; receiving terrain and obstacles geospatial data for the flight plan from the database; determining weight of the VTOL aircraft along the flight plan; determining temperature of the environment along the flight plan; determining ground effect data along the flight plan based on the temperature and the weight; and generating one or more commands to control a system of the VTOL aircraft based on the ground effect data.

The present disclosure provides systems and methods for predicting ground effects along a flight plan. The systems and methods provide a processor executed process including the steps: receiving a flight plan for a vertical take-off and landing (VTOL) aircraft; receiving terrain and obstacles geospatial data for the flight plan from the database; determining weight of the VTOL aircraft along the flight plan; determining temperature of the environment along the flight plan; determining ground effect data along the flight plan based on the temperature and the weight; based on the terrain and obstacles data, the ground effect data and the flight plan, predict where, along the flight plan, the VTOL aircraft will traverse a ground effect region, thereby providing prediction data; and generating one or more commands to control a system of the VTOL aircraft based on the prediction data.

A high efficiency hydrogen fuel system for an aircraft at high altitude which utilizes compressors to compress air to a sufficiently high pressure for the fuel cell. Liquid hydrogen is compressed and then utilized in heat exchangers to cool the compressed air, maintaining the air at a temperature low enough for the fuel cell. The hydrogen is also used to cool the fuel cell as it is also depressurized prior to its entry in the fuel cell cycle. A water condensation system allows for water removal from the airstream to reduce impacts to the atmosphere. The hydrogen fuel system may be used with VTOL aircraft, which may allow them to fly at higher elevations. The hydrogen fuel system may be used with other subsonic and supersonic aircraft, such as with asymmetric wing aircraft.

An aircraft operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a forward flight orientation. The aircraft has a blended wing body and includes first and second engines, a binary lift fan system, first and second forced air bypass systems and first and second exhaust systems. The engines have turboshaft and turbofan modes. The lift fan system includes ducted fans in a tandem longitudinal orientation. In the VTOL orientation of the aircraft, the engines are in the turboshaft mode coupled to the lift fan system such that the engines provide rotational energy to the ducted fans generating the thrust-borne lift. In the forward flight orientation of the aircraft, the engines are in the turbofan mode coupled to the forced air bypass systems such that the bypass air combines with the engine exhaust in the exhaust systems to provide forward thrust generating the wing-borne lift.

A vertical take-off and landing aircraft which uses fixed rotors for both VTOL and forward flight operations. The rotors form a synthetic wing and are positioned to achieve a high span efficiency. The rotors are positioned to even out the lift across the span of the synthetic wing. The synthetic wing may also have narrow front and rear airfoils which may provide structural support as well as providing lift during forward flight. The wing rotors are tilted forward and provide some forward propulsion during horizontal flight.

A method for the flying of a vertical take-off and landing aircraft which uses fixed rotors for both VTOL and forward flight operations. The rotors form a synthetic wing and are positioned to achieve a high span efficiency. The rotors are positioned to even out the lift across the span of the synthetic wing. The synthetic wing may also have narrow front and rear airfoils which may provide structural support as well as providing lift during forward flight, or may have a single center wing. The wing rotors are tilted forward and provide some forward propulsion during horizontal flight.

A hybrid power system includes a first power source that includes an internal combustion engine, a second power source that includes a battery, and a power controller. The hybrid power system is included in a vertical takeoff and landing (VTOL) vehicle that flies in a transitional mode between a hovering mode and a forward flight mode. The power controller selects one or more of the first power source and the second power source to power a rotor included in the VTOL vehicle, including by: during a landing, the power controller determines when to have the second power source provide power to the rotor, in order to supplement power provided to the rotor by the first power source, based at least in part on one or more flight state variables associated with a flight computer.

A system for in-flight stabilization including a plurality of flight components mechanically coupled to an aircraft, wherein the plurality of flight components includes a first flight component and a second flight component opposing the first flight component. The system further comprises a sensor mechanically coupled to the aircraft, wherein the sensor is configured to detect a failure event of a first flight component. The system comprises a vehicle controller communicatively connected to the sensor and is configured to receive the failure datum of the first flight component from the sensor, generate a failure notification configured to indicate that the vehicle controller received the failure datum from the sensor, and initiate an automatic response as a function of the failure datum. Initiating the automatic response further includes determining an autorotation inducement action for the second flight component to perform and commanding the second flight component to perform the autorotation inducement action.