Abstract: A hybrid stratospheric airship for the combined and optimized use of aerostatic and aerodynamic force, including: an inflatable central body; a first and second inflatable wing extending from the central body protruding laterally from two opposite sides of the central body, each wing having a portion proximal to the central body, an end portion distal from said central body, a leading edge, and a trailing edge; an outer shell having a main shell portion associated with the main body, and a first and a second side shell portion associated with each wing, respectively; at least one main spar extending transversely to the central body, which supports the first and second wing and crosses the central body, the at least one main spar a rectilinear spar interposed between the leading edge and the trailing edge of the first and second wings, and connected to the distal end portions of the wings.

Abstract: A system for and method of indicating an angle of attack of an aircraft is provided. The system utilizes measurements from existing aircraft sensors so that a dedicated angle of attack sensor is not required. The system enables and benefits from a unique method that includes performing standard flight operations during a calibration flight. The system does not need any aerodynamic model of the aircraft because it utilizes information from the calibration flight to develop an estimated aerodynamic model of the specific airplane. The system utilizes the aerodynamic model and other information to estimate an angle of attack of the aircraft during flight. Finally, the system utilizes additional information to indicate the estimated angle of attack of the aircraft relative to an optimum angle of attack for the aircraft and/or a critical angle of attack of the aircraft. The system further enables recalibration, so as to accommodate aircraft aerodynamic modifications.