The aircraft can include: an airframe, a tilt mechanism, a payload housing, and can optionally include an impact attenuator, a set of ground support members (e.g., struts), a set of power sources, and a set of control elements. The airframe can include: a set of rotors and a set of support members.

Aspects of the technology relate to a propeller blade assembly that is used in lateral propulsion systems for lighter-than-air high altitude platforms designed to operate, e.g., in the stratosphere. During operation, the propeller of the assembly is pointed along a specified heading and rotates at a selected velocity (e.g., hundreds or thousands of revolutions per minute). Power is supplied to the propeller as needed during lateral propulsion to move the platform along a particular trajectory or to remain on station over a given geographic location. In certain circumstances, the propeller may become damaged. This can include one or more blades breaking or shattering, which can result in failure of the propeller and potentially the entire LTA platform. The technology provides blades that are sufficiently flexible to avoid breakage or shattering due to debris impact or envelope entanglement, or otherwise shed a load. This can avoid catastrophic failure during stratospheric operation.

A propeller includes a hub coaxially surrounding a longitudinal axis. A ring shroud coaxially surrounds the longitudinal axis and is spaced radially from the hub. At least one propeller blade is fixedly attached to both the hub and ring shroud and extends radially therebetween for mutual rotation therewith. At least one stub blade has a first stub end radially spaced from a second stub end. The first stub end is fixedly attached to a selected one of the hub and ring shroud. The second stub end is cantilevered from the first stub end and is radially interposed between the first stub end and the selected one of the hub and ring shroud.

A propeller includes a hub coaxially surrounding a longitudinal axis. A ring shroud coaxially surrounds the longitudinal axis and is spaced radially from the hub. At least one propeller blade is fixedly attached to both the hub and ring shroud and extends radially therebetween for mutual rotation therewith. At least one stub blade has a first stub end radially spaced from a second stub end. The first stub end is fixedly attached to a selected one of the hub and ring shroud. The second stub end is cantilevered from the first stub end and is radially interposed between the first stub end and the selected one of the hub and ring shroud.

A propeller attaching device includes a coupler that rotates integrally with an output shaft of a motor, a movable body, and a resilient body. The coupler allows attachment/detachment of an attachment portion of the motor by rotation of the propeller in the circumferential direction and restricts the movement of the propeller in an axial direction. The movable body includes a second receiving portion, and is supported by the coupler so as to be movable in the axial direction. The attachment/detachment position is a position where attachment/detachment of the attachment portion to/from the first receiving portion is allowed. The restriction position is positioned in a first direction relative to the attachment/detachment position, the first direction extending from the other end to one end of the output shaft in the axial direction of the output shaft, and restricts the rotation of the propeller in the circumferential direction relative to the base.

A propeller attaching device includes a coupler that rotates integrally with an output shaft of a motor, a movable body, and a resilient body. The coupler allows attachment/detachment of an attachment portion of the motor by rotation of the propeller in the circumferential direction and restricts the movement of the propeller in an axial direction. The movable body includes a second receiving portion, and is supported by the coupler so as to be movable in the axial direction. The attachment/detachment position is a position where attachment/detachment of the attachment portion to/from the first receiving portion is allowed. The restriction position is positioned in a first direction relative to the attachment/detachment position, the first direction extending from the other end to one end of the output shaft in the axial direction of the output shaft, and restricts the rotation of the propeller in the circumferential direction relative to the base.

The aircraft can include: an airframe, a tilt mechanism, a payload housing, and can optionally include an impact attenuator, a set of ground support members (e.g., struts), a set of power sources, and a set of control elements. The airframe can include: a set of rotors and a set of support members. By utilizing a larger rotor blade area (and/or larger rotor disc area) and adjusting the blade pitch and RPM, the rotors can augment the lift generated by the aerodynamic profile of the aircraft in the forward flight mode in addition to providing forward thrust. Variants generating lift with the rotors can reduce or eliminate additional control surfaces (e.g., wing flaps, ailerons, ruddervators, elevators, rudder, etc.) on the aircraft since the thrust and motor torque is controllable (thereby indirectly controlling lift) at each rotor, thereby enabling pitch, yaw, and/or roll control during forward flight.

A propeller assembly having a hub having at least one receiver opening, a receiver located within the receiver opening and having a first collar defining a blade opening, a blade having a second collar and a protrusion with the second collar abutting the first collar and the protrusion received within the blade opening, and a first retainer, and a second retainer.

A propeller assembly having a hub having at least one receiver opening, a receiver located within the receiver opening and having a first collar defining a blade opening, a blade having a second collar and a protrusion with the second collar abutting the first collar and the protrusion received within the blade opening, and a first retainer, and a second retainer.

The present invention relates to Tetracyclic Heterocycle Compounds of Formula ##STR00001##
and pharmaceutically acceptable salts or prodrug thereof, wherein A, X, R.sup.1, R.sup.2, R.sup.3 and Ware as defined herein. The present invention also relates to compositions comprising at least one Tetracyclic Heterocycle Compound, and methods of using the Tetracyclic Heterocycle Compounds for treating or preventing HIV infection in a subject.