US Patent 9688404 Stabilized airborne drop delivery

Stabilized airborne drop delivery using an Unmanned Aerial Vehicle (UAV) is described. In one embodiment, the UAV includes a flight controller configured to control a flight path of the UAV, a winch mechanism secured to an underside of the UAV, a platform tethered to and extendable from the winch mechanism, and a ballast system configured to stabilize the platform. The winch mechanism may be relied upon to drop an item for delivery without landing the UAV. Because the use of the winch mechanism may give rise to certain design and operating considerations, various active and passive flight and/or ballast control systems are described. These systems are configured to maintain an orientation of the UAV, the platform, and/or the item during one or more stages of airborne drop delivery.