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Aircraft and Payload
The UAV platform selected for the demonstration was the APV-3 airframe built by RnR Products (Milpitas, CA). RnR has extensive experience in building RC gliders, large racing class RC aircraft, and experimental composite UAV research aircraft. They have also constructed and flown specialized wind tunnel and flight test models, including a Mars Airplane model built for NASA and flown at altitudes near 100,000 ft.
The APV-3 airframe consists of monocoque fuselage structures, composite materials, sandwiched construction techniques, tapered spar and fuselage load bearing structures, and compound surface curvature to provide the maximum possible strength to weight ratio in the airframe. Full span camber control is incorporated into the airfoil systems to expand the flight envelope to permit safe, low-speed landings without compromising top end speed. Flight control systems utilize direct and simple linkages with attention to fail-safe operation. Ailerons and flaps are individually actuated for each wing, permitting safe operation of the aircraft in the event of actuator or linkage failure. Airfoil designs incorporate a skin flexure control surface hinge design reducing mechanical complexity, eliminating failure modes, and increasing the strength to weight ratio of the wing structure. The airframe is designed to withstand +10g loading, thereby providing liberal structural safety margin in normal 1-2g operational conditions.
Maximum flight speed of the APV-3 is 90 mph. At the minimum flight speed of 45 mph, the APV-3 is capable of 8 hours flight duration. The airframe design features a convenient detachable pod on the underside of the fuselage that enables remote payload integration. Including payload and maximum fuel, the gross weight of the APV-3 is 50 lbs. Minimal runway or roadway clearance is required for takeoff and landing operations. The aircraft can be partially disassembled for transport by a small pickup truck. The APV-3 was equipped with an autopilot system developed by MLB Co. (Palo Alto, CA) and a Lockheed Martin generator/regulator system that provided the payload with 40 watts of power. The autopilot system enabled the aircraft to automatically negotiate courses defined by pre-specified and dynamically configurable waypoints.
The payload consisted of nadir-viewing color and thermal infrared (IR) digital cameras and a forward-looking color video system. The color digital camera is a Model A101fc Bayer array (1280x1024) that provides high spatial resolution, geometrically coherent, RGB (red, green, blue) imagery in the visible part of the spectrum. The thermal IR digital camera is a microbolometer array (160x128) with sensitivity in the 7.5 to 13.5 micron range. Both of these sensors are small (<12 cubic inches) and lightweight (<1 lb.), with low power requirements (1.5W). They were interfaced to a common data system through a multi-channel high speed IEEE 1394 controller. Image meta-data from an on-board GPS engine and 3-axis integrating attitude sensor were encoded into the image file headers. Two wireless links were used to provide remote control of the payload at low bandwidth (19.2 Kbaud at 900 MHz carrier frequency) and rapid downlink of image data at high bandwidth (11 Mbaud via IEEE 802.11b WLAN at 2.4 GHz carrier frequency). The imaging payload and the associated telemetry components were housed in the detachable pod. The video camera was positioned on the wing along with a miniaturized chemical sensor referred to as "SnifferStar." Created by researchers at Sandia National Laboratories in partnership with the Lockheed Martin Corporation, SnifferStar is capable of detecting nerve gases and blister agents.
The payload pod also included an air traffic control radar beacon system (ATCRBS) mode C transponder and altitude encoder. These components reduced the risk of interference with other aircraft. The position of the APV-3 was monitored by the Air Traffic Control Tower at the MFA receiving returns from the mode C transponder, while the UAV team’s on-site safety officer was visually observing the strobe lights positioned on the wingtips.
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