Airplane flow control wind tunnel test. NASA engineer (right) bracing himself against strong winds in a wind tunnel while operating a device that is emitting a stream of smoke. This smoke trail is used to visualize 'in flight' air flow across the aircraft tail (left). This tail was salvaged from a Boeing 75MB7 and modified with a system called Active Flow Control. Tiny jets called actuators have been added to the test structure and are being used to blow air across it. The tests will aid the design of smaller tails to improve fuel efficiency. Photographed in 2013 at the National Full-Scale Aerodynamic Complex at at NASA's Ames Research Center, California, USA.