NASA-TN-D-8133

Abstract

An investigation was made in the Langley V/STOL tunnel to determine, by the trailing wing sensor technique, the effectiveness of a large change in span load distribution, a forward-mounted spoiler, and a trailing drag device (spline) as trailing-vortex-hazard alleviation devices on a swept-wing transport aircraft model. <br>The induced rolling-moment coefficient on the trailing models at a given lift coefficient of the generating model was generally larger for the large trailing wing model than for the small trailing wing model, and the variation of trailing wing rolling-moment coefficient with lift coefficient of the generating model was generally greater for the large trailing model than for the small trailing model. <br>The induced rolling-moment coefficient on both trailing wing models was reduced when the horizontal-tail incidence angle of the generating model was decreased to a point where a download on the horizontal tail was produced. <br>At scale downstream distances behind the generating model of less than about 16 spans, the induced trailing wing rolling-moment coefficient was larger for the flap configuration with only the inboard flap deflected to 30&#176; than for the flap configuration with both inboard and outboard flaps deflected to 30&#176;.At scale downstream distances greater than 16 spans, the induced trailing wing rolling-moment coefficients were smaller for the configuration with only the inboard flaps deflected than those for the configuration with inboard and outboard flaps deflected. These results indicate that large changes in span loading due to retraction of the outboard flap may be an effective method of reducing the trailing-vortex hazard. <br>For the transport aircraft model in the normal approach configuration (inboard and outboard flaps deflected to 30&#176;) either a forward-located midspan spoiler or a spline reduces the induced rolling-moment coefficient on the small trailing model by about 35 to 40 percent throughout the downstream distances investigated. The reduction in induced rolling-moment coefficient on the large trailing model was much less (about 15 to 25 percent).