WIND-TUNNEL INVESTIGATION OF EFFECTS OF SPOILER LOCATION, SPOILER SIZE, AND FUSELAGE NOSE SHAPE ON DIRECTIONAL CHARACTERISTICS OF A MODEL OF A TANDEM-ROTOR HELICOPTER FUSELAGE

摘要

A low-speed investigation was made in the Langley stability tunnel to study the effect of spoiler location, spoiler size, and fuselage nose shape on the directional stability characteristics of a model of a tandem-rotor helicopter fuselage.nThe model was found to be directionally unstable at certain posi¬tive angles of attack. This instability was found to result, in general, from a large unstable fuselage moment that resulted from the potential flow pressure peaks in the vicinity of the fuselage nose and a low tail effectiveness, a factor that was shown to be associated with the adverse effect of the fuselage sidewash on the tail. The use of a spoiler 0.45 inch high at a position 3.50 inches from the fuselage nose was an effective means for making the fuselage directionally stable at all angles of attack investigated a result that had been obtained previ¬ously for a nonoverlap-type fuselage. Decreasing the spoiler height from 0A5 to 0.30 inch generally resulted in a decrease in magnitude of the stabilizing yawing-moment coefficient at angles of attack of -30°, -10°, and 30°;however, at an angle of attack of 10° the smaller spoiler was ineffective in stabilizing the fuselage-tail configuration. Substi¬tuting a blunt hose section for the tapered nose section resulted in a fuselage-tail configuration that was directionally stable at all angles of attack of the investigation except an angle of attack of 30°