NOISE OF THE SR-3 PROPELLER MODEL AT 2 D. AND 4 D. ANGLE OFATTACK.

THE NOISE GENERATED BY SUPERSONIC-TIP-SPEED PROPELLERS IS APOSSIBLE CABIN ENVIRONMENT PROBLEM FOR FUTURE AIRPLANES POWERED BY THESE PROPELLERS. IN FLIGHT, AS A RESULT OF THE INDUCED UPWASH FROM THE AIRPLANE WING, THE PROPELLER MAY BE AT AN ANGLE OF ATTACK WITH RESPECT TO THE INCOMING FLOW. EXPERIMENTS WERE THEREFORE UNDERTAKEN ON ONE OF THE EXISTING PROPELLER MODELS TO DETERMINE THE NOISE EFFECT OF OPERATING THIS TYPE OF PROPELLER AT ANGLE OF ATTACK. INCREASES IN THE MAXIMUM BLADE PASSAGE NOISE WERE OBSERVED FOR THE PROPELLER OPERATING AT ANGLE OF ATTACK. THE NOISE INCREASE WAS NOT SYMMETRICAL WITH ONE WALL OF THE WIND TUNNEL HAVING SIGNIFICANTLY MORE NOISE INCREASE THAN THE OTHER WALL.