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A variable noise reduction system consists of equipment on board an airplane that is designed to reduce noise in the vicinity of airports. They are anticipated to be used on supersonic civil aircraft currently under development by industry. They are investigated in this paper for a notional 55,000 kg supersonic business jet. The airplane concept was developed by NASA for use in environmental impact studies conducted by the International Civil Aviation Organization. The variable noise reduction system investigated implements a programmed thrust lapse procedure and a programmed flap retraction procedure. The procedures are expected to reduce noise in aircraft certification as well as in operational practice. Behavior of the aircraft in a noise certification setting is considered. Variables of the procedures are optimized to reduce noise levels. The optimization results in a reduction of 5.2 decibels (in the cumulative effective perceived noise level, measured in EPNdB) relative to levels reported previously. Certification considerations unique to these systems are discussed for transport-category large airplanes and jet-powered airplanes. A novel method for evaluating lateral noise is used.
A variable noise reduction system consists of equipment on board an airplane that is designed to reduce noise in the vicinity of airports. They are anticipated to be used on supersonic civil aircraft currently under development by industry. They are investigated in this paper for a notional 55,000 kg supersonic business jet. The airplane concept was developed by NASA for use in environmental impact studies conducted by the International Civil Aviation Organization. The variable noise reduction system investigated implements a programmed thrust lapse procedure and a programmed flap retraction procedure. The procedures are expected to reduce noise in aircraft certification as well as in operational practice. Behavior of the aircraft in a noise certification setting is considered. Variables of the procedures are optimized to reduce noise levels. The optimization results in a reduction of 5.2 decibels (in the cumulative effective perceived noise level, measured in EPNdB) relative to levels reported previously. Certification considerations unique to these systems are discussed for transport-category large airplanes and jet-powered airplanes. A novel method for evaluating lateral noise is used.
Advanced takeoff trajectories are proposed for supersonic transport noise reduction by capitalizing on excess engine thrust and improved aerodynamic efficiency at higher takeoff speeds. These novel trajectories use i) automatic continuous control of thrust, ii) increased takeoff speed, and iii) reduced cut-back altitude, compared to conventional pilot-initiated discrete thrust cut-back procedures currently used for subsonic transport. In this paper, we develop an optimal control framework to assess the attributes of effective takeoff trajectories for supersonic transport that yield minimum noise levels. We quantify the noise reduction potential of advanced takeoff trajectories for the eight-passenger, 55-metric-ton, Mach-1.4 NASA Supersonic Technology Concept Airplane. For the aircraft examined, these advanced takeoff trajectories enable a cumulative certification noise reduction of 10.6 EPNdB, which is insufficient to meet current subsonic transport noise limits.
The recent interest in the development of supersonic transport raises concerns about an increase in community noise around airports. As noise certification standards for supersonic transport other than Concorde have not yet been developed by the International Civil Aviation Organization, there is a need for a physics-based scaling rule for supersonic transport takeoff noise performance. Assuming supersonic transport takeoff noise levels are dominated by the engine mixed jet velocity and the aircraft-to-microphone propagation distance, this paper presents a reduced-order model for supersonic transport takeoff noise levels as a function of four scaling groups: cruise Mach number, takeoff aerodynamic efficiency, takeoff speed, and number of installed engines. This paper finds that, as cruise Mach number increases, supersonic transport takeoff noise levels increase while their thrust cutback noise reduction potential decreases. Assuming constant aerodynamic efficiency, takeoff speed, and number of installed engines, the takeoff noise levels and noise reduction potential of a Mach 2.2 aircraft are found to be [Formula: see text] higher and [Formula: see text] less compared to a Mach 1.4 aircraft, respectively. This scaling rule can potentially yield a simple guideline for estimating an approximate noise limit for supersonic transport, depending on their cruise Mach number.
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