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The Use of a Lidar Forward-Looking Turbulence Sensor for Mixed-Compression Inlet Unstart Avoidance and Gross Weight Reduction on a High Speed Civil TransportInlet unstart causes a disturbance akin to severe turbulence for a supersonic commercial airplane. Consequently, the current goal for the frequency of unstarts is a few times per fleet lifetime. For a mixed-compression inlet, there is a tradeoff between propulsion system efficiency and unstart margin. As the unstart margin decreases, propulsion system efficiency increases, but so does the unstart rate. This paper intends to first, quantify that tradeoff for the High Speed Civil Transport (HSCT) and second, to examine the benefits of using a sensor to detect turbulence ahead of the airplane. When the presence of turbulence is known with sufficient lead time to allow the propulsion system to adjust the unstart margin, then inlet un,starts can be minimized while overall efficiency is maximized. The NASA Airborne Coherent Lidar for Advanced In-Flight Measurements program is developing a lidar system to serve as a prototype of the forward-looking sensor. This paper reports on the progress of this development program and its application to the prevention of inlet unstart in a mixed-compression supersonic inlet. Quantified benefits include significantly reduced takeoff gross weight (TOGW), which could increase payload, reduce direct operating costs, or increase range for the HSCT.
Document ID
Document Type
Technical Memorandum (TM)
Soreide, David (Boeing Defense and Space Group Seattle, WA United States)
Bogue, Rodney K. (NASA Dryden Flight Research Center Edwards, CA United States)
Ehernberger, L. J. (NASA Dryden Flight Research Center Edwards, CA United States)
Seidel, Jonathan (NASA Lewis Research Center Cleveland, OH United States)
Date Acquired
September 6, 2013
Publication Date
July 1, 1997
Subject Category
Aircraft Propulsion and Power
Report/Patent Number
NAS 1.15:104332
Meeting Information
Joint Propulsion(Seattle, WA)
Funding Number(s)
PROJECT: RTOP 529-50-24-00-RR-00-000
Distribution Limits
Work of the US Gov. Public Use Permitted.

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NameType 19990042110.pdf STI