Joint efforts by the National Aeronautics and Space Administration (NASA), the Department of Defense, and industry partners are enhancing the capability of airborne wind and turbulence detection. The Airborne Coherent Lidar for Advanced In-Flight Measurements (ACLAIM) was flown on three series of flights to assess its capability over a range of altitudes, air mass conditions, and gust phenomena. This paper describes the observation of mountain waves and turbulence induced by mountain waves over the Tehachapi and Sierra Nevada mountain ranges (California, USA) by lidar onboard the NASA Airborne Science DC-8 airplane. The examples in this paper compare lidar-predicted mountain waves and wave-induced turbulence to subsequent aircraft-measured true airspeed. Airplane acceleration data is presented describing the effects of the wave-induced turbulence on the DC-8 airplane. Highlights of the lidar-predicted airspeed from the two flights show increases of 12 meters per second (m/s) at the mountain wave interface and peak-to-peak airspeed changes of 10 m/s and 15 m/s in a span of 12 seconds in moderate turbulence.
Pulsed Doppler lidar sensors can provide accurate range-resolved wind velocity measurements with sufficient spatial resolution to detect turbulent wind features. Application of this technology to commercial airliners would enable much-needed advanced warning of moderate to severe turbulence ahead. CTI, with NASA/Dryden, has developed the Airborne Coherent Lidar for Advanced Inflight Measurements (ACLAIM) which was recently flight tested aboard a research aircraft. This paper presents results from these initial engineering flights, with validated demonstration of Doppler lidar wind turbulence detection using the observed spatial and temporal variations in the longitudinal component of the wind field.
Atmospheric turbulence adversely affects operation of commercial and military aircraft and is a design constraint. The airplane structure must be designed to survive the loads imposed by turbulence. Reducing these loads allows the airplane structure to be lighter, a substantial advantage for a commercial airplane. Gust alleviation systems based on accelerometers mounted in the airplane can reduce the maximum gust loads by a small fraction. These systems still represent an economic advantage. The ability to reduce the gust load increases tremendously if the turbulent gust can be measured before the airplane encounters it. A lidar system can make measurements of turbulent gusts ahead of the airplane, and the NASA Airborne Coherent Lidar for Advanced In-Flight Measurements (ACLAIM) program is developing such a lidar. The ACLAIM program is intended to develop a prototype lidar system for use in feasibility testing of gust load alleviation systems and other airborne lidar applications, to define applications of lidar with the potential for improving airplane performance, and to determine the feasibility and benefits of these applications. This paper gives an overview of the ACLAIM program, describes the lidar architecture for a gust alleviation system, and describes the prototype ACLAIM lidar system.
Atmospheric turbulence environments can adversely affect the operation of both commercial and military supersonic aircraft. Future aircraft designs, such as the High Speed Civil Transport will aim to alleviate the effects of supersonic engine inlet unstart. Fluctuations in air temperature, longitudinal and transverse velocity all can trigger inlet unstarts. With fore- knowledge of the turbulence, a feed-forward control system can be used to re-configure the propulsion systems to avoid unstarts. The same technology can be used to counteract gust effects to improve ride quality and reduce gust loads. A coherent lidar sensor is being developed to demonstrate that the atmospheric turbulence can be measured with sufficient reliability, fidelity, and pre-encounter time for these feed-forward control solutions. The NASA Airborne Coherent Lidar for Advanced In-flight Measurements (ACLAIM) program will develop and flight test a sensor on NASA research aircraft, including the SR-71, and investigate the atmospheric environment to establish the feasibility of a lidar sensor. The paper will present an overview of the ACLAIM program including: the scope and content of the program, lidar measurement challenges, atmospheric environment, technology choices, and anticipated problem areas.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.