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Probe With No Moving Parts Measures Flow Angle
March 11, 2011

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Innovators at NASA's Armstrong Flight Research Center have developed, flight-tested, and patented a force-based flow-angle probe (FLAP) for measuring local flow direction. Local flow angle measurements are critical in many fluid-dynamic applications, such as aerodynamic flight testing of new aircraft and flight systems, engine flowpaths, extreme environments, pipelines, and nautical systems. The Armstrong-developed probe is a small aerodynamic, low aspect ratio fin with no moving parts. The probe computes flow angle from forces measured by strain gauges mounted to the upper and lower surfaces of the probe. A correlation is then used to convert force-measurement data to the local flow angle. Conventional flow angle probes use a pivoting "weather vane" mechanism to determine local flow direction, but these designs are relatively bulky and thus have limited application for evaluating fluid flow in small regions, confined spaces, or harsh environments. Such probes are ill-suited for transonic and supersonic regimes flown by many military and research aircraft because they are affected by local shock waves. In addition, conventional probes cannot be utilized in specialized environments such as engine flowpaths due to their size, movement, response time, and intolerance to extreme temperatures. To further reduce the size of the Armstrong innovation, conventional strain gauges can be replaced with fiber optic wires, which are even more sensitive to strain. A probe with strain-detecting fiber optic wires can be used to perform tests on individual streamlines in an airflow, rather than simply to monitor gross airflow behavior.


  • Robust: Provides high quality measurements in a probe with no moving parts in conventional or extreme environments
  • Scalable: Offers the potential for miniaturization to measure flow in small confined areas
  • Versatile: Computes quantitative measurements in very small and confined regions, in aerospace, nautical, and pipeline systems
  • Flexible: Measures local flow direction in transonic and supersonic regions and in a variety of fluid types and environments


This technology has potential to be used by commercial and military aircraft manufacturers, commercial nautical systems, commercial pipelines, as well as researchers measuring local flow angle in aerodynamic and hydrodynamic environments:

  • Wind tunnel testing
  • Water tunnel testing
  • Flight testing


Armstrong has one patent issued (U.S. Patent No: 6,526,821→ ) for this technology.

Additional Information

› Read "Probe Without Moving Parts Measures Flow Angle"→ published in NASA Tech Briefs

Commercial Opportunity

This technology is part of NASA's technology transfer program. The program seeks to stimulate development of commercial uses of NASA-developed technologies. NASA is flexible in its agreements, and opportunities exist for licensing and joint development. Armstrong is interested in a partnership to commercialize this technology.

Contact Information

If you would like more information about this technology or about NASA's technology transfer program, please contact:

Technology Transfer Office
NASA's Armstrong Flight Research Center
PO Box 273, M/S 1100
Edwards, CA 93523-0273
Phone: (661) 276-3368
E-mail: DFRC-TTO@mail.nasa.gov

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