SITIS Archives - Topic Details
Program:  SBIR
Topic Num:  N07-039 (Navy)
Title:  Three-axis Low Airspeed, Low-Cost Air Data Sensor for Rotorcraft
Research & Technical Areas:  Air Platform, Sensors

Acquisition Program:  PMA-261
  Objective:  To develop an accurate low airspeed three-axis air data sensor for enhanced safety of flight during low speed maneuvers, automatic flight control support, and weapons delivery.
  Description:  An accurate low air speed rotorcraft air data sensor is needed for enhanced safety of flight during low speed maneuvers, automatic flight control support, and weapons delivery. The low air speed regime is important in terms of safety and safely expending the maneuvering envelope during low speed maneuvers such as approach, rapid descent, hover, sideward, and rearward flight. At present, there are many challenges towards developing low cost, low weight sensors that work reliably at low air speeds for rotorcraft. This results in higher total ownership cost, limited automatic flight control authority, and costly systems for delivering weapons on target. Standard pitot systems degrade in capability below 40 knots due to sensitivity issues and the effect of rotor downwash. Although some specialized sensors can provide improvements over standard pitot systems, they are often complex, hard to calibrate, expensive, and/or significantly heavier than the standard systems. Optical Air Data Systems are one potential solution, but they currently can be expensive, complicated, and have substantial weight penalties. Other potential approaches involve separating the effect of rotor downwash from airspeed. There is a need for low cost, low weight, low maintenance, robust technology that can be easily introduced and integrated with existing avionics for rotorcraft such as the UH-1N, AH-1W, UH-1Y, AH-1Z, V-22, and rotary-wing UAVs. The desired capability would provide accurate airspeed down to a few knots despite rotor downwash. This capability should simultaneously provide measurement of airspeed and flow angularity in all three directions (forward, vertical, and lateral). Specifically, the low airspeed sensor of interest should have the following characteristics: (1) it should provide accurate speed measurements along the longitudinal, vertical, and lateral axes; (2) it should be easy to maintain with minimum calibration requirements; (3) it should be possible to easily retrofit the sensor with existing avionics systems without extensive structural changes to the vehicle. Small size, weight, low cost, and low power consumption are also highly desirable.

  PHASE I: Provide an initial feasability study that demonstrates scientific merit and capabilities of the proposed three-axis low airspeed sensor. If possible, this should incorporate limited laboratory scale experiments to support the analysis of the feasibility of the proposed concept. Conduct preliminary design studies to develop concepts for sensor protection from harsh environmental effects. Provide evidence via design studies, analysis, and limited laboratory testing that the proposed system can meet acceptable requirements in terms of accuracy below 40 kts airspeed (with a particular focus on airspeeds below 30 kts) and in different environmental conditions, calibration requirements, retrofit requirements, cost, weight, size, and power consumption.
  PHASE II: Design, fabricate and demonstrate a breadboard and/or limited prototype three-axis airspeed sensor. Conduct analysis supported by wind tunnel and relevant environmental testing of system. Conduct helicopter flight-tests on a naval or surrogate system to fully document the system's performance. Provide evidence via design studies, analysis, wind tunnel, environmental, and flight testing that the proposed system can meet acceptable requirements in terms of accuracy below 40 kts airspeed (and with a particular focus on airspeeds below 30 kts.) in different environmental conditions, calibration requirements, retrofit requirements, cost, weight, size, and power consumption.

  PHASE III: Develop a proptotype sensor, integrate the airspeed sensor and conduct final flight-testing using a naval production rotary-wing aircraft. PRIVATE SECTOR COMMERCIAL POTENTIAL/

  DUAL-USE APPLICATIONS: Successful development of low airspeed sensor should enhance safety and performance features of civilian helicopters. It will also assist in enhancing safety of search and rescue operations, fire-fighting, homeland defense, and in efficient transportation of loads such as lumber. Accurate low airspeed sensors will provide important data for closed-loop flight control for ‘hover and stare” operations required in reconnaissance and aerial survey.

  References:  1. Mangalam, S. M., Sarma, G. R., Augustin, Mike, and Yeary, D.: Low Cost / Low Airspeed Sensor for Helicopter Applications, AHS 59th Annual Forum, Phoenix, AZ, May 2003. 2. C. Watkins, C. Richey, P. Tchoryk, Jr., G. Ritter, P. Hays, C. Nardell, T. Willis, R. Urzi, "Molecular optical air data system (MOADS) flight experiment," Proc. SPIE Vol. 5086, p. 236-245, Laser Radar Technology and Applications VIII, Aug 2003 3. C. Watkins, C. Richey, P. Tchoryk, Jr., G. Ritter, M. Dehring, P. Hays, C. Nardell, R. Urzi, "Molecular optical air data system (MOADS) prototype II," Proc. SPIE Vol. 5412, p. 10-20, Laser Radar Technology and Applications IX, Sep. 2004. 4. Mangalam, S. M.: "Phenomena-based Real-time Aerodynamic Measurement (PRAM) System for Aircraft Performance, Safety, and Control." IEEE Aerospace Conference, Big Sky, MT, March 2003.

Keywords:  Airspeed; Sensor; Air Data; Rotorcraft; Helicopter; Low Speed

Questions and Answers:
Q: 1. Would three axis measurement of true ground speed be an acceptable alternate to the air speed sensor?
2. Would three axis measurement of true ground speed be of interest as a supplement to air speed measurement?
3. If answer to 1 or 2 is yes, then to what minimum altitude must the three axis true ground speed sensor operate for the important operational circumstances (low speed operations, weapons delivery, automated flight control)?
A: 1. No. Three axis measurement of true ground speed is not an acceptable alternate.
2. While supplemental measurement of true ground speed is of interest for some applications, it is not the focus of this topic.
3. Not applicable.
Q: 1. Would three axis measurement of true ground speed be an acceptable alternate to the air speed sensor?
2. Would three axis measurement of true ground speed be of interest as a supplement to air speed measurement?
3. If answer to 1 or 2 is yes, then to what minimum altitude must the three axis true ground speed sensor operate for the important operational circumstances (low speed operations, weapons delivery, automated flight control)?
A: 1. No. Three axis measurement of true ground speed is not an acceptable alternate.
2. While supplemental measurement of true ground speed is of interest for some applications, it is not the focus of this topic.
3. Not applicable.

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