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Alleviating Helicopter Tail Boom Loads with Passive Venting
March 11, 2011

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Innovators at NASA's Armstrong Flight Research Center have patented a method and apparatus that reduces loads on a helicopter tail boom to improve maneuverability. The innovation uses passive venting on the boom to alleviate side forces generated in hover and sideward flight as well as dynamic forces, including vibrations. The tail boom of a helicopter is subject to a complex flow field generated by the main and tail rotor wakes, the free airstream flow, and the wake from the forward fuselage. Mitigating these adverse effects results in improved helicopter control and reduced engine power requirements. A team of investigators from Armstrong and the U.S. Army determined that passively venting portions of a tail boom modifies the pressure distribution and therefore the loads on the boom. The technology employs various venting techniques that can be used alone or in conjunction with other venting devices, including strakes. Techniques include but are not limited to the use of porous material on all or parts of the boom connected to a specific plenum or open to the boom cavity, and the use of doors, grilles, slots, and other such openings. This technology is a result of cooperative work between Armstrong and the U.S. Army Aviation and Missile Command.


  • Safer: Alleviates some of the adverse side and dynamic forces generated in helicopter flight, allowing the pilot better control
  • Effective: Reduces adverse tail boom loads
  • Efficient: Reduces engine power required to control helicopter
  • High-performance: Increases performance, payload, and yaw control margins because less engine power is needed to maintain control


  • Commercial and military helicopter manufacturing
  • Helicopter retrofitting
  • Aftermarket parts manufacturing


Armstrong has one patent issued (U.S. Patent No: 6,352,220→ ) for this technology.

Additional Information

› Read "Passive Venting for Alleviating Helicopter Tail-Boom Loads" → published in NASA Tech Briefs
› Read "Exploratory Investigation of Aerodynamic Characteristics of Helicopter Tail Boom Cross-Section Models With Passive Venting"→ 

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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