National Helicopter Experts Gather to Discuss Aerodynamic Solutions for Brownout

  • Published
  • By William J. Sharp
  • AFOSR Public Affairs
ARLINGTON, Va --  Air Force Office of Scientific Research program managers here recently organized a workshop of national experts to work the problem of helicopter brownout.

At the University of Maryland, College Park, Md., AFOSR program managers - Drs. (Lt. Col.) Rhett W. Jefferies, Victor Giurgiutiu, and Fariba Fahroo - brought together experts in helicopter and tilt rotor aerodynamics and design and DoD pilots with operational experience in desert conditions.

Brownout can occur when helicopters takeoff or land in dry, arid regions. Spinning rotors cause dust to swirl upward around the aircraft resulting in a dust cloud in which flight crews can lose visibility. Loss of visibility affects the pilots' ability to control and stabilize the aircraft and hinders aircrew situational awareness of the landing zone. Brownout is an Air Force concern as the service has more than 200 helicopters in its inventory supporting a variety of missions to include combat search and rescue, special operations, and distinguished visitors support.

"Brownout is not a new problem to the Air Force but one of high priority, especially in light of our current operations (in the Middle East)," said Dr. Mark Lewis, chief scientist of the Air Force. "We want to chart a course for the Air Force to solve the problem. We want to look at what areas need discussion now, which areas need additional emphasis, and what areas and technologies we need to explore."

"Workshops such as this provide an invaluable opportunity to expand and leverage discussion among organizations with rotorcraft expertise," Dr. Lewis said. Attendees focused talks on brownout operations, helicopter aerodynamic design features influencing brownout, and experimental investigation of helicopter brownout. Participants also discussed future research considerations, technical issues, key collaborations, and research tools. Experts in attendance included representatives from the Air Force Research Laboratory, Air Force Special Operations Command, Army, Augusta Westland, Bell Helicopter, Boeing, Cold Regions Research and Engineering Laboratory, Continuum Dynamics, Marine Corps, NASA, Navy, Sikorsky Aircraft, and several leading universities.

"We recognize brownout as a serious but solvable problem and now is the time to solve it," said Walt Harrington, rotary wing brownout integrated solution study lead, Air Force Research Laboratory Sensors Directorate, Wright-Patterson Air Force Base, Ohio. "We (researchers) are looking to achieve a number of results toward solving brownout. We may, for example, be able to aerodynamically design or modify aircraft to improve brownout characteristics. We may be able to restore the visual cues with which pilots learned to fly the aircraft. We also may be able to reduce task difficulty and workload through the use of automation."

Dr. Lewis said, "An Air Force-led technology assessment and planning effort has already identified some potential opportunities to dramatically reduce the impact of brownout through helicopter aerodynamical design." Dr. Lewis indicated the Air Force has great hopes for these sorts of opportunities.

In November 2005, AFRL received a message from Air Force Special Operations Command, Hurlburt Field, Fla., asking for assistance with the brownout problem. AFRL responded with a number of strategies. One strategy resulted in development of a photographic landing augmentation system for helicopters, a device that uses digital imagery to help pilots land. The system, called PhLASH, will begin tests onboard an AFSOC helicopter this month. Additionally, AFRL commissioned an integrated solution study. The study team developed brownout core operational tasks that provide measurable objectives from which technologists and developers can work against.

"When a lead aircraft comes in (to a sandy environment) you can often assume the air is 'clean' initially, but as soon as the first aircraft lands there is significant hazard to operations as a result of hanging dust," said Maj. Lee Anderson, an MH-53 helicopter and CV-22 tiltrotor pilot with AFSOC. "That dust cloud can sometimes be measured in square miles based on the weight of the aircraft and the number of aircraft in formation."

Solving brownout is important because "flying helicopters is not the same as fixed-wing flying," Anderson said, a former jet pilot. "There is really no relaxation point with them. The pilot is constantly making adjustments to combat instabilities present during hovering. You compensate these instabilities by becoming a human Doppler - that is, you detect and react to states of position and motion. When visibility goes away so, too, does knowledge of the motion state. If a pilot can't detect motion state, then that pilot is likely seconds away from crashing."

Upon conclusion of the workshop, attendees began evaluating available data so that additional steps in research, planning, execution, and evaluation can take place. The Air Force hopes to soon begin careful test and evaluation of possible aerodynamic mitigation approaches which may lead to a viable field solution.