Lightly wing loaded aircraft, < 1 lbs/ft2., such as AeroVironment's high altitude solar powered aircraft PATHFINDER are extremely sensitive to the wind flows and can easily detect and measure small mountain gravity wave activity. On June 9, 1997 the Pathfinder aircraft after reaching an altitude over 67,000 ft and during descent encountered a small amplitude mountain wave produced by the 5,000 feet mountains of Hawaii's northernmost island of Kauai. The wave was detected only a few miles off shore and nearly twenty miles downwind from the north south orientated mountain range. The atmospheric conditions required for such wave formation developed steadily during the day and near landing time the winds at ridge top were 22 knots, all aligned in same direction and perpendicular to the ridgeline to an altitude of 30,000 feet, and a very stable atmosphere. By 2000 hrs local the aircraft then flying at about 12,000 feet was well into the wave. The aircraft navigated by GPS and was tracked by RADAR so determining position of the aircraft during lift and sink of the aircraft was possible. This paper will discuss the atmospheric conditions and aircraft configuration involved in a case of mountain wave production at the Naval Pacific Missile Range Facility (PMRF) at Barking Sands, Kauai, Hawaii.
The 8th Conference on Aviation, Range, and Aerospace Meteorology