Low -altitude wind conditions on Helios flight days at Kauai, HI"

The Helios solar / fuel cell powered airplane flys at low speeds due to its large wing area and very low wing loading. Hence, flight days are limited to those with speeds below 10 knots on the runway and speed aloft which are less than its maximum cruise speed (near 20 knots at sea level and 50 knots near 50,000 feet altitude). Its light wing loading combines with structural flexibility to produce noticeable responses to turbulence. As a result of an in-flight mishap on June 26th 2003 comparisons of wind conditions that day with previous flight days were accomplished. This paper reviews the details of the low altitude wind profiles measured on June 26th at Lihue (on the south-east coast), at the Pacific Missile Range (airfield on the west coast) and in-situ winds measured by Helios along its flight track. Winds measured on other flight days are also compared at selected altitudes. Relative findings are discussed with respect to wind induced turbulence in the wake of Kauai.