Benefiting from lessons of the Centurion HALE UAS, the wingspan was extended to 247 feet, and the aircraft was renamed the Helios prototype. Initial low altitude flight testing was completed successfully under battery power at Edwards Air Force Base in 1999. Helios was then equipped with high-efficiency photovoltaic solar cells and performed high-altitude flight testing in the summer of 2001 at the U.S. Navy Pacific Missile Range Facility (PMRF) in Kauai, Hawaii.
On August 13, 2001, during its second high-altitude flight, Helios reached 96,863 feet, shattering the existing world altitude record for sustained level flight for both propeller and jet-powered aircraft (the SR-71A spy plane was the previous record holder, having flown to 85,068 feet in July 1976).
This historic milestone, reaching well above the planned operational altitude of 65,000 feet, further demonstrated the viability of AeroVironment’s concept for stratospheric platform technology in support of government and commercial applications. The Helios prototype was the precursor to the Global Observer Stratospheric Persistent UAS.