Boeing’s Phantom Works has taken a number of important strides toward flying the Phantom Eye high-altitude long-endurance unmanned aircraft system (UAS). The first vehicle has just completed 12 days of ground vibration and structural mode interaction tests at the NASA Dryden Flight Research Center at Edwards Air Force Base, California. It has also had its fuel tanks filled for the first time.

Phantom Eye is powered by a pair of four-cylinder, 2.3-liter engines, based on a Ford motor engine and each generating 150 hp. What is remarkable is that they are fueled by hydrogen, held in two large tanks. Nitrogen was used for the first tank-filling tests, which focused on fueling procedures and assessment of the air vehicle in its full-weight configuration.

Boeing has developed the Phantom Eye as a technology demonstrator for a UAS that can fulfill a variety of roles, including persistent ISR and communications relay.

The demonstrator is designed to stay aloft for up to four days, flying at 150 knots at an altitude of 65,000 feet with a 450-pound payload, but ultimately Boeing is planning for larger vehicles with greater endurance and payload capacity.

Originally due to fly earlier this year, Phantom Eye is now scheduled to make its first flight from Edwards in late summer.