NASA's Green Flight Challenge

A handful of eco-friendly aircraft battle it out in Santa Rosa, California.

Only a handful of teams successfully completed the requirements necessary to compete in the challenge. One of those teams was Pipistrel-USA, which entered the competition with a four-seat dual fuselage electric aircraft known as the Taurus G4. NASA/Bill Ingalls

Another is e-Genius, a motor glider powered by a 60kW electric motor. NASA/Bill Ingalls

**The PhoEnix is the third aircraft to compete for the $1.65 million prize purse. The aircraft is powered by a 100 hp Rotax 912ULS engine.
** NASA/Bill Ingalls

**Here, Pipistrel-USA is being pushed back to the competition's weigh-in hangar in preparation for the first flight of the challenge.
** NASA/Bill Ingalls

Competition personnel prepare noise measurement equipment on Monday. Part of NASA's challenge included meeting a noise level beneath 78 dBA at full-power takeoff. NASA/Bill Ingalls

Team members prepare the Taurus G4's wings for weight measurement. NASA/Bill Ingalls

A competition inspector looks over Pipistrel-USA's aircraft as it sits on a scale built into the floor. NASA/Bill Ingalls

Taurus G4 pilot David Morss weighs in at the beginning of the competition. NASA/Bill Ingalls

Pipistrel-USA prepares to exit the weigh-in hangar. NASA/Bill Ingalls

The e-Genius undergoes similar weight measurements before the start of the competition. NASA/Bill Ingalls

An inspector speaks with the e-Genius team during the weigh-in process. To compete in the contest, aircraft had to be no greater than 6,500 pounds with less than or equal to 4,500 pounds on the main gear and less than or equal to 2,000 pounds on the nosewheel or tail-wheel. NASA/Bill Ingalls

Inspections of the e-Genius continue. The team is led by Eric Raymond of California, and boasts an impressive set of partners, including Airbus. NASA/Bill Ingalls

Competition personnel set up noise measurement equipment along the runway at the Charles M. Schulz Sonoma County Airport. NASA/Bill Ingalls

Pipistrel-USA takes off on Monday during the first flight of the competition. NASA/Bill Ingalls

Pipistrel's Taurus G4 is seen here on approach to land, with a Grumman Albatross below. NASA/Bill Ingalls

The PhoEnix takes off during Monday's competition round. NASA/Bill Ingalls

**The PhoEnix team is led by Jim Lee of Florida. Here, the aircraft completes the initial flight challenge.
** NASA/Bill Ingalls

Embry Riddle's EcoEagle takes off as part of NASA's challenge on Monday. NASA/Bill Ingalls

While flying in the competition, the EcoEagle is not vying for the prize. NASA/Bill Ingalls

Pipistrel-USA's Taurus G4 passes beside a Grumman Albatross at Sonoma County Airport. NASA/Bill Ingalls

The e-Genius takes off on Monday during its first flight at the competition. NASA/Bill Ingalls

All three teams, Pipistrel-USA, e-Genius and PhoEnix, completed the Monday test flight successfully, passing both the noise and take-off clearance requirements. NASA/Bill Ingalls

Competition personnel discuss the challenge on Tuesday, as the competing aircraft prepare to take part in the 200 mile fuel efficiency flight test. NASA/Bill Ingalls

The e-Genius aircraft is towed out onto the runway shortly before the miles-per-gallon flight. NASA/Bill Ingalls

To complete the flight successfully, competing aircraft must fly 200 miles within a time period of no more than 2 hours, all while using less than one gallon of fuel per occupant. NASA/Bill Ingalls

The e-Genius pilots discuss the upcoming flight with another team member. NASA/Bill Ingalls

The e-Genius aircraft prepares for take-off. NASA/Bill Ingalls

Pipistrel-USA's Taurus G4 also prepares for take-off for the fuel efficiency test flight. NASA/Bill Ingalls

A competition personnel team member waves Pipistrel-USA on. NASA/Bill Ingalls

The PhoEnix is waved on for the fuel efficiency flight as well. NASA/Bill Ingalls

The PhoEnix prepares for take-off. NASA/Bill Ingalls

The EcoEagle lines up to participate in the fuel efficiency test with a demonstration flight. NASA/Bill Ingalls

The Embry-Riddle Aeronautical University, EcoEagle prepares to takeoff as an demonstration aircraft for the miles per gallon (MPG) flight during the 2011 Green Flight Challenge, sponsored by Google, at the Charles M. Schulz Sonoma County Airport in Santa Rosa, Calif. on Tuesday, Sept. 27, 2011. NASA and the Comparative Aircraft Flight Efficiency (CAFE) Foundation are having the challenge with the goal to advance technologies in fuel efficiency and reduced emissions with cleaner renewable fuels and electric aircraft. Photo Credit: (NASA/Bill Ingalls) NASA/Bill Ingalls

Onlookers on the ground watch as the aircraft participate in the fuel efficiency flight. NASA/Bill Ingalls

Pipistrel-USA, seen from below during the flight. NASA/Bill Ingalls

A competition personnel team member waves a checkered flag as aircraft pass the finish line. NASA/Bill Ingalls

Pipistrel-USA team members look up at the aircraft as they take part in the challenge. NASA/Bill Ingalls

Pipistrel-USA pilots on the ground shortly after successfully completing the fuel efficiency flight within two hours. NASA/Bill Ingalls

The PhoEnix crosses the finish line after approximately 2 hours and 30 minutes in the air during the fuel efficiency flight. NASA/Bill Ingalls

An aerial view of the flight challenge set-up. NASA/Bill Ingalls

The e-Genius sits next to the Taurus G4. Both aircraft completed the 200 mile test flight within the required two-hour period. NASA/Bill Ingalls

The participating aircraft sit just off the tarmac. From the lower left to the upper right is the PhoEnix, the EcoEagle, the Taurus G4 and the e-Genius. NASA/Bill Ingalls