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Eye of the Experimenter

NASA Green Flight Challenge, Day 2

By Patrick Panzera, Editor – Experimenter, EAA 555743

G4 Takeoff
The Pipistrel Taurus G4 departing Runway 1/9, using as little power as possible to clear a 50-foot obstacle located 2,000 feet from the point of brake release.

Day 2 of NASA’s Green Flight Challenge featured noise and takeoff qualifying flights and  the weather for the day was seemingly “made to order” with deep blue skies and a brilliant sun warming everyone nicely at Sonoma County Airport in California. The aircraft benefited from the cooperative weather, too, with all competitors passing the first task - that being sound, or noise if you prefer. At any point if the wind had decided to blow more than 10 mph, the day’s mission would have been scrubbed.

Monday started out where Sunday left off, with the CAFE team verifying that the competition aircraft met the minimum standards and were then impounded. During this time, the CAFE board of directors had to meet to discuss how to deal with the Embry-Riddle team who, despite a valiant two-year effort, didn’t meet the letter of the law with respect to the rules.

The rules were very clear that if a plane had two or more seats, as least two of them had to be filled with humans, not ballast. The team was not prepared to do this based on the university’s rule that two souls were not allowed to occupy an experimental aircraft during flight, so they had to forfeit. There was another issue pertaining to the installation of a ballistic parachute that really became moot due to the university’s two-seat rule.

eGenius eGenius
All the competition aircraft had to remove their
wings or outer panels in order to fit in the CAFE hangar.

Just after lunch, e-Genius was done with its inspections and it was time to compete. The CAFE board members decided it was in everyone’s best interest to allow Embry-Riddle to fly its Eco-Eagle in the competition, but not as part of the official contest, and especially not for any of the prizes.

CAFE also opted to not weigh Eco-Eagle, and it was clearly stated that the university’s participation would not be allowed to impede any part of the competition. For example, during Monday’s sound check flights, they were put at the end of the line and had the winds picked up so that they weren’t able to participate that day, there would not be a make-up flight the following day, as the schedule permitted. All the other participants were allowed this option if necessary.

The pilots during the morning briefing.

As for the sound-check flights themselves, all went very well. All four of the aircraft were measured as under the sound limit. e-Genius opted to make a second pass and bettered its results. Although the official results are guarded, to this reporter’s ear, e-Genius was the quietest. The rules for this event are as follows:

The Community Noise Requirement is that all vehicles must demonstrate 78 dBA, slow scale, maximum takeoff noise emission when measured from two separate microphones located 250 feet on each side of the runway centerline, and near the aircraft brake release point during its two full power takeoff distance flight attempts. This dBA level is approximately twice as stringent as the current FAA standard for GA.

CAFE officials calibrating the system.
The “ears” of this event.
With the bright sun, it was a little difficult reading the display of the sound measuring equipment.

But again, from where I was standing and by my ears, the aircraft throttled back as the performance requirement stated that they had to clear a 50-foot obstacle (monitored by surveying equipment, but visually marked by a flag) at 2,000 feet from the brake release point, and these planes, with their high-aspect ratio wings, potentially could have cleared twice that in half the distance.

Of course the two electric aircraft were noticeably quieter than the Rotax-powered Phoenix and Embry-Riddle’s hybrid Eco-Eagle, but they were still very quiet by any standard.  

The official sound-check site of the CAFE GFC, 250 feet off of centerline of Santa Rosa's Runway 1/9. 

Starting 2,000 feet away from sound recording instrumentation, the e-Genius departs Runway 1/9. We really can't hear any of the airplanes until about halfway through the video as the sound of a turboprop aircraft is drowning it out.

Although this event is a pass/fail requirement for participating in the competition for the main prize, it’s my understanding that there is an additional prize for the team who has the quietest aircraft.

Awards will presented on Monday, October 3, at the Google Green Flight Exposition, hosted by NASA, at the NASA Ames Research Center, Moffett Field, Sunnyvale,  California. Members of the public can reserve free tickets for the exposition at http://cafefoundation.org/v2/gfc_2011_GFE_main.php.

Embry-Riddle’s Eco-Eagle started out as a Stemme S10 self-launch glider, refitted with a Rotax engine augmented by a belt-driven electric motor. The 100-hp Rotax 912 burning biofuel is assisted by a 40-hp electric motor and lithium polymer batteries. A true hybrid, the internal combustion engine is used to supply electric power for either running the motor or charging the batteries.


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