Alpaero, a small firm in the southern French alps (hence its name?) created an ultralight sailplane/motorglider about 10 years ago that was originally powered by a two-stroke engine. Recently, though, it’s gone green with a four-stroke, Briggs & Stratton engine and even greener with an electric motor version. Claude Noin, the designer, wanted to answer the request for a “light autonomous sailplane at a reasonable cost,” able to meet ULM (ultralight) qualifications. The fixed engine behind the cockpit configuration avoids the complexity of the retractable engine configuration, which Alpaero says can increase drag two or even three times over that of the “clean” sailplane when the engine or motor is extended. As Dick Van Grunsven has pointed out, the need for motor extension usually occurs at some low point in the flight, when other options have been exhausted. Even the clean design of his Antares motor system produces a noticeable drop in gliding performance, he notes. The large cockpit has …
Small car, Small motor, Big Launch
This recent video from FES (Front Electric Sustainer) in Slovenia shows a relatively low-budget way to launch and sustain a sailplane in flight. This was uploaded to YouTube by Lumakaja on September 27, with the following commentary. “This way of sailplane start, can make gliding much cheaper! Idea is simple: Use of FES after being airborne with help of auto-tow. Only a few sailplanes have high enough landing gear, so that propeller clearance on grass is not too small for safe self-launch. With minimal help of auto-tow than all FES equipped sailplanes would not need towing plane or winch any more to become airborne. All you need is FES equipped sailplane, usual car and about 120 meters (384 feet) of Dyneema rope. Such start could be used also on relatively short, let say 750 meter (2,460 feet) long airfields, which are otherwise too short for usual winch or car launch! If only short runway is available, then more powerful car is needed for …
A Weighty Matter
Several readers have asked for the weights of the Green Flight Challenge competitors. Here they are, pound for pound, among the most efficient flying machines on the planet. Those who wish can calculate different takes on that efficiency, including overall glide ratios for the course, ton-miles per gallon energy equivalent, or more exotic parameters. Empty Weight Takeoff Weight in Competition Pounds Pounds e-Genius 1670.2 2070.2 Pipistrel G4 2491.0 3294.1 Embry-Riddle 1970.0 2370.0 Phoenix 754.0 1199.7
How Green was GFC Electricity?
The blog received several comments about the relative energy use of electric aircraft, and how NASA and the CAFE Foundation might have overstated the efficiency and low emissions for the electric aircraft in the competition. Reader Robert Swanson thought the conversion between kilowatt hours and gasoline created a discrepancy. “The discrepancy in performance of gasoline and electric powered aircraft is due to an absurd conversion factor between kWh and gallons of gasoline. The conversion should be calculated from the number of gallons of gasoline consumed by the engine driving the generator used to charge the batteries.” Steven Crow added this objection. “Even after reading the relevant pdf’s, it is far from clear to me how CAFE computed ‘mileage’ for the electric aircraft. The right way of doing it is clear enough: base the mileage on the fossil fuel used to charge the batteries. Electric motors and batteries are not subject to Carnot efficiency limitations. They can seem to be nearly …
Dipping and Coating for Better Batteries
Could dipping electrodes in a secret sauce improve supercapacitor and battery endurance and power? Could coating cell internals be the flavor of the month? These recipes for better batteries may improve things at a better than normal rate, if California researchers have anything to say about it. Working with his compatriot Dr. Jaephil Cho in South Korean, Dr. Cui of Stanford University has been a leader in developing improved battery technology, even developing a painted paper battery. In an appearance at the 2009 Electric Aircraft Symposium, Cui explained a basic truth of battery development – that improvements generally created about eight percent greater power or endurance in cells every year, leading to a doubling of battery capabilities every seven and one-half years. He aims to improve that rate of change in batteries and ultracapacitors. Although ultracapacitors are able to charge and discharge rapidly, they are only about one-tenth as energy dense as batteries of equivalent mass. Cui and colleague Zhenan Bao …
Green Flight Challenge Final Results
Steve Williams, CAFE Foundation board member and e-totalizer guru, released the final results for the NASA Green Flight Challenge sponsored by Google, held at the Charles M. Schulz Sonoma County Airport from September 25 through October 1, 2011. Figures show a profound difference between the two electric winners and the two gas-powered and hybrid runners-up. All competitors flew extremely clean motorgliders with demonstrated lift-to-drag ratios between 25:1 and 35:1. Possible explanations for the large differences in energy use include low cooling drag for electric aircraft and the efficiency of electric motors – but the differences are still surprising. Note that a little over 11 US gallons of gasoline (energy equivalent) were used to fly seven people (Embry Riddle’s Eco-Eagle flew with only one pilot) over a total of 725.5 miles (Embry Riddle flew a shorter total distance on both “runs”). This is an enormous achievement for all concerned and a significant increase in efficiency over even the best general aviation craft available today. Congratulations are …
NASA Adds Some Numbers to Green Flight Challenge
NASA’s Mark Moore sends this link to NASA’s press release on the recent NASA Centennial Challenge Green Flight Challenge sponsored by Google. The CAFE Foundation organized and managed the event. “Today we’ve shown that electric aircraft have moved beyond science fiction and are now in the realm of practice.” – Chief technologist at NASA Joe Parrish. The lead quote is informative, as are some figures from the release. “The competition resulted in the world’s most efficient aircraft, beating the state of the art of approximately 100 pmpg (passenger miles per gallon) which is achieved by the newly released Boeing 787 airliner. Essentially this contest showed the ability of small aircraft to achieve twice the efficiency of the most efficient production automobiles today, while traveling at over twice the speed.” Part of this efficiency came about because of inspired design. NASA explains, “The Taurus G4 used a multi-body concept (reminiscent of the twin Mustang, or an inverse P-38); this accomplished a 61% useful …
AVweb Readers Weigh In on Electric Aircraft, Green Flight Challenge
Mary Grady of AVweb started an expanding dialogue with her recent opinion piece on NASA and the CAFE Foundation’s Green Flight Challenge sponsored by Google. The stimulating and varied points of view reflect what is probably floating around in the general public’s perception of “green aviation,” ranging from total ignorance of what has been done already, to confusion about what it all means, to well-honed, technically aware arguments on both sides of the issue. Her thought that electrification is, “the first step down a long and bumpy road that could take general aviation in new directions,” was reinforced with the following reflections that might be similar to those that readers of this blog often experience. “For people who fly for fun — presuming there are many of those left, it seems to be one of the fastest-shrinking segments of GA — electric airplanes are sure to appeal. They are easier to deal with, and quieter, with less vibration. A few …
No Pain in This Membrane
On September 30, the National University of Singapore announced the world’s first energy-storage membrane, with the claim that it “outstrips existing rechargeable batteries and supercapacitors,” and according to Science Daily, “Surpasses existing rechargeable batteries and supercapacitors.” The cheese-cloth appearance looks a bit like a gauze bandage, but when sandwiched between what are alternatively described as two thin metal plates or two graphite plates can hold a significant charge much greater than that of conventional batteries or supercapacitors. The material, developed by a team from the National University of Singapore’s Nanoscience and Nanotechnology Initiative (NUSNNI), and led by principle investigator Dr Xie Xian Ning, is capable of holding a “charge at 0.2 farads per square centimeter. This is well above the typical upper limit of 1 microfarad per square centimeter for a standard capacitor,” according to the University. Because energy storage in capacitors is usually measured in farads, How Stuff Works calculates the following to help us understand what that means …
Green Flight Challenge Winners
Monday, October 3 was the second day of Nobel Prize announcements, but also marked the Green Flight Challenge Expo, sponsored by Google and staged under the control tower on Moffett Field, home of NASA Ames Research Center, Mountain View, California. The four airplanes that flew in the Challenge at Charles M. Schulz Sonoma Country Airport in Santa Rosa, California were joined by Greg Stevenson’s full-size mockup of his GFC design and a Pipistrel Virus that had won an earlier NASA/CAFE Personal Air Vehicle (PAV) Challenge. Stevenson’s airplane was a reminder that there were numerous entrants that, for a variety of reasons, could not attend. There is a huge number of aircraft in the wings, so to speak, that will fill these pages in the next months and years. 20 exhibitors showed off their visions of a greener future, and three rows of tents protected exhibitors and their displays from the rain that started mid-afternoon. At about 11:00 a.m., attendees were bussed to Building …