Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.
Issue link: http://experimenter.epubxp.com/i/434207
EAA Experimenter 31 ature foam, carbon-sandwich structure, which saved several pounds. He innovatively combined weight savings and aerody- namic improvements with his wheelpants. "The new wheel- pants have the split line at the laminar transition so no zigzag tape is required," he said. "They weigh only 21 ounces with paint and hardware." Smaller weight-savings opportunities that Klaus took on are too numerous to list. "I put in a great deal of ef ort to make things light," he said. "But the result was the lightest Long-EZ with a Lycoming IO-360 engine. Most such airplanes weigh in at over 1,100 pounds. Mine is 900 pounds." THE DETERMINATOR 'S PERFORMANCE The Determinator, with its propulsion, aerodynamic, and weight improvements, has transitioned beyond what could be considered a Long-EZ. "No engineer would ever design a plane with too much power and too much wing and too little weight," Klaus explained. "It turns out for a cross-country ma- chine, there's nothing better. At high altitude—17,500 feet—it loses only 5 or 6 knots over sea level speeds." Klaus explained that the airplane "plows" less than others; its wing loading is only 13 pounds/square foot so the nose stays down when the air is thin. The Determinator wing doesn't present as much area to the wind and has less drag at these lower angles of attack. "Some popular planes with much heavier six-cylinder engines can't even go that high because they just need too much angle of attack at these altitudes," he said. Klaus says that the Determinator is a fast cross-country machine. "A 900-pound airplane with 250 hp does really well at altitude," he said. "It puts out about 250 hp at sea level. Air at 17,500 feet has half the density, so you still have 125 hp at altitude. But at 17,500 feet the drag is halved also. Given the already low-drag airframe, that helps the airplane to go very fast." This speed at altitude gets him to Oshkosh from Cali- fornia quickly. "I've never seen a piston airplane that loses so little speed at altitude." How fast does the Determinator fl y? At this year's Bronze Race at Reno, Klaus averaged 263 mph—and that is going around in circles, an inef cient fl ight pattern. Klaus' average speed documented for the AirVenture Cup was 270 mph. "A few Long-EZs with high-compression piston O-360 engines may top out at 240 mph," he said. The next fastest Long-EZ in the AirVenture Cup averaged 229 mph. Klaus is getting almost 20 percent speed improvement over the next best speed-im- proved Long-EZ at Oshkosh! Speed isn't the only performance improvement that Klaus was after. The ef ciency-obsessed engineer notes the De- terminator's fuel mileage is more than 41 mpg at 250 mph true airspeed above 15,000 feet. This, plus his 49-gallon fuel capacity, allows him to fl y almost anywhere in the United States nonstop. Of course, the mileage improves further with reduction of speed, all the way to around 100 mpg at best glide speed. (VBG is where all airplanes get their best fuel mileage.) It is interesting to note that VBG refers to indicated airspeed. Flying at VBG at 17,500 feet adds about 50 mph to your true airspeed! A more stock Long-EZ with an O-360 engine at 220 mph would achieve only 25 to 30 mpg, compared to Klaus' 41 mpg—Klaus burns 64 percent less fuel while cruising 14 percent faster! The fuel ef ciency of Klaus' airplanes surprises most ex- perienced pilots. In 2003, he fl ew his O-200-powered VariEze in the Reno National Championship Air Races. At the end of the week of racing, as pilots stood in line at the cashier to pay their fuel bill, the other race pilots' jaws dropped with shock and envy: Klaus' bill for the week of fl ying came to only 17 gal- lons—and that included the fuel to fl y home! ADVICE When asked for words of wisdom for other aircraft experi- menters, Klaus contemplated for a while. Referencing the time and money he spent making his exhaust heavier, he advised, "It's really important that you don't get too at- tached to your wonderful ideas. You have to be man enough to take it back out." (An alternate phrase used at Boeing was "You have to be able to admit that your baby is ugly.") All people who successfully modify their airplanes know that the improvement process—to understand the situation, design a fix, and test the fix—takes some time to master. To understand the situation, you not only have to pinpoint the problem element on the airplane, but you have to under- stand the system—how that one element affects the rest of the airplane in different flight conditions. To design a fix, you have to be knowledgeable about what and how to build and install the improvement. To test the fix, you have to have a well-planned test program, implemented methodi- cally by someone competent to flight-test the airplane. As Klaus' Determinator demonstrates, it is possible to modify an airplane to get amazing results. However, it is also possible to inadvertently mess up an important part of the system. Klaus' final words of wisdom for aspiring aircraft ef- ficiency experts: "Use an abundance of caution." The cautious Klaus reflected back on his hundreds of ideas to improve his airplane's propulsion, aerodynamic configuration, and weight and said, "I make the changes even though the increment of gain might be so small you might never measure it." Klaus does not have sophisticated instruments or a wind tunnel. But he has the intuition, the expertise, the persistence—plus the determination—to undertake a 31-year improvement effort that gives him un- paralleled efficiency and speed. If slow and steady wins the race, then Klaus will win many, many races. Lynne Wainfan has been a private pilot for more than 30 years. Originally an aerospace engineer, then a manager at Boeing Space, Lynne now consults and teaches at California State University, Long Beach. Readers may remember the Facetmobile experimental airplane, which was built by Barnaby and Lynne Wainfan and Rick Dean.