Experimenter

FEB 2015

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.

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EAA Experimenter 15 lined strut fairings that Terry sold industrywide for many years are now sold through U-Fly-It. ENGINE CHOICE MAKES THE ULTRALIGHT When fi rst introduced in 1997, the Aerolite 103 fl ew with a 35-hp, two-cycle 2Si 460-F35 engine that weighed 66 pounds. A year later, production shifted to an 85-pound Rotax 447 engine when the 2Si became unavailable. The Rotax 447 was popular, but the weight increase meant that the Aerolite 103 was pushing the ul- tralight weight limit with minimal options allowed. When Raber returned 13 years later to AirVenture 2010, he had switched to the 28-hp, single-cylinder Hirth F-33 with a displacement of 313 cubic centimeters. It weighs only 55 pounds ready to run and leaves plenty of room for airframe options with weight to spare. A standard Aerolite 103 can be almost 20 pounds under the limit with the Hirth. It's a repudiation to the claim heard in the 1990s that it's too hard to build a legal-weight, fi xed-wing ultralight with full three-axis controls. The German-built Hirth F-33 is still a two-cycle engine and a single cylinder as well, but there is no ignoring the weight-to- power advantage. The engines have gotten better over time, but to be fair, anytime you have two cylinders or less, it's always best to have someplace to go if you lose power. It's not that hard when you can land in 130 feet like the Aerolite 103 will. The engine has dual CDI ignition, a charging system, belt reduction drive, and electric start. It uses premixed fuel at an 80-to-1 ratio and does not have oil injection. The starter is cranked with a lithium bat- tery weighing a mere 1 pound, 5 ounces. With 25 pounds of torque, the Hirth is also fl ying powered para- gliders, single-seat trikes, and other FAR 103 ultralights. Dennis said they get more than 200 pounds of thrust from the F-33 with a 60-inch prop. The Aerolite 103 will climb 600 feet per minute (fpm) with this engine and cruise at 60 mph on 80-percent power. This bird is not a slow "fl oater." It gets up and moves right along. The fl aps must be rigged a few degrees downward (even with this small engine) to prevent the ultralight from exceeding the 63-mph speed limit for ultralights. Takeof s are shortened about 30 feet with 15 degrees of fl aps. Dennis (not a little guy) made plenty of takeof s from the ultralight runway at AirVenture going uphill with this engine, and it fl ew well. To get a close-up view, please watch the video " Ride along in an Aerolite 103 at AirVenture ." Here is a tip from Dennis about vibration. He frequently equips the single-cylinder Hirth with the simple Balance Masters prop-balancing ring on the prop fl ange. It sometimes helps tame vibrations, but maybe only by 10 to 15 percent. On a hunch, he installed a similar, specially made of set balancing ring on the magneto end, under the recoil starter cover. He said the second ring dramatically reduced engine vibrations by maybe 50 percent. It was like turning a switch on and of , he said. If the Hirth F-33 is not to your liking, U-Fly-It also of ers the Kawasaki 340 and 440 engines, the Rotax 447 and 503, and other applicable Hirth models. The Aerolite 103 can meet legal ultra- light weight with 32-hp twin-cylinder, inline, air-cooled Kawa- saki 340, but most of the other engines will put it over the limit. A The Aerolite 103 features robust aluminum tube-and-gusset construction in the landing gear area. A four-cycle, V-twin Briggs & Stratton engine on the Aerolite 103, shown here at Sun 'n Fun, is now mounted under the wing, according to reports on the Aerolite Facebook page. A view of the cockpit, control yoke, and the push-pull control cables.

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