Experimenter

April 2013

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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doors—but they got it done. And while it seems like a strange place for a bubble, it's not there to look through; it's there to allow more shoulder room. A bubble was also blown into the skylight to add a little stiffness. Normally, according to Scott, people opt for a thicker (0.09-inch) sheet of Lexan than what the plans specify to create the one-piece windscreen and skylight, to give the windscreen a little more rigidity. But Scott has proven that by adding some compound curves to the transition from windscreen to skylight, it stiffens the entire piece enough that thinner, lighter (0.04-inch) Lexan is sufficient. The Garrett JFS 100-13A Turboshaft Engine The turbine engine Scott chose, in its factory stock configuration, is a jet-fuel starter for an LTV A-7 Corsair II. It's designed to nestle up along the main powerplant, geared into the accessory housing, spinning the main turbine and thereby starting the engine. As a starter motor, as opposed to a ground power unit, it has some very distinct advantages, even though it's only designed to run for four minutes at a time. One, it's been tested up to 30,000 feet, and it has to be able to restart the aircraft's jet engine at those altitudes. It's also been designed (and tested) to a higher standard since it's an airplane part as opposed to a ground-based accessory; so it's a little lighter and has tighter tolerances. Most auxiliary power units are direct drive, whereas this is a "free turbine" that works more like the torque converter in your car, where the turbine disc driving the compressor rotates independently of the discs that power the prop. You basically have a combustion-driven fan blowing on the fan that spins the prop. The advantages to this arrangement is the lack of a need to install a prop that's capable of feathering (although many will argue that a windmilling prop causes more drag than one that's stopped) and the fact that a smaller, lighter electric starter motor can be used since it doesn't have to be powerful enough to rotate the prop and any Te two-piece cowl is completely hand fabricated from sheet aluminum, including the blisters and louvers. Details of the empennage, including gap seals and trim tab. EAA Experimenter 19

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