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/118927
S c o t t Ehn i 's Tur b in e - Po w e r e d Z e n i t h C H 701 S P tion of an aluminum cuff that fits into the NSI hub and is capable of going "beta" to help the plane slow down; and in some cases, actually allow the plane to taxi in reverse. Admittedly, the NSI was giving Scott problems during EAA AirVenture Oshkosh 2012. Scott said that it "seems to have a mind of its own," changing pitch only sometimes. And of course, the propeller is the rpm governor, so pitch control is critical. Scott said, "Ironically, the only thing that's given us any trouble is something we didn't make." …Or modify. Scott seems to think that the issues with this particular prop is the bearings or the jack screw. "Something's binding—we've even gone through the trouble of installing dual contacts thinking that it might be an electrical issue." But that didn't help. Performance Flying out of Texas really isn't the best for turbines; they do better at high altitudes and cold air, and there's not much of that where Scott and Kary live. Average fuel burn is 13 gph, and at 10,000 feet they can expect a 60-percent drop in usage as compared to the same speed at sea level. The advantage is that at high altitude airports, such as Leadville, Colorado, where Scott plans to vacation, he'll still have 120 hp available at the 8,000-foot runway elevation, where a comparable piston engine may have only 60 hp. A Grand Rapids Technologies EIS was installed to keep track of more systems than Scott could mention, including cowling temperature to monitor the temps "under the hood." Of particular concern was the throttle servo that may not be well suited for high temperature applications. But the highest temps recorded thus far have not exceeded 120 degrees, so Scott and Kary feel safe with the servo being located inside the cowl. In addition to this sensor, disposable temperature sensitive adhesive indicators (those designed to change color if an out-of-range temperature is sensed) have been located all over the engine compartment and checked after each flight. And speaking of the cowl, it's all aluminum. The blisters on the cowl streamline the engine mount attachment points. So Scott had to build and learn how to use the English wheel to produce them. Throughout the dyno, propeller, and flight testing, Scott and Kary were able to download the EIS stream to a laptop computer via a "Dogcatcher" RS232 serial data logger. With the help of a computer guru friend, the information is then displayed in an Excel spreadsheet for easy digestion. Scott learned early on that one can never have enough data. "You can always throw away the extra, but it's tough sometimes to get more," Scott said. These numbers were 22 Vol.2 No.4 / April 2013 beneficial in proving the engine, keeping an eye on the possibility of bearing failures or other system malfunctions during the critical first few hours. Future Plans Plans are to eventually put the plane on floats, so if you look closely, very near the leading edge of the wing you'll notice two little tabs protruding from the interior structural tubing. They are there for two reasons. In the future Scott and Kary plan to mount the plane on floats, so these two, along with two others (aft of the cabin) are lifting attach points for hoisting the plane for the easy attachment and removal of floats. There is also a side benefit—the hangar is a little crowded, so the 701 gets stored overhead, suspended from these attachments. A rack that is adjusted for fuel loads allows the plane to be lifted level from just these two points that are obviously ahead of the CG. Scott said that since he was a kid he's had an idea for an amphibious, four-place flying boat that he'd like to build, but he didn't want that to be his first project plane. So he built the 701 to get some good building experience with nearly guaranteed results. Scott also said that he'd begin working on the flying boat as soon as he got home from AirVenture 2012. Can It Be a Practical Aircraft Engine? Scott said that if this engine finds its way into a suitable airframe, such as any number of slick, fast aircraft like some of the scale Mustangs or even the smaller fast-glass aircraft that can work with 120 hp, then 200 to 230 mph on 13 gph starts to make a little more sense. Scott is currently working with a friend who is installing the JFS 100-13A in a single-place Midget Mustang (Long Midget). Bottom line? How else can someone log turbine time for $50 per hour? Is there a future for small turbine engines in homebuilt aircraft? Not according to Scott. For him, the real future in aviation will be fuel efficiency, which except for extreme circumstances, a turbine will never be. Scott recommends looking further into electric flight for the real future of experimental aviation. In addition to being the past editor of Experimenter e-newsletter, the current editor and publisher of CONTACT! Magazine, and a regular contributor to KITPLANES, Patrick Panzera is an experienced homebuilder, EAA Technical Counselor, AirVenture forums presenter, and an instrument-rated private pilot.