October 2012

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/84816

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Page 14 of 47

looks bigger than he should in com- parison to the airplane. But that's it. You can look at it from any angle and it has 'that' look! It looks like a Mustang. The best part, however, is that from the pilot's point of view, it is indeed a Mustang." As indicated by the sewer pipe- size exhaust stack on each side of the nose, Bill's Stewart Mustang isn't just any Stewart Mustang. Bill explained, "Jim Stewart originally designed the S-51 to be powered by a big-block Chevy, a 454 or larger, with a gearbox to reduce prop rpm. However, when Bob Wahl built this airplane back in 1999, he decided to go with a Czech-built Walter 601D turbine that puts out 724 hp. He sold it to a friend of mine, and in 2004 I bought it. I'd always wanted a Mustang and now I had one! Sort of, anyway." An obvious question is "How does one learn to fly a 724-horse, single- place taildragger?" "I had about 150 hours of taildrag- ger time," Bill said, "most of that in Cubs and Huskys. I had bought a Super Cub, then a Husky, to use in teaching my son how to fly. So, I didn't have a lot of tailwheel time. Plus, even though I'd flown RF-4s in the USAF, I'd never flown a civilian airplane with that much power. My checkout consisted of Brad Hood kneeling on the left wing while I sat in the cockpit. He said something to the effect of '…and then you flip this switch, turn this lever, and…' I was really keyed up, so you can imagine how I felt when I taxied out to the end of the runway and couldn't get the canopy cranked all the way shut. I had just gotten my nerves under control, then had to taxi back, spend three hours fixing the canopy, then had to go out and do it again. It was double jeopardy! I was nervous, but the first part of the flight went without a hitch. Photography by Tyson Rininger Power for Bill's aircraſt is a Walter 601D turbine engine. "I had flown about an hour and done five or six landings, then was taking it back to my home field when things went wrong. I had touched down, and the airplane wanted to start a very slow turn. I put the engine in beta with the tail off the ground, but I couldn't keep it straight. Then I noticed a wingtip going down and I knew a gear leg was folding. This was all happening in slow motion, and I had no problem keeping the wing up as long as possible. Then I gently let it down and watched as each prop blade hit the ground, each one making a very distinctive, unpleasant noise. Then I ground to a halt only about four feet left of the edge of the runway." An autopsy of the folded gear showed that two problems had worked together to bend Bill's air- plane: a design change that upgrad- ed the main gear trunnion axles from 1015 mild steel shafts to 4130 chro- moly hadn't been communicated to the original builder. Plus, too many holes had been drilled through the trunnion axle for the down-lock col- lar. The result was a break through the bolt holes, which allowed the gear to collapse. Bill said, "The wing hit hard enough that there was a three-inch crack in the main spar with a shorter one in the rear spar. Both were just outboard of the gear mount. The flap was kinked in the middle, and the prop was trashed. The internal condition of the engine was a big question, so it went out to Diemech Turbines in DeLand, Florida, the Walter engine experts, where it was torn down and rebuilt. Fortu- nately, since it wasn't a sudden stop, the internal condition was surprisingly good. In the meantime, I started taking things apart. Very shortly I decided that if you're go- ing to get this far into an airplane, you might as well do everything you've wanted to do, and that's EAA EXPERIMENTER 15

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