Inexpensive Turbine Power
By David Juwel
Scott Ehni and Kary McCord brought a Zenith 701 to AirVenture, which wouldn't ordinarily be news, except their 701 uses a turbine for go-power. The first question I asked Scott was, “Why put an engine in an airplane that surely costs a great deal more than the airplane?” He stated that, “We actually built the turbine for less money than a high-end Rotax engine.” Wow! That got my attention.
The turbine is a Garrett Jet Starter from an A-7 Corsair which required a little modification. They paid $20,000 for it. The engine is rated to 30,000 feet, although they've never had the aircraft over 10,000 feet. The biggest advantage of the turbine is that they have no issues with density altitude, they can burn any kind of fuel, they build turbo time for only $50.00 an hour, and if they actually needed to, they could fly at VNE all day long without issue. In spite of the turbine, the aircraft is flown within the flight specifications of the manufacturer. Keeping the engine performance married to the limits of the aircraft design specifications has the side benefit of less fuel flow. They also have to be careful of the type fuel they use because different fuels leave different deposits and residues. For instance, you wouldn't want to use leaded fuel. The plane carries 42 gallons.
Back in Texas, these guys have a complete CNC workshop with a punch, brake, shears, and mills. This allowed them to do much more with the aircraft and engine than a typical garage-builder could do. So they did. The aircraft is fully upholstered, has a 2-axis autopilot, and electric trim. A series of small modifications were also made to reduce weight. These changes allow them to fly with full fuel.
I suspect when they wind that turbine up on a flight line at a strange airport, that people really get confused because they can’t find the corporate turboprop that the noise is coming from.
Besides being the topic of conversation and photography wherever they go, I asked Scott if there have been any other benefits. He stated that because they built something so unique, it has brought in an additional $750,000 in their business. It’s given them the reputation that they can do anything, so everything is brought to them.