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Excel Jet's Bob Bornhofen Speaks with the former President and COO of a well known airplane company about the new Sport-Jet.

Interview recorded by Jerry Lips, publisher of the Airport Journal family of publications

Abridged from the article published in Airport Journal - December, 2004

Robert Bornhofen

The man behind the Maverick TwinJet is well into another project. After several of his two-engine jet kitplanes achieved true airspeeds of 350 knots and exhibited superlative handling, Bob Bornhofen sold the company and began to focus on a single-engine jet for the emerging Very Light Jet class that includes such competitors as the Eclipse 500, the Cessna Mustang, the Adams A-700, and the Diamond D-Jet. However, Bornhofen is operating his company, Excel Jet completely different than the others. In this interview with a former airplane company executive, Bornhofen explains how his Sport-Jet will arrive on the scene and how it will fit the new VLJ (Very Light Jet) class in a different way than the others.

The Man Behind Sport-Jet

Tell us a little bit about your education, background, how you got here?

I graduated from Parks College of Aeronautical Technology in 1966 and then received a master's in aeronautical engineering a year later. I never really used the aeronautical part until the Maverick project and now this project.

After earning my B.S. degree, I went to University or Arizona to get a Masters Degree. My first job was on the Apollo program and then worked for 12 years on military satellites. I began to specialize in systems engineering. I left the aerospace industry in 1980 and went on my own. I got involved in a few small corporations and retired in 1998 when I sold a company I co-founded.

However, I just could not get used to being retired so I got involved in building a Seawind kit. That led to my starting the Maverick TwinJet project.

Tell us how you came to build the TwinJet?

The TwinJet was designed in anticipation of the FJX-2 engine, which was being developed under the GAP (General Aviation Propulsion) program. The FJX-2 was going to be a new generation turbofan engine producing 700-800 pounds of thrust. When delays occurred for that engine, we elected to use the T-58 engines so we wouldn't slow the TwinJet development.

The concept was, "Gee, if you build an airplane and make it certifiable - pass all the FAR flight tests, with look-alike engines - then when the FJX-2 engines come along, you're kind of ahead of everybody else." You have the aerodynamics resolved and performance data behind you. And if those work out correctly the remaining issue would be to simply re-engine the aircraft and start certification. And since we would already have the airframe proven, we would have a significant head start on competition.

That was the basic business model. We were also using the Experimental Amateur-Built category to work out any major airframe issues. At that time both Lancair and Cirrus had just received certification on their respective aircraft and both of those graduated from Experimental aircraft. So we looked around to see what engine would have similar performance characteristics to the FJX-2 and after a few false starts, decided on the GE-T58. Boat racers were using these engines by converting them from the helicopter turboshaft engine to a crude turbojet engine. While the basic conversion was "proven" to work, no one had made a flight-worthy conversion. That took some creative engineering, for example, to rework the oil distribution system, fuel controller, replacement of the power turbine with an exhaust - all necessary changes. Needless to say we did not get lots of encouragement from the original manufacturer.

Our work was quite productive. Mind you the first iteration was not as efficient as later versions but it got the aircraft into the air. We first flew to Oshkosh in 2000 and then in the middle of 2001, we put the plane through a series of flight tests - all centered on the FAR 23 flight-testing criteria. The resultant report from the pilot was the plane did not have any major impediments that would prohibit starting certification.

When we designed the Maverick, we did it in two year's time. We passed all the FAR flight tests within two and a half years from the beginning of the concept, for vastly less investment than what has been spent on other programs.

Prior to the flight testing two things occurred which influenced the anticipated certification of the aircraft. First, Williams decided not to pursue the FJX-2 engine. The second was input from the insurance side of the fence. In pursuing insurance for the aircraft and kit owners we were advised that for our market audience, a single engine solution would be considered a better solution.

That meant we had to go back to the drawing board. An offshore group who had seen the TwinJet and was looking for a single engine military version of the aircraft contacted me and I started doing some initial design work for them. Meanwhile a Mr. McCotter wanted to pursue the twin-engine solution so the aircraft found another life when it was sold in March 2001.

So, McCotter bought the rights to the Maverick?

Correct. So, far, three planes have been put in the air. The first prototype was flight tested to about 370 knots during a series of flight tests to determine if the aircraft had any major certification-related problems. I believe the other two kits have flown about the same. I have been told that that one aircraft has been to 350+ knots and the other around 330 knots after only 10 hours of testing. Typical flight cruise was 340 knots at 25,000 feet.

More importantly than the speed was the flight handling. We wanted what one might call a Learjet with training wheels, similar to the early Citations. Get rid of all the complexity. Make it easy to fly. Make it real docile. And it was. It handled in a pattern like a Beech Bonanza, Duchess or Piper Seneca.

Are those airplanes still flying?

Two are still flying. One is not - it was involved in an incident. You asked about some of the tooling. Here's some of the tooling for the tail (picture on computer shown). As I stated we do have full production tooling for all the aluminum parts. The tooling and the parts were produced in Poland. Here is some of the wing spar tooling.

The whole tail and all the wing parts are fully supported with production tooling, FAR 23 analysis and reports, ready for certification submittal pending flight tests.

It appears your passion is the engineering and making it work and recognizing the market? You kind of independently hit the market way ahead of a lot of other people. You recognized it years ago, right?

Correct. That's my passion. I'm much better in engineering than I am as a pilot. I don't have that many hours, but I see a potential market niche. I said, "Gee, you know, as the piston twins get higher and higher in price - a million dollars for a Baron and so forth - maybe there's a market out there."

Did you do the design yourself or how many were involved in the design?

I did all of the conceptual design and preliminary specification of major components. For the further detailed design of wing spar members, major structural members we have only a few engineers. In building the aluminum tooling and parts, we have I'd say 50 to 60 workers in Poland doing detailed parts engineering, tooling manufacturing, assembly, and so on.

Did you have a wind-tunnel model for it or have you done just theoretical wind-tunnel work or theoretical aerodynamics?

We didn't do any wind tunnel models. However, we did tuft the entire left side of the aircraft, the wings and tail. We placed video cameras in 3 different locations to record the flight results and flew the aircraft in all possible flight configurations. There wasn't one bit of flow separation. The Sport-Jet follows pretty closely that concept. The wing was changed from constant cord to a slight taper for better support of flutter. The horizontal tail has slight sweep and again like the wing is tapered.

The inlets were the focus of the majority of engineering attention because turbofan engines require real even airflow across the face of the engine. The biggest issues on this kind of aircraft are the inlets because of the inherent nature of a turbofan engine.

Is this because of a high angle of attack and stuff like that? Separation?

Not really high angle of attack but more keeping the airflow uniform across the face of the engine. "S" shaped inlets are a challenge and you need that type of inlet when the engine is inside the aft fuselage. Essentially the aircraft was really pretty much designed around the inlets.