A&S: It seems like a bold move for Honda. Do you think the boldness was attractive to the President of Honda Motor?
Fujino: Actually, many of the board members were skeptical about the airplane project, but traditionally the president of Honda Motor comes from engineering background, and Honda is the kind of company that understands the product very well. Many Western companies are run by financial people. But in Honda’s case, the substance of the business is to build the best product and to sell with honesty or to sell with quality. That is the kind of circumstance of the business. And from such point, the president thinks we have to explore more long-term markets. Of course Honda’s looking at 3 years [out] and 5 years [out]. But we’re also looking at 10 years and 20 years as well. They just don’t concentrate on 3 years or 5 years only. Very few but some in management still have a very big picture. There are some broad-thinking people. They have a very good balance between a short-term business and a long-term business.
I think at the time [I made my proposal] the president had understood the future of mobility and his responsibility as a mobility company. He understood that a small airplane was a good thing to be pursuing.
A&S: Did the president say yes right away?
Fujino: Actually, he took about 30 minutes. But maybe he understood not only the potential of the market, but my enthusiastic explanation.
A&S: Did you expect when you began working on the over-the-wing engine mount for the HondaJet that you would need to find an optimum position, a “sweet spot” as you’ve called it?
Fujino: My first goal was to find the position which minimized the penalty, so at the time, I didn’t think we could turn [the configuration] into an advantage. After many theoretical studies, I found an optimum sweet spot, but at the time, we had not conducted experiments, so I could not hundred percent believe the result; it was only theory. So I decided to conduct experiment by using wind tunnel. And wind tunnel test results validated my theoretical concept.
A&S: When you tested your 1/8 scale model at the Boeing Wind Tunnel facility, what were the reactions to your over-the-wing engine mount?
Fujino: Yes, you know the Boeing engineers are very professional and very nice people, so they did not directly say this to me, but I heard them whispering, “This is a very bad design. He obviously doesn’t know anything about airplanes.”
But after a week or so, they started to understand that we understand what we are doing. And also they took a look at some of the data. They were kind of impressed that we were doing very sophisticated things. So they changed. And at the end of the tests, we had dinner with them and they said Honda people are really smart.
A&S: With these tests, were you also refining the shape of the pylon?
Fujino: The first concept was the nacelle position. So we didn’t concentrate on the shape of the pylon too much; our research concentrated on the position of the engine first. But also, if you mount an engine on the wing, you have to have a pylon structure or support structure. And that is also very critical: the shape of the pylon and nacelle configuration is very, very critical. There are many design constraints in the pylon. First, the pylon should not produce any side force. If it produces a side force, that causes a drag penalty. I tried to find a very sophisticated shape not to produce the side force. And also the pylon shape is very important for the stall characteristic. I checked the best pylon shape from a high-speed standpoint and a drag standpoint and the stall characteristic standpoint.
That’s why, probably you noticed, that the pylon is uniquely curved.
A&S: It looks a little like a wing standing on its side.
Fujino: Right, right. That shape comes from those detailed design studies.
A&S: Then you put that in the wind tunnel and discovered…
Fujino: First that the pylon and nacelle shape were giving us a very high-divergence Mach number. [That means that a sharp increase in drag, associated with local airspeeds approaching Mach 1 was delayed; the aircraft could fly faster—closer to Mach 1—before encountering the drag penalty]. When you see the HondaJet, you will notice the unique shapes of pylon and nacelle. They were designed to delay the increase in drag caused by the compressibility effect.