As my note the other day stated, last weekend I had the chance to fly the new EVO wing. Mark was interested in a second opinion and I did not give him a chance to retract the offer! I flew both his F1 with the new wings and his HRII with the standard wings. I liked flying both planes, the HRII flies just like mine, and as Mark phrased it,? It is just like climbing into an old pair of comfortable shoes? I am not a professional pilot and many of our comparison flights during the weekend were not scientifically accurate and as such can tend to be subjective. With that out of the way let me describe what I learned about the new wing.
For the last twenty five or thirty years the homebuilt movement has been dominated by variations of Van’s wings. There are many reasons for that, for example, ease of construction, low parts count, strength, etc. However, the delightful flight characteristics combined with a great high speed to low speed ratio have been what have defined the usefulness of the wing that we have all come to love. This new wing, named the EVO, which is a short form for evolution, could indeed set the stage for a shift in wing shapes. Pictures do not do the wing justice, it is quite beautiful.
But how does it fly? Mark first suggested that I do a few circuits at Taylor field. I can just imagine the thoughts that must have been going through his head when I taxied out to the runway. With a smooth application of power the tail came up as I would expect but the plane broke free of the ground sooner than I was used to. The climb seemed normal but it was strange to look out and see, not only a longer wing, but a tapered shape. A gentle turn around the pattern and a turn to final were all normal. There the similarities end. This wing has more lift and it actually exhibits a fair amount of ground effect during and after the flare. It is a remarkable difference from the high sink rate that I am used to, almost unbelievable; at slow speed, close to the numbers, it felt like a Cessna 150. I then found that a wheel landing was not what I was used to so I went around and did another not so pretty, but safe wheel landing. Mark fired up the HRII and we joined up and flew to San Marcos to pick up Luis Escobar. When we landed there I slowed the plane on final from 80 knots to seventy five knots and did a very pretty three point landing, stopping in a short distance from the numbers. Finally, after all these years I did a nice three point landing in a rocket! Other pilots seem to be able to do them but they have always been elusive for me. We took off again and flew to Lagrange TX for an EAA flyin. There were a lot of RVs there and when we taxied in quite a crowd gathered around this new bird. The first comment that I heard was from an RV8 owner who asked me if it would fit his plane. It felt good to smile and sadly shake my head as I told him that he would have to buy an F1!
Later in the day, after we had dropped Luis off, on the flight back to Taylor we climbed from 6000 feet to 10,000. At the same power settings the EVO wing got there about 800 feet sooner. We then called it a day and parked the planes for the night. During our ?loose? formation take offs that day Mark would start first and I would follow a few hundred feet behind. I consistently got into the air at the same time as he did with the standard wing but using that few hundred feet less runway.
The next morning we went out for some upper air work. We were using gps ground speeds to compare the planes. We were flying side by side, in calm air and this seemed to be a good way to compare the planes relative to one another. As the wing is still in the prototype phase no high speeds have yet been tested, nor has there been any tests with passengers or significant loads aft of the pilot. Both planes have the same engine and props. We set engine rpms at the same number by trailing one aircraft and synchronising the prop blades. Fuel flows were set using the Lycoming best power chart. With both planes using a twenty two squared power setting, and burning eleven gallons of fuel the EVO/F1 combination was eight knots faster than the HRII. Some of that speed gain is due to the fuselage shape of the F1 vs. the HRII. Before these flights I had felt that this difference was somewhere between three and five knots. Thus the EVO wing has added some top speed gain, even at this lower power setting. Then, with the HRII maintaining its power settings I lowered the manifold pressure on the EVO by one inch and leaned the engine until we were flying the same speed. At these settings the EVO was burning 1.2 gallons per hour less than the HRII.
Next we tried some clean stalls and the EVO wing broke about four to five knots slower. The flaps on the EVO wing were more effective and showed another four knots slower with full flaps, this makes the plane very close to my RV4 in stall. Stalls at moderate to low power settings are normal with a somewhat less abrupt full flap stall than in my HRII. This you would expect with the longer wing span that the EVO wing has. There was very little wind in the direction we were flying and the indicated speeds were quite similar to the GPS speeds during these slow speed runs. I did some steep left turns with the EVO wing at 60 knots indicated. The plane will turn on a dime in slow flight. Accelerated stalls in that attitude did not turn up any bad habits. In fact, the pre stall buffet is quite noticeable and occurs a couple of knots before the stall. Mark and I did some ?follow and try to catch the leader? stuff. He was an easy target, the EVO wing consistently was able to turn inside the HRII and he was unable to shake this air combat rookie. I ended the day with a very nice short field, three point landing at the Macho Grande grass strip. I have never stopped a rocket as short as I did with this landing and it took very little effort on my part.
During all the flights the airplane did not exhibit any significant signs of adverse yaw. The roll rate is slower than the HRII wing, I can not give you a definitive number but somewhat similar to my RV4. Moving the stick an inch or two either side does not produce a significant roll in the aircraft, unlike the standard wing where very small movements produce rapid turns. As you move the stick further the roll increases at an increasing rate until you can get a very satisfactory roll rate. It makes a much more stable plane than with the standard wing. The F1 is lighter in pitch feel with this wing than it is with the standard wing. One very remarkable thing that I noticed was the almost complete lack of need for elevator trim changes with speed changes. In fact I only changed the pitch trim a couple of times in six or seven flights! This will probably change as load is added but it was certainly different than the HRII in that regard.
So there you have it, a higher top speed, a slower low speed and greatly improved slow speed handling all wrapped up in a beautiful taper wing. I am sure that Mark will have more reports as the prototype testing continues but this wing is indeed an evolution of type.