Orin Brenning's Freewing Aircraft

by Orin Brenning, Neil Fosnaugh, and Dick Porter

Preface
In the late 1960s and early 1970s, while on the staff at the Battelle Memorial Institute, I led four NASA-sponsored studies to predict the dynamic behavior and gust alleviation virtues of this unconventional freewing concept. I’ve been into Radio Control (RC) since the 1980s and had often thought about building an RC model of such an airplane, but never stayed with it beyond designing a suitable airfoil section. I happened to mention this to former Ohio State University classmate, Orin Brenning, who has a history of designing and building unconventional airplanes. After briefly thumbing through my dusty old project reports, Orin took it from there and produced a very impressive airplane. Neil Fosnaugh had successfully flown a variety of unconventional models, and readily agreed to be the project’s test pilot.
—Dick Porter

Design, Build, and Fly
A Freewing—What’s that?—Will it fly? It sounds strange, but the freewing is mounted on a spanwise hinge on the fuselage so the wing angle of attack can be adjusted to change the lift completely independent of the angle of the fuselage.

Quite a few of you saw the model we had at the Shrine Temple show and you might think the wing would flop around and not know where it should be pointing. Not so. The pivot point is at the 15% chord whereas the center of lift is near the 25% chord, so the lift always tends to align the wing to the air flow at an angle of attack determined by the deflection of a full span trailing edge control surface. For this, the surfaces are controlled in the elevon mode on the transmitter, and serve the same function as the elevators on a conventional airplane. For roll control, they serve as ailerons and move in opposite directions.

So, in effect, the wing simply behaves as a flying wing. The fuselage just goes along for the ride, being balanced near the wing pivot point, and has no influence on the wing itself except to provide directional stability to the total airplane by the presence of the vertical tail.

Will it fly? We aimed to find out, although we already knew it should unless we goofed on something. We called upon Neil Fosnaugh for the initial efforts. The first attempt at flight didn’t go too well. On the takeoff run, as it lifted off, the weight came off the wheels and the fuselage nosed down. Since it looked as if the propeller might strike the ground, power was reduced. The wheels touched down in high grass and it flipped over, breaking off the vertical fin. A week later, while taxiing for takeoff, the tail wheel mounting broke loose, apparently having been damaged in the earlier attempt.

On the next attempt, Neil made two flights that were flawless. In flight, the airplane looks like any other most of the time, but not always. The angle of attack of the fuselage is controlled, completely independent of the wing, by small horizontal stabilators located at the rear. By deflecting these surfaces, the angle of the engine thrust can be “vectored” to help provide additional lift, allowing very slow minimum flight speeds. In the model, the stabilator has three positions. In the normal position, the airplane in flight appears as any other. The second position creates a moderate nose-up attitude, while the third might be called extreme. It creates a fuselage angle of attack approximately 45° larger than that of the wing. It looks a bit weird, but is completely controllable. Neil flew two more flights, doing loops, and even inverted flight. To a bystander, these appeared the same as they would for a conventional airplane. Then Orin flew, using a buddy box with Neil. All went well until the landing when the airplane flipped over its nose. A little practice should correct that.

Now the bad news. At the end of the fourth flight, Neil took control and prepared to land. At the east end of the runway and close to the road, he suddenly had no control on any channel. The airplane went in nose down with significant engine power. It was badly damaged. The fuselage was demolished but wing damage was minor. At first, it looked like a winter project to rebuild, but after sorting things out, reasonable progress on rebuilding has already been made.

Immediately after the crash, finding the root cause was a first priority. As Neil started checking out the receiver, the crystal was found to be loose. At that point, the pins were completely free of the socket. That explained the loss of control, but not how the crystal came loose. It’s unlikely that the crystal came loose during the crash. The other possibility is that it came loose over time in flight. Perhaps a small piece of Scotch Tape over the crystal is the solution.

Neil Fosnaugh’s Pilot’s Report
Over the years I have had the opportunity to fly many different model aircraft. It has been interesting and a lot of fun. This freewing aircraft is the most unique and unusual I have flown by far. There were only a couple unexpected things on first flight attempts. Really, there were no more new airplane adjustments than usual with the average maiden flight. That’s a real tribute to Orin Brenning’s ability as a designer/builder with something so unique and no plans or instructions to follow. I wanted to add something to this report because flying this aircraft “feels” different more than it looks different. I have flown canards, autogiros, flying boats, and some other odd stuff. More relevantly I have flown deltas and tailless bats, etc., which are flying wings. Some fly well, but many don’t.

The freewing flies extremely well. Unlike other designs, this one won’t stall. I tried and it won’t. The wing angle of attack freely and automatically adjusts itself to prevent stalling. With power off and full up in the ailevators, it has a rate of descent according to what forward speed and lift balances it out to be.

One of the first odd “feels” it has is when you put in up elevator to begin a climb. Nothing appears to happen—like it isn’t responding, and that is always a bad feeling. Then it gradually begins to climb with no apparent pitch up on the fuselage. My eyes expect to see a change in pitch immediately when you pull elevator, whether the airplane is conventional, flying wing, canard or whatever. A quick pull on the elevator gets a few feet gain in altitude and then it flies on. Now, with a more sustained pull on the elevator, it sets into a climb and will continue it without sustained elevator until it runs out of speed, then it levels off. It takes a noticeable amount of time for the horizontal stabilizers to redirect the fuselage to follow the wing’s changing direction of flight, but it does. Before I flew it, I didn’t think the fuselage and engine thrust would follow the wing and allow a loop. I envisioned the thrust continuing forward more or less horizontally with the wing in a more positive angle of attack and overall the airplane climbing. Wrong visualization on my part. It loops well in a medium size. It won’t loop small, since there’s that little delay for the fuselage to adjust its pitch upward as the wing pitches up and the direction of flight changes upward. As this happens, the horizontal stabilizers get the fuselage and thrust angle to follow into the changing direction of flight as directed by the changing direction of airflow. In a nutshell, the fuselage pitch doesn’t determine the pitch angle of flight like “normal.” The fuselage pitch follows the direction of flight after a discernable delay. Cause and effect are reversed for fuselage pitch angle. This is not as discernable when observing as when flying and watching the airplane respond to your stick movement. Feels odd.

It will fly upside down and does it pretty well for the airfoil that it has. It will roll if it has decent forward airspeed. Rudder response is medium effective; nothing strange.

Now for the more obvious strange part. The horizontal stabilizers are also on a transverse tubular spar, which can rotate into three positions. Usually the stabilizer is set to keep the fuselage pointed into the direction of forward air flow and keeps it level in horizontal flight. With the stabilizer position on a three-position switch, flipping the switch to the middle position rotates the stabilizer about 20-25°, I’d guess, which immediately pitches the nose of the fuselage up by that much while the wing flies on with no change in its angle of attack. Tendency to then climb or fly level depends as much on the power setting as on the elevator since the thrust is pointed upward that much. Flipping the switch to the third position sets the stabilizer and the fuselage at nearly 45° up pitch. Going to the first setting is like slamming on the brakes. It takes significant power to keep forward flying speed and controllability reasonable. Flipping to the second position is like hitting something solid. It slows down so much and so quickly that it literally looks like it hit something head on. It takes all the power it has to keep moving forward. We need more flights to check these flight modes out and learn how to fly it on the throttle. Very slow forward speeds are certainly possible. It won’t stall, but it can get really mushy and descend. We’ll have to get a better feel for that.

Flying this thing has been a blast and a real mind bender. I felt really bad it was hurt by one of the million possible things that can go wrong with an RC system. It had nothing to do with the airframe, which performed so well. I hope it’s a Phoenix and rises again.

Afterward
Orin completed the repairs and on July 23rd, Neil made a completely successful test flight. The freewing is once again capable of raising eyebrows and questions this flying season. Q

Orin Brenning's Freewing Aircraft