I took this photo at Brown Field (SDM) in San Diego in 1978. Note the second engine and propeller mounted vertically between the tailbooms. I had no idea what the heck this thing was, until very recently, when I decided to track it down on the internet. Turns out it is "Rotor Wing No. 1", N25RW, the creation of something called Rotor Wings Systems Inc., of Coronado, California. Described as an "experimental 'Three Passenger Airplane' to demonstrate the high lift capability of an aircraft equipped with 'Turbo Wing Technology.'" This top-view photo from their brochure shows the placement of the rotor in a cuout of the trailing edge of the wing. After this yellow thing was test flown, they modified a Cessna 207 with a rotor in each wing, replacing the flaps, and likewise a Cessna 337 with two rotors in each wing. Fortunately a video survives on YouTube with the designer explaining the concept, and showing some test flight clips. What will they think of next?