The German experimental glider Lippisch DM 1 was crucial for the evolution of delta-wing aircraft, finally leading to the first jet-propelled delta-wing aircraft: the Convair XF-92A. Its massive flight tests by Convair and the U.S. Air Force led to the development of the Convair F-102 Delta Dagger, the F-106 Delta Dart, and the B-58 Hustler supersonic delta wing bomber. The DM 1 was designed in a lineup of 1,400 aircraft between 1956 and 1988 for the U.S. Air Force and Air National Guard, making significant contributions to military aviation.
Alexander M. Lippisch, a visionary aircraft designer from Germany, spent years of his life pressing for the future of new aircraft configurations. Between 1921 and 1945, he conducted more than one hundred design projects, leading to the flight of some sixty types of aircraft, including the revolutionary Messerschmitt Me 163 Komet rocket fighter. The Komet was the very first operational combat aircraft in the world to be powered by a liquid-fueled rocket engine, and first entered service in May 1944. The Komet now, of course, is on display at the Steven F. Udvar-Hazy Center, Chantilly, Virginia.
The aircraft builders and engineers realized that straight wings and thick airfoils could not be capable of the task of designing wings for supersonic flight. Lippisch designed one such delta wing planform: the name derives from the Greek letter “Delta,” Δ, and resulted in some beneficial effects for high-speed flight: reduced drag at high speeds and still generated the requisite lift at the surface areas for use at slower ones. The structural feature offered by the delta wing enabled very thin wings with relatively low drag penalties yet loaded with tensile strength.
In the spring, Lippisch took over leadership of the Luftfahrt-Forschungsanstalt Wien and started working on the project “P 13 a,” a semi-tailless supersonic fighter aircraft. When Allied bombing became effective in accomplishing their goals, Germany desperately needed better fighter aircraft that could be built quickly and inexpensively. Lippisch envisioned the P 13 as propelled by a ram-jet engine burning a mixture of coal dust and heavy oil or gasoline.
The German Air Ministry (RLM) showed interest in the P 13 project because, at that time, several firms had already developed semi-tailless or all-wing designs for fighter aircraft with power plants based on jet turbines or rocket engines. Good examples are the Me 163 B-1a and the whole wing of the Horten Ho 229 V3, which also appears at the Steven F. Udvar-Hazy Center. Lippisch designed the P 13 a with a cantilever structure, 60° nose angle, and 15% profile thickness.
The P 13 design was a wind tunnel tested by experts at Spitzerberg Mountain near Vienna using a scale model. By August 1944, at the AVA wind tunnel test installations at Göttingen, the design was proven to have aerodynamic characteristics. Lippisch then pushed for the construction of a full-size, engine-less version of the aircraft. This would be towed aloft by a powered aircraft to permit a test pilot to study its takeoff, landing, and handling qualities.
A young assistant of Lippisch’s, Wolfgang Heinemann brought him around to the idea that students from the Flugtechnische Fachgruppe (FFG) at Darmstadt Technical College who regularly worked on difficult aeronautical problems could build the glider. They began work in August 1944, the new aircraft design being D 33, although Lippisch later said it should have been “P 13 a V1.”
However, construction stopped dead in its tracks when Allied bombers struck Darmstadt, including the building where the FFG experimental glider project was housed. I will write next time about how this had a further impact on the completion of the D 33.