sensitive to trim, and in fact have the capacity to make indoor flights in confined spaces under average conditions. Most in initial editions are equipped with catapult hook patterns, and demonstrate an ability to fly the length of a Rugby pitch when so launched. Later editions and gliders were equipped with a Bungee hook, the construction of which was included in Paper Pilot 3 and 12 Planes for the Paper Pilot. The Bungee system publish parallels, at a smaller scale, the practice used in radio controlled and full-size sailplane launches, at a fraction of the cost and complexity. To date, this is the only known example of such a launch system applied to a paper model aeroplane type published in book form. Flight performance on bungee is very good - one glider in particular, a scale model U-2 (in the last book of the series) had demonstrated flight performance in excess of 120 meters, on bungee hook launch. Papercopter A unique development of Prof. Mathews is the Papercopter, a model helicopter whose 'wing' is a trimmable annular ring which, using rotational aerodynamics to provide good forward flight performance without need for a tail rotor. A model helicopter 'body' is suspended beneath the ring, and uses airflow to stabilise itself in the direction of flight, much like a weather vane. The papercopter design permits flights of approximately 10–14 meters on average. Paper helicopters (autogyros) The world's first known published paper autogyro (engineless helicopter) by Richard K Neu appeared in "The Great International Paper Airplane Book" published in 1967. Its wings fly in a circle around a central ballast shaft as it descends vertically. This basic design has been published several times and is widely known. The world's first known published forward-gliding paper autogyro with forward-pointing body lifted by spinning blades was built by James Zongker. It appears on page 53 of "The Paper Airplane Book: The Official Book of the Second Great International Paper Airplane Contest" published in 1985 by Science Magazine. Its twin contra-rotating blades automatically spin on paper axles upon launch to provide lift. As noted above (see entry, Paper Pilot), E.H. Mathews developed a flight-stable paper model helicopter. This has a ring wing, and flaps for adjusting for flight for stability, positioned on the inboard edge of the ring. While not an autogyro per se, this paper model aircraft class falls within the general design of a paper