From the beginning of mankind, we have looked to the skies where legends and myths have entertained and provided us the dream to fly. Through the middle ages, the idea of flight evolved across Europe, with Leonardo Da Vinci well known for designing flying machines to carry humans. In 1874, Otto Lilienthal, a German mechanical engineer, started designing, building, and flying bird-like wings. [Figure 1-1] He published his work in 1889, and by 1891 made flights of over 100 feet in distance. Otto was the first successful hang glider pilot to design, build, and fly a number of wing designs. [Figure 1-2]
In 1903, the Wright brothers’ gliders became powered and the airplane was born as the Wright Flyer. In the early 1900s, aircraft configurations evolved as faster speeds and heavier loads were placed on aircraft in flight. As a result of the new demands, the simple flexible wing was no longer sufficient and aircraft designers began to incorporate rigid wings with mechanical aerodynamic controls. These new ideas in wing design eventually resulted in the familiar aileron and rudder configurations found on the modern airplane.
Commercial applications were driving the need for faster and heavier aircraft; however, the dream of achieving manned powered flight in its most bird-like form was evolving along a different path. As rigid wing design enjoyed development for military and commercial applications, the flexible wing concept lay largely dormant for decades. In 1948, a flexible wing design was created by Francis Melvin Rogallo as a flying toy kit for which he obtained a patent in 1951. [Figure 1-3]
Rogallo’s design concept evolved down two parallel paths in the early 1960s, military and sport flight. The military application was the National Aeronautics and Space Administration (NASA) development of the Rogallo wing into the Paresev (Paraglider Research Vehicle) later renamed the Parawing. That aircraft had rigid leading edges shown in Figure 1-4. NASA had the cart attached to the keel hanging below the wing and using weight shift to control the wing in the same fashion as modern WSC aircraft today.
During this same period, other pioneering engineers and enthusiasts started developing the Rogallo wing for sport. One was aeronautical engineer, Barry Palmer, who saw pictures of the NASA wings and, in 1961, constructed and flew a number of hang gliders based on the Rogallo design. [Figure 1-5] His efforts and others evolved to the WSC aircraft in the late 1960s. Another pioneer was John Dickenson of Australia who used the NASA Rogallo wing design but incorporated a triangular control bar that provided structure for the wing during flight with flying wires. [Figure 1-6]
The WSC system and the good flying qualities of the Rogallo wing and Dickenson wing, combined with its easy set-up and portability, started the hang gliding craze in the early 1970s. [Figure 1-7] In 1967, the first powered aircraft based on the flexible wing concept of Dr. Rogallo was registered as amateur-built experimental. Flexible wing development continued, and by the early 1970s several adventurous entrepreneurs were manufacturing Rogallo wings for sport use.
Another significant step in wing design was an airfoil that would change shape for optimum performance at slow and fast speeds. It was the first Rogallo wing with a lower surface that could enclose the structure that holds the wings out. Enclosing this crossbar tube and providing a thicker airfoil similar to the airplane wing provided a jump in high-speed performance. This double-surface wing was quickly adopted by manufacturers as the high-performance standard and is used on faster WSC aircraft today. [Figure 1-8]
Activity in the hang gliding community increased throughout the 1970s, which resulted in the proliferation and development of stable, high-quality modern hang gliders like the one shown in Figure 1-9.
Motorized Hang Gliders
In the late 1970s, performance had increased enough to allow motors to be added to hang gliders and flown practically. It was not until the wings had become efficient and the engines and propeller systems evolved that the first commercial motor for a hang glider was introduced in 1977, the Soarmaster. It used a two-stroke engine with a reduction system, clutch, and long drive-shaft that bolted to the wing frame. It had a climb rate as high as 200 feet per minute (fpm) which was acceptable for practical flight. However, during takeoff the wing would overtake the running pilot, and launching was very difficult. Also while flying, if the pilot went weightless or stalled under power, the glider would shoot forward and nose down into a dive. Overall, with the propeller pushing the wing forward during takeoffs and in some situations while flying, this was unsafe for a wide application. [Figure 1-10]
A Maturing Industry
Engines and airframe technology had made great advances because the ultralight fixed-wing evolution was providing lighter weight, higher power, and more reliable propulsion systems.
The propeller was moved lower for better takeoff and flight characteristics, wheels were added, and the trike was born at the end of the 1970s. A trike describes a Rogallo type wing with a three-wheeled carriage underneath (much like a tricycle arrangement with one wheel in front and two in back). Trike is the industry term to describe both ultralight vehicles and Light-Sport Aircraft (LSA) WSC aircraft. [Figure 1-11] The major trike manufacturers were formed in the early 1980s and continue to deliver trikes worldwide today.
By the 1980s, individuals were rapidly developing and operating small powered trikes. This development failed to address the sport nature and unique challenges these new aircraft presented to the aviation community. In an attempt to include these flying machines in its regulatory framework, the FAA issued Title 14 of the Code of Federal Regulations (14 CFR) part 103, Ultralight Vehicles, in 1982. Aircraft falling within the ultralight vehicle specifications are lightweight (less than 254 pounds if powered, or 155 pounds if unpowered), are intended for manned operation by a single occupant, have a fuel capacity of five gallons or less, a maximum calibrated airspeed of not more than 55 knots, and a maximum stall speed of not more than 24 knots. Ultralight vehicles do not require pilot licensing, medical certification, or aircraft registration. Ultralight vehicles are defined in more detail with their operating limitations in 14 CFR part 103.
Because training was so important for the single-place ultralight vehicle pilots, the FAA granted an exemption that allowed the use of two-seat ultralight vehicles for training, and the sport of two-seat ultralight training vehicles grew. Throughout the 1990s, worldwide sales of both single-seat and two-seat ultralight vehicles soared, but it was the proliferation of two-seat trainers that took the industry and the regulators by surprise. Worldwide sales of two-seat ultralight vehicle trainers vastly outnumbered the sales of single-seat ultralight vehicles; and it became clear that the two-seat trainers, which were intended to be operated as trainers only, were being used for sport and recreational purposes. This created a demand for increased comfort and reliability, which resulted in heavier, more sophisticated machines.