While watching the recent movie Sully, I was amazed at the sophistication of current flight simulators available to the major aircraft producers. During the course of this blog, we will trace the development of flight simulators from mere mechanical devices to the virtual reality electronics of today.
A flight simulator is a mechanical or electronic device, which attempts to duplicate both aircraft flight and the environment in which it flies. Current simulators can replicate factors such as flight controls, wind, moisture and electronic system interaction. While flight simulation is used primarily for pilot training, it may also be used to design aircraft, as well as identify effects of aircraft properties.
The earliest flight simulators were used during World War I to teach gunnery techniques. This involved a static simulator with a model aircraft passing in front to aid both pilots and gunners to develop correct lead angles to the target. This was the only form of flight simulation for nearly ten years. The Link Trainer, developed by Edwin Link in the late 1920′s, capitalized on the use of pneumatic devices from player pianos and organs from the family musical instrument business. The first trainer was patented in 1930 with an electrical suction pump boosting the various control valves operated by stick and rudder action while another motor simulated the effects of wind and other external disturbances. These actions could be manually adjusted to provide a variety of flight characteristics.
While the Link Trainer provided a quantum leap in capability over previous flight simulators, many in both the military and civil aviation communities believed the live flight experience offered a better training environment. However, by the early 1930′s, the United States Army Air Corps had a need for flight simulator applications which could train mail pilots to fly by instruments for long distances. An enhancement to the Link Trainer was a device called the course plotter, in which a self-propelled tracker could remotely trace the trainer position from an inked wheel with communications between pilot and instructor facilitated by the use of simulated radio beacons.
It was during the late 1930′s, when flight simulation began to be based on electronic applications. The Dehmel Trainer, developed by Dr. R. C. Dehmel of Southwestern Bell, coupled a Link Trainer with an advanced radio simulation system, which could accurately duplicate navigation signals transmitted to a receiving aircraft, providing a state of art simulation of radio navigation aids. The Aerostructor, developed by A. E. Travis, utilized a fixed base trainer with a moving visual presentation, as opposed to radio and electronic signals. This presentation was based on a loop of film which depicted the effects of course changes, pitch and roll. While the Aerostructor was never mass produced, a modified version of it was in service with the US Navy.
During World War II advances in aircraft design such as retractable landing gear, variable pitch propellers and higher speeds created a demand for more realistic forms of flight simulation. In response to this, the Hawarden Trainer was developed, which used a cutaway center section of a Spitfire fuselage, which allowed training in all aspects of operational flight. In 1939, the British were in need of a simulator which could train it’s navigators who were ferrying US aircraft across the Atlantic. The navigator was supported by a number of radio aids, as well as a celestial dome corresponding to changes in the position of the stars relative to changes in time, longitude and latitude. The Celestial Trainer, designed by Ed Link and P. Weems was also modified to train bomber crews, in which simulated landscapes gave the bomb aimer target sightings as they would appear from a moving aircraft. Redifussion (Redifon) produced a navigation device in 1940, which simulated existing radio direction equipment allowing two stations to take a fix on an aircraft’s position. By the end of the war, aircraft crews were trained by the simulation of radar signals to acquaint them with new types of radar developed during the war.
While the science of flight simulation had progressed dramatically over the past thirty years, they were unable to accurately duplicate performance characteristics of a plane. This changed with the arrival of subsonic jetliners in the 1950′s. Aircraft manufacturers began to produce more complete data and extensive flight testing. This data was stored on analogue computers, making the data transferable, but requiring more hardware as aircraft testing became more sophisticated. By the early 1960′s, digital computers began to replace the aging analogue units due to the increased data capacity and speed of the digital units. The most successful of these, the Link Mark I, operated with three parallel processors functional, arithmetic and radio selection, using a drum memory for data storage. By the 1970′s the majority of computer systems could be adapted for flight simulation.
During that decade computer image generation or CGI technology became available for flight simulation models. This technology, adapted from the space program, used a ground plane image, supplemented by three dimensional graphics. This technology became more sophisticated in recent years, mating it to advances in digital computers – a far cry from the rolling ground plane pictures of the 1940′s. Today, flight simulation is a colossal industry, spanning the globe with a wide range of high tech applications for both aircraft users and producers, enhancing the safety of both crew and passengers.