Tuesday 11th November 2014
‘Development of Flight Simulators’ by Mr David Parkinson, C.Eng, FRAeS.
David joined what was then Link-Miles in Lancing in 1972, and rose to become Director of Research & Development. He is now an independent consultant. His illustrated talk covered early flight simulators (using wood and real manpower) up to the present day, and touched on other vehicles such as tanks and submarines.”
Early Simulators: The first known flight simulation device was developed in 1909 to help pilots fly the Antoinette Monoplane. This consisted of a seat mounted in a half-barrel and two wheels which controlled pitch and yaw. The whole unit was pivoted so that assistants outside could move the device in accordance with the pilot’s use of the wheels, using long wooden rods attached to the barrel structure.
A number of pilot training devices were developed during World War I for teaching pilots how to operate the flight controls. Some ground-based simulators were also developed to train pilots in air gunnery.
The best-known early flight simulation device was the Link Trainer, produced in 1929. The Link Trainer had a pneumatic motion platform driven by inflatable bellows which provided pitch and roll cues. An electric motor rotated the platform, providing yaw cues. A generic replica cockpit with working instruments was mounted on the motion platform. By covering the cockpit, pilots could practice flying by instruments. The motion platform gave the pilot cues as to real angular motion in pitch (nose up and down), roll (wing up or down) and yaw (nose left and right).
World War 11 Simulators: The Link Trainer was the principal pilot trainer used during World War II, however other ground-based flight training devices were produced. For instance, in 1943 a fixed-base aircraft-specific trainer for the British Halifax bomber was produced at the RAF Station at Silloth (the “Silloth Trainer”) in the north of England. This consisted of a mock-up of the front fuselage of the Halifax, the pilot’s flight controls being simulated through an analogue system that gave artificial resistance (“feel”) when the pilot moved the controls.
A trainer was also developed used for night navigation. The Celestial Navigation Trainer of 1941 was 13.7 m (45 ft) high and capable of accommodating the navigation team of a bomber crew. It enabled sextants to be used for taking “star shots” from a projected display of the night sky.
1945 to the 1960s: In 1948, Curtiss-Wright developed a trainer for the Boeing 377 Stratocruiser. This was the first complete aircraft-specific cockpit trainer owned by an airline. There was no motion or visual system, but the cockpit was closely replicated and the controls functioned and produced responses on the cockpit instruments. The device provided training to flight crews in checks, drills and basic flight procedure.
With the advent of jet airliners such as the UK Comet and U.S. Boeing 707 and DC-8, simulators were produced to train for checks and drills, and to avoid using the actual aircraft for familiarization exercises that could be carried out in the simulator. An example was the simulator for the Comet 4 produced by the Redifon Company of Aylesbury, UK. This had a three-axis motion platform on which the forward section of a Comet fuselage was mounted.
The use of digital computers also began in the 1960s. Originally these were from specialist high-end computer manufacturers but with the increasing power of the PC, arrays of high-end PCs are now also used as the primary computing medium in flight simulators.
Motion systems: The motion system in the 1929 Link Trainer design gave movements in pitch, roll and yaw. Further development found that six jacks in the appropriate layout could produce all six degrees of freedom that are possible for a body that can freely move. These are the three angular rotations pitch, roll, and yaw, and the three linear movements heave (up and down), sway (side to side), and surge (fore and aft).
Visual Display Systems: Early visual systems used a small physical terrain model, normally called a “model board”. A miniature camera was moved over the model terrain in accordance with the pilot’s control movements. The resultant image was then displayed to the crew, generally used TV screens or projected displays in front of the replica cockpit to display the Out-The-Window (OTW) visual scene. Only limited geographical areas could be simulated in this manner, and for civil flight, simulators were usually limited to the immediate vicinity of an airport or airports. In military flight simulators, as well as at airfields, model boards were produced for larger areas that included terrain for practicing low flying and attacking targets.
Several developments improved the visual systems such that single-pilot trainers would typically have three display units (center, left and right), giving a field-of-view of about 100 degrees horizontally and between 25 and 30 degrees vertically.
Modern simulators use digital image generation systems combined with mirror-based cross-cockpit (for pilot and co-pilot) displays. Using five projectors a field-of-view of 240 degrees horizontally and 30 degrees vertically can be obtained.
Modern Simulators: High-end commercial and military flight simulators have high-resolution image generation and large field-of-view (FoV) display systems. Most motion platforms use variants of the six-jack Stewart platform for cues of initial acceleration. These are also known as Hexapods (literally “six feet”). Modern hexapod platforms can provide about +/- 35 degrees of the three rotations pitch, roll and yaw, and about one metre of the three linear movements heave, sway and surge.
Flight simulation is used extensively in the aviation industry to train pilots and other flight crew for both civil and military aircraft, particularly in flight dynamics and man-machine interaction (MMI). It is also used to train maintenance engineers in aircraft systems, and has applications in aircraft design and development, in aviation, and in other fields of research. Simulators are also used extensively in accident investigations.
David showed two video clips to demonstrate how ‘real’ modern simulators are. He showed two flights of RAF fast jets flying overland. One was a cockpit display of a real flight, the other a view from a simulator. I found it difficult to tell which was which!!