After the war, competition from Curtiss-Wright stimulated Link to develop their own electronic simulators. Also at this time the value of the Link Trainer motion system was being called into question. The movements of the Link Trainer did not correctly simulate the forces experienced in flight, and in fact a ground-fixed trainer would more accurately locate the force vector in coordianted turning or level flight. Also, the axis of roll rotation was too far below the pilot to allow correct simulation of accelerations due to roll. It was argued that the modern pilot should not fly "by the seat of his pants", but by instruments. Ed Link disagreed and held the view that trainer motion was needed even if incorrect, since motion was present in flying. However, customer pressure caused Link to follow the trend to fixed base simulators. The company therefore developed their own electronic analogue computer which was used in their C-ll jet trainer. A contract was awarded by the U.S. Air Force in 1949, and eventually over a thousand of these types were sold.


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Meanwhile, Curtiss-Wright had contracted to develop a full simulator for the Boeing 377 Stratocruisers of Pan American Airways. The simulator was installed in 1948 and was the first full aircraft simulator to be owned by an airline. No motion or visual system were installed, but in all other respects the simulator duplicated the appearance and behaviour of the Stratocruiser cockpit. The trainer was found especially useful for the practice of procedures involving the whole crew; emergency conditions could be readily introduced by the instructor on his fault insertion panel. Complete routes could be flown, as in real life, using the same navigational aids. This facility was used by other airlines, and in the words of a BOAC Captain, "From start to finish we had treated the whole exercise as if it were the real thing, and the cockpit was so complete in every detail that we soon forgot that we were not in an aeroplane'' However, there were some reservations expressed about the lack of motion in a fixed-base simulation, which caused it to feel unnatural and could even cause control problems.


In 1947 B0AC decided to buy Boeing 377 Stratocruisers, and knowing of Redifon's work on synthetic crew trainers, asked Mr Adorian if a simulator could be built for this aircraft; the simulator was to be the same as that which Curtiss-Wright were building for Pan American. In order to comply with the BOAC requirement Redifon had to enter into an agreement with Curtiss-Wright and Dr. Dehmel and obtain clearance from the U.S. State Department. Work commenced on the construction of the simulator at Redifons Wandsworth works in January 1950. The computation was analogue, using 60Hz (U.S. mains frequency) signals and servo motors, contoured potentiometers and 400Hz synchros and magnesyns for aircraft instrument drives. The control loading unit used variable levers, servo controlled as a correctly computed function of air speed, with springs to produce the necessary forces. The unit took the form of a separate frame running the whole length of the fuselage and, as today, carried the flying controls, throttle pedestal and pilot's panels and seats. The simulator was finally accepted in October 1951 with the price to BOAC being 120,000.


Prior to the final acceptance of the Stratocruiser, BOAC gave another simulator order to Redifon, this time for a Comet I. This was to become the first jet transport simulator in the world, and was designed by A.E. Cutler. Whereas the first simulator's servos had been manufactured by Curtiss, the Comet servos and potentiometers were built by Redifon. This second simulator followed similar principles to that of the first, except that a carrier frequency of 50Hz was employed and no computed control loading was necessary as the aircraft used a fixed spring-loaded control system.


The first Curtiss-Wright, Redifon and Link simulators used the a.c. carrier method of analogue computer. Air Trainers Limited however, decided to use the d.c. method - a more demanding technology, but one capable of superior precision in simulation. Their first simulator using this technology was built for the RAF's Meteor aircraft. The d.c. method was later adopted by Link in the United States. Redifon, however, developed a system using a carrier frequency of 400Hz which was very successful. Also, at this time, mechanical analogue computers were constructed for use in the simpler "type trainers" by Air Trainers Limited.



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