The first known discussion of the computer method of flight simulation
is that of Roeder in his 1929 German Patent Specification. Roeder treated the
general problem of the instrument control of vehicles freely movable in space,
such as airships, aeroplanes or submarines. His outlines of the requirements of a
simulator for such a task could almost refer to a modern simulator. As an
example of his technique he described the dynamic simulation of an airship height
control system and a fluid-operated analogue computer suitable for this. No
successful training devices are known to have resulted from this work. In 1939
Mueller, at MIT, described an electronic analogue computer for the faster-than-
real-time simulation of aeroplane longitudinal dynamics. His interest was in
aircraft design and the solution of the equations of motion, but as a postscript
to his paper he mentioned the possibility of extending the time scale of the
simulation and of including a man in the loop.
In 1941 an electronic simulator was designed and built at the TRE to
serve as the "flying unit" for their AI radar trainers. This computer was based
on the ideas of F.C. Williams, famous for his later work on digital computers,
and used the velodyne, another TRE invention, for integration. The d.c. method
of computing was used in the simulation of the simplified fighter aerodynamics.
The first model of this computer (the Type 8 Part II) was constructed by Dynatron
Radio Limited in 1941 and many were used throughout the war. Later, in 1945, a
more advanced flying unit including feel forces was designed by A.M. Uttley for
use in a new AI visual crew trainer. This, however, never saw service.
Also in Britain at about this time an electromechanical analogue
computer for the simulation of aircraft longitudinal dynamics was proposed by
G.M. Hellings, then working at the Ministry of Supply. Non-linear functions were
generated with shaped cams, and it was sufficiently general to allow the
characteristics of any chosen aircraft type to be represented. A mechanical
version of this device, the Day Landing Trainer, was manufactured by General
Aircraft Limited and used at the Empire Central Flying School. This trainer
simulated longitudinal motions and had a pitch motion system with an endless
belt, directly viewed visual model. Further development of the device was carried
out after the war at Air Trainers Limited.
In 1941 Commander Luis de Florez, of the U.S. Navy, visited Britain
and wrote his "Report on British Synthetic Training". This report was highly
significant and influenced the establishing of the Special Devices Division of
the Bureau of Aeronautics, the predecessor of the present Naval Training
Equipment Center. Also in this year the Silloth Trainer concept was brought to
the United States and one was erected at the Mohier Organ Plant at Hagerstown,
Maryland. After evaluation it was decided to build an electrical version of the
trainer as instability of adjustments due to humidity, temperature and ageing
made the system unmanageable. The task of producing the new trainer was given to
Bell Telephone Laboratories who produced an operational flight trainer for the
Navy's PBM-3 aircraft. This device, completed in 1943, consisted of a replica of
the PBM front fuselage and cockpit, complete with controls, instrumentation and
all auxiliary equipment, together with an electronic computing device to solve
the flight equations. The simulator had no motion system, visual system or
variable control loading. A total of 32 of these electronic flight trainers for
seven types of aeroplane were built by Bell and the Western Electric Company
during the war years. It has been stated that the PBM-3 was "probably the first
operational flight trainer that attempted to simulate the aerodynamic
characteristics of a specific aircraft" but this is debatable.
Since the development of his electrical instrument flight trainer Dr.
Dehmel had gained experience in analogue computing techniques through his work on
Bell's M-9 anti-aircraft gun directors. He applied this knowledge to the design
of an instrument flight simulator based on an analogue computer. He was then able
to interest the Curtiss Wright Corporation in the manufacture of these devices in
1943. After the development of a prototype trainer, the U.S. Air Force ordered
two trainers from Curtiss Wright for the AT-6 aeroplane; this trainer was named
the Z-1 and is shown in the photo. These were followed by production examples
designated the Z-2, -3 and -4.