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dynamics
Aircraft
model
Motion
system
Visual
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Figure 1. Flight versus simulation.
The Case Against Platform Motion. Cardullo
cites many of the reasons users either do not employ
motion or believe it is unnecessary (ref. 9). First,
platform motion usually does not have the face validity
that a simulation component such as the visual system
does. Face validity is defined as a seamless one-to-one
correspondence with the real world. Some subsequently
argue that since the true motion environment cannot be
duplicated faithfully, a subset of it should not be
presented, for the cues are incorrect. It is also argued that
providing platform motion is not cost effective. Finally,
opponents of motion note that transfer-of-training studies
have found no basis for a motion requirement. In
particular, the U.S. Air Force’s
standard view for training is that motion is not required in
the simulation of any aircraft with centerline thrust.
Roscoe (ref. 10) states that “Complex cockpit motion,
whether slightly beneficial or detrimental on
balance . . . has so little effect on training transfer that
its contribution is difficult to measure at all.” The two
studies most often cited showing that motion did not have
a training benefit for several tasks are those by Waters
et al. (ref. 11) and Gray and Fuller (ref. 12). However,
Cardullo points out that these two studies have largely
been discredited because of the poor experimental
apparatus used in each study (ref. 9). In particular, the
motion systems had large motion platform delays.
5
Boldovici (ref. 8), in an extensive review for the U.S.
Army, presents several reasons for not using motion
platforms: (1) the absence of supporting research results,
(2) possible learning of unsafe behavior based on incorrect
platform cueing, (3) achievement of greater training
transfer by means other than motion cueing, (4) undesirable
effects of poor motion synchronization, (5) direct,
indirect, and hidden costs, (6) alternatives to motion bases
for producing motion cueing (e.g., g-seats, pressure suits),
and (7) benign force environments.
Poor motion synchronization, which does not have a
precise definition, has caused some pilots to experience
simulator sickness. This discomfort affects both the
pilot’s performance and his acceptance of a simulator.
Surprisingly the discomfort can last, or even develop,
hours after the simulator session. The U.S. Navy has
recommended that motion bases be turned off if sickness
develops; however, that recommendation notes that some
crews also become sick in the actual vehicle (ref. 13).
Some branches of the armed services require a waiting
period between a simulator session and flight.
Finally, several researchers have defined tasks for which
motion does not seem to add benefit. Hunter et al.
(ref. 14) and Puig et al. (ref. 15) indicate that motion
does not seem to be very beneficial for tasks in which the
pilot creates his own motion. Such instances would be for
tracking tasks in a disturbance-free environment.
The Case For Platform Motion. Hall attempts to
determine when platform motion is and is not important
(ref. 16). He contends that non-visual cues are of little
importance for primarily open-loop, low pilot-vehicle
gain, low workload maneuvers with strong visual cues.
However, he also states that motion cues are more
important when the pilot workload increases, when the
pilot-vehicle gain rises, or when the vehicle stability
degrades. The latter certainly occurs in helicopter
simulation.
Showalter and Parris conducted a study in which pilots had
to recover from an engine-out during takeoff in a KC-135
aircraft (ref. 17). They showed that the addition of motion
significantly reduced the amount of yaw activity during an
engine-out when compared to the no-motion case. In the
same study, they also showed that the addition of motion
affected inexperienced pilots’ ability to perform precision
rolling maneuvers, but that the addition of motion had no
significant effect on experienced pilots for the same task.
Young showed that platform motion reduced the pilot’s
response time to a failure or disturbance while on a glide
path compared to the no-motion case (ref. 18). In the same
paper, results were presented showing that when helicopter
pilots and highly trained non-pilots hovered an
unaugmented helicopter model, their performance significantly
improved with the addition of motion. Performance
did not improve for the moderately trained non-pilots.
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Helicopter Flight Simulation Motion Platform Requirements(5)
