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0 000. .
1 000
c
The collective position δ c and pedal position δ r are in inches. The variable z1 was an additional state added to approximate the effects of dynamic inflow (ref. 51). All other vehicle states were kinematically related to the above dynamics. So, in effect, the vehicle c.m. was constrained to remain on a vertical axis fixed with respect to Earth for all tasks. Although the tail rotor in an actual helicopter
produces both a side force and a moment about the c.m., only the moment was represented in this experiment, a result of the fixed c.m. These vehicle constraints were introduced to simplify the number of motion sensations that had to be interpreted by the pilot. In addition, no coordination of the gravity vector was required, for it remained fixed relative to the pilot. No atmospheric turbulence was present in any of the tasks. The collective lever was used for Task 3 only.
The pilot was located 4.5 ft forward of the c.m., which represents the AH-64 pilot location. Thus for this case,
ψ
math model rotational accelerations were accompanied by lateral translational accelerations at the pilot’s station, and rotational rates were accompanied by longitudinal accel-erations at the pilot’s station. Specifically, the accelera-tions at the pilot’s station in this experiment were as follows:
˙
2
of the math model. These cues represented the pilot’s physical offset of 4.5 ft forward of the vehicle’s c.m.
Conventional pedals and a left-hand collective lever were used. The pedals had a travel of ±2.7 in, a breakout force of 3.0 lb, a force gradient of 3 lb/in, and a damping ratio of 0.5. The collective had a travel of ±5 in, no force gradient, and the friction was adjustable by the pilot.
All cockpit instruments were disabled, which made the visual scene and motion system cues the only primary cues available to the pilot. Rotor and transmission noises were present to mask the motion-system noise. Six NASA Ames test pilots participated in Task 1, and five of the same six participated in Tasks 2 and 3. All pilots had extensive rotorcraft flight and simulation experience.
Motion System Configurations
(6) Four motion-system configurations were examined for
ψ
ψ
=.45. ˙˙˙˙
each of three tasks: (1) translational and rotational
=45.
(7)
ψ
ayp ˙˙
p
motion, (2) translational without rotational motion,
(3) rotational without translational motion, and (4) no
motion. Figure 11 illustrates, in a plan view, the
(8)
=
where the subscript p refers to the pilot’s station.
Simulator and Cockpit
The Vertical Motion Simulator, described in section 2, was used. The mainframe-computer cycle time was 25 msec. The Evans and Sutherland CT5A visual system provided the visual cues, and it had a math-model-to-visual-image-generation delay of 86 msec (ref. 52). This delay is typical of today’s flight simulators. The visual field of view is shown in figure 10. The visual cues simulator cab motion for these configurations for Task 1, which was the ±15° heading turns. In the Translation+ Rotation case, the cab translates and rotates as if it were placed on the end of a 4.5-ft vector rotating in the horizontal plane. This case represented physical reality, or the truth case. In the Translational case, the pilot always points in the same direction, as the cab translates in x and y. In the Rotation case, the cab rotates but does not translate. Finally, in the Motionless case, the cab does not move.
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