A STUDY OF A PILOT'S ABILITY TO CONTROL DURING SIMULATED STABILITY AUGMENTATION SYSTEM FAILURES

APPENDIX A TIME-VARIABLE _ DYNAMICS In this section, someof the results of reference 8 are recast in a somewhatdifferent form to relate them to results in the present paper.

The study conducted in reference 8 is also considered pertinent to the present investigation because it represents an initial and interesting effort to determine directly the time-variable adaptive behavior of humancontrollers. The experiment consisted of measuring changes in the closed-loop, human-operator dynamics associated with changes in display, process, or "vehicle" dynamics_ etc. The experiments were performed with a tracking task similar to that used in the present study. The subject sat in front of a cathode-ray oscilloscope on which was displayed either task input and vehicle response (pursuit display), or only the error (compensatory display). The subject was instructed to manipulate a small controller to minimize the error.

Results are presented in reference 8 showing the changes in closed- loop humandynamics (average of eight subjects) that occurred as the vehicle dynamics were changedfrom unit gain (Yc = i) to pure integration (Yc = 1.61/s) and vice versa for both compensatory and pursuit displays.

The change in vehicle dynamics was generally completed within 6 seconds of the start of the change. Analysis of the average closed-loop operator dynamics Yp/I+YpYc during the change in vehicle dynamics from unit gain to pure integration with a compensatory display revealed somewhatthe samepattern of adaptation to SASfailures observed in the present study.

Specifically, time histories of average tracking error (fig. 16) deduced from the results given in reference 8 are fairly similar to the results obtained in the present study (e.g., fig. 2(b)). It was necessary to determine the error indirectly from the over-all system transfer function YpYc/l+YpYc, since the total tracking-error results are not provided in reference 8. The time-variable results (60 to 120 seconds, fig. 16) are shown dotted because they are determined from data which are inherently less precise than the time-invariant results (see ref. 8). The deduced tracking error (fig. 16) shows that adaptation occurred within about 15 to 30 seconds of the start of the change in dynamics. As indicated in figure 16, the mean-squarederror increased about five-fold as the vehi- cle dynamics changed from unit gain to pure integration. The associated open-loop humantransfer function (fig. 17) indicate that the subjects reduced both gain and phsse lag appreciably as they adapted to the change in vehicle dynamics.

APPENDIX B

TIME-INVARIANT PILOT MODEL CHARACTERISTICS

A summary of pilot-model characteristics_ taken from reference i,

is reproduced in figure 18. These results show the time-invariant, pilot

response characteristics (determined by the performance-matching technique

described in ref. i) for the wide range of vehicle longitudinal short-

period dynamics covered in the reference I study. Also provided in fig-

ure 18 (dashed lines) are the changes in gain and lead required for the

pilot to adapt to the various simulated SAS failures considered in the

present study. These results show that the damper failures at high short-

period frequencies (cases A and B) required primarily a reduction in gain

Kp. Damper failure at low short-period frequency (case C) required a

simultaneous reduction in gain and a large increase in lead. For the two

cases involving failures of static stability augmenters, a simultaneous

reduction in gain and increase in lead was required for case D, while case

E required primarily an increase in lead.

REFERENCES

l• Sadoff, Melvin, McFadden, Norman M., and Heinle, Donovan R.: A

Study of Longitudinal Control Problems at Low and Negative Damping

and Stability With Emphasis on Effects of Motion Cues. NASA

TN D-348, 1961.

McFadden, Norman M., Vomaske, Richard F., and Heinle, Donovan R.:

Flight Investigation Using Variable-Stability Airplanes of Minimum

Stability Requirements for High-Speed, High-Altitude Vehicles.

NASA TN D-779, 1961.

McNeill, Walter E., and Vomaske, Richard F.: A Flight Investigation

To Determine the Lateral Oscillatory Damping Acceptable for an

Airplane in the Landing Approach. NASAMEMO 12-I0-58A, 1959.

_Jr.

Creer, Brent Y., Stewart, John D., Merrick, Robert B., and Drinkwater,

Fred J., III: A Pilot Opinion Study of Lateral Control Requirements

for Fighter-Type Aircraft. NASA MEMO 1-29-59A, 1959.

. Vomaske, Richard F., Sadoff, Melvin, and Drinkwater, Fred J., III:

The Effect of Lateral-Directional Control Coupling on Pilot Control

of an Airplane as Determined in Flight and in a Fixed-Base Flight

Simulator. NASA TN D-If41, 1961.

.

Creer, Brent Y., Heinle, Donovan R., and Wingrove, Rodney C.: Study

of Stability and Control Characteristics of Atmosphere-Entry Type

Aircraft Through Use of Piloted Flight Simulators. Paper No. 59-129, Inst. Aero. Sci., 1999.

. Hall, lan A.M.: Effects of Controlled Element on the Human Pilot.

WADC Tech. Rep. 57-509, Aug. 1958 .

•

Sheridan, Thomas B.: Time Variable Dynamics of Human Operator

Systems. AFCRC-TN-60-169, March 1960.

9. Sadoff, Melvin: The Effects of Longitudinal Control-System Dynamics

on Pilot Opinion and Response Characteristics as Determined From

Flight Tests and From Ground Simulator Studies. NASA MEM0 I0-I-58A, 1958.

i0. Ashkenas, Irving L., and McRuer, Duane T.: The Determination of

Lateral Handling Quality Requirements From Airframe-Human Pilot

System Studies. WADC TR 59-135, June 1959•

ii.

McRuer, Duane T., Ashkenas, Irving L., and Guerre, C. L.: A Systems

Analysis View of Longitudinal Flying Qualities. WADD TR 60-43, Jan. 1960.

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NASA-Langley, 1962 A-703