Kennedy's Design-Induced Spiral

Flight experiments support the conclusion that John Kennedy, Jr. became spatially disoriented in the absence of a visible horizon in conditions of poor visibility. The overwhelming probability is that he wound up in what is known by pilots as a "graveyard spiral." That is exactly what 19 of 20 similarly trained pilots did with the loss of a visible horizon in an experiment at the University of Illinois 45 years ago (Bryan, Stonecipher, & Aron, 1954).

Later experiments at Illinois have shown that a simple addition to the conventional "artificial horizon" indicator on the instrument panel can virtually eliminate this type of accident, one that kills many people every year in general aviation and can even occur in commercial aviation (Roscoe, 1997). For the aviation community to correct this situation, someone in the media has to expose the problem, someone in government has to listen, and someone important has to die.

In conditions of poor visibility, inexperienced pilots get into screaming spiral dives in several ways, but this is the most common: While the pilot is looking for lights on the ground or other horizon reference, the airplane slowly rolls into a banked attitude. With no horizon visible, the pilot looks at the "artificial horizon" indicator in the cockpit and notices that the horizon bar is not level. The initial reaction is to roll the horizon bar back to level, which rolls the airplane into a steeper bank. This is known as a horizon control reversal.

In a steep bank, the nose of the airplane drops, and it starts to lose altitude. To hold altitude the pilot pulls back on the wheel, which tightens the turn and steepens the spiral dive. At this point the pilot is confused. totally disoriented, and no longer in control of the airplane. Such a sequence can and does happen very rapidly, and the resulting crash is invariably attributed to pilot error. No doubt the pilot made the error, but what caused the error is never determined nor the probable cause reported.

The term "pilot error" is misused when such errors can be prevented by an experimentally proven equipment modification. In the case of flight attitude control, all that is needed is to cause the "little airplane" symbol on the artificial horizon indicator to rotate in direct response to aileron control inputs. Thus, to return to a wings-level attitude, the pilot merely has to align the airplane symbol with the displaced horizon bar and maintain that alignment as the real airplane and the artificial horizon bar, rotating in opposite directions, both return to wings-level.

To illustrate, if the airplane rolls to the right, the horizon bar rolls left. The pilot notices this and applies left aileron to align the airplane symbol with the horizon bar, causing the plane to start rolling back toward wings level. As this is going on, the pilot gradually reduces the left aileron input to maintain alignment until the ailerons are neutral when the wings are level. Thus, straight-ahead flight is restored.

Attitude Indicators: What moves? The three display modes all indicate a bank to the right. The left indicator is rotated counterclockwise. In the center indicator, the airplane symbol is rotated clockwise. In the right indicator, the horizon is the same as on the left, but in addition the airplane symbol is rotated clockwise by the pilot's aileron input, indicating that the plane will continue to roll to the right. The instrument represented on the left is the standard system in today's airplanes including John Kennedy's Piper Saratoga II. With the display at the right, pilots maintain wings-level flight merely by aligning the airplane symbol with the horizon, a natural response. Click here for a 17-second animation. Flash Player required.

Bryan, L. A., Stonecipher, J. W., & Aron, K. (1954).180-degree turn experiment. University of Illinois Bulletin, 54(11), 1-52.

Roscoe, S. N. (1997). Horizon control reversals and the graveyard spiral. CSERIAC Gateway, VII(3), 1-4. (Wright-Patterson Air Force Base, OH: Crew System Ergonomics Information Analysis Center.)

Roscoe, S. N. (1948). The effects of eliminating binocular and peripheral monocular visual cues upon airplane pilot performance in landing. Journal of Applied Psychology, 32, 649-662

Roscoe, S. N. (1951). Flight by periscope: I. Performing an instrument flight pattern; the influence of screen size and image magnification. University of Illinois Bulletin, 48(55; Aeronautics Bulletin 9).

Roscoe, S. N., Hasler, S. G., & Dougherty, D. J. (1966). Flight by periscope: Making takeoffs and landings; the influence of image magnification, practice, and various conditions of flight. Human Factors, 8, 13-40. [Original report in 1952 classified CONFIDENTIAL]

Nygaard, J. E. & Roscoe, S. N. (1953). Manual steering display studies: I. Display-control relationships and the configuration of the steering symbol (Tech. Memorandum 334). Culver City, CA: Hughes Aircraft Company.

Roscoe, S. N., Wilson, K. V., & Deming, H. C. (1954). Manual steering display studies: II. The transition of skilled interceptor pilots from the E-series to the moving airplane display (Tech. Memorandum 381). Culver City, CA: Hughes Aircraft Company.

Roscoe, S. N. (1957). The development of integrated instrument display panels at Hughes Aircraft Company. In M. L. Ritchie & C. A. Baker (Eds.), Psychological aspects of cockpit design-A symposium report (Tech. Report WADC 57-117; pp. 28-40). Wright-Patterson Air Force Base, OH: Wright Air Development Center.

Bauerschmidt, D. K., & Roscoe, S. N. (1960). A comparative evaluation of a pursuit moving-airplane steering display. IRE Transactions on Human Factors in Electronics, HFE-1(2), 62-66.

Roscoe, S. N., & Besco, R. O. (1963). An experimental evaluation of the Hughes predictive situation display for terrain following (Reference 2732.01/2). Culver City, CA: Hughes Aircraft Company, Display Systems Department.

Roscoe, S. N. (1968). Airborne displays for flight and navigation. Human Factors, 10, 321-332. [Also in M. Venturino (Ed.), Selected readings in human factors. Santa Monica, CA: Human Factors Society.]

Johnson, S. L., & Roscoe, S. N. (1972). What moves, the airplane or the world? Human Factors, 14, 107-129.

Jacobs, R. S., Williges, R. C., & Roscoe, S. N. (1973). Simulator motion as a factor in flight-director display evaluation. Human Factors, 15, 569-582.

Roscoe, S. N., & Williges, R. C. (1975). Motion relationships in aircraft attitude and guidance displays: A flight experiment. Human Factors, 17, 374-387.

Ince, F., Williges, R. C., & Roscoe, S. N. (1975). Aircraft simulator motion and the order of merit of flight attitude and steering guidance displays. Human Factors, 17, 388-400.

Beringer, D. B., Williges, R. C., & Roscoe, S. N. (1975). The transition of experienced pilots to a frequency-separated aircraft attitude display. Human Factors, 7, 401-414.

Roscoe, S. N., & Eisele, J. E. (1976). Integrated computer-generated cockpit displays. Proceedings of the NATO AGARD Symposium on Monitoring Behavior and Supervisory Control (pp. 22-32). Neuilly-sur-Seine, France: North Atlantic Treaty Organization; also in T. B. Sheridan & G. Johannsen (Eds.), Monitoring behavior and supervisory control (pp. 39-49). New York: Plenum.

Roscoe, S. N. (1980). Aviation psychology. Ames: The Iowa State University Press. [display motion relationships, pp. 68-81; display-control synthesis, pp. 82-94.]

Roscoe, S. N., & Jensen, R. S. (1981). Computer-animated predictive displays for microwave landing approaches. IEEE Transactions on Systems, Man, and Cybernetics, SMC-11, 760-765.

Roscoe, S. N., Corl, L., & Jensen, R. S. (1981). Flight display dynamics revisited. Human Factors, 23, 341-353.

Roscoe, S. N. (1983). 747 dives into Arabian Sea: Did a design-induced error cause the deaths of 210? Aviation Accident Investigator, 2(9), 1-3.

Roscoe, S. N. (1985). Frequency-separation: A third alternative in the outside-in/inside-out controversy. In G. B. McNaughton (Ed.), Aircraft Attitude Awareness Workshop Proceedings (pp 2-6-1 to 2-6-16). Wright--Patterson Air Force Base, OH: Flight Dynamics Laboratory.

Roscoe, S. N. (1986). Designed for disaster. Human Factors Society Bulletin, 29(6), 1-2.

Roscoe, S. N. (1986). Stanley N. Roscoe replies. Human Factors Society Bulletin, 29(9), 5.

Lintern, G., Roscoe, S. N., & Sivier, J. E. (1990). Display principles, control dynamics, and environmental factors in pilot training and transfer. Human Factors, 32, 299-317.

Roscoe, S. N. (1992). From the roots to the branches of cockpit design: Problems, principles, products. Human Factors Society Bulletin, 35(12), 1-2.

Roscoe, S. N. (1999). Forgotten lessons in aviation human factors. In D. O'Hare (Ed.), Human performance in general aviation. Aldershot, England: Ashgate.

Stanley N. Roscoe, Ph.D., WW2 pilot, is emeritus professor of aviation, engineering psychology, and aeronautical and astronautical engineering, University of Illinois at Urbana-Champaign; emeritus professor of psychology, New Mexico State University; former head of the Display Systems Department of Hughes Aircraft Company; president of ILLIANA Aviation Sciences Limited of McKinleyville, California and Las Cruces, New Mexico; and senior vice president of Aero Innovation, Inc. an aviation human factors company of Montreal, Quebec.

Read "More About Aircraft Attitude and Steering Displays"
Other details in "Design-Induced Errors" in AeroNews 1/96
Read: "How Do Graveyard Spirals Occur?"
Click here for an animation of the displays. Flash Player required.

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