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Proceedings Paper

Frequency response of helicopter pilot head azimuth, pitch, and tilt: approaching engineering specifications
Author(s): Leonard A. Temme; David L. Still; Adrianus J. M. Houtsma
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Paper Abstract

Background: Since helmet mounted displays (HMDs) are slaved to a pilot's head, head motion is important for the design of HMDs and their symbology. This is particularly true since the lateral tilt of a pilot's head changes when the pilot shifts his/her gaze from the horizon visible outside the cockpit to the instruments inside the cockpit. This change in head tilt, which may contribute to episodes of spatial disorientation and possibly dangerous control input reversal errors, is commonly attributed to a neuro-muscular reflex driven by the apparent tilt of the visible horizon, the so-called optokinetic cervical reflex (OKCR). The present paper: (1) describes head motion in the frequency domain, and (2) elaborates a biomechanical explanation for the observed head tilt that is simpler than the neurological OKCR model. Methods: Fourier spectral decompositions were calculated from archived head pitch, tilt, and azimuth data recorded at 10 Hz from four pilots as they executed a slalom maneuver in an AH Mk 7 Linx helicopter. Pilots A through D performed the slalom 11, 12, 8, and 11 times, respectively, for a total of 42 flights. Results: The Fourier decomposition showed that the typical azimuth spectrum differs from that of pitch, and tilt. Discussion: These results provide: (1) spectral descriptions of head azimuth, pitch, and tilt to aid the design of HMD systems, and (2) further support for the biomechanical model of head tilt.

Paper Details

Date Published: 5 May 2006
PDF: 14 pages
Proc. SPIE 6224, Helmet- and Head-Mounted Displays XI: Technologies and Applications, 622404 (5 May 2006); doi: 10.1117/12.668016
Show Author Affiliations
Leonard A. Temme, U.S. Army Aeromedical Research Lab. (United States)
David L. Still, U.S. Army Aeromedical Research Lab. (United States)
Adrianus J. M. Houtsma, U.S. Army Aeromedical Research Lab. (United States)


Published in SPIE Proceedings Vol. 6224:
Helmet- and Head-Mounted Displays XI: Technologies and Applications
Randall W. Brown; Peter L. Marasco; Clarence E. Rash; Colin E. Reese, Editor(s)

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