HEAD ALIGNMENT OF THE

GENERAL AVIATION PILOT DURING FLIGHT

 

 

 

 

 

 

 

 

 

A thesis submitted in partial fulfillment

of the requirements for the degree of

Master of Science

 

 

 

By

 

 

 

KAZUHITO SHIMADA

M.D., University of Tsukuba, 1983

Ph.D., University of Tsukuba, 1987

 

 

 

 

 

 

 

1995

Wright State University

 

 

WRIGHT STATE UNIVERSITY

 

SCHOOL OF GRADUATE STUDIES

 

 

                                      , 1995

 

            I HEREBY RECOMMEND THAT THE THESIS PREPARED UNDER MY

SUPERVISION BY Kazuhito Shimada ENTITLED Head Alignment of General Aviation Pilot BE ACCEPTED IN PARTIAL FULFILLMENT OF THE

REQUIREMENTS FOR THE DEGREE OF Master of Science.

 

 

 

                                                                                                                                              

                                                                                    Anthony J. Cacioppo, Ph.D.

                                                                                                Thesis Director

 

 

                                                                                                                                              

                                                                                    Stanley R. Mohler, M.D.

                                                                                                Department Chair

Committee on

Final Examination

 

 

                                                                      

            Anthony J. Cacioppo, Ph.D.

 

 

                                                                      

            Stanley R. Mohler, M.D.

 

 

                                                                      

            Robin E. Dodge, M.D., M.S.

 

 

                                                                       

            Satya P. Sangal, Ph.D.

 

 

                                                                      

Joseph F. Thomas, Jr., Ph.D.

Dean, School of Graduate Studies


ABSTRACT

 

 

Shimada, Kazuhito. M.D., Ph.D., M.S., Department of Community Health,

Wright State University, 1995.  Head Alignment of the General Aviation Pilot During Flight.

 

 

 

The professional literature provides a lack of relevant research dealing with the dynamics of pilot head motion during flight.  This study analyzed the head alignment of 10 civilian pilots during turns in flight using data collection from a head-mounted videocamera.  Pilots were found to roll their head around the head x-axis in a direction opposite to the center of turn.  The angle of aircraft roll and head roll had a linear relationship when pilots were flying solely with visual cues (V mode) or acting as second-in-command (P2 mode).  Pilot head roll response plateaued when pilots were referring to both external visual cues and the attitude indicator (AI mode).  Asymmetrical pilot head roll response was found in left and right turns when pilots were in V mode.  The slope of the head roll angle vs. aircraft roll was the steepest in P2 mode and the shallowest in AI mode.  Individual variation in pilot head roll response tended to relate to subject age and experience.  Pilot head roll response had minimal phase difference to aircraft roll for roll-in, but had a lag for roll-out.  Overshoot in pilot head roll was observed in roll-out.  The magnitude and time course of head roll response in ground turns were similar to those in flight, except for the direction.  The origin of pilot head response may have a relationship to the righting reflex.  It is predicted that any combination of +Gz and pilot head roll response will produce a tangential force to the skull/C1/C2 joints.
                                                TABLE OF CONTENTS

 


1.            INTRODUCTION                 1

 

2.            BACKGROUND                  3

 

3.            RESEARCH OBJECTIVES               10

 

4.            METHODS           11

 

4.1          Subjects                 11

4.2          Aircraft                  14

4.3          Airspace and weather          14

4.4          Head tilt recording              15

4.5          Flight task             21

4.6          Ground task           23

4.7          Pilot briefing        23

4.8          Experimental design           24

 

5.            RESULTS              26

 

5.1          Flight conditions                 26

5.2          Quality of recorded image                27

5.3          Body leans            28

5.4          Pilot head roll angle            29

5.5          Comparison of three flight modes (AI, visual, and non-flying)                 35

5.6          Regression analysis            35

5.7          ANOVA analysis                 38

5.8          t-test       40

5.9          Comparison between the direction of aircraft roll (left or right)             42

5.10       Comparison by subject age and flight time     46

5.11       Time series analysis of pilot head roll response           52

5.12       Head roll in turns on the ground       56

 

6.            DISCUSSION AND CONCLUSIONS             62

 

6.1          Existence of pilot head roll response             62

6.2          Body leans            64


 

cont. 6. DISCUSSION AND CONCLUSIONS

6.3          Head motion in other modes of transportation             65

               6.4          Response of non-flying pilot                 70

6.5          Response of visually flying pilot      71

6.6          Response of partially visual, partially instrument pilot               72

6.7          Individual variation in pilot head roll response             74

6.8          Phase comparison of aircraft roll and head roll            74

6.9          Response in ground turns                  75

6.10       Comparison with simulator study     76

6.11       Implication for cockpit design          77

6.12       Effect of peripheral vision                80

6.13       Implication for pilot health stabilization        82

6.14       Physiological background of pilot head roll and its implication for motion sickness          84

6.15       Future study design             86

 

7.            SUMMARY          89

 

8.            APPENDICES      90

 

8.1          Nomenclature for body axes             90

8.2          Table 15. - Flight maneuver sequence for subject #8.               93

8.3          Table 16.-In-flight raw data.              94

8.4          Consent form for subjects.           98

 

9.            REFERENCES    100



LIST OF FIGURES

Figure 1.-Computer graphics attitude display.               4

Figure 2.-Variation in Attitude Indicator design.           4

Figure 3.-View of AI and the horizon.              5

Figure 4.-Head roll of F-16 pilot in 9 G turn.                9

Figure 5.-Research airplane.  Cessna C172L Skyhawk, fixed-gear, 4-place.        12

Figure 6.-Instrument layout of the research airplane.                  12

Figure 7.-Visual Flight Rule 1:500,000 sectional chart for the flight test air space.           13

Figure 8.-Videocamera mounted on a headset.             16

Figure 9.-Data acquisition system diagram.                 16

Figure 10.-Dimension of videocamera setting in the research airplane.                 17

Figure 11.-Calibration of videocamera angle.               18

Figure 12.-Cockpit picture in analysis.           18

Figure 13.-Head alignment of a pilot in 45 bank turn to the left.            19

Figure 14.-Head roll angle around head x-axis, in Attitude Indicator mode of flight.           30

Figure 15.-Head roll angle around head x-axis, in vidual flight mode.    30

Figure 16.-Head roll angle around head x-axis, in non flying flight mode.             30

Figure 17.-Pilot head roll around head x-axis during aircraft turn, in Attitude Indicator mode of flight.                    32

Figure 18.-Pilot head roll around head x-axis during aircraft turn, in visual mode of flight.             33

Figure 19.-Pilot head roll around head x-axis during aircraft turn, in non-flying mode of flight.                    34

Figure 20.-Regression coefficient (ordinate) for aircraft bank angle  vs. head roll angle.                36

Figure 21.-Regression analysis for head roll angle vs. aircraft roll angle.               37

Figure 22.-Field of view for Cessna 172L.   43

Figure 23.-Scattergram of subject age vs. head roll angle, left aircraft roll.            47

Figure 24.-Scattergram of subject age vs. head roll angle, right aircraft roll.          48

Figure 25.-Scattergram of subject flight time vs. head roll angle, left aircraft roll.             49

Figure 26.-Scattergram of subject flight time vs. head roll angle, right aircraft roll.           50

Figure 27.-Head roll angle around head x-axis of each subjects.            51

Figure 28.-Time course of aircraft and head roll around their x-axis, Attitude Indicator flight mode.                  53

Figure 29.-Time course of aircraft and head roll around their x-axis, visual flight mode      54

Figure 30.-Time course of aircraft and head roll around their x-axis, non-flying mode.      55

Figure 31.-Head roll in ground turn.               57

Figure 32.-Head roll during a 180 course reversal on the ground, time series.     58

Figure 33.-Head roll during a 180 course reversal on the ground.          59

Figure 34.-The relation between elapsed time and aircraft heading for Figure 32 and Figure 33.      60

Figure 35.-Head position of a passenger in 90 bank flight.       63

Figure 36.-Automobile driverfs head alignment during roll of vehicle around its x-axis (longitudinal axis).       66

Figure 37.-Head alignment of an automobile driver.   67

Figure 38.-Motorcycle rider and passengerfs head alignment in turn.      68

Figure 39.-Latest Head Up Display symbols.                79

Figure 40.-Cervical spine alignment on head roll.        81

Figure 41.-Nomenclature for axes.                  92

 

 

                                                LIST OF TABLES

 

 

 

 

 

Table 1.-Terms equivalent to emoving horizonf and emoving aircraftf.            7

Table 2.-Profile of pilot subjects.       11

Table 3.-Ground simulator study result.          24

Table 4.-Head roll with body lean, subject #9.            28

Table 5.-Result of pilot head roll angle around head x-axis during aircraft turn.         31

Table 6.-ANOVA table for subject and flight mode.   39

Table 7.-Post-hoc test for head roll angle difference among flight modes.       39

Table 8.-A matrix of t-test for difference in head roll among flight modes at each aircraft roll (bank) angle.         41

Table 9.-Comparison of head roll angle between left and right aircraft roll, all flight modes.              44

Table 10.-Comparison of head roll angle between left and right aircraft roll, Attitude Indicator flight mode.               44

Table 11.-Comparison of head roll angle between left and right aircraft roll, visual flight mode.      45

Table 12.-Comparison of head roll angle between left and right aircraft roll, non-flying flight mode.      45

Table 13.-Regression coefficients from simulator and flight study.     76

Table 14. +Gz values for aircraft roll angles.              85

Table 15. - Flight maneuver sequence for subject #8.             93

Table 16.-In-flight raw data.   94

 

 

 

 

 

 

 

 

 

                                                ACKNOWLEDGEMENTS

 

 

 

 

 

 

 

            I would like to extend my sincerest thanks to the following people for their assistance in the undertaking of this study:

Stanley R. Mohler, M.D., Anthony J. Cacioppo, Ph.D., Satya P. Sangal, Ph.D., Robin E. Dodge, M.D., and Frederick R. Patterson, Ph.D.

             I am grateful to Terry Taddeo, M.D. and Fumi Shimada for their help in manuscript preparation.



 

 

 

                                    1.         INTRODUCTION

 

 

 

            Spatial disorientation is still a pilot killer.  Spatial disorientation is associated with the experiencing of an orientational illusion for pilots [Gillingham 1985].  Loss of situational awareness has been a major concern in military aviation, where one encounters a wide aircraft aerodynamic envelope (acceleration and velocity) [Barnum 1968, Cheung 1995].  Requirements for close formation flying under poor weather conditions is another factor related to this phenomenon.  Civilian aviation has not placed much emphasis on this pilot-system limitation [Kirkham 1978, Johnson 1989, AOPA 1993].  Is it a problem only for high-performance fighter pilots?

            Recently spatial disorientation was identified as a link in the causal chain of factors related to a major US air carrier crash.  A DC-9 jetliner had a collision with the ground because of an encounter with a microburst and the pilotsf subsequent  loss of situational awareness due to somatogravic illusion [NTSB  1994].  The flight crew became disoriented during the transition from Visual Meteorological Conditions to Instrumental Meteorological Conditions.

            What type of computer graphic display, head-up display, or head-mounted display might facilitate spatial orientation?  What should be the contents of a training syllabus against disorientation?  Is our understanding of its pathophysiology sufficient to permit the design of truly better instruments and training?

            In aerospace medicine textbooks, there has been no quantitative description about natural body and head alignment of pilots other than in a straight and level flight.  Only recently this was challenged by two ground simulator studies [Patterson 1995A, Smith 1995].  Some flight instructors teach students that keeping their head and body straight along the body z-axis (longitudinal axis, Figure 41) is the proper body alignment.  But the simulator study found that pilots laterally deflect their heads during turning maneuvers.

            Positional alignment of head and body during flight maneuvers is a significant limiting factor for the design of instruments and cockpit layout.  The latest designs of Head-Up Displays or Head-Mounted Displays are more sensitive to this geometry because of their limited angle of view.  In order to view some military head-up displays, the eyes must be kept within an 8 x 13 cm (3 x 5 inch) field.  These limits are easily exceeded if pilots roll their head around their head x-axis (deflect the head laterally).

            The physiological dynamics of pilot head motion during flight has yet to be investigated.

 

                                    2.         BACKGROUND

 

 

            Actively controlled human flight began with hang gliders, under visual flight condition.  The Wright Brothers from Dayton, Ohio began controlled, powered flight after their extensive experiments with gliders.  The next breakthrough, was the invention of the aircraftfs attitude display.

            Prior to the emergence of the apparatus, there was an interesting instrument arrangement used by Charles A. Lindbergh for his solo transatlantic flight in 1927.  Since his forward view was blocked by a fuel tank, he used a periscope to provide a visual reference [Roscoe 1966].  Although he is said to have used forward slipping during approach to gain a better view of the runway, the periscope deprived him of peripheral vision, which is important for pilots [Kochhar 1978].

            Based upon his design of a gyroscopic stabilizer for ships, Elmer Sperry, Jr. [Laboda 1995], in 1910, extended the technology by developing a gyroscope for use by pilots for determining aircraft attitude.  The Sperry Artificial Horizon allowed Lt. James H. Doolittle to fly his NY-2 Navy trainer airplane eblindf on 24 September 1929.  This historic apparatus is on display at the US Air Force Museum, Dayton, Ohio.
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1.-Computer graphics attitude display.

A display of a Fokker F-100 jetliner.  It is the latest design in use, but stays with the concept of a stationary aircraft symbol with a moving horizon.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 2.-Variation in Attitude Indicator design.

This AI in a 1966 Piper PA30B twin piston-engine airplane has a bank pointer that moves with the horizon bar, instead of with the miniature airplane. Many AIfs of this design are still in use today.  This kind of design variation is also seen in VOR (Very High Frequency Omni Range) indicators.
Figure 3.-View of AI and the earth horizon.

The Attitude Indicator (arrow) and the earth horizon seen from cockpit of a CH2000 single engine airplane.  The roll angle of the aircraft is 64 to the left.  This picture is aligned to the page so that it looks natural to the reader, while actually it differs from the retinal image of the pilots in the cockpit because of the limited motion of the head in flight.

[ AOPA Pilot, 36(12),1993: 47 ]


 

            There is a speculation that Lindberghfs success with the periscope may have affected the design of the artificial horizon (now called the Attitude Indicator, Figure 1, Figure 2).  All operational attitude indicators, except for those of Russian design, use emoving horizonf symbolic design.  The horizon bar (Figure 1) resembles that of a short portion of the earth horizon as if seen through a periscope (Figure 3).

            Peripheral displays, such as the para-visual director, peripheral command indicator, HOVERING display, and the Malcolm horizon stimulate peripheral vision to provide aircraft attitude information [Stokes 1988].  They have proven to be relatively effective despite degraded visual acuity associated with peripheral vision.  Visual acuity in Snellenfs fraction decreases from 1.0 in the visual center to 0.2 at 10 off center, 0.1 at 20, and 0.07 at 30 [Westheimer 1992].

            How can we present attitude information to maximize foveal vision?  Although the options are many, modern Russian fighters use an attitude display whose miniature airplane, instead of a horizon bar, rolls.

            In the past, no commercial competition was seen between the emoving horizonf and emoving airplanef display.  This is probably due to the initial success of the Sperry artificial horizon and the comprehensive analogy of periscopic view (ecut outf earth horizon appears in an Attitude Indicator) [Poppen 1936, Roscoe 1966].  Other equivalent terms, which are often confusing, are summarized in Table 1.  It is worth noting that an integrated display which changes from emoving aircraftf to emoving horizonf for roll-in has been devised [Fogel 1959, Roscoe 1975].

 

Table 1.-Terms equivalent to emoving horizonf and emoving aircraftf.

            moving horizon                                                moving airplane

            inside-out                                                        outside-in       

            fly-to                                                               fly-from

            moving card or tape                            moving pointer

            earth referenced                                              aircraft referenced

            aircraft stabilized                                            space stabilized

            in aircraft coordinates                         in earth coordinates

            modified from [Johnson 1972]

 

 

            A study by the Federal Aviation Administration Civil Aeromedical Institute with a Beechcraft T-34 [Hasbrook 1973] compared the two types of display and concluded that:

                        Data from many of these earlier studies suggest that the outside-in (moving-                     aircraft) indicator provides better pilot performance:  but this in-flight study                  fails, in the main, to show any such well defined, overall advantage.

 

            Despite pioneer efforts, it was not until 1930 that military pilots were taught that the instruments should be used as source for flight information and that they should not fly by the gseat of their pantsh [Malcolm 1984].  This is not widely understood among todayfs leisure pilots.

            When one questions the dynamics associated in comparing a emoving horizonf with emoving airplanef, the answer is ambiguous.  Missing is the recognition of natural behavior of the pilots.  What is the natural position of the head relative to the cockpit?

            When asked if the head moves during flight, most pilots will answer enof.  Only a few pilots admit that they roll their head.  Even demonstration team members of the US Navy [Patterson 1995A] and the US Air Force (Figure 4) were observed to roll their heads around the head z-axis (tilt their head) in a direction opposite to the center of the turn in visual flight.   Pilots prefer to view a picture as if aligned to the earth horizon rather than to the cockpit (Figure 3).  The only literature about head motion in flight, which surfaced, gave a general indication that subject pilots kept their head z-axis normal to the ground [Hasbrook 1973].

            Recent simulator sutdies revived this old but unanswered question [Patterson 1995A, Smith 1995].  If pilots are rolling their heads, is a emoving horizonf better adapted to prevent roll reversal (mistakenly initiate roll to the opposite direction)?  What if the display moves with the head instead of being fixed to the cockpit?  What is the natural motion of the head that should be assumed in a new display design?  Which attributes of display design should be adopted?

 

 

Figure 4.-Head roll of F-16 pilot in 9 G turn.

 

This U.S. Air Force Thunderbirds demonstration team member is quickly rolling into 9 G turn.  The roll (bank) angle of aircraft in this picture is 64 (ÐBOHf).  His head is rolled to the right around head x-axis (laterally deflected to the right) with an angle of 15 (90 - ÐAOH) relative to the cockpit.  Cockpit level is represented by line HHf.  Because the body is leaned to the right with an angle of 3 (ÐHOS), the angle of head roll relative to the body z-axis is 12 (15 - 3).  There is a slight yaw of the head to the left, which does not affect more than 1 for this head roll angle relationship to the cockpit.  A transient maximum roll of the head of 24 relative to the cockpit was observed when roll of the aircraft was at 60 (just before this picture).  After this picture, roll of aircraft was kept 82 to 85 to keep 9 G turn, which theoretically requires 83.6 of bank [ cos- 1 (1/9) ].  Head roll angle was kept approximately 6 to the right relative to the cockpit while 9 G 360 turn was continued.

 [ International Video Corporation 1990 ]

 

 

                                    3.         RESEARCH OBJECTIVES

 

 

 

            The purpose of this research is to determine how pilots (flying and non-flying) align their heads during actual flights in a general aviation aircraft.

            It is hypothesized that general aviation pilots in visual flight rule (VFR) conditions align their heads with the horizon of the earth for visual orientation, which causes head rotations around the x-axis of the head.  This study examines this hypothesis by recording and analyzing pilot head motion during actual VFR flight in a general aviation aircraft.

            To supplement the flight test, head motion data were collected during the ground taxing phase of a flight.

 

                                                4.         METHODS

 

4.1       Subjects

 

    A total of 10 civilian volunteer pilots holding current FAA medical certificate (either class 2 or 3) and FAA pilot rating (either private, commercial, or Air Transport Pilot) participated (Table 2). 

    The protocol for participation by  human subjects was approved, prior to flight test, by the Office of Research and Sponsored Programs, Wright State University.

 

 

Table 2.-Profile of pilot subjects.

subject number (n = 10)

(numbered as tested)

total flight time [hours] (airplane)

age

[years]

8

80

38

9

110

37

6

485

41

7

570

22

1

710

31

4

780

24

3

1200

26

5

1230

30

10

2600

34

2

4000

47

mean, sample SD

1177 ,  1165

33.0 , 7.52

 

 All subjects held current FAA certificate for the research airplane.  All 10 subjects were male with an age rage of 22 - 47 years and airplane flight tie of 80 - 4000 hours.  None had military flying experience.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 5.-Research airplane.  Cessna C172L Skyhawk, fixed-gear, 4-place.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 6.-Instrument layout of the research airplane.

Attitude Indicator type is EDO-AIRE 5000F-6.  The miniature airplane of the AI moves with the bank pointer, which is the standard in U.S. at present.  This picture was taken from pilot eyepoint with a comparable field (35 mm film, f = 35 mm).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure. 7.-Visual Flight Rule 1:500,000 sectional chart for the flight test air space.  The area marked by arrows was used for the research flights.  The meteorological condition was better than VFR minimum; Dayton visibility was 10 statute miles or better for 9 subjects and 7 miles for subject #9.  Dayton wind was 6-15 knots.  Flight altitude was 1500-3500 feet Above Ground Level, more than 1000 feet below the clouds.  All flights were completed within daylight hours.
4.2       Aircraft

 

                        The aircraft used for this study was a 150 horse power, single-engine land, fixed-gear, 4-place general aviation utility airplane (Figure 5, Cessna C172L, N7116Q,  based at Brookville Air Park, airport code I62).   All subjects were volunteers familiar with this airplane type.

                       The research airplane was equipped with a set of standard Instrument Flight Rule instruments, which includes an attitude indicator (attitude gyro).  Figure 6 shows instrument panel arrangement.  This picture corresponds to the pilotfs view in flight.  Attitude Indicator is located at top center of the eTf layout for cardinal Instrument Flight Rule instruments.

 

4.3       Airspace and weather

 

                        The airplane took off from Brookville airport and returned.  Flight maneuvers took place in a practice area approximately 15 km southwest of the airport (Figure 7).  Because of Dayton jet traffic, flight altitude was kept below 4,000 feet Above Ground Level.  The altitude flown was between 1,500 and 3,500 feet AGL, and was at least 1,000 feet below the clouds. 

                        Visibility reported at Dayton International Airport at the time of flights was better or equal to 10 statute miles for 9 subjects; 7 statute miles for subject #9.  Surface wind at Dayton was reported at 6 to 15 knots, generally from southwest.  There was a slight turbulence for subject #2 due to thermals.  Other subjects had no turbulence.  Surface temperature at Dayton International Airport (308 m above Mean Sea Level) was between -4 to +11 C.  All flights were completed within daylight hours under Visual Meteorological Condition.  Weather was at all times above federal Visual Flight Rule minimums.

 

4.4       Head tilt recording

 

                        The subjects were seated in the left seat of the airplane.   They wore a small, light-weight (70 g) CCD camera(Sony CCD-MC1, f=3.6 mm) on a headset (Figure 8 ).  Video recording was made during taxi and flight with a NTSC-VHS portable video cassette recorder (Panasonic AG-170). 

                         The center of the videocamera field was aimed at the center of a white bar, 530 mm in length,  located on the top of the instrument panel.  The horizon of the earth was visible in the camera field (Figure 10).  Alignment of the camera relative to the earth horizon was calibrated with a grid pattern and a protractor while on the ground (Figure 11).  Angular readings were entered into computer  by keyboard (Figure 9).

                         Subjectsf head motion relative to the cockpit were analyzed from the recorded video picture.  Head roll angle around the head x-axis was measured on a TV monitor screen with a protractor, frame by frame (Panasonic AG-1970 video cassette recorder and Sony SSM-2010 monitor) (Figure 12). In-flight pictures were compared to a calibrated video picture recorded during the preflight phase on the ground. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 8.-Videocamera mounted on a headset.

SONY CCD-MC1 lightweight videocamera was mounted onto David Clark H10-13.4 aviation headset.  The head pad of the headset was removed to minimize height.  Cables were not interfering with pilot head motion.  Line-of-sight of the camera had an angle range of 10 - 15 relative to horizon when a pilot is in the seat (Figure 10).

 

 

 

 

 

Figure 9.-Data acquisition system diagram.  The video tape pictured with a portable videorecorder was manually analyzed and the result was entered to computer through keyboard.

 

 

 

 

Figure 10.-Dimension of videocamera setting in the research airplane.

 

Figures are shown in mm.  The height of the subjects ranged from 172 cm to 190 cm, which varied the line-of-sight angle of the videocamera from 10˚ to 15˚ relative to horizon.  This range of camera angle did not cause rotational skew of the cockpit image more than 1˚.

 

B: reference bar at the top of instrument panel.

C: optical center of CCD videocamera attached to headset.

E: eyepoint of subject.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 11.-Calibration of videocamera angle.

Angle of the head of a pilot and reference white bar on instrument panel is in calibration with a protractor mounted on the head, a grid, strings and weights.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 12.-Cockpit picture in analysis.

Video images were measured manually frame by frame with a 20-inch video monitor and a protractor.  Both aircraft roll and head roll were measured in this example frame.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

      Figure 13.-Head alignment of a pilot in 45 bank turn to the left.

 

Posterior view of a pilot flying Cessna 172P.  Actual roll (bank) angle of the airplane was 48 to the left at the moment this video frame was captured.  The head is rolled to the right around head x-axis with an angle of 11 relative to the cockpit.  This student pilot was trying to keep 45 bank turn.  It is common to observe small amount of jerky transient head roll component superimposed onto steady bias.  Note that this picture was taken by a videocamera different from that used for data collection.

            When the head of pilot rolled to the right, it was reflected by the left roll of the white bar on the top of the instrument panel.  Actual roll angle of the aircraft was also measured from the angle between the earth horizon and the white bar on the instrument panel (Figure 13).  The initiation of aircraft rolling motion, the return to level and straight flight, and the angle of the head relative to the cockpit (the white bar) were all evident in video picture.  Frame-by-frame analysis of the picture was made necessary to determine the roll angle of the head because there were small-angle motions superimposed on relatively large-angle static components, the result of establishing in aircraft turn (constant bank angle).

            Time resolution of the measurement was 1/30 seconds (video frame interval).  The angular resolution limit of rotation around head x-axis was unmeasurable because the resolution limit was much better than the precision of mechanical rotatory positioning of videocamera on a tripod.  A protractor used for reading had 1 step in scale.

            There was an artifact in the picture rotation in the head coronal plane when subjects rolled their head around the head z-axis (roll in the horizontal plane).  The amplitude of this (around x-axis) angular artifact was 1.0˚ per 10˚ of head roll (around z-axis).  That is, when subjects looked 10˚ to the left (horizontally), it seemed as if they tilted their head 1 to the left.  It was revealed in post-flight video analysis that all necessary scenes were recorded with less than 10 of the head roll around the head z-axis.  Thus artifact effect due to this phenomenon was less than 1 in this study.

            There was no measurable artifact in the picture rotation due to head roll around the head y-axis (head pitch change).

            Overall precision and systemic error estimation for angular measurement was 1˚.  This was considered a degrade for this study.  No positional drift of the videocamera, due to headset slippage relative to the skull, was observed in the post-flight video analysis.

           

4.5       Flight task

 

            The subject sat in the left seat of the airplane.  The investigator took the right seat.  The flight task was categorized into three flight modes; AI (Attitude indicator) mode, visual mode, and non-flying mode.

 

  Attitude Indicator   Subject flew the aircraft with attitude indicator and              mode               visual reference.  This mode examined subjectfs response in combined visual/instrument                                            environment.

 

• Visual mode              Subject flew the aircraft with visual reference only                                       (with no instrument reference). This mode examined subjectfs response with pure outside                                                visual reference.

 

• Non-flying mode                   Right seat pilot (the investigator) flew the aircraft;                                 subject observed outside of aircraft.  This mode examined subjectfs response in alert, motivated but                                      non-controlling state.

 

 

            For each flight mode, 6 turns were flown.  Bank angle of the aircraft for every turn was assigned to a subject randomly by the investigator.  The bank angles used were: right and left 45 ˚, right and left 30 ˚, right and left 15 ˚. These bank angles are also expressed with + sign indicating right bank and - sign indicating left bank, i.e. -45, -30, -15, +15, +30, and +45 degrees.  Head motion recording was continued in level and straight flight (bank angle 0 ˚)  and ground taxi.

            The first run of flight maneuvers was started from AI mode, then to visual mode, and ended in non-flying mode, with 6 x 3 = 18 turns in a run. Within each flight mode, 6 bank angles were arranged randomly.

            Each subject had 3 runs, 18 x 3 = 54 turns in total.  Order of flight mode was kept the same (AI, visual, then non-flying mode), in order to avoid flying successively in a same mode.  The order of bank angles within each mode was changed randomly.

            An example of the order of flight maneuvers with raw head angle data are shown in Table 15 (in Appendix).
4.6       Ground task

 

            No specific assignment was given to subjects for ground maneuvers (turns on runway or taxiway).  Video images for ground turn analysis were selected from continuous video record, based on picture quality (lighting condition was a major factor).

 

4.7       Pilot briefing

 

            Before a flight, the subject pilot was briefed orally as follows:

gThe purpose of this research is to measure your neck motion during the flight.  Since some amount of natural cervical motion is anticipated, DO NOT restrict your body motion.  Fly and look out as you always do.  But do not keep looking into the side windows during record turns (to keep the angle of the videocamera within a favorable range). Make clearing turns before record turns if necessary.h

gCount to three out loud when flying level and straight (counting was used to time straight and level portion of the flight and clarify subjectfs intention).  Roll in and out at your usual rate.  Count to ten out loud after you have established the specified bank angle.h

            For the Attitude Indicator mode, subjects were orally briefed as follows:

gUse the attitude indicator to establish and keep the specified bank angle.h

            For visual mode, subjects were orally briefed as follows:

gDo not refer to the instrument panel for this turn.h

            For non-flying mode, subjects were orally briefed as follows:

gI have the airplane controls.  You will look out for other traffic.h

            No specific instruction was given to the subjects for ground taxi.

 

4.8       Experimental design

 

            The ground simulator data (Patterson 1995A) showed that variance of head roll angle is relatively small when aircraft roll angle is within 45˚.  From this result, it was estimated that head roll angles in flight test would have a standard deviation of 8 degrees or less (Table 3).

 

 

 

Table 3.-Ground simulator study data.

                                                                                                                               

Aircraft roll angle@ Head roll angle [deg]@ Sample mean (n=14) variance

45˚ left                        13.75                           32.36

30˚ left                        11.32                           11.75

15˚ left                        5.31                             3.74

15˚ right                                  -4.79                              5.53

30˚ right                      @@@-10.39                          15.31

45˚ right                -12.87              39.30          

 The largest Standard Deviation was 6.27 (square root of 39.30) for 45 right aircraft roll.  Arbitrary assumption that flight data will have 30 % larger SD than simulator study yielded SD estimation of about 8 for flight test data.

 [Patterson 1995A]

 

 

 

            The number of subjects necessary was estimated to be at least 10 with the assumptions below [Odeh 1975]:

 

• randomized block experimental design with subjects as blocks

• five degrees difference in head roll angle is to be detected among flight       modes (with Attitude Indicator, visual, and non-flying status.)

• average variance of the groups is 3/4 that of random variation

• error rate

• estimated standard deviation of head roll angle is less than 8 degrees

 

            The statistical design for this study is a factorial design, 10 subjects  3 flight modes  7 aircraft bank angles.  The dependent variable was head roll angle.  Subjects were treated as a random factor.

 

 

 

 

                                                5.         RESULTS

 

 

 

 

5.1       Flight conditions

 

            The 10 subjects completed all assigned tasks.  Since the flight maneuvers were simple turns, only one subject was requested to re-try two of the turns due to shallower bank angles than specified.  All turns were coordinated to within half ball deviation on the inclinometer.

            Flight time (block to block) for subjects ranged from 30 minutes to 1 hour 18 minutes, average was 50 minutes.  Recording maneuvers in the air took approximately 20 minutes for 54 turns.  The remainder of the flight was devoted to taxi, ascent and approach, horizontal repositioning in the airspace (mostly for wind correction), and test equipment operation.
5.2       Quality of recorded image

 

            Spot measurement of head position in flight pictures was not difficult n = 10).  However, transient blockage of camera view was not infrequent with the pilotfs hand or the sun in view.  The quality of video images were satisfactory in lighting and in camera angle for 26 flight maneuvers with 3 subjects (#8,9,10) for frame-by-frame time series analysis.

            For ground phase analysis (n =10),  8 ground maneuver images from 5 subjects (#4,5,6,9,10) were satisfactory for spot measurement; only one image was subjected to frame-by-frame time series analysis (subject #10).

            By comparison to the earth horizon, it was found that the attitude indicator had a systemic error of 5˚.  The attitude gyro indicator onboard, EDO-AIRE 5000F-6 Serial No.29005F, indicated correct bank angle to the right, but 5˚ more than actual to the left.  That is, 45˚ bank to the left was actually at 40˚.  It was still in compliance with federal regulations, including TSO-C4C for Attitude instruments [Kelly Instruments].  Correcting the instrument was technically difficult.  Since there was no redundant equipment onboard the aircraft for real-time reference, data were not correctable for this instrument error.  This did not affect the precision or systemic error of head angle measurement.  However, careful analysis for the difference in the right and the left turn was required.

5.3       Body leans

 

            Simultaneous and independent recording of the head motion and the torso motion was not feasible because only one videocamera was onboard the research airplane. Specific attention was paid to the torso lean of subjects, by the investigator in the right seat.  To evaluate the leans of subject body, the lateral deviation of the shoulders relative to a seatback was visually monitored.  Only the first 6 turns by subject #9 was observed to have had leans, with shoulder lateral deviation in excess of 5 cm.  None of other subjects presented deviation more than 3 cm.   Forward leaning was frequently monitored when subjects tried to check upward traffic in non-flying flight mode.

           Head roll angle data with noticeable body lean from subject #8 is presented in Table 4.  The data were included in the data set for this study, because there was no meaningful trend in these values.

 

Table 4.-Head roll with body lean, subject #9.

aircraft roll angle        @@@ run #1*              run #2 @@ run #3            mean

            left      45                              4                      2                    3                    0.3

            left      30                              7                    2                      10                    5

            left      15                              0                    1                    3                    1.3

            right     15                              5                      5                      0                    3.3

            right     30                              4                      1                      1                 -2

            right     45                              5                      5                -11              -7

*Body lean was observed in the 6 maneuvers of run #1.  All values are in degrees.  Negative sign means head roll to the left.
5.4       Pilot head roll angle

 

            The head roll angles of subjects, around the head x-axis, during in-flight turns showed a distinct relationship to the bank angle of airplane (Figure 14, Figure 15, Figure 16).  Neutral point of the head around the head x-axis, where head roll angle is 0˚, was defined as the position of the head immediately before the aircraft began a move to roll-in.  Raw in-flight data are shown in Table 16 (in Appendix).

            The magnitude of head roll response of each subject varied.  However, each subjectfs response was generally symmetrical in the right and the left aircraft roll.  Sample mean head roll and group standard deviation are shown in Table 5, Figure 17, Figure 18, and Figure 19.  As seen from mean and Standard Deviation values, all data showed the pilotsf behavior to tilt (roll around the head x-axis) their head toward outside of the turn (in the direction that eyes follow the earth horizon).
 

                                                            

 

                        Figure 14.-Head roll angle                around head x-axis, in Attitude                       Indicator mode of flight. All 10                      subjects.  There is a considerable                individual variation.  However,                   each subjectfs head roll curve is                    symmetrical about direction of                       aircraft roll.

 

 

 

 

 

                        Figure 15.-Head roll angle                around head x-axis, in visual             flight mode.  All 10 subjects.                      There is a considerable                      individual variation.  However,                   each subjectfs head roll curve is                    symmetrical about direction of                       aircraft roll.

 

 

 

 

 

                        Figure 16.-Head roll angle                around head x-axis, in non-                 flying flight mode.  All 10                subjects.  There is a considerable                individual variation.  However,                   each subjectfs head roll curve is                    symmetrical about direction of                       aircraft roll.

 

 

 

 

 

 

Positive values for head or aircraft roll mean roll to the right; negative values mean roll to the left (-45 in aircraft roll angle means left 45 bank).

 

 

Table 5.-Result of pilot head roll angle around head x-axis during aircraft turn. 

 

 

           

   aircraft

roll angle

 [deg]  attitude indicator    flight mode             visual

 flight mode       non-flying

 flight mode

  mean

   [deg]          group

   S.D.                   mean

   [deg]          group

   S.D.                   mean

   [deg]          group

   S.D.     

 

  left

  turn          45                    5.5             5.2             9.0             5.8             8.3           6.3

30@4.9@       4.3       6.8       4.4       6.0       3.8

15@2.2           2.3       4.9       3.9       3.0       2.7

 

  right

  turn          +15                  -2.4            1.5             -2.0            2.0             -3.8            4.3

+30              -4.1                  3.7             -3.3            2.0             -5.8            5.8

+45              -4.8                  3.6             -4.8            4.8             -7.1            6.9

 

 

 

 

Negative values of aircraft roll angle means bank to the left; positive values mean bank to the right (-45 means turn to the left with a bank angle of 45.)  Negative values of head roll means left lateral deflection of the head (-2.4 means that the head was deflected 2.4 to the left.); positive values mean right lateral deflection of the head.  Opposite sign of head roll to aircraft roll means that the subject rolled the head in the direction that retinal image is stationary.  The maximum Standard Deviation value of 6.9 (at right 45 turn) was close to the pre-test estimation of 8.  Data from this table is used in Figures D, E, and F.  In Attitude Indicator flight mode, subject pilot used both visual cue and Attitude Indicator to fly; in visual flight mode, subject used only outside visual cue to fly; in non-flying mode, subject acted as non-flying pilot, looking outside for other air traffic without controlling the airplane.


Figure 17.-Pilot head roll around head x-axis during aircraft turn, in Attitude Indicator mode of flight. 

 

 

Sample mean and sample Standard Deviation plot of 10 subjects.  Each vertical bar represents +/- 1 SD.  Data are from Table 5.  Negative sign for head or aircraft roll means roll to the left (-45 aircraft roll means left turn with 45 bank angle.)  Slope of the curve is less than those of visual mode (Figure 18) or non-flying mode (Figure 19).  Head deflection is symmetrical for both direction of aircraft roll.  Head roll response is linear to aircraft roll within +/- 30 of aircraft roll(bank) angle.  Restricted head motion response was observed at +/- 45 of aircraft roll, which was not seen in visual or non-flying mode.

Figure 18.-Pilot head roll around head x-axis during aircraft turn, in visual mode of flight. 

 

 

Sample mean and sample Standard Deviation plot of 10 subjects.  Each vertical bar represents +/- 1 SD.  Data are from Table L.  Negative sign for head or aircraft roll means roll to the left (-45 aircraft roll means left turn with 45 bank angle.)  Slope of the curve is more than that of Attitude Indicator mode (Figure 17), and similar to that of non-flying mode (Figure F).  Head deflection is larger in left turn of the aircraft.  Head roll response is linear to aircraft roll within range of this experiment (+/- 45 of aircraft bank).

Figure 19.-Pilot head roll around head x-axis during aircraft turn, in non-flying mode of flight. 

 

 

Sample mean and sample Standard Deviation plot of 10 subjects.  Each vertical bar represents +/- 1 SD.  Data are from Table 5.  Negative sign for head or aircraft roll means roll to the left (-45 aircraft roll means left turn with 45 bank angle.)  Slope of the curve is more than that of Attitude Indicator mode (Figure 17), and similar to that of visual mode (Figure 18).  Slope of the curve is symmetrical to both direction of aircraft turn.  Magnitude of head roll response is linear to aircraft roll within range of this experiment (+/- 45 of aircraft bank).
5.5       Comparison of three flight modes (AI, visual, and non-flying)

 

 

            Head tilt (roll around the head x-axis) response due to aircraft bank angle was measured in Attitude Indicator mode (subject pilot uses both outside visual cues and attitude gyro indicator for spatial orientation), visual mode (only outside visual cue is used for orientation), and non-flying mode (subject observes outside without controlling airplane).

            The head roll angle data were statistically tested with regression, ANOVA, and t-test.

 

5.6       Regression analysis

 

            The relationship between aircraft bank and head roll angle, depicted in Figure 17, Figure 18, and Figure 19, can be approximated with a linear model.  When we assume their relationship as,

 

            [head roll angle]  =  B  [aircraft bank angle]

 

where B is a regression coefficient, the value of B for Attitude Indicator mode was -0.127; visual mode, -0.163; non-flying mode, -0.183.  95% t-test confidence intervals for B value were calculated as in Figure 20.  This figure shows that when subject pilots were flying in AI mode, they had less head roll relations to an aircraft roll than they did when they were flying in either visual or non-flying mode.

 

 

 

 

 

 

 

            regression coefficient

                    

 

            Figure 20.-Regression coefficient (ordinate) for aircraft bank angle  vs.    head roll angle. 

           

            Each bar shows 95 % t-test confidence limits for coefficient (B) for            Attitude Indicator mode, visual mode, and non-flying mode.

            Subjects have significantly less head roll in Attitude Indicator mode.         

            This graph corresponds to Figure 21.  The ANOVA analysis presented     in Table 7 also dictates that Attitude Indicator and non-flying mode are             most separated among three flight modes.  The values for (upper limit,      B, lower limit) are:

 

                                    AI mode                      (-0.114, -0.127, -0.140)

                                    visual mode                 (-0.147, -0.163, -0.179)

                                    non-flying mode          (-0.164, -0.183, -0.202).

 

 

 

 

Figure 21.-Regression analysis for head roll angle vs. aircraft roll angle.

 

The 95 % confidence band for Attitude Indicator, and linear regression lines for visual/non-flying mode are shown.  Negative values for angle mean roll to the left.  Linear regression line for Attitude Indicator mode is significantly different from that of visual mode or non-flying mode.  This graph corresponds to Figure 20.

 

5.7       ANOVA analysis

 

 

            Analysis of Variance (ANOVA) test was applied to examine the effects of subject or flight mode difference.  Absolute (sign-less) values of head roll angle data were used for calculating ANOVA table because mean of head roll for a subject is close to zero due to the symmetrical value distribution over aircraft bank angle  (Table 6).   There was a difference in mean head roll angle among flight modes (p = 0.0860).

            As a post-hoc test for the effect of flight mode on head roll angle, Schefféfs procedure was performed.  There was a difference between the Attitude Indicator flight mode and the non-flying flight mode (p = 0.0920), i.e. when subjects were working as non-flying pilot, their head roll around the head x-axis due to aircraft bank was larger than when they were using an Attitude Indicator as one of spatial orientation cues.

 


Table 6.-ANOVA table for subject and flight mode.

 

effect

df effect

MS effect

df error

MS error

F

p-level

subject

9

169

180

13.8

12.2

0.0000

flight mode

2

34.3

180

13.8

2.49

0.0860 *

subject x flight mode

 

18

 

10.7

 

180

 

13.8

 

0.776

 

0.727

 

 

Number of subjects was 10.  Flight modes were Attitude Indicator, visual, and non-flying.  Absolute (sign-less) value of the head roll angle was used.  Subject and flight mode both were found to be influential on the magnitude of head roll angle.  There was no significant combined interaction effect of the two factors.

 

 

 

 

Table 7.-Post-hoc test for head roll angle difference among flight modes.

 

Schefféfs test

p-level

Attitude Indicator

mean = 3.53

visual

mean = 4.43

non-flying

mean = 4.91

Attitude Indicator

0.366

0.0920 *

visual

0.740

non-flying

 

 

Absolute (sign-less) values of the head roll angle were used for the mean head roll angle calculation.  There was a considerable (*p = 9.2 %) statistical difference between effects of Attitude Indicator and non-flying mode on head roll angle.  This result is the same as regression analysis as shown in Figure 20, which means that Attitude Indicator and non-flying mode are separated farthest among the three flight modes.

 

5.8       t-test

 

            As the third statistical measure used for comparison among three modes of flight, t-test matrix was calculated (Table 8).  As found by regression analysis, mean head roll angle for each aircraft roll (bank) angle was significantly larger in visual mode than that in Attitude Indicator mode in left turn.  However, in right turn this difference was not found significant by t-test.

             In the right turn, the t-test indicated that mean head roll angle is larger in non-flying mode than that in visual mode.  This was not seen in either the regression or ANOVA analyses.  There was no significant difference between these modes in left turn as indicated by t-test.

            In right turn, there was a possible difference in mean head roll, as indicated by regression and ANOVA analysis, between non-flying and AI mode (p = 0.11, 0.11, 0.28).

            Because of a notable discrepancy between the direction of the turn (roll) of the aircraft in comparison among flight modes, t-test by itself was not sufficient to derive a conclusion.  A reference to the directional variation shown in Table 11 in view, these directional effects needs careful evaluation.
Table 8
.-A matrix of t-test for difference in head roll among flight modes at each aircraft roll (bank) angle.

 

aircraft

 bank angle

   two-tail t-test for head roll angle        (n = 10 ) 

p level          (* p < 0.05)

 

 

flight mode

 

AI

visual

non-flying

 

 

 

 

 

 

left

turn

 

 

45 deg

Attitude Indicator

0.0026 *

0.048 *

visual

0.67

 

non-flying

 

 

 

30 deg

Attitude Indicator

0.029 *

0.39

 

visual

0.57

 

non-flying

 

 

 

15 deg

Attitude Indicator

0.0077 *

0.27

 

visual

0.12

 

non-flying

 

 

 

 

 

 

 

right

turn

 

 

45 deg

Attitude Indicator

0.96

0.11

visual

0.040 *

 

non-flying

 

 

 

30 deg

Attitude Indicator

0.29

0.15

 

visual

0.11

 

non-flying

 

 

 

15 deg

Attitude Indicator

0.51

0.28

 

visual

0.11

 

non-flying

 

 

 

Absolute (sign-less) values of the head roll angle were used for the mean head roll angle calculation.   The most significant difference was left turn visual vs. AI mode (the former the larger, p  0.029).  Then right turn non-flying vs. visual mode (p  0.11) and right turn non-flying vs. AI mode (p  0.28) followed.  It is notable that there was considerable difference between left and right turn.  In right turn, there was no difference (0.96  p  0.29) in visual vs. AI mode.  Conversely, there was no difference (0.67  p  0.12) in non-flying vs. visual mode in left turn.  Bank (roll) angle of the aircraft did not have much influence in these trends.   Consult Table 5 for mean values.
5.9       Comparison between the direction of aircraft roll (left or right)

 

            The difference in mean head roll angle by the direction of the aircraft roll (turn) was statistically analyzed by two-tail t-test.  Table 9 shows the complied data from all three flight modes.  Except at bank angle of 15, there was a significant difference in mean head roll angle value between the left and the right direction of aircraft turn.  The difference in the mean head roll was 1.5 and 2.1.  These angular values are approximately 30 % of the amplitude of head roll during turns. 

            The experimental condition differs, in terms of right or left, in aircraft seating (subjects took a left seat of the two in the frontal row in the airplane).  It brought an asymmetric pilot view through windshields for outside visual cues (Figure 22).  Hence it affected the pattern of visual vigilance in all three flight modes.

            Although the window view was asymmetrical in the right and the left, it did not present equal effect on three modes of flight.  The left-right directional difference in mean head roll angle found in visual mode (Table 11) was not observed in the other two modes (Figure 19, Figure 28).

            The difference found in compiled data in Table 9 is thought to have resulted from visual flight mode part of data.


 

 

 

 

 

 

 

Figure 22.-Field of view for Cessna 172L.

 

Angular dimensions measured from the eyes (nasion) of a pilot 172 cm in height in Cessna 172L research airplane.  Drawing is not to scale.  Side windows are weakly affecting peripheral vision because of its rear position.  Field of view in pitch (vertical) is limited in this airplane type.  Field of view data has not been measured by the manufacturer of the airplane.
Table 9.-Comparison of head roll angle between left and right aircraft roll, all flight modes.

 

all flight modes

 n = 30

head roll mean

[deg]

head roll S.D.

[deg]

t-test (two-tail)

p level

 

15 deg bank

left

3.4

3.1

 

p = 0.35

right

2.8

2.9

 

 

30 deg bank

left

5.9

4.1

* left > right

p = 0.049

right

4.4

4.1

 

 

45 deg bank

left

7.6

5.8

* left > right

p = 0.010

right

5.5

5.2

 

 

 

Absolute (sign-less) values of the head roll angle were used for the mean head roll angle calculation.  The amount of head roll was significantly greater in left turns, by 1.5 (5.9 - 4.4) at 30 bank and by 2.1 (7.6 - 5.5) at 45 bank.  There are no significant difference in the variance of head roll.  Table 10, Table 11, and Table 12 are presented for each mode of flight.

 

 

Table 10.-Comparison of head roll angle between left and right aircraft roll, Attitude Indicator flight mode.

 

Attitude Indicator mode          n = 10

head roll mean

[deg]

head roll S.D.

[deg]

t-test (two-tail)

p level

 

15 deg bank

left

2.2

2.3

 

p = 0.74

right

2.4

1.5

 

 

30 deg bank

left

4.9

4.3

 

p = 0.34

right

4.1

3.7

 

 

45 deg bank

left

5.5

5.2

 

p = 0.56

right

4.8

3.6

 

 

 

Absolute (sign-less) values of the head roll angle were used for the mean head roll angle calculation. Although there was a bias in Attitude Indicator (pilots rolled the aircraft shallower to the left by 5 because of bias error in AI), there was no significant difference in the amount of head roll by the direction of the aircraft roll (turn).

Table 11.-Comparison of head roll angle between left and right aircraft roll, visual flight mode.

 

visual mode

n = 10

head roll mean

[deg]

head roll S.D.

[deg]

t-test (two-tail)

p level

 

15 deg bank

left

4.9

3.9

* left > right

p = 0.040

right

2.0

2.0

 

 

30 deg bank

left

6.8

4.4

* left > right

p = 0.0074

right

3.3

2.0

 

 

45 deg bank

left

9.0

5.8

* left > right

p = 0.016

right

4.8

4.8

 

 

 

Absolute (sign-less) values of the head roll angle were used for the mean head roll angle calculation.  The amount of head roll was significantly greater in left turns, by 2.9 (4.9 - 2.0) at 15 bank; by 3.5 (6.8 - 3.3) at 30 bank; by 4.2 (9.0 - 4.8) at 45 bank.  The variance of head roll seems to be greater in left aircraft roll than in right roll, although not to be tested statistically.

 

 

 

 

Table 12.-Comparison of head roll angle between left and right aircraft roll, non-flying flight mode.

 

non-flying mode

n = 10

head roll mean

[deg]

head roll S.D.

[deg]

t-test (two-tail)

p level

 

15 deg bank

left

3.0

2.7

 

p = 0.45

right

3.8

4.3

 

 

30 deg bank

left

6.0

3.8

 

p = 0.91

right

5.8

5.8

 

 

45 deg bank

left