HEAD ALIGNMENT OF = THE

LIST OF FIGURES

Figure = 1.-Computer=20 graphics attitude display. =20 4

Figure = 2.-Variation in=20 Attitude Indicator design. = 4

Figure = 3.-View of AI=20 and the horizon. =20 5

Figure = 4.-Head roll of=20 F-16 pilot in 9 G turn. =20 9

Figure = 5.-Research=20 airplane. Cessna C172L = Skyhawk,=20 fixed-gear, 4-place. =20 12

Figure = 6.-Instrument=20 layout of the research airplane. &nbs= p; =20 12

Figure = 7.-Visual=20 Flight Rule 1:500,000 sectional chart for the flight test air = space. = 13

Figure = 8.-Videocamera=20 mounted on a headset. =20 16

Figure = 9.-Data=20 acquisition system diagram. = &nbs= p;=20 16

Figure = 10.-Dimension=20 of videocamera setting in the research airplane. &nbs= p; =20 17

Figure = 11.-Calibration=20 of videocamera angle. =20 18

Figure = 12.-Cockpit=20 picture in analysis. = 18

Figure = 13.-Head=20 alignment of a pilot in 45=81=8B bank turn to the left. =20 19

Figure = 14.-Head roll=20 angle around head x-axis, in Attitude Indicator mode of flight. = 30

Figure = 15.-Head roll=20 angle around head x-axis, in vidual flight mode. 30

Figure = 16.-Head roll=20 angle around head x-axis, in non flying flight mode. =20 30

Figure = 17.-Pilot head=20 roll around head x-axis during aircraft turn, in Attitude Indicator mode = of=20 flight. &nbs= p; =20 32

Figure = 18.-Pilot head=20 roll around head x-axis during aircraft turn, in visual mode of = flight. = 33

Figure = 19.-Pilot head=20 roll around head x-axis during aircraft turn, in non-flying mode of = flight. &nbs= p; =20 34

Figure = 20.-Regression=20 coefficient (ordinate) for aircraft bank angle vs. head roll angle. &nbs= p;=20 36

Figure = 21.-Regression=20 analysis for head roll angle vs. aircraft roll angle. &nbs= p;=20 = 37

Figure = 22.-Field of=20 view for Cessna 172L. 43

Figure = 23.-Scattergram=20 of subject age vs. head roll angle, left aircraft roll. =20 = 47

Figure = 24.-Scattergram=20 of subject age vs. head roll angle, right aircraft roll. = 48

Figure = 25.-Scattergram=20 of subject flight time vs. head roll angle, left aircraft roll. =20 49

Figure = 26.-Scattergram=20 of subject flight time vs. head roll angle, right aircraft roll. = 50

Figure = 27.-Head roll=20 angle around head x-axis of each subjects. = 51

Figure = 28.-Time course=20 of aircraft and head roll around their x-axis, Attitude Indicator flight = mode.=20 &nbs= p; =20 53

Figure = 29.-Time course=20 of aircraft and head roll around their x-axis, visual flight mode 54

Figure = 30.-Time course=20 of aircraft and head roll around their x-axis, non-flying mode. 55

Figure = 31.-Head roll=20 in ground turn. =20 57

Figure = 32.-Head roll=20 during a 180=81=8B course reversal on the ground, time series. 58

Figure = 33.-Head roll=20 during a 180=81=8B course reversal on the ground. = 59

Figure = 34.-The=20 relation between elapsed time and aircraft heading for Figure 32 and = Figure 33.=20 60

Figure = 35.-Head=20 position of a passenger in 90=81=8B bank flight. 63

Figure = 36.-Automobile=20 driver=81fs head alignment during roll of vehicle around its x-axis = (longitudinal=20 axis). 66

Figure = 37.-Head=20 alignment of an automobile driver. 67

Figure = 38.-Motorcycle=20 rider and passenger=81fs head alignment in turn. 68

Figure = 39.-Latest Head=20 Up Display symbols. &nbs= p;=20 79

Figure = 40.-Cervical=20 spine alignment on head roll. 81

Figure=20 41.-Nomenclature for axes. &nbs= p; =20 92

&nbs= p; = ; = =20 LIST OF=20 TABLES

Table 1.-Terms equivalent = to =81emoving=20 horizon=81f and =81emoving aircraft=81f. = 7

Table 2.-Profile of pilot=20 subjects. 11

Table 3.-Ground simulator = study=20 result. 24

Table 4.-Head roll with = body lean,=20 subject #9. =20 28

Table 5.-Result of pilot = head roll=20 angle around head x-axis during aircraft turn. 31

Table 6.-ANOVA table for = subject and=20 flight mode. 39

Table 7.-Post-hoc test for = head roll=20 angle difference among flight modes. 39

Table 8.-A matrix of t-test = for=20 difference in head roll among flight modes at each aircraft roll (bank) = angle.=20 = 41

Table 9.-Comparison of head = roll angle=20 between left and right aircraft roll, all flight modes. =20 44

Table 10.-Comparison of = head roll angle=20 between left and right aircraft roll, Attitude Indicator flight mode. = =20 44

Table 11.-Comparison of = head roll angle=20 between left and right aircraft roll, visual flight mode. 45

Table 12.-Comparison of = head roll angle=20 between left and right aircraft roll, non-flying flight mode. 45

Table 13.-Regression = coefficients from=20 simulator and flight study. = 76

Table 14. +Gz values for = aircraft roll=20 angles. =20 85

Table 15. - Flight maneuver = sequence=20 for subject #8. =20 93

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

&nbs= p; = ; = =20 ACKNOWLEDGEMENTS

=20 I would like to extend my sincerest thanks to the following = people for=20 their assistance in the undertaking of this study:

Stanley R. Mohler, M.D., Anthony J. = Cacioppo,=20 Ph.D., Satya P. Sangal, Ph.D., Robin E. Dodge, M.D., and Frederick R. = Patterson,=20 Ph.D.

=20 I am grateful to = Terry=20 Taddeo, M.D. and Fumi Shimada for their help in manuscript=20 preparation.

&nbs= p; = ; =20 1. =20 INTRODUCTION

=20 Spatial disorientation is still a pilot killer. Spatial disorientation is = associated=20 with the experiencing of an orientational illusion for pilots = [Gillingham=20 1985]. Loss of = situational=20 awareness has been a major concern in military aviation, where one = encounters a=20 wide aircraft aerodynamic envelope (acceleration and velocity) [Barnum = 1968,=20 Cheung 1995]. = Requirements for=20 close formation flying under poor weather conditions is another factor = related=20 to this phenomenon. = Civilian=20 aviation has not placed much emphasis on this pilot-system limitation = [Kirkham=20 1978, Johnson 1989, AOPA 1993]. = Is=20 it a problem only for high-performance fighter = pilots?

=20 Recently spatial disorientation was identified as a link in the = causal=20 chain of factors related to a major US air carrier crash. A DC-9 jetliner had a = collision with the=20 ground because of an encounter with a microburst and the pilots=81f = subsequent loss of situational awareness = due to=20 somatogravic illusion [NTSB =20 1994]. The flight = crew=20 became disoriented during the transition from Visual Meteorological = Conditions=20 to Instrumental Meteorological Conditions.

=20 What type of computer graphic display, head-up display, or = head-mounted=20 display might facilitate spatial orientation? What should be the contents of = a=20 training syllabus against disorientation? =20 Is our understanding of its pathophysiology sufficient to permit = the=20 design of truly better instruments and training?

=20 In aerospace medicine textbooks, there has been no quantitative=20 description about natural body and head alignment of pilots other than = in a=20 straight and level flight. = Only=20 recently this was challenged by two ground simulator studies [Patterson = 1995A,=20 Smith 1995]. Some flight=20 instructors teach students that keeping their head and body straight = along the=20 body z-axis (longitudinal axis, Figure=20 41) is the proper body alignment. =20 But the simulator study found that pilots laterally deflect their = heads=20 during turning maneuvers.

=20 Positional alignment of head and body during flight maneuvers is = a=20 significant limiting factor for the design of instruments and cockpit=20 layout. The latest = designs of=20 Head-Up Displays or Head-Mounted Displays are more sensitive to this = geometry=20 because of their limited angle of view. =20 In order to view some military head-up displays, the eyes must be = kept=20 within an 8 x 13 cm (3 x 5 inch) field. =20 These limits are easily exceeded if pilots roll their head around = their=20 head x-axis (deflect the head laterally).

=20 The physiological dynamics of pilot head motion during flight has = yet to=20 be investigated.

&nbs= p; = ; =20 2. =20 BACKGROUND

=20 Actively controlled human flight began with hang gliders, under = visual=20 flight condition. The = Wright=20 Brothers from Dayton, Ohio began controlled, powered flight after their=20 extensive experiments with gliders. =20 The next breakthrough, was the invention of the aircraft=81fs = attitude=20 display.

=20 Prior to the emergence of the apparatus, there was an interesting = instrument arrangement used by Charles A. Lindbergh for his solo = transatlantic=20 flight in 1927. Since his = forward=20 view was blocked by a fuel tank, he used a periscope to provide a visual = reference [Roscoe 1966]. = Although=20 he is said to have used forward slipping during approach to gain a = better view=20 of the runway, the periscope deprived him of peripheral vision, which is = important for pilots [Kochhar 1978].

=20 Based upon his design of a gyroscopic stabilizer for ships, Elmer = Sperry,=20 Jr. [Laboda 1995], in 1910, extended the technology by developing a = gyroscope=20 for use by pilots for determining aircraft attitude. The Sperry Artificial Horizon = allowed=20 Lt. James H. Doolittle to fly his NY-2 Navy trainer airplane = =81eblind=81f on 24=20 September 1929. This = historic=20 apparatus is on display at the US Air Force Museum, Dayton, Ohio.

Figure 1.-Computer graphics attitude=20 display.

A display of a Fokker F-100 = jetliner. It is the latest design in = use, but=20 stays with the concept of a stationary aircraft symbol with a moving=20 horizon.

Figure 2.-Variation in Attitude Indicator=20 design.

This AI in a 1966 Piper = PA30B twin=20 piston-engine airplane has a bank pointer that moves with the horizon = bar,=20 instead of with the miniature airplane. Many AI=81fs of this design are = still in=20 use today. This kind of = design=20 variation is also seen in VOR (Very High Frequency Omni Range) = indicators.Figure 3.-View of AI and the = earth=20 horizon.

The Attitude Indicator = (arrow) and the=20 earth horizon seen from cockpit of a CH2000 single engine airplane. The roll angle of the aircraft = is 64=81=8B to=20 the left. This picture is = aligned=20 to the page so that it looks natural to the reader, while actually it = differs=20 from the retinal image of the pilots in the cockpit because of the = limited=20 motion of the head in flight.

[ AOPA Pilot, 36(12),1993: = 47=20 ]

=20 There is a speculation that Lindbergh=81fs success with the = periscope may=20 have affected the design of the artificial horizon (now called the = Attitude=20 Indicator, Figure 1, Figure = 2). All operational attitude = indicators,=20 except for those of Russian design, use =81emoving horizon=81f symbolic = design. The horizon bar (Figure 1) resembles that of a = short=20 portion of the earth horizon as if seen through a periscope (Figure = 3).

=20 Peripheral displays, such as the para-visual director, peripheral = command=20 indicator, HOVERING display, and the Malcolm horizon stimulate = peripheral vision=20 to provide aircraft attitude information [Stokes 1988]. They have proven to be = relatively=20 effective despite degraded visual acuity associated with peripheral = vision. Visual acuity in Snellen=81fs = fraction=20 decreases from 1.0 in the visual center to 0.2 at 10=81=8B off center, = 0.1 at 20=81=8B,=20 and 0.07 at 30=81=8B [Westheimer 1992].

=20 How can we present attitude information to maximize foveal = vision? Although the options are many, = modern=20 Russian fighters use an attitude display whose miniature airplane, = instead of a=20 horizon bar, rolls.

=20 In the past, no commercial competition was seen between the = =81emoving=20 horizon=81f and =81emoving airplane=81f display. =20 This is probably due to the initial success of the Sperry = artificial=20 horizon and the comprehensive analogy of periscopic view (=81ecut = out=81f earth=20 horizon appears in an Attitude Indicator) [Poppen 1936, Roscoe = 1966]. Other equivalent terms, which = are often=20 confusing, are summarized in Table=20 1. It is worth noting = that an=20 integrated display which changes from =81emoving aircraft=81f to = =81emoving horizon=81f for=20 roll-in has been devised [Fogel 1959, Roscoe = 1975].

Table 1.-Terms equivalent to =81emoving = horizon=81f and =81emoving=20 aircraft=81f.

=20 moving horizon &nbs= p; = ; = =20 moving airplane

=20 inside-out &nbs= p; = ; = &= nbsp; =20 outside-in =20

=20 fly-to &nbs= p; = ; = &= nbsp; &n= bsp; =20 fly-from

=20 moving card or tape &nbs= p; = ; =20 moving pointer

=20 earth referenced &nbs= p; = ; = =20 aircraft referenced

=20 aircraft stabilized &nbs= p; = ; = =20 space stabilized

=20 in aircraft coordinates &nbs= p; = ;=20 in earth coordinates

=20 modified from [Johnson 1972]

=20 A study by the Federal Aviation Administration Civil Aeromedical=20 Institute with a Beechcraft T-34 [Hasbrook 1973] compared the two types = of=20 display and concluded that:

&nbs= p; =20 Data from many of these = earlier=20 studies suggest that the outside-in (moving- &nbs= p; =20 aircraft) indicator provides better pilot performance: but this in-flight study &nbs= p; =20 fails, in the main, to show any such well defined, overall = advantage.

=20 Despite pioneer efforts, it was not until 1930 that military = pilots were=20 taught that the instruments should be used as source for flight = information and=20 that they should not fly by the =81gseat of their pants=81h [Malcolm = 1984]. This is not widely understood = among=20 today=81fs leisure pilots.

=20 When one questions the dynamics associated in comparing a = =81emoving=20 horizon=81f with =81emoving airplane=81f, the answer is ambiguous. Missing is the recognition of = natural=20 behavior of the pilots. = What is the=20 natural position of the head relative to the = cockpit?

=20 When asked if the head moves during flight, most pilots will = answer=20 =81eno=81f. Only a few = pilots admit that=20 they roll their head. = Even=20 demonstration team members of the US Navy [Patterson 1995A] and the US = Air Force=20 (Figure 4) were observed = to roll=20 their heads around the head z-axis (tilt their head) in a direction = opposite to=20 the center of the turn in visual flight. Pilots prefer to view a = picture as=20 if aligned to the earth horizon rather than to the cockpit (Figure 3). The only literature about head = motion in=20 flight, which surfaced, gave a general indication that subject pilots = kept their=20 head z-axis normal to the ground [Hasbrook 1973].

=20 Recent simulator sutdies revived this old but unanswered question = [Patterson 1995A, Smith 1995]. = If=20 pilots are rolling their heads, is a =81emoving horizon=81f better = adapted to prevent=20 roll reversal (mistakenly initiate roll to the opposite direction)? What if the display moves with = the head=20 instead of being fixed to the cockpit? =20 What is the natural motion of the head that should be assumed in = a new=20 display design? Which = attributes of=20 display design should be adopted?

Figure 4.-Head roll of F-16 pilot in 9 G=20 turn.

This U.S. Air Force = Thunderbirds=20 demonstration team member is quickly rolling into 9 G turn. The roll (bank) angle of = aircraft in=20 this picture is 64=81=8B (ÐBOH=81f). =20 His head is rolled to the right around head x-axis (laterally = deflected=20 to the right) with an angle of 15=81=8B (90=81=8B - ÐAOH) relative to the cockpit. Cockpit level is represented = by line=20 HH=81f. Because the body = is leaned to=20 the right with an angle of 3=81=8B (ÐHOS), the angle of head roll relative to = the body=20 z-axis is 12=81=8B (15=81=8B - 3=81=8B). There is=20 a slight yaw of the head to the left, which does not affect more than = 1=81=8B for=20 this head roll angle relationship to the cockpit. A transient maximum roll of = the head of=20 24=81=8B relative to the cockpit was observed when roll of the aircraft = was at 60=81=8B=20 (just before this picture). = After=20 this picture, roll of aircraft was kept 82=81=8B to 85=81=8B to keep 9 G = turn, which=20 theoretically requires 83.6=81=8B of bank [ cos^{- 1} (1/9) = ]. Head roll angle was kept = approximately=20 6=81=8B to the right relative to the cockpit while 9 G 360=81=8B turn = was=20 continued.

=20 The purpose of this research is to determine how pilots (flying = and=20 non-flying) align their heads during actual flights in a general = aviation=20 aircraft.

=20 It is hypothesized that general aviation pilots in visual flight = rule=20 (VFR) conditions align their heads with the horizon of the earth for = visual=20 orientation, which causes head rotations around the x-axis of the = head. This study examines this = hypothesis by=20 recording and analyzing pilot head motion during actual VFR flight in a = general=20 aviation aircraft.

=20 To supplement the flight test, head motion data were collected = during the=20 ground taxing phase of a flight.

A total of 10 = civilian=20 volunteer pilots holding current FAA medical certificate (either class 2 = or 3)=20 and FAA pilot rating (either private, commercial, or Air Transport = Pilot)=20 participated (Table = 2).

The protocol for=20 participation by human = subjects was=20 approved, prior to flight test, by the Office of Research and Sponsored=20 Programs, Wright State University.

All subjects held current FAA = certificate=20 for the research airplane. = All 10=20 subjects were male with an age rage of 22 - 47 years and airplane flight = tie of=20 80 - 4000 hours. None had = military=20 flying experience.

Figure = 5.-Research=20 airplane. Cessna C172L = Skyhawk,=20 fixed-gear, 4-place.

Attitude = Indicator type is=20 EDO-AIRE 5000F-6. The = miniature=20 airplane of the AI moves with the bank pointer, which is the standard in = U.S. at=20 present. This picture was = taken=20 from pilot eyepoint with a comparable field (35 mm film, f =3D 35 mm).

Figure. = 7.-Visual Flight=20 Rule 1:500,000 sectional chart for the flight test air space. The area marked by arrows was = used for=20 the research flights. The = meteorological condition was better than VFR minimum; Dayton visibility = was 10=20 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=20 Ground Level, more than 1000 feet below the clouds. All flights were completed = within=20 daylight hours.
4.2 =20 Aircraft

&nbs= p; =20 The aircraft used for this study was a 150 horse power, = single-engine=20 land, fixed-gear, 4-place general aviation utility airplane (Figure 5, Cessna C172L, = N7116Q, based at Brookville Air Park, = airport=20 code I62). All = subjects were=20 volunteers familiar with this airplane type.

=20 =20 The research airplane was equipped with a set of standard = Instrument=20 Flight Rule instruments, which includes an attitude indicator (attitude=20 gyro). Figure 6 shows instrument = panel=20 arrangement. This picture = corresponds to the pilot=81fs view in flight. =20 Attitude Indicator is located at top center of the =81eT=81f = layout for=20 cardinal Instrument Flight Rule instruments.

&nbs= p; =20 The airplane took off from Brookville airport and returned. Flight maneuvers took place in = a=20 practice area approximately 15 km southwest of the airport (Figure 7). Because of Dayton jet traffic, = flight=20 altitude was kept below 4,000 feet Above Ground Level. The altitude flown was between = 1,500 and=20 3,500 feet AGL, and was at least 1,000 feet below the clouds.

&nbs= p; =20 Visibility reported at Dayton International Airport at the time = of=20 flights was better or equal to 10 statute miles for 9 subjects; 7 = statute miles=20 for subject #9. Surface = wind at=20 Dayton was reported at 6 to 15 knots, generally from southwest. There was a slight turbulence = for=20 subject #2 due to thermals. = Other=20 subjects had no turbulence. = Surface=20 temperature at Dayton International Airport (308 m above Mean Sea Level) = was=20 between -4 to +11 =81=8BC. = All flights=20 were completed within daylight hours under Visual Meteorological = Condition. Weather was at all times above = federal=20 Visual Flight Rule minimums.

&nbs= p; =20 The subjects were seated in the left seat of the airplane. They wore a small, = light-weight=20 (70 g) CCD camera(Sony CCD-MC1, f=3D3.6 mm) on a headset (Figure 8 ). Video recording was made = during taxi and=20 flight with a NTSC-VHS portable video cassette recorder (Panasonic = AG-170).

&nbs= p; =20 The center of the=20 videocamera field was aimed at the center of a white bar, 530 mm in = length, located on the top of the = instrument=20 panel. The horizon of the = earth was=20 visible in the camera field (Figure=20 10). Alignment of the = camera=20 relative to the earth horizon was calibrated with a grid pattern and a=20 protractor while on the ground (Figure=20 11). Angular readings = were=20 entered into computer by = keyboard=20 (Figure = 9).

&nbs= p; =20 Subjects=81f head = motion=20 relative to the cockpit were analyzed from the recorded video = picture. Head roll angle around the = head x-axis=20 was measured on a TV monitor screen with a protractor, frame by frame = (Panasonic=20 AG-1970 video cassette recorder and Sony SSM-2010 monitor) (Figure 12). In-flight = pictures were=20 compared to a calibrated video picture recorded during the preflight = phase on=20 the ground.

SONY CCD-MC1 = lightweight=20 videocamera was mounted onto David Clark H10-13.4 aviation headset. The head pad of the headset = was removed=20 to minimize height. = Cables were not=20 interfering with pilot head motion. =20 Line-of-sight of the camera had an angle range of 10 - 15=81=8B = relative to=20 horizon when a pilot is in the seat (Figure = 10).

Figure = 9.-Data=20 acquisition system diagram. = The=20 video tape pictured with a portable videorecorder was manually analyzed = and the=20 result was entered to computer through keyboard.

Figures are shown = in=20 mm. The height of the = subjects=20 ranged from 172 cm to 190 cm, which varied the line-of-sight angle of = the=20 videocamera from 10˚ to 15˚ relative to horizon. This range of camera angle did = not cause=20 rotational skew of the cockpit image more than 1˚. =

Angle of the head = of a=20 pilot and reference white bar on instrument panel is in calibration with = a=20 protractor mounted on the head, a grid, strings and=20 weights.

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