DOT/FAA/AM-00/31

Kevin W. Williams

Civil Aeromedical Institute

Federal Aviation Administration

Oklahoma City, Oklahoma 73125

October 2000

Final Report

This document is available to the public

through the National Technical Information

Service, Springfield, Virginia 22161.

Impact of Aviation

Highway-in-the-Sky

Displays on Pilot

Situation Awareness

Office of Aviation Medicine

Washington, D.C. 20591

U.S. Department

of Transportation

Federal Aviation

Administration
NOTICE

This document is disseminated under the sponsorship of

the U.S. Department of Transportation in the interest of

information exchange. The United States Government

assumes no liability for the contents thereof.
i

Technical Report Documentation Page

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

DOT/FAA/AM-00/31

4. Title and Subtitle 5. Report Date

Impact of Aviation Highway-in-the-Sky Displays on Pilot Situation October 2000

Awareness 6. Performing Organization Code

7. Author(s) 8. Performing Organization Report No.

Williams, K.W.

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)

FAA Civil Aeromedical Institute

P.O. Box 25082

Oklahoma City, OK 73125 11. Contract or Grant No.

12. Sponsoring Agency name and Address 13. Type of Report and Period Covered

Office of Aviation Medicine

Federal Aviation Administration

800 Independence Ave, S.W.

Washington, DC 20591 14. Sponsoring Agency Code

15. Supplemental Notes

This work was performed under task AM-A-00-HRR-519.

16. Abstract

Thirty-six pilots were tested in a flight simulator on their ability to intercept a pathway depicted on a

highway-in-the-sky (HITS) display. While intercepting and flying the pathway, pilots were required to watch

for traffic outside the cockpit. Additionally, pilots were tested on their awareness of speed, altitude, and

heading during the flight. Results indicated strong practice effects for a pilot’s ability to intercept the pathway

and that the presence of a flight guidance cue significantly improved performance. The ability to spot traffic

was more affected by task difficulty than by display appeal. New display concepts are needed for supporting

secondary flight information present on the HITS display. Recommendations for training and use of HITS

displays are given, along with recommendations for display enhancements to support situation awareness.

17. Key Words 18. Distribution Statement

Document is available to the public through the

National Technical Information Service,

Situation Awareness, Pathway Displays, Highwayin-the-Sky Displays, Cockpit Displays, Perspective

Displays, Applied Psychology Springfield, Virginia 22161

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price

Unclassified Unclassified 13

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

iii

ACKNOWLEDGMENTS

The author thanks Dr. Tom Nesthus and Jared Fasion for collecting the eye-gaze data,

Howard Harris for recruiting and scheduling participants, Barry Runnels for maintaining the

Advanced General Aviation Research Simulator, and Tom Philps and Deborah Thompson for

their assistance in reducing the eye-gaze data.

1

IMPACT OF AVIATION HIGHWAY-IN-THE-SKY DISPLAYS

ON PILOT SITUATION AWARENESS

INTRODUCTION

Recently, a great deal of attention has been given to

the incorporation of a Highway-In-the-Sky (HITS)

display as the primary cockpit flight display. A HITS

(also called “pathway”) display provides course guidance to the pilot using a perspective view of a path

through the air. Figures 1a and 1b provide examples

of typical HITS displays. Interest in this type of

display is not new, originating in the 1950s with the

Joint Army-Navy Instrumentation Program (see

Warner, 1979). Until recently, however, the implementation of a HITS display was too expensive for

most aircraft owners.

Two technological breakthroughs have made it

feasible for HITS systems to become a reality in most

aircraft cockpits. One of these is an affordable Global

Positioning System (GPS) receiver that provides realtime, accurate aircraft position information. The

second breakthrough is the production of inexpensive, yet powerful, graphic display systems that are

capable of providing real-time HITS depictions in

the cockpit. Both of these technologies make HITS

displays feasible for general aviation (GA) aircraft.

Given the availability of more affordable HITS displays, the Advanced General Aviation Transport Experiments (AGATE) consortium, which is dedicated

to the specification of a next-generation GA aircraft,

has mandated the incorporation of the display as its

top priority in judging the success of its program.

Although HITS displays have the potential to

replace many of the older display formats that have

been the mainstay of GA aircraft, the exact purpose

and use of a HITS display is still being debated.

Research is required to answer critical questions

regarding the effectiveness and safety of these displays. One of these questions is how well a pilot

maintains situation awareness (SA) while flying with

a HITS display.

Problems with SA have been implicated as a leading causal factor in both military aviation mishaps

(Endsley, 1997) and accidents among major air carriers (Endsley, 1995). The current study was designed to look at the effect that a HITS display would

have on pilot SA. In particular, three types of SA were

considered in the study.

a. b.

Figure1. a) Goal post pathway design showing pathway, airspeed, altitude, and heading indications. b) Paving

stone pathway design.
2

The first type of SA involved knowledge of the

position of the intended flight path, relative to the

current position of the aircraft. The HITS display

depicts a volume of space in the real world and the

position of the aircraft in relation to this volume of

space. Endsley (1997) refers to this type of SA as

Spatial/Temporal SA. Wickens (1995) suggests that

one of the major deficiencies of three-dimensional

(D) perspective displays, of which the HITS display

is one example, is the “ambiguity of position estimate

along the line of sight or viewing vector of the

display” (p. K2-9). When approaching the pathway

from the outside, there are very few visual cues to

indicate distance from the pathway. In this situation,

some cues, such as binocular disparity and textural

gradients, are unavailable. Other cues, such as relative size, can be distorted. The ability of the pilot to

maintain awareness of the position of the aircraft

relative to the pathway is important. The present

study was designed to provide information on the

effects that different pathway formats and guidance

cues have on the ability of pilots to establish their

aircraft on the pathway.

A second type of SA addressed here is the ability to

locate other aircraft. Referred to as tactical SA

(Endsley, 1997), the need to maintain awareness

outside of the cockpit is critical to flight safety. The

impact of new flight displays and controls on the

amount of time spent looking outside of the cockpit

has been studied primarily within the context of an

airline cockpit (e.g., Damos, John, & Lyall, 1999;

Rudisill, 1994; Wiener, 1993). In those studies, the

complexity of interacting with the display was shown

to be the main driver of how long and how often the

pilot focused attention outside of the cockpit. For

HITS displays, previous observations of pilots using

a head-down HITS display had suggested that significant proportions of flight time were spent viewing the HITS to the exclusion of other piloting

activities. Therefore, the ability of the pilot to maintain

awareness outside of the cockpit was examined in the

current study by having the pilot scan for aircraft

traffic while acquiring and flying the pathway.

A final type of SA addressed in the current study is

knowledge of secondary information available on the

HITS display. Information about the current airspeed, aircraft heading, and altitude is present in the

display, but there is a question of whether such

information is necessary and what circumstances

would make the information necessary. Researchers

have examined pilot information requirements

(Schwaneveldt, Lamonica, Tucker, Nance, &

Beringer, 2000), but that research did not consider

the effect that a HITS display would have on those

requirements. Of interest in the current study is how

aware pilots are of the secondary information available on the HITS display and whether they use that

information during flight.

METHODS

Participants

Thirty-six pilots, holding at least a current private

pilot certificate, were recruited locally. Information

was collected regarding each participant’s education

level, gender, flight experience, and age. Flight experience averaged 830 hours. Twenty-one of the 36

pilots (58%) held an instrument rating. The average

age of the pilots was 37, ranging from 19 to 67 years.

Median pilot age was 30.5 years.

Facilities and Equipment

Data collection was performed using the Advanced

General Aviation Research Simulator (AGARS) located at the FAA Civil Aeromedical Institute in

Oklahoma City. The AGARS is a high-fidelity, fixedbase flight simulator. The controls and displays used

in this study simulated those of a Piper Malibu,

which is a single-engine, high-performance aircraft

with a retractable landing gear. Control inputs are

provided by high-fidelity, analog controls, including

rudder pedals, throttle, gear, flap, and trim controls.

The HITS display appeared on a cathode ray tube

(CRT) located on the right side of the cockpit. Pilots

flew the simulation from the right seat during the study.

In addition, a video eye-tracking system was used

to record pilot gaze position during each flight. The

EL-MAR, VISION 2000 system, from EL-MAR

Incorporated, was used for this experiment. In this

head-mounted system, a miniature scene camera captures the subject’s field of view. Imagery from the

scene camera is electronically combined with a moveable cursor corresponding to the horizontal and vertical position of the eye. The combined imagery is

recorded on videotape, showing the relationships between the subject’s gaze and objects in the field of view.
3

Experimental Design

Two factors relating to pathway acquisition were

manipulated in the experiment: 1) Pathway type

(goal posts or paving stones); and 2) guidance symbology (follow-me airplane, flight predictor only, or

none), resulting in a 2 x 3 repeated measures design.

Figures 1a and 1b show how both of the pathway

types appeared when viewed from the center of the

path. Figure 2 shows the guidance symbology, including the follow-me airplane symbol, flight predictor velocity vector, and pitch reference symbol.

Display functioning was not quickened or unburdened in any fashion (Frost, 1972). Pathway type was

counterbalanced across participants, while guidance

symbology was counterbalanced within pathway type.

Procedure

Participants were tested individually. Each pilot

received a consent form to read and sign and then

completed an experience questionnaire. Following

completion of the questionnaire the participants were

shown the HITS display and given an overview of the

flight task. A calibration procedure for the eye-tracking

equipment was then performed, but pilots were not

required to wear the eye-tracker until after a practice

flight in the simulator. They were then placed in the

simulator and familiarized with the location of the

controls and displays needed during the flight.

After the pilot was familiar with the aircraft displays and controls, a ten-minute practice flight was

conducted. The pilot was then fitted with the ELMAR eye-tracking equipment, and the experimental

trials were begun. Pilots completed three flights, were

given an opportunity for a break, and then completed

the remaining three flights. Following completion of

the experimental task, participants were asked about

their display preferences. Their preferences were recorded, participants were debriefed, and they were

then dismissed.

All pilots flew six scenarios, lasting between 9 and

12 minutes each. The highway-in-the-sky path was

positioned as a traffic pattern around Runway 08 of

Albuquerque International Airport; however, pilots

did not fly the entire pattern during the scenarios.

Instead, after take-off, pilots were instructed to climb

to 100 feet (30.5 m) above ground level while holding

the runway heading and then begin a left turn to a

heading of 310 degrees. Pilots intercepted the downwind portion of the pathway generally between 7500

and 8000 feet mean sea level. The pathway was then

followed until midway through the base leg for scenarios one through five and until turning to final for

scenario six. Each scenario was ended with the aircraft in midair by blanking out the screens and

resetting the aircraft to the runway. At the end of the

third and sixth scenarios, after the displays had been

blanked out, pilots were asked to estimate their

airspeed, heading, and altitude. The actual and reported airspeeds, headings, and altitudes were recorded.

During three of the six scenarios, selected randomly, two aircraft flew within the field of view and

were visible on the out-the-window screens for 20

seconds to 1 minute. Pilots were instructed to indicate when these aircraft were detected by making a

traffic call over the radio, using a push-to-talk switch

located on the yoke. Traffic scanning task complexity

was manipulated by controlling the timing of when

each aircraft appeared in the pilot’s field of view. One

aircraft appeared in the field of view as the pilot was

in the process of establishing on the pathway and for

a short time thereafter (high complexity condition).

The other aircraft appeared during a straight portion

of the path when very little input was required to

maintain position on the path (low complexity condition). These targets were referred to as off-path and

on-path targets, respectively.

Figure 2. Display guidance symbology used in the

experiment. Note that under the ‘no-guidance’

condition, only the pitch reference symbol was visible

(from Beringer, 1999, reprinted with permission of

author).
4

RESULTS

Intercepting the Pathway

To analyze the ability of pilots to intercept the

pathway, horizontal and vertical deviations from the

pathway were recorded at 1-second intervals. Recording began when the aircraft first approached

within 100 feet (30.5 m) horizontally of the path and

continued for the next 60 seconds. Only one pilot,

during one of the six experimental trials, failed to

approach to within 100 feet (30.5 m) of the path. The

data from this pilot were not included in the analyses.

This particular pilot was the oldest pilot participating

in the experiment (67 years old).

Horizontal Deviation Analyses. A 2 x 3 (pathway

type by guidance condition) repeated measures analysis of variance was conducted on the horizontal root

mean square errors (RMSE). The only difference to

reach significance was the main effect for guidance

condition, F(2, 68) = 6.875, p < .01. The means for

the horizontal RMSE for the no-guidance, flight

predictor, and follow-me airplane conditions were

560 feet (170. m), 293 feet (89.4 m), and 108 feet

(32.9 m), respectively. Figure 3 shows the horizontal

errors separated by guidance and pathway conditions. Post-hoc analyses demonstrated a significant

difference between the no-guidance and follow-me

airplane conditions, t(34) = 3.002, p = .005, and

between the flight predictor and follow-me airplane

conditions, t(34) = 2.845, p = .007, but not between

the no-guidance and flight predictor conditions t(34)

= 1.982, p = .056. Clearly, pilots had less horizontal

error while acquiring the pathway when they were

using the follow-me airplane.

Vertical Deviation Analyses. A 2 x 3 (pathway type

by guidance condition) repeated measures analysis of

variance was conducted on the vertical RMSE. As

with the horizontal errors, a significant effect for

guidance condition was found, F(2, 68) = 11.365. p

< .001. Mean RMSE values for the no-guidance,

flight predictor, and follow-me airplane conditions

were 162 feet (49.4 m), 128 feet (39 m), and 52 feet

(15.9 m) respectively. Again, as with the horizontal

errors, post-hoc analyses indicated a significant

difference between the flight predictor and followme airplane conditions, t(34) = 4.829, p < .001, and

between the flight predictor and no-guidance

conditions, t(34) = 3.928, p < .001, but not between

the no-guidance and flight predictor conditions, t(34)

= 1.605, p = .117. Pilots committed significantly less

error vertically when using the follow-me airplane

than when acquiring the pathway without it.

In addition to the significant main effect for the

guidance condition, there was also a significant interaction between guidance condition and pathway type,

F(2, 68) = 4.457, p = .015. Post-hoc analyses indicated that vertical error was significantly greater

during pathway acquisition with the paving stone

display than with the goal post display (171 feet vs.

84 feet [52.2 m vs. 25.6 m]) when only the flight

predictor was used, t(34) = 3.601, p = .001. Figure 4

shows a graph of this interaction.

Practice Effects. To look at the effect of practice

on the pilot’s ability to acquire the pathway, a separate analysis of vertical and horizontal error across

trials was conducted. For these analyses, only trial

number (1 to 6) was treated as an independent

variable. A repeated measures analysis of variance

found a significant effect for trial number for both

the horizontal error, F(1, 35) = 5.576, p < .001, and

the vertical error, F(1, 35) = 3.89, p = .002. Figure 5

shows both of these types of error across trials. That

pilots continued to improve across trials is clear from

the figure.

Figure 3. Horizontal RMSE for each guidance and

pathway condition – NG = no-guidance, PR = flight

predictor only, and FM = follow-me airplane.

0

100

200

300

400

500

600

700

Horizontal RMSE (feet)

NG PR FM

Guidance Condition

Pavers Goal Posts
5

Subjective Comments

After completing all of the experimental trials,

pilots were asked which of the pathway types was

easier to acquire and whether the guidance provided

made it easier to acquire the pathway. Twenty-eight

of the 36 pilots (78%) believed that the goal post

display was easier to acquire than the paving stone

display. Only five (14%) believed that the paving

stones were easier to acquire and three (8%) thought

there was no difference between the two pathway

types.

Figure 5. Vertical and horizontal error during pathway acquisition by trial

number.

0

200

400

600

800

1000

RMSE (feet)

123456

Trial Number

horizontal vertical

Regarding the effect of flight guidance on pathway

acquisition, 26 of the pilots (72%) thought that the

follow-me airplane symbology made it easier to acquire the pathway. Five pilots (14%) believed that the

use of the flight predictor without the follow-me

airplane was more effective for acquiring the pathway, and 5 pilots (14%) did not think that any of the

guidance symbology was useful for acquiring the

pathway. It is interesting to note the large percentage

of pilots who expressed a preference for the goal post

over the paving stone pathways, even though few

actual performance differences were obtained.

Spotting Traffic

Overall, pilots spotted an average of 3.25 aircraft

out of the six, although some pilots were able to spot

all six aircraft while others spotted none. A onesample t-test demonstrated that pilots located significantly fewer aircraft than were possible, t(35) = -7.427,

p < .001. In addition to this finding, a separate

analysis was conducted comparing the number of offpath and on-path targets that were located. On average,

pilots located 1.33 off-path targets (high-complexity

condition) and 1.92 on-path targets (low-complexity

condition). A paired t-test showed that this difference was significant, t(35) = 2.78, p = .009.

Two things are clear from the current data. 1)

Pilots are able to spot traffic while using the HITS

display. Although only about half of the traffic was

spotted overall, pilots clearly differed in their ability

to spot traffic, even though their experience with the

display was equivalent. Other factors besides the

novelty of the display had to play a role in these

differences. 2) Task complexity was a

major contributor to the pilot’s ability

to spot traffic because significantly

more traffic was spotted under the

low-complexity condition than under

the high-complexity condition.

Eye-Gaze Data

To analyze the eye-gaze data, the

percentage of time during each flight

that was spent looking out of the cockpit was computed. The eye-gaze videotapes were reviewed, and a count was

made of both the number of times that

the pilot looked out the cockpit and

the total time that was spent looking

0

20

40

60

80

100

120

140

160

180

Vertical RMSE (feet)

NG PR FM

Guidance Condition

Pavers Goal Posts

Figure 4. Vertical RMSE for each guidance and

pathway condition – NG = no-guidance, PR = flight

predictor only, and FM = follow-me airplane.
6

out of the cockpit. The total time count was then

divided by the length of the flight to get a percentage

of the time during the flight in which the pilot was

looking out of the cockpit. The time that pilots spent

looking out of the cockpit across all flights varied

from 0% to 52%, with a mean of 14% and a median

of 10%. A 2 x 3 (pathway type by guidance condition) repeated measures analysis of variance was performed on the percentage scores to see if there were

any differences in head-out time due to differences in

pathway type or usage of guidance symbology. No

significant effects were found.

In addition, correlations were computed between

head-out time and several performance and demographic variables. Table 1 presents the correlations

between these variables. As expected, head-out time

was significantly correlated with the number of aircraft spotted. Head-out time was also significantly

negatively correlated with age, indicating that older

pilots spent less time head-out than did younger

pilots. Head-out time was not significantly correlated with either total flight time or flight time during

the last 90 days.

Awareness of Secondary Display Information

Pilot estimates of airspeed, heading, and altitude

were recorded along with actual corresponding system values following completion of the third and

sixth trials. Responses were scored as “hit” or “miss”

if they were within a specified range of the actual

values. The range for each aircraft parameter was

selected based on practical test standard values for

private pilots. Each range was twice that specified in

the practical test standards for performance of most

private pilot maneuvers – ± 20 knots for airspeed, ± 20

degrees for heading, and ± 200 feet (61 m) for

altitude. Estimates were scored as a miss if they fell

outside the ranges specified or if the pilot said “don’t

know,” “no idea,” etc. for the estimate.

Of the 72 total estimates given for each value (36

subjects x 2 estimates per subject = 72 total estimates), pilots were correct 59 times for airspeed

(82%), 32 times for heading (44%), and 22 times for

altitude (31%). The number of correct estimates

differed significantly across the three information

types, χ2(2, N = 72) = 40.79, p < .001.

A comparison was performed of the difference

between the first time that pilots were asked to make

estimates and the second time they made estimates.

For the airspeed estimates, 28 (78%) gave correct

estimates the first time and 31 (86%) estimated

correctly the second time; not a significant improvement. For the heading estimates, nine (25%) correctly estimated the first time, while 23 (64%)

estimated correctly the second time. A paired t-test

showed a significant difference in correct estimates,

t(35) = 4.95, p < .001. Only four (11%) correctly

estimated their altitude the first time they were asked.

This improved to 18 correct estimates (50%) for the

second attempt. This improvement was also found to

be statistically significant, t(35) = 3.86, p < .001. The

most dramatic errors were committed when estimatTable 1.

Intercorrelations Between Percentage of Head-Out Time, Performance, and Demographic Variables.

______________________________________________________________________________

Variable 1 2 3 4 5 6 7

______________________________________________________________________________

1. Head-out time (%) -- .496b -.315 -.176 -.502b -.247 -0.58

2. Number of aircraft spotted -- -.117 -.217 -.329a -.169 .117

3. Mean horizontal error -- .751b .692b .416a -.226

4. Mean vertical error -- .509b .114 -.304

5. Age -- .500b -.390a

6. Total flight time -- -.196

7. Flight time – last 90 days --

____________________________________________________________________________________

a Correlation is significant at the .05 level (2-tailed, n = 36).

b Correlation is significant at the .01 level (2-tailed, n = 36).
7

ing altitude. Ten pilots were off by > 1000 feet (305

m) the first time they estimated their altitude; one

pilot was > 4000 feet (1220 m) in error.

DISCUSSION

This study examined the effect of pathway symbology and guidance cues on pathway acquisition,

and the ability of the pilot to establish the airplane on

the path in such conditions. Awareness of the position of the airplane relative to the intended flight

path is one of the primary functions of a HITS

display; however, little research has been conducted

regarding maintaining that awareness under various

unexpected conditions. Reising and Barthelemy

(1991), for example, examined the effect of a HITS

display on the pilot’s ability to recover from unusual

attitudes. However, in that study, pilots began each

trial on the pathway (though at an unusual attitude

relative to the floor of the pathway). It seems likely

that a pilot using a HITS display will, at some point,

become distanced from the pathway, whether by

design through evasive maneuvers, or unintentionally, and will need to reposition the airplane back on

the path. Consequently, the need for this type of

study becomes obvious.

When comparing the two pathway types for ease of

acquisition, little difference was found between the

goal-post display and the paving-stone display. There

was some indication that vertical error was less using

the goal-post display, but that advantage was nullified when a follow-me airplane aided the pilot in

intercepting the pathway. Therefore, for pathway

interception and acquisition, the manner in which

the pathway was depicted had little overall effect. In

contrast, 78% of the pilots felt that it was easier to

intercept and acquire the pathway using the goal-post

display than when using the paving-stone display.

This finding is reminiscent of the review by Andre

and Wickens (1995) demonstrating that the favorableness of a display is not necessarily a good indication of its effectiveness.

A second finding was that use of the follow-me

airplane significantly enhanced the ability of a pilot

to intercept the pathway relative to using a flight

predictor symbol alone or no-guidance symbology;

however, the assistance provided by the follow-me

airplane was most useful to pilots with little or no

experience with a particular pathway type. Notably,

the effect of practice at intercepting the pathway

appeared to overwhelm any effects caused by differences in either the pathway or guidance symbologies,

suggesting that the selection of pathway depiction,

and the presence and functioning of guidance symbologies, are not as important as ensuring that pilots

receive practice with the display. There still remains

a question regarding how long the training remains

effective. Further research is required to determine

how often training would be required to maintain

proficiency with the display.

One interesting result in the current study was the

apparent tendency for some of the pilots, when first

viewing the HITS display, to be unable to interpret

the two-dimensional display as a representation of a

three-dimensional volume of space. Pilots “flying

through” the pathway, from one side to the other,

without even attempting to turn the plane onto the

pathway, manifested this tendency, which seemed to

be more prevalent among the older pilots in the

study. The inability of these pilots to extract threedimensional information from a two-dimensional

display is reminiscent of the work of Hudson (1960)

on the inability of certain cultural groups to perceive

specific types of two-dimensional drawings in three

dimensions. Hudson concluded that differences in

the tendency to make use of certain kinds of depth

cues were the result of culturally mediated experiences. Perhaps the same type of finding was manifested in the current study. Although computer gaming

experience was not assessed, it seems likely that the

older pilots would have less computer gaming experience than would the younger pilots. In general, the

older pilots seemed to experience more difficulty

with the displays.

As mentioned earlier, the only pilot who failed to

come within 100 feet of the pathway during one of

the flights was the oldest pilot in the group. A

significant positive correlation was found between

age and the amount of horizontal and vertical error

made during pathway acquisition. A significant negative correlation was found between age and the number of traffic targets located. There was also a

significant negative correlation between age and the

amount of time spent looking outside of the cockpit.

Older pilots, in general, spent more time looking at

the HITS display. Inexperience with these types of

perspective displays could explain some of the pilots’

difficulties in correctly interpreting three-dimensional

volume from a two-dimensional depiction. Because

not all depth cues are available in these displays, and
8

because some depth cues are distorted, an inexperienced viewer of the display could have difficulty

interpreting the display. Again, practice with the

display is an important aspect to successful display

interaction.

The second type of SA examined in the present

study was awareness of other airplane traffic. Even

though pilots did not spot a significant proportion of

the traffic, it is premature to conclude that the HITS

display prevented or interfered with the ability to

spot traffic relative to more traditional flight displays. A direct comparison of traditional and HITS

displays was not performed. One question of interest

for the current study was whether the HITS display

would absorb attention that would otherwise be used

to search for traffic simply because of the novel nature

of the display. On average, pilots in the current study

looked outside of the cockpit 14% of the time. No

research could be found regarding how much time

pilots in a GA environment normally spend looking

outside, so it is difficult to make judgments; however,

this percentage does seem low, especially for a flight

occurring under visual flight rules (VFR).

Even though pilots in the current study looked

outside of the cockpit 14% of the time on average,

many demonstrated a willingness to take their attention away from the HITS display to search for traffic,

as evidenced by the finding that some of the pilots

were able to spot all of the traffic. Task complexity

was shown to be a factor in their ability to locate

traffic. There was a significant difference in the

number of aircraft located during the high-complexity and low-complexity portions of the flight. As with

studies of advanced avionics in airline cockpits

(Damos, John, & Lyall, 1999; Rudisill, 1994; Wiener,

1993), the complexity of interacting with the display,

and not display novelty, is believed to be the main

driver of how long and how often the pilot focused

attention outside of the cockpit.

The final type of SA that was studied was an

awareness of flight parameters (airspeed, heading,

and altitude) present on the HITS display. Pilots

were much more successful at estimating airspeed

than they were heading or altitude. One simple explanation for this result is that airspeed was less variable

than either heading or altitude. Pilots could monitor

this value less often but still have an accurate idea of

their airspeed. It is interesting that the pilots had such

difficulty with heading information (44% correct

responses overall), given that the pathway headings

were known to the pilot prior to the start of the

experiment. If the pilot had been aware of which leg

of the traffic pattern was being flown, it would have

been possible to deduce the aircraft heading from the

original runway heading. Some of the pilots, in fact,

made this deduction; however, the majority did not.

One problem with querying the pilot’s awareness

of detailed aspects of a situation is that these details

are not of concern to the pilot under all conditions

(McGuiness, 1995). Most often, the pilot translates

these data into a meaningful, qualitative state (e.g.,

too high, too slow, on course). However, it can be

argued that, if the information presented requires

translation before it becomes meaningful, it violates

the principle of display design which states that the

operator should not be required to derive functional

properties of the system but should receive those

properties directly (Lintern, Waite, & Talleur, 1999).

Even if unaware of the exact values of certain flight

parameters, the pilot should at least be aware of the

trend of those values (slowing down, climbing, etc.).

In addition to being least successful at guessing

altitude information (31% overall, with only 11%

correct estimates the first time they were queried),

pilots were unaware that the airplane was slowly

climbing from the point at which the pathway was

first intercepted. The large majority of the estimates

for the altitude were less than the altitude at which

the airplane first intercepted the pathway, the altitude the pilots had been told to attain and hold until

intercepting the pathway.

Several conclusions can be drawn from the results

of this research. First, at least for the pathways tested

in the current study, pathway depiction is not as

important as practice with the display. Use of any

particular HITS display should be predicated on the

receipt of training for that display. The current study

suggests that this training does not have to be extensive to be effective, but it should include situations

that will expose the pilot to unusual interactions with

the pathway. This will enable the pilot to become

adept at interpreting the two-dimensional depiction

as a three-dimensional volume of space. Second, task

complexity has a more powerful effect on the ability

to focus attention outside of the cockpit than does

display novelty. Pilots can focus their attention on

other aspects of flying as long as they do not find it

too difficult to maintain the airplane on course and

on the path. One possible solution to this problem is

to place the HITS display on a head-up display
9

(HUD), thus allowing the pilot simultaneously to

maintain both visual contact with the display and at

least partial focus outside of the cockpit. Current

research at the Civil Aeromedical Institute is looking

at this issue. Finally, new display depictions are

needed that will allow the pilot to easily track trends

in flight parameters. It will not always be the case that

the pathway will be straight and level. A general

awareness of altitude, heading, and airspeed is important to the safety of the flight, especially if the HITS

display should fail.

REFERENCES

Andre, A.D. & Wickens, C.D. (1995). When users

want what’s not best for them. Ergonomics in

Design, October, pp.10-14.

Beringer, D.B. (1999). Flight command-guidance indicators or pathway displays: My way or the

highway? Paper presented at the 10th International Symposium on Aviation Psychology, Columbus, Ohio, May 2-6, 1999.

Damos, D.L., John, R.S., & Lyall, E.A. (1999). The

effect of level of automation on time spent looking out of the cockpit. International Journal of

Aviation Psychology, 9(3), 303-14.

Endsley, M.R. (1995). A taxonomy of situation awareness errors. In Human Factors in Aviation Operations, R. Fuller, N. Johnston, and N. McDonald

(Eds.). Aldershot, England: Avebury Aviation,

Ashgate Ltd., pp. 287-92.

Endsley, M.R. (1997). Supporting situation awareness

in aviation systems. In Proceedings of the IEEE

International Conference on Systems, Man, and

Cybernetics, Orlando, Florida, October 12-15,

1997, pp. 4177-81.

Frost, G. (1972). Man-machine dynamics. In H.P. Van

Cott & R.G. Kinkade (Eds.), Human engineering guide to equipment design (Rev. ed.) (pp.

227-310). American Institutes for Research, Washington, DC: US Government Printing Office.

Hudson, W. (1960). Pictorial depth perception in subcultural groups in Africa. Journal of Social Psychology, 52, 183-208.

Lintern, G., Waite, T., & Talleur, D.A. (1999). Functional interface design for the modern aircraft

cockpit. International Journal of Aviation Psychology, 9(3), 225-40.

McGuiness, B. (1995). Situational awareness measurement in cockpit evaluation trials. AGARD CP

575, Paper 7.

Reising, J. & Barthelemy, K. (1991). Unusual attitude

recoveries using a pathway in the sky. In A Collection of Papers: Flight Simulation Technologies

Conference (pp. 131-8). New Orleans, Lousiana,

August 12-14.

Rudisill, M. (1994). Flight crew experience with automation technologies on commercial transport

flight decks. In M. Moulou & R. Parasuraman

(Eds.), Human performance in automated systems: Current research and trends (pp. 203-11).

Washington, DC: Catholic University.

Schwaneveldt, R., Beringer, D.B., Lamonica, J., Tucker,

R., & Nance, C. (2000). Priorities, organization,

and sources of information accessed by pilots in

various phases of flight. FAA Office of Aviation

Medicine Technical Report #DOT/FAA/AM-00/

26. Department of Transportation, Federal Aviation Administration, Washington, DC.

Warner, D.A. (1979). Flight path displays. WrightPatterson AFB, OH: Air Force Flight Dynamics

Laboratory, Technical Report AFFDL-TR-79-

3075.

Wickens, C.D. (1995). Situation awareness: Impact of

automation and display technology. AGARD CP

575, Paper K2.

Wiener, E.L. (1993). Life in the second decade of the

glass cockpit. In Proceedings of the Seventh International Symposium on Aviation Psychology (pp.

1-7). Columbus: The Ohio State University, Department of Aviation.