A piloted simulation study was conducted to evaluate the effect on instrument landing system tracking performance of integrating localizer error rate information with the raw localizer error display. The resulting display was named the pseudo command tracking indicator (PCTI) because it provides an indication of any changes of heading required to track the localizer. Eight instrument-rated pilots each flew five instrument approaches with the PCTI and five instrument approaches with a conventional course deviation indicator. The results show good overall pilot acceptance of the PCTI and a significant reduction in localizer tracking error

Hinton, D. A.

English

NASA Technical Reports Server

I- 
A SIMULATOR EVALUATION OF A RATE-ENHANCED 
INSTRUMENT LANDING SYSTEM DISPLAY 
David A. Hinton 
NASA Langley Research Center 
ABSTRACT 
A piloted simulation study was conducted to evaluate the effect on instrument 
landing system tracking performance.of integrating localizer error rate information 
with the raw localizer error display. The resulting display was named the pseudo 
command tracking indicator (PCTI) because it provides an indication of any changes 
of heading required to track the localizer. Eight instrument-rated pilots each 
flew five instrument approaches with the PCTI and five instrument approaches with 
a conventional course deviation indicator. The results show good overall pilot 
acceptance of the PCTI and a significant reduction in localizer tracking error. 
171 
IL 
https://ntrs.nasa.gov/search.jsp?R=19840003974 2020-03-22T07:55:55+00:00Z
PSEUDO COMMAND TRACKING INDICATOR (PCTI) 
This figure compares the PCTI presentation and the conventional CD1 
presentation for two different flight situations. The PCTI consists of two 
needles joined at the horizontal centerline of the instrument. The upper 
needle presents the same raw localizer error information as is presented on 
the conventional display. The lower needle pivots from the upper needle and 
indicates localizer error rate. The PCTI in this figure depicts two situations. 
The airplane between the two displays is to the left of centerline and with no 
wind is returning to centerline (see solid flight path arrow). With a wind (see 
dashed wind vector arrow) the airplane is tracking away from centerline (dashed 
flight path arrow). The solid localizer error rate needle depicts the first 
situation. If the pilot turns the airplane to keep the tip of the rate needle 
centered, the result will be an asymptotic return to the centerline. The second 
situation is depicted by the dashed rate needle. The rate needle is deflected 
more than the localizer needle, indicating increasing error. If the localizer 
error rate were zero,then the two needles would form a straight line. 
## 
. . . .o ..,, 
CONVENTIONAL LOCALIZER 
DISPLAY 
RUNWAY 
0 
: 1 
9 4’--- 
-? 
WIND 
SITUATION 
PCTI DISPLAY 
’ DISPLAY LOCALIZER ERROR RATE ALONG WITH LOCALIZER ERROR 
a PROVIDE TURN COMMANDS BY INTEGRATING THE TWO INDICATIONS 
8 “ON COURSE” INDICATION IS II\!DEPENDENT OF RUNWAY HEADING OR 
WIND CONDITION 
0 PROVIDES PILOT WITH LEAD INFORMATION 
172 
PCTI IN FOUR SITUATIONS 
The diagram below shows an airplane in four situations and the corresponding 
PCTI displays. In the left-most figure the airplane is stabilized on the 
localizer centeriine. Both needles of the PCTI are centered. In the next 
figure the airplane has begun to drift off centerline because of a wind. The 
localizer needle is still centered but the rate needle is deflected to the left, 
telling the pilot to turn to the left. The third figure shows the airplane to 
the right of the centerline on a flight path returning to the centerline. The 
localizer needle is deflected to the left and the rate needle is deflected back 
towards the center to indicate decreasing error. In the final figure the airplane 
is stabilized on centerline with a heading that compensates for the wind. Both 
PCTI needles are centered. 
f 
I 
0 . . . . . 
I 
0 
. . . se. 
0 
.- .0... 
173 
DISPLAY IMPLEMENTATION 
The PCTI display was implemented in the NASA LaRC General Aviation (GA) 
Simulator. A 5-inch diagonal monochromatic CRT displayed the PCTI and CD1 
presentations. The CRT was located immediately to the right of the primary 
flight instruments in a typical GA instrument panel CDI location. The CRT 
presentation was chosen for the speed and ease of display implementation and 
does not imply that a CRT is necessary for a PCTI. Switching between CD1 and 
PCTI presentation was accomplished by driving both needles as one needle with 
localizer error information when the CD1 was desired. A conventional glideslope 
needle was also drawn on the CRT for the study. 
174 
TEST SUBJECTS AND DATA RUNS 
Data were collected from eight pilots. All of the pilots were instrument 
rated and their experience ranged from 250 hours to 6000 hours. Each of the 
pilots was given an explanation of the display and simulation task and was 
required to fly four practice approaches. More practice was allowed if requested. 
Each pilot flew five data runs with the PCTI and five data runs with a 
conventional CDI. Since the run conditions were identical for each run, the 
runs were alternated between the CDI and PCTI to minimize learning effects. 
0 EIGHT SUBJECTS, ALL INSTRUMENT RATED, HOURS RANGE FROM 250 TO 6000 
. EACH PILOT WAS GIVEN AN EXPLANATION OF DISPLAY AND RUN CONDITIONS 
AND FOUR PRACTICE RUNS 
l DATA RUNS ALTERNATED BETWEEN CONVENTIONAL DISPLAY AND PCTI, FIVE RUNS 
WITH EACH DISPLAY PER PILOT 
175 
RUN CONDITIONS 
Each data run began with the airplane 0.3 nautical mile2 left of the 
localizer centerline about 5.3 miles from the runway on a 30 intercept heading 
to the localizer as indicated by the circle and arrow in this figure. This 
situation resulted in a localizer intercept prior to reaching the outer marker 
or glideslope intercept. Identical weather conditions were used for each data 
run. Ai the initial altitude of 1000 feet above ground level a 24 knot wind 
from 120 right of localizer course was present. At the surface a 12 knot wind 
from 36 left of localizer course was present. Linear interpolation for both 
wind speed and direction was used at other altitudes. This provided a constantly 
changing wind as the airplane descended on the glideslope. Light turbulence was 
also present during each data run. Data runs were terminated with an automatic 
reset just prior to reaching decision height at the middle marker. 
- -+- -+-v 
LOCAL1 ZER LOM MM RUNWAY 
176 
DATA RUN PLOT, CDT 
This plot shows angular localizer error Versus distance from the runway 
for all five CD1 runs for one of the subject pilots. Localizer error in degrees 
is presented on the ordinate and di.stance from runway in thousands of feet is on 
the abscissa. Each run began with the airplane to the left of the localizer 
about 5.3 nautical miles from the runway [top right of plot). The airplane then 
intercepts the localizer about 5 miles from the runway and tracks inbound until 
an automatic reset occurs at a range of about 4000 feet. This plot is typical 
of each subject pilot. 
L. 
1.600 
-1.600 
-2.000 
-2400 ’ ’ ‘I’ ’ ’ 1 ’ ’ ‘I’ I I I I I III I I I I I II, I I I , , J 
0.00 3.50 7.00 to-50 llL.00 17.50 21.00 DIST. 29-50 28.00 31.50 
Distance from runway.(feet x 103) 
177 
DATA RUN PLOT, PCTI 
This plot shows the five PCTI runs for the same pilot that flew the 
CD1 runs in the previous plot. Higher system frequencies and smaller localizer 
errors are observed with the PCTI. 
- 1.200 
tc 
e .800 
P F u V 400 
Gc 
k * 
k 
= 0.000 
Q) 2 
E 
- .YOO 
V- -.eoo - 
F 
2 
s 
-1.200 - 
-1.600 - 
-2.000- 
-2.YOO. ’ ’ ’ I’ ’ ’ 1 ’ ’ ’ 1 ’ ’ ’ I I I III I I I I I I II I I ,I , , 
0.00 I 3.50 7.00 10.50 1Y.00 17.50 ' 21.00 
DIST. 
2'4.50 28.00 31.50 
Distance from runway (feet x 103) , 
178 
PILOT COMMENTS 
Pilot comments indicate that the PCTI was easy to interpret and provided 
more useful information than the conventional CDI. Tn particular, the PCTI 
provided lead information on the localizerand solved the problem of finding 
the correct heading to compensate for wind. The pilots were less concerned with 
localizer error using the PCTI since keeping the'rate needle centered automatically 
kept the localizer error near zero.. When.errors did developithe pilots would 
bank the airplane into.a turn until the localizer rate indicated a return to center- 
line. When the localizer error zeroed,the pilots would turn the airplane to zero 
the localizer error rate. Very little use of the directional gyro was reported 
by the pilots. The reduced scanning tended to lower reported pilot workload 
while the higher system frequencies tended to increase workload. The result 
was that reported workloads with the PCTI and the CD1 were about the same. 
’ ABOUT THE SAME WORKLOAD, PCTI MEANS LESS SCANNING BUT TIGHTER CONTROL 
’ LESS LATERAL WORKLOAD AND MORE TIME FOR GLIDESLOPE 
0 PCTI EASY TO INTERPRET 
l USED BANK ANGLE TO SET RATE NEEDLE IN GOOD POSITION THEN ROLL LEVEL 
AND WAIT FOR LOCALIZER TO CENTER; VERY LITTLE D.G, USE 
l LESS CONCERNED WITH LOCALIZER, JUST KEEP RATE NEEDLE CENTERED 
0 IGNORE RATE DURING LARGE CORRECTIONS AND USE IT TO STAY ON LOCALIZER 
ONCE THERE 
l SOLVED PROBLEM OF FINDING THE CORRECT HEADING 
l PROVIDES LEAD INFORMATION ON LOCALIZER 
179 
CONCLUSIONS 
The pseudo command tracking indicator (PCTI) was designed to aid pilots 
during ILS approaches. The PCTI display was evaluated in the General Aviation 
Simulator using eight instrument-rated pilots. The results showed a 42 percent 
reduction in localizer mean RMS error with the PCTI when compared with a 
conventional CD1 display. The PCTI display aided the pilot in compensating for 
wind drift and in correcting for wind- and turbulence-induced deviations from 
centerline. No significant changes in pilot workload or glideslope RMS errors 
were noted. 
’ PCTI DISPLAY DESIGNED TO AID PILOT DURING ILS APPROACH 
’ DISPLAY EVALUATED IN GA SIMULATOR WITH EIGHT SUBJECT PILOTS 
’ FORTY-TWO PERCENT REDUCTION IN LOCALIZER MEAN RMS ERROR 
’ NONSIGNIFICANT CHANGES IN GCIDESLOPE‘TRACKING OR PILOT WORKLOAD 
’ KEEPING THE RATE NEEDLE CENTERED WILL AUTOMATICALLY KEEP THE 
LOCALIZER NEEDLE CENTERED 
’ SOLVES PROBLEM OF FINDING THE CORRECT HEADING IN WINDS 
180 


A simulator evaluation of a rate-enhanced instrument landing system display

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