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T Government Aecostvon No. BT. Recipients Catalog Nov
j FAA-AM-79~19 ] 1

(JHE 1976 ACCIDENT EXPERIENCE OF CIVILIAN PILOTS WITH
ASTATIC PHYSICAL DEFECTS, oa
a ~~ ee

—

“Berlarmng Orgennenien Rapes. i
a “-ROBERT/DILLE sam CHARLES z BOOZE f i

Paileomng Organization Name ond Addisas 10. Werk Unit No. (TRAIS)
FAA Civil Aeromedical Institute
P.O, Box 25082 n
Oklahoma City, Oklahoma 73125

Contract ov Gront Ne.

. 12, Spenvenng Agency Nome ond Address

Office of Aviation Medicine
Federal Aviation Administration
800 Independence Avenue, S.W.
Washington, D.C. 20591

15S. Suppiementery Noten

L

16, Abstract

The 1974 and 1975 aircraft accident experiences of civilian pilots with eight select-
ed static physical defects have been examined and reported previously. Three cate~
gories--blindness or absence of either eye, deficient color vision with a waiver, and
deficient distant vision--had significantly more accidents than were expected on the
basis of observed-to-expected ratios. However, pilots with these conditions reported
considerably higher median 6-month flight times than did an active airman population
sample and accident airmen without selected pathology. In 1975 the reported recent
and total flying times for all airmen with these defects were determined and accident
rates were calculated. The rates for airmen with blindness or absence of an eye were
still found to be significantly higher. The contact lens group was also selected to
receive special attention in a study of the 1976 accident data‘ because marginal sig-
nificance was found on analysis of the 1975 data and, after 1976, this group will not
carry a pathology code or require a waiver and thus will be difficult to study.

Observed-to-expected ratios for 1976 are 1.91 for deficient color vision with a
waiver, 1.28 for contact lens users, 1.37 for blindness or absence of either eye, and
1:62 for deficient distant vision. The accident rates per 100,000 hours of cumulative
and last 6 months' flying experience were significantly greater for contact lens users)
and monocular pilots than for the active airman population... The other groups had no
consistently significant differences. Each accident was reviewed to determine time of|
day, phase of ‘flight, weather conditions, and recent flight experience in an attempt
to determine,;bases for the findings. None was found. .

17. Key Words 16

‘bynes

. Accident investigation
Aircraft accidents
Flight safety
Physical defects

Pilot performance

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A A644 320 Ete



References

Dille, J. R., and C. F. Booze: Accident Experience of Civilian Pilots
With Static Physical Defects. FAA Office of Aviation Medicine Report ‘
No. AN-76-7, 1976. :

Dille, J. Re, and C. F. Booze: The 1975 Accident Experience of Civilian
Pilots With Static Physical Defects. FAA Office of Aviation Medicine
Report No. AN-77~20, 1977,

Kochhar, S., and T. M. Fraser: Monocular Vision as a Factor in Flight !
Safety, Preprints of the 1977 Annual Scientific Meeting of the Acrospace
Medical Association, pp. 53-54, 1977.

Lewis, C. E., Jr., W. R. Blakeley, R. Swaroop, R. L. Masters, and

T. C. McMurty: Landing Performance by Low-Time Private Pilots After

the Sudden Loss of Binocular Vislon--Cyclops II, AEROSP. MED., 44:1241- Y

1245, 1973. . |
{
}
t

Lewis, C. E., Jr., and G. E. Krier: Flight Research Program XVI: Land-
ing Performance in Jet Aircraft After the Loss of Binocular Vision,
AEROSP. MED., 40:957-963, 1969.

2 Late toe mete nana CREE Set Rn i)



Il. Method.

For the 1976 active airman population of 780,408, the numbers were deter-
mined who had blindness or absence of either eye (includes uncorrectable dis-
tant visual acuity of 20/200 or worse in one eye); contact lenses; deficient
color vision but who had taken and passed a signal light gun test and had no
operational limitation; and deficient distant vision (uncorrected distant
vision poorer than 20/100 for first and second class, or does not correct to
standards for any’class). The defictent distant vision category ordinarily
includes many who also have absence of an eye and some who wear contact lenses,

‘but these were subtracted for this study.

For each of these four categories, their representation per 1,000 active
airmen, expected frequencies for 4,355 total accidents, actual accident expe-
rience, ratio of observed to expected accidents, and significance by the chi-
square test were calculated.

Total and last~6-months civilian flight hours, reported at the time of
the most recent physical examinations, were obtained for all active airmen,
those with blindness or absence of either eye, those with deficient distant
vision, those with deficient color vision, and those who wear contact lenses.
From these flight time data, accident rates per 100,000 hours of flying
experience, both total and in the last 6 months, were calculated. and
statistically compared.

Finally, the records for all accidents involving pilots in one of these
four defect categories were reviewed by the authors to determine if- medical
conditions had been considered by the accident investigators or if time of
day, phase of flight, nature of the accident, or other findings offered any
plausible explanation for the accident experience of these groups.

ce Red neg Pian be ne a pageants ie

III, Results.

The numbers of active airmen in each of the four categories and their
accident experience in 1976 are shown in Table 1. The 1974 and 1975 data are
included for comparison, Again, the same four categories had more than their

expected numbers of accidents--deficient color vision with no restriction, .
deficient distant vision, blindness or absence of either eye, and contact
lens use,

When the accident experiences of airmen with each of the four static
defects of major concern were compared with the total active airman popula-
tion accident experience per unit of total (cumulative) and recent (6 months)
exposure (Table 2), both rates for airmen with blindness or absence of an .
eye were again found to be significantly higher as were those for the contact
lens group, the rates for those with deficient color vision were again sig~
nificant when total experience was used but not significant when calenlated
for recent exposure. Similar findings to those for color vision were observed
for the deficient distant vision category.



Apennines amteee natceneitie cannot atte

THE 1976 ACCIDENT EXPERIENCE OF CLVILTAN PILOTS
: WITH STATIC PHYSICAL DEFECTS
f

1. Introduction.

The 197% and 1975 aircraft accident experiences of civilfan pilots with
eight selected static physical defects have been examined and reported pre-
viously (1,2). These conditions were blindness or absence of either eye, use
‘of contact lenses, deficient color viston with a statement of demonstrated
ability (waiver) and no operational Limitations, deficient color vision with
a restriction "not valid for night flight or color signal control," deficient
distant vision, paraplegia, deafness, and amputations, For each category we
determined the number in the active airman population, the rate per 1,000
airmen, the expected number of accident. atrmen on a ratio basis to total air-
men and total accidents, the observed accident airmen, the observed-to-
expected accident airman ratio, and the statistical significance by che chi-
square test. Three groups--blindness or absence of either cye, detictent
color vision with a waiver, and deficient distant vision--had signifteantly
more accidents than were expected on the basis of observed-to-expected ratios.
In 1974, pilots with these three conditions repurted considerably higher
(4- to 8-fold) median 6-month flight times in the 6 months preceeding their
most recent physical examinat fons before their accidents. than did an active
airman population sample, but the study was not designed to determine the
role of exposure by calculation of accident rates. ae

In 1975 the same three categories plus the contact lens group had more
aceidents than were expected as demonstrated by the obgerved-to-expected
ratio. This year the self-reported 6-month and total flying times for all
atrmen and all atrmen with the three-defects significant in 1974 were deter-"
mined and accident rates were calculated. ‘the rates for airmen with blind-
ness or absence of an eye were found to be significantly higher than the
total active airman population, The rates for atrmen with defictent distant
vision and deficient color viston and a watver were not significant when the
G-month. flying Clmes were used; the rate for the color vislon group using
total time was significantly higher but was fele to be of marginal importance
considering the 6-month rate.

Individual accident records were reviewed to determine any possible
relationship between visual detects of the plot and ageldent cause, phase of
flight, type of Clying, time of day, and weather but no unusual assoc lations
were determined.

The contact lens group was selected to receive spectal attention ina
study of Che 1976 data because a marginal significance was found in the anal-
ysis of the 1975 accidents and, after 1976, this group wilt not carry a
pathology code or require a waver and thus will be very difftteult to study.



nature of the problem or how to aveld it. . Ne changes in medical standards or
policies are proposed at this time. Studies have shown normal performance
by binocular pilots suddenly rendered monocular (3,4,5) so no turther res
{8 recommended, either, for now. J

rare

We do suggest greater awareness: of chese findings and our concern, in=
creased knowledge about depth perception, and recognitton of the disadvantages
of monocularity by-¢ Light instructors, phystetans, affected airmen, and
accident investigators,

At a recent staff seminar, 15 visual cues for depth perception were
identiffed. Only two (stereopsis and convergence) are binocular, the other
13 are monocular including retinal size, which ts better than stervopsis, and
motion parallax, which is also very effective. However, with monocularity
there is 1) no xpare, 2) possible incapacitation by a foreign body, 3) a
reduced Cleld of vinton, 4) an uncompensated blind spot, 5) tnereased aware-
ness of floaters, and, perhaps most important, 6) frequent dental by the
individual,

The vartable classiffeation of many. pllots as monocular, which has com
Plicated the analysis herefn, can probably be attributed to the frequent
imprecise measurement.of acuities of 20/100 or worse. A case which varted
from 20/400 to 20/13. uncorrected probably tavolved undetected contact lenses.
Improved accuracy will be stressed for Aviation Medical Examiners There is
some regret that administrative monocal rity is combined with actual
monocularity tn our data base and that refractive errer faformatton fs not
obtained,

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cor wetrewd oe wee ut es ce : oe nt

Review of each of the accidents and extraction of factors of interest

and concern did not reveal any unusual associations of these accidents with j
weather, time of day, mid-air collisions, or agricultural flying. Physical ‘
findings had not been ascribed causal roles. Landing accidents, which ,
usually account for about 40 percent of the total, were listed in our pre~
liminary tabulation as the phase for 89 percent of the monocular pilot acci-
dents. However, after review of the reports for the correct phase and
adjustment for emergency landings’ reportedly caused by mechanical problems,
the final figure was 41 percent (15 of 37). Of these, two struck objects
(power line, trees) on approach, one misjudged snow depth, two landed left or y
right of he runway, four ran off the end of the runway (one on a downwind .
jJanding), two lost directional control, and one accident was blamed on a 1
downdraft. Most of the 15 were pilot factor accidents but not definitely
associated with their visual problems. Binocular pilots have similar acci~

dents. Some of the accidents with "loss of power” and other cited mechanical H
problems could also have been due to human factors; mechanical problems can

be caused by human errors and loss of power is an easy excuse for landing

short.

When the medical records of 36 monocular" pilots with the 37 accidents
were reviewed, we were surprised to learn that 3 had been miscoded and 5 who
were originally correctly coded were subsequently reported as having better
than 20/200 corrected visual acuity in their "pad" eye.

No corrections to the tables and calculations have been made as a result
of this finding. We assume that the errors and variations apply equally to
the 37 accident airmen and to the 4,855 total “monocularTM airmen groups. The
ratios and rates which we have calculated here are, by definition, estimates
and we feel that they are still best estimates. We do not have sufficient
resources or, priority to review all 4,855 medical records at this time.

Of the 36 monocular airmen who had accidents, 18 had no useful vision

in one eye, 9 had best corrected vision of 20/200 or worse in one eye, 5 had
previous visual recordings which caused correct assignment of a monocular

code but do not presently meet the criteria, the record cannot be located for
one, and 3 never should have been coded as monocular. One of the non-monocular
pilots had two accidents in 1976.

six of the 37 accidents were fatal; 2 of these 6 pilots did not meet
the monocular criteria at the time of their accidents.

weather, time of day, or recency of experience for the contact lens, deficient

| No unusual associations were found with phase of flight, accident cause,
distant vision, or deficient color vision groups, either.

Iv. Conclusions.

Despite the recent discovery of errors and variations in the assignment
of the code for monocularity, the increased accident ratios and rates for
monocular pilots, which have been observed for 3 consecutive years, are felt
to be real. However, there is no clear indication at this point of the exact

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AO77189

AD

Document {8 available to the public through the
National Technical Information Service,
aaa Springfield, Virginia 22161

: Prepared for ="
U.S. DEPARTMENT OF TRANSPORTATL!
Federal Aviation Administration
Office of Aviation Medicine
Washington, D.C. 20591



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