Review of the individual accident records revealed the following informa-
tion: (i) Only two agricultural accidents involved monocular pilots. One
involved fuel exhaustion during a swath run and, in the other, the pilot
taxied into another aircraft; both were nonfatal. The FAA accident investi-
gator noted the medical defect in his report of the taxiing accident, advised
the Regional Flight Surgeon, and recommended reevaluation of the pilot through
medical flight test procedures. (ii) Vision was noted by the authors as a
possible causal factor in 7 more of the 35 accidents involving monocular
pilots; however, in each case, the FAA investigator documented the defect but
did not associate it with the cause of the accident in the narrative report.
(iii) Of the 35 accidents involving pilots with blindness or absence of one
eye, 9 of 35 were fatal; 3 occurred at dusk; 6 occurred at night; 6 of the 9
fatal accidents occurred under conditions of darkness, fog, rain, or haze;
there were no midair collisions; and 14 of the 35 accidents occurred during
landing, 3 while taxiing, and 10 on takeoff. (iv) Deficient color vision
was not cited in the accident reports or considered a likely cause by the
authors in any of the 61 accidents experienced by the pilots with deficient
color vision but no restrictions. Of this group, 7 accidents were fatal, 6
accidents occurred at dusk and 7 at night, 22 accidents occurred on approach
and landing, and 12 involved agricultural operations; there were no midair
collisions. (v) The records for the defective distant vision group were not
examined, but it is known from the agricultural operation accident records
that 20 of the 144 accidents occurred during ag operations.

IV. Discussion.

Despite additional studies (2,3) and anecdotal evidence that report normal
flying performance by monocular pilots, and our findings that the increased
accident experience by this group in 1974 might be due to increased exposure,
we now find on examining the 1975 accident data in greater depth that these
pilots had a larger number of accidents than was expected, possibly because
of their defects in some cases, and a significantly higher accident rate that
was real and reproducible. Vision was cited as a possible cause in only 1 of
the 35 accident reports. Again, as in the previous year, more accidents were
observed than were expected at night and on landing. However, agricultural
accidents, which were of particular concern in our earlier study, were reduced
from six to two for this category. Mayer and Lane (4) have found that monoc—
ular pilots in Australia were involved in more hazardous events than were
control pilots.

Some statistical artifact may explain the varied findings for the
deficient color vision without restriction group. Since review of each of
their accident reports failed to find any operational significance for their
defect, there seems to be little reason for concern. However, there were
more accidents than were expected empirically at night, on approach and
landing, and during ag operation.





Total and last-6-months civilian flight hours, reported at the times 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, and those with deficient color vision,

Medical record printouts are routinely obtained on receipt of accident
notification from field sources. This file provided the medical and exposure
source data for the accident-involved airmen. Prevalence data for the
population are available annually from computer analyses. Conventional chi-
square analysis was applied during the first phase of the analysis in order
to identify the static defects showing significant difference at probability
level 0.10. Since this project is designed to screen for potential medical
factors of importance in the epidemiology of accidents, a higher level of
significance was chosen to decrease the chances of wrongly accepting a hypoth-
esis of no difference between the accident experience of those with and
without the defect. Accident rates per hundred thousand hours of cumulative
and recent flight time were computed for the three static defect categories
identified as significant by previous analysis and repeated in this study.
Rates for the static defect groups were then compared with population experi-
ence by a critical ratio rate test.

Additionally, exposure and defect-specific rates were analyzed for trends.
These comparisons were based on a December 31, 1973, population estimate
(not specifically obtained for this study) that provided frequencies for
exposure intervals of 0-10, 11-50, 51-100, 101-200, and more than 200 hours
of recent flight time and 0-10, 11-50, 51-200, 201-1,000, 1,001-2,000, and
more than 2,000 hours of cumulative flight time from a sample. Persons
having accidents in 1975 would have received medical certification in the time
period from January 1973 to December 1975. The December 1973 data, while
slightly out-of-phase with the midpoint of this study (July 1974), is not
expected to produce appreciable bias because of the stability of the popula-
tion during this time period. The July 1974 population total was 756,004
versus a December 1973 total of 758,243.

Finally, the records for all accidents involving agricultural operation,
a "one eyed" pilot, or a pilot with deficient color vision but no operational
limitation were reviewed by both authors to determine if medical conditions
had been considered by the accident investigators, visual factors played a
significant role in agricultural accidents, or time of day, phase of flight,
nature of the accident, or other findings offered any plausible explanation
for the increased accident experience of these groups.

III, Results.

The number of active airmen in each of the eight categories and their
accident experience in 1975 are shown in Table 1. The 1974 data are included
for comparison. Again, the same three categories had more than their expected
numbers of accidents--deficient color vision with no restriction (significant

2


Deficient distant vision does not appear to be associated with an increased
accident rate. This is consistent with another recent study of FAA data (5).

The contact lens group should receive special attention in a study of the
1976 accident data because marginal significance was found on analysis of the
1975 data, exposure data were not programed and accident rates could not be
calculated, and, after 1976, this group will not carry a pathology code or
require a waiver and thus will be difficult to study.

The accident rates that we have calculated are accidents in 1 year per
100,000 flight hours reported for 6 months and total civilian experience. A
more conventional calculation would be accidents per 100,000 flight hours in
1 year, which would give one-half the values shown in our "last 6 months"
column (Table 2). However, the relationship between the three pathology
categories and the total airman population would remain the same and we feel
that fewer problems are associated with this method of analysis than with an
arbitrary extrapolation of recent flight time as currently reported.

V. Conclusions.

The increased accident experience of monocular pilots, which was observed
in 1974 and again in 1975, appears to be real after analysis of accident
rates per unit of exposure and examination of accident reports. Blindness or
absence of either eye, contact lens use, and color vision defects with no
restriction are deserving of special attention in analyzing the 1976 aircraft
accident data; there appears to be little need to pursue the other five
pathology categories on an annual basis.

In view of studies that show normal flying performance by monocular
pilots and the paucity of accident/defect correlation in accident investiga-
tions, no changes in medical policies or standards seem indicated at this
time. Further attention through medical flight tests, education, and accident
investigation, in addition to data analysis, are planned.


Technical Report Documentation Page

T. Report No. 2. Government Accession No. 3. Recipient's Colelog No.
FAA-AM-77-20
& Title and Subtitle 3. Report Date
The 1975 Accident Experience of Civilian Pilots August 1977
With Static Physical Defects 6. Performing Organization Code
hes [8. Performing Organization Report No.
J. Robert Dille, M.D. and Charles F. Booze, Ph.D.
9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)

FAA Civil Aeromedical Institute
P.O. Box 25082
Oklahoma City, Oklahoma 73125

Ti. Contract or Grant No.

13. Type of Report and Period Covered

12. Sponsoring Agency Name and Address
Office of Aviation Medicine
Federal Aviation Administration
800 Independence Avenue, S.W. T4. Sponsoring Agency Code
Washington, D.C. 20591 FAA

15. Supplementary Notes

16. Abstract
The 1974 aircraft accident experience of civilian pilots with eight selected statid
physical defects has been examined and reported previously. Three categories--
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 or accident airmen without selected pathology. Concern was
raised about the failure to relate any of the 416 accidents to the pilot's physi-
cal condition in the accident reports.

The 1975 accident data have now been examined. Again, the same three groups were
found to have significantly more than their expected numbers of accidents. This
year the reported recent and total flying times for all airmen with these defects
were determined and accident rates were calculated. When the accident experience
of airmen with any of these three static defects was compared with the active
airman population accident experience per unit of recent and cumulative exposures,
the rates for airmen with blindness or absence of an eye were still found to be
significantly higher. Rates for airmen with color vision defects and a waiver werg
somewhat higher but of marginal significance. However, the rates for those with
defective distant vision other than blindness or absence of an eye were similar
and the difference was not significant. Only one of the FAA accident reports that
were reviewed related the accident to the pilot's physical defect.

17, Key Words 18, Distribution Statement
Document is available to the public
Flight Safety through the National Information
Accident Investigation Service, Springfield, Virginia 22151
19. Security Classil, (of this report) 20, Security Classif, (of this page) 21. No. of Pages | 22. Price
$3.00 PC
Unclassified Unclassified 7 .95 ME

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



REFERENCES

Dille, J. Robert, and Charles F. Booze: Accident Experience of Civilian
Pilots With Static Physical Defects. FAA Office of Aviation Medicine
Report No. AM-76-7, 1976.

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

Lewis, C. E. Jr., W. R. Blakeley, Ram Swaroop, R. L. Masters, and
T. C. McMurty: Landing Performance by Low-Time Private Pilots After
the Sudden Loss of Binocular Vision--Cyclops II, AEROSPACE MED.
44:1241-1245, 1973.

Mayer, H. B., and J. C. Lane: Monocular Pilots--A Followup Study,
AEROSPACE MED. 44:1070-1074, 1973.

Ryan, Leonard C., S. J. Gerathewohl, Stanley R. Mohler, and Charles F.
Booze, Jr.: To See or Not to See: Visual Acuity of Pilots Involved in
Midair Collisions. FAA Office of Aviation Medicine Report No. AM-75-5,
1975.





THE 1975 ACCIDENT EXPERIENCE OF
CIVILIAN PILOTS WITH STATIC PHYSICAL DEFECTS

I. Introduction.

The 1974 aircraft accident experience of civilian pilots with eight
selected static physical defects has been examined and reported previously (1).
Three categories--blindness or absence of either eye, deficient color vision
with a waiver (and no operational limitations), and deficient distant vision--
had significantly more accidents than were expected on the basis of observed-
to-expected ratios. However, pilots with these three conditions who had
accidents reported considerably higher median 6-month flight times at the
times of their last physical examinations before their accidents than did an
active airman population sample or accident airmen without selected pathology.
Determination of the role of exposure by calculation of accident rates was
not attempted. More accidents were observed than were expected at night,
during landing, and in agricultural operations. The pilot's physical
condition was not related to any of the 416 accidents in the accident reports.

Plans were made to calculate accident rates and to examine individual
accident reports for 1975 to further explore these observations and determine

their significance.
II. Method.

For the 1975 active airman population of 763,793, the numbers were deter-
mined who had blindness or absence of either eye (includes uncorrectable
distant 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; deficient color vision but had not taken
or passed a signal light gun test and had a restriction "not valid for night
flight or color signal control"; deficient distant vision (uncorrected
distant vision poorer than 20/100 for first and second class, or vision that
does not correct to standards for any class); paraplegia (special controls
required on the aircraft); deafness with a restriction prohibiting flying
where a radio is required; and amputations (some with a requirement for the
use of artificial limb(s) while flying or for special controls on the
aircraft). The deficient distant vision category ordinarily includes many
who also have lost an eye and some who wear contact lenses, but these were
subtracted for this study.

For each of these eight categories, the representation per 1,000 active
airmen, expected frequencies for 4,181 total accidents, actual accident
experience, ratio of observed-to-expected accidents, and significance by the
chi-square test were calculated.