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marshaler is lost from sight, a “no
taxi” situation again exists.
• Use wingwalkers if ramp congestion
is even a remote consideration.
One is good; two are better.
However, consider that the
marshaler may be focusing on the
nosewheel position rather than
watching the wingwalkers.
• Be aware that the marshaler may be
unable to see wingwalkers.
• Recognize that ground crews may
be unable to communicate verbally
with each other or with vehicle
drivers.
• Finally, in the words of a United
Kingdom Flight Safety Committee
member, remember that “during
ramp operations, everything is
alright until is isn’t alright!” _
20 Issue Number 8
ASRS
Database
Statistics
ASRS codes descriptive characteristics
of every report
it receives and places that information
in a computerized database.
We code the function of the person
who submitted the report; the place
and time of the reported incident; and
the descriptive nature of the occurrence.
Following are 13 pages of
graphs and statistics portraying these
and other data.
Time Frame
The data presented are for two specific
time periods—a 1-year period
from January 1994 through December
1994, and a 7-year period from January
1988 through December 1994. The
reader will see that, with few exceptions,
the 1-year and 7-year data are
remarkably similar, with few changes
in percentages.
Relationship of ASRS Data to All
Aviation Incidents
ASRS reports are voluntarily submitted
and are not obtained through a
statistically valid sampling process.
Thus, the ASRS cannot specify the relationship
between its database and
the total volume of aviation safety incidents
that occur, nor can it say with
certainty that this relationship has remained
fixed over time. This is known
as the self-reporting bias problem.
However, the ASRS can say with certainty
that its database provides definitive
lower-bound estimates of the
frequencies at which various types of
aviation safety events actually occur. For
example, 34,404 altitude overshoots were
reported to the ASRS from January 1988
through December 1988. It can be confidently
concluded that at least this number
of overshoots occurred during the
1988-94 period—and probably many
more. Often, such lower-bound estimates
are all that decision makers need
to determine that a problem exists and
requires attention.
Known Biases
We are aware of two prominent factors
that bias ASRS statistical data. The
first is the relatively high number of
reports received from pilots (currently
about 96 percent of ASRS report intake)
versus controllers (roughly 3 percent).
This imbalance causes the ASRS
database to have many more records describing
pilot errors (altitude deviations,
runway transgressions, etc.) than controller
errors (operational errors, coordination
failures, etc.).
The second biasing factor is the
computerized error detection capabilities
at FAA Air Route Traffic Control
Centers (ARTCCs). These are very effective
at capturing altitude and track
deviations that result in a loss of aircraft
separation. Thus, the ASRS receives
disproportionately large
numbers of reports describing these
kinds of events, mostly from pilots.
Statistical Charts
Year of Occurrence ..... 22
Reporting Sources ...... 23
Month of Occurrence.. 24
Weekday of
Occurrence ................. 25
Time of Day of
Occurrence ................. 26
Involved Facilities ........ 27
Involved Airspaces ...... 28
Anomalies (Top Level
Categorization) ........... 29
Airborne Spatial
Deviations & Conflicts . 30
Ground Incidents ......... 31
Non-Adherence to Rules
& Requirements .......... 32
Other Aircraft
Anomalies ................... 33
ATC Handling
Anomalies ................... 34
Introductory Note Regarding ASRS Database Statistics
Issue Number 8 21
Number of Reports vs.
Number of Incidents
Many incidents are reported by more than one individual.
For example, an incident may be reported by a pilot
and a controller, several pilots and several controllers,
the entire flight crew of a given aircraft, and pilots of
more than one aircraft. In 1994, ASRS received 32,272 reports
describing 26,413 unique incidents; thus, 5,859 reports
were “secondary,” in that they described incidents
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