曝光台 注意防骗
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Here is a problem where the flight crew amended
their route for operational considerations, but
didn’t catch the fact that ATC apparently didn’t
have the requested change:
✍ “…The original aircraft never left the
hangar due to a mechanical problem. We
were about an hour late when maintenance
switched planes. The new aircraft was not
overwater equipped, so the computer flight
plan changed from overwater to an inland
routing. Although the aircraft had several
items inoperative and an originating preflight
[inspection] had to be done, I felt we
could still make the connecting complex at
our destination hub if we moved right along.
The clearance came out of the aircraft printer.
It started out the same as filed and the route
[was] loaded into the aircraft [FMS]. What I
failed to see was the clearance went out over
the water down-line, diverging from the filed
inland route. We received direct clearance to
a fix past the point where the filed and the
clearance route split. Approaching our clearance
limit, the next controller was unable to
take us. We quickly verified our filed routing
with controller and were then cleared as
filed. During preflight I had thought the filed
routing and the printed clearance were the
same because, at first glance, they looked
identical. It’s what a fellow thinks he knows
that hurts him.” (ACN 235894)
6 Issue Number 5
Confusing Format
Some reporters claim that the format or structure
of their printed or ACARS downloaded
PDC has led to misinterpretations, or to overlooking
important amendments to their filed
route. One Captain notes the format problem
following a track deviation after takeoff:
✍ “…as we inspected the pre-departure
clearance more carefully, we found that on or
near the top [of the printed PDC] was the
filed route. Several lines down we found the
[actual] clearance. Because of other pressures
on the crew at departure time, i.e.,
checklist completion, ACARS entries, cockpit
to ground crew communications, etc.,
there was a tendency to give a higher priority
to the top line of the pre-departure clearance
message than to lines farther down where
the clearance routing is located…We hope
that the PDC can contribute to safety and
smooth flow instead of degrading them.”
(ACN 193587)
Even the physical printing of the PDC can lead
to problems:
✍ “The pre-departure clearance (PDC) was
received with the filed clearance on it and
further down a change of route…Received
PDC late (at push time) and attached to
another report (final weather or weight and
balance). The report had the ATC clearance
printed at the perforation in the paper. Just
below was the filed clearance. Read filed
[route] vice ATC [clearance].” (ACN 207371)
And finally:
✍ “…initial heading, altitude and squawk
are buried among other nonessential verbiage.
Need better format to highlight critical
information since readback is no longer
required.” (ACN 195504)
ASRS Analysis
In order to develop a better understanding of the
frequencies with which these events occur, we
reviewed 42 reports that described problems
with PDC’s. We also examined the consequences
of PDC errors.
PDC Error Consequences
In 20 instances in 42 reports, a track or heading
error resulted from a PDC error, while an altitude
deviation was cited in 7 instances. There
were 14 instances where the flight appeared to
depart without an IFR route clearance. Thirtythree
of 42 reports provided some evidence that
a breakdown in cockpit coordination contributed
to the incident.
Who Caught the Error
One of the factors we looked at was whether the
error was discovered before departure or after.
In 37 of 42 incidents, the PDC problem was
discovered after departure. Perhaps this
shouldn’t be surprising, in that errors discovered
before departure may be considered nonincidents
by pilots and therefore unworthy of
reporting to the ASRS.
A PDC error was more likely to be caught by the
controller (17 of 42 incidents) due to a route or
altitude discrepancy than for any other reason.
The second most frequent means of error detection
was by the flight crew due to a transponder
code discrepancy (11 of 42 reports).
PDC‘s — The Problems with Pre-Departure Clearances
Issue Number 5 7
Types of PDC Problems
Figure 1 shows the types of problems and human errors
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