with Pre-Departure Clearances
Editor's Note: The following
article is a summary of a research paper by Michael Montalvo, a San Jose
State University research associate at NASA Ames. Mr. Montalvo's research
is based in part on work previously published in ASRS Directline #5. You
may request a free copy of the paper from: Michael Montalvo, NASA Ames
Research Center, MS -262-4, Moffett Field, CA, 94035-1000.
In 1990, the FAA instituted the Pre-Departure Clearance (PDC) system at
a number of U.S. airports. The PDC system allows pilots to obtain a clearance
without the need for verbal communication on the Clearance Delivery frequency.
The program's objective of reducing congestion on this frequency has been
met. However, ASRS incident reports indicate that pilots encounter a number
of difficulties in using the PDC system. Two major areas of concern are
lack of confirmation of receipt of the PDC, and lack of standardization
of the PDC format.
Some airports have a confirmation
process built into the PDC system; others do not. The lack of a verification
process (such as the "readback" required if a clearance is obtained
on the Clearance Delivery frequency) leaves no opportunity for the absence
of a clearance to be discovered by the crew, or for an erroneous clearance
to be corrected by ATC. An Air Carrier pilot seemed surprised to discover
- I asked
ATC if there was any way they would know that a crew had received the
clearance via PDC. They said at the present time, there was no back-up.
They assumed that when a flight called for taxi, it had its clearance.
Reporters had many suggestions
for ensuring that PDCs had been obtained, including:
1) Make "Obtain PDC" a specific checklist item. Some checklists
use the item, "Radio/ACARS" as the prompt for obtaining or checking
the PDC. However, there may be other tasks associated with this item,
and the PDC may still be overlooked.
2) Standardize the delivery procedure for PDCs. Most crews receive the
PDC by ACARS; others pick up a printed copy at the gate or have it delivered
to the cockpit by the gate agent. The variable delivery methods at different
airports may provide opportunity for an oversight in obtaining the PDC.
3) Require an aircraft to verify its PDC-obtained squawk code with ATC
when obtaining taxi instructions.
Most pilots are accustomed
to hearing ATC-issued clearances in the format required by the Air Traffic
Control Handbook. However, most airports and airlines arrange the items
of PDCs in different orders, requiring pilots to search for the information
they need. The following reporter recognized this as a significant issue.
- PDC format
is not standardized. It also does not conform with the way clearances
are read to you from Clearance Delivery. Putting "cleared as filed"
up on top followed by the Standard Instrument Departure in the remarks
section is too easy to miss in the last minute flurry of activity at
Another aspect of formatting
includes readability issues. For example, one pilot reported that non-standard
abbreviations are often used for altitude restrictions. He suggested that
critical instructions always be spelled out.
Pilots' recommendations for enhancing readability of PDCs include:
1) Standardize the PDC format to duplicate the ATC format.
2) Mark any changes from "as filed" with ******* or other eye-catching
3) Provide pilots with additional training in reading PDCs.
the Footsteps Of
Readers will note from the number
at the upper left-hand corner of this page that CALLBACK has reached a
new milestone--200 consecutive issues published since July 1979. Seventeen
years ago, the inimitable founding Editor, Rex Hardy, produced this little
two-page blue bulletin and guided CALLBACK through its first 100 issues.
At the end of CALLBACK's second century, it's time to recognize the involvement
of another editorial talent--Marcia Patten.
Ms. Patten has contributed many articles to CALLBACK during the last year,
and next month (with issue #201) will assume the position of Managing
Editor. She is a commercial helicopter pilot and certified rotorcraft
flight instructor, with more than 1,200 flight hours in Hughes, Bell,
and Aerospatiale helicopters. She is also an experienced pilot of general
aviation aircraft. Perhaps as important, Ms. Patten follows in the Hardy
Humanistic tradition, with a B.A. degree in Classics and a Masters in
We hope readers will continue to learn and profit from the incidents presented
here, as the ASRS editorial staff carries on Rex's mission of making CALLBACK
"interesting, instructive, and even--sometimes--entertaining."
Say Again, Say Again...
Communication errors occur
on both sides of the radio. Many errors are corrected during a readback.
Others are transmitted back and forth, compounding their severity. A General
Aviation pilot's experience is not uncommon:
- I arrived
at the hold line before another small airplane. That pilot advised,
"Ready to go, southeast departure." I called in right after,
explaining that I was number one at the hold line. [The Controller's]
response was, "Roger, position and hold," without actually
saying my callsign. I verified position and hold, without actually saying
my numbers as well. I pulled onto the centerline to see an airborne
FAA ILS Check plane approaching me from the opposite end of the runway
at a high closure rate.
The Controller stated for the unauthorized aircraft to remove itself
immediately from the active runway.
The Controller had actually said, "Hold short." I heard "Position
and hold," and even read back that instruction. Anytime there is
the slightest chance for miscommunication, [one should] always verify
to whom the radio call was directed, and mention callsigns with every
readback instead of relying on voice identification.
Don't forget that two clicks
of the microphone do not qualify as adequate identification.
Your Left, Right?
The old Abbott and Costello
comedy routine, "Who's on First," is a well-known example of
how an intended meaning can get lost in the exchange between the speaker
and the recipient. In the following report, the ground crew's hand signals
were at odds with the flight crew's mindset, and a repeated misunderstanding
was the result. An Air Carrier Captain reports:
- Ground man
checked in on the headset prior to departure and briefed a powerback
with a left turn. During the powerback, the ground man gave the signal
for a right turn. Since I was primed by the briefing for a left turn,
I began a left turn. This rightly excited the ground man who stopped
me, brought me forward, and began the powerback again. Again, he gave
the signal for a right turn, and again I turned left. By this time the
ground man was pretty frustrated. We finished the powerback straight
out and the flight departed. Departing, I saw another aircraft on the
taxiway behind us. We would have been nose-to-nose with it if I had
turned as I was trying to do.
The briefing had said a left turn, so even though he was giving a right
turn, in my mind, I had locked into a left turn. The system worked as
it was supposed to the ground man used the proper signals to stop the
aircraft from doing something he didn't want it to do, and got the problem
sorted out. The flight departed without incident or compromising safety.
A good job by the ground man in the face of confusion.
Although the reporter does
not indicate that the problem was a "left/right" confusion,
such errors also occur. Some airlines avoid this issue by requiring the
ground crew to describe the compass direction the nose of the aircraft
will be pointed during the pushback turn.
In response to our recent discussion
of flight crew incapacitation, a letter from an Aviation Medical Examiner
(AME) provided additional information about the AME medication guide.
the AME guide does reference many medicationsthe FAA intentionally does
not publish an all-inclusive "laundry list" of either approved
or non-approved medications. Many new medications are being approved
by the FDA all the time. It would be impossible for the FAA to continually
update such a list in a timely manner.
"[Further], many drugs are approved for certain medical conditions
but not for others. For example, Beta-blockers are commonly used medications
in the treatment of hypertension, and are approved for use by pilots
for this purpose. However, they may also be prescribed for panic attacks,
and in this case it is the underlying medical condition that is disqualifying
"Of course, there are some drugs that are always disqualifying.
These include drugs of abuse and psychoactive drugs such as tranquilizers.
Many of these are reasonably well discussed in the AME guide."
Nugget From an ASRS reporter:
come from wisdom,
Wisdom comes from experience,
Experience comes from bad decisions,
Experience like this I don't need.
ASRS Recently Issued Alerts
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November 1995 Report Intake
- Air Carrier Pilots--1740
- General Aviation Pilots--663