by Charles Drew

New solutions to old problems sometimes result in a few new problems. Such is the case with Pre-Departure Clearances (PDC's). Getting an IFR route clearance has often been difficult during busy times at major airports, with pilots competing on a congested clearance delivery frequency, and controllers having to read involved, often lengthy instructions. Solution: PDC's.

With a pre-departure clearance, the flight crew of a cooperating air carrier can get their IFR clearance from their company rather than directly from an ATC facility. ATC still issues the clearance, of course, but the transfer of information is directly to the air carrier's dispatch department via teletype, computer link, or other method, rather than by voice communication on an ATC frequency. The air carrier then provides the clearance to the flight crew in the form of a printed message, or via ACARS. But, there have been a few problems.

Don't Leave Home Without It

Some flight crews have departed without an IFR route clearance:

• "After takeoff, I switched to Departure Control as instructed. When I got no response I tried to verify the frequency by retrieving the clearance from ACARS...When I saw there was no PDC message stored I asked my First Officer for the correct frequency from his verbal PDC and he said, eventually, 'Oh-oh, I forgot to get our clearance.' " (ACN 198736)

And from another reporter:

• "Shortly after takeoff, ATC told us to change transponder code. We complied, then checked pre-departure clearance (PDC) for assigned squawk. Couldn't find paper, even though all other paperwork was located. We either lost the PDC or never received it." (ACN 208027)

Wrong, Wrong, Wrong

Sometimes flight crews misread or misinterpret PDC's.

Wrong Flight

One variation of the PDC problem is getting a PDC meant for another flight:

• "We receive our PDC's with our flight packets containing release, weather, NOTAMS, and flight data sheet. During review of the packet, I did not notice that our PDC did not match our flight. After takeoff, Departure Control gave us a correction to our transponder code. We corrected the code as requested and the PNF checked the code on the PDC and showed it to me...I did not notice the wrong flight number, having my...attention on flying...the Controller notified us that the code originally used was for...flight XXX -- the PDC in our possession, but not our flight YYY. The mix-up was verified and the flight continued without incident. The mix-up was also not noticed by the other crew. Therefore, the error went undetected by the original agent and four crew members." (ACN 192294)

Wrong Leg

Pilots of flights with multiple legs face another potential problem:

• "Our flight (BOS-PWM) received the wrong departure (PDC) clearance in BOS. It had the proper flight number and date, but was the PDC for the ATL-BOS leg. When transponder code was reported wrongly off the PDC, they only said, 'change squawk to read xxxx,' thus not alerting the crew to the error. After takeoff, crew found out altitude cleared to was wrong also, but did not violate any altitudes. Coordinated with...ATC, company flight control and...operations to find error causes and correct." (ACN 179596)

Wrong Day

It's even possible to get a PDC for the correct flight number, but the wrong day:

• "I picked up our pre-departure clearance at the counter in the terminal area about 15 minutes before departure...I reviewed the clearance as I fought my way through the packed jetway to the cockpit. As I entered my seat and began to review the departure and planned route of flight, the APU shut down on its own. There was no external power plugged in and no ground personnel in sight. I let the F/O continue cockpit setup and went in to operations to get ground power hooked up and a mechanic to look at the APU. When I got back to the cockpit, we ran the pre-departure checklist, started engines, and taxied for takeoff. ...after takeoff when Tower cleared us to Bay Departure Control with a turn to 030 degree heading, we questioned which departure we were assigned. Tower impatiently informed us we were on the San Francisco 6 which we then complied with. Later, reviewing our pre-departure clearance, I found the problem was [that] the pre-departure clearance I was given was for March/Sunday, not March/Monday...There's no excuse for my missing the date on the pre-departure clearance, but I thought this was another example of how a series of events can lead to a hazardous situation." [Emphasis added.] (ACN 236984)

Changes Not Noted

Another of the problems noted in PDC incidents is that flight crews fail to note changes on the PDC to their filed or "usual" route:

• "Climbing out of SLC enroute to LAX. ATC cleared us direct to FFU, flight plan route. After passing FFU and proceeding on what we thought was our flight plan route, ATC asked us what our routing was. We doubled checked our PDC and realized we had misread the clearance." (ACN 218473)

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)

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. Thirty-three 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 non-incidents 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).

Types of PDC Problems

Figure 1 shows the types of problems and human errors experienced by flight crews in PDC incidents. Note that this category allowed multiple responses to a single question, so there are more citations (69) than reports (42) in the data set. The biggest problem appeared to be failure on the part of the flight crew to adequately read the PDC, and/or to note changes in the PDC.

Transponder Verification

In an effort to ensure that a flight has received the proper IFR clearance, some facilities require the flight crew to read back the PDC transponder code on Clearance or Ground frequency prior to departure -- this can catch many potential PDC problems. Other ATC facilities, however, do not use this verification procedure. In 17 of 18 instances in which data was available, there was no transponder code verification procedure. Table 1 provides further detail.

Many pilots are confused about the "chain-of-responsibility" in the pre-departure clearance process. Note the following ASRS report:

• "Forgot to get ATC route clearance through ACARS...taxied out on Ground Control. No mention of lack of clearance! Took off ...on Tower frequency. No mention of lack of clearance! Switched to Departure Control. Again no mention of lack of clearance! They told us to squawk yyyy as compared to zzzz. We did. That was our first clue that something wasn't right. I checked our ACARS messages and found no ATC PDC. Nothing was ever said to us one way or the other!" (ACN 205530)

It is important to remember that ATC, having issued the PDC to the company, may or may not get an acknowledgment of the company's receipt of the PDC. ATC certainly will not know if the flight crew has received the PDC from company dispatch unless they (ATC) use some sort of verification procedure.

Recommendations

Review of these PDC incident reports leads to a number of suggestions for all parties involved in PDC transactions.

Pilots

1. Check for Clearance: PDC's introduce a new variable in cockpit management -- how and when a clearance is received. As one reporter notes, "...many airports do not have PDC's, so it is not an acquired habit to check for a PDC..." (ACN 218886) Adding an "ATC clearance received and reviewed" item to the written checklist may help assist pilots' memory until the process is routine.
   
   
2. Look for Errors: Is the PDC for the right flight number? For the right trip segment? For the right day and month? Scanning carefully for such errors may prevent an embarrassing incident.
   
   
3. Look for Changes: Are the PDC and the filed route the same? Sometimes PDC formatting and presentation, whether on ACARS or a printed sheet, can make detecting such changes difficult, so it is important to review the PDC carefully.
   
   
4. Practice CRM: Good cockpit management and crew coordination techniques can help catch potential errors. In the words of one reporter: "I have now selected a place in the cockpit preparation flow where the PDC message (or radio delivered clearance) will be reviewed by both pilots, and critical information set in proper windows for departure." (ACN 194740) Are flight crew members in total agreement on what the clearance is? If not, stop the flow and resolve the discrepancy.
   
   
5. Query ATC: Getting a transponder code change from ATC shortly after departure might be an indication that there is a PDC clearance misunderstanding. If there is any question about the clearance, ask your friendly controller for help.
   
   
6. Reset The Transponder: Resetting the transponder to 0000 (four zeros) after landing can help you, or the next crew, detect lack of a PDC. Additionally, should a flight depart without setting an appropriate IFR code on the transponder, ATC will be more likely to quickly detect the problem. (Setting 1200 on the transponder may lead a controller to believe the target is normal VFR traffic.)

Air Carrier Flight Departments

1. Review PDC Format: Is the PDC (whether using ACARS or a printed message) readable, clear, concise, and consistent, or do flight crews need to look in different places to "piece together" their clearance? Perhaps having the clearance displayed in a linear, cohesive manner will reduce the opportunity for misinterpretation. It may be possible to highlight changes to the filed route in bold type or in some other manner. Similarly, placing the actual, full route clearance at or near the top of the message could help.
   
   
2. Provide PDC Training: It is recommended that air carriers provide instruction to flight crews (during scheduled initial and recurrent training sessions) in the use and interpretation of PDC's.

FAA/ATC Facilities

1. Transponder Code Verification: Use of clearance verification by requiring the flight to read the transponder code appears to be effective where used. In the words of one pilot:

• "...one thing that might be done to prevent departing without a PDC would be to standardize the way PDC's are acknowledged, such as in ORD where you relay your assigned transponder code to Clearance Delivery." (ACN 207872)