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B757 captain discovered his cleared pre departure clearance route including the identifier 'Q1' could be programmed and accepted by the FMC in two distinctly different ways; only one of which was correct.
| Attributes | |
| ACN | 838784 |
| Time | |
| Date | 200906 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | SEA.Airport |
| State Reference | WA |
| Aircraft 1 | |
| Make Model Name | B757-200 |
| Operating Under FAR Part | Part 121 |
| Route In Use | Airway Q1 SID ELMAA |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | FMS/FMC |
| Person 1 | |
| Function | Captain Pilot Not Flying |
| Experience | Flight Crew Last 90 Days 150 Flight Crew Total 16000 Flight Crew Type 3000 |
| Events | |
| Anomaly | ATC Issue All Types |
Narrative:
Pre departure clearance cleared route was sea elmaa Q1 pye sfo. This is an ambiguous clearance which I resolved prior to departure; but am writing this as it is a serious possibility that it could cause an accident in the future. Q1 is both a route (a 'quick route' RNAV airway) and a fix... I.e. It can be programmed to either the left side or the right side of the FMC and will appear as a valid routing and you would have no way of knowing which is correct. If selected as a route; the route reads elmaa; then along the Q1 routing to pye. If selected as a fix; the route reads elmaa; then direct to Q1; then direct to pye. The way the routing reads on the pre departure clearance; either could be correct. Fortunately for me; the point Q1 is way out of the way (N5842.6m W09830.3 in northeastern canada) so it was obvious; but if we had started out somewhere else; it would have been less obvious. So; ATC needs to either rename the point or rename the route; so both are not the same; else; the potential exists for a future flight to go the wrong way and possibly end up in real trouble.
Original NASA ASRS Text
Title: B757 Captain discovered his cleared PDC route including the identifier 'Q1' could be programmed and accepted by the FMC in two distinctly different ways; only one of which was correct.
Narrative: PDC cleared route was SEA ELMAA Q1 PYE SFO. This is an ambiguous clearance which I resolved prior to departure; but am writing this as it is a serious possibility that it could cause an accident in the future. Q1 is BOTH a route (a 'quick route' RNAV airway) AND a fix... i.e. it can be programmed to either the left side OR the right side of the FMC and will appear as a valid routing and you would have no way of knowing which is correct. If selected as a route; the route reads ELMAA; then along the Q1 routing to PYE. If selected as a fix; the route reads ELMAA; then direct to Q1; then direct to PYE. The way the routing reads on the PDC; either could be correct. Fortunately for me; the point Q1 is way out of the way (N5842.6m W09830.3 in Northeastern Canada) so it was obvious; but if we had started out somewhere else; it would have been less obvious. So; ATC needs to either rename the point OR rename the route; so both are not the same; else; the potential exists for a future flight to go the wrong way and possibly end up in real trouble.
Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.