Date: 201202
Local time of day: 1201-1800
Location: MMUN.Airport, FO
Light: Daylight
Aircraft: B737 Next Generation Undifferentiated
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Confusion
Anomaly: Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Pre-flight
Result: General None Reported / Taken
Contributing factors: Procedure; Company Policy
Primary problem: Company Policy

Narrative: Round trip to MMUN is normally scheduled for 7:45 flying time with aircraft equipped with life rafts. Flying time for non-life raft equipped aircraft is approx 8:10 and two crews operate the round trip or the crew RON's in MMUN. We arrived at aircraft to find it non-life raft equipped but filed over the gulf beyond 162 NM. We advised the Dispatcher and he re-dispatched the aircraft; with final paperwork arriving at departure time. We hurried to make departure and after takeoff; realized we were probably not legal to make the round trip due to the additional time required for not crossing the Gulf of Mexico. Upon arrival in MMUN; Dispatch was able to produce paperwork which suggested we could accomplish the flight in under eight hours. I'm not sure we actually did the round trip in under eight hours using the 'wheels rolling method' that the company uses for FAR compliance. However; the more troubling aspect of this was Scheduling's insistence that 'legal to start; legal to finish' applied in this case. They argued that because we showed up to work intending to fly under eight hours; we were legal to finish regardless of the circumstances. I believe that as soon as we showed up to work with an aircraft incapable of making the round trip under normal circumstances (non-life raft equipped aircraft;) we were NOT legal to start; therefore; not legal to finish. Clearly the company knows this as all advance pairings where non-life raft equipped aircraft are anticipated for this route is scheduled with either two crews or an RON; and pairings where life raft equipped aircraft are anticipated are scheduled in advance with one crew. I believe Scheduling is stretching the intent of 'legal to start; legal to finish' beyond reasonable. I don't believe Scheduling should consider you having started legally when you arrive at work to find they have assigned an aircraft incapable of legally completing the scheduled round trip. They believe because you showed up to work intending to have an aircraft capable of making the round trip legally; regardless of the fact that the company long ago changed the legal aircraft out. I believe this should be clarified to both Scheduling and flight crews one way or the other.




Synopsis: A B737-NG crew originally scheduled to fly a non EOW aircraft to MMUN over water were rescheduled over land and exceeded eight hours but were told because the original over water flight was less than eight hours they were legal to fly the rescheduled flight.