Date: 201412
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: MD-83
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: FMS/FMC
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Situational Awareness
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Pre-flight
Result: General Flight Cancelled / Delayed
Contributing factors: Aircraft; Human Factors
Primary problem: Human Factors

Narrative: I started my day receiving the aircraft from another Captain who informed me that there was an MEL on the FMS.  The write up was 'FMS Database Corrupted And Incomplete'.  Maintenance Control applied [a specific] MEL for FMS Navigation Database.  They had taken a delay earlier in the day to update the release to show a VOR to VOR route and change some of the aircraft equipment codes.  My release showed the equipment line as 'MD83/M-SDFGLVW/S and the line showing RNAV departures; enroute; and arrivals was removed as well.   However; the route was filed as the canned route rather than VOR to VOR.  I made a quick call to the Dispatcher and she agreed that it should have been a VOR to VOR route and we amended the release to show that.  After arrival and reviewing the release; I noticed that the equipment coding was the same as the release for my flight up; but the routing wasn't VOR to VOR - instead it had us filed direct to LAMED which is the canned route.  I directed the First Officer to call Dispatch and have it refiled [via] J6.  It sounded like the Dispatcher was confused about why we wanted to do that and they discussed the reasoning for about 5-10 minutes.  After looking at the MEL; the Dispatcher felt we did not need to file a VOR to VOR route and at that point the FO passed the phone to me.  I told the Dispatcher that we were filed on a VOR route on the way up; as well as the previous crew.  He continued to push his opinion that it wasn't required per his interpretation of the MEL.  I then told him that I wanted it filed that way and explained it was a quick fix and since the MEL wasn't very clear we should take the more conservative route.  He indicated it would take more time to redo the flight plan and send the paperwork.  I told him I was fine with amending the release over the phone; but he didn't want to do that. We eventually got the new paperwork and departed.  Later in the flight we discovered that while we were filed VOR to VOR; the aircraft equipment codes had been changed back to the standard and didn't reflect the same as the previous releases.While the Dispatcher may have been correct in his interpretation of the MEL; another Dispatcher and another crew both followed the same procedure as me that day.  The MEL for the Navigation Database seems to be more for databases that are out of currency; not necessarily for one that is 'corrupted'.  Perhaps the entire FMS should have been deferred?  The procedure for [the MEL] says to 'Plan and conduct flight using navigation charts in lieu of FMS Navigation Database'.  While this isn't 100 percent clear; our thought was to have our initial fix be a VOR that we could manually navigate to if needed rather than an intersection in case the corrupted database failed completely in flight.  The Dispatcher felt that all we needed to do was verify that the [latitude and longitude] points in the FMS database matched the release.  Again; while the Dispatcher may have been correct in his interpretation; I felt a more conservative action was required which is why I requested a VOR to VOR route.We would not have taken as much of a delay had the Dispatcher simply refiled the route when asked.  More clarity in the MEL.  Perhaps the MEL applied was the wrong MEL.  Dispatchers to follow a more conservative request rather than argue the point.




Synopsis: A MD-83 Captain reported confusion in the cockpit and in dispatch about the implications of an MEL affecting the FMS database.