Date: 202005
Light: Night
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Parked
Aircraft component: Data Transmission and Automatic Calling
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Dispatcher
Reporter qualification: Dispatch Dispatcher
Human factors: Communication Breakdown; Time Pressure; Confusion
Anomaly: Aircraft Equipment Problem Less Severe; Airspace Violation All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Dispatch
Contributing factors: Aircraft; Airspace Structure; Staffing; Procedure; Environment - Non Weather Related; Company Policy
Primary problem: Aircraft

Narrative: The Captain operating Flight AB contacted flight control over SATCOM to request to speak with Dispatch and Maintenance regarding the malfunction of their CPDLC. Maintenance told the crew that if they preferred they could issue an MEL to defer the CPDLC; as long as the Captain and dispatch agreed it was deferrable. The Captain wanted to continue with the deferral and I stated that I would review the route; NOTAMs and Jepp to verify there were no restrictions.  The first step I took was to review the enroute NOTAMs over waypoint ZZZ VOR because that is a known hotspot.  There was a NOTAM for ZZZ1 VOR that stated 'If' the aircraft was capable of logging onto CPDLC that it was preferred for that route.  I interpreted the wording of the NOTAM to mean that it was preferred; but not required. To continue my investigation of the NOTAM over ZZZ1 I searched 'CPDLC' in the state rules and procedures for Country X in the Jepp airway manual text.  Under 'Route 1234; Y1; Y2 procedures' it states 'data link service; CPDLC/ADS-C; is applied to the Routes 1234 [ZZZZZ-ZZZZ]; Y1 and Y2.' And then there is a table for 'Country mainland data link routes operational conditions' and lists CPDLC requirement; again; only for 1234; Y1 and Y2.   Then I searched CPDLC for the rest of the state rules and procedures for the countries along the rest of the route and referenced an email from the training department that confirms that our aircraft; can operate in Continent X with no FL restriction with CPDLC inop. Then I confirmed to the Captain that I could not find any restrictions preventing us from using the deferral and continuing the flight as planned. The CPDLC deferral does require the ATC strip to be modified to reflect the loss of CPDLC; so I attempted to rerun the flight plan; but LIDO was not able to rerun the flight plan and gave an error message that there were no available FL on airway X111. When I reviewed the enroute NOTAMs for X111; there was an airway restriction up to FL310; and I mistakenly assumed that LIDO was misinterpreting the NOTAM and restricting the entire airway then in perfect storm timing the enroute airway restriction NOTAM was canceled and I reran the flight plan (and assume that I mistakenly reran the flight plan without the MEL applied) and was able to run the flight plan on another OFP; confirming my belief that it was just a misinterpreted NOTAM by LIDO.  Then I wanted to be certain that I did not mess with the planned fuel or planned altitudes by simply canceling and refiling the ATC strip on the filed OFP instead of sending a whole new flight plan with a new OFP this was to prevent accidentally changing any current info; due to the flight being ready to block for departure; and also to receive acknowledgment from all countries listed under the ATC filing; which I did receive acknowledgment and no reject from all of them. It was not until I came in the next day that I was informed by a Senior Dispatcher that there were two RNP4 airways that were on the route; X111 ZZZZ1 to ZZZZZ2; and Y999 ZZZZZ2 to ZZZZZ3. I quickly realized that I had been scanning for any restrictions to CPDLC and not also looking for restrictions to RNP4 (which would have led me straight to the RNP4 routes listed in the airway manual text).My suggestions moving forward after reviewing this situation. I felt pressure due to time constraints because 1) The flight was nearing their ETD and the route for ZZZZ1 to ZZZZ2 is notorious for airway closures and I did not want to risk possibly delaying into them; 2) The flight was ready to block and if it was possible to continue with the deferral then I did not want to cause a delay; 3) The Continent X desks (at least mine) are seemingly always setup with flights departing very close to the same time.  I was also responsible for Flight AC ZZZZ3-ZZZZ2 and XXX ZZZ-ZZZZ2 which both departed within an hour of each other and I was already almost an hour and a half behind on planning due to the ZZZZ1 deferral and there are multiple NOTAMs to review for XX and XXX can be time consuming to find an efficient route to cross that is also approved by [foreign ATC]. In fact I had to notify the Supervisor that it was possible that I would not have XXX paperwork submitted in time; but was able to barely make the 2 hour deadline.The next issue was that due to coronavirus separations I was the only dispatcher in Continent X control in my building so I did not have anyone directly next to me to start the dispatch release process and failed to ask my fellow dispatchers on the ocean side for assistance. Lastly; guidelines for constant issues with CPDLC freezing state that if the CPDLC freezes before departure to contact maintenance and have them accomplish the circuit breaker reset procedure. So from now on I will insist that maintenance follow through with this procedure instead of defaulting to a deferral.




Synopsis: Dispatcher reported re-routing issues associated with the deferral of a flight's CPDLC system.