Date: 201908
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Challenger 350
Operator: Fractional
Operating under: Part 91
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground ZZZ
Aircraft component: Fire Protection System
Component problem: Malfunctioning
Reporter organization: Fractional
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Situational Awareness
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Taxi
Result: General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: MEL; Manuals; Aircraft
Primary problem: Aircraft

Narrative: During taxi; the FIRE SYS FAULT CYAN EICAS (Engine Indication and Crew Alerting System) came on. This was noted by the PF (Pilot Flying); and he advised me of it. I was about to contact ATC for our departure clearance; that's why I did not immediately noticed the EICAS. We parked the aircraft in the turning bay to do our checklists. We then looked up the MEL (Minimum Equipment List). After reading the MEL and consulting with my Co-Captain; we made the decision to return to the ramp and contact Maintenance. After speaking to Maintenance we AOG'd (Aircraft on Ground) the aircraft instead of using the MEL. The reason was that in my opinion; the MEL is poorly written and does not allow us to legally take off; even though this is 'only' a CYAN EICAS and not an AMBER EICAS message. There is a note at the bottom of the MEL stating that 'Repair all FIREX failures causing FIRE SYS FAULT advisory message.' In our opinion we cannot take off with the MEL applied since the FIREX system failure that caused the FIRE SYS FAULT message has not been repaired. The aircraft fault history and B-code indicated an L ENG FIRE LOOPB FAILED/WIRING and the Diagnostic Data said a SHORT CIRCUIT. The next morning we arrived at the airport to preflight a different aircraft. We noticed that a mechanic was working on the [aircraft]; he came over and talked to me about the incident. He was asking how it happened; and I explained that it happened exactly as I wrote it in the logbook write-up. He asked if we had done a Fire Test perhaps. I answered that we did not; we do not do the test when doing the cockpit checks; let alone during taxi. He again asked how this EICAS could have happened and I explained again that it happened exactly as my write-up and I could not give him any other information that may be useful to him. It sounded like he was very frustrated because he was out working on the aircraft the whole night and could not find the cause of the problem. Shortly after; I received a phone call from the Fleet Director. He talked to me about the write-up and explained that this should not have been an AOG; but an MEL since there is an MEL for this CYAN EICAS. He further explained that it was only a redundancy in the system; and the note at the bottom of the MEL is a carry-over from the Master Maintenance Manual. I appreciated the Fleet Manager's phone call but I also gave him my opinion and my reasoning for the AOG. I said something along the lines of that we do not have the master manual in front of us; all we have to go by is the MEL. And that I find it poorly written. The way I interpret it is that we need to have all FIREX system failures that caused the CYAN EICAS advisory message to be fixed. So therefore I cannot take-off knowing that a part of the system has failed. The Short Circuit of the L ENG FIRE LOOP B in this case. This is the second time this has happened to me. The first time was on 04/2019. On that occasion I also AOG'd the aircraft after a 3 way consultation with Maintenance; the ACP (Assistant Chief Pilot) on duty; and the Maintenance Liaison. I asked the Fleet Manager also how often this has been occurring and he mentioned 4 times in the last 6 months. 2 of those AOG's were done by me. I got the feeling that's why the Fleet Manager thought it necessary to give me a call. Again; I can appreciate the call; but I still feel that I am put in a difficult position with this poorly written MEL. I saw no other recourse on both these instances than to AOG the aircraft. I checked the Mobile Manager on the Waypoint app during the rest of the day; and noticed that at some point Maintenance had written 'Item is hard failed'. So that to me proves that AOG-ing the aircraft was a legitimate action. Please look into the CL-350S MEL 25-XX-XY FIREX System.




Synopsis: CL-350 Captain reported a fault with the Engine Fire Detection System.