Date: 201910
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: IMC
Weather elements / visibility: Rain
Light: Dusk
Aircraft: Challenger 650
Operator: Fractional
Operating under: Part 91
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: Engine
Reporter organization: Fractional
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Ground Personnel
When detected: Aircraft In Service At Gate
Result: General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Following what we thought was a normal shutdown; I noticed the left engine ITT (Interstage Turbine Temperature) was slowly rising. The rise was very gradual; and if I had just gotten up out of my seat following the checklist I might have missed it. Watching it; I realized something was wrong; and I knew we had been given a similar scenario during initial. I knew the remedy was to dry motor the engine which I started doing before the ITT exceeded limits. I motored the engine; monitoring the slowly dropping ITT while I asked my partner to look for an appropriate checklist. I did not immediately recall the name of the checklist because I had only seen the scenario once during initial; and the simulator presented a very different set of symptoms: instead of the slow rise; the sim presented a much more rapid rise. Once I got the ITT below 150; I stopped motoring; and the ITT began to rise again. This too was different than the simulator scenario; where the fire went out after a single dry motoring. My Partner on IOE (Initial Operating Experience) could not identify an appropriate checklist; so I decided to call the Company for assistance; he got out of the seat and opened the door because line service was trying to gain our attention. They reported seeing a fire on our initial shutdown. On the third dry motoring; while talking with Maintenance; the ITT finally dropped to a normal level; but again began a slow rise. We discussed shutting off the fuel with the fire switch; but by this time the engine had cooled on cycle 5 of the starter. After the immediate crisis I was able to look at the QRC and found that the correct checklist was Tail Pipe Fire. However; that checklist would have had us essentially abandon the aircraft after attempting to dry motor once. At no point did the ITT exceed limits; but I'm fairly certain that the starter limits were exceeded. See recommendationsEmphasize this scenario at training; with a revision to show a much more insidious ITT rise. Revise the checklist to be clear as to how many times the engine should be dry motored before pressing the fire switch; and clarify if dry motoring should take place after pressing the fire switch. Further revise the checklist on what steps to take if the APU is inoperable; or otherwise shut down. Clarify the meaning of the starter limitations; it's described several different ways; which adds ambiguity.




Synopsis: CL-650 Captain reported encountering tail pipe fire after engine shutdown.