Date: 201811
Local time of day: 1801-2400
Location: DTW.Airport, MI
Flight conditions: IMC
Light: Night
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B DTW
ATC / advisory: TRACON D21
Reporter organization: Air Carrier
Reporter function: Captain; Check Pilot; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Training / Qualification; Workload; Situational Awareness; Time Pressure
Anomaly: Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Contributing factors: Aircraft; Human Factors
Primary problem: Human Factors

Narrative: We were on a short flight to DTW; this was day three of initial IOE for the First Officer. Prior to departure; while the airplane was being deiced; we briefed the approach that we were expecting in DTW based off of the current ATIS. We were expecting the ILZ Y approach that uses an offset localizer and final approach course; but thankfully IS the ILS that is actually contained in our FMS database. While enroute; the new ATIS and the Approach Controller informed us that we would (instead) be executing the ILS Z approach; which is not included in our database.The First Officer is new and was struggling to deal with the many speed and altitude changes being issued by ATC while maintaining enough thrust to keep the wing anti-ice heated appropriately (requiring the use of spoilers to manage airspeed). The Captain was attempting to monitor - coach the First Officer while briefing; setting up the FMS and changing all the avionics required for the approach on the different localizer and after entering a straight in visual in the FMS with the appropriate inbound course. The Captain had his finger over the execute button and was waiting to confirm the change; but we were still in Heading Mode - while trying to correct the method of speed control that the First Officer was using; the Captain unfortunately pressed the execute button on the FMS and as we were in NAV mode the aircraft started a turn toward the airport to intercept the approach course that was programmed. ATC calmly told us to make a left turn to a heading of 330 and the Captain put the aircraft in Heading Mode and started the turn as instructed; ATC requested further turn to 300 heading 'tight turn now'. We complied and were subsequently vectored onto the final approach course.The Captain had set up the appropriate ILS Z localizer and instructed the First Officer in the methods of flying this approach correctly without it being in the FMS database - which is a threat that is known to our airline and there have been safety bulletins about this and the flight crew had reviewed this as a possible threat; but on previous arrivals had not been issued the Z approach so we had not had the opportunity to prepare for it prior to this flight and on short notice.Late notice to change to an approach that is not contained in the FMS database. New First Officer being trained to manage the CRJ-200 in icing conditions and learning to manage speed on multiple altitude changes while keeping enough thrust for the anti-ice system while using flight spoilers to manage speed. All of these things happening concurrently in a very busy environment set the table for a key press by the Captain that was inappropriate and ill-timed. The Captain failed to make sure the airplane was switched to Heading Mode; and hadn't gotten to the point of confirming the change with the Pilot Flying because his attention was distracted by making sure the First Officer maintained the appropriate airspeed and inadvertently pressed execute on the FMS.A better move would have been to ask for an extended downwind or vectors to 'make time' for briefing; setting up for; and explaining the approach that we were changed to and its potential pitfalls should we not be aware of the input errors that could occur and correct them. Also; the Captain should have moved his hand away from the execute button while prompting the First Officer to correct airspeed and coaching the First Officer through how to do that; then going back to the FMS CDU and explain that we should switch to Heading Mode; then have the Pilot Flying confirm the change in the FMS and then depress the execute button. Slowing down the pace of these different tasks and doing a better job as a Captain in dividing attention and compartmentalizing these different tasks should in the future prevent such errors.




Synopsis: CRJ-200 Captain reported a track deviation occurred on arrival into DTW when they erred while manually loading an approach that was not in the database.