Date: 201809
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: IMC
Light: Night
Aircraft: Challenger CL604
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Reporter organization: Air Taxi
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Instrument; Flight Crew Commercial; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human factors: Communication Breakdown; Situational Awareness
Second reporter function: First Officer; Pilot Not Flying
Anomaly: ATC Issue All Types; Deviation - Altitude Overshoot; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Returned To Clearance; Flight Crew FLC Overrode Automation; Flight Crew Overcame Equipment Problem; Flight Crew Became Reoriented
Contributing factors: Procedure; Human Factors
Primary problem: Human Factors

Narrative: We were on the RNAV arrival; and were initially told to expect the ILS XXR with a 15 mile final. We requested an arrival on [Runway] XYL due to proximity to parking and were told that it would be unable. I had manually pre-tuned both localizer frequencies for [Runway] XXR (in active) and [Runway] XYL (in standby) in preparation for either approach.On the downwind leg; descending to an assigned 3;000 feet; Approach said they could offer us [Runway] XYL if we were able to 'expedite down to 3;600 feet.' My copilot; in an unfortunate non-standard fashion; stated that we would be able to accept an expedited descent. However; my copilot failed to read back that we were now to still descend to 3;000 ft and expedite down through 3;600 feet; as we had understood the clearance to mean. The last clearance limit we had received was descend to 3;000 feet; and the controllers request was that we 'expedite to 3;600 feet' not 'descend and maintain 3;600 feet.'We passed through 3;600 feet and at approximately 3;300 feet; the controller admonished us stating that we were supposed to maintain 3;600 feet; and to level off immediately. This took us by surprise; since our clearance limit had been 3;000 feet. We leveled off at 3;000 feet and were then given a traffic call for aircraft inbound on the ILS XXR. We started to receive vectors for [Runway] XYL; and it was becoming more clear that we were being vectored in very tight and high. I reminded my copilot to please update the approach and runway to [Runway] XYL in the FMS; as I was slowly beginning to lose situational awareness.We then received a turn to intercept to localizer on [Runway] XYL. I looked down and the box was now incorrectly set for [Runway] XYR. I quickly noted to my copilot that the incorrect runway had been set again and to change it. I had remembered that I had pre-tuned the localizer frequency into NAV1; so I switched my nav data from FMS to raw data; and picked up the localizer. We still had not yet been cleared for the approach and were high on the glideslope. I told my copilot we would need lower in order to accept the approach. Approach then immediately cleared us for the approach and told us to contact ZZZ Tower.Upon checking in with ZZZ Tower; they queried if we were confirmed lined up for Runway XYL. Being IMC; I noted that I had a centered localizer and had just caught the glideslope; and my FMS was showing Runway XYL. However; I failed to notice that when the copilot accidentally selected [Runway] XYR in the FMS; the system had autotuned to that localizer frequency; dumping out the XYL one I had previously manually pre-tuned. Once the copilot had corrected the error in the box; I had already selected raw data and it would not auto-tune to the new XYL frequency in this mode. This resulted in us displaying XYL on our nav screens with XYR localizer frequency tuned.We broke out of the clouds at 900 feet; and I immediately recognized we were lined up for [Runway] XYR and not [Runway] XYL. At this point; ZZZ Tower advised it also appeared we were lined up for the incorrect runway and issued us a go-around instruction. My copilot noted that we were in process of lining up for [Runway] XYL; and then confirmed that we were still cleared to land on [Runway] XYL. The issue appears to have started snow balling with the query by ATC about our clearance to descend to 3;000 feet. The instructions to expedite were given in a non-standard fashion; and my copilot's response was also non-standard. This led to confusion in the cockpit. The tight turn just outside the FAF; last minute runway change; and mistakes loading the approach appropriately in the FMS resulted in us lining up on the XYR localizer even though our FMS was displaying XYL. There was a breakdown in communication with Approach; and [also] between both crew members.Upon landing; ZZZ Tower requested that we call them on the landline and discuss. I spoke with personnel at ZZZ Tower; [we] reviewed the entire approach; including how we mistakenly lined up for [Runway] XYR. I told him I felt that we were given a series of quick changes and poor clearances on a very congested frequency. This led to us making a series of poor decisions and unfortunate mistakes. I could feel us slowly slipping behind the airplane; and I should have just broken off the approach entirely and requested new sequencing. Going forward; Company SOPs; including using correct radio phraseology; and confirming changes in the FMS before executing them need to be reiterated and reinforced.


Second narrative: Descending into ZZZ; were given [Runway] XXR. [We] switched to a new controller [and was] given a descent to 3;000 feet; we requested [Runway] XYL. [We] were told it was unavailable; shortly after; [we] were advised there was a hole; but we'd need to expedite through 3;600 feet. Descending through 3;300 feet; we were admonished we had missed 3;600 feet and to arrest our descent. We were given traffic to follow; and maintain 3;000 feet. When we were turned onto final; we were still at 3;000 feet at the Final Approach Fix. When we asked for lower; we were cleared for the approach. We were high; not configured or stable; and in fact had wrong LOC tuned.Through not terribly rushed; we were given a series of changes and poor clearances on a very congested frequency. We felt we were caught up; [up] to the very end; when things sort of unraveled. I was every bit as involved in this as the Pilot Flying. What I can take away is to always be diligent of the 'tone' of things on frequency and be [attentive of an overworked controller.


Synopsis: CL604 flight crew reported that mistakes loading the approach appropriately in the FMS resulted in lining up on the right localizer even though their FMS was displaying the left.