Date: 201506
Local time of day: 1201-1800
Location: BFI.Airport, WA
Flight conditions: VMC
Light: Daylight
Aircraft: Challenger 605
Operator: Corporate
Flight plan: IFR
Flight phase: Landing
Airspace: Class D BFI
ATC / advisory: Tower BFI
Second aircraft: Skyhawk 172/Cutlass 172
Reporter organization: Corporate
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Confusion; Situational Awareness
Anomaly: ATC Issue All Types; Conflict Airborne Conflict
Detector: Automation Aircraft RA; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action; Flight Crew Executed Go Around / Missed Approach
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: During our approach to Runway 31L into BFI we received a TCAS RA; initially to; 'level off' and then 'climb'. We subsequently complied with the RA and then executed a missed approach.Approaching the airport from the south and west we were left on a fairly high left base to final in good visual conditions. While the approach was higher than normal we were stabilized well above 1;000 feet and use of speed brakes was not required. After confirming that we had the airport in sight with SEA Tracon; they subsequently cleared us for a visual approach to Runway 31L. We were given instructions to contact BFI tower. During the transition from approach to tower both the PM and myself noticed traffic ahead and to our left. I'm pretty sure the aircraft was slightly above us or at our same altitude when I initially noticed him. After checking in with BFI tower we were given a traffic point out and told that this aircraft; whose position was at our same altitude and west of us; was going to be landing on Runway 31R. At this point I started wondering how this was going to work out. Around the same time I started to doubt the success of this approach we received a RA to; 'level off.' We were just inside the outer marker descending on the glide path. After responding to the RA; first a level off command then a climb command; we executed a missed approach. I started to climb out expecting more instruction from the tower on our missed approach instructions. At this point the BFI tower controller told us to execute the; 'published missed approach procedure;' this was strange because we were cleared for a visual approach. Thinking the controller wanted us to execute the published missed approach off of Runway 31L ILS; this is how I proceeded. Somewhere around 3;000 feet the tower said he wanted us on the published missed approach procedure; 2;100 feet. To my knowledge there is no published missed approach altitude or procedure for the visual approach to Runway 31L in BFI. The only 2;100 restriction I know of is the departure procedure off of 31L; NEEDLE NINE.I don't think there is any reason to revisit our frustration with the TCAS issues in BFI. That said the Tower Controller in this situation seemed to have little to no situational awareness. Trying to cross traffic from left-to-right and underneath our path while descending on the glide path? The controller should have had us or the C-172 complete a 270 degree turn to rejoin the final. The final area of frustration concerning this approach; the expectation that we complete a published missed approach procedure that doesn't exist. If the controller wanted us at a specific altitude he should have just cleared us to the altitude; i.e. climb to 2;100 feet




Synopsis: CL605 Captain on a visual approach to Runway 31L at BFI is informed of C172 traffic on a left base for Runway 31R. A TCAS RA is received and the reporter initiates a go around. The Tower instructs to fly the published missed approach but actually intended that the flight fly runway heading and climb to 2;100 feet.