Date: 202008
Local time of day: 1801-2400
Location: COS.Tower, CO
Flight conditions: VMC
Weather elements / visibility: Microburst
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class C COS
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Second reporter function: Pilot Flying; Captain
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Executed Go Around / Missed Approach; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Took Evasive Action
Contributing factors: Airport; Airspace Structure; Procedure; Weather
Primary problem: Procedure

Narrative: Crew deviated from ATC instructions in interest of safety of flight. Weather was VMC: hazy twilight with some virga above 4000 ft. AFL (Above Field Elevation) in the vicinity but not in the approach sector. Aircraft was on a dog leg to final when switched to Tower for visual approach to COS RWY 35R. Tower immediately advised of a microburst alert. Crew requested a turn to the right; eastward; away from terrain; to break off the approach and avoid the microburst hazard. Tower instructed crew to maintain present heading; which was a northwest heading toward rapidly rising terrain. Crew replied 'unable.' Tower assigned a heading of 350; approximately runway heading and toward the microburst area. Crew responded that it was not going to fly into the microburst. Tower advised of traffic to the northeast at 9000 ft. Crew roger'd the traffic and swept TCAS for targets. With no TCAS targets in the immediate vicinity; PIC exercised safety of flight authority and executed a turn toward the east; open terrain away from the microburst area. Tower issued a climb to 8000 ft. to which the crew complied with.ATC; Tower; prioritized its own concerns; traffic separation; above the physical requirements of continued flight: microburst and terrain avoidance.Controllers must have sufficient aviation understanding to prioritize threats and the latitude to compromise procedures in the obvious conflict of priorities. For example; if the choice is between losing separation between two aircraft or losing separation between an aircraft and a mountain; sacrifice separation between aircraft. Similarly; if the choice is between an aircraft flying too close to another and that aircraft not flying at all because of a deadly meteorological hazard; sacrifice IFR separation between aircraft.


Second narrative: On a visual approach; 3 mile left base; Tower declared a microburst alert for 17L. We did a soft go around; requesting vectors for visual 35R; they turned airport around for winds. Turning final for 35R; they announced another microburst for 35R. In neither case was any convective weather observed or any aircraft radar indications. Did another soft go around and asked for turn away from airport. ATC instead asked for a turn into airport and towards microburst area; [we] could see virga in that area. Informed ATC we were turning away from the indicated area. They said we had traffic. We informed them we would not be flying into the potential microburst; and no traffic on TCAS; and turned east. Shortly later; ATC put us on an appropriate vector and altitude in that direction. Found a holding pattern; and after things settled down was vectored for ILS 35R. After clearing us approach; ATC informed us the ILS was inoperative; we think they forgot to turn it around from south flow; and they tried to give us a frequency and clear us to 35L. I thought better of it and accepted a pure visual to 35R and landed without incident.ATC later mentioned they had wind equipment malfunctioning. Several aircraft diverted. We had plenty of ferry fuel. In my opinion they lost control of their pattern. We took appropriate actions and used emergency authority to prevent being put in a microburst. Did not bite on last second runway change. Previous training in 'soft' go-arounds very useful as we did it twice.


Synopsis: Air Carrier flight crew reported deviating from ATC instructions due to safety of flight.