Date: 201503
Local time of day: 0601-1200
Location: OPF.Airport, FL
Light: Daylight
Aircraft: Gulfstream II (G1159)
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class E MIA
ATC / advisory: TRACON MIA
Reporter organization: Air Taxi
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Other / Unknown
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Conflict NMAC
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action; Flight Crew Became Reoriented
Contributing factors: Airspace Structure; Human Factors
Primary problem: Ambiguous

Narrative: I was the Captain and PF [Pilot Flying] for this leg and while on radar vectors to OPF and descending into the terminal area there was a lot of IFR and VFR traffic; the autopilot was engaged and ATC gives us a descent to 2;000 FT from 3000 FT and heading 250; Subsequently ATC issued a right turn to HDG 280 my copilot in a very concerned manner asked me to stop descending and stop turning because there was traffic a small airplane to our right wing. I complied by disconnecting the autopilot and manually arresting the descent by now copilot asked me to climb and turn in opposite direction to the left because traffic was near the Wing tip. I complied and mentioned that I cannot see the traffic and there was no indication of traffic in our TCAS. He questioned the ATC controller and the controller said that he did not know that traffic was near us. Copilot indicated in a very strong voice that we just had a NMAC by about 300 ft. Controller indicated that traffic was not near us and issue a turn to the west. Copilot indicated that a turn to the west will put us in a collision path with that traffic again. I reiterated again that I was not able to see any traffic as it was near the right wing tip. ATC issue a descent to 1500 and another turn and we landed uneventfully. On the ground I asked the cabin host as she indicated that passengers saw the small airplane near the right wingtip. Passengers were safe and not alarmed as they saw the airplane momentarily. I asked the copilot to write a report with the facts because I never saw the traffic; the TCAS system never alerted of the presence of traffic in the vicinity; or a near miss; we never received a TCAS RA and ATC never issued a near miss or a loss of separation advisory. It is believed that the small airplane involved in the alleged near miss did not have the transponder on or it was not operational. I mentioned to my copilot that I feel our CRM and his clear instructions helped to prevent this situation from escalating into an incident or accident.


Second narrative: After being vectored by approach controllers while on the FISEL6 STAR we experienced a near mid-air collision. About 4 miles before reaching the waypoint AGOYA we were instructed to turn left to a heading of 190 and descend and maintain 3000 feet. After reaching 3000 feet and a heading of 190 ATC pointed out VFR traffic at 2 o'clock and 3 miles I made visual contact with the VFR traffic and ATC then informed us to turn right to a heading of 280. I told the controller that heading would put us on a collision course with VFR traffic; he then stated for us to turn right to 290 and descend and maintain 2000 feet. We accepted the clearance; at that time after the VFR traffic was no longer a factor. After completing the turn to 290 and descending through 2300 feet I told the PF [Pilot Flying] to stop his descent ASAP as we were descending into other traffic; the traffic was not showing on our TCAS. My best guess is that we missed the traffic by 300 feet laterally and 200 vertically. The aircraft was a white Cessna 172 with a green stripe; the pilot was a white male wearing gold rimmed Ray Ban sunglasses and a blue baseball hat with a white bill. I then voiced my concern to approach that we had VFR traffic that didn't show on our TCAS and we missed by 300 ft. He responded that he had just then just picked up the traffic as a primary only target. He then told us to turn to a heading of 090. I then voiced my concern that ATC was once again turning us back to the VFR traffic that wasn't using mode C but we were able to comply with the clearance as the PF had the traffic in sight and was able to maintain a visual. Once we completed the turn to the east we were cleared for a visual approach to RWY 09L at OPF and we landed with no other incident.


Synopsis: GII flight crew experiences a NMAC with a C172 at 2300 feet while being vectored by MIA Approach Control. The C172 did not have a transponder or it was turned off; as the aircraft was invisible to ATC and the GII TCAS.