Date: 201701
Local time of day: 1801-2400
Location: BOI.TRACON, ID
Flight conditions: Marginal
Aircraft: Military Transport
Operator: Military
Operating under: Part 91
Flight plan: IFR
Mission: Training
Flight phase: Initial Approach
Airspace: Class C BOI
ATC / advisory: TRACON BOI
Second aircraft: Military Transport
Reporter organization: Government
Second reporter function: Supervisor / CIC; Approach
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 CFTT / CFIT
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance
Contributing factors: Airspace Structure; Human Factors; Procedure; Weather
Primary problem: Airspace Structure

Narrative: I was receiving a skill check from my supervisor at the time of the incident. Weather was in the area and for the first part of the session traffic had been light and routine. After half way through the first part of the training session [military aircrafts] were recovering from their practice area. There were 2 flights of 2 and 2 singles. They didn't come in at once but they were about 20 seconds apart and they all came in VFR. Because there was light to moderate precipitation around the airport the flights changed their plan and requested local IFR clearances and flight split ups so they could do the TACAN Approach to Runway 28L. While the [military aircrafts] were inbound I had a DH8 on an arrival as well as a B737 and I had to departures plus I had to sequence to the North Radar with his arrivals. The incident occurred when I had [military aircrafts] on a vector to intercept final. At the time I turned [the military aircraft flight] to intercept the Minimum Vectoring Altitude (MVA) was seven thousand. However [one of the military planes] were 4 or 5 miles in trail and the turn I gave them wasn't enough to intercept the final approach course and miss the higher MVA of eight thousand. [The military aircraft] was briefly in the higher MVA and given a heading to exit it immediately. Thankfully the [military aircraft] was able to intercept final and landed without incident. This was my first time working the [military planes] in inclement weather and doing flight split ups. I am presently in training. I need to keep training in order to make adjustments and improve. The [military aircraft] had been deployed overseas for months and in that time I had been unable to train with them. They're back now and are always providing new challenges. One suggestion to alleviate this problem would be to have the military approach control perform the flight split ups prior to entering my airspace when we are landing west. There isn't a lot of space to vector 6 aircraft with rapidly rising terrain.


Second narrative: I was conducting a monthly skill check on a Controller in training with approximately 60 hours on this position. 4 flights of [military aircraft] (2 single ships and 2 flights of 2) had departed earlier for training at Mountain Home. The two flights of 2 had cancelled IFR immediately upon departure in order to stay below the clouds. At the time of the occurrence; the [the military aircrafts] were returning to BOI to land expecting Runway 28L. When the first flight was about 13 miles from the airport they advised that they would be unable to return VFR and requested a flight split and separate IFR clearances. I found out later that the trainee had not worked this type of scenario other than in simulation. As I talked him through the first one; he issued IFR clearances to both [the military aircraft] and had them both established on a 010 heading about 5 mile apart. Then he turned [the military aircraft] to a heading of 310 and cleared them for the TACAN approach. He had initially climbed [the military aircraft] to 8000 feet but had descended him back down to 7000 feet with the intention of turning him to the same 310 heading which would have had him going from a 7000 foot Minimum Vectoring Altitude(MVA) to a 6600 foot MVA. Before he turned [the military aircraft]; another flight of [the military aircrafts] checked on and explained that they wanted a flight split and IFR clearances with the wingman going first. This caused the Trainee Controller to be late turning [the military aircraft] and he was nearing an 8000 MVA. The Trainee turned [the military aircraft] to a 310 heading and I prompted him to turn him farther to a 280 heading. [The military aircraft] was about a mile into the 8000 foot MVA before he had completed his turn and then about a mile later he entered the 6600 foot MVA on the final approach course and was later cleared for the approach. No low altitude alert was activated by the computer so no altitude alert was issued.I think recognizing sooner that the volume/complexity of the traffic was overwhelming the Trainee (returning [the military aircraft] and their special requests; deteriorating weather; other arrival/departure traffic as well as coordinating the sequence with the Approach Radar North controller) and take control of the sector instead of offering guidance. Specifically; when he descended [the military aircraft] to 7000; I should have climbed him back up to 8000 in case frequency congestion prevented a timely turn onto the final approach course (as happened). I have only been his supervisor since Jan 1 and I had rarely watched him during his approach control On the Job Training even though I often work with him in the Tower and I think this contributed to my misunderstanding of his abilities at this stage of his training.


Synopsis: BOI TRACON controllers reported radar vectors were issued to an aircraft into an area below the MVA.