Butte Montana VOR-A
Butte, Montana, and its Bert Mooney Airport (BTM) are nestled snuggly between the Yellowstone and Glacier national parks in the southwestern portion of the state, where copper mining was once the primary economic driver. The Butte VOR-A approach to Mooney Airport seems pretty straightforward, but remember, of course, that any approach without a runway number indicates the final approach course does not technically meet the definition of a straight-in. The VOR-A’s R098 final approach course is pretty close, and should, under no-wind conditions, offer a glimpse of Runway 12 out the left front cockpit window if the weather permits.
Bert Mooney Airport’s field elevation is 5,551 feet, with terrain rising another 3,000 feet just east, adding a few challenges during the approach. The right turn during the missed approach demands pilots keep a close eye on their climb rate since just west of BTM the terrain is already 1,000 feet higher. Additional nearby obstacles are why the minimums for all categories of aircraft are 7,120 feet msl.
1. A FINAL APPROACH FIX TURN
While inbound on R307, flying 127 degrees to the Coppertown VOR (CPN), the pilot must be ready to “turn, time and twist,” in IFR-training language, at the FAF when the course changes to tracking the R098 outbound to the airport. Failure to fly the new course will head aircraft toward nearby terrain.
2. FLYING TO FINAL
While it’s common to use the DME arc to position the aircraft on the final approach when not receiving radar vectors, the pilot could also proceed to the VOR and head outbound for a procedure turn before rejoining the inbound radial. In an IFR GPS-equipped aircraft, flying directly to the CPN VOR, NUNZU or DMKEX might be possible as long as the pilot observes the area’s minimum safe altitudes until joining an established segment.
3. CIRCLE-TO-LANDONLY MINIMUMS
Although the R098 provides nearly a straightin to Runway 12, this approach offers only circle-to-land minimums, which opens the option of landing on the 5,100-foot Runway 12/30 or the 9,000-foot Runway 15/33.
4. CIRCLING LIMITATIONS
Circling northeast of Runway 15/33 is not authorized, a restriction that might at first seem counterintuitive considering the “brown” high-terrain depictions on the plate just west of the runway. In fact, the terrain north and east is even higher, nearly 3,000 feet in some places.
While time inbound from the final approach fix can be used to identify the missed approach point, DME will also identify the 10 DME point. But the DME is required for more than simply identifying the missed approach point. DME is also required for an aircraft entering this approach area from the en route environment.
6. MULTIPLE STEP-DOWNS
This procedure offers multiple step-down points. Approaching from the west of CPN demands the aircraft remain above 12,000 feet as indicated in the MSA chart, while from the northeast, aircraft must remain at least 10,100 feet. From there, a descent to 9,000 feet while on the arc is required until established inbound within 10 miles of the VOR, where a descent to 8,200 feet is authorized. Crossing the VOR inbound, the aircraft may descend to 7,120 feet.
7. WATCH MISSED APPROACH POINT
The missed approach point at MACXA coincides with the 10 DME but leaves the aircraft short of the airport. That’s because the pilot must see the airport early enough to land or, if not, have sufficient distance to make the turn on the missed approach procedure while remaining clear of terrain. This requirement is highlighted by the greater than normal approach visibility minimums ranging from 1¼ to 3 miles depending on the aircraft category.