Sun Valley, Idaho (KSUN) is an airport that has a justified reputation for being tricky to fly into and out of. The airport, actually located in the town of Hailey, is situated in a fairly narrow valley with high mountains on three sides, making "one way in, one way out" the usual procedure. It's 6952' x 100' runway would be quite generous at sea level, but at 5300' elevation and frequently contaminated by snow or ice, it's short enough for most turbine drivers to sit up and fly straight. The airport is served by NDB-A and GPS-31 approaches, to be used by the brave and the well-equipped, respectively.
My company is one of two airlines that fly into Sun Valley. In terms of aircrew training, flight standards issues, and dealing with abnormal operations, I'd say we put more effort into that airport than any other in our system.
Notice that the GPS approach only gets you down to 1800' above airport elevation, and for Cat C airplanes like the Megawhacker, three miles of visibility is required. Although Sun Valley is blessed with many dry, clear days, all that snow has to come from somewhere - and when it does, the airport is almost unusable. Fortunately, the company usually has advanced warning, and can operate out of Twin Falls instead. When that happens, the company just busses the passengers to and from Sun Valley, 60 miles north.
A few weeks ago I was doing a trip that had me flying Boise - Sun Valley - Oakland - Sun Valley - Seattle. The first time flying into SUN, it was daylight and pretty clear out, and we got in on a visual approach without a problem. Our return was to be at night, but the TAF was calling for a pretty high scattered ceiling, so we weren't anticipating any problems. Indeed, approaching KSUN after our Oakland turn, the ATIS was reporting calm winds, 10 miles visibility, and an overcast ceiling at 5500' (above airport elevation). I was pilot flying; I told the captain I'd anticipate a visual approach but would brief the GPS approach "just in case."
Salt Lake Center had cleared us for PRESN; by the time we got there, we were still in the clouds at 9800' so they cleared us for the GPS approach. Turning inbound past WTSOX, we realized this approach was going to happen "for real," and configured the airplane accordingly. Past LIBYO, we descended via VPATH (kinda like a glideslope, but computed by the GPS). "500 to go," in and out of clouds, with heavy snowfall. "100 to go," we have ground contact but no forward visibility. "Minimums, Missed Approach." Holy crap, we weren't expecting this! It took me a moment to recall the missed approach callouts: "Condition levers max, set power, flaps one notch up...gear up...flaps up, climb power, after takeoff checklist." Just as we crossed over the airport, we broke out of the clouds and could see the airport far below us. It's too late now, though - it'd be dumb to try to save the approach even if you could do circling approaches into SUN at night (it's prohibited).
Complying with the missed approach procedure, we made the turn direct to PRESN and entered the hold there. We took stock of our fuel situation (plenty on board) and called up our dispatcher. She was aghast that we went missed approach: "It's 5500' overcast and 10 miles vis there!" We gently explained that the weather was much worse over the entrance to the valley. Not satisfied, she called Sun Valley Tower and the SUN station manager. Tower reported 3800' overcast and 9 miles vis in light snow; the station manager reported seeing us as we flew over. How could we go missed in those conditions? We replied again, somewhat more testily, that the weather often varies greatly over small distances in the mountains. "Well, can you try another approach, then?"
We had a decision to make. Second and third approaches after going missed are not something to be taken lightly; statistically, the accident rate goes up quite a bit on them. I was feeling good and alert, and have plenty of experience flying into SUN at night; I was willing to give it one more shot. The captain, however, had never flown into Sun Valley at night - in perfectly good weather, much less an approach to minimums in a snowstorm. He didn't want to do it - and even if I wasn't his subordinate, I wouldn't have pressed the issue. Messing around with multiple approaches at night in the mountains in poor weather requires everything to be done right, and if any crewmember isn't comfortable with it, neither am I.
We ended up diverting to Boise and then repositioning empty to Seattle. Not getting into Sun Valley inconvenienced a lot of passengers, and we both felt bad about that. Still, I think we made a wise decision. Could we have made it into Sun Valley? Perhaps. Would we have crashed on approach? Most probably not. Still, there was a definate increase in risk, and that sets off little alarm bells in any captain's head. The fact that captains are allowed - and expected - to make these kinds of judgement calls is as big of a factor as any in the remarkable safety record of U.S. airlines over the past several years.
The MegaWhacker at KSUN on a nicer day...