Terrain Tactics: Going to Jackson

November 1, 2004

Bruce Landsberg, executive director of the AOPA Air Safety Foundation, has flown light aircraft in mountainous terrain many times.

The Grand Tetons are spectacular as mountain ranges go. Jackson Hole Airport in Jackson, Wyoming, is a great place to visit in a light aircraft to see the unparalleled vistas, towering parapets, and the sheer grandness of the firmament. It is also where too many general aviation pilots meet their maker prematurely. There is quite enough metal in the surrounding mountains without adding copious quantities of aluminum.

Controlled flight into terrain (CFIT) has traditionally been a big problem for the airlines and a lesser one for general aviation. It was enough of a concern that it became part of former FAA Administrator Jane Garvey's Safer Skies program. The objective of that program was to significantly impact (sorry) the aviation accident rate. The FAA remains interested in this area as does the AOPA Air Safety Foundation. In this article you will see one aspect of CFIT — the part where a normally functioning aircraft flies into the ground, usually because the pilot was unaware of his location relative to the terrain. In a place such as Jackson Hole, this is not a good idea because the terrain is pretty aggressive.

Take a look at a chart and you'll see why Jackson is called a hole. Despite an airport elevation of 6,451 feet msl, the Tetons slam skyward just a few miles west of the airport to more than 13,500 feet. There are high mountains all around — but the western range is one that gets top billing. Having flown there several times in light aircraft I can honestly say, "Go, enjoy, and be mindful of terrain and weather." The terrain doesn't change but the weather certainly does. Several accidents that occurred in or near Jackson Hole provide some good case studies for decision making.

A private pilot with no instrument rating decided to fly his Cessna 150 from Santa Monica, California, to visit his sister in Billings, Montana, for Christmas. The 150 is not really known for its high-altitude capability or for extensive range. Many would agree that such an ambitious trip in winter might border on risky. At Ogden, Utah, the pilot received a VFR-not-recommended warning (VNR) into Jackson but launched anyway without a flight plan. In that kind of terrain, search-and-rescue insurance is worth at least the time it takes to file and activate a flight plan. The pilot successfully negotiated the weather, landed at Jackson, and the FBO personnel attempted to dissuade him from leaving. They described the weather as "horrible" with snow and ice. Our intrepid aviator launched, with no weather briefing this time, probably anticipating another VNR warning. Upon encountering low visibility he decided that maybe this flight wasn't such a good idea after all. Snow and ice brought the 150 down to treetop level where, not surprisingly, it encountered a tree. The pilot survived the ensuing impact with minor injuries. That is an unusual outcome for weather accidents. Generally, they tend to be fatal between 80 and 90 percent of the time.

An instrument-rated private pilot with more than 800 hours total time and more than 600 hours in his Beechcraft V35 Bonanza planned a flight from Minneapolis to Jackson Hole in mid-January. The weather was typical for the mountains in January: From noon until midnight, Jackson Hole was forecasting scattered to occasional broken clouds above 2,000 feet with occasional periods of five-mile visibility and light snow showers. After midnight, the weather was expected to deteriorate. There were no major weather systems along the route of flight. Turbulence was reported, and isolated moderate rime icing was forecast in the clouds below 7,000 feet. The Jackson Hole ILS glideslope was notamed out of service; however, at the time of the accident, the glideslope and all facilities were operational.

The flight departed Minneapolis at 1 p.m. Central time and refueled in Rapid City, South Dakota. A weather update revealed occasional moderate to severe turbulence below 20,000 feet and for occasional moderate to severe icing between 6,000 and 22,000 feet. In the Jackson Hole area possibilities of mountain obscuration and IFR conditions added to the hazards. Visibility was expected to decrease to a mile and a half in light snow. This is not the recipe for success in an aircraft without substantial deicing equipment. The pilot filed IFR and departed Rapid City at 3:39 p.m. Mountain time. At 4:34 p.m. the pilot contacted Casper Flight Service, where the specialist reported Jackson Hole showed scattered layers and visibility at 10 miles. There were no pilot reports for icing conditions.

In-flight altitudes ranged from 11,000 to 14,000 feet and at 6:10 p.m. the flight was cleared for an ILS approach into Jackson Hole. The Bonanza crashed seven miles north of the airport and slightly off the localizer. No oxygen system was installed and ATC transcripts indicate that the flight had been above 12,500 feet for approximately one hour and 10 minutes. The regulations require pilots to use oxygen when above 12,500 for more than 30 minutes. So in addition to the weather there was the very real possibility that hypoxia further degraded the pilot's decision-making capability. Check that.

A turbocharged Beechcraft B36TC Bonanza flew from Aspen, Colorado, to Jackson in early December. The pilot contacted flight watch, while VFR, for weather information. This forecast was a teaser because the current weather was clear below 12,000 with unrestricted visibility but with forecast icing conditions and variable low ceilings at the destination (200 feet and one mile visibility) with mountain obscuration. Subsequent reports showed weather deterioration, and the low ceilings did materialize.

En route radar indicated the B36TC was consistently to the right of the airway centerline by a few miles and, when ATC advised the pilot, he responded that the VOR was "kind of in and out." This is not the area to have any kind of navigation system degradation. The pilot's last transmission before being cleared for the approach was that the flight was picking up moderate rime ice. During the arrival on what was then the VOR/DME 36 approach (recent renaming of the runways at Jackson Hole now makes this the VOR/DME 1 approach), at the 16-mile DME arc, the flight did not make a required turn to the west onto the arc, but continued to parallel the airway. Shortly afterward, radar contact was lost. The Bonanza impacted terrain near the top of a 10,741-foot peak, located approximately 11 miles southeast of the airport. Minimum altitude for the approach was 12,700 feet on the arc. The pilot had about 1,000 hours total flight time, more than 200 in the Bonanza, recent simulator training, and he had been making monthly trips into Jackson for about a year. If there is ever a place not to be complacent, Jackson is it!

Another cross-country flight was receiving VFR flight following. The controller provided the pilot with the latest weather observation (at 11:15 a.m. local time): a few clouds at 2,100 feet agl, scattered at 3,000 feet, broken clouds at 3,400 feet, and visibility of seven miles. At 11:29, the pilot advised the controller that he was going to descend from 12,500 to 10,500 feet. When asked if he was familiar with the high terrain in the area the pilot said that he was not. At this point it would have been a good time to stop and think about the risk entailed in descending VFR through a broken cloud deck into unknown high terrain. The controller advised that the IFR minimum altitudes (MIAs) in the area ranged from 10,000 to 14,000 feet msl.

Radar data showed this Bonanza 40 nautical miles southeast of Jackson Hole at 11,500 feet turning left toward the south. A satellite image showed a band of clouds near the location where the airplane turned toward the south, with tops estimated to be about 12,000 feet. At 11:39, radar data showed the flight level at 10,800 feet (2,800 feet agl). The last radar contact was at 11:41 and showed the airplane at an altitude of 10,800 feet, approximately 48 nm southeast of Jackson. After radar contact was lost, the airplane reversed course and headed northwest toward the airport. The airplane impacted mountainous terrain approximately 16 miles southeast of Jackson at approximately 10,400 feet. Based on satellite cloud analysis the NTSB determined that the airplane entered clouds shortly before impact. The noninstrument-rated private pilot had a total of 13 hours instrument flight time.

It's not always light aircraft that get snared by the big hills. The Air Force lost a Lockheed C-130 presidential cargo aircraft on departure out of Jackson Hole in the summer of 1996 in support of then-President Clinton's birthday party. The C-130 departed to the south and made a sweeping left turn into a nearby peak with no survivors. The mountains make no distinction for aircraft size or pilot experience.

You might surmise that the terrain around Jackson Hole is a Bonanza magnet with the odd Cessna 150 or C-130 thrown in for good measure. There are a few common points for consideration. Everybody, except those in the C-130, was on a cross-country flight in the winter months, which demands complete flexibility in scheduling when flying light aircraft in and around high terrain. The weather was a factor in every case and was predicted accurately as being marginal to impossible for the proposed GA operation. The VFR pilots were clearly beyond their depth. The IFR pilots did not appreciate the terrain, the weather conditions, or both. In any case, the limitations of the pilot or the aircraft always dictate a conservative approach around Jackson Hole.

For more information on mountain flying, see " Answers for Pilots: The Air Up There," page 30, " Hard Knocks," page 97, and " On Display: Steering Clear," page 147.


A free, four-step method to help VFR pilots avoid collisions with terrain at night or when visibility suddenly lowers is now available. ASF's simple Terrain Avoidance Plan (TAP) show pilots how to use published altitudes on charts to determine a safe altitude. To see the TAP, visit the Web site and click on Terrain Avoidance Plan.