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Mountain misdirectionMountain misdirection

By David Jack Kenny

There’s little dispute that the introduction of affordable GPS receivers for the civilian market produced the most dramatic improvement in navigational accuracy since the installation of the VOR network half a century earlier. Further refinements followed with the end of selective availability in 2000 and the construction of both wide- and local-area augmentation systems, making it possible to determine an aircraft’s position within a few feet. Even a legacy non-WAAS receiver achieves accuracy on the order of 10 yards or so, a degree of precision unattainable by even the sharpest practitioners of VOR or ADF navigation.

Despite that, pilots still get lost—even in GPS-equipped aircraft. Some choose to rely on the moving map and the Direct-To button instead of bothering to enter a flight plan. Terrain or airspace considerations can require routing VFR flights by way of landmarks that aren’t in the database, in which case falling back on pilotage may seem easier than deriving the latitude and longitude from the hash marks on the sectional chart. Or one might make a mistake entering the coordinates while trying to create a new waypoint.

In well-populated areas with plenty of airports, the result is most often embarrassment (though TFR or special-use airspace violations are also possible). In more rural regions, the prospect of fuel exhaustion begins to rear its ugly head. But in the higher mountains, missing your bearings by even a couple of miles risks a situation that offers no attractive options.

Shortly before noon on Aug. 9, 2014, a normally aspirated 200-horsepower Piper Arrow III took off from Steamboat Springs, Colorado, en route to Boulder Municipal. A 62-year-old CFI and a 60-year-old private pilot were on board. The flight was the last leg of a mountain flying course that had already taken them from Boulder to Eagle, out to Glenwood Springs, and back to Eagle on their way to Steamboat Springs. E-mails exchanged beforehand suggested that they planned to return by way of Milner Pass about 50 miles to the east but didn’t specify other details of their route. However, pilots familiar with the area suggested that the preferred way to begin an eastbound departure from Steamboat Springs was through Rabbits Ears Pass, where U.S. Route 40 crosses the mountains at an elevation of 9,573 feet.

The 1978-model Arrow had completed a 100-hour inspection two days earlier. Its engine had been operated almost 1,600 hours since its last major overhaul (about 80 percent of its suggested 2,000-hour time between overhauls). Cylinder compressions ranged from 71 to 78 of a nominal 80 pounds per square inch. Its instrument panel had been modernized with updates that included a digital transponder, a new audio panel, and a Garmin 530 GPS.

An alert notice was issued at 5:20 p.m. after the airplane was reported overdue. Searchers located the wreckage shortly before 10 p.m. in a mountain valley. The accident site was 12 miles southeast of the Steamboat Springs Airport. At the mouth of the valley, U.S. Route 40 makes a hairpin turn on its way to Rabbit Ears Pass two miles to the east-northeast. The elevation of the crash scene was 9,100 feet. A METAR recorded at Steamboat Springs six minutes before the accident included a temperature of 20 degrees Celsius; investigators calculated that the density altitude was 11,200 feet. The performance table in the Arrow’s pilot's operating handbook indicated that the best rate of climb attainable in a new aircraft under those conditions would have been less than 200 fpm. A guide to mountain flying published by the Colorado Pilots Association recommended against taking off unless the airplane could be expected to gain at least 200 feet per nautical mile—in this case, a minimum rate of 300 fpm.

The Arrow was found with the landing gear down and locked and the gear selector in the “down” position. Investigators concluded that after missing the turn that would have led to the pass, the pilots flew straight up the valley, ignoring the Colorado Pilots Association’s advice to enter at a 45-degree angle to facilitate escape. By the time they realized their airplane could not outclimb the slope, there wasn’t room to turn around. Presumably, they did their best to make a survivable forced landing, but failed.

Onboard electronics have proven a boon to accident investigation by recording the aircraft’s position, speed, and attitude during the last seconds of a flight. In addition to the panel-mounted Garmin 530, two iPad minis and a GoPro camera were found in the wreckage and sent to the NTSB recorder lab. The camera hadn’t recorded any images of the accident flight—and impact damage to the other three devices was so severe that no data could be recovered. The flight’s exact course, and the details of what if any use was made of the GPS, remain unknown.

Related links

GPS for VFR Operations online course

"Truth in Performance" Safety Pilot article

Mountain Crash Real Pilot Story

GPS from the Ground Up Safety Advisor

Mountain Flying online course