Mountain passes are important features, particularly for VFR pilots on cross-country flights.  Terrain is often a limiting feature for those of us that don’t fly in the flight levels and knowing how to navigate through mountainous areas is a key part of pre-flight planning.  The indication of a mountain pass on Sectionals is one feature to look for, especially when flying in an unfamiliar area. But how well are mountain passes denoted on the flight charts?  AOPA recently raised this issue at the Aeronautical Charting Meeting, a national group that meets twice a year to consider charting specifications, and is starting an effort to review the charting of mountain passes.  Are there passes that should be charted but aren’t?  Passes charted that shouldn’t be? And what more could we do to help pilots successfully navigate major mountain passes?

Mountain Passes Missing?

An oblique view of Atigun Pass from the southwest. Pilots turning into the pass can’t see conditions ahead and may not have room to reverse course if encountering poor visibility on the other side.

Alaska has some significant mountain ranges that pilots must navigate to get around the state.  Today, the mountain pass chart symbol is the primary clue to where the “gaps” in the terrain are located, that mark significant passes.  But not all passes are created equal.  Some are pretty benign low altitude corridors, often carved out by streams, and widened by glaciers, with no big surprises.  Others are little more than gaps between mountain peaks, with sharp turns, that may be very challenging to fly.  Perhaps the poster child of the later case is Atigun Pass, in the eastern Brooks Range, and the scene of numerous aircraft accidents over the years.  It is a narrow notch, requiring the pilot to make a pair of ninety degree turns—without being able to see what is on the other side.  Yet, only seventeen nautical miles to the west is a much more friendly pass that connects the North Fork of the Koyukuk with the Itkillik River.  Charting this location would at least let pilots know there is an alternative they should check out during their flight planning activities.  Should we add this pass to the Sectional?

While Atigun Pass is charted on the Sectional, 17 miles west is an uncharted pass, at a lower altitude with more forgiving terrain that locals normally use when transiting this section of the Brooks Range.

Mountain Passes Not Needed?

In contrast, there may be passes on the charts that were imported from USGS maps that aren’t helpful to pilots. Holmes Pass, also in the eastern Brooks Range, was named by a Robert Marshall in 1930, traveling by dog sled. Should this be on Sectional charts today

At the same time we examine at this topic, are there passes shown on the charts that may not be needed, which may lure pilots to fly through them.  Passes on flight charts are typically imported from USGS topographic maps.  Recognizing that locally any notch in the terrain can serve as a route through higher terrain, the features assigned on topographic maps may have little to do with aviation.  Again looking at the eastern Brooks Range, consider Holmes Pass, about 30 nautical miles southwest of Atigun.  According to the Dictionary of Alaska Place Names, published by USGS, it was named by Robert Marshall in 1930—a time when he was exploring the area by dog sled.  (Marshall’s book, An Arctic Village provides a fascinating account of his activities and what conditions were like at the time.)  Does this pass have value for aviation purposes today?  If not, perhaps we should remove it.

The path ahead
To address these issues, AOPA is in the process of setting up a working group, with the Alaska Airmen Association and other industry stakeholders, to examine these questions.  While the effort will initially focus on Alaska, the goal is to make a recommendation back to the FAA and Aeronautical Charting Meeting which would address these topics nationally.  While this process is just getting underway, I am seeking input on these two questions:

(1) Do you know of significant mountain passes not on Sectionals today that you think should be added?

(2) Are there mountain passes charted today that you don’t believe are used, and should be removed?

Please feel free to email me ([email protected]) with any candidates corresponding to either of these questions.

Watch for more information on this topic in the months ahead!


[This article was originally published in the January-March, 2020 edition of the Alaska Airmen Association’s Transponder]