A popular mountain pass through the Alaska Range connecting Anchorage and McGrath just got a “facelift.”  The flight route that has for many years been known as Ptarmigan Pass is the longer, lower, and more open pathway through the Alaska Range. It provides an alternative to Rainy Pass, which is at a higher elevation along a more confined route.  As the FAA’s Aeronautical Information Services is reviewing Alaska mountain passes, discrepancies are being corrected.  During this process, two issues were discovered regarding the route formerly associated with Ptarmigan Pass, which are resulting in significant changes to features on the McGrath Sectional, including renaming and relocating Ptarmigan to Houston Pass.

Background
Pilots flying VFR through the Alaska Range between Anchorage and McGrath for many years have used either Rainy Pass—if the weather was really good—or the longer, lower route that goes up the Happy River into Ptarmigan Valley, down Ptarmigan Creek before taking a turn to the west and following the South Fork of the Kuskoskwim River out of the mountains and on to McGrath.  This route is frequently used when clouds limit more direct pathways across the range.  The description from a 1934 Naval Air Pilot publication provides a compelling comparison of the two routes, which was probably relevant for the capabilities of the airplanes of that time– in addition to many that we fly today.

This description of the air routes between Anchorage and McGrath was published in the Naval Air Pilot, Hydrographic Office Publication No 188, published June 1, 1934. (Thanks to Marshall Severson for locating this document.)

In the interest of providing more information to pilots to improve safety, the FAA is currently looking at mountain passes in Alaska and the information presented to pilots on flight charts.  In the course of this review, two problems were discovered regarding the location that had for years been labeled as Ptarmigan Pass:

  • the U.S. Geological Survey’s recognized name for this landmark is Hellsgate Canyon, not Ptarmigan Pass and,
  • further inspection revealed that while it may be the narrowest segment of the route, it is not a pass.

Where IS the Pass?
A “pass” represents the highest point along the lowest route between two drainages.  For VFR flight planning, pilots need to know the location and elevation of that point.  Adding the altitude needed to comfortably fly the route based on their personal flight minimums, a pilot can now evaluate the weather enroute.  When flying up a valley toward a pass, a pilot encountering ceilings lower than needed to cross the pass now have a basis to make the decision to turn around—while they still have the opportunity to do so.

Changes to the McGrath Sectional as of the August 12, 2021 chart cycle. After this date, Houston Pass is added to the chart, while Hellsgate is changed to a VFR checkpoint.

Along this route through the Alaska Range, the actual pass is about 10 nautical miles northeast of Hellsgate Canyon. According to the U.S. Geological Survey’s place names dictionary, Houston Pass is the name of that location.  Houston Pass has an elevation of 2,749 feet and sits in a wide valley, providing an alternative to the higher and more confined terrain along the route that goes through Rainy Pass, which sits at an elevation of 3,524 feet.  As of the charting cycle starting on August 12, changes to the McGrath Sectional include adding Houston Pass  and converting Hellsgate Canyon from a pass symbol to a VFR checkpoint.

A comparison of the elevations of three features along the Rainy and Huston Pass routes.

Looking ahead
As part of the FAA review of Alaskan mountain passes, it was noted that the pass elevation data normally found on sectionals in other parts of the country is missing for Alaska.  The FAA charting team has already added elevation data to a few passes and is working to add it to a large number of other passes across the state later this fall. For now, with regard to these passes, please make it a point to:

  • Update your databases or buy a new paper chart with the August 12 revisions
  • Note these changes and use the new placenames when making CTAF calls along the route, allowing other pilots to know your location relative to these features, reducing the likelihood of mid-air collisions
  • Help pass the word–as this represents a significant change along a route that has been used since the earliest days of flying in Alaska

When we’re talking about Houston Pass or Hellsgate Canyon, let’s help keep everyone on the same page – especially when that page is a sectional chart.  Fly safe!