Sunday, October 5, 2008

VFR Paths over the Rockies

You need to be careful flying through the Colorado Rocky Mountains in a small non-turbocharged plane, but it can still be done safely. There are many paths over the Rockies. What path to use depends on each particular situation: clouds, winds, weather, and intended direction. Also what you are comfortable with and your experience. In general, I do not pick straight lines, but instead follow the main valleys and minimize my time flying over the highest mountains. Through my trips west, I have used quite a few paths. Each one is quite beautiful.

Here are the main paths I have taken crossing the divide going from the furthest north to the furthest south. All these routes are not exact, but approximate. The flight path tool I could find could not show the route more exactly.

One interesting item to note is that the section from Grand Junction along the Colorado River to Vail and to Kremmling is very well covered by radar almost to the ground. This makes flight following possible and a good idea. All the other routes (through Gunnison and Alamosa) are not covered well by radar at lower altitudes.

North route into Southern Wyoming and west
Usually only needed if heading somewhere further north. This is the lowest terrain on the North side of the Colorado Rockies.

Over Colorado/Wyoming border, to Kremmling, and along the Colorado River
A nice low spot exists near the CO/WY border. Below is the route, but I would not go all the way to Laramie. This is the closest I could indicate on this flight planning tool.

I hear going over Cameron Pass or the FROGS intersection can be good. I have not had the situation yet where I used it for long trips, but I have gone over it for fun though.

Over Rocky Mountain National Park and along the Colorado River
Going over Rocky Mountain National Park is often less bumpy than over Corona pass.

Over Rollins Pass (Corona Pass) and along Colorado River

Southern Middle Route through Salida then Gunnison
A nice middle route if the norther routes will not work. There are 2 ways to get to Salida:
klmo-larks-kank- through Wilkerson Pass and Salida
klmo-pub-kank- through Pueblo then Salida
Then through Marshall pass (better than Monarch pass since Monarch is a sequence of ridges with downdrafts instead of just one)
- CO11-hbu-kmtj

Southern route through Alamosa and Durango
Another route further south if the main mountain section is bad for weather. There are three ways to get to Alamosa:
klmo-larks-kank-als- through Wilkerson Pass and Salida then Alamosa
klmo-pub-kank-als- through Pueblo then Salida then Alamosa
klmo-pub-gosip-als- through La Veta Pass then Alamosa (La Veta Pass can have some pretty big turbulence for being a low pass)
Then through Durango
- brazo-dro

Very Southern route near Albuquerque
On the way back to Longmont in the past, I have had to wait in Albuquerque for a snow to clear in the Denver area. Then I proceeded the rest of the way when the snow cleared. This is the lowest terrain route on the southern side of the Colorado Rockies.
Another route for the north/south portion that has had less turbulence for me is on the windward side of the Sangre De Cristo mounains.

Combined Picture of Routes

Using the above flyagogo links, then clicking on the little Google earth button on the left side of the web page for each link, I built a Google Earth image with all the routes. (Save the file and load it into Google Earth). If you want you can add the sectionals by clicking on this link to Google Earth Sectional Chart information. If you are zoomed out, I think the sectionals do not look good. But zoomed in, the sectional information is nice. I found these addons for NexRad Information for Google Earth, West Cloud Satellite information for Google Earth, and Eastern Cloud Satellite information for Google Earth.

Some Quick General Thoughts

Take a mountain flying course. Many instructors in Denver area are available for this type of instruction.

Landing in the moutains is different; here are some of the factors:

  • Density altitude is a major factor.
  • Your ground speed will be higher since you are flying the same indicated approach airspeed at a higher altitude.
  • Short field methods are important even on longer strips.
  • Your horizon and determining what is straight and level is sometimes confusing since the sky horizon is much higher than the real horizon.
  • Your approach and pattern is often restricted by high moutains.
  • Many other items that you would cover in a mountain lesson.

Colorado Department of Transportation has a nice book and on-line information for all the different Colorado airports.

Approach ridges at 45 degrees to reduce the amount needed to turn around if needed. Watch out for downdrafts and turbulence. Don't fly over the ridges if the winds aloft are expected to be above 30 knots at 12,000 MSL. Always have an out if something goes wrong. And IFR over the rocky moutains is a bad idea in small planes; don't try.

There are many AWOS stations near passes. Use this information where you can. It can give you an idea of how the winds are doing in different places.

Here are some books to read available at Marv Golden. Sparky Imeson has a good website with lots of mountain flying information.

Once again take instruction if at all possible.



CPS said...

Thank you for this well thought out information! It was exactly what I was looking for.

Brian said...

There is one more thing to mention that I see I did not include. Another resource is the Colorado Aeronautical Chart. You can pick it up at many airports in colorado and I think you can order it from this web page. I see they are out of the airport directories, but maybe they have the charts. It nicely combines the Cheyenne and Denver Sectional, shrinks it similar to a WAC chart, covers only Colorado, and shows some routes over the passes. A nice thing to have!


Brian said...

I added a blog entry with some of my thoughts and things I have learned in my lessons about flying in the Rocky Mountains.


Gimble said...

I appreciate the work, have referred to this page on numerous times. One gripe: my current version of Google Earth won't load -- could you give more specific directions?

Brian said...

Sure. In order to use vfr_routes.kml, save that file to your desktop. I think this is the key part you may have not done; it does not automatically run in Google Earth. Then start Google Earth (I am using version 5.1.3535.3218), then do File->Open-> select vfr_routes.kml that you stored on your desktop. Hopefully this will work for you.


Nelson said...

This blog post is a fantastic resource, thank you.

You can view the proposed routes in Google Maps in your browser. Unfortunately there's no sectionals; the FlightPrep patent threats have shut down most of the options for drawing routes on sectionals (including FlyAGoGo).

Awhile back I made a map of all terrain over 8000' as a way to understand the challenge of crossing the mountains. There's notes and a small image on my blog.

Brian said...

Maybe I need to update my flyagogo links, but I have them in a lot of posts. It is bummer that the FlightPrep patent thing happened. You can still use The other option is google earth with the following link:

Michael Holroyd said...

You should try for your routes. What are the minimum altitude for each route? What do you do about oxygen over 12.5k?