I-70 Across Continental Divide

[dmloftus]

Looking for a new route for my annual trip from Atlanta to Vegas in my non-turbo DA40. In a single, I try to stick close to interstates near higher elevations and rough terrain to have an out in emergencies. I’ve flown the I-10 southern border route through El Paso and Tuscon, the I-40 route across Amarillo and Albuquerque, and the I-80 route through northern Colorado and Provo Pass. I’m considering whether my plane has the performance to fly I-70 west of Denver and the continental divide. Seems I would need to be at least 14,500 to safely traverse over the Eisenhower Tunnel. But there are some tight twists and turns west of the tunnel due to some of the higher peaks. I’ve had this aircraft up to 15,500 but it is pretty sluggish above 14,000 and very little margin for error. Anyone care to share their experience flying the I-70 route in a non-turbo aircraft? Thanks!

[Rich]

Did it once in a stubby-wing Piper Arrow with three non-skinny men aboard. The overall flight destinations were KBJC -> KLXV -> KASE -> KBJC. The last leg routed over Vail, Vail pass, and then over a ridge just North of the tunnel eastbound. The highest altitude was about 15,000 ft. over Independence Pass into Aspen.

It was October a day behind a snowstorm, so the weather was nice and cool. Density Altitude and altimeter altitude about the same. No wind the whole flight. By the time we went over the last couple of passes we'd burned off quite a bit of fuel. Here's my suggestion:

Early in the morning, go light on fuel and load. No wind. Keep in mind it's Density Altitude that matters. It doesn't take much semi-warmth to make 15,000 ft PA to become 18K-19K ft.

BTW, not to nitpick, but I-80 doesn't go through Colorado - it's Southern Wyoming and generally at about 7,000 ft in that large flat desert area.

[dmloftus]

Thanks Rich. Correct on I-80 being Wyoming vs Colorado. Once through Provo Pass, that’s a pretty easy route.

[Rich]

Thanks Rich. Correct on I-80 being Wyoming vs Colorado. Once through Provo Pass, that’s a pretty easy route.

I've used it a lot. IFR at 11,000 ft = 4,000 ft AGL

[Rich]

BTW, for some additional context: Believe it or not, a Piper Arrow of this vintage is something like 300 lb lighter than most DA40’s

[CFIDave]

The best E-W routes to get across the Rockies in a normally-aspirated piston plane are I-80 thru Wyoming, I-40 near Albuquerque, or I-10 near El Paso. But you've already flown all 3 of these.

While I've flown the "I-70 route" over Colorado, it was in a turbocharged DA42 IFR up at 16,000/17,000 feet where I could mostly ignore the high mountainous terrain. I would not attempt I-70 across the Continental Divide in a Lycoming DA40 unless I had specialized mountain flying training, was lightly loaded, and had perfect weather with light winds.

[Rich]

Clearly Dave dealt with the reality of DA effects to some degree.

It looks like he has already been researching a wrinkle about this particular route when approaching from the East. You're not just flying up a nice straight canyon as all the "mountain flying" literature shows. If not already past 14K you're already "in among them" miles before the moment of truth. Personally I'd want to be at 14K by Georgetown.

Flying light is important to combat raw DA problems - mountainous terrain or not. I once flew my Cherokee 140 over Rocky Mountain National park at 15,000 ft. in summer. How? I was alone in the plane and down to something like 10 Gallons of fuel after flying nonstop from SE Idaho.

As we've said you want no wind. The "upwind side of the canyon" is a meaningless concept in this kind of terrain. This and various other standard stuff taught in Mountain Flying courses just doesn't always cut it.

The Berthoud Pass and Copper Mountain Weather stations should be helpful: https://www.codot.gov/programs/aeronautics/mtnawos

[Rich]

To digress a bit on the subject of I-80. If you ever drive that highway across Wyoming, there's a small innocuous sign in the middle of flat, featureless terrain. It depicts the high point as "Continental Divide - 7000 ft.".

image.jpeg (8.52 KiB) Viewed 660 times

For like 200 miles you will feel like you have hardly climbed or descended at all.

[dant]

I realize and understand the desire to follow interstates, but in terms of risk avoidance in that area I think you might be better off avoiding that mass of peaks that I-70 charges through unheeded.

Rollins pass under V8 is just north a relatively short way and doesn't have as many venturi forming peaks nearby for a 12000 foot pass. You can rejoin the interstate afterwards. Iooks like it's about 80nm that way vs 60 straight through, 20 additional miles. And there's a road through there for maybe some options.

pasted in to skyvector:
394240N1051935W 395717N1053300W 400033N1061943W 394209N1064135W

All of this assuming the winds aloft aren't absurd.

[Rich]

Yes, hedging a bit to the North makes sense. And Vail pass is less challenging. However, calling Rollins Pass a road is being kind. It's one I've driven numerous times. Parts of it are rotting trestles shouldered against the mountain slopes that may no longer be there.