Jim, you've gone beyond my understanding on the physics here. In moderate 1-3,000 fpm down air, in the desert, I usually experienced a strong bump about 100-200,' followed by an equally strong updraft. From a 200' patrol altitude, thermal ups and downs were much less effective. In the mountains, I stayed about 50' horizontally and whatever that left vertically on the ridge downwind of the drainage as much as practical or. When ridge lift was not available, I soldiered on keeping an energy management turn down drainage available. At 200, this, however, this was rarely necessary.

My low level experience, 98% or so, causes me to believe that several things have kept me from being driven into the ground. I think the rate of descent of air is dampened by the surface. I think the weight and inertia of large airplanes work against them in conditions smaller aircraft can survive. I think working with this and other forms of wind energy, rather than against, has made a tremendous difference.

Consider, the aircraft is descending and pulling back on the stick makes it worse. Why does pushing forward on the stick help? Could going down with descending air and later trading this increase in airspeed, this zoom reserve, for altitude in more friendly ascending air be more efficient? If I'm wrong, at least I will be flying all the way to the crash. Contact

Only about 25-30% of my flying has been in ground effect, but the vast majority of my aerodynamics work has involved the influance of ground effect and how it varies with the Biot-Savart Law. It's fun stuff.

Sparky's book (Mountain Flying Bible) says 20 knots at ridge top means be careful and 30 knots at ridge top means delay or postpone. We use 25 knots at ridge top in the C-130 I fly for a living. Those numbers have worked for me in large and small airplanes.

I think that more than 30 knots of wind at ridge top takes local familiarity, knowledge of an inversion, or enough altitude for it to not be a factor. "Enough altitude" is another can of worms but half the height of the mountain (base to peak) is a number I've heard before.

In addition to the structural considerations, I also consider weather and passenger comfort. I have a lower tolerance for bumps if IMC or with passengers.

I used to shut the engine off in the Pacer in the bookcliffs or Grand Mesa near Grand Junction on strong days in the winter. I got up to 15k several times often with the prop stopped from about 7k', and 17,999' occasionally near Grand Mesa. The tower chief was a competition glider pilot, and he used to ask how my little flying manhole cover was doing.

I could run around in the calm wave lift, sometimes having to fly in a significant crab to keep the VSI from pegging. I could only stand about 15-20 minutes at a time without the heater, then push over to start the prop with a little help from the starter motor, and then fly west out of the brunt of the updraft and head down to warmer altitudes.

I was always within ample gliding distance of an airstrip or the runway at GJT, but I never had a problem firing up the engine even stone cold.

The rotors in those conditions could shred a plane in no time. I nibbled at it on occasion inadvertently, and it was a pretty good life lesson.

I helped build a golf course in Grand Junction in the early 60s and rented a 150 there. Young and inexperienced, I hadn't figured out energy management yet. Waves are great for going east unless you have to stay down on the pipeline.

slowmover wrote:Sparky's book (Mountain Flying Bible) says 20 knots at ridge top means be careful and 30 knots at ridge top means delay or postpone. We use 25 knots at ridge top in the C-130 I fly for a living. Those numbers have worked for me in large and small airplanes.

I think that more than 30 knots of wind at ridge top takes local familiarity, knowledge of an inversion, or enough altitude for it to not be a factor. "Enough altitude" is another can of worms but half the height of the mountain (base to peak) is a number I've heard before.

In addition to the structural considerations, I also consider weather and passenger comfort. I have a lower tolerance for bumps if IMC or with passengers.

Another rookie question from the rookie, how do you estimate winds at a ridge? Ground speed vs. air speed?

With 20 ridge lift should be significant. With 30 expect the VSI to be pegged. The greater the wind speed, the greater the lift on the ridge downwind of the drainage. Just need to stay close to the ridge downwind of the drainage. Working into the wind is like tacking. We have to have some angle. Flying directly into the wind and uphill doesn't work. Now we have the VSI pegged down. Now an energy management turn down drainage is all we have.

Winds aloft forecasts, PIREPs, Skew-T diagrams, etc.

If you live in an area with snow on the mountains and you can see snow blowing off the tops of the ridges, that's another good clue.

Or if you get up close and see the wind is stronger than expected, maybe by comparing your ground speed to your true air speed, that's another great indicator! In that case you can turn around, or fly so that you have an out by always being in a position to turn away, etc.

albravo wrote:

slowmover wrote:Sparky's book (Mountain Flying Bible) says 20 knots at ridge top means be careful and 30 knots at ridge top means delay or postpone. We use 25 knots at ridge top in the C-130 I fly for a living. Those numbers have worked for me in large and small airplanes.

I think that more than 30 knots of wind at ridge top takes local familiarity, knowledge of an inversion, or enough altitude for it to not be a factor. "Enough altitude" is another can of worms but half the height of the mountain (base to peak) is a number I've heard before.

In addition to the structural considerations, I also consider weather and passenger comfort. I have a lower tolerance for bumps if IMC or with passengers.

Another rookie question from the rookie, how do you estimate winds at a ridge? Ground speed vs. air speed?

I thought that was what a GPS is for? That's how I get a handle on winds before I head over a ridge anyway, the VSI acting as a backup to give me a fuller picture of what to expect. It's funny how when working up a ridge, if it's easy and you're climbing great and all is well, you can expect the fun to lessen as you head over the backside! Starting off hang gliding like I did, sure helped me on that whole ridge lift/ going over the backside thing. It's pretty obvious what's going on when you don't have a motor to mask the aircraft's performance.

If you have a motor and you plan your downwind of valley ridge up to the pass and it works out, beyond the pass is rising air as well. The choices are managing altitude and heading or managing wind.With small engines, and sometimes large, managing wind is more efficient.

Since extensive wind management is seldom taught, favoring avoidance, a thorough reorientation is necessary. Altitude and heading maintenance thinking can be dangerous, down in the mountains, without the avoidance orientation.

One of the neater things about flying in Colorado: 13 AWOSs installed and maintained by the Colorado Division of Aeronautics, most of which are on the ridges or in the passes near the ridges (actually 12 certified by the FAA--the Dakota Hill AWOS serving the Rollins Pass area has been just recently completed but not yet certified--although it is working). From the comfort of my home, I can call the applicable AWOSs on the phone and learn what the current winds are. If I'm already in the air, most are "listenable" from about 80-85 miles away.

My personal "rule" is that if the winds according to the applicable AWOS's are exceeding 20 knots, I'll probably scrub the flight. If between the time I check them from home and when I check them again by radio, they've gone from right around 20 to 25 or so, I know I'll scrub it, because by the time I get there, they're likely to be in the "almost 30" range--no thanks!

The last time I scrubbed such a flight, a weekend when the Colorado Pilots were doing a fly-in into Marble, I had taken the Friday off to make it a 3 day weekend. But when I called the AWOSs in the morning, the winds were already at 25, so I still loaded up the airplane but postponed the flight until the next morning. The next morning, the winds had died down to only 5-10 knots at most. When I arrived at Marble, I was visiting with some who had flown in the day before, and their description of the flying conditions was exactly what I had wanted to avoid--moderate to severe turbulence, bouncing all over the sky, especially uncomfortable when anywhere near the rocks.

Cary

albravo wrote:

slowmover wrote:
Another rookie question from the rookie, how do you estimate winds at a ridge? Ground speed vs. air speed?

I use the winds aloft forecast.

Funny this thread came up again and has drifted in the direction it has. I am doing the AOPA's flight instructor recurrent training in order to get back up to speed for my CFI reinstatement check next month. The module I just finished was mountain flying by the ASI which count as an elective credit towards the FIRC. I found it lacking to say the least. 90% about density altitude and one slide (maybe two) on actual techniques of flying in the mountains. DA is important, but....we get it. Then at the end it just says "go get an instructor that is familiar with mountains". This just served to confirm that the modules are about time instead of content. I fully understand that there are entire books dedicated to the issue, but a lot more meat could have been added to the course.

Yeah, I've watched that ASI video, and it is oriented primarily to high DA issues. I guess it's the difference between high elevation operations presumably in the Mountain West, and actual flying in the mountains--and that difference can be significant. Except for my initial training in the Anchorage area, most of my flying life has been in high elevations in Wyoming and Colorado, so I'm really, really accustomed to operating in high DA circumstances.

But it's only been in the last 7+ years that my high elevation flying was actually in the mountains. My "basic mountain flying", both training and doing, had been way too basic, yet it was probably much more than the ASI video. Quite honestly, I wish I'd started learning more advanced mountain flying long, long ago--it would have added more to my enjoyment of the area in which I have lived. Just like everything else in aviation, it takes a long time to learn, and the learning goes on and on and on.

Cary

When looking at government training programs, or government sanctioned programs, we have to understand that the needs of the government come first. Just look at the name for us. Why do they want us to "be " instructors (noun) rather than to teach (verb.) Certification, official structure, paperwork, control. Once it was acceptable for us to teach people to fly and then they would evaluate our students.