Mountain waves - your stories, please!

[David Johnson]

All,

The discussion on another thread about some nasty mountain wave turbulence got me thinking about this phenomenon. It would be interesting to hear some other stories from some of you about some of mother nature's roller coaster rides your RVs have survived.

Here is a shot taken from my back porch here in the bustling metropolis of Erie, CO. It shows a very well-defined cap cloud over the continental divide of the Colorado Front Range, along with a sausage style rotor cloud that stayed rolling stationary in one spot for the better part of a day as the winds howled at the surface. Classic setup for the famous chinook. Winds over the passes were perpendicular to the ridge line gusting beyond 70 knots and an airplane was flipped at BJC that afternoon.



So let's hear it...what's the worst you've encountered over the high terrain?

Dave

[rvator51]

Lenticular cloud several miles long over a long ridge coming back from Durango Co to Phoenix, AZ. Major turbulence. Ground speed wend down to 90 mph. Have to turn away from it and fly a long ways around it.

[airguy]

Refer to my thread about the "Buddy Holly" flight here - http://www.vansairforce.com/communit...ad.php?t=13475

These shots were taken the next day while snow-skiing in Purgatory (Durango, CO). We flew home that night with 40+ knots on the tail.


http://img262.imageshack.us/img262/4545/clouds16rs.png
http://img262.imageshack.us/img262/2746/clouds27ok.png
http://img212.imageshack.us/img212/584/clouds37pz.png




On the flight up for this trip, coming into ABQ from the east was rather interesting. We had about 50 knots on the nose and I was seeing a rather pronounced slow mountain wave with about a 4-minute period. At the top end I had to pull back on the throttle to keep the engine below redline, with the nose down at a rather alarming angle and airspeed edging into the yellow, and we were still climbing. On the bottom, I was at Vy and full power, and still losing 700-900 fpm. I finally called Center and advised "Unable to maintain assigned altitude", put it in a Vy climb and left it there for the duration until we crossed the pass just east of ABQ at 11,200, about 3000 AGL.

[Nuisance]

Well, once upon a time...

I departed Jeffco (BJC) IFR due to some upslope poor visability that had low ceilings. About 1500 agl (which would be 7000 msl) I broke out into a beautiful clear blue sky with fresh snow on the peaks, and headed southwest toward Pagosa Springs. As I climbed, I picked up stronger and stronger winds out of the west. Soon I was riding the waves up and down. I have a long standing policy of accepting any free lift I get in these conditions, and as the westerlys passed 50 knots (forecast was for 35) I knew I needed all I could get. As I started over the ridge SE of Kenosha pass (called the Tarryall mtns) I was at 15,000 msl. The ridge is about 12,000. I hit a real strong down part of the wave, and started down. Usually I will just maintain Va it these conditions and hope to fly through it. Also, the C-180 I was flying climbs pretty well at Va. Well, I just kept going down. As the terrain kept getting more detailed, I eventually found my self at Vy. I ended up about 500 agl (a 2500 ft loss) before I flew out of the downdraft and into the next updraft. This in a very good climbing airplane. It all happened in about a minute.

Fortunately, the rest of the trip was easy. I was toast.

John

[rv6ejguy]

A friend with an O-360 powered RV6A related the following story to me a couple years ago. I hope I have it basically correct. Crossing the Rockies at about 12,000 feet, he encountered severe descending air. He applied full power, fine pitch and established best climb speed. He was still descending at 500 fpm.

He altered heading to cross the ridge line at an angle to no avail. All the while he was in severe turbulence and was really concerned the the airplane would come apart. Even with the straps tight, he was hurled into the canopy several times, knocking his headset off and stuff was flying around the cockpit, the wings were flexing like crazy. He had nothing to hold on to with his spare hand. He could not read the instruments on the panel.

The airplane was heading towards the trees after about 10 minutes of this and he thought he would be impacting them momentarily. Luckily descending air stops at the ground and at about 200 feet ATL (above tree level), the aircraft stopped descending.

He flew home with new respect for mountain flying, humbled and scared to say the least. Inspection later showed some cracked paint on the wings but no structural damage. Strong airplane.

If you think your RV performance can get you out of anything, learn from this one.

[David Johnson]

Excellent. These stories are just the sort of thing I was hoping for. Good stuff to learn from, and I welcome more.

I've taken mountain instruction from the Colorado Pilots Association and have spent considerable time with a local "old salt" flying around up there as well. One thing I've seen over the past few years is that there are different definitions of mountain flying. To some, it's crossing the ridges at 3000 AGL. To others, it's flying the canyons and heading to backcountry strips. I'm experienced with the former but plan to head to McCall with the 182 this summer to get the latter. Precise airspeed control and advanced planning/knowledge are all vital to heading into backcountry strips.

Anyway, one of the things I've found works in a strong downdraft (and others recommend) is to actually point the nose down and fly through it, believe it or not. It's counter-intuitive, but it minimizes the amount of time you spend in the wave of descending air. Also- cross the passes at least 2000' AGL and at a 45 degree angle, and you'll have the option of turning to lowering terrain and point the nose down to fly out of it if you get caught in a severe downdraft. Many folks here probably know this stuff already, but maybe some folks don't, so it seems worth mentioning it.

Dave

Oh, one more thing. A T210 went down near Ouray, CO last year, I believe it was. It was winter and there was a strong westerly wind blowing across the San Juan Range- the most rugged and sharp in the state. As the pilot descended below the ridge line on the east side to set up for a landing, he apparently encountered severe or extreme turbulence and broke up in flight. They found the wreckage scattered across 2 miles. I've crossed the Rockies in a T210 when the winds were howling, but in the flight levels. Even there we got lots of up and down motion, but no severe or extreme turbulence. It's the eddy currents surrounding the terrain that shake the dust out of the carpets...or worse.

[Yukon]

Dave,
Choose the weather you fly in. Flight Service is pretty good at predicting severe turbulence, based on both winds aloft and pilot reports. Some days are better spent in the car!

[alpinelakespilot2000]

Originally Posted by David Johnson

Anyway, one of the things I've found works in a strong downdraft (and others recommend) is to actually point the nose down and fly through it, believe it or not. It's counter-intuitive, but it minimizes the amount of time you spend in the wave of descending air.

This is a good point that Sparky Imeson makes in his "Mountain Flying Bible and Handbook of Flight Operations." Although it is counter-intuitive, when caught in a downdraft you should not drop to Vy or Vx. You should maintain as high a forward speed as possible and try to fly out of it. (Kind of like how a swimmer gets out of a riptide--don't swim against the current, swim across it!) Of course, this assumes that your not getting knocked around by significant turbulence at the same time. If the latter is true, Va is what you'll probably have to live with.

Even if you never intend to do any mountain flying other than flying 3000 feet over the top of the mountains, at least reading a good mountain flying book should be a basic minimum requirement of flying anywhere there are mountains. If you do intend to go lower, I'd defintely second the "get some good mountain flying instruction" advice. I kind of think it is, by far, the best training you can do to make yourself a better pilot. You will really get to know the airplane and the limits of its (and your) capabilities.

[the_other_dougreeves]

Originally Posted by David Johnson

Anyway, one of the things I've found works in a strong downdraft (and others recommend) is to actually point the nose down and fly through it, believe it or not. It's counter-intuitive, but it minimizes the amount of time you spend in the wave of descending air. Also- cross the passes at least 2000' AGL and at a 45 degree angle, and you'll have the option of turning to lowering terrain and point the nose down to fly out of it if you get caught in a severe downdraft. Many folks here probably know this stuff already, but maybe some folks don't, so it seems worth mentioning it.

Yep - I've heard not to try and climb in the downdraft, to keep the speed up and get out of the sink - don't sailplane pilots use the same technique? If it works for them without an engine, it should work for us with one I've also heard to cross ridges at 1000' above it per 10 kt of wind aloft.

Only bad Mountain Wave encounter I've had was as PAX on a CO 737-800 around the Blue Mountains, I'm guessing at FL380. You could feel the airplane pitching and climbing / descending in the wave along with thrust changes, each cycle about 20 seconds in period, with the amplitude of the wave getting stronger with each one. Climb, then sink and horrendous turbulence in the trough of the wave - smacked my head onto the cabin wall more than once. Knowing it was wave and that it was going to get worse before it got better was pretty unnerving. Those guys earned their pay that day.

[CraigH@KRPH]

I'll second the recommendation for Sparky's book. I read it cover-to-cover several times before taking my first trip up to LXV. Pointing the nose down in a downdraft is counter intuitive, but it proved to be the fastest way out when I hit a nasty downdraft between Leadville and Buena Vista in a Tcraft.