A while back I was flying back from Twin Falls to Salt lake direct. It was an afternoon flight and I was excited to have a little tailwind behind me.
As I came up to the Raft River Mountains I noticed the VSI shot up to 1500fpm!! At over 11,000 ft my cherokee 180 was climbing like a maule @ SL and it lasted for about a minute and was gone. Back to level flight.

My instructor had given me some short lessons on mountain waves a few years earlier and I seemed to recall the opposite would happen soon so the voice inside said keep my altitude even though I had left my " appropriate VFR altitude".

Sure enough, minutes later the VSI changed to a dive of 1500 fpm. and full power and a tug on the yoke had no effect. The strange thing was, I hadn't really reached the other side of the mountain, which had largely a flat top with a few peaks in the high 9's. I was about 2/3rds across the top of it. I didn't panic because I had a good margin at this time, but my thoughts took me back to the last trip to Twin when I flew northwest bound low over the Raft Rivers to check out the awesome snowmobile possibilities (deep snow and high meadows and no one in sight). I may have been screwed.

Eventually, I flew out of the wave but I had lost almost 2,000ft under full power. It made me feel like a lesson was taught and I passed but I recall the previous time I could have bonked.

We also had a Citabria crash this last September in Utah County. The pilot and wife survived but said they were out looking at the pretty leaves in the canyon and their planed just sunk into the trees with no warning.

http://www.ntsb.gov/ntsb/brief.asp?ev_i ... 7544&key=1

I was wondering if any of you in the group have some sage advice on detecting and dealing with mountain waves ( or whatever the correct term is) that may save some bacon someday. I don't recall reading much on this subject even though I try to read all the rags around the airport.

Thanks for your input in advance-

This will get you started

http://www.pilotfriend.com/safe/safety/ ... n_wave.htm

Typical with wave you will have a primary, secondary and sometimes a third range. In soaring most glider pilots are taught to slow down in lift (take advantage of it) and speed up in sink (get through it faster than normal loose less alt). If approaching a mountain ridge and you encounter the sink expect to next find a bit of turbulence (rotor) then lift. If the lift is real smooth like sitting on your couch at home,you're in the wave. If you want to explore this wave turn parallel to the ridge and stay in the strongest part of the lift if you can. As a 1000 hr. glider pilot I've had many wave flights seeing altitudes as high as 27,000' at Minden and 25,000' at California City. It's a very powerful phenomenon, but can be used to your advantage and sometimes not.

Glidergeek wrote:Typical with wave you will have a primary, secondary and sometimes a third range. In soaring most glider pilots are taught to slow down in lift (take advantage of it) and speed up in sink (get through it faster than normal loose less alt). If approaching a mountain ridge and you encounter the sink expect to next find a bit of turbulence (rotor) then lift. If the lift is real smooth like sitting on your couch at home,you're in the wave. If you want to explore this wave turn parallel to the ridge and stay in the strongest part of the lift if you can. As a 1000 hr. glider pilot I've had many wave flights seeing altitudes as high as 27,000' at Minden and 25,000' at California City. It's a very powerful phenomenon, but can be used to your advantage and sometimes not.

Hi GliderGeek,

Guess I'm one too. Besides the Husky, I have a Schleicher ASH26E based at Minden. Agree with all your comments re wave.

However, sometimes mountain wave can extend for hundreds of miles downwind from the initial mountain that caused them. In sat images, when there's enough moisture to condense as the top of each "up wave", lenticular clouds form. These will be stationary and show as multiple bands of clouds downwind and parallel to the mountain range. Often too, there will be rotor clouds and/or rotor cumulas under the "lennies". Worst case, these areas can be so violent they can do bad things to plane or glider that venture there.

So, if speeding up to get through sink (recommended) be ready to slow up to design manuevering speed at the first indication of turbulence. Mommy Nature can dish out far more than any pilot or aircraft can handle. So it's best to avoid flying in mountainous regions when the winds at ridge top exceed ones level of experience. In a stable atmosphere, expect wave when winds at ridge top exceed 25 - 30 knots or so. When it gets up around 50 -70 knots it gets interesting!

If the atmosphere is dry, there will be no lenticular cloud "markers" - - but the rotor tubulence will still be there!

bumper
zz
Minden, NV

SixTwoLeemer wrote:I was wondering if any of you in the group have some sage advice on detecting and dealing with mountain waves ( or whatever the correct term is) that may save some bacon someday.

First rule of thumb: Expect wave conditions when the atmosphere is fairly stable and ridgetop winds exceed about 15 kts.

Second rule: strongest wave conditions usually are downwind of a range perpendicular to the wind with a sharper drop-off on the downwind side. (could even be a plateau with many miles of flat terrain on top)

When you encounter smooth lift downwind of a range, expect sink next! Depending on your altitude above terrain, consider stopping to utilize the updraft. Slow down to Vy, make a 180 if neccessary, and climb several thousand feet before continuing, you'll lose it soon enough! Figure 8-ing may be required to stay in the zone of lift. I once blew my motorcyle buddy's mind by taking him and his 170 into the Pikes Peak Wave, pulling the engine to idle at 13,000 feet and climbing to 20,000 in ten minutes!

Collision with terrain is much more likely going upwind than downwind because groundspeed is low and you are in the zone of sink for much longer. Choose your altitude accordingly....four to five thousand feet above terrain is not too much!

The real danger contacting an unsuspected wave while going downwind is entering the (often invisible) rotor zone at a high indicated airspeed. The turbulence can be extreme. If you suspect this, not only add some altitude insurance, but consider slowing to manoeuvering speed just after passing over the range. IF there is dangerous rotor, it will be just under the point where uplift becomes downdraft, and the worst will be under the primary wave. Look at some drawings. Another good reason to use that updraft for all it's worth in a zoom. You will only have 10-15 seconds of lift at a groundspeed of 150 kts in a high amplitude wave, which is where the worst rotors occur. (This usually requires more than 25 kts at ridge level.) Consider avoiding mountainous terrain entirely when the ridgetop winds are this high.

In areas where the ridges are parallel and not real far apart, like Nevada and Pennsylvania, sometimes the wave is either cancelled out or increased by the harmonics. Thus you can encounter a situation where the first range doesn't have much lift or sink or turbulence but the next one is much worse, or vice versa. Sometimes these ranges either end or have large gaps, and one upwind technique is to find the zone of lift, turn to parallel the range, fly to the gap, and then cross.

Always cross ridges at an angle to facilitate turning away and never wait until the last moment. The sink can be at it's absolute worst half a mile from the ridge, well after the primary lift zone has been crossed upwind. My rule of thumb is to expect to lose three thousand or more feet before arriving just downwind of the ridge, and I want two thousand feet AGL remaining when I'm 30 seconds from crossing!!

As far as detecting a wave, you either have lenticulars or you just find them by feel. Any rythmic bands of lift and sink approaching a range, even 50 miles downwind of it, tells you to come up with a plan for safe crossing as related above. The only aircraft immune to waves are military jets that can climb vertically at 10,000 fpm or more!


Fly safe!

Rocky

Bumper
Hello to you too. I'm sure you've seen my flights and I've seen yours on OLC.
I fly a DG-600 out of Warner, Crystal or Cal City normally flew Tonopah for the first time last year and Ely first time this summer wow. I've also seen you on RAS. I know of you but never met you I don't think, hope to some day. I moved up from a C-170 to a C-180 this year and am have been havin a ball with it. The Tonopah trip last year I did a 800 km triangle and held the lead for the Hilton cup till Walt Rogers bumped me in September 07. Thinking of looking for the Chicken strip in a couple of weeks maybe NY's weekend we should meet up.
Russ Barry
1DV