I'm Los Angeles-based and have been trying to fly to Mammoth this entire winter season, but am constantly making a no-go decision based on winds aloft and perceived mountain wave risk in the Owens Valley.

- I'm a relatively new pilot (~250 hours, ~40 in the Sierras, but ONLY with light winds aloft), flying a 150hp GlaStar.
- Have operated out of 10k density altitude strips, and am familiar/comfortable with my performance in the Sierras.
- Understand the mountain flying basics (stay on the upwind slope, cross ridges at 45's, etc.), and have flown on the East of the Sierras a couple times, but usually no more than 500-1,000 feet AGL, and only with super low winds aloft.

Using this weekend as an example, the flight up on Friday afternoon seems doable (winds straight down the valley), but the return trip any time on Sunday seems questionable. Images below. Rest of Wx is CAVU.

Winds aloft forecast (this far in advance) only seems to be available from Windy, and only at 10k and 14k feet.

- At 10,000', the winds aloft seem totally fine, including to the far west of the mountains.
- At 14,000', the winds are anywhere from 25 kts to 50 kts, depending on where you look.

My main concerns/questions are:

1. If I look at winds at 10k (or at 14k in some places) I could call the winds aloft <20kts and make an easy go decision. If I look at 14k, I could make an easy no-go decision... Would you make a no-go decision based on these screenshots, and why?
2. Is it possible to fly under any potential rotors/turbulence? Surface winds are predicted <10kts all day. If I stick to 500ft over the 395, could I stay below it?
3. Am I being far too conservative?
One the one hand: There's news articles of people flying right over the peaks w/ 45kt winds and surviving. I also can't find any large repository of reports on turbulence-induced fatal accidents.
On the other hand: Most forum threads give me the impression I'm committing suicide by flying anywhere in or near the valley with >25kts winds aloft. No information on what altitude/where they're talking about flying though.

I'm very OK getting slammed around in exchange for learning, but don't want to take off from Mammoth into an immediate death trap.

Huge thanks in advance for any advice/tips!

Winds @ 10,000'

Winds @ 14,000'



(Moderators: I was originally going to post this in the Region-specific Forum, but thought it might provide good general knowledge about mountain wave turbulence.)

You are not being too conservative. There are LOTS of turbulence related fatalities in the Sierra's, and in addition to the risk of getting slammed into the ground, you run the risk of being sent into the stratosphere and passing out.

This is in a 170, which doesn't normally climb 2,000 fpm at 16k.



Flying low might save you some bumps, but 500 feet isn't nearly enough room to deal with the downdrafts that you could encounter. Turbulence is not that predictable, and you'd be hard pressed to find an area with the potential for more mountain wave induced violence than the Owens Valley.

Moving over to the east side of the valley will allow you to climb in ascending air...when you turn west you'll be going slow, but you should know long before reaching the Sierra's whether you're high enough. If you can't hold altitude as you get to within ten miles or so of the Sierra's, turn around and climb higher. You need a really good fuel reserve, btw.

When you're high enough to get out of the mountain wave downdraft, you'll start climbing rapidly, since you're now in the ascending part of the wave. As previously mentioned, that has it's own risks.

I've crossed the Sierra's several hundred times, and I can tell you that it's a LOT more dangerous than flying around Idaho or Montana. The highest and lowest points in the continental US are 80 miles apart, and the Owens Valley is smack dab in the middle of them...lots of potential for air movement that will vastly exceed any possible evasive maneuver in a small airplane.

Remember Steve Fossett? You'll learn plenty while being super-conservative...do not push it.

Hammer, much thanks! but a few questions:

-You mention that I'm not being too conservative, but then suggest climbing up and flying into the mountain wave? I'm confused as to why I would want to do that.
Again this is a flight from Mammoth, down the Owens valley towards Los Angeles. Definitely not crossing the Sierra's.

-With regards to 500agl being too low to deal with downdrafts: is that really a concern? How can a downdraft over flat terrain (valley floor) go all the way into/through the ground?

Thanks again!

What Hammer said. At flat pitch, a Huey goes down at 3,000 fpm. Over Ft Carson, east of Pikes Peak, a Huey entered the rhythmic bounce up of a wave, bottomed the collective, and was lifted to 17,500' in a minute or so. That was at least 13,000 fpm minus the 3,000 at flat pitch or 10,000 fpm.

Lower is generally rougher and higher generally smoother. Think white water rafting.

Slower is smoother than faster, but we want to get through downdrafts quickly.

Ridge lift is good when we can use a single ridge up to the pass. The pass is a venturi. Faster air equals more lift.

Don't fight rough unstable air. Use rudder more than aileron to level the wing. Go slow (pitch up) in up air and fast (pitch down) through down air. At 1,000 fpm or more downdrafts, up elevator will just keep us in it longer. If in the assent of a wave, donn oxygen or come back down as soon as possible. WWI fighter pilots patrolled at 20,000 briefly just to stay alive.

Wind energy is good when managed by the pilot, but God is bigger than any engine. Be smart. Be humble.

Sorry...I'm used to flying over the Sierra's, where climbing on top of the wave is the only way to cross. Disregard.

I used to subscribe to the "downdrafts can't go all the way to the ground" theory, but then I learned better up around Reno. Turns out, they can...or close enough to make it a moot point to your aircraft and spine. Wind shear is a terrible thing.

I wouldn't choose to fly at 500 agl because a rotor coming off the Sierra's was preventing me from flying higher, and I SURE wouldn't take off in those conditions. At that point you'd be infinitely better off driving on 395, not flying above it.

Kinetc38,

There is disagreement with whether air goes into the ground. In 17,000 hours flying all day, I have never experienced that. But I always pitched down to fly through downdrafts quickly. I think some who were "thrown into the ground " actually stalled above it attempting to climb out of it.

I have been physically hurt by a serious downdraft. Also got a lot of dirt in my face from the floor of a PA22. Complete temporary loss of control is possible.

Again, what Hammer said.

As someone who has flown through through that area quite a few times myself, I can attest that flying on the lee side of the Sierra Nevada in high wind conditions is nothing to take lightly. When it's calm it can be a magical experience, but when it starts blowing it can be terrifying. There are no simple answers, as the wind conditions and turbulence conditions can be different every single time. A route that works well one time might be a really rough ride the next time. And you can't count on being to see cap clouds or rotors, as the air is often so dry that visible clouds don't have the chance to form.

As far as flying at 500' AGL - in high wind conditions, in that area, definitely not a good idea. While it's true that in theory a downdraft doesn't go into the ground, it can certainly get you moving downward fast enough that you cannot overcome your momentum. Also, the floor of the Owens Valley really isn't flat- there are many local ups and downs which will affect the lower winds. Combine that with the performance effects of high density altitude as you gradually climb north along the valley towards Bishop, and you can find yourself in trouble pretty quickly with not many alternates. The wind forecasts you show indicate the worst of it in the area where you climb from Bishop (4000+ ft elevation), to Mammoth (7000+ ft), with rough terrain topping 14,000 ft to windward, and the view you showed doesn't even take into account the gust factors.

Some places and conditions just are not suitable for light planes. The Owens Valley in those kinds of winds is one of them.

Pretty much no way I'd go myself, with that forecast. But if you do decide to give it a try, I recommend that you do it by yourself and take lots of fuel. If you do hit one of the patches of severe turbulence or strong downdrafts that are probable in those conditions, you might have a tough time convincing your passengers to fly with you again soon.

It blows 50 on the ridges all the time in the Sierras . If it’s calm on the ground and blowing 50 up top there will be some bumps . Less windshear if there is a little wind on the ground as well as up top . I start thinking about not going when ridge winds reporting around 50 . North and East winds on the ridges at 50 is ALOT smoother and way more enjoyable than the same wind from the SW . I would make the trip from Tahoe down to Mammoth with 50 up top depending on what kind of day it is . Some days are just crappy wind . Owens Valley is its own animal . Plenty of days where it’s no problem to fly below the ridge winds . Just ease into it and be cautious .

low rider wrote:... Owens Valley is its own animal...

That I believe to be a true statement!

kinetic38...you might be aware of this already, but statistically you are at one of the most dangerous times for a pilot. The two~four-hundred hour mark has a very high mortality rate, mostly because people are figuring out enough to make them think about pushing outside their previous comfort zone, without the knowledge and experience to extricate themselves from unexpected situations.

My uncle was a high-hour air force instructor, and he drilled into me that I'll know half as much at 500 hours as I think I know at 200 hours. FWIW.

I fly in a different set of mountains. Colorado. I fly across the continental divide half dozen times a year, usually through high passes. I have seen high winds with minimal turbulence and high winds with very little. And turbulence on the lee side of the divide on days with almost no wind in the passes.
One day a couple years ago, I was fairly low time. I flew from EGE to GUC almost direct across the Elk range, right past a few 14,000' peaks. It was a magic carpet ride, at 14,500 I was pretty close to the peaks, but on the windward side. Not even the slightest bump all the way across. The winds aloft forecast for ASE, just a few miles east of my course, was for 45knots at 15,000. One high time pilot friend of mine reminded me that its just a forecast.

A few weeks ago I was flying a Husky from Minnesota to western Colorado. I was flying low enjoying the scenery in eastern colorado, all the ground stations were reporting calm or light and variable. The winds aloft forecast for KFNL was not one of concern, like less than 15, the pass I usually go across is west of KFNL. I was getting tossed around pretty good at 500 agl, so I took it up to 8500' where I got tossed around just as much or more. I was also fighting a headwind of about 30mph. I made the assumption at that time that the winds aloft forecast was in error. I was not looking forward to a 30mph+ wind through a pass at just below 12,000. I may have been overly cautious by taking a northerly route around the high passes, but I don't think so. My route was not smooth, but once I got on the west side of the big ridge, it was smooth as can be. So, maybe the winds aloft forecast was correct?
The situation described in the OP is probably quite different, but I am interested to see the response. And apply that to my situations.

I'm really interested in following this discussion. Over the years I've read posts by guys here about flying through the Sierra's and always wondered if it was just flat lander talk or a real thing. When Faucett died it raised my awareness.

It is possible this spring I'll be doing a trip that will include a flight from Death Valley to the red woods which puts me flying along the east side of the Sierra's. I certainly don't want it to be a miserable trip so I need to learn how and when it is safe to navigate this range.

Huge thanks to everyone here. I'll go throw a donation at the forum.

100% understand/appreciate Hammer's last post, and that's exactly what I've been trying to do: ease into progressively more advanced situations.

So far everything I've been nervous about has turned out to be much safer/easier than expected. Combine that with the few pilot's I've talked to that have flown the valley numerous times who say they never thought to even check winds aloft, leads me to worry that I'm over-thinking here, and should just go fly, and learn.

If it's a matter of extreme discomfort and an unpleasant flight (in exchange for learning about flying in this valley), that's one thing; but I certainly don't want to launch from MMH into an immediate rotor that induces structural damage.

I also don't have a good understanding for the scale/ magnitude of these effects. Is the wave/rotor only a problem close to the ridge, or is the whole valley really at risk? Is there a green safe area somewhere like in the image below? Or is it red turbulent rotors all over the valley?

(Left is West)

whee wrote:I'm really interested in following this discussion. Over the years I've read posts by guys here about flying through the Sierra's and always wondered if it was just flat lander talk or a real thing. When Faucett died it raised my awareness.

It is possible this spring I'll be doing a trip that will include a flight from Death Valley to the red woods which puts me flying along the east side of the Sierra's. I certainly don't want it to be a miserable trip so I need to learn how and when it is safe to navigate this range.

I can actually provide some insight here!

I have flown high and low over the Sierras a couple times now in winds of 15-30 knots. I've found the general advice to hold true:
- Fly downwind of a peak: bumps
- Fly along an upwind slope: smoother
- Winds 20 knots or below: no drama at all, anywhere.
- Winds 20-30 knots: manageable.
- More than that: I wouldn't do it at my experience level.

To be clear, this is unrelated to my question in this thread, which is the ability to fly NEXT to the Sierras (in the Owens valley), with winds higher than 20-30 knots.

I'm kinda a low time glider pilot with 1k hours and prolly 250 hrs wave, a single Lennie (25K documented) Cal City and a flight to 27K at Minden. Your best area for wave flight should be achieved parallel to the ridge. Up close to the ridge you will find the primary , a little further out you will find rotor , a bit further out you will find sink . If you can visualize a sine wave as in electrical sine.

Wave will occur most effectively when wind direction is within 45 degrees or more (90) of the lee side of the ridge line at 25 or more MPH. Most likely you can have Primary, Secondary and possibly tri and more, all with lift rotor sink weakening the further away from the main ridge.

Use the lift for forward speed and altitude, stay out of the rotor (very uncomfortable) and use the down side to come down.

Here's a couple flights out of KIYK notice how close to the ridge these guys were. O2 is a must, use the altitude graph below the map image and slide left to right and you will see the location and speed lift sink stats.

https://www.onlinecontest.org/olc-3.0/g ... Id=7676629
https://www.onlinecontest.org/olc-3.0/g ... Id=7676670

When planning your flight watch W/A at KWJF and KBIH. I'd get a little glider training at KIYK to gain a little respect.

One thing that the Owens Valley has in common with other areas is that mornings tend to be better than later in the day. Of course, if there's a system going through or a strong pressure differential, it can be howling at dawn, and all bets are off. I'm very cautious about taking off from Mammoth. If the wind is up, there are a lot of things working against you.

I used to fly through/over Mammoth Pass to get to Death Valley and Saline Valley. It's gorgeous country, but even at 18,000' there's nothing civilized within glide range for a good 20 minutes. There are some hair-raising survival stories about planes that didn't make it. Dog-legging over Tehachapi to the Central Valley is much lower and friendlier terrain (if less scenic), has lots of airports and services, and can be done without oxygen. That route also spares you the worst of the wave/rotor potential of the Sierra, although I've been knocked around pretty good around Ridgecrest and Mojave. The Tehachapi route adds an hour to the flight time from my home drome, but it's less stressful than straight over the top. Unless it's a calm day under a big bubble of high pressure, I'd go via Tehachapi rather than try flying up the east side of the Sierra.

YMMV

CAVU wrote:I used to fly through/over Mammoth Pass to get to Death Valley and Saline Valley. It's gorgeous country, but even at 18,000' there's nothing civilized within glide range for a good 20 minutes. There are some hair-raising survival stories about planes that didn't make it. Dog-legging over Tehachapi to the Central Valley is much lower and friendlier terrain (if less scenic), has lots of airports and services, and can be done without oxygen. That route also spares you the worst of the wave/rotor potential of the Sierra, although I've been knocked around pretty good around Ridgecrest and Mojave. The Tehachapi route adds an hour to the flight time from my home drome, but it's less stressful than straight over the top. Unless it's a calm day under a big bubble of high pressure, I'd go via Tehachapi rather than try flying up the east side of the Sierra.

YMMV

Again, I'm talking about departing Mammoth. Flying there is no problem, but crossing the Sierras over to the central valley with 60 knot winds aloft seems like a more daunting proposition than flying the valley.

(Left is West)
[/quote]

Not having flown in the waves and rotors of Owens Valley I can’t give you any advice based on local experience. Having flown in and investigated waves and rotors in the Alps, the Rockies (Colorado) and the Andes, in gliders, I could tell you a lot about wave and rotor development and characteristics and spice that with “interesting” stories.
Re your sketches: neither one describes a typical scenario. Rotors tend to develop close to the lee slope (left/West), reaching from ridge height down to almost valley floor. It’s a dynamic system, so they will sometimes “roll” downwind across the valley and dissipate their energy on the uphill side, temporarily destroying the low level wave flow.The laminar wave flow itself might dip down as low as perhaps 1000ft AGL, typically to about half the height between ridge and valley floor and go up to… 49000 ft is the glider altitude record over Owens Valley.
In the end all depends critically on the vertical wind profile (shear).
I would definitely stay away from the lee slope, no matter what altitude.

The three most important wave research projects were carried out in/over the Owens Valley: the 1951/’52 Sierra Wave Project, the 1955 Jet Stream Project and the 2006 TREX (Terrain-induced Rotor EXperiment), the first two subject of a very interesting and entertaining book: Exploring the Monster by Robert Whelan.

Glidergeek wrote:I'm kinda a low time glider pilot with 1k hours and prolly 250 hrs wave, a single Lennie (25K documented) Cal City and a flight to 27K at Minden. Your best area for wave flight should be achieved parallel to the ridge. Up close to the ridge you will find the primary , a little further out you will find rotor , a bit further out you will find sink . If you can visualize a sine wave as in electrical sine.

Wave will occur most effectively when wind direction is within 45 degrees or more (90) of the lee side of the ridge line at 25 or more MPH. Most likely you can have Primary, Secondary and possibly tri and more, all with lift rotor sink weakening the further away from the main ridge.

Use the lift for forward speed and altitude, stay out of the rotor (very uncomfortable) and use the down side to come down.

^^^^^^

This is exactly what has me so frazzled. I'm here trying to figure out if it's safe to fly through a valley far away from the peaks, and hearing that it's still too dangerous; meanwhile glider pilots are over here flying straight into the mountain wave... what gives?

Kinda sounds like the only "safe" place to fly, in these conditions, is IN the wave (with lots of experience)? Trying to avoid the wave/turbulence by staying to the east of the valley is too risky and unpredictable?

I would suggest reading the FAA's Glider Flying Handbook; specifically chapter 10.

https://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/glider_handbook/

Gliders navigate rotors and waves regularly seeking lift; it is dangerous if you don't know what to look for, even for them. But knowing that it can be done safely will encourage you to seek better instruction on the matter. There are really good glider schools in the Sierras because of this dynamic. I would suggest getting some glider instruction that will help you understand the air you are trying to navigate. If you don't want to get the rating, at least get some time, instruction, and experience feeling and visualizing what the air is doing in various wind conditions.

Another helpful book is Sparky Imeson's Mountain Flying Bible:

https://www.amazon.com/Mountain-Flying-Revised-Sparky-Imeson/dp/1880568179/ref=sr_1_1?crid=3OIG54GP0PUFC&keywords=mountain+flying+bible&qid=1580261783&sprefix=Mountain+flying+%2Caps%2C189&sr=8-1

Its a good read and helpful in understanding the effect that terrain has on wind currents.

It is said the private pilot cert is merely a "license to learn"; and that is very true. I firmly believe that adding the Glider manual and some glider time to the curriculum would be very helpful.

Most of the time, within 500' of terrain, we get less orographic or hydraulic lift than thermal lift action. Because wave action is dynamic and progressive, it can be much greater for good (up) and ill (down.) Sympathetic energy, we don't march troops across bridges, increases some kind of math thing with each repition. That is why Hobbs, NM, Moriority, and Colorado Springs have glider operations down range.

I think Hammer explained how waves can get going quickly in the tighter Sierra range. Vast vertical space available high to low terrain.