Mountain Wave

[Nibbler]

I had my first experience of mountain wave last week. As a fairly new PPL with less than 100 hours P1 it created some concern.

Flying between Cumbernauld and Bournemouth between St Albans Head and as far south as Luton the effects were greater than 500ft pm decent, enough for the PA28 Archer to barely maintain level flight at full power with an IAS of 70Kts at 7000ft. Climbing was out of the question. The direction of the wave was 90 degrees off and there were no physical external signs, like lenticular clouds.

The effects of wave were never covered on my PPL course, apart from a little bit in Met theory. I wonder what the results might have been in a slightly stronger wave at a lower altitude and how you would get yourself out of such a situation safely?

[Pilot DAR]

There are specific mountain flying courses available in western Canada. They are well worth the money, and even then, just the tip of the iceburg for learning about this.

The key is not planning to get yourself out, but planning to not get yourself in. Getting out is sometimes just not possible, and you won't know 'till you're in! It sounds like you were in a very gentle one. Good for you, it got your attention without hurting you, many are not that lucky. Both mountains and thunderstorms are pretty, and intriguing. Give them both about the same amount of space when flying...

Pilot DAR

[Saab Dastard]

Join a gliding club - particularly one like Deeside at Aboyne - they know all about wave flying! They want into it - but that's only when it's going up.

SD

[BOAC]

Nibbler - Google will tell you lots about waves. Not quite sure what you mean by 'at 90 degrees', but in basic terms wherever there is a down wave there is an up wave not far away. If you plan to fly along a ridge or row of hills in wave conditions, best to route on the upwind side where the air will almost certainly be going up. If you cannot, and get caught, step sideways towards or away from the ridge to find the 'up'. If you are going 'across' the wave, relief will come shortly:).

I had wave over the highlands a while back in a Cessna 310 at FL85 which went from full power 80mph to throttles closed 160mph.

[SNS3Guppy]

This absolutely astounds me. I keep hearing people posting about not having been taught regarding using their mixture, about mountain waves, density altitude, weight and balance, etc...these are all very basic things that should be taught in ground school before the flying ever begins...and reinforced and taught throughout the flight training. We're not talking esoteric subjects of passing interest; these are fundamental to learning how to fly an airplane; the bare-bones basics, and the building blocks. Are these things seriously being omitted? I find this hard to believe.

[M609]

Mountain waves are scary, more so the first time you "try it"!

Living in a part of the world where wind and craggy terrain is plentiful, I've had the 'pleasure' of ending up in several during my short flying career! :uhoh:

They are however something that you can plan against, and even if you get caught in a bad one, you can get away from it. (You might find yourself mighty close to the valley floor before things calms down, but 99% of the time you will find calmer air.)

I ended up in a mountain wave on my first post-license navigation bimble in a C-172. It was a bit windy from the SW, 20-35knts, but SKC/-15C, so i planned to fly well above highest terrain elevation on the parts of my flight I know are prone to waves. About half way up a valley heading north at 7500ft (and positioned in the valley as far away from the peaks as I though necessary) i got hit by a wave coming off the Njunis mountain massif (5633ft) , and the fun and games began.

At max power and Vy all I got from the old Cessna was a 800 fpm descend (!) :ouch:

http://img.photobucket.com/albums/v477/M609/Div/Dividalen.jpg

In short I ended up about 1000ft AGL over a lake to the north (Aptly called "Dødes vann" or "The lake of the dead".......) before things calmed down, and the Cessna began to climb again. Have to admit the blood pressure was a bit high for about 10 minutes! :D

Now, have encountered a few more since then, but I've learned to read the wind forecasts with a bit more skepticism, and stay away from the mountains as much as possible wind the wind is up.

[K.Whyjelly]

I wonder what the results might have been in a slightly stronger wave at a lower altitude and how you would get yourself out of such a situation safely?

I seem to recall from the mists of time reading an AAIB report about a C150/152(??) that got caught by strong mountain wave activity in the (I think) Lake District. The maximum downward vertical velocity far exceeded the aircraft's maximum ROC and as a result the aircraft got dumped on the side of the mountain.

Unless you are an experienced Alpine flyer or glider pilot versed in the ways of mountain wave then exercise extreme caution when MW is forcast

[mad_jock]

I think its more to do with regional bias with whats required to stay safe in the area.

Weight and balance is not included in this statement.

Density alt in the UK is not normally an issue for most if not all of the year, temps are sub ISA and most airfields are sub 100ft elevation. So for alot of pilots instructors included density alt is a theoretical concept which is never touched on unless they go on holiday and do a bit of flying abroad. There is a couple of air fields where it is an issue eg netherthope.

I think the mixture thing is mainly to do with the fact that most VFR flights in the UK are capped at A5.0 by either wx or airspace restrictions most don't go above A3.0, the instructors know the theory of leaning the engine but very rarely put it into use.

Up in the north we did used to cover the problems and issues regarding flying near hills. But due to said hills and lack of controlled airspace we couldn't expose the students to the joys of flat feature saturated plains and avoiding complicated bits of controlled airspace with a multituded of various ATC agency's to be contacted. But the southern london schools could but couldn't expose the students to the joys of getting caught in a washing machine in rotar or the bum twitching moment of being at full power going down at best glide speed.

As an ex-instructor with most of my time in the North I would be very wary of flying out of say Redhill (very near to 3 of the london airports or approaches) and it would be quite stressful flying around that area VFR. And vice versa I should imagine a instructor from Red hill would find it equally stressful dealing with the scottish wx and navigating through the hills.

In the UK we are a bit finatical about using carb heat other places in the world eg Fl they hardly mention it apart from a pre flight check. Come to think of it in my PPL in FL they didn't mention mountain wave. But they certainly mentioned CB's, funnel clouds, gust fronts and the like.

[fernytickles]

Also be aware how far those mountian waves can travel before they really dissipate. We live in Wisconsin, where the tallest bump is 1952 ft above sea level, so any mountain waves have come from a lot further west. I have experienced slight to moderate - +/- 2-300 fpm RoC or RoD flying south from Wisconsin, so not going any nearer to those great big Rockies. The distance from Denver to Milwaukee is over 900 miles, so those waves have travelled a long way to get here.

All the more reason to stay high, and well clear of any potential waves if you have to fly.

I suppose it goes to prove what many examiners say - the licence you get is basically a licence to start learning. If anyone (and I'm not pointing fingers at anyone here) gets their licence, then sits back on their laurels and stops striving to broaden their aviation knowledge through study, they are asking for a scare. Of course, plenty of us still get plenty of scares, study or no study :ouch:

[tuscan]

"Mountain Flying Bible" sparky iversen. Buy it, read it ,learn then go to Canada and do a mountain course (funds ????)
I dont see the point going down the gliding route, they have a different perspective for obvious reasons.

[Airbus Girl]

Well I did my PPL in the USA and you learn about all these things that seem to be omitted from the UK syllabus!!!

I would add that a) everyone going anywhere near big hills should read up on mountain wave as it can be quite scary and b) learning as much as possible about weather should be natural for a pilot.

I know about wave flying as I've done it in a few times in gliders (and light aircraft :) ) however I know what it is like to be in conditons where you cannot get out of the down draft. I've been in Nevada and going down rapidly, in a PA28, with full power on - in fact ATC asked if I was declaring an emergency - they thought I'd had an engine failure!!! There are ways out of it, but sometimes it is strong and takes longer than you think to get out of it.

So - go read up!

[tuscan]

sorry, spelling? Sparky Imersen

[Canadapilot]

lots of fun flying in the Rockies of Western Canada, did all my CPL nav trips through the valleys. My plan was always to check the upper winds before flying as an indicator, always have a get-out plan (e.g. cross ridges at a small intercept angle incase you need to turn around quickly), rotor/lenticular clouds near peaks may be an indicator of MW activity, and be as high as you can...altitude = safety! am sure there's lots more tips other people have....

[gpn01]

The effects of wave were never covered on my PPL course, apart from a little bit in Met theory. I wonder what the results might have been in a slightly stronger wave at a lower altitude and how you would get yourself out of such a situation safely?

As nobody else has yet given a possible solution tothe "what do I do if caught out" I'd like to offer this...

As a very, very, rough approximation, Mountain Wave usually sets up parallel to mountain ridges and perpendicular to the wind direction. So, if you fly downwind of hills/ridges then you should expect some wave effect which varies depending upon wind strength, changes in strength with height and a few other factors. Often the quickest way out of a wave bar is, providing it's safe to do so, change heading by 90 degress.

So, and I accept that this is a very broad generalization (and massively simplified), as a first step try changing heading to give yourself a good chance of escaping the rapidly sinking air.

[SNS3Guppy]

I think its more to do with regional bias with whats required to stay safe in the area.

Weight and balance is not included in this statement.


No, weight and balance wasn't included in this statement, nor did I say it was. A very basic tenet of aeronautical knowledge pertinent to private pilot operations was included, however...and I frequently hear people describe that these things aren't being covered in the course of individual's private pilot training. Important topics, such as mountain waves, weight and balance, mixture setting, carburetor icing, etc. There's really no excuse for an instructor to fail to teach this..."regional bias" or not. One can't assume that a student will only remain in the local area, nor that the local area represents the wide world of flying.

One may live in a flat desert, but should understand mountains. One may live in the desert, but should know about cold weather operations. One may live in the mountains but should understand flat land navigation. One may live on an island, but still must understand cross country flight. All important, and all must be taught.

So far as flight within a mountain wave goes, it's oscillating air; it goes up it comes down. If you can't maintain level flight, so be it. Go down, or go up with the rising air. If the air is rising, then you can either rise with it and come down later, or you can push forward, maintain altitude, and accept higher speed. Or reduce power. If the air is going down, and you can't maintain altitude, then go down with it. Not a big deal.

I've spent much of my flying life, including all my time as a private pilot, in mountainous areas where up and down drafts of up to several thousand feet per minute were common. To this day I still seek out rising air to take advantage of the free lift. Where air is going down, somewhere it's going up...find it. A downdraft of 500 fpm is fairly mild. Even if you're only 500' above the ground to start, that gives you a minute to fly out of it, and the rate of descent close to the ground will decrease markedly as the downflow changes to outflow and reduces in vertical component. In other words, the downdraft or descending air, isn't going to fly you into the ground. It's just a decrease in performance, and that's all.

If you're indeed in a wave, somewhere upwind or downwind of your position you're going to find rising air. Know the dynamics of the wave (based on knowing what's causing it), and you can take advantage of that wave to reduce fuel burn, increase speed, etc.

Waves tend to run perpendicular to the wind. If the wind is out of the east, the waves will run north and south. Find rising air in that wave as you fly south, and you can ride it like a ridge.

When you find a mountain wave, rush to get out of it. It's an ideal learning experience. Explore it a little. Trying climbing and descending and turning in it to find boundaries, learn about performance, learn how to identify it.

You won't always see lenticular clouds with a mountain wave...most of the time you won't see anything. A mountain wave can extend hundreds of miles downstream, and can be found from the surface all the way up into the flight levels. Air quality around a mountain wave might be smooth as glass, or hold severe clear air turbulence. Often as not, it's smooth, and the only indication you'll have is performance.

One doesn't "get caught" in a mountain wave. One simply flies through it, across it, or in it. Then one flies out of it or away from it. Very simple. If one doesn't like one's performance, then turn and fly to a different place. the mountain wave tends to remain geostatic, that is, it tends to stay in one place geographically so long as the wind value remains the same. It's characteristics remain fairly uniform, it's a known quantity. It's not going to follow you.

Flying to another point in space may mean crossing another ridge or trough of the wave...still not a big deal. As always, if you don't like the performance, turn a little and fly somewhere else. Not a big deal. There's nothing to "trap you." Simply fly away.

A mountain wave isn't something to be afraid of. It's nothing more than modified airflow. You can see it in a stream downstream of a rock, sometimes, or as ripples above the stream bed.

[mad_jock]

I agree

In the UK the issue has become cyclic. There are very few experienced old hands in the industry like yourself Guppy. The experence base of instructors and thier supervising Instructors is quite low. Most never fly a complex aircraft after there CPL next step is a boeing or airbus or a FADEC 20 ton Turboprop.

I won't say they are not taught its just that no great emphasis is placed on them. Where as other topics are hammered to death.

[SNS3Guppy]

Well...I think experience is okay, in fact a very good thing, but my concern isn't that students aren't being taught about advanced systems or even retractable landing gear. It's the important things that worry me.

Several threads here have addressed issues in which various posters cite not being taught to use the performance charts in their aircraft flight manual. others have discussed never having been taught how to use the mixture. These are real concerns. Weather related learning is also a big concern, obviously...which is the topic of this thread.

Do the training requirements in the UK not address these topics, or is this a failing on the part of instructors? Either way, it's not endemic to the UK...unfortunately I see it other places too...where I know full well the regulation requires the instructor to teach these things. It's not a failing on the part of the student...it's a failing on the part of the instructor.

This is one of the great values of sites such as this, where the questions can be asked and answered. Clearly someone's being taught these things as there are enough knowledgeable posters right here to properly answer the question to prove this to be the case.

I suppose my biggest concern would be cases where inadequate training is provided, and the student is released on his or her own, not knowing. It's good that individuals take it upon themselves to be proactive and participate here or other such places...but what of those who don't? What can be done to enhance the education process to ensure that others who may not have the information they should, get it in a way that's meaningful and relevant?

[mad_jock]

The comment about going straight from instructing to something large wasn't really meant that way.

Instructors in the UK will tend to stay static once working so they will arrive with 230 hours and then stay in the same area flying 2-4 seaters for 800 hours then dissappear off. They have thier local comfort zone and it's rare they go outside it.

The subjects are contained in the theory. But its been a bit of a spiral for the last few years. I would say its a failing of the instructors, instructor,instructor....... The instructor proberly never got taught it was important in their PPL and the FIC tends to be very instructor dependent some folk get striaght and level battered to death and others circuits. So you tend to know what ever the favorite is of your instructor.

There is virtually no national standardisation of acceptable methods. Each school has there own prefered practise and what one schools views as good airmanship another will think is bad airmanship requiring retraining.

The regional bit comes in because the emphasis on what is the important stuff is regionally dictated. What we considered important up north would be considered worth a mention in passing down south.

And the experence or lack of breadth of experence also dictates what is covered in depth or as a passing comment. What I now consider important has changed from what I used to think was important 3000 hours ago when I instructed PPL and was flying in my local comfort zone.

To be honest I don't have a clue how to lean a piston engine properly, by the time I read about it on here and realised all the myths and instructions I had been told in the past were utter bollocks I was flying turbines. But before I knew any better, and in good faith, I had continued these myths which I had been told.

[RatherBeFlying]

Ascending wave can let you save on gas if it doesn't take you too far out of your way.

Remember that the wind forces air to ascend going over the mountain like water flowing over a rock, then it descends, then it ascends into the primary wave and comes down again and repeats with secondary and tertiary waves etc. until the air settles down.

So if you're in descending wave, there's ascending wave in either direction but heading towards the mountain/ridge will likely take you through the rotor and some major turbulence; so, heading downstream will be easier on you, your pax and the airframe.

Glider pilots learn quickly that if in sink, get out of it. Think 90 degree turn. Not a bad idea for power pilots, especially if it's wave. When in lift, keep an eye out for gliders.

[SNS3Guppy]

It's a similiar problem in the US, unfortunately. I like to call it the heritage of inexperience. It's not entirely the fault of the instructor, in that one low time pilot becomes a low time instructor, and then teaches another pilot, who becomes an instructor...each one knows only what he's been told. Myths creep in, misunderstandings...often as not things are done only on the assumption that it must be right because so-and-so said so.

It's not just contained to primary training, either. I've run into pilots who swear this airplane or that handles this way or that...because that's what they were told, and that's what they saw in the simulator. Never mind that the simulator was set up in a particular fashion to dramatize a principle or behavior in a manner that's larger than life...they know only what they've been told.

That's really part of the refreshing view here. Posters here, hopefully representative of the majority out there, tend to question what they're told. This is a healthy thing. People who ask questions, think for themselves, search out answers...these are pilots who have a future. Pilots who believe everything they're told without looking beyond the mark are asking for trouble.

The internet harbors a lot of half-truth, too. However, it's a fantastic tool where people who would never meet in this lifetime can encounter one another to share thoughts, ideas, and exchange information in ways that was unheard of, not so long ago. Kudos to those who take the time to participate and learn, including the original poster of this thread.

[liam548]

how high do hills/mountains have to be to create serious mountain waves that should be avoided?

Is there a ball park figure, 1000ft+? or does it just ..."all depend".

[aviate1138]

This might help.

Wave Theory for Glider Pilots (http://www.go.ednet.ns.ca/~larry/bsc/articles/wave/wavesoar.html)

Wave can be a useful performance enhancement tool as can cloud streets as all soaring pilots know.

Pay attention to any mention of rotor or lee side eddy clouds! To be avoided at all costs!

[astir 8]

You can see lenticulars in southern England with the right wind direction (westerly) - certainly weak wave can set up over Oxfordshire as a result of the winds hitting south Wales.

Wave is not exclusive to the immediate vicinity of big mountains.

But wave strength & height is certainly related to wind strength & mountain height - hence Scotland which gets uninterrupted airflow from across the Atlantic + the Cairngorms can equal wave to +35 000 feet in the Aboyne area. But there are other known good wave sites for gliders in Yorkshire (Sutton Bank), the Long Mynd (Shropshire) and Talgarth (South Wales) to name but a few. The general indications for the UK are steady westerly winds. The wave "seasons" for gliding tend to be October - May but it can set up at any time of the year. 500 - 800 feet/minute up or down and very strong turbulence at the bottom in the rotor are all possible.

In extreme conditions the rotor seems to be able to get down to ground level and certainly down wave has been known to cancel out what should have been good ridge lift at the Long Mynd.

But if you know where and when to look for it, it's great! (21 000 feet best so far)

[mad_jock]

Very true Guppy and thanks to pilots like yourself for spending the time putting your experence into print.

[IO540]

A few years ago I was going to Crete, straight across the Alps from Swizerland, with the Alpine route being direct from Wangen-Lachen LSPV to Corfu LGKR.

I found tons of stuff on "mountain flying" which, to most people, seem to mean flying inside the Alpine canyons, often below cloud, and the emphasis is to avoid the mountain waves and other turbulence, while not getting into a canyon too narrow to turn around in.

However I was going straight over the top of the Alps. As is normal in VFR, a route had to be planned OCAS and in this case it was FL130 because above that was Swiss Class C airspace (and as it turned out the Swiss would not let me into it) so I would be flying only about 1500ft above the mountain peaks. It was obviously important for there to not be much turbulence due to wind.

I found very little material on how high one needs to be to do this. The best I found was that one needs to be 1000ft above the peaks, for every 10kt of wind flowing across them, to be sure any downdraught is no bigger than a few hundred fpm. It has proved to be a good rule.

Ovee Wales etc it works OK because there isn't much low level airspace there so one can fly high.

On a recent flight in Spain I was crossing the Pyrenees, on a track of about 040, towards Biarritz LFBZ, from Granada LEGR. There was about 20kt of wind flowing across the terrain. I could not get above 17500ft no matter what I did, whereas normally the TB20 will go to 20,000 without any great trouble. Quite obviously there was a descending airflow of about -200fpm... not much but bad enough if trying to stay above the cloud and above icing. In this case the terrain was about 8,000ft below!

The above was an IFR flight so not limited by CAS but I would never again fly across mountains VFR, when limited by airspace above, through which a transit can potentially be denied. It's a way to get snookered, and ATC won't give a damn until you declare a mayday.

[SNS3Guppy]

I found very little material on how high one needs to be to do this. The best I found was that one needs to be 1000ft above the peaks, for every 10kt of wind flowing across them, to be sure any downdraught is no bigger than a few hundred fpm. It has proved to be a good rule.


In a mountain wave, vertical currents can exceed several thousand feet per minute, and can extend twenty or thirty thousand feet above the mountain, as well as several hundred miles down range. Typical magnitudes are less, in the order of 1,000 to 1,500 fpm, but they can be higher.

When approaching a ridgeline close to the ridge altitude in a light airplane, the 10 knot/1000 ft. rule is a good one.

I've spent a great deal of time approaching ridges from about 15 feet above the ridge, in strong winds...knowing where to go in the even that downdrafts and rotors exceed aircraft capabilities is far more important than having sufficient altitude above the ridge. Having that altitude is more about giving you options for turning and exiting, than it is for being in an area where updrafts and downdrafts won't affect you. You'll have to fly far higher than that to escape the effects of a mountain wave.

[MIKECR]

In response to astir 8's post,

Westerlies still produce excellent wave in Scotland, however, some of the most extreme wave we have experienced in the gliding world here in recent years is actually produced in southerlies. To the north of the Cairngorms and towards the Inverness area we have managed fantastic wave climbs. I have enjoyed several 20k plus climbs and excellent cross countries. A number of diamond heights have now been claimed in this area, with wave systems seen working even higher(possibly 40k plus) towards the west coast. On most occasions, a 2000feet aerotow is more than sufficient to contact the wave.

[bookworm]

Are these things seriously being omitted?

I think Nibbler was saying that is was taught in ground school, but that was his first practical experience of a mountain wave. And if you're training in flatland, what do you do? Take the student on a 400 mile navex to some hills in the hope of catching a good example of a mountain wave?

[Gertrude the Wombat]

This absolutely astounds me. I keep hearing people posting about not having been taught regarding using their mixture, about mountain waves, density altitude, weight and balance, etc...these are all very basic things that should be taught in ground school before the flying ever begins...and reinforced and taught throughout the flight training.
How are mountain waves "taught throughout the flight training" in East Anglia?

[steveking]

Other than what I learnt from the oxford CD rom package I don't recall mountain wave coming up at all in my course. I suppose the instructors are going to focus on what they see as relevant. On the other hand learning in essex, CAS was a very topical discussion.

[englishal]

Do we have mountain in southern England :}

Last mountain waves I came across were in Southern California when the Santa Ana's were blowing.....40-60 kts kts across the 11000 peaks. Everyone [as in every commercial airliner and everyone airborne] was reporting severe turbulence.

[ChrisVJ]

I learned to fly at Oxford, mountain flying was not a real consideration and waves were only briefly mentioned in Met.

When I came to Canada and started flying again I was shocked to find I was below the tops of the mountains, very strange sensation for us flatlanders. Then people started mentioning mountain flying courses etc. Several accidents around here in the last seven or eight years attributed vaguely (not usually much evidence after the event) to wave action.

Getting transition training in my amphibian from a local sightseeing pilot we were flying thirty or forty feet above hill top lakes at pretty well the aircraft`s ceiling and encountered turbulence as we flew back over the valleys (Slow down, slow down!) I fly nice days, low winds only, with a relatively low climb cabability I have already seen 400ft per min updraft on final and do not want to find its evil twin.

There are several people doing mountain flying instruction in BC. I am planning on getting some before I get more adventurous.

[SkyHawk-N]

In August I was flying westwards approaching the Rockies just north of Salt lake City when I hit mounatain wave. I was 2,000ft above the highest peak and approaching at the recommended 45 degree angle, my VSI maxed out downwards and I turned tail and fled to my alternate airport on the east side of the range. It was a clear day and there were no clouds to provide warning, my alternate airport was reporting calm winds.

[Mark1234]

My theory may be a little bit rusty, but wave generally requires:

A stable layer low down (i.e. a temperature inversion)
Barrier (mountain range etc.) which protrudes above the inversion.
Ideally a steadily increasing windspeed with altitude above the layer (laminar flow)
Wind direction within 45deg either side of perpendicular to the barrier

The waves set up parallel to the barrier (not perpendicular to the wind) - the inversion allows the wave to 'bounce' back up on the downwind side of the barrier. You'll find wave is extremely smooth. (again, the rotor underneath the wave is not..) They are also geographically static - they do not blow downwind. If there are a series of barriers, like another mountain range 1 wavelength downwind, even relatively small barriers can re-inforce to produce huge wave (NZ being a good example)

So to answer liam548, it all depends - You can however predict from the forecast info. You want to look at a skew-T chart, aka a temperature sounding, and the terrain profile around your area, though they're a bit of a specialist subject.

It would seem to make sense that the fastest way out of sink is to turn downwind, perpendicular to the barrier - go upwind and you have a lower groundspeed, and escape it into the rotor. If you parallel it - good luck!

Of course to have massive sink and turbulence downwind of a ridge does not require wave...

[SNS3Guppy]

The waves set up parallel to the barrier (not perpendicular to the wind) - the inversion allows the wave to 'bounce' back up on the downwind side of the barrier.


Wave orientation is roughly perpendicular to the prevailing wind, but modified by the obstacle causing the wave (and it need not be a mountain). A solitary mountain will have a crescent shaped wave pattern roughly akin to the mountain shape layed down facing downwind...it will curve and be lower in magnitude and closer to the mountain at the lower ends of the mountain, and be farthest with the greatest magnitidue, downwind at a point corresponding roughly with the highest point in the mountain.

Because a mountain isn't a continuous, even obstacle with even neight and gradient, neither are it's effects downwind. Additionally, most of the time multiple mountains exist, and the wave form isn't solitary or a singular repeating wave, but a series of mixed waves more akin the the swells and wave pattens one might see in the surf. Amid these waves can be turbulent rotors which may or may not coincide with the crests and/or troughs of each wave.

Of course to have massive sink and turbulence downwind of a ridge does not require wave...


Quite correct.

You'll find wave is extremely smooth.


In some cases this is true, in some cases it's not. A wave can form a distinct shear which can produce severe clear air turbulence.

They are also geographically static - they do not blow downwind.


If wind magnitude remains constant, this is true, unless atmospheric properties change (airmass change, frontal passage, etc); the waves do move then. If the magnitude of the wind changes, so do the positions of the waves.

In August I was flying westwards approaching the Rockies just north of Salt lake City when I hit mounatain wave. I was 2,000ft above the highest peak and approaching at the recommended 45 degree angle, my VSI maxed out downwards and I turned tail and fled to my alternate airport on the east side of the range. It was a clear day and there were no clouds to provide warning, my alternate airport was reporting calm winds.


It's common to have calm winds near the surface and strong winds aloft, particularly near or above the peaks, in the Rockies. Also strong winds in and around passes or gaps between mountains or saddles...these act as venturis where you'll find a pressure drop and a wind velocity increase.

Very often the best place to be is near the peak; get on the upwind side and enjoy the lift it provides.

I did a lot of fire flying around SLC, much of it in single engine air tankers. We were often maxed out in load, meaning minimal performance...airplanes capability of doing only one or two hundred feet per minute climb. Less than the Skyhawk. What I did to get to altitude, on my way to a fire, was hug the hill, usually with about half a wingspan's distance from the surface or less, and let the rising air carry me to altitude. Approaches to drops are planned the same way; knowing where the rising air is and where the descending air will be found is a key to coming out the other side of the drop alive.

Same thing in the Grand Canyon. When flying from some of the canyon airstrips in heavy loads, often the airplane didn't have the capability to do better than maintain altitude, initially. Takeoffs would be made which lead to flight over a drop-off of one to three thousand feet, and the rising air at the drop off was then used as the lift necessary to climb out of the canyon. Many of those flights were made in 172's, often from dirt strips in high density altitude situations; successfully operating there was all about finding and using the available orographic lift.

Sometimes if you find yourself approaching the lee or downwind side of a ridge and sinking, you can tuck in closer to the ridge to avoid the sink. This places you into rotors, and you have to know where you're going to go and always have a generous escape path...this is something to try after you've got some training and experience in the mountains...but a wave with descending air is a sure sign that somewhere not too far away is rising air of the same value or better...if you can find it you can really boost your performance, reduce your fuel burn, and even enjoy a quieter ride.

Again, waves or even rotors don't trap you. There's no cage there. If you don't like the performance where you are, fly to a different location and see what you get. Find the lift...it's all about looking for lift.

[barrow]

http://%3Ca%20href=%22http://s389.photobucket.com/albums/oo338/pezzer_photos/?action=view&current=StandingLenticularCloud2.jpg%22%20target=%22_blank%2 2%3E%3Cimg%20src=%22http://i389.photobucket.com/albums/oo338/pezzer_photos/StandingLenticularCloud2.jpg%22%20border=%220%22%20alt=%22Ph otobucket%22%3E%3C/a%3EA lenticular cloud over southern California

http://i389.photobucket.com/albums/oo338/pezzer_photos/StandingLenticularCloud2.jpg?t=1227593438

[barrow]

Another a couple days earlier!http://i389.photobucket.com/albums/oo338/pezzer_photos/StandingLenticularCloud1.jpg?t=1227594609

[Nibbler]

Thank you everyone for your advice, links and experiences all of which will add to my (slowly growing) knowledge.

For clarity my FTO and instructors did in fact cover everything (like using the mixture etc) however as others mentioned, some subjects are more relevant to the airfield you are learning at - mountain wave hardly ever affected the airfield and it was never experienced in flight so it was never discussed in any detail. Having said that I now wonder if the topic should be covered better.

SNS3Guppy - couple of great posts on the subject so thank you for your time and effort explaining and in particular the 'what to do if...'!

[vanHorck]

Many years ago I did a flight in the southern french Alps, with an instructor, landing at a few airfields like Barcelonette.

You know how pragmatic the french can be..... He tried to climb close to a ridge but there was a downdraft. He simply said: If we have a downdraft here, there will be an updraft at the other side of the valley, and there was!

It is something that always stuck in my mind regarding valley flying as a potential escape: If there 's a downdraft one side, there must be an updraft on the other side!

[IO540]

How do you find the other side (with the updraught) if the terrain is totally covered in cloud?

The strange thing about the lenticular type clouds is that one often sees them where there is absolutely zero turbulence or wind....

[JW411]

Wave bars are usually only 3-4 nms apart. If you can't see the ground then try to imagine what feature is likely to be setting off the wave (assuming that you know your present position and the forecast wind).

Turn downwind for a couple of minutes and watch your ASI and VSI very closely. As soon as you start detecting an increase in speed and/or lift, resume your original track.

If it is not possible to fly parallel to the wave bar, then try flying a series of small doglegs. I have made considerable fuel savings making use of wave. I once saved 4000 lbs of fuel in an Argosy flying from Tehran to Cyprus and I have had a Belfast flying at cruise speed with the throttles at flight idle over the Massif in France.

I would have to say that my experience in wave soaring in gliders in such places as Dishforth, Sutton Bank and Aboyne comes in very handy. You don't have to have dramatic mountains to create wave and it can exist a long way downwind of the feature that is causing it.

I can remember someone getting to 17000 feet in Oxfordshire in weak wave created by the Welsh mountains.

[snapper1]

In order to begin to understand wave it might be very useful for a power pilot to experience it in a glider with an experienced mountain flying instructor. The best sites in the UK to give this sort of instruction are in Scotland so, Aboyne in Aberdeenshire, Portmoak in Fife and Feshiebridge near Aviemore. As others have said, you can get wave anywhere in the UK and some of the other gliding hill sites are good but none are as consistently as good as Aboyne.

It's a massive subject and even the experts like John Williams who flys from Portmoak will tell you that after years of exploring it, they are still learning - and he's a bloke who has flown offical 1,000 km tasks in wave within Scotland.

If you fancy having a look at how we see wave try these two youtube vids. The first is from Aboyne, the second (expletives NOT deleted) is from Camphill, Derbyshire.

YouTube - Glider returning from wave soaring flight through cloud (http://www.youtube.com/watch?v=OQhXRBsIXrg&feature=related)

YouTube - Camphill wave (http://www.youtube.com/watch?v=8PQsysBVsG8)

[liam548]

How do you find the other side (with the updraught) if the terrain is totally covered in cloud?

The strange thing about the lenticular type clouds is that one often sees them where there is absolutely zero turbulence or wind....

and what if you cannot out-climb the wave itself or can you always turn back and head the way you came?

[flybymike]

An Argosy and a Belfast. I just had to check JW411's age...:)

[SNS3Guppy]

The strange thing about the lenticular type clouds is that one often sees them where there is absolutely zero turbulence or wind....


The lenticular cloud form is due to wind. No wind, no lenticular. So, there is always wind where the lenticular is formed. Turbulence may or may not be present.

[liam548]

The lenticular cloud form is due to wind. No wind, no lenticular. So, there is always wind where the lenticular is formed. Turbulence may or may not be present.


so can you still have mountain waves with no wind?:confused:

i see. I should read it as, no lenticular means no wind...

[RatherBeFlying]

The leading edge of lennies show where the ascending wave air drops below dewpoint; the trailing edge is where dewpoint is regained as the air descends and the moisture is reabsorbed.

While the cloud appears stationary, the air going through is not and there can be considerable shear.

Lennies generally show the peak of the wave; directly below is the rotor.

[snapper1]

Liam,

Guppy said, 'there is always wind where the lenticular is formed'.

There might not be any wind where YOU are but there IS wind where the lenticulars are!

[Shunter]

They can be seriously unfunny. I flew through a wave about 10mins from LBA clearing the hills south of Dewsbury and it scared the crap out of me. Eyes shaken in sockets, head banged repeatedly on roof despite being strapped in etc... Mentioned it to Leeds Approach who replied, "Funny you should mention that, just had an Embraer on saying he was unable to descend".

[liam548]

They can be seriously unfunny. I flew through a wave about 10mins from LBA clearing the hills south of Dewsbury and it scared the crap out of me. Eyes shaken in sockets, head banged repeatedly on roof despite being strapped in etc... Mentioned it to Leeds Approach who replied, "Funny you should mention that, just had an Embraer on saying he was unable to descend".

blimey, very local to me. "hills south of Dewsbury", crikey!:confused:

[SNS3Guppy]

so can you still have mountain waves with no wind?


No. A mountain wave IS wind.

[Pilot DAR]

I stumbled upon this FAA AC, while looking for something else. I have not read it, I just noticed the title...

(I tried the link, and it worked for me. I case it does not for you it is: AC 00-57 of 1997, Hazardous mountain winds, and their visual indicators)

AC 00-57 Hazardous Mountain Winds and Their Visual Indicators (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/780437D88CBDAFD086256A94006FD5B8?OpenDocument)

Pilot DAR

[coldair]

I seem to remember that a Vulcan was brought down over the North Sea due to mountain waves / standing waves , from Wales.

Does anyone have any info about this or a link.
Many thanks.

[Tmbstory]

In the Southern Hemisphere the weather fronts would normaly come from the South West and proceed to the North East.

On cloud seeding operations we spent a lot of time working ( or playing ) with these fronts.

I can remember one one occasion a roll cloud formed on the leading edge of the air mass. The Cessna 310 sat nicely right on the top of the roll cloud, in the clear, very little turbulence and throttles reduced. A spectacular flight in all ways and it lasted for many miles. The escape plan was to turn left into the clear.


Tmb

[wsmempson]

This is quite a good illustration of the 'upside' of mountain waves.

Grosse frayeur en snowkite (http://www.koreus.com/video/malik-bouchenafa-snowkite-grosse-frayeur.html)

If anyone wants a translation of what the camera man is saying, do feel free to pm me - but I suspect you'll be able to guess.....:rolleyes::oh::O

[liam548]

This is quite a good illustration of the 'upside' of mountain waves.

Grosse frayeur en snowkite (http://www.koreus.com/video/malik-bouchenafa-snowkite-grosse-frayeur.html)

If anyone wants a translation of what the camera man is saying, do feel free to pm me - but I suspect you'll be able to guess.....:rolleyes::oh::O


!!!!!!!!!!!!! @@$$!!

[BRL]

Woooooaaaahhhhhhhhhhh!!!!!!!!!!!! :D :D

[SNS3Guppy]

Those are upslope winds, but not a mountain wave.

Not a very bright snow boarder, either.

[Flying Farmer]

I've just gone right of the idea of a para glider :eek::O

[liam548]

Those are upslope winds, but not a mountain wave.

Not a very bright snow boarder, either.


anabatic winds?

[SNS3Guppy]

Orographic lifting based on whatever winds prevail.

Waves exist downwind from the obstacle that created them.

[Scotsheli]

I fly in northern Scotland and often plan my routes to avoid the local mountain wave we experience. Thinking back over my last 10 trips, i've experienced some mountain wave effect on at least half of them. Any reasonable (say >20KTS at or below 2000) westerly or south westerly and its a 99.9% certainty you will be sinking if you head off in the wrong direction (high terrain is around 10NM's away). On this basis, its hard to avoid it being taught when you learn to fly here! We do get some very nice lenticular clouds, particularly in April & May!

[mad_jock]

Not a very bright snow boarder, either.

The technical term for them on the slopes in Scotland is tube or muppet or feel bawbag if they have been really stupid. I have never heard a snow boarder being acused of being intelligent.

[liam548]

This is quite a good illustration of the 'upside' of mountain waves.

Grosse frayeur en snowkite (http://www.koreus.com/video/malik-bouchenafa-snowkite-grosse-frayeur.html)

If anyone wants a translation of what the camera man is saying, do feel free to pm me - but I suspect you'll be able to guess.....:rolleyes::oh::O


are these anabatic winds then?
such as

Anabatic Kiteboarding. NZ's Auckland based kitesurfing importer and retailer. Into Wake boarding? Snowboarding? Surfing or Skateboarding? Then you will love kiteboarding. - Lessons Information (http://www.anabatic.co.nz/page.php?id=122)

[snapper1]

Listen very carefully. I will say this only once. (Spoken in a faux french accent, as in 'Allo Allo'.)

Orographic.

Forced upward movement of air upon encountering a physiographic upland. This lifting can be caused by two mechanisms:
1) The upward deflection of large scale horizontal flow by the Orography.
2) The anabatic or upward vertical propagation of moist air up an orographic slope caused by daytime heating of the mountain barrier surface.

[liam548]

Listen very carefully. I will say this only once. (Spoken in a faux french accent, as in 'Allo Allo'.)

Orographic.

Forced upward movement of air upon encountering a physiographic upland. This lifting can be caused by two mechanisms:
1) The upward deflection of large scale horizontal flow by the Orography.
2) The anabatic or upward vertical propagation of moist air up an orographic slope caused by daytime heating of the mountain barrier surface.

gotcha,

Merci ;)

[snapper1]

The picture perfect storm: Photographs capture the terrifying beauty of clouds gathering over Greenland | Mail Online (http://www.dailymail.co.uk/sciencetech/article-1090829/The-picture-perfect-storm-Photographs-capture-terrifying-beauty-clouds-gathering-Greenland.html)

This is really exteme.

[landedoutagain]

Mt. Rainier puts on a show! | KOMO News - Seattle, Washington | Weather Blog (http://www.komonews.com/weather/blog/35631614.html)

good examples (as well as nice pics!) where you see what the way the air flows over a mountain

[SkyHawk-N]

I was going to go flying today but was put off by the following scene (and NO I don't mean the runway was under water! :rolleyes:) ....

http://i145.photobucket.com/albums/r203/Skyhawk-N/MountainWave4.jpg

http://i145.photobucket.com/albums/r203/Skyhawk-N/MountainWave.jpg

There are 2,500ft mountains to the east of us and a 25 mph easterly wind was blowing. The lenticulars were forming at just over 2,500ft, I didn't go and have a closer look. It looked like wave was carrying on over the Pacific for quite a number of tens of miles.

[astir 8]

There have been satellite photos of wave bars all the way from Scotland across the North Sea to Norway - which led to suggestions that a Scotland - Scandinavia glider flight might be feasible. :ooh:

I never heard of anyone trying it though! :uhoh:

[Fitter2]

Hi Skyhawk

You don't worry when the sky looks like that.

But when it looks like this, be careful

http://i38.tinypic.com/317cz6u.jpg

[SkyHawk-N]

I don't think we have mountains near us big enough to cause that spectacle, the Cascades some 80 miles to the east could and I would really like to see that happen. When there is just a light easterly along the coast here the fillings bounce out of your teeth. I know that flying when lenticulars are visible will not be dangerous, just very unpleasent for an afternoon bimble.