Over mountains - how high?

[IO540]

I am planning a route through the Alps this Sept, from Switzerland to Venice.

I haven't yet worked out the route; it is non-trivial because there is so much controlled airspace. But at this stage I would like an idea (without attending a mountain flying course) how high one needs to be above say the nearest peak within 10nm either side of track, to ensure that the various types of wind don't get you.

The aircraft has a ceiling of 20,000 feet at the configuration in question and I have oxygen. So no need to fly in between anything - I intend to go well above.

I gather 2000ft might be enough provided the forecast winds aloft are below 30kt.

I would also aim to do the transit as early in the morning as possible.

Any advice would be much appreciated.

[Genghis the Engineer]

My experience is, frankly, limited. However, flying over Scottish mountains of about 4,000ft, I've found that to clear most significant "funny wind effects", 6,500ft does it.

What I don't know is whether the main player is that I was about 2,500ft above the peaks, or that I was at about 160% of the height of the peaks.

The other player, at least for me because I don't get to play with multi-engined aircraft very often, is that I'd plan it on the basis of a consistent series of viable glide diversions which are, at the very least, survivable.

G

[RodgerF]

Quote

The other player, at least for me because I don't get to play with multi-engined aircraft very often, is that I'd plan it on the basis of a consistent series of viable glide diversions which are, at the very least, survivable

G

I am not sure whether having two engines will necessarily help. As you will know the ceiling on many light twins on one engine is below the Alpine mountain tops. So one could have a more controlled descent into a valley but not be able to climb out again if there was no place to land within.

[englishal]

I normally go 2000' above. The mountain waves can extend up to 30-40,000' and 40 odd miles down wind anyway...

cheers
EA

(want a co-pilot :D )

[slim_slag]

IO540,

It's all a matter of personal preference, but 2000ft above a ridge with 30knts winds could turn into a wild ride. 20knts @ 2000ft above would be about what this old pussy would want, some say clear the tops by 1000ft for every 10knots of wind. I've crossed many a 10000ft ridge by 50ft on a cold & smooth day, which are wonderful to fly in.

Also be wary of any shear in forecast winds aloft, i.e. the winds at 12000 ft are different from those at 15000ft.

Most important of all, always have an out. That's the second and third most important things too. And probably fourth and fifth.

[Fly Stimulator]

IO540,

The CAA in New Zealand have a good 'Safety Sense' style booklet on mountain flying.

You can download a pdf version from their web site here. (http://www.caa.govt.nz/fulltext/Safety_booklets/Mountain%20Flying.pdf)

The index to others in the series is here. (http://www.caa.govt.nz/safety_info/good_aviation_practice.htm)

[Aerobatic Flyer]

Things aren't always as clear cut as they seem. If the wind is calm, then you will may have a more relaxing trip by flying high above the peaks (and I would recommend 3500ft above the peaks, as this guarantees you the 1000m clearance that you need if you want to fly over a national park (in France.... not sure of the regulations in Switzerland)). However, if there is wind, which there usually is, the situation can be very different. The turbulence at altitude can often be severe (by light aircraft standards), and paradoxically it can be calmer to fly well below the peaks and clear passes at the lowest possible altitude. That does require you to know precisely where you are at all times, and to understand the rudiments of mountain flying, so it's probably better to wait until the wind is calm.

You should be careful of the forecast winds aloft. In the mountains they can often be different to what the forecast indicates.

[mad_jock]

Is there not some effect where by you have to alter the MSA dependant on the wind over the mountains.

I would go as high as possible. Better air under you than over. Single engine drift down its better to have as much time as possible to sort out your options.

MJ

[TonyR]

That does require you to know precisely where you are at all times, and to understand the rudiments of mountain flying That's what it takes.

I know it's a pain to do another course but if you want to fly in the Alps, or anywhere with hills over 6,000 ft, it is really best to fly with someone who has been there, or at least take their advice.

I delivered a C340 to Croatia a few weeks ago and I thought the aircraft was going to fall apart at FL150, 6,000 feet above the peaks I was over. I would have been more comfortable at 5,000 ft in the valley as I met another pilot who came low level to Trieste the same day.

In the UK we usually have an escape from severe turbulance within a few miles, but in the Alps it can last a very long time. I have needed the odd change of Y fronts upon landing.

But you will just love flying in the hills, so get some good local advice each time before you fly a sector and do it.

Tony

[slim_slag]

Rough air is a funny old thing. I've followed people through passes who have been reporting turbulence which was going to shake their engine off, and I encounter what I describe as light occasional moderate. Sometimes I hardly feel a thing, the bumps have gone elsewhere. The vast vast majority of turbulence in the UK in VMC will be light, severe turbulence means uncontrollable plane and (on the very very rare occasion you hit it in the flatlands) will last seconds. True moderate turbulence can be quite unpleasant and yet most people think they are going to die and report it as severe/extreme.

Now I agree that all bets are off in the mountains, and I've been woken up in the back of a 747 when crossing the Alps. However for every person who finds it smoother in the valleys I will find you another who find it smoother several thousand feet over the top. Sometimes I am tightening my belts as the previous five times I have gone over a certain ridge I have nearly lost my teeth, and it is as smooth as silk.

As I said, when flying around the mountains you need options. Being 5,000 feet above the highest mountain gives you more options than being in a valley 2000 feet below the peak. If your plane can reach FL200, you are licenced to be up there, and you have O2 then I will take FL200 every time.

You might still get shaken around, but that's the price you pay for being around mountains. Mountains have local weather systems which are essentially unforecastable, and winds aloft will be wrong in places. That's why you have to pick your comfort level. If winds are forecast at 30knts at the level you are crossing then you can bet the mountains are somewhere producing winds doing 60knts. It gets bumpy, such is life, and if the forecast winds aloft aren't all over the place I'd go over the top...

[klausk]

Mountain flying is more than just altitude. Somebody told me that you can't outpower the moutains, but you can outsmart them - meaning that a good plan and strategy how, when and where to fly are important. The rule of a thumb I'm hearing around the Rockies is that you have to double the highest peaks if you don't want to feel the effects of the mountains. Not many pilots have this luxury (not to mention that summer effects and plane's age can lower the ceiling altitude substantially). Definitely and for sure check with the local pilots -- they know the area the best.

I also suggest to check the following book "Flying the Mountains" by Fletcher Anderson (McGraw Hill, ISBN 0-07-141053-8) http://www.amazon.com/exec/obidos/tg/detail/-/0071410538/qid%3D1090010237/sr%3D11-1/ref%3Dsr%5F11%5F1/102-4962697-2741708?v=glance&s=books

[MLS-12D]

I also suggest to check the following book "Flying the Mountains" by Fletcher Anderson Or consult the Mountain Flying Bible (http://www.kitplanesbooks.com/mountain_flying_bible.htm), by Sparky Imeson. If you don't have the time to track down a copy, this (http://www.mountainflying.com/crossridges.htm) will have to do.