PDA

View Full Version : Mountain flying


witchdoctor
4th Oct 2003, 05:19
Having just come come back from a trip in the Highlands, it got me thinking about the specific techniques required for flying in mountainous terrain. One of the areas I had to visit was well into one of the glens and required me to operate at an altitude well below the summits (about 1000' below) of the terrain either side. The valley was typically narrow and steep-sided, but plenty wide enough in still conditions at our operating altitude to perform 30 degree turns, with room to spare.

However, the conditions were far from still, with perhaps a 20 - 25 kt wind being funnelled into and around the glen, making the flying much trickier, with turbulence and changing airspeeds, and this was a little concerning as my first experience of this terrain up close and personal. My co-pilot and photographer has much more experience in these conditions and gave me sound advice on handling, and happy to report we had no problems.

So, my question is this; what techniques do you employ in mountain flying? I'm aware of the dangers of rotor streaming on the lee side of hills and lower cloud bases, changeable weather, potential variations in wind direction of 180 degrees, but not much more. In the absence of a mountain rating/checkout, what else should I know as essential knowledge?

Cheers, WD

Capt BK
4th Oct 2003, 16:03
Im afraid I wouldn't have a clue but it sound's like a hell of an excuse for a holiday to Canada. I've seen loads of advents for mountain flying courses there, flying is quite cheap too :)

Aerobatic Flyer
5th Oct 2003, 00:15
what else should I know as essential knowledge?

Best thing is to fly with someone experienced until you are comfortable. The overriding rule in the mountains is to leave your options open, and not let yourself get trapped into a dangerous situation. Here are a few tips:

In valleys, fly to one side so that you have plenty of room to turn round.
Be aware of the tendency to descend when turning towards a valley, and to climb when turning towards a hill. The latter can kill you easily.
When crossing a ridge or a pass, cross at an angle (normally 45 degrees) so that you can easily turn back if the conditions on the other side aren't good.
If there's wind, fly on the side of a valley where the wind is blowing up the slope.
Cables will kill you. Know where they are, and lookout all the time.
Know how much space you need to do a 180 degree turn (it's less than you think). Think of the effect of wind on such a turn - another reason for flying on the correct side of a valley.
Be decisive. Turn back early if you aren't comfortable, or if you have any doubt about your position.
Think about the effect of wind on ridges and passes - as well as turbulence and up/down drafts, there can be venturi effects which cause dramatic change in windspeed in a short distance.
Don't forget the "usual" stuff - fuel, T's and P's, etc.
Enjoy it!

IO540
5th Oct 2003, 02:22
Would I be right in thinking that assuming one is able to fly on instruments (i.e. climb if necessary) icing conditions are going to be the real killer when flying in between terrain like that?

On Track
5th Oct 2003, 07:47
All good points, Aerobatic Flyer.

There is no substitute for a comprehensive mountain flying course. It is spectacular but challenging flying.

I did mine in New Zealand, but I'm aware that a number of flying schools in North America offer them as well.

englishal
6th Oct 2003, 01:26
And also if flying in a hot climate (not very likely in Scotland :D) bear in mind density altitude. If you're mushing along and hit moderate / severe turbulence it is very likely you'll stall.....

I always leave about 2000' between myself and the mountains, unless flying in a pass, then I try and leave 2000' AGL to the floor of the pass.

Another good reason to fly to the right of a loch in Scotland is incase you meet a tornado flying down the middle at 450 kts, and make sure you have your txpdr on so that they can 'see' you....

Cheers
EA

Aerobatic Flyer
6th Oct 2003, 02:00
I always leave about 2000' between myself and the mountains, unless flying in a pass, then I try and leave 2000' AGL to the floor of the pass.

Sometimes it's better to be low. Usually the wind is stronger at altitude, and you can sometimes encounter severe turbulence which you would have avoided lower down.

When I was learning mountain flying in the Alps, I once flew on a very windy day with an instructor. He asked me to cross an 8300ft pass and told me not to exceed 8500ft. I thought he was crazy, so surreptitiously climbed a bit higher to give myself a safety margin. As we entered the pass at 8800ft, the turbulence was so bad that I almost lost control. We did a 180, descended to 8400ft and tried again - and got through with no problems.

As On Track says, the answer is to do a mountain flying course. A lot of conventional wisdom doesn't apply in the mountains, and sometimes what seems safe isn't.

david viewing
6th Oct 2003, 20:19
Something learned on a mountain flying course in Canada and not mentioned here so far is Slow Down! It's amazing how much smaller your turning circle is at 70kts.

Incidentally my instructor couldn't believe that we have maps you can't write on - to her, checking off each valley on the chart with a time as you pass it is fundamental to knowing where you are.

Tall_guy_in_a_152
6th Oct 2003, 22:09
David

What sort of charts do you use? I write on my CAA half mil charts all the time (the laminated ones). Even paper Jepperson charts (tried it once, didn't like it) can be written on in pencil.

TG.

Edited because I think I realise what you mean. Canadian and US charts are so cheap that you scribble on them and throw them away

Floppy Link
6th Oct 2003, 22:51
Be aware of the tendency to descend when turning towards a valley, and to climb when turning towards a hill. The latter can kill you easily.

Visual illusions! Certainly when HM the Queen paid for my helicopter training, mountian flying was a mix of visual and instrument flying...there are any number of false horizons out there in the hills to get your brain all confused. Sloping strata in the rock, sloping ridgelines even sloping cloudbases can give you a false horizon so crosschecking the artificial horizon every couple of seconds was a must, as was ensuring the VSI was on zero if you wanted to fly level (as in a circuit to a landing point). I remember having an inadvertant 500fpm climb downwind just because I was next to a sloping stratum.

There's a lake in Snowdonia somewhere that looks like it has a sloping surface because of the visual illusions (great for water skiing though - who needs a boat!)

And one of my training mistakes... with a (simulated) engine failure turn downslope, it gives you so much more time than turning towards rising ground!

And respect the wind and fly on the updrafting side of the valley...we sat in a Wessex in updrafting air with the tailwheel on a rock and the collective lever almost on the floor, using less torque to hover in the updrafts than it took to turn the rotors while stationary on the ground.

Remember wind doesn't go underground (unless Arthur Scargill has been on the baked beans) so if caught in a downdraft it will eventually stop - see pass crossing story above - you just may be quite close to the surface by then.

Cross at 45 degress also applies to big power lines if you happen to be stooging around at 200ft (looking for somewhere to do a precautionary forced landing...of course)

There's lots more, get a good instructor, PFA Coach Charlie Huke would be a good place to start, he used to teach mountain flying at the SAR Training Unit.

Cheers
Russell

http://www.espotlight.co.uk/gbtbi/listlogo.jpg

Aerobatic Flyer
6th Oct 2003, 23:36
checking off each valley on the chart with a time as you pass it is fundamental to knowing where you are

Unfortunately a standard 1:500000 chart is pretty useless in the mountains. 1cm represents 5 km, which can easily be enough for two valleys separated by a mountain. They'll only be identifiable on the chart by changes in colour - if they make it onto the chart at all. If the visibility is at all bad, you can easily be fooled into turning into a narrow valley thinking that it is the large one you can see on your chart.

It's better to use a 1:200000 scale map, with contour lines on it. Much better still, if you're going to be flying often in the same area, is to get to recognise the major features with a local pilot then not have to use the map at all in flight.

Floppy Link

if caught in a downdraft it will eventually stop

Yes....... but it may stop so close to the ground that you will crash anyway. Or it'll be a downdraft over a slope which won't stop before it reaches the bottom of the valley; if you're flying over that bit of slope at the time..... :( :(

I know of two accidents in the last year that were caused this way. One a PA28 which ended up on a glacier (although the downdraft was only one of many factors that caused that), and the other a high performance glider that ended up in the trees.

P.S. Nice P47! :)

Fly Stimulator
8th Oct 2003, 02:54
The New Zealand CAA publish a good booklet on mountain flying. (http://www.caa.govt.nz/fulltext/Safety_booklets/Mountain%20Flying.pdf)

That's where I did my mountain training, and it seems to have worked in the northern hemisphere too so far. The rugged peaks of the Chilterns hold no fear for me now.