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Hi to all. Been floating around here for a couple of years and not really posted that much, but I do find this forum to be a great resource. I am from down south and really the the mountains around here are more hills (less that 3000 ft) but i have been following a couple of the threads (the heli logging one, also watching on TV and the heli skiing one).

 

Anyway a quick question for the more experienced among us. At what point does wind go from being helpful to dangerous to deadly in the high mountains (think above tree line, heli skiing, Canadian Rockies, Colorado Rockies, Sierras, Utah, etc). What about the type of rotor system (Bell 206B/L, 205/212 vs Astar, 407, 412) and how does that change the equation.

 

I know every situation is different, but around here hills are 500 to 1000 ft above surrounding area and not really craggy, just rolling hills, so up to 30-40mph is good to go as not too much turbulence. How does the really high stuff, or mountainous terrain (cliffs, cirques, pinnacles, knife edge ridges, etc) change things and when do you shut it all down.

 

Attending a mountain course (the best ones are in Canada from what I hear) is the best way to find out, but that is out of the question for now.

 

Thanks in advance for any informative reply's.

 

Mixmaster

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Hi to all. Been floating around here for a couple of years and not really posted that much, but I do find this forum to be a great resource. I am from down south and really the the mountains around here are more hills (less that 3000 ft) but i have been following a couple of the threads (the heli logging one, also watching on TV and the heli skiing one).

 

Anyway a quick question for the more experienced among us. At what point does wind go from being helpful to dangerous to deadly in the high mountains (think above tree line, heli skiing, Canadian Rockies, Colorado Rockies, Sierras, Utah, etc). What about the type of rotor system (Bell 206B/L, 205/212 vs Astar, 407, 412) and how does that change the equation.

 

I know every situation is different, but around here hills are 500 to 1000 ft above surrounding area and not really craggy, just rolling hills, so up to 30-40mph is good to go as not too much turbulence. How does the really high stuff, or mountainous terrain (cliffs, cirques, pinnacles, knife edge ridges, etc) change things and when do you shut it all down.

 

Attending a mountain course (the best ones are in Canada from what I hear) is the best way to find out, but that is out of the question for now.

 

Thanks in advance for any informative reply's.

 

Mixmaster

Mixmaster,

 

Once you get winds above 20 knots or so, every cirque, ridge, or mountain top will have a surprise for you. Also depends on your load. I won't get into the technique that I use here as you are better off to seek advise from a school for the technical explanation.

 

We have been heliskiing here with a B2 and L-4, same landings, similar loads and as I hate to say it, the Astar works better in gusty conditions, 30-40 knot with gusts to 60 or so, 6000-9000

feet, leeward side of the range (Coast Mountains, Central B.C.). After 2 attempts- my limit, I would pick a lower landing and the B2 ran the guests to the top. (2 runs later he quit as well)

 

Main thing to remember- don't get on the leeward side of the ridge in down flowing or circulating air. Always have an escape route when the bottom drops out, because it will.

Strong steady wind, the sideways approach works good for me and you always have an escape route in front of you, straight ahead.

 

 

Fly Smart, Fly Bell

(unless it is too windy)

 

B.M.

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Hi, Mixmaster,

The speed of the wind is not so much of a factor as how turbulent it is.

The turbulence can be caused by the shape of the mountain it is flowing past, or by the nature of that particular weather system.

Some pilots describe some weather systems as being very "mechanical". This is represented in the aircraft by a short, sharp chop and a 'banging' flight.

Some days the wind has a huge amount of 'downflow' to it. Though this doesn't always make a landing more difficult, it will slow your ascent, it will need to be allowed for on the approach path you choose, and shows that each day brings its own challenges.

Because of the vagaries of the weather on any particular day, there are not too many fixed rules that you can use on such days. You will have to assess the conditions at that time.

 

What is more predictable is the effect of the shape of the peak you are working with. This will have a huge influence on whether you can land there or not. It makes sense that round, smooth knobs are much easier to work with.

Some peaks feature a cliff on one side. If the cliff is on the downwind side, the peak will be easier to work with, but don't get into the diving curl behind the peak.

 

Landing on a shoulder behind a peak will also be difficult, and worsened by a windy day as even a smooth wind will now be disturbed by the peak.

Cirque landings are to be avoided on windy days if possible. The wind swirls inside them, and is very unpredictable. If you 'have to' land in a cirque, make sure you have a large power-margin, have an abort route, and do a few recces to see if the wind is acting the same each time.

(and remember, there is only one "have to" in our industry.......you 'have to' make it back to the hangar, whether you landed in the cirque, or called it off!!)

 

Always consider the altitude you are at. The aircraft will not be as responsive in thin air, so it may not be as safe to land at a higher peak on the same day.

 

Before landing somewhere, consider the take-off.

For example, the bottom of glaciers are usually troughs of downflowing air between two moraine walls. They often feature a lot of descending air which you won't be able to climb into, because of the rising terrain ahead. Therefore you will have to depart downwind. If it is snowy, the snowball will be charging down the icefield with you, so your visibility will be hampered. If the departure path is a flat, white surface.......be very careful!!

 

Types of aircraft.........hmm, this should start a debate.

Bell mediums have been popular for years but their problem can be in the engines.....i.e they must speed-up and slow down a lot as you work in turbulent air. Because of the big, fat blades these aircraft have, it is sometimes hard for the governors to keep the rotor RPM at 100%.

Some of the multi-blade systems will have a lower inertia to them, and be easier for the engines to compensate for rapid power changes......especially if the helicopter is fitted with a good FADEC control system.

Please remember....if you are requiring a lot of big power changes to land somewhere.....maybe you should go somewhere else. And just because your passenger "landed there last week in a 407 on a windier day", it doesn't mean you can land a 212 there today.

 

Tail rotors.........A mountain approach will require a crisp tail rotor that responds well to pedal inputs. I like the basic design of two or three tail rotor blades back there.

I have not liked the "mushy" effect that a fenestron or NOTAR system give the aircraft.

 

Eventually you will learn how to fly on windy days, and be able to handle more wind/turbulence as your experience and skill level increases. You will also be more comfortable about saying "sorry, not that peak today".

The approach is vital. If you can't get the aircraft to set-up 'smoothly' on the approach... the landing will be a disaster. "Smoothly" is a relative term depending on all the factors mentioned above. Even if a wind is strong and/or rough, you may still be able to land if it is predictable.

A recce flight on your approach path (which always features an abort route) will tell you so much. And a second recce will tell you MORE than twice as much !!

 

If you can't figure-out what the wind is doing after a few recces......go somewhere else.

WC Fields said, "If at first you don't succeed, try again. If that doesn't work...give up, 'cos there's no point in making a fool of yourself."

 

Be careful out there.

 

 

 

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Hi, Mixmaster,

The speed of the wind is not so much of a factor as how turbulent it is.

The turbulence can be caused by the shape of the mountain it is flowing past, or by the nature of that particular weather system.

Some pilots describe some weather systems as being very "mechanical". This is represented in the aircraft by a short, sharp chop and a 'banging' flight.

Some days the wind has a huge amount of 'downflow' to it. Though this doesn't always make a landing more difficult, it will slow your ascent, it will need to be allowed for on the approach path you choose, and shows that each day brings its own challenges.

Because of the vagaries of the weather on any particular day, there are not too many fixed rules that you can use on such days. You will have to assess the conditions at that time.

 

What is more predictable is the effect of the shape of the peak you are working with. This will have a huge influence on whether you can land there or not. It makes sense that round, smooth knobs are much easier to work with.

Some peaks feature a cliff on one side. If the cliff is on the downwind side, the peak will be easier to work with, but don't get into the diving curl behind the peak.

 

Landing on a shoulder behind a peak will also be difficult, and worsened by a windy day as even a smooth wind will now be disturbed by the peak.

Cirque landings are to be avoided on windy days if possible. The wind swirls inside them, and is very unpredictable. If you 'have to' land in a cirque, make sure you have a large power-margin, have an abort route, and do a few recces to see if the wind is acting the same each time.

(and remember, there is only one "have to" in our industry.......you 'have to' make it back to the hangar, whether you landed in the cirque, or called it off!!)

 

Always consider the altitude you are at. The aircraft will not be as responsive in thin air, so it may not be as safe to land at a higher peak on the same day.

 

Before landing somewhere, consider the take-off.

For example, the bottom of glaciers are usually troughs of downflowing air between two moraine walls. They often feature a lot of descending air which you won't be able to climb into, because of the rising terrain ahead. Therefore you will have to depart downwind. If it is snowy, the snowball will be charging down the icefield with you, so your visibility will be hampered. If the departure path is a flat, white surface.......be very careful!!

 

Types of aircraft.........hmm, this should start a debate.

Bell mediums have been popular for years but their problem can be in the engines.....i.e they must speed-up and slow down a lot as you work in turbulent air. Because of the big, fat blades these aircraft have, it is sometimes hard for the governors to keep the rotor RPM at 100%.

Some of the multi-blade systems will have a lower inertia to them, and be easier for the engines to compensate for rapid power changes......especially if the helicopter is fitted with a good FADEC control system.

Please remember....if you are requiring a lot of big power changes to land somewhere.....maybe you should go somewhere else. And just because your passenger "landed there last week in a 407 on a windier day", it doesn't mean you can land a 212 there today.

 

Tail rotors.........A mountain approach will require a crisp tail rotor that responds well to pedal inputs. I like the basic design of two or three tail rotor blades back there.

I have not liked the "mushy" effect that a fenestron or NOTAR system give the aircraft.

 

Eventually you will learn how to fly on windy days, and be able to handle more wind/turbulence as your experience and skill level increases. You will also be more comfortable about saying "sorry, not that peak today".

The approach is vital. If you can't get the aircraft to set-up 'smoothly' on the approach... the landing will be a disaster. "Smoothly" is a relative term depending on all the factors mentioned above. Even if a wind is strong and/or rough, you may still be able to land if it is predictable.

A recce flight on your approach path (which always features an abort route) will tell you so much. And a second recce will tell you MORE than twice as much !!

 

If you can't figure-out what the wind is doing after a few recces......go somewhere else.

WC Fields said, "If at first you don't succeed, try again. If that doesn't work...give up, 'cos there's no point in making a fool of yourself."

 

Be careful out there.

 

 

Wow !!! very usefull info there OT....thank you!

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If you can't figure-out what the wind is doing after a few recces......go somewhere else.

WC Fields said, "If at first you don't succeed, try again. If that doesn't work...give up, 'cos there's no point in making a fool of yourself."

Be careful out there.

Excellent, can't add much. My instructors used to say that the wind was more often your friend than not.

  • get close to the terrain. Contour fly tight to the hill to feel the wind there but always leave an exit path.
  • no steep approaches. Makes for less downward momentum to overcome on late final and less power changes, easier to sense the power required for the landing as you're gradually adding it on the way in.
  • be aware of the "demarkation line". This is the "line" separating the smooth, upflowing air on the upwind side of a ridge or cliff from the roiling air back from the lip. Stay out of the later. This may require a steeper approach in the smooth air or another spot! The demarkation line varies in steepness with wind speed and tends to lie down at higher speeds but at much higher speeds could be steeper with a strong flow up the cliff. I'm open to correction on this one from other moss backs!
  • explain a bit of this to your customers so they understand why you're rejecting one spot for another. I don't think we've been good as an industry with educating our customers about the limitations we face (weights, winds, experience, etc.). These vary daily, too.
Does anyone have a "manual" or graphics on this? Great topic.

 

Cheers . . . .

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I was told once a hundred years ago, that if you thought about water flowing over and around the mountains, you would have a good idea of what to expect from the wind.

 

It tends to give you a "good visual" of what you might encounter...

 

Watch a creek full of rocks and boulders and you will see all the things that the wind does, from swirling, turbulence, eddies, and whatnot.

 

 

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