Mountain flying

[FO Gyro]

Hi,

With regard to the unloading of rotors and turbulence, have you ever experienced severe turbulence in the Cape mountains so far?

I ask this because despite my 500 odd gyro hours, I have yet to experience severe turbulence where I am thrown out of the seat, or have got myself into an unloaded situation, but then I have done all my flying on the highveld thus far.

I need as much advice as possible with regard to flying around here. I've only been down here for about 2 months now. My MT-03 is at Stellenbosch. I must say, these big mountains do scare me somewhat, as one doesn't know what turbulence is waiting around them.

Your reply would be most appreciated.
Glenn

[Gyronaut]

Hello Glen

Yes, I have been banged around real good in these mountains once or twice.

The worst has been on returning from the Karoo, a front was approaching from the west so the North Westerly slams into the mountains and creates huge standing waves and severe rotors behind them that stretch for miles and miles and catch you very unexpectedly.

VSI at +1500 one minute being pushed down into the seat then -1500 the next, seatbelt involutarily gets pulled real tight and you sit bolt upright. Sunglass pouch was lying on the floor on one occasion, hit the roof, then the floor, then the roof... Airspeed from 80 to zero... yes ZERO and back to 80 in 3 seconds or so, repeatedly. (Bwana Sir Eric Torr explained this to me... he says severe updraft/downdraft causes a low pressure as it whips vertically past the pitot tube reflecting 0 indicated air speed )

The only advice I have when it happens is to continue to fly the machine or get outta there. If it gets too rough (as it has for me), go park. I have landed in front of a shed in Ceres, asked them to store my machine till after the weather has passed which they happily agreed to, arranged lift home, went back a week later and fetched it (we don't need long runways etc so its a non event) and a much safer option in my humble opinion.

I'd rather live to fly another day than boast about how I crossed the mountains in really bad weather.

I also dont think you need to be nervous of the mountains under normal circumstances, just remember that they are far steeper than they look from the air and with max 10 degree or so landing slope in our gyro's before we hit the stops and get dynamic roll over, we'd best have a valley floor or flat area within autorotational distance at all times or we'll execute a perfect auto only to roll down the mountain - moertoe.

Fortunately the little Rattex behind us doesn't know its over the mountains (or the sea) so it usually behaves really well

Having said all that, it truly is one of the more special things in life and we (my softness and I) consider ourselves most fortunate and priviledged to be able to fly for e.g. the Tulbach valley - Breede, Hex River, Karoo area at will.

Fly safe and ENJOY!

Len

[FO Gyro]

VSI at +1500 one minute being pushed down into the seat then -1500 the next, seatbelt involutarily gets pulled real tight and you sit bolt upright. Sunglass pouch was lying on the floor on one occasion, hit the roof, then the floor, then the roof... Airspeed from 80 to zero... yes ZERO and back to 80 in 3 seconds or so, repeatedly. (Bwana Sir Eric Torr explained this to me... he says severe updraft/downdraft causes a low pressure as it whips vertically past the pitot tube reflecting 0 indicated air speed )

That sounds quite scary, particularly if one is in an open gyro like a MT-03. Psychologically one would feel as though one is about to be thrown out of the gyro, which is terrifying!

At what altitude were you above the mountain tops? The winds must have been very strong to experience this type of turbulence...

[Gyronaut]

Altitude varied between 500ft agl (in that area about 5000' - 5500') and 1500 ft agl (6500' - 7500). Full power in the downdrafts, back to almost idle in the updrafts concentrating on best airspeed mainly.

Yes, even in an enclosed gyro I find I double check the seat belt constantly and also really make sure there are no loose articles.

Fortunately we mostly fly for fun so if the conditions aren't ideal, we don't go so it really doesn't happen often!

The awesome flights on perfect days FAR outweigh the rough ones as a result. Don't let it worry you, the machines are most forgiving under those conditions. Your wingspeed is about the same as your 737's

[Gyronaut]

By the way, this is what my softness thinks of the mountains!!

Inverdoorn 124a.jpg (92.95 KiB) Viewed 3619 times

Loving it!

Maybe I should post this in the Gyro Softness thread rather?

[johnht]

Thanks for a most interesting topic, guys!

It's great to learn from others' experiences so that you can be better prepared when you encounter unpleasant situations.

John

zu-jht

[Magnifan]

Hi All

I am a notorious lurker on the forum!

Last weekend three of us flew up to a fly-inn at Andrews Field, Striusbaai. Jetranger was a bit hung over from the microlighters ball, it seems, and chose to motor up with Badnav and his softness, Thelma, who had come down for the ball. This suited Learjet, Paul Ackermann and I, as Len kindly hauled some additional fuel for us. We routed over the mountains at Bain's Kloof and then followed the still flooded Breede river from the bottom of Bain's Kloof via Robertson and Bonnievale and then hooked a right direct to Andrew's Field. From there we flew to a very tight grass runway on some property of mine in Hermanus where we all spent the night.

The next morning Paul elected to fly directly back to his homebase at Diemerskraal over Theewaterskloof and Franchhoek. Dave and I decided to route back to Goedverwacht and Morningstar along the coast as the weather seemed absolutely perfect with hardly any wind. We enjoyed a wonderful flight along the coast as far as Hangklip but, as we rounded the point, we flew into a howling South Easter. The stretch of coast from Hangklip to Gordonsbay is almost totally devoid of emergency landing sites and we were soundly klapped all the way. The sea was whipped into a white frenzy below us and when I attempted to fly closer to the very steep coastline which is essentially a ridge of mountains that plunge directly into the sea I got into some very unstable air which at times was ascending up the slope and caused us to shoot up at over 1000 ft/min and then later turned into downdraughts that took my breath away. In fact Learjet, who was on my tail all the way, commented once we had landed, that as I was doing a radio call I suddenly dropped out of the sky ahead of him and he noticed that my call was interrupted by a long silence before I continued in a slightly shaky voice. I decided that I was going to take my chances in the sea if the donkey died and routed further out to sea where it was marginally better.

I have flown quite a lot in the mountains around the Cape, but this was probably my worst experience of turbulence. I find that a rule of thumb of 1000ft for every ten knots, given to me by an experienced trike pilot, has held me in good stead. I also find that it is preferable to avoid flying through low points between the peaks as the wind tends to accelerate in these areas, rather climb above the peaks. I have flown back from Hermanus over Sir Lowrie's pass at 4500 ft in a 40 mph wind quite safely and without much turbulence.

Last weekend's experience has just served to increase my respect for the stable characteristics of the Magni M16 that I fly as, despite the conditions and a certain amount of anxiety, I never felt that I was anywhere near to losing control of the aircraft.

[FO Gyro]

It's good that we can share experiences. Having my gyro at Stellenbosch (ony been there about 2 months now), I end up flying near the mountains quite often, and am keen to learn more from others that fly gyro's in the area.

Someone at Stellenbosch, gave me advice to be careful and stay away from the mountains when an Easterly wind was blowing.
Magnifan, if a south easterly is blowing, I would imagine you would get hammered with the downdraughts flying from Cape Hangklip towards Gordan's Bay.

Climbing higher, should always be the safer option, but I find I tense up quite a bit on the stick when flying at +4000ft AGL. I am not comfortable at all. Do others share this "fear of heights" as well? It's horrible, because when compounded with some turbulence, you feel as though you are maybe going to somehow fall out, or be thrown out of the gyro. Silly, because at lower altitudes, I am comfortable with bad turbulence.

Magnifan, I want to fly to Ceres sometime. Any advice for flying through the Bainskloof pass? Does is get very turbulent there? I would prefer to keep low, rather than have to climb over the top (its that fear of heights thing again!).

[Learjet]

I want to fly to Ceres sometime. Any advice for flying through the Bainskloof pass? Does is get very turbulent there? I would prefer to keep low, rather than have to climb over the top (its that fear of heights thing again!).

Glenn - I'm no great fan of heights either but I prefer the high road to the low road when it comes to crossing mountains.I usually go over the top of Baineskloof rather than through it. (although this is at odds with how some other gyro pilots do it.) My rationale is that I'd rather worry about rock below me than worry about rock below me AND on either side of me. Also I can put 1000ft per 10 knots wind between myself and the crest quite easily (and still turn around if I want to) - that's a little harder to do laterally in a mountain kloof where you don't know what rotors await you around the next bend. Jonathan's account of our flight around Hangklip last weekend is a case in point. One turn around the mountains and the sea below us changed from glassy smooth to white-horses! A simple rule of thumb for the Cape South-Eater is that it usually pics up late morning / noon so I like to do any mountain crossings in the early morning.

[Low Level]

Climbing higher, should always be the safer option, but I find I tense up quite a bit on the stick when flying at +4000ft AGL. I am not comfortable at all. Do others share this "fear of heights" as well?

I thought I was the only freak. Talking to some flying buddies last week, they were quite surprised to hear that I hate, even going over 1500 ft AGL. Even while training, when we had to climb to 2000 ft AGL to do maneuvers, I almost crapped myself. The first time I said to my instructor, I'm not comfortable, It feels like I'm going to fall out of the gyro.

Like you say, I tense up, and any funny feedback from the stick freaks me out. Two weeks ago over Rhino, I decided to climb to very low clouds, about 2000 ft AGL. When I reached it, I did a power off decent, a fun manouver I love to do every time I fly. Coming from 2000 ft .

I love flying, but hate heights.

P.S. You will NEVER find me at 4000 ft AGL.

P.S.S. Maybe ZULU must make me patch as well: The 1/4 mile high club.

[Gyronaut]

I think all rotowing pilots experience that sense guys. We train in close proximity to the ground so we become accustomed to it.
The mighty Buzz Bezuidenhout took me to 10 000ft AMSL between Rand and Carletonville for high altitude familiarisation during my heli training years ago and even he hated it!
(PS, we auto'd all the way back from overhead Carletonville to Rand in a R22 and kept the carb heat on all the way)

Fact is that altitude is your friend. If something does go wrong you have much more time. If its catastrophic, 300ft will kill you as dead anyway. (As they always say, "Its only the length of the scream that varies" )

I agree it makes one feel very vulnerable but I keep reminding myself that it increases my options for a forced landing and gives me time in the unlikely event of an emergency.

Fly safe

Len

[Magnifan]

Hi Glen

I also become very tense at altitude and far prefer to keep as low as possible, but when it comes to crossing mountains I grit my teeth and go up using the 1000ft per ten knots rule! If it is dead calm, one can comfortably fly much closer to the mountains and even route through the valley's but when there is a wind blowing don't think that it will be easier to find a nice vally and route through it in order to avoid too much altitude. It is in the vallys that you will really get thumped.

If you think of a wind blowing towards a mountain with a gap in it, the air that hits the face of the mountain needs to divert over it or around it. Some of the air on either side of the gap will choose to go through the gap, along with all of the air that was going towards the gap anyway. This causes a big increase in the speed of the air moving through the gap, along with the associated wind shear and turbulence caused by the airstreams mixing in the gap. It can be a lot more scary than the altitude. I tend to choose a low point, like Bain's Kloof, and then route over the low point, but above the height of the peaks on either side.

You have to deal with a few minutes at altitude, but just keep telling yourself that it is much better up there than lower down.

Regards

Jonathan

[Gyronaut]

Quite true about it being more harsh in the 'gap' Magnifan. As an engineer I am surprised you didn't quote Bernoulli's Principle...

ex Wiki
"Bernoulli's principle is equivalent to the principle of conservation of energy. This states that in a steady flow the sum of all forms of mechanical energy in a fluid/gas along a streamline is the same at all points on that streamline. This requires that the sum of kinetic energy and potential energy remain constant. If the fluid is flowing out of a reservoir the sum of all forms of energy is the same on all streamlines because in a reservoir the energy per unit mass (the sum of pressure and gravitational potential ρgh) is the same everywhere.



Couldn't agree with you more about flying OVER the gap because that gives you a flat area (even if its a riverbed) below you to go land if you must!

Enough talk, its an awesome day, lets go fly!?

Rgds

Len

[Magnifan]

Indeed Bernoulli's principle applies, but I would hate to think what the Reynolds Number is!

[Magnifan]

Oh, I forgot to respond to the suggestion that we go flying, sorry the salt mine calls! What about Friday pm?