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Sir Lowry's Pass presents a barrier to the wind
How to go over the back of a big mountain range
by Greg Hamerton (

1. What weather conditions are you looking for?
For Sir Lowry's Pass, I like a light westerly wind (W 10-15), post-frontal conditions (after a cold front has passed), no inversion layer (ie. good climbs up, up and away), ideally with some cumulus clouds to show the way. Usually in spring, before the summer South Easters arrive.

2. Isn't it dangerous to go over the back?
What about rotor?
Rotor is most severe low down in the lee of a mountain (ie. below and behind the crest). It is also more severe in strong winds. Don't go over the back on a ridge-soarable day, because the wind is too strong, and you don't get high enough. But on a thermic day, you can quite safely go over the back with double the height of the ridge, and outglide any nasty air. How do you tell the difference between a ridge-soarable day, and a thermic day? Ridge-soarable : the hang-gliders will be out in full force, and you don't need to turn in circles to gain height. If you're just 'parking' above the ridge without effort, its ridge-soaring. If you need to work the lift in 360 degree turns or tight figure-eights to survive, then its thermic.
3. How high do I need to go?
As high as you can go. This may be your last climb for a long time. The rule of thumb for safety is double the height of the ridge. It's roughly a 400m ridge, so you need at least 400m above it. But it's pretty pointless going over the Pass at this height, because you'll just be planted in the ground with the sink you'll experience on gliding behind (downwind) of a ridge like Sir Lowry's.

4. Where is the best place to go over?
For the purposes of your first crossing, I'd recommend going over near the northernmost curve of the pass, above the peak we usually soar close to takeoff. It's where the best thermals track up the spine from turkey patch. The N2 is reassuringly close by, and there are no tricky technicality like ridges and endless forests. For those with more xc experience, going over on the south edge of Hanskop can be done, where you have the option of going up to 2300m (airspace ceiling is raised). This is a better xc route, as there are ridges downwind to jump to, and it's the way I went when I flew to Bot River. Be prepared to walk if you don't outglide the moon country, though.

5. You try to thermal high, but you get whooshed over the ridge too early and have to fly forward again. How can you get higher?
When a thermal runs up the ridge, it gains momentum in that direction, and keeps its oblique angle for a distance behind the crest, until it begins to pull more vertically. Lee-side thermals also join with it to assist in straightening the rising collumn. It follows that if you work the thermal tight against the ridge, you're going to be thermalling low over the crest. If you lose the thermal then, you're in the compression / venturi and can't glide forward again, and run the risk of sinking into the rotor.

What's the solution? Make your into-wind legs longer on your thermalling turns. As you reach ridge-height, you should be moving directly upwind within the thermal. Often you'll find stronger cores which left the ridge earlier. Often you can fly out to find a thermal further from the ridge. Work this one until you're getting near to crossing the crest again, and fly forward. Thus, in a process of zig-zagging, you build altitude systematically over a few thermals. Once you're high enough, you'll find the thermals straighten out above the crest, and you can keep circling for longer.

6. When do I leave the thermal to go on glide?
Never (except if you're at the airspace ceiling - at 1200m asl at Sir Lowry's Pass. That's about 800m above takeoff, and plenty high enough). Hold onto the crossing thermal. It will protect you from the surrounding sink, and will drift with the prevailing wind. Even if the thermal is a zero, it's giving you an effective 100:1 glide angle, so don't rush away. Just float until it's broken up, and you're well over the back, then glide away.

7. Speedbar? Trim? Brakes?
What's best glide in this situation?

Quite simply, just put your hands up and let the glider glide. Only slow down when you fly into a thermal. Only speed up if you're in very, very heavy sink (> -3m/s)

8. Do I turn in the first broken thermal, or keep gliding and hope for something stronger?
Use the first flatlands thermal. It is my experience at Sir Lowry's Pass (and Dasklip's Piekernierskloof Pass) that if you ignore the first thermal, you're on the deck in ten minutes, wishing you hadn't. It has something to do with the descending air you're in, and the thermals being scarce. Sir Lowry's has acres of forest over the back, and white sandy soil - a bad combination for thermal production if I ever saw one.

9. What's the catch?
If you don't find that first flatlands thermal, you'll land beside the N2 somewhere near the Sqwattazz. Be intelligent - don't whip out your cellphone, and don't leave your vario, GPS, radio, wallet, and sunglasses lying in plain view. I hide that sort of stuff as soon as I land, and do a quick-quick pack, walking out before the inevitable crowd of smiling faces begins to think of doing anything but smiling. They're usually awed by the 'strange brave flying person' for a while. Smile back, wave, and be on your way. Walk back toward Sir Lowrys for a kilometre or two before sitting down beside the road and hitch-hiking (difficult, free) / phoning your pals (retrieve may cost you lunch).

10. Goal!
The first goal is the farmstall over the back (Orchards?), which has a wonderful bakery, restaurant and grass lawn to lie back in post-cumulus bliss. It's about as difficult as getting to the farmstall in front of Sir Lowry's. After that, you're on your own - you can choose the IFR route (I follow roads) along the N2, or go for the hills to the East.

May the wind be at your back, and the retrieve vehicle at your toes.
Launching at Sir Lowry's Pass
Ready to go! Waiting for the right cycle.

Soaring along waiting for the crossing thermal
Hang around in the right place for getting high

Big peaks mean more vertical wind
Lots of lift in front of steep cliffs.

On glide it's best to be efficient
For best glide just put your hands up