Crossing the barrier of the mountain range that you launch from is a big challenge. It could be the start of an epic adventure, but it could lead to disaster if you cross the mountain too low and get caught in the lee-side turbulence. So how do you judge the correct method of crossing, when it's your first time?

1. What weather conditions are you looking for?

Light base wind (10-15kmh) will help by allowing thermals to rise vertically. Post-frontal conditions (after a cold front has passed) are good because the air is usually clear and cold, which means thermals will rise fast through it. There should be no inversion layer (a layer of warmer air on top of cool air below) which leads to good climbs to great altitude. Ideally, there'll be a few cumulus clouds to show the way.

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, it's ridge-soaring. If you need to work the lift in 360 degree turns or tight figure-eights to survive, then it's 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 at this height, because you'll often be planted in the ground with the sink you'll find behind (downwind) of a big ridge.

4. Where is the best place to go over?

The highest point in the ridge will give you the best climbs, because the thermals will be forced to rise vertically and the horizontal component of the wind is reduced. Low points or saddles in the ridge often cause a strenghthening of the wind and weaker lift. The trick is to find a place where you can climb high, then peel off away from it to glide towards a low point in the ridge so you avoid the heavy sink behind the high peaks, and you get the boost of strong wind behind you for a long glide.

5. Getting pushed over

You try to thermal high, but get whooshed over the ridge too early and have to fly forward again. How do 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 (unless you've reached an airspace ceiling). 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 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. Often the ground surface behind a mountain is vegetated and bad for thermal production.

9. What's the catch?

If you don't find that first flatlands thermal after your big glide over the back, you'll land somewhere well behind the launch site. You might have to walk back, try to hitch-hike, or you could phone your pals (retrieve may cost you lunch).

10. Goal!

Pick a route with a nearby goal, like a farmstall or village, so you can walk there even if you can't fly all the way. Most cross country flights begin with an IFR approach - I Follow Roads. You don't have to be a pioneer to enjoy a good distance flight. If you're lucky, you'll have a retrieve vehicle at your toes, and the wind at your back. Once you've crossed the barrier, who knows where you'll go?