RC slope soaring
- my personal passion!
Slope soaring with an rc glider is one of the most relaxing and straightforward ways of enjoying radio control flight. It's relatively easy to master and, for me, is a personal favourite type of rc flying!
If you live close to a hill then you might have already tried your hand at rc slope soaring, but if you've yet to give it a go then this page will show you some of the basic tips to get the most out of your flight, and your glider.
Finding a suitable slope
This is of course very important! Not all slopes or hills are suitable for slope soaring, but many are, provided that flying a radio control glider (or operating any rc model) is permitted in that area - always check first!
An ideal slope will have a drop of at least a couple of hundred feet and will have a gradient of at least 30 degrees, but the steeper the better. A tree-free slope is ideal, but if there are trees on the bottom half of the slope then that's not so bad - so long as there aren't any near the top. Trees not only present the obvious collision risk but can also create 'wind shear' problems whereby smooth airflow is disrupted, thus making your life at the Tx sticks a little harder.
Another important factor is whether or not the top of the slope, where you'll be flying from, is reasonably flat and clear of obstructions - this will be your landing area. To give you an idea of a good slope, take a look at the photo below - this is actually my local hill that I fly from:
The final point to remember when choosing a suitable site for slope soaring is of course the wind. To get the best flights, the wind needs to be blowing directly up the slope at a fairly constant force. So, a slope or hill that rises up from open land in front of it is a good one to fly from, because the wind blowing over the land will be uninterrupted.
Coastal sites are a good and favourite option, on-shore sea breezes or stronger winds coming off the sea provide excellent slope soaring opportunities if you can find a suitable spot to fly from. Coastal air is famously silky smooth most of the time, since the wind comes in over the flat sea with nothing to get in its way and create turbulence.
Launching your glider
We'll talk about a standard hand launch here, because this is how the majority of rc gliders are launched for slope soaring (some fliers use a small catapult/hi-start system).
Ideally you should be standing a little way back from the start of the slope, and facing directly into wind.
With all pre-flight checks complete, hold the glider at, or just above, head-height with one hand directly below the wing, or immediately behind it if it's a low-wing design glider. Hold the transmitter in your other hand with the thumb on whichever stick it naturally falls onto. A transmitter neck strap is a real life-saver here!
Take a few steps forward, or stand still if you prefer, and give the glider a very firm push into the air, out over the slope. Make sure that the glider is launched horizontally, or even pointing slightly downwards. If you launch with a 'nose up' attitude then there's a chance that the glider will stall and crash if your push wasn't strong enough, or if the wind up the slope pitches it up too much before adequate airspeed has been reached.
As soon as the glider has left your hand, put that thumb on the other transmitter stick. Once launched, the glider should catch the rising wind and your slope soaring has begun!
Beware of strong winds, or wind gusts, when launching, especially with smaller and lighter gliders. If the wind is strong enough, it can easily take your glider out of your hand, over your head and behind you - before you've even realised what's happened. Only launch when you feel it's safe to do so.
Using the wind
RC slope soaring is made possible because of the action of the wind. Any moving air that encounters rising land is naturally forced upwards over that land, and this upward movement of the air is called ridge lift. It's this rising air that you're using to keep the glider airborne - if the wind stops, or dies down, then the glider will only stay up for so long.
The optimum area for catching this ridge lift is just in front of and above the upper reaches of the slope. If the wind is constant and you keep your glider within this area, you can stay slope soaring all day long!
So to get the best out of it, you need to fly your glider parallel to the slope face and not too far away in front of you i.e. fly by making a pass left to right (or right to left), turn the glider through 180 degrees and repeat the pass going the other way. The important thing to remember here is to always make your end turns into wind i.e. away from the slope.
If you fly the glider too far away from the slope face then you risk flying out of the rising air and losing lift, which can result in a long walk down the slope to retrieve your fallen glider!
As you fly from side to side, you'll notice that your glider will gain altitude with each pass - hopefully. This is the rising air pushing the glider upwards.
If you're confident to do some basic aerobatics, just let the wind carry the glider higher as you fly it from side to side. When you've reached a good height, now's the time to have some fun!
The video below shows these basic slope soaring tips, as performed on the RealFlight simulator (sorry about the jumpiness of the vid, something happened during upload to YT to produce this)....
...while below is a slope soarer on the Phoenix sim...
This next video is of me enjoying an evening flight on my local slope with my Eraser EPP 'combat' glider...
When slope soaring it's important to remember to make your end turns into wind, but of course there may be times when a downwind turn is needed or inevitable, for whatever reasons. Bear in mind that turning downwind can rapidly accelerate the glider, especially if the wind is strong; before you know it the glider can be over your head and behind you, and suddenly out of the lift zone. With no lift the glider will rapidly descend and your natural reaction to apply up elevator will likely result in a nasty stall - obviously a situation to avoid if you can.
Also bear in mind that good lift will not always be present, even with a wind blowing up slope. From time to time you are likely to encounter 'sink', which occurs when cooler or downward moving air passes through. There's not much you can do if you fly into an area of sink, other than hope that it doesn't last too long, and keep flying around looking for better air.
This is the trickiest part of rc slope soaring, but if you've chosen a good slope with a clear and flat top then you shouldn't have too many problems.
Get the glider to a suitable height (say 100ft. or so) above you and bring it round in a wide circle back over the top of the slope and out to your side. It'll speed up a bit as it turns downwind coming off the slope, but that speed will decrease again as you turn it back into wind for final approach.
Don't let your glider get too far behind you, but when it is at a point where you feel that you can bring it down to land somewhere close to you, then begin the landing approach. Gently turn it back into wind and use the elevator to get it onto the ground.
If the wind is strong, you might have trouble getting the glider down using a normal approach angle. In fact, you might even find yourself having to go around several times if you overshoot and the glider catches the wind again too close to the edge of the slope. Just keep trying and see each aborted landing as good practice!
Other tips for RC slope soaring
- Judging the wind strength is very important - too strong and you'll have trouble launching and controlling your glider, too weak and the glider won't gain enough altitude for a successful flight. If this happens, you might end up with a long walk down to the base of the slope to retrieve your model!
- Don't fly over your head and behind you, unless landing. It's easy to become disoriented and if this happens the results can be nasty.
- Don't fly downwind (with the wind) for too long if you can help it. An rc glider will quickly lose lift flying downwind, and it's not always easy to regain lost altitude.
- If you're going for long-duration slope soaring sessions, don't forget about the radio control gear batteries! If they die, so does your glider.
- If you're completely new to rc slope soaring, try and fly from a gentler slope rather than a steep one.
- If you're flying from a cliff top, be very confident about the conditions before you throw your glider off the cliff and out over the sea.
Slope soaring is indeed great fun, and given the simplicity of rc gliders is very rewarding. You don't need lots of accessories with a glider either, and given the right conditions you can make a flight last for a very long time because there are no recharging or refueling issues.
It's my personal favourite way of enjoying some good rc flying, and I highly recommend it!