In the previous article I explored possible cross-country routes, possible distances flown and managing controlled airspace in the southern Romanian flatlands. In this article I summarize my experience of flying in the flats: how to do safe and efficient takeoffs on a payout winch, how to thermal in the flats, and how to fly cross-country.
There are two main types of winches in paragliding: pay-in and pay-out winches. Pay-in winches are stationary devices. A helper pulls out something like 1000-2000 metres of line, the pilot hooks up to this line, and the winch pays in (pulls) the line while towing the pilot up in the air. Payout winches work the other way. They are mounted in a car (or boat, quad or some other vehicle). A short (around 50 m) line is payed out. The pilot hooks up to the end of the line, lifts and stabilizes the wing above his/her head, and the car starts moving while paying out the line with a certain brake pressure applied to it. We used payout winches in the flatlands, so I will explore this option further below.
Payout Winch Takeoff
What do you need? On the winch-side of the line you need:
- A ~2 km long straight road with no or very little traffic, and no trees, power lines or buildings for the line to fall on them
- A car with sufficient off-road capabilities to drive on this road at a speed of up to 45-50 kmh (worse roads require more rugged cars).
- A payout winch, which is sufficiently automated to be operated by the car driver
- A driver/winch operator; he can also drive you to the takeoff, tow you and then retrieve the car/pilots.
The pilot needs:
- The most important requirement for the pilot are proper ground-handling skills. You need to be able to handle the wing in zero wind, cross-wind, strong wind, whatever the conditions are; stabilize it above your head; give the start signal to the driver; and take off pulled by the line synchronized with the car/winch operator. All these scenarios require good ground-handling skills.
- A tow release is the only equipment you need in addition to hill launch.
- Good communication with the driver. We use headsets and a mobile call with the driver for takeoff. Radio communication is also required for release because the phone call usually cuts out above 500m AGL.
Risks at Towing
The major risk is messing up the launch process, because at launch you are close to the ground, and any incident can quickly escalate into something very bad. I had a close call when once in a hurry I hooked up the tow release somehow asymmetrically (or the tow release got caught in my cockpit, not really sure). At launch, the release pulled the right riser far more than the left one, and I started flying at 45 degrees to the tow line to the left and gaining very little height instead of following the car and going up. I had precisely 2-3 seconds from launch to pull the release before being pulled out from below the glider and hit the ground hard. I pulled the release just in time, but I came very close to a serious accident. The best way to avoid any major surprises at takeoff is to apply brake pressure on the tow line slowly and gradually (the brake pressure starts pulling the glider up in the air).
After takeoff, the only major concern of the pilot is keeping the glider perpendicular to the tow line (if the wing is facing a different direction than the tow line, the pilot can be pulled out from under the wing and nasty things can happen again). Use mostly weight shifting and little brake inputs; use the brakes as little as possible (not to stall the glider).
Disclaimer: I am far from being an expert in cross-country flying, but I like to reason and write about flying. In this article I present my personal strategy and ideas that I use to fly in the flatlands. The section on flying fast and efficiently should be written by someone else though. I fly rather slow.
In my experience, if the day is good, it is best to take off starting from 11 am to 12:30 pm. This is the first booming period of the day, when the first decent cumulus clouds form and you can expect to climb well. If the day is slow, and the lapse rate is rather bad, the first good climbs are usually possible at around 3 pm.
After Releasing the Line
In the first climb, I try to recognize the pattern of the day: the wind direction and strength at different altitudes (how much I drifted while thermalling). Every few minutes I check my ground speed for an entire 360 turn. I also pay attention to possible altitude levels with weak lift or disorganized thermals (wind shear or inversion); in which direction I had to extend my circles at a given altitude level to center/find the core; how clouds evolved around me and above me while I was climbing (cloud cycles). After the first thermal, I usually have a first strategy whether I should follow clouds or the ground (sunlit regions, thermal sources and triggers); which clouds to go to; if it is worth to go to nice fat clouds or rather aim for the small fluffy stuff. This pattern generally holds up for the first hour or two of flight.
As the day passes and as I cover some distance, the conditions may change, but the inversion levels, thermalling strategy and cloud cycles/patterns remain the same for some time. The next challenge is observing how the day and conditions change and adapting my strategy to these changes. Generally things are pretty fast and easy from 11 am to 1:30 pm.
Then there is often a period of 30 minutes to one hour of weak lift, and fuzzy clouds. In this period your only option is to slow down, be patient and try to stay up. You simply core every weak lift you can find, don’t go on long glides with speed, and don’t give up fighting to stay up until you have actually landed.
If there was a thermal lunch break and you survived this period, you are generally rewarded with a few hours of booming conditions, strong thermals and reliable lift. How long this lasts depends on the number of daylight hours (22nd of June being the longest day) and the quality of the air. Now you can fly fast, only take the strong stuff and use as much speed as possible.
If there was no overdevelopment in the booming period, the last part of the day brings weak but steady lift, and nice orange colours in the sky. You need to slow down again, and you can cover an additional 10-30 kms just by patiently circling in the weak lift and drifting with the wind until the day ends completely. This part of the day feels the most rewarding and relaxing: just do your circles in the 0-1 m/s lift and drift with the wind.
Using the Wind
Flatland flying requires a pretty different strategy than flying in the mountains. With no ridges, peaks and valleys to define thermals, wind has a much more important effect on how you should fly. You need around 20 kmh wind to fly efficiently in the flats. With 20 kmh wind, you cover distance with a constant speed of 20 kmh even if you don’t go on a glide. The maximum wind speed for safe flying is somewhere around 35 kmh at ground level. With stronger wind, the wind determines where you go; you have fewer options to choose a landing place when getting low, so you can be blown into villages, cables or trees. Flying cross-wind to avoid areas of controlled airspace, towns/villages or lakes gets more difficult.
Due to the strong wind, thermals tend to be organized in bands along the wind direction, so after climbing high, the best option is usually gliding directly downward to find the next lift.
In case of weak to no wind, you may need to fly in a zigzag pattern to cover the best thermal sources or to follow the clouds scattered all over the area. Flying triangles in the flats is more difficult than in the mountains, because there are no mountains (especially ridges) to organize thermals in bands.
When looking for thermals, you can follow the clouds or the ground or a combination of these two. Clouds have a different lifecycle every day and this can even change every few hours, so it is best to find the pattern that applies to your day and period of the day. There are days when you will find a good thermal under every cloud you go to. On other days big fat clouds never have a good thermal under them and you should rather go to the young and weak clouds or even out in the blue. It all depends on the day and the patterns you found.
With every climb, try to understand the patterns that worked at that time, and try to apply them for your next move. Obviously, you also need to recognize any changes in the day; adapt to it, and refine your strategy instead of blindly applying what worked in the previous hour or day.
When following the ground, look for sunshine, thermal sources, triggers and the wind. Plan your route to cover as many good possible sources of thermal as possible. It is all statistics: if you fly over many good thermal sources, you will eventually bump into one. The key is looking for contrast. If everything is covered with snow, you may find a thermal above a wetland with liquid water. So look for the hottest, driest, darkest and bushiest fields. These are my main criteria for selecting good thermal sources, in this order: the field must be in the sun and be the driest of all, it should be dark in colour and should have vegetation (grass, wheat, rape seed, bushes). Villages are usually good thermal sources too. If there is wind, the thermal is triggered at the downwind end of this field, where there is a good trigger. With weak to no wind, thermals may get triggered right in the middle of the field.
Triggers can be anything, which give the strongest contrast in the area. A trigger can be the border between a dry and a wet field, a tree line, a tractor, a road, a river, a ridge. The terrain feature giving the strongest contrast is usually the best trigger if it is close enough to a thermal source.
In one flight I followed a 50 m high ridge in the flats for 40 km from Giurgiu towards Calarasi. It was set exactly in the direction of the wind and it gave a reliable thermal just like a ridge in the Alps. There I learned the idea of looking for contrast. If everything is flat, even a 50 m high ridge can give reliable thermals.
Please share your stories and ideas about flying in the flatlands in the comments below! Your ideas will help others and telling them will even help you reasoning about them and becoming a better pilot.