Thermals for Gliders - Epic Clouds

Gliders are a relaxing and natural way to fly. Here is some background information on what to expect and how to maximise thermal lift.

What Are Thermals?

In certain conditions heated air can build up over particular ground features. The air can form bubbles or streams of warm air that rise and eventually release heat and vapour to form clouds. The clouds and thermals move downwind over time, so the thermals are normally rising diagonally over the terrain.

The strength of the thermals depends on:

The latitude – a temperate zone works well
The altitude – choose a low altitude airport to start
The season – summer is best
The time of day – noon is best

To maximise lift, choose mid-summer, mid-day, and a low altitude airport.

The thermal presets have been tuned for the AS-33ME with full water ballast at mid summer and mid day at Stigler Regional Airport (KGZL) in central America. At that location, its possible to go to 10,000 ft on a thermal updraft, however, in France at Challes-les-Eaux (LFLE) it is difficult to reach half that altitude.

How to Find a Thermal

To meet the thermal at your current altitude, either start at the source and fly downwind to the cloud or start at the cloud and fly upwind to the source.

When you find some lift, you will want to maximise the amount you can get by performing a circling search pattern. Experienced pilots suggest adjusting the size and position of the turning circle but not changing the direction of the circle. If you are using the AS-33me glider, click on the Al / Therm button to reveal a plan view of your relative altitude over time. Use the green feedback to locate the best lift available.

Wind Visualisation

The flight sim can show you where active thermals are: open the weather dialog box from the in-sim toolbar then enable the checkbox on the bottom-right hand side. You will now be able to see blue trails moving upward from hotspots on the ground. The trails are for general guidance but do not accurately show how the wind is moving. You can find the strongest thermals by looking for the highest reaching, and thickest collection of blue lines.

The AS-33me Glider

I recommend the AS-33me glider, it’s a pleasure to fly and has many useful features. Click on the ‘Al / Therm’ button to reveal a colour coded plan view of your relative altitude over time. Use the green feedback to locate the best lift available.

A Guide for New Glider Pilots

I recommend the AS-33ME since it is has excellent and intuitive instruments onboard that will help you track thermals and wind direction.

New pilots can follow these instructions in order to engage with all the available help provided by the AS-33ME.

Preferably select the AS 33ME glider for your first flight, and leave it with full water ballast. If you are using a lighter aircraft, you can decrease the strength of the thermals as described in the overview.
Select the tow plane as your means of reaching altitude. If one isn’t available, waggle the rudder to call one.
Select airport KGZL (Stigler Regional Airport) in central USA; the terrain is flat, making it perfect for concentrating on thermal lift. It is at 599 feet (183 m) above mean sea level so the air is more dense than airports in the hills and mountains.
Load the flight and the flaps lever will be set to A for Aerotow (if you are using the AS-33ME).
Set the month of the year to June (the summer month in the flight location).
Set the time of day to noon since this preset is tuned to the maximum thermal energy at that time.
For extra help on your first flight, switch on the wind visualisation at the bottom left of the presets dialogue box.
Move your rudder left and right twice to indicate to the tow plane pilot you are ready to go.
When you lift off, retract the wheel.
During the tow, keep the tow plane visible and in position just above the cockpit rim, following it gently as it turns.
Release the tow rope when the tow plane moves its wings up and down several times.
Move the flaps lever to T2 for maximum thermal lift (if you are using the AS-33ME) potentially adding in a small amount of pitch up to reduce the effort on the stick.
Head for the nearest big cloud, this is where the thermals are most intense.
Follow the wind direction into the centre of the cloud. In theory, the strongest thermals will have made the cloud and pushed it downstream. You will want to be on the upstream edge of the cloud shadow so you can make good use of the increasing lift while you seek the centre of the thermal.
Begin circling when you meet a thermal as indicated by your instruments and variometer. If you do not immediately find a thermal, you should perform a search pattern and double back wherever you find reasonable lift.
Gain a few thousand feet so you can make a long distance run to a new location.
When you begin your flight to a new location switch the flaps to -1 (if you are using the AS-33ME). Adjust the pitch to achieve a smooth, straight flight without the slow undulating motion.
Follow the Arkansas River to the East for some scenic sights. Seek some extra lift at 3000 feet to avoid being trapped in less energetic air at lower altitudes.
Before landing, empty the ballast tanks using the switches on the right of the cockpit (if you are using the AS-33ME).
When starting the landing sequence set the flaps to L for maximum drag (if you are using the AS-33ME), drop the wheel when you are close to the airfield and use the spoilers or side-slip as necessary to achieve the correct glide slope for the runway.