4. LESSON 10 - THE GLIDING CIRCUIT
- The purpose of the circuit is to arrive at the final turn in the right place, at a safe height and at the right airspeed
- The circuit is a predictable traffic pattern to distribute the flow of incoming gliders
- To assess circuit position: use angle (height and distance) to the landing area. If wrong, correct without delay
A safe landing starts with correct planning of the circuit. There may be special considerations at some airfields but normally the standard circuit pattern works for a landing anywhere. It is designed to be flexible and to allow for making corrections and variations at any time, whilst keeping within the basic circuit plan. A circuit consist of several ‘legs.’ Adhering to the circuit contributes to a safe landing.
PRE-CIRCUIT CHECKS
Before starting your circuit you should form the habit of doing pre-circuit checks, to prepare the glider (and yourself, mentally) for landing. That way, your glider will be correctly configured for landing and you can concentrate on flying the circuit. The standard BGA pre-circuit check is WULF (Water ballast, Undercarriage, Loose articles, Flaps, see Lesson 4.3). It doesn’t much matter what checklist you use, and some pilots prefer their own; the important thing is that you always do a methodical check. Of course, when deciding where to land you will also have to consider the wind speed and direction, other landing aircraft, the approach speed needed today, and so on.
The illustration shows what a circuit should look like. First you line up to join the circuit and fly parallel to your landing run (downwind leg). You have to make sure that there is sufficient space between your glider and the other gliders joining the circuit. Circuits can get very busy; it is therefore very important to keep a good lookout.
HIGH KEY AREA
Depending on the local conditions and the wind, we start on a down- wind leg at a height of about 800ft. (You’ll soon learn about the difference between height = above landing area, and altitude = above sea level). From this point on we no longer look at the altimeter.
Instead, we make all adjustments by looking at the angle (height and distance) to a reference point that we chose within our landing area.
The area where we enter the downwind leg is called the high ‘key’ area.
THE DOWNWIND LEG
On this first leg we make final preparations for the landing. If required, make a radio call and continue your thorough lookout for others in the circuit and on the airfield. The downwind leg is a convenient time to select and trim for the approach speed.
It is important to frequently estimate your angle (height and distance) to your landing area. As you descend around the circuit you should aim to keep approximately the same angle. If the angle is too flat you need to move in closer; if it’s too steep, you need to move out until it looks about right. As soon as you notice that your angle doesn’t look right, make a correction. The earlier you do it, the easier it is. On windy days the correct angle is quite steep and on calmer days flatter.
There are no instruments to tell you this angle to your landing area, but with practice you will soon learn to estimate it. Avoid staring at your reference point, but do remember to fly normal, coordinated turns and, above all else, prioritise lookout.
LOW KEY AREA
When we come abeam our reference point we are at the low key area; next comes the diagonal leg. The turn should be about 45° but is flexible; the main goal is to reach the final turn at the correct height and distance from the landing area. Continue to use the angle looking down to the reference point to make your judgement. If it looks a bit flat then turn more than 45° to bring yourself closer; if too steep then make a smaller turn, taking you further back from the landing area. Remember you are flying down-wind and if the wind is strong you will be moving away from your airfield quickly.
DIAGONAL LEG
During this leg you can use the same angle to the reference point to make adjustments and to decide when to turn onto the base leg.
BASE LEG
The goal of the base leg is to reach the final turn at the right angle (height and distance) towards the landing area that will allow you to fly the final approach with half to two-thirds airbrake.
While you are on the base leg you need to look ahead for traffic approaching on an opposite circuit and away from the airfield for traffic on long final. You can still make some angle adjustments during this leg, perhaps even with airbrakes. In general, it’s better not to use airbrakes during the final turn; you may lose a lot more height or speed than you intended. Concentrate on making a reasonably coordinated turn.
CIRCUIT PLANNING
In a circuit, the height, distance and angle to your landing area should be correct. If not, make active corrections. If too high and too close, move out of the circuit until the angle is correct. If too low and too far away, move in.
NON STANDARD CIRCUITS
One day, you may find yourself out of position to fly a standard circuit. In Lesson 4.33 we will practice how to approach the airfield and how to land from an unfamiliar angle and altitude. We will not describe this in more detail here.
