Introduction to Gliding

Gliding involves flying through the air without the assistance of an engine. In order to stay in the air, and gain height, the pilot flies within pockets of air that are rising faster than the aircraft is descending.

The sport of gliding consists of racing gliders around ‘tasks’ (race circuits involving taking the glider to various locations out of gliding range of the airfield), and aerobatics competitions (where pilots perform a number of aerial manoeuvres and are scored on how well the manoeuvres are performed).

This section will give you a brief introduction to how gliders are controlled, launched and how they stay in the air.

Controlling a glider

Gliders are controlled by moving a number of ‘control surfaces’. These ‘control surfaces’ change the airflow over parts of the glider causing it to move. The control surfaces are connected to controls in the cockpit – primarily a stick and a pair of pedals.

Ailerons:

Located on the rear edge of the wing, the ailerons ‘roll’ the glider. Moving the stick to the left causes the left wing to drop and the right wing to rise (a roll to the left), moving the stick to the right causes the right wing to drop and the left wing to rise (a roll to the right). The ailerons are used to turn the glider.

Elevator:

The elevator causes the glider to ‘pitch’. Pulling the stick towards you causes the nose to rise and tail to drop, and pushing the stick away from you causes the nose to drop and the tail to rise. The elevator is used to control the speed of the glider, to increase/decrease the rate of descent, and to make turns tighter.

Rudder:

Located at the rear of the fin, the rudder causes the glider to ‘yaw’. Pushing the left pedal moves the nose to the left, and pushing the right pedal moves the nose to the right. The rudder is used to ‘co-ordinate’ turns.

Airbrakes:

Located in the upper, and sometimes lower, surface of the wing, the airbrakes are stored inside the wing, and are raised or lowered (via a leaver in the cockpit) to control the rate of descent. Pulling the leaver towards you raises the brakes, increasing the rate of descent. The airbrakes are primarily used on landing to allow a precise touch-down.

Launching a Glider

A glider cannot take-off on its own, so it must be helped in to air.At Wittering, gliders are launched by two methods: winch and aero-tow.

Winch:

To launch, a glider is attached to a long steel cable that is connected to a drum which is rotated at high speed by a large (at Wittering) diesel or LPG engine. As the cable is wound in, the glider is pulled along the ground until it reaches a fast enough speed to take-off and climb. Using this method the glider reaches a height of 1500 to 2000ft (and quite often higher!) in about 30 seconds. This is a fast and cheap way of launching gliders, and is the most common at Wittering.

Aero-Tow:

In this method, the glider is attached via a rope to a powered aircraft and pulled into the air (like a car pulling a trailer). At Wittering a SuperFalke is used as the tug aircraft. This method is gentler, slower and more expensive than the winch, but allows a launch to any height and location.

How does a Glider stay up?

A glider stays in the air by flying within rising air. If the air is rising faster than the glider is moving downwards, then the glider will climb and potentially rise thousands of feet (imagine trying to walk down an escalator that is moving upwards!). There are three main sources of lift:

Thermals:

Thermals are rising pockets of air caused by the heating of air by the Sun, and are the predominant form of lift used by glider pilots. To make use of thermals a glider is flown into the rising air, where the pilot then circles the aircraft to keep in the lift until the desired height is achieved. Thermals are often marked by fluffy cumulus clouds.

Ridge Lift:

Wind meeting the side of a mountain or hill is forced upwards in order to flow past the obstruction, so gliders can fly along the windward slide of the slope in the lift generated by the wind.

Wave:

Wave is produced by wind meeting the side of a hill/mountain producing a standing wave behind the hill. This wave can extend for several miles behind the obstruction and consists of alternating lines of rising and descending air. A pilot can gain height by flying along one of the lines of rising air.