8GlidingObjectives:List and describe the Forces acting on Glider duringbalanced flight.State the effect of Wind on the distance travelledover the ground.Explain the effects of Airbrakes on Glide Performance.Understand the ‘Gliding Angle’ (Angle of Attack).
9The GliderPreviously we looked at the balance of forces acting on a powered aircraft (Chapter 1 & 2)Now we will be looking at a glider, which only has three forces acting, LIFT, WEIGHT and DRAG.The only way to maintain airspeed in a glider is to remain slightly “nose-down”.This uses the pull of gravity to drag the glider forwards.The forces on a glider can be balanced also, just like in a powered aircraft, and the glider can maintain its straight and level flight this way.
10The Balance of ForcesAs has been mentioned, the glider has only three forces acting: LIFT, WEIGHT & DRAGThey balance as shown:As you can see, the glide is slightly nose down to maintain airspeed.The speed is generated by the pull of gravity downwards on the weight of the aircraft
11SpeedJust as a bike can “coast” down a hill without being peddled, a glider can “glide” forwards without an engine.In order to keep going (and avoid the stall) the pilot puts the nose of the glider slightly down.To increase speed, the nose is reduced further, and vice versa for decreasing the speed.Since there is no engine, and the glider is always nose down, it is continually descending, hence most gliders cannot stay airborne all day.
12How Far Can It Go?The distance a glider can travel is related to its height and gliding angle.The higher the glider is, and the shallower the angle, the longer it can stay aloft for.A high glider with a deep angle may not be able to glide as far as a low glider with a very shallow angle.The “Lift/Drag” ratio also affects the distance a glider can travel. This will be optimum at a particular angle, which will differ from glider to glider by design differences. This information will be available in the Pilot’s Notes.
13How Far Can It Go?Most modern gliders are quite efficient, and hence have a very good “Lift:Drag” ratio and optimum gliding angle.The ATC’s Gliders, the Viking has a gliding angle of 1 in 35, so for every 1metre up, it can glide 35 metres in still air.Example: if the glider was 1km (1000metres) up, it could glide for 35km before landing.
15Effect of the WindThe wind direction relative to the glider flight path will have an effect.If travelling downwind (i.e. in the same direction as the wind) the glider will travel further than id it is travelling upwind (towards the wind).The wind slows down the aircraft going upwind, hence more nose down angle is required to maintain airspeed, hence the glide angle is increased, and the glider will be able to cover less ground before it touches down.
16Effect of the WindExample: A glider travelling at 35kts into a head wind also of 35kts will appear not to move forwards, but instead stay in one place and descend.
17Air Brakes Gliders do not have flaps as powered aircraft do. Instead they make use of air brakes to have the same effect.These are deployed from the upper and lower of the wings to interrupt the airflow over the wing surfaces.The airbrakes are deployed by the pilot on landing, and cause a huge increase in the drag on the glider.
18Air BrakesThis means a deeper angle is needed to being the glider in, hence it looses more height faster.This allows the glider to land in a much smaller space, as we have said, a Viking at 1m would require 35m of runway in order to land, and that’s without the distance to slow down!
20GlidingObjectives:List and describe the Forces acting on Glider duringbalanced flight.State the effect of Wind on the distance travelledover the ground.Explain the effects of Airbrakes on Glide Performance.Understand the ‘Gliding Angle’ (Angle of Attack).
21Questions Name the Forces Acting on a Glider in Normal Flight. a. Force, Weight and Lift.b. Drag, Weight and Thrust.Drag, Weight and Lift.Drag, Thrust and Lift.
22Questions How does a Glider Pilot Increase the Airspeed? a. Operate the Airbrakes.b. Lower the Nose by pushing the Stick Forward.Raise the Nose by pulling the Stick Back.Lower the Nose by pulling the Stick Back.
23QuestionsA Viking Glider with a glide ratio of 1:35 descends from 1640 ft (0.5 km).How far over the ground does it Travel (in still air)?a kms.b. 35 kms.70 kms.8.75 kms.
24Questions When flying into a Headwind, the distance covered over the ground will:a. Be the same.b. Decrease.Increase.Take you to Burger King.