How Gliders Work

CUO Tonya Brown Apr 11

Not talking about this glider...

Allposter.com

Aim

• Learn the basics of how gliders work

• Create a model glider (Squadron Competition)

Introduction

• Glider is an unpowered aircraft• Aerodynamic and piloting factors that apply to

powered airplanes also apply to gliders• Lack of motor changes a lot about how gliders

work• Closest humans get to soaring like a bird

Parts of a Glider

• A glider has many of the same parts as an airplane:– Fuselage– Wings– Control Surfaces– Landing Gear

• But there are significant differences

Fuselage• As small and light as possible• Basically sized around the

cargo they carry (1 or 2 people)• Cockpit of a single-seat glider is small, but

large enough for most• Pilots recline with their legs stretched out in

front of them • Frontal exposure of pilot is reduced and cross-

sectional area of cockpit can be substantially smaller

Howstuffworks.com

• Designed to have skins that are as smooth as possible to allow plane to slip more easily

• Modern gliders – composite construction using materials such as fibreglass and carbon fibre

• Materials allow aircraft designers to create seamless and rivet-less structures, producing less drag

Wings

• Longer and narrower than conventional a/c• Slenderness of wing expressed as aspect ratio

(calculated by dividing the square of the span of the wing by the area of the wing)

• High aspect ratio (long wing compared width)• Drag created during the production of lift

(induced drag) can account for significant portion of drag on glider

Flightglobal.com

Control Surfaces

• Gliders use same control surfaces that are found on conventional aircraft

• Ailerons and elevator controlled using single stick between pilots legs

• Rudder – controlled using foot pedals

Ailerons

• Moveable sections cut on trailing edge of wing• Used as primary directional control and they

control roll of plane• Operate in opposite directions of each side of

the plane• Roll to the right - move control stick to right– Left aileron deflect down (more lift)– Right aileron deflect up (less lift)– Difference in lift causes rotation along axis

Elevator

• Horizontal Stabiliser• Movable wing like structure on the tail• Used to control pitch of plane• Allowing to point nose up/down

Rudder

• Vertical Stabiliser• Wing structure on tail• Control the yaw• Allowing pilot to point nose left/right

Landing Gear

• Reduce size of aircraft by reducing landing gear

• Glider typically consists of a single wheel mounted just below cock pit

Getting off the ground• 3 basic forces act on a glider (they do not have thrust

like airplanes)• Lift – created by wings, counteracting weight– Lift enhanced

• Drag – tends to slow plane down– In motorised thrust overcomes drag, in glider try to reduce

with the design of glider

• Weight – can be made to work for or against– Lighter keeps in air, heavier increases speed– Tanks of water can be used for weight and dumped off

during flight

• Without an engine needs to get up in air by aero-tow

• Conventional powered plane tows glider up in sky using long rope

• Glider takes of before tow plane• When at the desired altitude – release rope

Staying in the air

• Thermals– Columns of air rising by heating of earth surface– Absorbing more sun (asphalt parking lots, dark ploughed

fields, rocky terrain)– Circle within column (gaining height)

• Ridge Lift– Winds blow against mountains/hills/ridges

• Wave Lift– Winds meet mountain – leeward side– Can lift up to thousands of feet high (more than 35000ft)

Hooked-on-rc-planes.com

Landing

• Much like conventional except only single small wheel located directly under the pilot

• Wings are strong and reinforced to prevent damage (usually manage to keep off anyway until slowed sufficiently)

• Spoilers are on each wing - disrupting airflow drastically reducing lift

Glider World Records

• Absolute Altitude: 49, 009ft• Speed over 100km triangular course:

217.4km/h• Free distance: 1460.8 km• Distance around triangular course: 1399.4 km

Make a Model Straw Glider

• Refer to Activity Sheet