HOW DOES A GLIDER FLY?
WHAT IS A GLIDER? A glider is a light aircraft that is designed to fly without the use of an engine. Gliders are graceful aircraft’s, as some say they are the closest humans can get to soaring like birds.
DIFFRENT TYPES OF GLIDERS
- Paper aeroplane simplest form of gliders made from folded paper.
Hang Glider Fabric aerofoil is stretched over a stream-lined frame and the single pilot is suspended from a harness from the glider airframe. The pilot shifts their body weight to control the flight. Sailplane A lightweight aircraft which has a similar design style to an engine powered aircraft. They are designed to climb efficiently in rising air so can glide for long distances at high speeds.
Space Shuttle Although rocket engines are use during lift off they return to Earth as a glider.
Closer look at a
SAILPLANE
√
WINGS
Gliders have longer, narrower wings than conventional aircraft’s.This allows them to produce more lift and make them more efficient for gliding. Slim wings means the plane cannot carry heavy loads. Similar to conventional air-planes controls, as a single stick between pilot’s legs controls the ailerons and elevators, and the rudder is controlled using foot pedals.
BODY
The body is designed to be lightweight, thin and stream-lined. This shape also allows the aircraft to soar through the air more effiently Modern gliders are made from fibreglass & carbon fibre as these are smoother than other materials such as wood & aluminium.
CONTROL SURFACES
√E
√A
AILERONS
The primary way of cotrolling direction of plane. Deflect up or down to control lift/drag on each side of the wings.
√R
ELEVATORS
Controls piton of plane (points nose of plane up/down).
RUDDER
Controls yaw of plane (point nose of plane left/right)
DESIGN OF THE WING Curved shape of wings means air pressure is lower on top of wings (as the air takes longer to pass over the curve).
Air pressure underneath the wing is higher as it can pass straight under wing
This dynamic creates more lift under wings. As glider wings are longer and narrower they produce more lift efficiently.
GETTING OFF THE GROUND Three basic forces which act on gliders (engine powered planes have a fourth force: thrust):
LIFT
Allows aircraft to stay in the air. Created by wings & counteracting weight.
DRAG
A force of resistance on glider- slows them down. Must be reduced to keep glider in air.
WEIGHT
Although gliders must be lightweight, the heavier they are the greater the speed they travel. Gliders have water tanks which can be emptied or filled to control speed of aircraft.
LAUNCHING METHODS AERO-TOW
Most common launching method.Conventional engine powered plane tows glider in the air using rope. Glider pilot controls quick release of rope when they have reached the desired altitude.
WINCH-LAUNCHING
Engine powers winch on ground. When winch is activated, glider is pulled along the ground towards winch, which generates enough power to lift sailplane in the air. Pilot releases the cable.
AERO-TOW
LIFT DRAG
WINCH-LAUNCHING
WEIGHT
STAYING IN THE AIR GLIDE RATIOS
Tells you how far a glider can travel compared to the altitude it has to drop. Modern gliders can have ratios up to 60:1 (meaning if they start at an altitude of 1 mile, they can glide a distance of 60 miles.
HELP FROM MOTHER NATURE RIDGE LIFT
Created by winds blowing against mountains, hills or other ridges. As air reaches mountain it is redirected upwards & forms a band of lift.
THERMAL LIFT
Air near the ground is heated by the sun and expands and rises. Pilot’s keep an eye out for terrain which absorbs heat rapidly- such as buildings, car-parks and rocky terrain.Cumulus Clouds & birds gliding can also be signs of thermal lift.
DETECTING LIFT
A Variometer on a glider dashboard notifies pilot their rate of climb or descent. Uses static pressure to detect changes in altitude. If glider is rising static pressure drops (as air pressure decreases the higher you go) If glider is sinking static pressure rises.
VARIOMETER
0
WHY WEIGHT MATTERS Heavier gliders sink faster but do so at a higher speed (so glide-ratio is unaffected). And order to glide faster they can hold up to 500 pounds of water.
However, heavier planes have reduced climb rates, therefore if pilot cannot find suitable lifts the flight duration will be reduced. Pilots can drop loads of water through the wings to reduce weight so plane can climb altitude more efficiently (or come in for a slower landing).
HOW IT LANDS! Similar to landing a conventional plane However sailplanes only use a single small wheel located Plane wings are under cockpit. very strong and can handle being dragged along ground during landing.
Tail of plane also has a small wheel to prevent tail from scraping. Gliders deploy spoilers on each wing to reduce lift and increase drag so plane can descend efficiently.
By Harriet and Isabel