Gliders : An Aerodynamics Mastermind
Aeroplanes, Helicopters, Rockets, and Jet planes are a few of a wide array of machines that fly across our daily sky. These mechanical megastructures require tremendous amounts of energy to travel and maintain an altitude many thousand feet above the Earth’s surface. Propulsion, powered by fuel, does the work of providing energy to the system simultaneously due to which these machines can stay in the sky for a particular amount of time.
The propulsion system burns a lot of fuel during the flight which results in plenty of CO2 emissions. Nevertheless, to date, no such commercial aircraft that produces zero Carbon Emissions is made by humankind. Non-stop research and technological developments in the aerospace sector can only lower Carbon Emissions but cannot eradicate them. However, there exists a type of Aircraft that does not even have an engine within its framework.
What are Gliders?
A long-winged, lightweight and compact machine, Glider, is a type of aircraft where there exists no propulsion system. Consequently, this makes it a Zero Emission Aircraft (during flight) with minimal design complexities.
Originally gliders were made of abundantly available materials like wood and metals. Propulsion completely depends upon the design characteristics and weight of an Aircraft. This is why gliders are fabricated with lightweight materials. Nowadays, composite materials and 3D printed parts with calculated infill amount and type are used to manufacture a Glider. As a result, production cost increases but a good flight and durability of the Aircraft is ensured.
Gliders have a high Aspect Ratio that makes their wings longer than their complete width of wings. The average aspect ratio of a glider is 6:1, i.e. the wings are six times longer than the chord length. However, this ratio is variable and it depends upon the gliders flying capabilities. A high aspect ratio provides more lift (altitude) whereas a low aspect ratio makes the aircraft easily manoeuvrable. Aspect and Glide Ratio will be briefed in the following sections.
Gliders require towing to take off. It consists of another aircraft attached to a glider that cruises it to an altitude with some speed after which a glider can perform. Gliders can also take off from the gradients of a mountain which in turn makes them Zero Carbon Emission Aircraft.
A glider has a very compact cockpit. The pilot sits in a way similar to how an F1 driver seats in his vehicle. Cockpits are designed in such a way that their surface area is minimum which reduces drag induced due to pressure. Generally, cockpits have a single seat but nowadays, 2 seated gliders are also famous. Three major instruments are seen in every glider; an Altimeter, a compass and an airspeed indicator.
An Altimeter is used to indicate the altitude of the aircraft. Altitude is generally denoted in feet. Modern gliders are equipped with GPS, however, a compass is also installed for navigation purposes. An Airspeed Indicator (ASI) is used to indicate the airspeed of an aircraft. In aviation, the Airspeed unit is generally knots.
1 knot = 1.852 km/hr.
The main body of any aircraft is the fuselage. The fuselage acts as a connection between the wings and tail of the aircraft to the main body. Gliders have a significantly narrow fuselage to minimise the surface area. The fuselage is the home of the cockpit and the avionics module of the aircraft. It is made up of Aluminium Steel, Composite Materials or Kevlar material. Unlike other giant aircraft, where the surface of the body is supposed to induce turbulence, the fuselage of a glider has a smooth body. This ensures that it slips through the air easily and reduces induced drag.
Wings on an aircraft are divided into various components. Each component has a unique purpose and way of operation. These components are operated in unison to achieve lift, decrease speed or maneuver the aircraft. The nautical terms, Port and Starboard are used to classify left and right side wings respectively. (facing front)
Flaps are located in the inner part of the wing near the fuselage. Flaps are used to increase drag, lift or the descent rate. The design of flaps is dependent upon the type of glider and use case. A slight change in the orientation of flaps can alter the amount of drag and lift in significant amounts.
Ailerons cover the trailing edge of a wing. Primarily ailerons control the rolling motion of an aircraft. Ailerons always move in the opposite direction during their operation. When a right turn is desired the aileron on the right wing displaces in an upward motion. Consequently, the aileron on the left wing moves downwards. The combined effect of these two components maneuvers the aircraft accordingly.
c. Air Brakes
To reduce speed in an aircraft, the drag force must be increased. In gliders, Air brakes create additional drag force as a result speed is decreased. When air brakes are applied, the surface area of the glider against the airflow increases. This results in a pressure difference zone behind the brake’s cross-section. As a result glide ratio decreases at a fast pace and a lower speed is achieved.
The whole tail module, containing the fixed Vertical Stabilizer (Fin), Horizontal Stabilizer (Tailplane), Rudder and Elevator comes under the Empennage. Analogous to wings, these elements have distinctive features and maneuvers the aircraft in a united functioning.
The Rudder is a single component mounted on the rear end of the vertical stabilizer. It controls the yaw movement of the aircraft by altering the direction of airflow.
Elevators are similar to ailerons which are mounted behind the tailplane. It controls the movement about the lateral axis, which in other words it is known as pitch. Elevators are a necessary element of a glider as it controls the angle of attack. The angle of attack is a significant factor in aerospace engineering because the rate of lift generated is controlled by it.
Gliders need assistance for takeoff. This is can be done in multiple ways. One of the most convenient ways of takeoff is towing. In this method, another aircraft is attached to the glider and it tows it through a runway to a certain altitude. After reaching the optimal altitude and speed, the towing aircraft detaches from the glider.
The optimal height of the glider decides the glide ratio. The glide ratio is the ratio of the altitude of the aircraft to the total horizontal distance it can glide. Gliders have a huge glide ratio that ranges up to 70:1. This means at an altitude of 1 kilometre, a glider can glide horizontally for 70 kilometres.
Gliders have the ability to gain height during flight. There are two common ways for a glider to gain altitude.
Thermals are the most common way to gain altitude. Some areas on the Earths surface heat up causing the surrounding air to rise into atmosphere. Such regions are called air pockets or thermals. Gliders revolve around such pockets to gain altitude. Birds such as owls and hawks also follow the same technique to elevate.
The wind rising across the slopes of mountains and hills are used by gliders to rise higher. These wind occurrences are called updrafts. Gliders can sail right above the apex of mountains to gain height without revolving in a pattern. This is the prime advantage of updrafts.
All information and images provided in this article are represented as per my knowledge and information gathering. The information/results should not be used in real-life applications without the guidance of an expert. The scope of this article is limited as a project for students.