Project-1: Powertrain for aircraft in runways
1. Aircrafts are classified on basis of their design and powered system
Types of aircraft based on the design:
1. Aerodyne - Any hevier thean air machine that derives greater lift from its aerodynamics
2. Aerostat - Any lighter than air carrying craft is a aerostat. Eg; Balloon
Types of aircraft base on powered system:
1. Propelled Aircraft - The aircraft with a propulsion system which helps aircraft to move against airflow.
2. Unpropelled Aircraft - Aircraft do not have any propulsion system and moves with the flow of wind and its structural dynamics.
Weight of different aircrafts
1. Airliner - 60,000 kg (Weight of plane and its fuel tank)
2. Airship - 1600kg (unfilled)
3. Amhibian (able to land in water as well) - 1044kg
4. Autogyro - 450kg
5. Freighter - 80,000kg
6. Biplane (Two sets of wings one above another) - 500kg
7. Bomber - 83,250kg
8. Canard - 700kg
9. Drone - 5kg to 200kg
10. Helicopter - 6000kg - 20,000kg
2. Ground speed - a referene point is selected on the ground. When the aircraft moves, the velocity of aicraft relative to that reference point is called ground speed. When aircraft takes off the ground speed is completely equal to zero. The ground speed is always acting in the horizontal direction. when the aircraft starts to change its orientation to vertical the ground speed starts becoming zero.
Airspeed - It is the speed relative between the aircraft and air when aircraft is in the position to lift itself from ground. The airspeed is computed from ground speed and wind speed. Airspedd is vector difference between ground speed and wind speed.
Airspeed = ground speed - wind speed
On a perfectly still day, the airspeed is equal to the ground speed. But if the wind is blowing in the same direction that the aircraft is moving, the airspeed will be less than the ground speed.
3. On ground the movement of aircraft is done to move it from one place to another. Genarally it is done by the towing vehicle or the a group of people. This movement of aircraft is called taxing. The vehicle with a speed of 30 - 35km/hr. The aircraft are mostly attached with jet engines which produces a huge amount of power and force. The engine geerates a thrust force in hundreds of kN which can cause damage on the ground. The speed required is to just move from one point to another wich will be at a maximum distance of 1km.
Hence to cover this distance using aurcraft engine will be wrong choice. Hence it is not recommended to use aircraft engine for making the aircraft movement on the ground.
4. The aircraft moves from terminal to the runway with its own engine power. But at the initia point at the terminal it is not recommended for aircrafts or it is restricted to switch on their jet engines due to the possibility of the damage. As the thrust required is obtained from the propeller of the jet engine which produces lot of power and heat. Hence the towing vehicles pushes back the aircraft before they can start their own engines to take off.
5.
1. Take off power - take off power is the power required to lift aircraft from the ground. This power is derived from the thrust required to lift the aircraft. Take off power is never a maximum engine power. Maximu power affects engine life due to wear of an engine. The airline generally prefer low power take offs. Occasionally, a condition such as high ambient temperature (resulting in high pressure altitude), heavy load, obstacle on departure path may demand a max power takeoff. Possible wind shear may also prompt the crew to select a higher takeoff power.
2. Tyre Design
Tyre is important component when it comes to safety of an aircraft and the passengers in it. It helpd to absorb shocks during landing and provide friction to reduce speed. An aircraft tyre is designed to withstand extremely heavy loads while landing, take off, taxing and parking. The number of wheels required for aircraft increases with the weight of the aircraft, as the weight of the aeroplane needs to be distributed more evenly.
Unlike an automobile or truck tyre, it does not have to carry a load for a long period of continuous operation. However, an aircraft tyre absorbs the high impact loads of landing and also it’s operating at high speeds for a short time when required.
Some tecnical aspects considered while design of tyres
Load Rating – Load rating is the maximum permissible load at a specified inflation pressure.
Ply Rating – Ply Rating is used to identify the maximum recommended load rating and inflation pressure for a specified tyre. It is an index of tyre strength.
Speed Rating – The speed rating is the maximum takeoff speed to which the tyre has been tested.
Skid Depth – Skid depth is the distance between the tread surface and the deepest groove as measured in the mould.
Aircraft tyres must have an approved speed and load rating and have sufficient clearance when retracted through landing gear to allow for tyre growth. Tyre growth is the increase in the size of the tyre due to centrifugal forces at high speed.
3. Tyre Pressure - Aircraft tyres operate at high pressures of magnitude 200 psi.
Large aircraft tires are filled with nitrogen not air. Air is a combination of gasses that at low atmospheric temperatures and pressure can turn to ice inside the tires or under high temperatures and pressures even explode. Nitrogen is an inert gas meaning that it does not react chemically with rubber and does not support combustion. Nitrogen is the much safer choice to fill aircraft tires.
As per the survey it is known that aircraft tyres lose 5% of the pressure per day for the routine operation.
4. Brake forces when Landing - Bringing at aircraft down to the runway from 37,000 feet is only part of the challenge. It’s not over until the aircraft is safely parked at its gate. In order to do this, pilots have a number of systems available to slow the aircraft down, even in a blizzard on a snow-covered runway.
Stopping aircraft landing at a high speed requires a huge braking force. To do this the barke units are powered by hydraulic systems. The electrical signal is sent from flight deck to hydraulic actuators near the main landing gear. Here, hydraulic fluid at 3,000 pound per square inch is used to force the brake unit against the wheel, thus slowing it down.
his system works fine, but the pipes and actuators that form this part of the hydraulic system come at a considerable weight cost. Extra weight means more fuel burn, which in turn increases costs and carbon emissions.
To avoid the above situation hydraulic brakes are replaced with electric brakes. When the pilots press on the brake pedals, an electrical signal is sent to the brake unit on the wheel. Here, electrically powered actuators are used to press the carbon brake disc against the wheel, slowing it down.