Project-1: Powertrain for aircraft in runways
PROJECT:1 Powertrain For Aircraft In Runways
PART A:
- Search and list out the total weight of various types of aircrafts.
- Is there any difference between ground speed and air speed?
- Why is it not recommended to use aircraft engine power to move it on the ground at Airport?
- How is an aircraft pushed to the runway when it's ready to take off?
- Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when Landing.
Objective:1 Search and list out the total weight of various types of aircrafts.
Solution: The aircraft gross weight (also known as the all-up weight and abbreviated AUW) is the total aircraft weight at any moment during the flight or ground operation.
An aircraft's gross weight will decrease during a flight due to fuel and oil consumption. An aircraft's gross weight may also vary during a flight due to payload dropping or in-flight refueling.
At the moment of releasing its brakes, the gross weight of an aircraft is equal to its takeoff weight. During flight, an aircraft's gross weight is referred to as the en-route weight or in-flight weight.
- Weight of a Male person= 88kg
- Weight of a Female person= 70kg
- Weight of a Children (2-12) yrs= 35kg
- Weight of a Cabin Crew= 75kg
- Weight of fuel in aircraft can be approx 12000kgs for 4000km Payload-Passenger,Cargo,Mail,Baggage.
Let's discuss about the weight of a aircraft one by one:
Maximum design taxi weight (MDTW)
The maximum design taxi weight (also known as the maximum design ramp weight (MDRW)) is the maximum weight certificated for aircraft maneuvering on the ground (taxiing or towing) as limited by aircraft strength and airworthiness requirements.
Maximum design takeoff weight (MDTOW)
Is the maximum certificated design weight when the brakes are released for takeoff and is the greatest weight for which compliance with the relevant structural and engineering requirements has been demonstrated by the manufacturer.
Maximum design landing weight (MDLW)
The maximum certificated design weight at which the aircraft meets the appropriate landing certification requirements. It generally depends on the landing gear strength or the landing impact loads on certain parts of the wing structure.
The MDLW must not exceed the MDTOW.
Maximum design zero-fuel weight (MZFW)
The maximum certificated design weight of the aircraft less all usable fuel and other specified usable agents (engine injection fluid, and other consumable propulsion agents).
All up Weight(AUP): It can be written as DOW+ Payload Fuel
Following table shows the different types of Aircrafts weights.
Where MTOW= Maximum Take Off Weight and MLW= Maximum Landing Weight.
Objective: 2 Is there any difference between ground speed and air speed.
Solution: Ground speed is the horizontal speed of an aircraft relative to the Earth’s surface. It is vital for accurate navigation that the pilot has an estimate of the ground speed that will be achieved during each leg of a flight.
An aircraft diving vertically would have a ground speed of zero. Information displayed to passengers through the entertainment system of airline aircraft usually gives the aircraft ground speed rather than airspeed.
Ground speed can be determined by the vector sum of the aircraft's true airspeed and the current wind speed and direction; a headwind subtracts from the ground speed, while a tailwind adds to it. Winds at other angles to the heading will have components of either headwind or tailwind as well as a crosswind component.
Airspeed is the vector difference between the ground speed and the 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.
Air Speed= Ground Speed - Wind Speed
On a perfectly still day Airspeed is equal to Ground speed.
Difference between Ground Speed and Air Speed:Ground speed is the airplane’s speed relative to the surface of the Earth. Airspeed – is its speed relative to the air it is flying in.Airspeed is what determines whether there is enough airflow around an aircraft to make it fly, Ground speed is what determines how fast an aircraft will get to its destination.If there is no wind at all, then both the aircraft’s airspeed and ground speed would be the same 500 miles per hour, and the aircraft would reach its destination in four hours.Ground speed is easily and accurately determined by the GPS. Air speed is more complicated as it cannot be calculated by sensor sata. What we get is indicated airspeed
Objective3: Why is it not recommended to use aircraft engine power to move it on the ground at Airport.
Solution: Although many aircrafts are capable of moving in backward using reverse thrust, as result the jet blast or prop wash might cause damage to the terminal building or equipment. Engines close to ground may also blow sand and debris forward and then suck them into the engine, causing damage to the engine.
The risk may arise from the engine ground running relate to the potential for loss of control of the aircraft by those persons occupying the pilot seats in the flight deck.Unwanted consequences from such static running are mainly related to those arising from the movement of the aircraft engine running-effectively loss of control especially during high power engine running.
The noise generated from aircraft is also very dangerous for the passengers and people living around them.
Hence it is not recommended to use engine power to move on ground.
Risk to Operational Safety:
The best form of overall mitigation is to ensure that all persons authorized to supervise or directly participate in engine ground from the flight deck, who are not pilots but flight engineers currently rated on the special aircraft type.
Objective: 4 How is an aircraft pushed to the runway when it's ready to take off.
Solution: The airplane may be pushed or pulled by landing gear or wing struts since they're known to be strong enough to drag the airplane through the air. To allow for turns, a person may either pick up or push down on the tail to raise either the nose wheel or tail wheel off the ground, then rotate the airplane by hand.
Procedure:
The pilot parks the aircraft in exactly the right place. Usually with the help of an automatic system, but occasionally guided by a marshaller waving two paddles or wands. Dozens of handling personnel are already standing by to perform a whole range of tasks simultaneously.
As soon as the aircraft is stationary and the engines are switched off, the first priority is to disembark the passengers as quickly as possible. The apron handler places chocks in front of the wheels and connects the ground power. Meanwhile, the passenger bridge maneuvers up to the door and a belt loader rolls up to the cargo hold. Luggage is unloaded and transferred to the terminal on baggage carts.
Refueling begins, usually from a hydrant at the stand. A hose is attached to this from a special vehicle called a dispenser, with the other side connected to the fuel tank in the wing. Read more about refueling here.
Meanwhile, specialists from the airline conduct a technical check to make sure that the engines, wings, control surfaces, landing gear, instruments, doors and other equipment are in full working order.
The aircraft is now ready for baggage to be loaded for the next flight. This is a quick process, on average taking only 10-15 minutes. A little later the passengers start boarding. As soon as they are all in their seats, the door is closed and the pilot informs air-traffic control that the flight is ready for departure.
The apron handler removes the chocks. A so-called pushback truck reverses the aircraft into taxiing position, pushing it with a tow bar attached to the nose-wheel strut. Or, in the most modern versions, by actually lifting the wheel. That speeds up coupling and decoupling.The aircraft taxis to the runway to depart at the agreed time.
Objective: 5 Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when Landing.
Solution:
Take off power: for light aircraft, usually full power is used during takeoff. Large transport category (airliner) aircraft may use a reduced power for takeoff, where less than full power is applied in order to prolong engine life, reduce maintenance costs and reduce noise emissions. In some emergency cases, the power used can then be increased to increase the aircraft's performance. Before takeoff, the engines, particularly piston engines, are routinely run up at high power to check for engine-related problems
The nose is raised to a nominal 5°–15° nose up pitch attitude to increase lift from the wings and effect liftoff. For most aircraft, attempting a takeoff without a pitch-up would require cruise speeds while still on the runway.
Tyre Design: An aircraft tire or tyre is designed to withstand extremely heavy loads for short durations The number of tires required for aircraft increases with the weight of the aircraft, as the weight of the airplane needs to be distributed more evenly. Aircraft tire tread patterns are designed to facilitate stability in high crosswind conditions, to channel water away to prevent hydroplaning, and for braking effect.
Aircraft tires also include fusible plugs (which are assembled on the inside of the wheels), designed to melt at a certain temperature. Tires often overheat if maximum braking is applied during an aborted takeoff or an emergency landing
Dimensions and Sizing
Dimensional classification is usually made according to outer tire diameter, sectional width, and the diameter of the rim. A common classification system in use today is that of the United States Tire and Rim Association.
Construction
A tire follows a layered construction approach where each layer (region) of the tire serves a different purpose. Broadly speaking, a tire can be divided into four specific regions: the bead, ply, tread and sidewall.
Refer to the image below which shows the make-up of a typical aviation tire.
Bead
The bead consists of bundles of high strength steel wire encased in rubber. This provides the tire with lateral strength, anchoring the structural plies and transferring the impact loads generated in the tire onto the wheel rim.
Ply Region
A tire is built from multiple plies which are laid on top of each-other to give the tire its structure and form. Plies are usually manufactured from nylon fabric sandwiched between layers of rubber. These structural members are sometimes called carcass plies as they form the skeleton of the tire. The concept of ply rating refers to the relative strength of the tire’s ply layup. The ends of each ply are anchored to the beading on each side of the tire to transfer load out the tire and into the wheel.
Tread
The tread refers to the wearable part of the tire that is designed to come into contract with the ground. The tread is located on the tire crown and must resist frictional wear, abrasion, cracking and cuts
Rolling Resistance:
Rolling resistance is the combination of forces that work against the forward motion of your vehicle. The weight of the vehicle, gravity and inertia, the amount of friction between the tires and the road surface, and air drag all play a part. When you coast in your car or on a bike, rolling resistance is what slows you down. The more rolling resistance, the more power it takes to propel a vehicle. Between 3 and 11 percent of the gas used in passenger vehicles goes to overcoming this force, so reducing it means saving on gas.
Since tires contribute to between 15 and 25 percent of a vehicle’s overall rolling resistance — depending on how fast you’re going, vehicle type and road surface — they are a significant factor in gas economy.
- Tyre Pressure: Car tyre pressure is a measurement of how much air is in your pneumatic tyre, and ensures the tyres wear evenly and maintain the correct level of grip on the road surface. This is commonly expressed as PSI, or pounds-per-square-inch.
Tyre manufacturers have recommended tyre pressures, and car manufacturers actually have a placard (or tyre pressure chart) on all new cars showing the correct tyre pressure for the tyres the car came with.
Driving with too low pressure (as when the tyre is flat) means the tyre could roll off the wheel, and will have dangerously soggy handling performance which affects braking in an emergency.
Aircraft tires are usually inflated with nitrogen to minimize expansion and contraction from extreme changes in ambient temperature and pressure experienced during flight Dry nitrogen expands at the same rate as other dry atmospheric gasses (normal air is about 80% nitrogen), but common compressed air sources may contain moisture, which increases the expansion rate with temperature
The requirement that an inert gas, such as nitrogen, be used instead of air for inflation of tires on certain transport category airplanes was prompted by at least three cases in which the oxygen in air-filled tires had combined with volatile gasses given off by a severely overheated tire and exploded upon reaching autoignition temperature. The use of an inert gas for tire inflation eliminates the possibility of tire explosion.
Brake forces when Landing: Aircraft brakes stop a moving aircraft by converting its kinetic energy to heat energy by means of friction between rotating and stationary discs located in brake assemblies in the wheels.
Brakes provide this critical stopping function during landings to enable airplanes to stop within the length of the runway. They also stop aircraft during rejected takeoff events, in which an attempted takeoff is canceled as the airplane is rolling down the runway before it lifts off from the ground due to engine failure, tire blowout, other system failure or direction from air traffic control.
Aircraft brakes also prevent motion of the aircraft when it is parked, limit its speed during taxiing and can even help steer the aircraft on the ground by applying different levels of braking force to the left- and right-side brake.
Develop a Simulink Model: Develop a Simulink Model: Develop a Simulink Model:
Part B:
- A. With necessary assumptions, calculate the force and power required to push / pull an aircraft by a towing vehicle.
- Develop the model for the calculated force and power using Simulink.
- A. Design an electric powertrain with type of motor, its power rating, and energy requirement to fulfill aircraft towing application in Simulink. Estimate the duty cycle range to control the aircraft speed from zero to highest. Make all required assumptions. Prepare a table of assumed parameters. Draw a block diagram of the powertrain.
(Hint :DC7 Block)
- Also, Design the parameters in excel sheet.
Objective:6 A. With necessary assumptions, calculate the force and power required to push / pull an aircraft by a towing vehicle.
- Develop the model for the calculated force and power using Simulink.
Solution: A:According to the challenge we have to calculate the force and power required to push and pull on aircraft by a towing vehicle.
Taking the value of Aircraft 310 specifications are:
Mass= 170000kg
Height= 15.80m
Width= 44.00m
Frontal area A= Height*Width
15.80*44.00=695.2msquare
Drag coefficient Cd=0.0265
Air density = 1.225kg/m square
Taking the value of Towing vehicle TBL280
Mass=40000kg
Height= 2.0m
Width= 3.5m
Frontal area A= Height*Width
2.0*3.5=7m square
Tyre size R=0.5588m
Drag coefficient Cd=0.6
Air density= 1.225kg/m square
Speed v= 32km ph= 32*5/18= 8.89m/s
Now calculate the forces acting on the push and pull
Rolling Resistance Force=Fad
Formula
Frr=urr*m*g
M= mass of the body
urr= coefficient of rolling resistance.
g= gravitation
Fad= ½*p*A*Cd*V^2
p= Air density
A= Frontal area
Cd= Drag Coefficient
V= speed
Coefficient of Rolling Resistance urr=0.02
Rolling resistance force of an aircraft Frr= urr*m*g
Frr= 0.02*170000*9.8
Frr=33320N
Rolling Resistance Force of a Towing vehicle Frr2=urr*m*g
Frr= 0.02*35000*9.8= 39004N
Air drag force of an aircraft Fad=½ *p*A*Cd*v^2
=½*1.225*693.62*0.0265*8.89^2
=889.77N.
Develop a Simulink Model:
In the simulink model I have created a subsystem for both Rolling resistance force and Air Drag force and connected them to an additional block to calculate the total force and take a connection from the output of the additional block connected it to the product block. Speed is also connected to the product block.
Now from above model by opening the subsystem of Rolling resistance force we can see the following connections.Were rolling resistance force is calculated for both aircraft and towing vehicle
The subsystem of AirDrag resistance had the following blocks when we opened it. The upper part of the subsystem is to calculate the AirDrag force of the aircraft and lower part is to calculate the air drag force of the towing vehicle.
ROLLING RESISTANCE SUBSYSTEM
AIR DRAG RESISTANCE SUBSYSTEM
Objective:7. A. Design an electric powertrain with type of motor, its power rating, and energy requirement to fulfill aircraft towing application in Simulink. Estimate the duty cycle range to control the aircraft speed from zero to highest. Make all required assumptions. Prepare a table of assumed parameters. Draw a block diagram of the powertrain.
(Hint :DC7 Block)
SOLUTION: Energy Required
Energy= Power*Time
Power calculated as,
Power= 350.41KW
Time is assumed as 20 minutes which is converter to hours as 0.33h
Time= 0.45h
Now
Energy= 350.41*0.45
Energy= 135.18KWH
Now we have to calculate the input power to the duty cycle of the towing vehicle.
Duty Cycle= Power output/Power input
Input voltage=650V
Input Current= 600A
Power input= Input Voltage*Input Current
Power Input= 650*600=390000W
Power Input= 390KW
Duty Cycle= Power output/Power input
Duty Cycle=350.41/390
Duty Cycle=90%
The duty cycle required for Towing the vehicle is 90%
The Table Represent the assumed Parameters:
Parameters Value
Aircraft
Mass 174000kg
Height 16.80m
Width 45.90m
Air density 1.225 kg/m^3
Towing Vehicle
Mass 35000kg
Height 2.0m
Width 3.7m
Tyre Size 0.5560m
The following figure represent the Block diagram of Powertrain:
When the battery is to supply the DC voltage to the Converter. The converter gives the required voltage to the controller and the motor is controlled by the controlled block. The output of the motor is given to the transmission system. It is linked to the brakes, wheels and load. We have to design a electric powertrain with type of motor, its power rating and energy requirement to fulfill aircraft towing application.
Here AC to DC converter is used because we have taken input as AC so we need to convert it into DC.We have taken supply voltage as 380V. Convert them into DC supply as we are using DC drives. The converter output gives value to the DC7 block which gives value to the selector block.
The resultant plot is shown in the given below graph:
Here we can see the plot for duty cycle, Armature current, Armature voltage, Motor current. Motor reaches its highest voltage and current, Speed then becomes constant and then start decreasing.
Design the Parameters in Excel Sheet:
