Project-1: Powertrain for aircraft in runways

                                                               Part A

1.Search and list out the total weight of various types of aircrafts. 

Different Weights or Masses. For each flight, the weight are taken into account for Several Reasons

Manufacturer's empty weight(MEW):

• Also called Manufacturer's Weight Empty (MWE) or Licensed Empty Weight
• It is the weight of the aircraft "as built" and includes the weight of the structure, power plant, furnishings, installations, systems and other equipment that are considered an integral part of an aircraft.
• This excludes any baggage, passengers, or usable fuel

Zero-Fuel Weight(ZFW):

• This is the total weight of the airplane and all its contents (including unusable fuel), but excluding the total weight of the usable fuel on board.
• As a flight progresses and fuel is consumed, the total weight of the airplane reduces, but the ZFW remains constant.
• Maximum zero fuel weight (MZFW) is the maximum weight allowed before usable fuel and other specified usable agents (engine injection fluid, and other consumable propulsion agents) are loaded.

Operating empty weight(OEW):

• Roughly equivalent to basic empty weight on light aircraft.
• It is the basic weight of an aircraft including the crew, all fluids necessary for operation such as engine oil, engine coolant, water, unusable fuel and all operator items and equipment required for flight but excluding usable fuel and the payload.

Payload:

• It is the carrying capacity of an aircraft. It includes cargo, people, extra fuel. In the case of a commercial airliner, it may refer only to revenue-generating cargo or paying passengers.

Maximum takeoff Weight(MTOW)

• This is the maximum weight at which the pilot of the aircraft is allowed to attempt to take off.

Regulated takeoff Weight(RTOW)

• Depending on different factors (e.g. flap setting, altitude, air temperature, length of runway), RTOW or maximum permissible takeoff weight varies for each takeoff. It can never be higher than MTOW.

Maximum landing weight(MLW)

• This maximum weight at which an aircraft is permitted to land.The MLW must not exceed the MTOW

Maximum ramp weight(MRW)

• It also called maximum taxi weight (MTW)
• It is the maximum weight authorized for maneuvering (taxiing or towing) an aircraft on the ground.

                            

Aircraft gross weight:

• It is the total aircraft weight at any moment during the flight or ground operation. This decreases during flight due to fuel and oil consumption

Let us list out the MTOW and MLW of few notable aircrafts:

Airbus A340-500	371,950	240
Airbus A340-600	367,400	256
Airbus A340-1000	308,000	233.5
Airbus A340-900	270,000	175
Airbus A220-300	59,000	20.80
Antonov An-225	640,000	591.7
Boeing727-200	78,000	68.1
Boeing 737-700	70,000	58.06
Boeing747-400	396,900	295.742
Concorde	185,000	111.1

More such weight can be found from the below link:

https://en.wikipedia.org/wiki/List_of_airliners_by_maximum_takeoff_weight

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2. Is there any difference between ground speed and air speed?

                        

Wind Speed:

        The air moves relative to the reference point at the wind speed.It is a Vector quantity and has both a magnitude and a direction.In this figure, we are considering only velocities along the aircraft's flight path. A positive Velocity is defined to be in the direction of the aircraft's motion. Which occur perpendicular to the flight path but parallel to the ground and updrafts and downdrafts, which occur perpendicular to the ground.

Ground Speed:

• The is the actual speed of the aircraft over the ground and is the result of the wind’s effect on the aircraft. For example, it the aircraft is flying at 100 knots into a 10 knot headwind, the Ground Speed is 90 knots. Ground Speed is used to help determine the aircraft “Estimated Time Enroute;” how long it is estimated to take to reach the destination.
• For a reference point picked on the ground, the aircraft moves relative to the reference point at the ground speed. The Groind speed is also a vector quantity so a comparison of the ground speed to the wind speed must be done according to rules for vector comparisons

AIR SPEED:

       It is simply the speed at which an aircraft is moving relative to the air is flying. It is the Speed at which the air is flowing around the aircraft's wings. There are two types of Air Speed

                                

The AirSpeed Indicated(ASI):

          This is the speed that the aircraft’s “Airspeed Indicator” display and that the pilot uses as a critical reference in piloting the aircraft. It’s a measure of the speed of the airflow over the aircraft’s wings. For example, “Stall Speed” is an Indicated Airspeed reference.

          It measures the speed of an airplane as it moves through the air.It was mentioned earlier that true airspeed (TAS) is the term used for the actual speed of the aircraft relative to the body of air in which it is flying. Unfortunately it is not possible to measure TAS easily. The nearest direct reading available to an aeroplane pilot is the parameter known as indicated air speed (IAS) which is measured by the ASI. The difference between TAS and IAS is caused by changes in air density. The ASI is a pressure-operated instrument. It senses the difference between the total pressure measured at a pitot static tube and the static pressure measured at a ‘static measuring point’, where there is no dynamic component due to air velocity. This principle, and the instrument display. The differential pressure reading is then transferred via a simple geared linkage to the single-pointer display. 

True Air Speed(TAS):

         TAS is Indicated Airspeed adjusted for altitude and non-standard temperature and is theoretically how fast the aircraft would be flying in a no wind condition.

         The true airspeed of an aircraft is the speed for which aircraft relative to the air mass through which it is flying. The true airspeed gives important information on accurate navigation of an aircraft. Traditionally it is measured using an analogue TAS Indicator but as in the GPS has become available for civilian use, the importance of such analogue instruments had been decreased. Since indicated airspeed is a better indicator of power used and lift available, true airspeed is not used for controlling the aircraft during taxiing, takeoff, climb, descent, approach or landing; for these purposes the Indicated airspeed– IAS or KIAS (knots indicated airspeed) – is used. However, it indicated airspeed only shows true speed through the air at standard sea level pressure and temperature, a TAS meter is necessary for navigation purposes at cruising altitude in less dense air. The IAS meter reads very nearly the TAS at lower altitude and at lower speed. On jet airliners the TAS meter is usually hidden at speeds below 200 knots (370 km/h). Neither provides for accurate Speed over the ground, since the surface winds or winds aloft are not taken into account

                                                 Airspeed = Ground Speed - Wind Speed

                                   

Ground Speed:

• The is the actual speed of the aircraft over the ground and is the result of the wind’s effect on the aircraft. For example, it the aircraft is flying at 100 knots into a 10 knot headwind, the Ground Speed is 90 knots. Ground Speed is used to help determine the aircraft “Estimated Time Enroute;” how long it is estimated to take to reach the destination.
• For a reference point picked on the ground, the aircraft moves relative to the reference point at the ground speed. The Groind speed is also a vector quantity so a comparison of the ground speed to the wind speed must be done according to rules for vector comparisons

For reference purpose:

https://www.grc.nasa.gov/www/k-12/airplane/Animation/airrel/anrelg.html

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3. Why is it not recommended to use aircraft engine power to move it on the ground at Airport?

For movement on the ground the aircraft uses it own engine power ,which is called taxing.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. Engine close to ground may also blow sand and debris forward and then suck them into the engine, causing damage to the engine. Therefore these are pushback trucks in the airport. A pushback truck lifts the front wheel of the aircraft, their role is most airports is to move the aircraft away from the parking spot on to the taxiways, Which is called towing.

• Unwanted consequences mainly arising from the unintended movement of the aircraft during engine running.

 

• Effectively a loss of control can happen, especially during high power engine running. Damage can occur to the aircraft nearby or to airsidestructures.

 

• There is a risk of injury to ground support personnel who may be in relatively close proximity to the aircraft.

 

• It is easier for truck driver to see the surrounding better than the pilot sitting in the cockpit with limited window. The pushback driver Knows the airport better than the pilot.

 

• It also saves fuel. Virgin Atlantic's had proposed a new system in which pushback truck will move the aircraft all the way to runway to save fuel and reduce impact on the environment.

 

• The plane engines are very loud. When more than one plane will result to add up their sound, it will not be pleasent for passengers and others near airport.

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 4.How an aircraft is pushed to runway when its ready to take off?

• The Aircraft are usually 'Pushed' by the ground vehicles Known as tow Vehicles such as tow truck. It is used to mainly reverse an airplane from the terminal area, until it is in the position to move by itself. These tow trucks will only help move the aircraft to an area where the pilots can safely switch on the engine, not in the runway. The ground vehicles are rarely allowed to move on a runway (save for emergencies and inspection) and the aircraft is supposed to move to the runway by itself

 

• The Aircraft do not have powered wheels and hence cannot move in reverse (Let alone forward by themselves). Imagine a tiny jet strapped to one of your toy cars, that essentially how airplanes works on the ground. They go where the engine push them towards.

 

• There is a mechanism known as reverse thrusters, which allow the engine air flow to be pushed towards the front, but that is highly risky maneuer, and it is only used to reduce speed immediately after landing.

 

• Another reason to push back an aircraft to a safe area,it for safety reasons. The engines produce tremendous thrust from the exit and an immense vaccum from the front, it enough to small vehicles, ground equipment etc., Hence it is a common procedure to start the engine once it is cleared away from the terminal area and lined up on a taxiway. the roads that lead to the runway.

Simply:

• Airplanes have engines, and they can use them to move forward along the ground. So they push themselves to the runway.
• It is true that most of the time, a small vehicle is needed to push the larger commercial airplanes backwards away from the terminal building, because even if a plane can reverse it’s thrust, it’s not always safe to hit the buildings with that reverse thrust. So the little trucks push the bigger planes back away from the buildings, but after that, the planes can apply a small amount of engine power to roll forward just as all airplanes can.Aircraft push themselves to the runway.

The below chart shows the take off 

                                

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5. Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.

Take off Power:

• The takeoff distance consists of two parts, the ground run and the distance from where the vehicles leaves the ground to until it reaches to 50ft, the Sum of two distance is known as takeoff distance. And the power required to take off the aircraft is known as takeoff power, it is varying with the type of aircraft using. The aircraft can be a light weight and heavy weight aircraft, not only that the takeoff power requirement can change according to the atmosphere condition
• Some condition that influence take off performance would be aircraft weight, temperature, pressure altitude, wind and thrust.
• Full Power take off is just that. The engines are brought to full power and when the aircraft reaches a certain speed (Vto), the aircraft leaves the ground. The crew could also elect to perform a reduced power takeoff. The aircraft charts would be used to determine this power setting.  

 

Tyre design:

Tyres of an aircraft is designed to withstand extremely heavy loads while landing and take off, taxing and parking. The number of wheels required for an aircraft is totally depends on the weight of the aircraft, the count of wheels increases with increases in weight

when it comes to safety, tyres are one of the most important components of aircraft, they help to absorb the shock during the time of landing and providing cushioning. It also provides necessary traction for braking and stopping of an aircraft.An aircraft tyre is constructed for the purpose it serves.

1. It need to support the weight of an aircraft while it is on the ground.
2. Provides the necessary traction for braking and stopping of an aeroplane.
3. Tyre also helps to absorb the shock of landing and provide cushioning the roughness of takeoff, roll-out, and taxi operations.

However, an aircraft tyre absorbs the high impact loads of landing, and also it is operating at high speeds for a short time when required.

Some technical aspects of the tyre.

Retreading – Retreading is methods of restoring a worn tyre by renewing the tread area or by renewing the tread area plus one or both sidewalls. Repairs are included in the tyre retreading process.

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.

 

Tyre Pressure:

• 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.
• The tires are typically inflated to 200 PS
• One thing we almost never see when an airplane lands is a blowout. Think about that: Again and again, the tires hit tarmac at 170 miles per hour and bear the weight of a modest office building. And they nail it. Every time.
• Aircraft tires are amazing when you think about it. The typical airliner tire can handle a 38-ton load. It can meet the ground 500 times before needing a re-tread, a refresh it can take on seven times in its life.
• A Boeing 777 uses 14 tires, Airbus' A380 carries 22, and theenormous Antonov An-225 demands 32. The key to their remarkable durability is maximizing the air pressure, says Lee Bartholomew, lead test engineer for Michelin Aircraft Tires. The high-flying rubber is typically inflated to 200 psi, roughly six times what you put in an automobile tire, and the tires on an F-16 fighter are pumped to 320 psi. It's really pressurized air that's so strong.

 

Rolling Resistance:

• Resistance offered by the tyre during the movement on the ground before taking off, it is known as rolling Resistance.
• When taking off from a runway covered with slush, standing water or snow, the required take-off ground -run distance will be longer than on a dry runaway. This is the result of the fact that slush, standing water and snow on the runway will generate a rolling resistance that increases the total resistance on the aircraft during the ground-run. The Joint Aviation Authorities (JAA) have established aircraft certification and operational rules accounting for runaway surface Condition.

 

Brake force while landing:

• A set Spoiler are raised when the aircraft tyres touch the ground, which decreases the lift generated by the wings during takeoff.The Spoilers some drag which main purpose is to stop the plan from flying.
• Not only the aircraft provided with disk brakes, the aircraft comes to rest due to generation of friction force. The large amount of heat is generated while slowing the vehicle/ rotation of the wheels of an aircraft.

                                                       

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                                                                      Part-B

6. A. With necessary assumptions, calculate the force and power required to push / pull an aircraft by a towing vehicle. 

THEORY:

MASS:

         Mass is a measure of the amount of matter in an object. Mass is usually measured in grams(g) or Kilograms(Kg).

Mass measures the quantity of matter regardless of both its location in the universe and the gravitational force applied to it. An object's mass is constant in all circumstances; Contrast this with its weight, a force that depends on gravity.

 

ROLLING RESISTANCE FORCE:

       Rolling resistance, sometimes called rolling friction or rolling drag, is the force resisting the motion When a body (such as a ball, tire or wheel) rolls on a surface. It is mainly causec by non elastic effects; that is, not all the energy needed for deformation (or movement) of the wheel, roadbed etc.

An formula for rolling resistance force are given below. 

 Frr = μrr * m* g

Where

    μ -varies with speed

    m-Total mass

    g- gravity

 

AERODYNAMIC DRAG FORCE:

The force on an object that resists its motion through a fluid is called drag. When the fluid is a gas like air, it is called aerodynamic drag or air resistance.

                        Fad =1/2* Cd * A * ρ * V²

Where

  Cd- Drag Coefficient

   A - Frontal area m^2

   V - Velocity m/s

   ρ - Air density kg/m^3

 

DRAG COEFFICIENT FORCE:

Any object moving through a fluid experiences drag-the net force in the direction of flow due to pressure and shear stress forces on the surface of the object.

The drag force can be expressed as

 Fd =1/2* Cd * A * ρ * V²

 Where

Cd- Drag Coefficient

Fd - Drag force(N)

A -Characteristic frontal area of the body (m²)

V - Flow Velocity (m/s)

ρ - density of fluid (1.2 kg/m³ for air at NTP)

The drag coefficient is a function of several parameters like shape of the body. Reynolds number for the flow, Froude number, Mach number and Roughness of the Surface.

 

TOTAL TRACTIVE FORCE:

The term tractive effort is often used synonymously with tractive force to describe the pulling or pushing capability of a locomotive. In automotive engineering, the terms are distinctive tractive effort is generally higher than tractive force by the amount of Rolling resistance present and both terms are higher than the amount of drawbar full by the total resistance present(including air resistance and grade).

 Fte = T*G/R

Where

T= Motor Torque

G =Gear ratio

r= Tire radius

So total

Tte = Frr + Fad

 

POWER:

Power is a rate at which work is done or energy is used. It is equal to the amount of work done divided by the time it takes to do the work. The unit of power is the Watt(W), Which is equal to a Joule per second (J/s).

Total Power = Total force * Speed

 

FORMULA USED:

Frr = μrr * m* g

Fad =1/2* Cd * A * ρ * V² 

Tte = Frr + Fad

   The below chart tells the basic information of Airbus A350-1000. From this information We need to calculate force and power required to push / pull an aircraft by a towing vehicle.

                   

Let the

mass of the aircraft (M1)=5,90,000Kg

Rolling Resistance Coefficient of an aircraft tire (µ_rr)=0.004

The Mass of the towing Vehicle (M2) = 50,000 Kg

Rolling Resistance Coefficient of an aircraft tire (µ_rr)=0.001

Rolling Resistance:

Rolling Resistance Force on towing Vehicle =µ_rr* M2*g

                                                              =0.001*5000*9.81

                                                              =49.05N

It is very less as compared to aircraft

Rolling Resistance Force on aircraft=µ_rr* M1*g

                                                  =0.004*590000*9.81

                                                  =23151N

Total Rolling Resistane Force =Rolling Resistance Force on towing Vehicle+Rolling Resistance Force on aircraft                                               

                                          =49.05+23151

                                          =23200N

Total Rolling Resistane Force = 23.2KN   

                                 

Air Drag Force:

Calculation:

The Velocity of the Aircraft while Towing= 25Kmph = 6.94m/s.

Density of Air medium (ϼ)=1.225

The Frontal area of the Aircraft = 20m²

The Coefficient of Drag of the Aircraft = 0.026

Air drag force =0.5*ϼ*A*v^2*Cd

                    =15.34N

The Air drag force of the Aircraft ==0.0153KN

As the Vehicle movea at very low speed Aerodynamic resistance can be neglected and hill climbing resistance too because runway is flat .

Therefore the

total force that the motor needs to overcome=Rolling Resistance of the aircraft+Drag Force Acting on the Aircraft

Total forces Acting = 23.2+0.0153

Total Force that the Motor needs to Overcome in order to Push/Pull the Aircraft = 23.215KN

 

Power Required:

The Power Required by the Motor is given by the Velocity with Which the Towing Operation takes place.

The average speed of Push/Pull = 20Kmph = 5.5m/s

Power required by the motor= Total Force* Velocity = 23.63*5.5

Power Required by the motor=127.7Kw

 

Torque output of the towing Aircraft can also be calculated by the below steps:

         F_te=T.G/r

where 

F_te=Total Tractive Force(Rolling resistance Force + Air drag Force)

T=Torque Output

r=Radius of Tire

G=Gear Ratio

For Heavy Duty Towing we Assume,

G =11 (for delivering high torque)

r =25inches=0.635m

T=F_te.r/G=(23200*0.635)/11

Torque required to Push/Pull for the above stated condition = 1.339 KNm

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B.Develop the model for the calculated force and power using Simulink.

Simulink Model:

                        

• Constant Blocks are used to feed the parameters such as mass, coefficient and other parameters.
• Using product block the resistive force are calculated
• using sum block, the total resistive forces can be calculated.
• The outputs are Visualized using the display blocks.

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 7. A. Design an electric powertrain with type of motor, it’s 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 powertrain. 

(Hint :DC7 Block)

    B. Also, Design the parameters in excel sheet.

Solution:

Battery Pack:

          It is a set of any number of identical batteries or individual battery cells. There may be configured in a series, parallel or a mixture of both to deliver the desired voltage capacity or power density. It gives DC output.

DC-AC Converter:

         DC supply from the battery is converted to AC and is given to motor. Power transfer is managed by Powertrain Electronic Control Unit.

Electric Motor:

         Converts Electrical to Mechanical Energy. Regeneration can be obtained to save Power in many EV's.

On board Charger:

         Converts AC received through charge Port to DC and controls the amount of current into battery Pack.

 

Block Diagram:

 

EV POWERTRAIN:

Motor design: 

for designing the EV Powertrain this are the input are to be considered

Motor is DC motor type

Rated Power= 40Kw

Speed =1400RPM

Rated torque=90 N-m

Efficiency = 90%

 

Power Rating:

Rated Power is 40Kw .

Lets the Input Voltage is 800

Input current is 50

Power Input is V*I

P=800*50

P=40Kw

 

Energy Requirement

Energy reqired for an EV similar to Towing Vehicle Push/Pull the aircraft is Calculated on basis of time

Energy = Power*Time Taken by towing Vehicle to Push/Pull the aircraft

Power=40Kw ----Time is 8 min

Energy=40*8*60

Energy=19200KJ

 

Duty Cycle:

Duty Cycle of Powertrain is calculated by Output Power by the Input Power

Duty cycle = Output Power/Input Power

Duty cycle =36Kw/40Kw

Duty cycle = 0.9=90%

 

Table

Airbus A380-800F

Power generating Source:

Motor	DC motor
Rated Power	40Kw
Speed	1400 rpm
Efficiency	90%
Rated torque	90 N-m

Towing machine Specification that is shown in excel sheet that has been attached below

Entire System:

 

In the above system the Airbus is connected to the towing machine .The forward movement of an aircraft, usually with engines off, using the power of a specialised ground vehicle attached to or supporting the nose landing gear. It may occur for the movement of both in service and out of service aircraft. This will affect the promulgation of procedures and the required qualification for those occupying the flight crew seats on the aircraft during the manoeuvre. and also the engine gets supply from the Four quadrant chopper.

 

Power generating Source:

 

• The DC motor is separately excited with a constant DC field voltage source. The armature voltage is provided by an IGBT converter controlled by two PI regulators.In order to limit the DC bus voltage during dynamic braking mode, a braking chopper has been added between the diode rectifier and the DC7 block.
• In this system we are connected a battery 800V and 50Ah battery to DC 7 Block. We are connected inbetween to Vcc and Ground. Sp is make a constant value to 1400 and the linear load torque is kept 90N-m 
• The first regulator is a speed regulator, followed by a current regulator. The speed regulator outputs the armature current reference (in p.u.) used by the current controller in order to obtain the electromagnetic torque needed to reach the desired speed. The speed reference change rate follows acceleration and deceleration ramps in order to avoid sudden reference changes that could cause armature over-current and destabilize the system.
• The current regulator controls the armature current by computing the appropriate duty ratios of the 5 kHz pulses of the four IGBT devices (Pulse Width Modulation). For proper system behaviour, the instantaneous pulse values of IGBT devices 1 and 4 are opposite to those of IGBT devices 2 and 3. This generates the average armature voltage needed to obtain the desired armature current. In order to limit the amplitude of the current oscillations, a smoothing inductance is placed in series with the armature circuit.

Simulation

Before starting the simulation, set the initial bus voltage

• Start the simulation. You can observe the motor armature voltage and current, the four IGBT pulses and the motor speed on the scope. The current and speed references are also shown.
• The motor is coupled to a linear load, which means that the mechanical torque of the load is proportional to the speed.
• The speed reference is set at 500 rpm at t = 0 s. Observe that the motor speed follows the reference constant accurately (1400) and reaches steady state around t = 1.3 s.
• The armature current follows the current reference very well, with fast response time and small ripples. Notice that the current ripple frequency is 5 kHz.
• At t = 2 s, speed reference remains constant for towing to 1400 rpm. The current reference decreases to reduce the electromagnetic torque and causes the motor to decelerate with the help of the load torque.
• From the below chart we can clearly find out the above information

 

Battery:

The below chart it gives the information about the Current,Voltage and SOC . The battery information is given below

 

Towing System:

Three-Axle Tractor Towing a Three-Axle Trailer