Project-1: Powertrain for aircraft in runways

AIM:Powertrain for aircraft in runaways

Objective:

PART A:

1)Introduction:

An aircraft is a vehicle that is able to fly by gaining support from the air.it countries the force of gravity by using either static lift or by using the dynamic lift of an airfoil,or in a few cases the downward thruust from jet engines.

There are many factors that lead to efficient and safe operation of aircraft.Among these vital factors are proper weights and balance control.The maximum allowable weight for an aircraft is determined by design considerations.The manufacturer provides the aircraft operator with the empty weight of the aircraft and the location of its empty weight center of gravity(EWCG)at the time the certified aircraft leaves the factory.

However the maximum operational weight may be less than the maximum allowable weight due to such considerations as high-density attitude or high-drag field conditions caused by wet gross or water on the runway.The maximum operational weight may also be limited by the departure or arrivalairports runway length.

MANUFATURERS DESIGN WEIGHT LIMITATIONS:

The maximum allowable weight for an aircraft is dtermined by design considerations by the aircrafts manufaturer.However,the maximum operational weight may be less than the maximum allowable weight due to such considerations as high-density attitude or high-drag field conditions caused by wet grass or water on the runaway.The maximum operational weight may also be limited by the departure or arrival airports runaway length.The structural weight limits are based on aircraft maximum structural capability and define the envelop for the CG charts.Aircraft srtuctural weight capability is established during aircraft design and certification.

MAXIMUM DESIGN TAXI WEIGHT (MDTW OR MTW):

The maximum design taxi weight or maximum deisgn rramp weight (MDRW)is the maximum certificated design weight for aircraft ground manoeuvres as limitedd by aircraft strength and airworthiness requirements.The difference between the maximum taxi/ramp weight and the maximum take-off weight(maximum taxi fuel allowance)depends on the size of the aircraft,the number of engines,APU operation,and engines/APUfuel consumption,and is typically assumed for 10to15 minutes allowance of taxi and run-up operations.

MAXIMUM DESIGN TAAKEOFF WEIGHT (MDTOW OR MTOW)

The maximum design take off weight is the maximum certified design weight for takeoff run as limited by aircraft strength and airworthiness requirements.

MAXIMU DESIGN LANDING WEIGHT(MDLW OR MLW)

The maximum design landing weight is the maximum certified design weight for landing limited by aircraft strength and airworthiness requirements.it generally depends on the landing gear strength or the landing impact loads on certain parts of the wing structure.

MDLW<MDTOW<MDTW

Maximum Design Zero-Fuel weight (MDZFW)

The maximum design zero-fuel weight is the maximum certificated design weight of the aircraft less all usable fuel and other specified usable agents as limited by aircraft strength and air worthiness reuirements.It is the maximum weight permitted before usable fuel and other specified usable fluids are loaded in specified sections of the airplane.The weight difference between the MDTOW and the MDZFW may be utilized only for the addition of fuel.

Maximum payload=MDZFW-OEW

MINIMUM FLIGHT WEIGHT(MFW)

Minimum certficated weight for flights as limited by aircraft strength and airworthiness requirements.

EFFECTS FLIGHT WEIGHT(MFW)

Some of the problems caused by overloading an aircraft are

• The aircraft will need a higher takeoff speed,which results in a longer takeoff run.
• Both the rate and angle of climb will be reduced.
• The service celling will be lowred.
• The cruising speed will be reduced.
• The cruising range will be shortened.
• Maneuverability will be decreased.
• A landing roll will be required because the landing speed will be higher.
• Excessive loads will be imposed on the structure,especially the landing gear.

DEFINITIONS:

AIRCRAFT GROSS WEIGHT:

The aircraft gross weight is the total aircraft weight at any moment during the flight or ground operation.

The aircraft goes weight decreases during flight due to fuel and oil consumption.The aircraft gross weight may also vary during flight due to payload dropping or in-flight refueling.

MANUFACTURERS EMPTY WEIGHT(MEW)

Lets start with the aircraft itself.An aircraft as is includes:

• Airframe structure with all moving machanical parts(fuselage,wingsflaps,gear,rudder,nacelle..)
• Power generation system (APU,main engines,power plant....)
• Systems (electrical,hydraulics,pneumatic,fuel flow system,instument,navigation,air conditioning.anti-ice fixed furnishing)
• Fixed equipment and services considered an integral part of the aircraft
• Fixed ballast
• closed systemfluids
• Unused fuel onnly for small aircraft

All these items above form the Manufacturers Empty Weight(MEW).

This weight does not include:

• Fuel
• Oil,potable water
• payload(cargo,passenger
• Removable equipment
• Cutomer specific installation or operator items.

OPERATIONAL EMPTY WEIGHT(OEM)

The MEW and the operators items are summed up to the operational Empty weight(OEW).The OEW is uuually fixed for a specific aircraft and only gets changed during maintanance ornoperational changes.OEW is the empty weiht that is used in the flight simulator or the usual planning software.

The operators items are:

• fluids necessary for aircraft operation(engine oil and collant,watr,unusable fuel)
• the water for galleys and lavatories
• aircraft documentation
• passenger seats(and the life vests)
• galley structure
• catering emergency eqiupment
• aircraft crew and their luggage.
• standard items necessary for full operation.

ACTUAL ZERO FUEL WEIGHT(AZFW)

If we add the payload to the empty plane weight,we get the Actual Zero Fuel Wight(AZFW)

The payload includes:

• the passengers weight (the standard weights used defined by ICAO respectively)
• the passengers luggages weight
• the cargo weight

The assumed weights vary arround some kg/lbs.depending on the number of seats available on the aircraft.

• a male passenger(incl.cabin luggage)weigh around 82kg(181 lbs.)
• a female passenger around 67kg
• a child around 50kg(110lbs).
• an infant 16kg(35lbs).

These are stastical values but otherwise one wuold need to weigh every single passenger during check in to get his exact weight.Additional payload consists of baggage and cargo(such as mail or goods).

ACTUAL GROSS WEIGHT(AGW)

In addition to the actual zero fuel weight,we add the fuel required for the flight and we get the Actual Gross Weight(AGW).At that time you should have calculated your total fuel for this flight.The actual gross weight is the weight of aircraft ready for departure at the gate befor push-back and start-up

type

1Liter

1 .U.S. Gallon

1imp.Gallon

Aviation Gas

1.58lb.

6.0lb.

7.20lb

JP-4

1.76lb

6.6lb

8.01lb

Kerosene

1.85lb

7.0lb

8.39lb

Oil

1.95lb

7.5lb

8.5lb

Note 1kg=2.20462262185 lb(s)

The total fuel shall include:

• Taxi-out fuel(at departure airfield)
• Trip fuel
• Holding
• Re- routing expectation
• regulation needs depending on your route arrived airfield
• taxi-in fuel at destination
• final reserve.

TAKE-OFF WEIGHT

Fuel burn taxi operation to the departure runway reduces the gross weight.At the holding point,we have the Actual Take-all weight (ATOW)which is used for take-off performance calculation.

The gross weight varies during flight.Fuel and oil consumption reduces the gross weight.additionally it may vary during flight due tovinfight refuelling or payload dropping.

MAXIMUM DESIGN TAKEOFF WEIGHT(MDTOW)

The maximumtake off weight(also known as the maximum brake-release weight)is the maximum weight authorized at brake release for takeoff,or at the start of the takeoff roll.

The maximum takeoff weight is alwyas less than the maximum taxi/ramp weight to allow for fuel burned during taxi by the engines and the APU.

In operation,the maximum weight for takeoff may be limited to values less than the maximum takeoff weight due to aircraft performance,environmental conditions,airfield characterstics (takeoff field strength,altitude),maximum tire speed and brake

At this weight,the subsequent addition of fuel will not result in the aircraft design strength being exceeded.The weight difference between the MTOW and the MZFW may be utilized only for the addition of fuel.

LANDING WEIGH

withe the calculation of fuel consumption during flight,we can calculate the Estimated Landing Weight (ELW)which is used for landing performance calculation at the destination.

Approaching your destination you use yout current gross weight to determine the find approach speed.The gross weight now is the ACTUAL LANDING WEIGHT(ALW).

of course before landing.you never land without only fuel in reserve.The regulation is strict about fuel calculation for commercial air transportation including reserve fuel.Except in specific situations like re- routing.multiple holding,landing at alternate or technical problems,at landing the aircraft shall still have expected reserve fuel if there was no etra consumption.

EXAMPLE:

Now we will get started and calculate an example(we operate an Airbus A319);

Manufacturers Empty Weight(MEW)

36,779kg

+operators items

+5,205kg

=operational Empty Weight(OEW)

=41,981kg

+Payload

+13,529kg

+Fuel

+13,239kg

=Actual Gross Weight(AGW)

=68,749kg

Fuel consumption

-10,900kg

=Actual Landing Weight(ALW)

=57,749kg

2)DIFFEENCE BETWEEN GROUND SPEED AND AIR SPEED:

Wind speed:

For a reference point picked on the ground,the air moves relative to the reference point at the wind speed.Notice that thw wind speed is a vector quantity and has both a magnitude and a direction.Direction is important.A 20-MPH wind from the west is different from a 20-mph wind from the east.The wind has components in all three primary directions(north-south,east-west,and up-down).In this figure.we are considering only velocities along the aircrafts flight path.A positive velocity is defined to be in the direction of the aircrafts motion.We are neglecting cross winds,which occur perpendicular to the flight path but parallel to the ground,and updrafts and downdrafts,which occur perpendicular to the ground.

Ground speed:

For a reference point picked on the ground,the aircraft moves relative to the reference point at the groound speed.Grounf speed is also a vector quantity so a comparision of the ground speed to thw wind speed must bedone according to rules for vector compatisions.

AirSpeed:

The important quantity in the generation of lift the relative velocity between the object and the air,which is called the air speed,Airspeed cannot be directly measured from a ground position,but must be computed from the ground speed and the wind speed .Air speed is the vector difference between the ground speed and the wind speed.

Airspeed=Ground speed- windspeed

CONCLUSION:

Yes,there is a difference between ground speed and air speed.Ground speed is how fast an airplanes shadow would move across the land.If theres a strong wind pushing an aircraft,thats reflected in the ground speed.Airspeed,in contrast,is how fast an airplane is really flying strictly under its own power.which is calculated by subtracting the wind speed from the ground speed.On a perfectly still day,the aspired 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)Why is it not recommended to use aircraft engine power to move it on the ground at airport:

The Risk to Operational safety:

The risks which may arise from engine gound running relate to the potential for loss of control of the aircraft by those persons occupying the pilot seats in the flight deck.In most cases,such persons will be maintanance personnel holding specific company-issued approval for the required tasks.The consequences of loss of control during taxi ortowing are the same as apply to these operations generally and this article is concerned only with the risks arising from the static running of one or more aircraft engines.Unwanted consequences from such static running are mainly related to those arising from the unintended movement of the aircraft during engine running-effectively a loss of control-especially during high power engine running.Damage can occur to the aicraft itself,other aircrafft nearby or to airside structures.In addition,there is risk of injury to ground support personnel who may be in relatively close proximity to the aircraft.

Reasons for not using aircraft engine power to move it on the ground at Airport:

• Usage of high power mounted engines have high risk of blasting.
• Usage of low power mounted engines have a risk of impurities on the ground may enter inside the engine.
• High fuel cost since aerplanes uses large amount of power.

4)How an aircraft is pushed to runaway when its ready to take off:

TAXIING:is the movement of an aircraft on the grounf,under its own power,in contrast

to towing or pushback where the aircraft is moved by a tug.The aircraft usually moves on wheels,but the term also includes aircrsft with skills or floats(for water-based travel).

A pushback truck lifts the front wheel of the aircraft.their role in most airports is to move the aircraft away from the parking spot on to the taxiways.Here the truck is removed and when all platform.staff is out of the way the engines are started one by one.From here on the aircraft moves on its own power to the runway.In the aircraft you will hear the engine spinning up when power is demanded for acceleration.

An airplane uses taxiways to taxi from one place on an airport to another ;for example,when moving from a hangar to the runaway.The term "taxiing"is not used for the accelarating run along a runway prior to takeoff,or the decelerating run immediately after landing,which are called the takeoff roll and landing,which are called the takeoff roll and landing rollout,respectively.

5)Learning about take off power,tyre design,rolling resistance,tyre pressure,brake forces when landing:

a)take off power:

Takeoff is the phase of flight in which an aerospace vehicle leaves the ground and becomes airborne.For aircraft traveling vertically,this is known as liftoff.For aircraft that take off hrizontally,this usually involves starting with a transition from moving along the ground on a runway.For light aircraft,usually full power is used during take off Large transport category(airliner)aircraft may use a reduced power for takeoff,where less than full power is applied in order prolong engine life,reduce maintenance costs and reduce noise emissions.

After taxiing onto the runway,the airplane should be carefully aligned with the intended takeoff direction,and the nose wheel positioned straight,or centered.After releasing the brakes,the throttle should be advanced smoothly and continuously to takeoff power.An abrupt applicationof power may cause the airplane to yaw sharply to the left because of the torque effects of the engine and propoller.This will be most apparant in high horsepower engines.As the airplane starts to roll forward, the pilot should assure both feet are on the rudder pedals so that the toes or balls of the feet are on the rudder positions,not on the brake portions.

Take off performance can be predicted by using a simple measure

of Acceleration of the aircraft among the runway based on force equilibrium.

The force involved will be

T-Thrust of propulsion system pushing aircraft along runway.

D-Areodynamic Drag vehicle resisting the aircraft motion.

F-Rolling resistance friction due to the contact of wheels of skids on the ground.During take-off run the imbalance in these forces will produce on acceleration along the runway.

DV/dt = (T-D-F)/m

where dV/dt is the acceleration along the runway and m is the mass of the vehicle.

b)Tyre Design:

When it comes to safety,Tyres are one of the most important components of aircraft.They help to absorb the shock of landing and providing cushioning.It also provides the necessary traction for braking and stopping of an aircraft.An aircraft Tyre is designed to withstand extremely heavy loads whilelanding,takeoff,taxiing,and parking.The number of wheels require for aircraft increases with the weight of the aircraft,as the weight of the aero plane needs to be distributed more evnly.

Carcass piles are used to form the tire.They are sometimes called casing plies.An aircraft Tyre is constructed for the purpose it serves.

• They support the weight of an aircraft while it is on the ground.
• It also provides the necessary tracion for braking and stopping of aero plane.
• Tyre also helps to absorb the shock of landing and provide cushioning the roughness of takeoff,roll-out,and taxi operations.
• Unlike an automobile or truck Tyre it doed not have to carry a load fora long period of continuous operation.However,an aircraft Tyre absorbs the high impact loads of landing,and also,its operating at high sped=eds for a short time when required.

c)Rolling Resitance:Rolling resistance,sometimes called rolling friction or rolling drag,is the force resisting the motion when a body (such as a ball,tire,or wheels))rolls on a surface.It is mainly caused by non-elastic effects;that is ,not all the energy needed for deformation(or movement)of the wheels,roadbed,etc,is recovered when the pressure is removed.Two forms of this are hystersis losses and permanant (plastic)deformation of the object or the surface(e.g soil)Note that the slippage between the wheel and the surface also results in energy dissipation.Although some researchers have included this term in rolling restistance,some suggest that this dissipation term should be treated separately fom rollin resistance because it is due to the applied torque to the wheel and the resultant slip between the wheel and ground,which is called slip loss or slip resistance in addition,only the so-called slip resistance involves friction,therefoe the name"rolling friction"is to an extent a misnomer.

The rolling resistant coefficient is defined by the following euation

F=CrrN

where

F =Rolling resistance force

Crr=dimensionless rolling resistance coefficient or coefficient of rolling friction(CRF)

N=Normal force,the force perpendicular to the surface on which the wheel is rolling.

Crr Surface

0.001-0.0025 steel wheels on steel rails

0.0015-0.0025 bicycle tires

0.006-0.01 Truck tire on asphalt

0.01-0.0015 ordinary car tires on concrete

0.03 car tires on tar or asphalt

0.2-0.4 car tire on loose land

Tyre Pressure:

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.Aircraft tires generally operate at high pressures,up to 200 psi (14bar;1400kpa)for airliners,and evn higher for business jets.The main landing gear on the concorde was typically inflated to 232 psi(16.0 bar),whilst its tail bumper gear tireswhere as high as 294 psi(20.3 bar).

d)Brake Forces:

In aircraft types,the brake units are powered by the hydraulic system.An electrical signal is sent from the flight deck to hydraulic actators nea the main landing gear.Here,hydraulc fluid at3000 pound per square inch is used to force the brake unit against the wheels,

Part b:

6)A calculating the force and power required to push/pull an aircraft by a towing vehicle:

The forces required to push/pull an aircraft by a towing are rolling resistance force and areodynamic drag forcre .

1)Roling resitance force:As we have dicussed in part -A 5c.it is the force resisting the motion when a body (such as a ball,tire,or wheel)rolls on a surface its governing equation is given as

F=Crr*N

F=Crr*m*g

where

Crr= Rolling resistance coefficient

m=mass of the body

g=acceleratopn due to gravity

2)Aerodynamic Drag Force:

It is the force opposing the motion of the body.The drag coefficient is a common measure in automotive design as it pertains to aerodynamics.Drag is aforce that acts parallel to and in the same direction as the airflow.The drag coefficient of an automobile measures the way the automobile passes through the surrounding air.When automobile companies design a new vehicle,they take into considereration the automobile drag coefficient in addition to the other performance characterstics.Aerodynamics drag increases with the square of speed;therefore it becomes critically important at higher speeds.Reducing the drag coefficient in an automobile improves the performance of the vechicle as it pertains to speed and fuel efficiency.The governing equation of these force is given as following

Fd=1/2`rho`v^2CdA

where

Fd=drag force

rho=mass density of the air

v=flow velocity relative to theobject

Cd=drag coefficient

A=reference area

CALCULATION:

let us assume that,

mass of Towing vehicle=40000kg

Mass of aircraft=155,000kg

Total mass(m)=40000+155,000=195,000kg

Frontal Area of the aircraft(A)=18 m^2

speed of the vehicle(v)=25kmph

converting it into m/sec

v= 25*(1000/3600)=6.9445m/sec

Drag coefficient (Cd)=0.75

Air density(rho)=1.225kg/m^3

Calculating Rolling resistance Force

Frr=Crr*m*g

=0.01*195,0009.8

=19,110N

calculating Aerodynamics Drag Force

Fd=0.5*rho*Cd*A*V^2

=0.5*1.225*18*0.75*(6.9445)^2

=398.769N

Therefore the total Force required to push/pull the aircraft by the towing vehicle(F)=Frr+Fd

=19,110+398.769

=19,508.769N

Calculating power(p)=

Force*velocity=1958.769*6.9445=135.478kw

B.DEVELOPING THE MODEL FOR THE CALCULATED FORCE AND POWER USING SIMULINK:

Blocks Used:

1)Constant

2)Sum

3)Product

4)Square

5)Display

Explanation:

In order to understand the above simulink model we do reverse engineering.

• For calculating power we have to multiply both total force(F)and velocity inm/sec for this we have used product block(P=F*V)
• For calculating the Total Force(F)we have added both Frr Fd by using 'sum' block as shown in the figure
• To find the value of rolling resistance(Frr)we used product to mass(m)*gravity (g)which are to be entered in the'constant block'.
• Similarly for calculating Drag force(Fd)we have to multiply the velocity in m/sec,Drag coefficient,Frontal area of aircraft (A)and a constant value 0.5 which are to be entered in constant block.
• In order to convert velocity in kmph to m/sec we have multiplied with 5/18.

7)A.Based on the calculations done in 6A.

Force required to push/pull the aircraft =19.508KN

Power required =135.478kw

let us assume,

The radius of the Tyre for the Tug=25inches=0.635m

Gear ratio=8

Transmission Efficiency(etat)=87%

Motor Efficiency(etam)=95%

then,

Torque required for the wheels

(Tw)=Totalforce*Radius in meters

=19.508*0.635=12.38KNm

Mtor Torque=Wheel torque/(Gear ratio*etat)

=12.387/(8*0.7)=1.778Nm

For etam=95%The required motor Torque (Tm)=1.778/0.65=1.871kNm

Similarly The Total power required by the motor considering all the efficiencies(Pt)=

=135.478/(0.87*0.95)=163.917kw

Let us assume the towing operation was done for a 15 minutes (0.25hrs)duration.

Then Total Energy consumed=16.917*0.25=40.98kwh

If we consider (d)=(Required power)/(Rated powerr)=163.917/220=0.75

Therefore the controller will be able to provide a duty cycle ranging from 0to 75%in order to control the following speed.

Power Converter:

A converter is an electrical circuit which accepts a DC input and generates a DC output of a different voltage,usually achieved by high frequency switching action employing inductive and capacitive filter elements.A power converter is an electrical circuit that changes the electric energy from one from into the desired from optimised for the specific load.A converter may do one or more functions and give an output that differs fom the input.It is used to increase or decrease the magnitude of the input voltage,invert polarity,or produce several output voltages of either the same polarity,or mixed polarities such as in the computer power supply unit.

The DCtoDC converters are used in a wide range of application including computer power supplies,board level power conversion and regulation ,dc motor control circuits and much more.The converter acts as the link or the transforming stage between the power source and the power supply output.There are several kings of converters based on the source input voltage and the output voltage and these falls into four categories namely the AC to DC converter known as the rectifier,the AC to AC clycloconverter or frquency changer.

POWERTRAIN:

Powertrain test rings can now be built to be capable of using either the engine as the prime mover,or an electric motor simulating the engine.The evolution of such cells has been made possible by the comparatively recent development of permanant magnet motors(PWMS)and their associated controls in the automotive power ranges.These units are capable of engine simulation including that of most driveline dynamics and combustion pulses.The same motor technology has produced dynamometers having low inertia capable of absorbing high torque at low speeds,thus providing road wheel load simulation that,with customized controllers,include tire stiffness and wheel slip simulation .An important logistical justification for such all- electric powertrain cells, besides not having to install and maintain all the cell services required by running an IC engine,is that the require engine may not be available at the time of the transmission test.One cost-effective arrangement that suffers from similar logistical problems of unit availability but whuch overcomes several rig design problems,where a complete (Dummy or modified production)vehicle is mounted within either a two-wheel "four-squre powertrain test.