Project-1: Powertrain for aircraft in runways

PART-A

1) Typical Airplane Weights:-

Aircraft	Empty Weight	Max Fuel Weight	Max Cargo Weight	Max Gross Takeoff Weight
Antanov AN-225	628,000 lbs 285,000 kg	661,400 lbs 300,000 kg	417,000 lbs 190,000 kg	1,411,000 lbs 640,000 kg
Airbus A380-800	611,000 lbs 277,000 kg	560,000 lbs 254,000 kg	185,000 lbs 84,000 kg	1,268,000 lbs 575,000 kg
Boeing 747-800	485,300 lbs 220,100 kg	427,400 lbs 194,000 kg	295,000 lbs 134,000 kg	987,000 lbs 447,700 kg
Airbus A340-500	370,000 lbs 168,000 kg	386,300 lbs 175,000 kg	119,000 lbs 54,000 kg	820,000 lbs 372,000 kg
Boeing 777-300ER	370,000 lbs 168,000 kg	320,800 lbs 145,500 kg	148,000 lbs 67,100 kg	776,000 lbs 352,000 kg
Boeing 787-10	299,000 lbs 135,500 kg	223,500 lbs 101,500 kg	126,300 lbs 57,300 kg	560,000 lbs 254,000 kg
Boeing 737-900	98,500 lbs 44,700 kg	53,100 lbs 24,000 kg	44,600 lbs 20,200 kg	187,000 lbs 85,000 kg
Airbus A320-100	93,900 lbs 42,600 kg	48,700 lbs 22,100 kg	44,000 lbs 20,000 kg	150,000 lbs 68,000 kg
Embraer 190	63,500 lbs 28,800 kg	28,600 lbs 13,000 kg	28,800 lbs 13,100 kg	106,000 lbs 48,000 kg
Gulfstream G650	54,000 lbs 24,500 kg	48,200 lbs 21,900 kg	6,500 lbs 3,000 kg	100,000 lbs 45,200 kg
Bombardier CRJ900	48,160 lbs 21,850 kg	19,600 lbs 8,900 kg	6,075 lbs 2,760 kg	80,500 lbs 36,500 kg
Bombardier Q400	39,300 lbs 17,800 kg	11,700 lbs 5,300 kg	18,700 lbs 8,500 kg	62,000 lbs 28,000 kg
Learjet 75	13,900 lbs 6,300 kg	6,060 lbs 2,750 kg	2,900 lbs 1,300 kg	21,500 lbs 9,700 kg
Cessna Citation CJ4	10,300 lbs 4,700 kg	5,800 lbs 2,650 kg	2,200 lbs 1,000 kg	17,200 lbs 7,800 kg
Beechcraft King Air B100	7,100 lbs 3,200 kg	3,200 lbs 1,450 kg	4,150 lbs 1,900 kg	12,000 lbs 5,400 kg
Diamond DA50 RG	3,200 lbs 1,450 kg	340 lbs 155 lbs	1,250 lbs 560 kg	4,400 lbs 2,000 kg
Beechcraft Bonanza G36	2,500 lbs 1,150 kg	450 lbs 200 kg	850 lbs 385 kg	3,660 lbs 1,660 kg
Cessna 206H	2,200 lbs 990 kg	520 lbs 235 kg	1,150 lbs 520 kg	3,600 lbs 1,630 kg
Sirrus SR22	2,250 lbs 1,000 kg	485 lbs 220 kg	950 lbs 430 kg	3,600 lbs 1,630 kg
Cessna 172R	1,700 lbs 770 kg	380 lbs 170 kg	560 lbs 255 kg	2,425 lbs 1,100 kg

Aircraft Empty Weight (AEW)

This is sometimes referred to as OEW – Operating Empty Weight and it is the weight of the aircraft with all its equipment on board but no fuel, no passengers or no cargo.

Think of this like the aircraft has just come out of the factory and is sitting waiting to be fueled up for delivery to the customer.

Aircraft Maximum Gross Takeoff Weight (MGTW)

This is the maximum permissible weight the aircraft can weigh as it lifts off the ground at takeoff. This includes the aircraft’s empty weight, the fuel, the crew, the passengers, and all the cargo.

This weight limit is set by the manufacturer and is gospel. Many aircraft accidents have been caused by an aircraft being overweight and the pilot/s have not had enough power or maneuverability to prevent the accident.

Aircraft Useful Load

This is the weight that a pilot can place in the aircraft. Take the MGTW figure and subtract the AEW and this is the total useful load that can be placed into the aircraft. This is the fuel, crew, passengers, and cargo. The bigger the load, the more useful the aircraft can be to its customers!

The Boeing 737 can weigh from 132,000lbs/60,000kg to 187,000lbs/85,000kg at takeoff depending on the model, compared to a small Cessna 172 weighing around 2,400lb/1,11kg. An aircraft’s empty weight, fuel, passengers & cargo must not weigh more than the aircraft’s Maximum Gross Takeoff Weight.

2)There is a difference between ground speed and air speed to understand this we should take into account wind speed too

Wind Speed:-

For a reference point picked on the ground,the air moves relative to the reference point at the wind speed.Notice that the wind speed is a vector quantity and has both a magnitude and a direction. Direction is important. A 20mph wind form the west is different from a 20mph wind form the east. The wind has components in all three primary directions (north-south,east-west and up-down). 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 ground speed. Ground 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:-

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

Air speed=Ground speed-wind speed

On a perfectly still day, the air speed 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) The risk which may arise from 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 unintended movement of the aircraft during engine running-effectively a loss of control especially during high power engine running. Damage can occur to the aircraft itself, other aircraft nearby or to airside structures. In addition, there is a risk of injury to ground support personnel who may be in relatively close proximity to the aircraft.

When modern jet engines are operated at rated thrust levels, the exhaust wake can exceed 375mi/h(325kn or 603km/h) immediately aft of the engine exhaust nozzle. This exhaust flow field extends aft in a rapidly expanding cone, with portions of the flow field contacting and extending aft along the pavement surface. Exhaust velocity components are attenuated with increasing distance from the engine exhaust nozzle. However, an airflow of 300mi/h(260kn or 483km/h) can still be present at the empennage and significsnt people and equipment hazards will persist hundreds of feet beyond this area. At full power. the exhaust wake speed can typically be 150mi/h(130kn or 240km/h)at 200ft(61m) beyond the airplane and 50 to 100mi/h(43 to 88kn or 80 to 161km/h) well beyond this point.

The extensive noise arises from the engine power also dangerous for humans and other living things around the vicinity. Hence for the above reasons it is not recommended to use engine power to move on the ground.

4) In aviation, pushback is an airport procedure during which an aircrafts is pushed backwards away from an airport gate by external power. Pushbacks are carried out by special, low profile vehicles called pushback tractor or tugs.

Although many aircraft are capable of moving themselves backwards on the ground using reverse thrust(a procedure referred to as a powerback), the resulting jetblast or propwash might cause damage to the terminal building or equipment. Engines close to the ground may also blow sand and debris forward and then suck them into the engine, causing damage to the engine. A pushback is therefore the preferred method to move the aircraft away from the gate.

Pushbacks at busy aerodromes are usually subject to ground control clearance to facilitate ground movement on taxiways. once clearance is obtained, the pilot will communicate with the tractor driver(or a ground handler walking alongside the aircraft in some cases) to start the pushback. To communicate, a headset may be connected near the nose gear.

Since the pilots can not see what is behind the aircraft, steering is done by the pushback tractor driver and not by the pilots. Depending on the aircraft type and airline procedure, a bypass pin may be temporarily installed into the nose gear to disconnect it from the aircraft's normal steering mechanism.

Once the pushback is completed, the towbar is disconnected and any bypass pin removed. The ground handler will show the bypass pin to the pilots to make it clear that it has been removed. The pushback is then complete and the aircraft can taxi forward under its own power.

5) 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 emission. In some emergency cases, the power used can then be increased to increase the aircrafts performance. Before takeoff, the engines particularly piston engines are routinely run up at high power to check for engine-related problems. The aircraft is permitted to accelerated to rotation speed(often referred to as Vr). The term rotation is used because the aircraft pivots around the axis of its main landing gear while still on the ground, usually because of gentle manipulation of the flight controls to make or facilities this change in aircraft attitude(once proper air displacement occurs under/ over the wings, an aircraft will lift off on its own, controls are to ease that in).

The nose is raised to a nominal 5degree to 15degree 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:-

Based on the type of plies used the tyres can be:-

Radial ply tires:-

These tyres feature a flexible casing which is constructed of rubber-coated ply cords which extend around the beads and are substantially at 90 degree to the centerline of the tread. The casing is stablized by an essentially inextensible circumferential belt.

Bias ply tires:- These tyres feature a casing which is constructed of alternate of rubber-coated ply cords which extend around the beads and are at alternate angles substantially less than 90 degree to the center line of the tread.

Based on the method for containing the inflation gas the tyres can be:

• Tube type tyres:- These require tubes for inflation retention.
• Tubeless tyres:- These do not require tubes. They are constructed with an innerlinear(integral rubber lining that is engineered to prevent the diffusion of the inflation gas into the casing).

Rolling Resistance:

The resistance offered by the tyres against motion of vehicle/aircraft is called as rolling resistance, the rolling resistance is produced during takeoff/ landing in the runway.

Tyre pressure:-

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 gases(normal air is about 80% nitrogen) but common compressed air sources may contain moisture, which increases the expansion rate with temperature.

Tests of airliner aircrafts tires have shown that they are able to sustain pressures of maximum 800psi(55 bar,5500kpa)before bursting. During the tests the tire have to be filled with water to prevent the test room being blown apart by the energy that would be released by a gas when the tire bursts.

The main landing gear on the concored was typically inflated to 232psi(16.0bar)whilst its tail bumper gear tires were as high as 294psi(20.3bar). The high pressure and weight load on the concorde tyres were a significant factor in the loss of air france flight 4590.

Brakes Forces when landing:-

In general, when the wheels touch the ground, a set of spoilers raise up quickly, which kills the lift provided by the wings.(There are two sets seen in the image below: ground spoilers that only deploy on landing and spoilers that are used in flight as speed brakes as well as on landing) while the spoilers provide some drag, their primary purpose is to stop the plane form actually flying putting all of the weight on the landing gear and in turn making the brakes that much more effective.

Aircraft have- engineered, multi-disc brakes made of a carbon-steel material. Manufacturers include honeywell and goodrich,part of collins Aerospace. In general, the brakes are composed of discs that rotate with the wheel and separate discs that are fixed. When pressure is applied and below you can see pressure applied from the right fixed disc on all of the discs-the entire assembly compresses to create the braking action. Carbon brakes are standard today; they cool faster than steel brakes(their predecessor) and can weigh up to 700 pounds less. That represents a significant weight saving for airlines.

Auto Brakes:-

Wheel brakes are usually selected to engage automatically after landing. These are called "autobrakes". that all airliners have several levels of autobrake "severity".The crew will decide which is the most appropriate to use for every landing depending upon factors like the length of runway, if it is wet or dry or if the pilots want to exit the runway at a particular point. "For a short wet runway you might select autobrake 3 or MED on the Airbus. For a long dry runway you might select autobrake 1 or low on the Airbus".

PART-B

6) For this question, the towing vehicle considered is KAMBLAR Two tractor TBL 190 and the aircraft considered is Airbus A319

TBL 190 is designed for pushback and maintenance towing of aircraft from MD-80/A319 up to B777/A340.

length:8,100mm

width:3,450mm

Height:2,050mm

Thus, frontal area is calculated to be:7.07m^2

Dry weight:15,150kg

working speed:23km/h,30km/h(14.3mph)

The Airbus A319 has the following specifications:

length 33.8m

wingspan 35.8m

Height 11.8m

maximum take off weight 64000-75500kg

weight of aircraft 35,400kg

Drag coefficient(Cd):Taxing0.031

take off:0.024

landing:0.017

The frontal area for the airbus A319 can estimated as

Area=width*Height

=2*2.54*2*2.38

=24.18m^2

The area of the wings can be estimated to be

Area=width*Height

=(35.08-(2*2.54))*0.3

=30.72*0.3

=9.2118m^2

Hence, the total frontal area to be considered for the aircraft and tow truck will be

=Frontal area of two truck+ Frontal area of aircraft

=Frontal area of tow truck+Frontal area of wings+frontal area of cabin

=7.07+9.2118+24.18

=40.46m^2

The forces to be taken into consideration while calculating the traction power required are

1) Frr=urrmg

Where Frr is the rolling resistance force in N

urr is the coefficient of rolling resistance

m is the total mass of vehicle in kg

g=9.81 is the acceleration due to gravity in m/s^2

2)Fad=1/2*Rho*A*v^2*Cd

Fad is the aerodynamic drag force in N is the air density

A is the frontal area of vehicle in m^2

Cd is the drag coefficient v^2 is the velocity in m/s

3) Fh=mgsin(sai)

where Fh is the hill climbing force in N

saiis the hill climbing Angle in radian

4) Fa=ma

where a is the acceleration of the vehicle in m/s^2

The summation of all the forces multiplied by the vehicle velocity will give the required power.

(B)The following m script is used for calculating the required power. The acceleration force is neglected here. Tractive requirement with changing urr is plotted.

clc
m=50550;
g=9.81;
ur=linspace(0.02,0.08,7);
rho=1.25;
A=40.46;
Cd=0.03;
v=6.4;
slope=0.035;
Ft=[];
for i=1:length(ur)
Fr=ur(i)*m*g;
Fd=0.5*rho*A*Cd*v^2;
Fh=m*g*sin(slope);
Ft(i)=Fr+Fd+Fh;
end
power=(Ft*v)/1000
%plot
plot(power,ur)
xlabel('tractive power in kw')
ylabel('Coefficient of rolling resistance')
title('Variation of tractive power with ur')

The torque required can also be calculated if the wheel radius and gear ratio of the towing vehicle are known by using the formula

Torque=force*radius/Gear Ratio

(7)(A)Assumption for powertrain Design

parameter values

Aircraft mass=150000kg

towing vehicle mass=40000kg

rolling resistance coefficient=0.01

Air Density=1.225kg/m^3

Towing vehicle drag coefficient=0.608

Aircraft drag coefficient=0.15

frontal area=18m^2

Inclination Angle=0rad

Tyre pressure=196PSI/13.51bar

Towing velocity(V)=10km/hr=2.778m/s

Towing time(t)=2min

Radius of the towing vehicle wheel=0.4m

Now from the above calculation we get the total force acting on the vehicle as:

Total Traction force(F)=18877.93056N

Power TRequired(P)=104.877392kw

Now, the torque required by the vehicle to move is given by:

Torque(T)=Force(F)*Radius of the wheel(R)

therefore,T=18877.93056*0.4

= 7551.1722Nm

The energy required by the vehicle for towing application is given by

Energy(E)=Power(P)*towing time

=104.877392*2/60

=3.496lwh

For this application an electric motor which can be either a BLDC motor or an Induction Motor is choosen for the above power specs is given below:

Here in the above figure, the peak motor output power given in the motor parameters in the input to the towing vehicle

So therefore input power to the towing vehicle(kw)=120

Output power of the towing vehicle(kw)=104.877392

Duty cycle=Output power/Input power

=104.877392/120

=0.87

therefore duty cycle=87%

So we can say that to control the Aircraft speed from Zero to highest the duty cycle range will be from 0 to 87% respectively.

The power train block Diagram for the entire towing application starting from the aircraft to the towing vehicle is given below:

From the diagram we can see that the Battery is supplying the power to the motorand that is controlled by the controller unit which is nothing but the inverter circuitry.As automotive batteries generally operates on DC while the grid operates on AC, so a converter is needed to transfer power to the battery. Because of these capability of EV vehicle, the efficiency of them are much more(80-60%)than the conventional IC engine type of vehicle(25-30%). This motor is then responsible for controlling the wheels and the brakes through the transmission and the gear system.