Project-1: Powertrain for aircraft in runways

Part A:

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

• Weight is a major factor in airplane construction and operation, and it demands respect from all pilots and particular diligence by all maintenance personnel.
• Excessive weight reduces the efficiency of an aircraft and the available safety margin if an emergency condition should arise.
• The total weight is the maximum take-off weight.
• It is the maximum mass at which the aircraft is certified for take-off due to structural or other limits

MTOW Maximum take-off weight, MLW Maximum landing weight, TOR Take-off run, LR Landing run

Maximum Takeoff Weight:

The maximum weight limit for an aircraft to begin its takeoff roll is called the max takeoff weight.

Maximum Landing Weight

The maximum landing weight is, as you might imagine, the maximum aircraft weight limit approved for an aircraft to land. Landing weight can cause structural damageThe maximum landing weight is, as you might imagine, the maximum aircraft weight limit approved for an aircraft to land. Landing weight can cause structural damage

In this above diagram refers that we canexplain the examples of heavy large and small aircrafts

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

ANS :

Ground speed

Ground speed is the horizontal speed of an aircraft relative to the ground.

An aircraft heading vertically would have a ground speed of zero.

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.

Wind Speed :

For a reference point picked on the ground, the air moves relative to the reference point at the wind speed.

A positive velocity is defined to be in the direction of the aircraft's 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.

Airspeed :

The important quantity in the generation of lift is the relative velocity between the object and the air, which is called the airspeed.

Airspeed cannot 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.

Airspeed Ground Speed - Wind Speed :

The aircraft usually operates on land as well as in the air and so need to study their speed differences in-ground and in air

The ground speed and the airspeed usually change based on the wind component.

If we consider that there is no wind component then, ground speed = airspeed

If the wind is blowing in the tail direction of the aircraft then (airspeed ground speed) so, airspeed = ground speed+ win component.

If the wind is blowing in the head direction of the aircraft then (airspeed ground speed)so, airspeed ground speed - wind component.

Also, gravity plays a major role in increasing the aircraft's specs while it is descending

Here wind speed is the vector difference between ground and airspeed. On a particular day, the wind speed may be zero is equal to the ground speed.

If the measured airspeed is greater than the observed ground speed the wind speed becomes positive.

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

ANS :

Aircraft can move using their own engine power all the time on the airport apron and taxiways under their own power to go towards runways and after landing taxi to their assigned gate.

But the thrust produced resulting in jet blasts 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. And also it can reduce the cost for fuel. Taxiing can save money.

Effectively a loss of control can happen, especially during high-power engine running. Damage can occur to the aircraft itself, other aircraft nearby or to airside structures.

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 drivers to see the surroundings better than the pilot sitting in the cockpit with a limited window.

The pushback driver knows the airport better than the pilot. It also saves fuel virgin Atlantic had proposed a new system in which a pushback truck will move the aircraft all the way to the runway to save fuel and reduce the impact of the environment.

The plane engines are very loud. When more than one plane will add up their sound, then it will not be pleasant for passangers and others near the airport.

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4 . How an aircraft is pushed to the runway when it's ready to take off?

ANS :

1) Taxing:

Taxiing is the movement of an aircraft on the ground, under its own power, in contrast to towing or push-back where the aircraft is moved by a tug.

The aircraft usually moves on wheels, but the term also includes aircraft with skis or floats.

An airplane uses taxiways to taxi from one place on an airport to another; for example, when moving from a hangar to the runway

2) Towing:

Movement of large aircraft about the airport, flight line, and hangar is usually accomplished by towing with a tow tractor.

In the case of small aircraft, some moving is accomplished by hand pushing on the correct areas of the aircraft.

Aircraft may also be taxied about the flight line but usually only by certain qualified personnel.

Towing aircraft can be a hazardous operation, causing damage to the aircraft and injury to personnel, if done recklessly or carelessly.

This article outlines the general procedure for towing aircraft.

However, specific instructions for each model of aircraft are detailed in the manufacturer's maintenance instructions and are to be followed in all instances.

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

ANS :

1) Take off the power:

Take off power can be predicted using a simple measure of the acceleration of the aircraft along the runway based on force equilibrium.

The forces involved will be.

T is the Thrust of the propulsion system pushing aircraft along the runway.

D is the Aerodynamic Drag of the vehicle resisting the aircraft's motion.

F is Rolling resistance friction due to the contact of wheels or skids on the ground.

During the take-off run, the imbalance in these forces will produce an acceleration along the runway.

m*(dv/dt)=T-D-F

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

The procedure for take-off will be that the vehicle will accelerate until it reaches a safe initial flying speed.

The pilot can then rotate the vehicle to an attitude to produce a climb lift and it will ascend from the ground The determination of this safe flying speed or rotation speed V. is a critical factor in determining take-off performance Take-off rules vary slightly depending on the aircraft category.

For Small commuter aircraft

V=1.1*VSTALL

V=1.05*V control

VSTALL =√(W/0.5CtmaxρS)

where S-Runway length

Take off power= force*displacement

(m*dv/dt)*2*s1 = (T-D-F)*S1

2) Tyre design :

Designing aircraft tires is a very intense undertaking The tire is designed to withstand heavy loads while landing, taking off, taxing, and parking.

The number of wheels required for aircraft increases with the weight of the aircraft, as the weight of the airplane needs to be distributed more evenly.

Aircraft tyre generates more heat during landing Aircraft drags the wheel until they match the rotational velocity of the wheels.

Due to this heat generates. The aircraft's tread pattern is designed to facilitate stability in high crosswind conditions, to channel water away to prevent hydroplaning, and for braking effect.

3) Construction of tyre :

Radial Tyre:

a ) It has fibre strands of the ply fabric oriented at 90° to the direction of rotation and the tyre sidewall.

1. b) This restricts flexibility bidirectional and the flexibility of the sidewall while it strengthens the tyre to carry heavy loads.

1. c) Due to their unique construction most radial tyres are resistant to penetration ad cuts. Due to stiffer tread they distribute weight evenly.

1. d) Thus provide greater traction. Radial tyres have an advantage in term of reducing the heat better.

Bias-ply Tyre:

1. a) It has the fabric bias oriented with and across the direction of rotation and the sidewall.

1. b) Since fabric can stretchon the bias, the tyre is flexible and can absorb loads.

1. c) Tyre strength is obtained by adding plies.

1. d) It is cut resistant is sidewall area.

1. e) These tyres do not offer as much smoothness in terms of riding quality.

4) Rolling Resistance:

Rolling resistance is the force resisting the motion when a body (such as ball, tyre or wheel) rolls on a surface.

Rolling resistance can be seen in the aircraft when the aircraft takes-off from the runway & while landing at the runway with the help of their wheels

Rolling resistance can be expressed as Fm g (N).

Where

Frr the Rolling resistance(N)

μrr coefficient of rolling resistance.

m is mass(kg)

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

5) Tyre pressure :

Aircraft tyres operate at such high extremes of pressure, load, and speed, their care and service is critically important.

The most important action an operator can take to prevent tyre-related events is to maintain proper tire inflation pressure.

Failure to keep aircraft tires properly inflated can lead to very serious consequences.

One relatively easy way to help avoid those consequences is to check tire pressures regularly and service them as necessary.

Following these three actions is a good way to make sure you get the most value out of your tires and contribute to the safe operation of your aircraft.

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, Also, the use of an inert gas for tire inflation eliminates the possibility of tire explosion.

Relation to Rolling Resistance and Tire Pressure :

Braking Forces during Landing :

Following braking devices are used to decelerate the aircraft -

2. Wheel Brakes (Including Anti-Skid systems & Auto-Brake systems)
3. Reverse Thrust

6) Spoilers :

The mechanical deflection of parts of the wing upper surface by increasing aerodynamic drag on the moving aircraft.

This can be achieved by raising upper wing surface panels called ground spoilers or by operation of a tail cone 'clamshell type air brake and also by increasing the effective downward load on the landing gear and thereby increasing the efficiency of wheel braking

7) Wheel Brakes :

To be effective, braking action at any speed depends upon sufficient friction existing between the tires and the runway surface achieved through freely rotating wheels.

Anti skid system :

When landing on slippery runways, there's a chance that the wheels may start to skid as the brakes are applied. To stop this from happening and to maintain maximum effective braking, each wheel has anti-skid protection.

Using a variety of sources to determine the aircraft speed, the brake units know how fast the wheels should be spinning. If that speed drops significantly, it's because the current brake pressure on that wheel is too great and the wheel is just skidding over the surface.

In this situation, the anti-skid system automatically reduces the braking on that wheel to a point where the skid stops before reapplying the pressure.

8) Reverse Thrust :

Thrust reversers provide a deceleration force that is independent of runway condition.

Thrust reverser efficiency is higher at high airspeed, therefore-Treversers must be selected as early as possible after touchdown.

Thrust reversers should be returned after reverse idle at low airspeed to prevent engine stall or foreign object damage.

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

				Data	Frr
Mass of aircraft, mA = 575,000kg				Aircraft	Crr	m in kg	g	Frr=Crr*m*g in N	Frr in KN
Mass of pushback is 1000kg(assume)					0.002	575000	9.81	11281.5	11.2815
Coefficient of rolling resistance (Crr) = 0.002
Rolling resistance (Frr) = Crr * m * g				Towing vehicle	0.002	1000	9.81	19.62
For the Aircraft, Frr = 0.002*575,000*9.81
Frr = 11.2815kN
For the Towing Vehicle, Frrt = 0.002*1000*9.81
Frrt = 19.61N
As the towing vehicle resistance is very less compared to aircraft, since it is a heavy vehicle this resistance can be neglected.
Aerodynamic resistance, (Far)
Given
Drag coefficient Cd = 0.025
Air density ρ = 1.125kg/m^2				Data	Frr	far
Fronatal Area A = 150 m^2				Aircraft	A=Area	V=velocity km/hr	V=velocity m/s	far=(1/2)*Cd*p*V^2	far in N
Velocity v = 14.5kmph or 4m/s					150m^2	14.5	4.02777778
Far = (1/2)*Cd*ρ*V^2					Cd	p in kg/m^2	Area in m^2	34.2203776	34.2203776
Far = (1/2)*0.025*1.125*150*(4)^2					0.025	1.125	150
Far = 33.75N
Total Force = 11281.5 + 34.22								total force	11315.72038	N
= 11315.47 N			11315.47076
As the tow vehicle and plane moving at al ow speed this force can be neglected
Hill Climbing resistance:							by considering the actual factors Fte=Frr			11281.5	N
Runways are constructed flat so gradient force or hill climbing force is neglected.
Total Traction Force:
Fte = Frr							power needed =Ft*v		45439.375	W
= 11281.5									45.439375	Kw
Power required

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SIMULATION MODEL :

The different forces involved when the plane is moved by a tow vehicle:

To proceed for calculating the force and power required to push or pull an aircraft by a towing vehicle, we will assume the following parameters:

Here we will consider aircraft and towing vehicle as separate units. We will also consider acting on aircraft as well as towing vehicle which are;

Rolling Friction Force

Acceleration Force

Aerodynamic drag force

We will neglect the all the losses for calculations.

Data taken :

The total mass of the aircraft including payload for aibus a 380 bs 575,000kg

Aircraft Calculations:

Mass of aircraft, mA = 575,000kg

Mass of pushback is 1000kg(assume)

Coefficient of rolling resistance (Crr) = 0.002

Rolling resistance (Frr) = Crr * m * g

For the Aircraft, Frr = 0.002*575,000*9.81

Frr = 11.2815kN

For the Towing Vehicle, Frrt = 0.002*1000*9.81

Frrt = 19.61N

As the towing vehicle resistance is very less compared to aircraft, since it is a heavy vehicle this resistance can be neglected.

Aerodynamic resistance, (Far)

Given

Drag coefficient Cd = 0.025

Air density ρ = 1.125kg/m^2

Frontal Area A = 150 m^2

Velocity v = 14.5kmph or 4m/s

Far = (1/2)*Cd*ρ*V^2

Far = (1/2)*0.025*1.125*150*(4)^2

Far = 33.75N

Total Force = 11281.5(Frr) + 33.75(Far)

= 11315.25 N

As the tow vehicle and plane moving at al ow speed this force can be neglected

Hill Climbing resistance:

Runways are constructed flat so gradient force or hill climbing force is neglected.

Total Traction Force:

Fte = Frr

= 11281.5

Power required

P = Ft*v

= 11315.25*4

= 45.26kW

Since the minimum power required at the tow vehicle is 45.126kW to taxi a heavy aircraft at 4m/s.

1. The Model for calculate force and power using Simulink:

Mathematical model of rolling resistance force: =Crr*m*g

Mathematical model of Aerodynamic force:

Mathematical model of the Total force and power required by the vehicle to push/pull the aircraft:

Velocity v = 14.5kmph or 4m/s

Total Force : Ft = 11281.5(Frr) + 33.75(Far)

= 11315.25 N

Power required

P = Ft*v

= 11315.25*4

• Constant blocks are used to feed the parameters such as mass, coefficient and other parameters.
• Using the product block the resistive forces are calculated.
• Sum blocks are used to calculate the total resistive force.
• The outputs are visualized using scope blocks.

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Outputs :

Rolling force Frr:

Aerodynamic :

Total power :

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Study - 7 :

Design an electric powertrain with the type of motor, it's power rating, and energy requirement to fulfill aircraft towing application

Assumption For Powertrain Design

The power required by the aircraft is 45.26kW. Consider a motor with the following specifications.

Voltage 400-800V

Peak Power 60-70kW

RPM 1500-4000

Torque 300Nm

Transmission

consider 60kW as peak power therefore voltage will be 400V.

Assume battery power to be 550V.

Now we can calculate the duty cycle

d=Vo/Vs

= 400/550 = 0.7272

Duty cycle is the 0.7272

Assume parameterss

Parameter value

Aircraft Mass (mA) = 575,000kg

Towing vehicle Mass =50,000kg(assume)

Rolling Resistance Co-efficient (Crr) = 0.002

Air density ρ = 1.125kg/m^2

Towing vehicle Drag coefficient Cd = 0.5

Aircraft Drag co-efficient =0.09

Fronatal Area A = 150 m^2

Inclination angle = 0 rad

Tyre Pressure = 203PSI/14 bar

Towing Velocity (V) = 14.5kmph or 4m/s

Towing Time(t) = 2 min

Radius of the towing vehicle wheel = 0.38

Rolling Resistance calculation:
	Parameters	units	values
	kerb weight	kg	575,000
	total weight=m	kg	575,000
	coefficient of rolling reisistance= Crr	m/s^2	0.002
	Acceleration due to gravity(g)	N	9.81
	Rolling Resistance force (Frr)=Crr*m*g		11281.5
Airdrag calculation:
	Air density(p)	kg/m^2	1.125
	width	m	10
	height	m	15
	frontal area	m^2	150
	Air drag co-efficient Cd for aircraft		0.025
	speed( V) in m/s	m/s	4
	Airdrag force-- Fad =(1/2)*Cd*p*A*V^2		33.75	33.75
	Hill climbing Angle	Rad		0
	sine	Rad		0
	Fhc	N		0
	Total Tractive force (Fte)=Frr+Fad	N	11315.25	11315.25
	power required P=Ft*v	KW	45.261	45.261
	Duty cycle
	Voltage	V	400
	peak power	KW	60
	RPM	rpm	1500-4000
	Torque	Nm	300
	Battery power (assume)	V	550
	duty cycle		0.727273

Block diagram of powertrain:

Simulink Model:

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The above figure shows the powertrain arrangement of a tow tractor for towing aircraft. The battery source is displayed at the left. The battery parameters are the maximum voltage value of the selected motor. The motor characteristics is implemented as calculated above.

The 200 HP DC motor is separately excited with a constant 150 V DC field voltage source. The armature voltage is provided by an IGBT converter controlled by two PI regulators.

The converter is fed by a 515 V DC bus obtained by rectification of a 380 V AC 50 Hz voltage source. 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.

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 behavior, 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.

Output:

b). Design the parameters in the Excel sheet is attached.

Rolling Resistance calculation:
	Parameters	units	values
	kerb weight	kg	575,000
	total weight=m	kg	575,000
	coefficient of rolling reisistance= Crr	m/s^2	0.002
	Acceleration due to gravity(g)	N	9.81
	Rolling Resistance force (Frr)=Crr*m*g		11281.5
Airdrag calculation:
	Air density(p)	kg/m^2	1.125
	width	m	10
	height	m	15
	frontal area	m^2	150
	Air drag co-efficient Cd for aircraft		0.025
	speed( V) in m/s	m/s	4
	Airdrag force-- Fad =(1/2)*Cd*p*A*V^2		33.75	33.75
	Hill climbing Angle	Rad		0
	sine	Rad		0
	Fhc	N		0
	Total Tractive force (Fte)=Frr+Fad	N	11315.25	11315.25
	power required P=Ft*v	KW	45.261	45.261
	Duty cycle
	Voltage	V	400
	peak power	KW	60
	RPM	rpm	1500-4000
	Torque	Nm	300
	Battery power (assume)	V	550

Conclusion:

• Since we saw the total weights of type of aircrafts.
• Given the difference between the airspeed and ground speed.
• Since we have see the engine power to move it on the ground in the aircraft with the help of tow vehicle.
• Explained how aircraft is pushed to runway when its ready to take off.
• We have Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.
• Calculate the Force and power required to push/pull an aircraft bya towing vehicle.
• Design the electric vehicle powertrain with motor rating duty cycle which motor is contrlled using controller and also calculate power, Torque to move the aircraft with the towing vehicle.