Project-1: Powertrain for aircraft in runways

AIM -

• To Search and list out the total weight of various types of aircraft.
• To differentiate between ground speed and airspeed.
• To Explain Why is it not recommended to use aircraft engine power to move it on the ground at the Airport.
• To Explain How an aircraft is pushed to the runway when it's ready to take off.
• To Learn about take-off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.
• To calculate the force and power required to push/pull an aircraft by a towing vehicle with necessary assumptions and develop the model for calculated force and power using Simulink.
• Design an electric powertrain with a type of motor, power rating, and energy requirement to fulfil aircraft towing application in Simulink. Estimate the duty cycle range to control the aircraft speed from zero to highest. Make all required assumptions. Prepare a table of assumed parameters. Draw a block diagram of the powertrain and plot the parameters in an excel sheet.

PART-1

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

The overall aircraft weight at any point during the flight or ground operation is referred to as the Aircraft Gross Weight. During the flight, the gross weight of an aircraft is referred to as the en-route weight or in-flight weight. Aircraft gross weight is not a constant value it decreases as the flight is flying because of the consumption of fuel and oil consumption.

Several weight limitations apply to an aircraft's gross weight to avoid overloading its construction or exhibiting unsatisfactory performance or handling attributes while in operation. These limitations are defined during an aircraft's design and certification phases and are documented in the type certificate and manufacturer specification papers.

MDTW/MDRW (Maximum Design Taxi/Ramp Weight) - The maximum design taxi weight is the maximum weight certificated for aircraft ground manoeuvring (taxiing or towing), as determined by aircraft strength and airworthiness regulations.

MDTOW (Maximum Design Take-Off Weight) - It is the maximum certificated design weight when the brakes are released for takeoff. Due to climatic circumstances, aircraft performance and airport features, the maximum weights for the takeoff may be limited to values less than the maximum takeoff weight.

MDLW (Maximum Design Landing Weight) - It is the maximum certificated design weight at which the aircraft meets the appropriate landing certification requirements. The maximum landing weight is typically designed for 10 feet per second sink rate at a touch down with no structural damage.

MDZFW (Maximum Design Zero-Fuel Weight) - The maximum certificated design weight of the aircraft less all usable fuel and other specified usable agents (engine injection fluid, and other consumable propulsion agents). It is the maximum weight permitted before usable fuel and other specified usable fluids are loaded in specified sections of the aeroplane.

MFW (Minimum Flight Weight) - It is the minimum certificated weight for flight as limited by aircraft strength and airworthiness requirements.

OEW (Operating empty weight) - It is the sum of the empty weight and the crew plus their baggage.

COMPARISON FOR THE ABOVE LISTED WEIGHT -

It is said that Maximum design taxi/ramp weight is greater than maximum design take-off weight and Both Maximum design taxi/ramp weight and maximum design take-off weight are greater than the maximum design landing weight. The reason for this is that amount of fuel and oil the flight contains while landing is less than while the flight had while launching.

MDTW > MDTOW > MDLW

Maximum fuel weight is found by subtracting maximum design take-off weight and maximum design zero fuel weight.

MFW = MDTOW - MDZFW

Maximum payload weight(MPW) is equal to the difference between maximum design zero fuel weight and operating empty weight.

MPW = MDZFW - OEW

TYPES OF AIRCRAFT -

There are many categories of aircraft

1. Aeroplane Category
2. Rotor Craft Category
3. Powered Lift Category
4. Glider Category
5. Lighter than air Category
6. Powered parachute Category
7. Weight Shift control aircraft Category

Aeroplane Category - There are 4 types in Aeroplane Category

SINGLE-ENGINE LAND CLASS	SINGLE-ENGINE SEA CLASS	MULTI-ENGINE LAND CLASS	MULTI-ENGINE SEA CLASS
QUEST KODIAK 100	DeHavilland Turbo Beaver	King Air 200	Beechcraft D18s
WEIGHT - 1601KG	WEIGHT - 2700KG	WEIGHT - 5669KG	WEIGHT - 3250KG

RotorCraft Category - There are 2 types in RotorCraft Category

HELICOPTER CLASS	GYROPLANE CLASS
the empty weight of helicopters ranges from 135 kg to 15070 kg.	The aircraft has an empty weight of 265 kg and a gross weight of 450 kg.

Powered Lift Category -

the Above image is an image of a Bell XV-15, whose maximum take- off weight is 27445kg

GLIDER CATEGORY -

this category of planes weight ranges from 113kg to 680kg

LIGHTER THAN AIR CATEGORY -

AIRSHIP CLASS	BALLON CLASS
the above image is the image of an LZ 129 Hindenburg Zeppelin which weighs around 1,30,000 kg	this type of class weighs around 907kg

Powered Parachute Category -

powered parachute land class	powered parachute sea class
this type of class weight ranges from 90 to 225 kg	this type of class weight ranges from 90 to 225 kg

Weight-Shift-Control aircraft Category -

Weight-Shift-Control aircraft land class	Weight-Shift-Control aircraft sea class
this type of class weighs around 250kg	this type of class weighs around 250kg

RESULT - Searched and listed out the total weight of various types of aircraft

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

When we are travelling by car, the speed we are going is being measured relative to the ground, but things get tricky when dealing with the aircraft. In NO wind condition, the aircraft speed will be measured relative to the ground like in the case of the car but when the wind appears, its a game-changer because of the wind the air moves therefore, even though the car and aeroplane travel at the same speed, the travelled distance relative to the ground will be different. (i.e) the aeroplane will travel further. there are many airspeeds, but the speed which corresponds to the movement relative to air is called true airspeed.

In case the speed blows from the tail end of the aircraft, ground speed will be higher than the true airspeed because the aircraft gets help from wind.

Ground speed = airspeed + wind component

In case the speed blows from the head end of the aircraft, groundspeed will be lower than the true airspeed.

Ground Speed = airspeed - wind component

Ground speed	Airspeed
Ground speed is the aircraft’s speed relative to the ground.	Airspeed is simply the speed at which an aircraft is moving relative to the air it is flying in.
One thing that should be noted here is that it’s horizontal rather than vertical speed – an aircraft climbing completely vertically would have a ground speed of zero.	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.

RESULT - differentiated between ground speed and airspeed

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

There are several reasons why it is not recommended to use aircraft engine power to move it on the ground at the airport even though it is capable to move on by own. but before listing out the reasons let me explain taxing, towing, Pushback

Taxing - It is the movement of an aircraft on the ground, under its own power.

Towing - if the aircraft is moved by a tug or a tow tractor, it is called Towing.

Push back - If the aircraft is being pushed backwards with the tow tractor, it is called Push-back.

REASON -

• The jet surge from the engines has the potential to cause damage to the terminal building and adjacent equipment.
• Sand and debris can be blown by engines.
• Engines may suck up sand and debris, causing significant engine damage.
• The truck driver has a greater view of his surroundings than the pilot sitting in the cockpit with limited windows.
• The pushback truck driver is more familiar with the airport than the pilot.
• The plane engines are quite loud. When many planes are flying around the airport, this noise may mount up quickly. Most people do not enjoy the sound of strong motorcycles, therefore it will not be a pleasant experience for those sitting inside the terminal.
• It conserves fuel.
• Modern planes are enormous. It is challenging to manoeuvre such massive buildings in such confined spaces. An A380 has eight floors. The pilots will be unable to see anything straight ahead of them or behind the wings.

RESULT - Explained Why is it not recommended to use aircraft engine power to move it on the ground at the Airport

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

Aircraft are generally pushed by a tow vehicle such as tow trucks, It is mostly used to reverse an aeroplane from the terminal area until it is able to move on its own. These tow trucks will only assist in moving the aircraft to a location where the pilots may safely turn on the engines, not to the runway. tow vehicles are rarely permitted to travel on a runway unless in emergencies and for inspection, and the aeroplane will then taxi (move on their own) to the runway on its own.

aircraft cannot move in the reverse direction, so to take reverse pushback trucks are used.

The pilots will deploy flaps and slats on the aircraft wings during taxi. the motors that move the flaps and slats produces a loud whining sound. In subzero conditions, aircraft will need to be "de-iced" before landing. To eliminate built-up snow and ice, which can impede airflow over the wings and limit lift, the plane will be sprayed with an anti-freeze solution. Once in the air, the engines will supply heated air to keep ice and snow from accumulating on the wings.

RESULT - Explained How an aircraft is pushed to the runway when it's ready to take off.

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

(I) Take-Off power -

Takeoff is the phase of flight in which an aircraft leaves the ground and starts flying. The amount of power that an engine is allowed to produce for a limited period of time for takeoff is called take-off power. The total energy of an aircraft flying in the atmosphere can be calculated using the equation,

E = ½ m v2+ mgh

However additional energy is required by the engine in order to keep the aircraft flying at constant speed and altitude. the extra power needed can be calculated by the equation,

P = (dh/dt) m g

When an aircraft is ready for takeoff and has been approved by Air Traffic Control, the pilot or first officer releases the brakes and advances the throttle to boost engine power and speed down the runway. As the aeroplane speeds up, air travels quicker and faster over its wings, creating lift. Airspeed is shown on the aircraft's instruments, and it equals not just the plane's speed relative to the ground, but also the speed of any wind blowing toward the aircraft. When the airspeed hits a predefined threshold known as rotation speed, the pilot manipulates panels on the aircraft's tail to rotate the plane's nose upward. This generates even more lift, and the plane takes off.

V1- the speed beyond which a safe stop on a runway is no longer possible

VR- Rotational velocity

V2- the minimum speed needed to keep a plane flying.

The weight of the aeroplane, the air temperature, and the airport's altitude are all elements that impact VR and V2. The more the lift, the greater the speed required to lift the aeroplane off the ground. On a hot day, aircraft must travel faster than on a cold day. Hot air is less dense than cool air, and lower density results in less lift at the same speed.

(II) Tyre design -

Designing aeroplane tyres is a difficult task. The tyre is built to handle high stresses during landing, takeoff, taxing, and parking. The number of wheels necessary for aircraft grows in proportion to the aircraft's weight since the weight of the aircraft must be spread more equally. A Boeing 737NG & 737MAX uses 6 wheels, Boeing 787 uses 10 wheels, Boeing 777 uses 14 wheels and Airbus A380 uses 22 wheels.

During landing, the aircraft tyre creates extra heat. The aircraft drags the wheel until its rotational velocity matches that of the wheels. As a result of this, heat is generated. The tread pattern of an aircraft is meant to aid in stability in high crosswind situations, to channel water away to minimise hydroplaning, and to provide braking action.

DESIGN AND CONSTRUCTION OF AIRCRAFT TYRE -

Carcass plies are used to form the tire. These aircraft tyres don't have to carry the load for a longer period of time like automobiles, therefore they are built in a way that they can absorb the high impact loads of landing and also it’s operating at high speeds for a short time when required.

Technical aspects of tyre -

1. Apex strip: A triangular piece of stiff rubber which is fitted onto the bead core to taper the rigid bead into the flexible body plies in the sidewall.
2. Bead heel: Outer edge of the bead.
3. Bead toe: Inner edge of the bead.
4. Breaker: Breakers are fabric plies placed directly on the upper-most ply beneath the tread rubber. They disperse stress throughout the tire. This breaker is utilized in a limited number of Bridgestone aircraft tires.
5. Chafer strip: Reinforces the beads and protects the cord body-plies from damage from rim friction or from damage when replacing the rim.
6. Carcass plies: Each nylon ply is held by wire beads across the tire to keep the tensile strength at the proper level, and is folded to the side of the sidewall. Each ply is provided with cushion rubber to reduce the shearing forces produced between the cords of the tire when it is deformed. Multiple coated-nylon cords are crossed alternately on the bias to make the carcass.
7. Decoration line: A projecting, embossed line moulded between the shoulder and sidewall of a tire. Its purpose is for decoration only.
8. Flipper strip: A strip of material that is wrapped around the bead bundle and filler to add support and help taper the assembly into the sidewall.
9. Inner liner: A sheet of special rubber laminated to the inside of the first casing ply of the tubeless tire so as to ensure retention of pressure when the tire is inflated.
10. Ply turn-ups: The turned-up ends of plies around the bead. Other plies lock the ends into place.
11. Tread reinforcing fabric: Nylon cord plies located in the tread between the tread groove and the outer ply of the carcass which reduce tread squirm and increase stability for high-speed operations.
12. Rim line: This line is provided near the beads to allow inspection of how the tire fits with the rim.
13. Shoulder: The area on the side of the tire between the sidewall and the tread.
14. Sidewall: The side area of the tire located between the buttress and the beads. Composed of rubber, it protects the carcass from damage.
15. Tread: A layer of rubber on the outer circumference of a tire, its major functions are to protect the casing from cuts, withstand high speed during take-off and landing, provide traction, resist wear, provide durability under a wide range of temperatures and ensure stability (in particular, the effective discharge of water on wet runways). The tread compound is designed to suit a wide range of operations.
16. Under tread: A rubber layer provided for use in retreading the tire and which provides adhesion of tread to the cord body. Bridgestone makes this rubber layer thick enough to ensure a high number of retreads.
17. Wire beads: Constructed of steel wire encased in rubber, they help to maintain the shape of the tire and keep it securely fixed to the rim. The wire beads are wrapped with fabric.
18. Venting hole: The hole through which gas is vented from inside the carcass plies.

THERE ARE TWO TYPES OF TYRES USED IN AIRCRAFT -

RADIAL TYRE -

It has ply fabric fibre strands aligned at 90° to the direction of rotation and the tyre sidewall. This reduces bidirectional flexibility and sidewall flexibility while strengthening the tyre to bear large loads. Most radial tyres are resistant to puncture ad cuts due to their unique design. Because of the stronger tread, they distribute weight more evenly. As a result, give more traction. Radial tyres provide an advantage in terms of heat reduction.

BIAS-PLY TYRE -

It has the bias of the fabric aligned with and across the direction of rotation, as well as the sidewall. The tyre is flexible and can absorb loads because the cloth can stretch on the bias. Plies are added to increase tyre strength. The sidewall region is cut resistant. In terms of ride quality, these tyres do not provide as much smoothness.

(III) ROLLING RESISTANCE -

The Rolling resistance force is mainly Experienced by the Tyre when the vehicle moves over any surface. The rolling resistance force is given by the expression,

Frr = Urr * (m.g)

Where,

• Urr = coefficient of rolling resistance
• m = mass of the vehicle.
• g = gravitational constant.(9.81m/s^2)

The friction between the aircraft and the runway will be proportional to the normal force exerted by the aircraft on the runway.
The normal force will be equal to the weight of the aircraft, the friction coefficient will be typical of a magnitude of 0.02 for a standard tarmac runway.

(IV) TYRE PRESSURE -

An aeroplane tyre is intended to bear exceptionally large loads for short periods of time. The number of tyres necessary for aircraft grows in proportion to the aircraft's weight since the weight of the aircraft must be spread more equally. Aircraft tyre tread designs are designed to aid in stability in high crosswind situations, to channel water away from the aircraft to minimise hydroplaning and to provide braking action.

Fusible plugs (which are installed on the inside of the wheels) are also used in aircraft tyres and are engineered to melt at a particular temperature. Tires frequently overheat when full braking is used during a failed takeoff or emergency landing. The fuses enable a safer failure mode by deflating tyres in a controlled way, limiting harm to aircraft and objects in the surrounding environment.

The pressure of an aeroplane tyre is typically quite high in order to decrease rolling resistance and to handle the weight. The pressure is usually between 200 and 300 psi, although it varies depending on the kind of aircraft. Airliner aeroplane tyres have been tested and proved to be capable of sustaining pressures of up to 800 psi. Nitrogen is typically used to inflate aircraft tyres in order to reduce expansion and contraction caused by severe variations in ambient temperature and pressure encountered during flight.

(V) BRAKING FORCE -

To stop an aircraft braking plays a vital role, there are many components to apply braking force,

spoilers-

Mechanical bend of portions of the top surface of the wing caused by increasing aerodynamic drag on a moving aircraft.

This can be accomplished by elevating upper wing surface panels known as ground spoilers or by using a tail cone 'clamshell' style air brake, as well as by increasing the effective downward pressure on the landing gear and therefore improving the efficacy of wheel braking.

Wheel braking -

The landing gear of an aircraft has disc rotors, which are used to brake the wheels when they make contact with the ground. These brakes are either hydraulic or electrical controlled.

If the hydraulics system is used to power the braking units. The flight deck sends an electronic signal to hydraulic actuators near the main landing gear. In this case, 3,000 pounds per square inch hydraulic fluid is utilised to push the brake unit against the wheel, slowing it down.
If the electric system is used to power the braking units. When the pilots push the brake pedals, an electrical signal is delivered to the wheel's braking unit. Electric actuators are employed here to push the carbon brake disc against the wheel, slowing it down.

Anti-skid system - When landing on a wet runway, the wheels may begin to skid even when the brakes are applied. To avoid this anti-skid system is used.

The braking units know how quickly the wheels should be spinning because they use a number of sources to calculate the aircraft speed. If the speed reduces substantially, it's because the braking pressure on that tyre is too high and the wheel is just sliding across the terrain.

In that case, the anti-skid system immediately decreases braking pressure on that wheel until the skid ends before reapplying pressure.

Reverse Thrust:

Thrust reversers offer an independent deceleration force regardless of runway condition. As a result, at high airspeed, thrust reverser efficiency is higher. Traverses must be chosen as soon as possible following a touchdown.

To avoid engine stalls, thrust reversers should be returned after reverse idle at low velocity.

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

6.

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

let us assume that, the aircraft that we are pushing or pulling is Boeing 747-8,

Mass of the Aircraft (M1)	442252 kg
Mass of the towing vehicle (M2)	50000 kg
Co-efficient of rolling resistance of Aircraft (`mu1`)	0.002
Co-efficient of rolling resistance of towing vehicle (`mu2`)	0.003
The drag coefficient for aircraft (Cd1)	0.15
The drag coefficient for the tug (Cd2)	0.7
The frontal area of aircraft(A1)	100`m^2`
The frontal area of tug (A2)	4`m^2`
Towing speed (v)	5 m/s
Air density (`rho`)	1.25 kg/`m^3`
Gravitational acceleration (g)	9.81 m/`s^2`

Formulae Used -

• rolling resistance - `Fr = mu*m*g`
• Aerodynamic drag force - `Fd = 1/2*rho*A*Cd*v^2`

CALCULATION -

Rolling resistance -

`F_(r1) = (0.002)*(442252)*9.81 = 8676.9N`

`F_(r2) = (0.003)*(50000)*(9.81) = 1471.5N`

Aerodynamic drag force -

`F_(d1) = (0.5)*(1.25)*(100)*(0.15)*(5)^2 = 84.375`

`F_(d2) = (0.5)*(1.25)*(4)*(0.7)*(5)^2 = 15.75`

TOTAL FORCE = `F_(r1)+F_(r2)+F_(d1)+F_(d2)`

F = `86769.9+14715+84.375+15.75=101500N = 10.2 KN`

POWER REQUIRED = TOTAL FORCE * TOWING VELOCITY

P = `(10.2)*(3) = 51.24 KW`

RESULT- calculated the force and power required to push/pull an aircraft by a towing vehicle with necessary assumptions

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

Simulation diagram -

the constant block is used to give parameters such as Mass, velocity, coefficient of rolling resistance, Drag coefficient, front area, air density, Gravitational acceleration constant.

Explanation -

• To implement the rolling resistance formula and aerodynamic drag formula, the product block and the square block is used.
• To calculate the total forces, a sum block is used and To calculate the power required, a product block is used.
• To finally display the forces and power required, a display block is used.
• Results displayed in the display block and results calculated in the previous question are the same.

Simulation file - https://drive.google.com/file/d/1tZxW0NvdK_ff8CDop-7cz7vVYZKhKW1n/view?usp=sharing

Result - developed the model for calculated force and power using Simulink.

7.

A. Design an electric powertrain with the type of motor, its power rating, and energy requirement to fulfil aircraft towing application in Simulink. Estimate the duty cycle range to control the aircraft speed from zero to highest. Make all required assumptions. Prepare a table of assumed parameters. Draw a block diagram of the powertrain.

Aircraft towing vehicle - The aircraft towing vehicle that we are choosing is Challenger 700,

The CHALLENGER 700 is a conventional aircraft tractor capable of pulling all wide-body aircraft, even a fully-loaded Airbus, for push-back, repositioning, and maintenance.

characteristics -

From the official performance characteristics list from the company, it is said that it can pull about 600tons (600000 kg),

the weight of the aircraft we have chosen is around 475 tons, therefore Boeing 547-8 can be pulled by a challenger 700 towing truck.

MOTOR SPECIFICATION -

Motor	REB 90
voltage	400–800 V
Pole	4
rated power	60
peak power	80
efficiency	90%

Estimate the duty cycle range to control the aircraft speed from zero to the highest

Duty cycle = `(Output power)/(Input power)`

Where output power is the required power by the towing vehicle that is 51.24kw

input power = Rated Motor Power/Motor Efficiency = 60 / .9 = 66.666

D = `51.4 / 66.6 = 0.771`

The duty cycle will be 77.1%.

The duty cycle range to control the aircraft speed from zero to highest is from 0 to 77.1 %

Assumed parameters -

Assumed parameters	values
Mass	442252 kg
Co-efficient of rolling resistance(Crr)	0.002
Drag coefficient(Cd)	0.15
Air density	1.25kg/m^3
Velocity	5 m/s
Frontal Area	100m^2
uphill gradient	0
battery voltage	550v

BLOCK DIAGRAM OF POWERTRAIN -

SIMULATION -

Simulink file - https://drive.google.com/file/d/1ZGzk0lZopGIKDZOPxs0z3gYSZF4Qd0yi/view?usp=sharing

INPUT GRAPH -

The above graph is the input given using the Signal builder block.

Battery graph -

DC DRIVE OUTPUT -

• The speed reference is set at 500 rpm at t = 0 s. Observe that the motor speed follows the reference ramp accurately (+400 rpm/s) 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 drops to -1184 rpm. The current reference decreases to reduce the electromagnetic torque and causes the motor to decelerate with the help of the load torque.
• At t = 2.2 s, the current reverses to produce a braking electromagnetic torque (dynamic braking mode). This causes the DC bus voltage to increase.
• At t = 3.25 s, the motor reaches 0 rpm and the load torque reverses and becomes negative. The negative current now produces an accelerating electromagnetic torque to allow the motor to follow the negative speed ramp (-400 rpm/s). At t = 6.3 s, the speed reaches -1184 rpm and stabilizes around its reference.

B - Design the parameters in an excel sheet

excel sheet link - https://drive.google.com/file/d/115Ha-de_niyTUI8xmOxg8VkXgUNayg1M/view?usp=sharing

RESULT - Designed an electric powertrain with a type of motor, power rating, and energy requirement to fulfil aircraft towing application in Simulink. Estimated the duty cycle range to control the aircraft speed from zero to highest. Made all required assumptions. Prepared a table of assumed parameters. Drawn a block diagram of the powertrain and plotted the parameters in an excel sheet.