Project-1: Powertrain for aircraft in runways

AIM

Part A:

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

2. Is there any difference 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?

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

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

Part B:

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

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

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

(Hint : DC7 Block)

B. Also, Design the parameters in an excel sheet.

1.To search and list out various types of Aircraft along with their gross weight respectively.

Aircraft Gross Weight:

As per the federal aviation department, aircraft gross weight is defined as the total weight at any moment during flight or ground operation.

The aircraft's gross weight decreases during the flight due and oil consumption. In some case, gross weight (aircraft) may vary due to a drop in payload or inflight refueling, whereas on the other hand when the brakes are released the gross weight will be equal to take-off weight.

During the flight, an aircraft's gross weight will be referred to as inflight weight.

Types of aircraft weights are the following:

1)Manufactures empty weight:

-It includes the weight of aircraft of the entire flight with its internal working parts but excludes baggage, passenger, and fuels.

2)zero fuel weight:

-It includes the total weight of airplanes including unusable fuels but excludes the total weight of useable fuel at the board.

3)Payload:

-It is the load-carrying capacity of an aircraft that includes passengers, cargo, and fuels, But if it is in the case of cargo flight it determines the total load of logistics weight of the container which it needs to transport.

4)Maximum take-off weight:

-This is the maximum weight at which the aircraft would be made to take off.

5)Regulated take-off weight:

-Depending on different factors (flap setting, altitude, length of runway), RTOW varies for each take-off, but can never be high for MTOW.

6)Maximum landing weight:

-It is the maximum weight at which an aircraft is permitted to land.

7)Maximum Ramp weight:

-It is the maximum weight used for manoeuvering (towing) aircraft on the ground.

-Listed below are the types of aircraft with their weight:

Category MTOW(kg) MLW(tons)

Boeing 747-8F 447,700 346.091

Airbus A380-800 575,000 394

Concorde 185,000 111.1

Antonov An225 640,000 91.7

Vickers VC10 152,000 151.9

Fokker 100 46,000 39.95

Embraer 175(19) 37,500 32.8

Avro RJ-85 42,000 36.47

Tupolev Tu-154M 104,000 80

Boeing 777-300 299,370 237.683

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

As we know, true airspeed is simply the speed at which the aircraft is moving relative to the air it is flying in. As such, it is also the speed at which the air is flowing around the aircraft’s winds. Ground speed on the other hand is aircraft relative to the ground. one thing that is noted here is that it is horizontal rather than vertical speed – an aircraft climbing completely vertical would have a ground speed at zero. In other words, while airspeed is what determines whether there is enough airflow around an aircraft is what determines whether there is enough airflow around aircraft to make it fly, ground speed is what determines how fast an aircraft will get its attention.

Aerodynamic forces are generated by an object moving through a fluid (liquid or Gas). A fixed object in a static fluid doesn’t generate aerodynamic forces. Hot air balloons lift because of buoyancy forces and some aircraft like the Harrier use thrust to lift the vehicle, but these aren’t examples of aerodynamic lift. To generate lift the object must move through the air, or air must move past the object. Aerodynamic lift depends on the square of the velocity between the object & the air. Now things get confusing because not only can the object be moved through the air but the air itself can move. To properly define the relative velocity, it is necessary to pick a fixed reference point and measure velocities relative to the fixed point.

The aircraft usually operates inland as well as in air so we do not need to study their differences in-ground and in air.

The difference between the ground speed & airspeed is caused by the influence of the winds on the overall velocity of the aircraft.

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

If we decide that there is no wind component, then Ground Speed = Air Speed.

If the wind is blowing in the tail direction of an aircraft, then (Air Speed > Ground Speed)

AirSpeed = Wind Component + Ground Speed.

If the wind is blowing in the head direction of the aircraft then, (Air Speed < Ground Speed)

AirSpeed = Ground Speed - Wind Component.

Gravity plays a major role in increasing the aircraft's speed while it is descending.

3.Why it is not recommended to use aircraft engines to move it on the ground at the airport?

-Generally, most of the airplane can move in a reverse manner by making use of reverse thrust technology. But in most of the practice, it is not possible because when airplanes start using reverse thrust it will consume a lot of fuels as well as causes a lot of noise and also be hazardous for the people working nearby.

-The another for not using reverse thrust is that the jet blast can cause damage to terminal buildings or their equipment. Since the engine is also close to the ground it will blow off the sand and debreis forward and sucks it to the engine and causes damage to it.

-To solve this kind of issue we use a towing vehicle which helps to tow the vehicle in the reverse direction and it will be tugged until it reaches a safe place and from there onwards airplane will move by itself for further take-off.

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

Taxiing refers to the movement of an aircraft on the ground, under its own power. The aircraft moves on wheels. An airplane uses taxiways to taxi from one place to another.

When aircraft is ready with all the passengers and luggage for aviation then pushback is the aviation procedure during which an aircraft is pushed backward away from an airport gate by an external power. The aircraft always move on the ground following the yellow lines, to avoid any collision with the surrounding buildings, vehicles, or other aircraft. The taxiing motion has the speed limit. Before making a turn, the pilot reduces the speed further to prevent the tire skids. Just like cars, there is a certain list of priorities during taxiing. The aircraft that are landing or taking off have higher priority. The other aircrafts have to wait for these aircraft before they start or continue taxiing. The thrust to propel the aircraft forward comes from its propellers/jet engines. Steering is achieved by turning a nose wheel or tail wheel; the pilot controlling the direction traveled with their feet. The use of engine thrust near terminals is restricted due to the possibility of jet blast damage. This is why the aircraft are pushed back from the buildings by a vehicle before they can start their own engines for taxiing.

Pushbacks are carried out by special, low profile vehicles called pushback tractors/tugs.

These are heavy weighing low profile vehicles with enormous torque to do the job of pushing/pulling the large aircraft from the terminals to the runway.

The tractors are designed with extra weight purposefully to offer them enough traction to push or pull the heavy aircraft.

You Tube Link - https://www.youtube.com/watch?v=F077WDnB8P8

Take off –

Take-off is the phase of flight in which an aircraft goes through the transition from moving along the ground (Taxiing) to flying in the air, usually starting on a runway. Usually, engines are run at full power during take-off. Following the taxi motion, the aircraft stops at the starting line of the runway. Before take-off, the engines particularly the piston engines, are routinely run up at high power to check for engine-related problems. This makes considerate noise. when the pilot releases the brake, the aircraft starts accelerating rapidly until the necessary speed to take-off to achieve.

The take-off speed required varies with air density, air weight, aircraft configuration (flap/slat position) air density is affected by factors such as field elevation & air temperature.

Operations with transport category aircraft employ the concept of take-off V-speeds, V₁ & V_2. These speeds are determined not only by the above factors affecting take-off performance but also by the length and slope of the Runway. Below V₁, in case of critical failures, the take-off should be aborted; above V₁ the pilot continues the take-off and returns for landing. After the co-pilot calls V₁, then V₂ (the safe take-off speed) is called, this speed must be maintained after an engine failure to meet performance targets for rate of climb & angle of climb.

Operations with transport category aircraft employ the concept of the take-off & returns for landing after the co-pilot calls V₁. Then V₂ (the safe take-off speed) is called. The speed must be maintained after an engine failure to meet performance targets for rate of climb & angle of climb.

The speeds needed for take-off are relative to the motion of the air (indicated airspeed). Ahead wind will reduce the ground speed needed for take-off, as there is a greater flow of air over the winds. This is why the aircraft's always take off against the wind. Sidewind is not preferred as it would disturb the stability of the aircraft. Typical take-off airspeeds for Jetliners are in the 130-155 knot range (50-180mph) for a given aircraft, the take-off speed is usually directly proportional to the aircraft weight, the heavier the weight, the greater the speed needed. Some aircraft have difficulty generating enough lift at the low speeds encountered during take-off. These are therefore fitted with high-lift devices, often including flaps & slaps, which include the camber of the wing, making it more effective at low speed. Thus creating more lift. These have to be deployed from the wing before performing any maneuver.

At the beginning of the climbing phase, the wheels are retracted into the aircraft & the undercarriage doors are closed. The operation is audible by the passengers as a noise coming from below the floor.

Climb –

Following take-off, the aircraft has to climb to a certain altitude (30,000 ft. or 10 KM) before it can cruise at this altitude in a safe & economic way. A climb is carried out by increasing the lift of the wing supporting the aircraft until the lifting force and weight are again in balance. The increase in lift may be accomplished by increasing the angle of attack of the wings, by increasing the thrust of the engines to increase the speed (thereby increasing lift) by increasing the surface area or shape of the wing to produce greater lift, or by some combinations of these techniques.in most cases, engine thrust & angle of attack are simultaneously increased to produce a climb.

Because lift diminishes with decreasing air density, a climb once initiated, will end by itself when the diminishing lift with increasing altitude drops to a point that equals to the weight of the aircraft. At that point the aircraft will return to a level flight at a constant altitude. During the climb phase it is normal that the engine noise diminishes. This is because the engines are operated at a lower level after the take-off. It is also possible to hear a whirring noise or a change in the tone of the noise during climb. This is the sound of the flaps that are retracting. A wing with retracted flap produces less noise.

Cruise –

Cruise is the level portion of aircraft travel where travel where flight is most efficient. It occurs between ascent and descent phases and it is usually the majority of the journey. Technically, cruising consist of heading (direction of flight) changes only at a constant airspeed & altitude. It ends the aircraft approaches the destination where the descent phase of flight commences in preparation for landing.

For most commercial passenger aircraft, the cruise phase of flight consumes the majority of fuel. As this lightens the aircraft considerably, higher altitudes are more efficient for additional fuel economy. However, for operational & air traffic control reasons it is necessary to stay at the cleared flight level. Typical cruising speed for long-distance commercial passenger flights is 475-500 knots. (878 – 926 km/hr).

Commercial or passenger aircraft are usually designed for optimum performance at their cruise speed. There is also an optimum cruise altitude for particular aircraft type and conditions including payload weight, centre of gravity, air temperature, humidity & speed. The altitude is usually where the drag is minimum and the lift is maximum. As in any phase of the flight, the aircraft in cruise mode is always in communication with Air Traffic Control (ATC) station. Although the general tendency is to follow a straight line towards destination, there may be some deviations from the flight plan of the weather, turbulence, or Air Traffic reasons after receiving clearance from ATC.

Descent –

A descent during air travel is any portion where an aircraft decreases altitude. Descents are an essential components of an approach to landing. Other partial descents might be to avoid traffic, poor flight conditions (turbulence or bad weather), clouds (under visual flight rules), to see something lower, to enter warmer air (in case of extreme cold) or to take advantage of wind direction of a different altitude. Normal descents take place at constant airspeed & constant angle of descent (3 degrees’ final approach at most airports). The pilot control the angle of descent by varying the engine power & pitch angle (lowering the nose) to keep the airspeed constant.

At the beginning and during the descent phase, the engine noise diminishes further as the engines are operated at low power settings. However, towards the end of the descent phase, the passengers can feel further accelerations and an increase in the noise, to realise the “final approach” before taking the landing position.

Landing –

Landing is the part of the flight where the aircraft returns to the ground. Aircraft usually land at an airport on a firm runway, generally constructed of asphalt concrete, normal concrete, gravel or grass. To land the airspeed & the rate of the descent are reduced to where the object descends at slow enough rate to allow for a gentle touch down. Landing is accomplished by slowing down & descending to the runway. This speed reduction is accomplished by reducing thrust or inducing the greater amount of drag using flaps, landing gears or speed brakes.

The plane approaches the ground the pilot will execute the flare to induce the gentle landing. Although the pilots are trained to perform the landing operation, there are “instrument landing systems” in most of the airports to help pilots land the aircrafts. An Instrument Landing System (ILS) is ground based instrument approach system that provides precision guidance to an aircraft approaching and landing on a runway, using a combination of radio signals & In many cases, high intensity lighting arrays to enable safe landing during instrument meteorological conditions (IMC) such as low ceilings or reduced visibility due to fog, rain or blowing snow

At the beginning of the landing phase, the passengers will hear the opening of the doors of the landing gears. As the landing gears are deployed, they will create an additional drag & an additional noise. Immediately after touchdown, the passengers can hear a blowing sound, sometimes with increasing engine sound, sometimes with increasing engine sound. This is the engine’s thrust reverses, helping the aircraft to slow down to taxi speeds by redirecting the airflow of the engines forward. Once the aircraft is decelerated at forward speed, it can taxi to the terminal building.

5. Learn about take-off power, Tyre Design, Rolling Resistance, Tyre pressure, Brake forces when landing.

• Take – Off Power -

Take-off power is the phase of flight in which an aerospace vehicle leaves the ground and becomes airborne.

For the aircraft that take off horizontally, this usually involves starting with a transition from moving along the ground on a runway.

The take-off speed requires varies with air density, aircraft gross weight, & aircraft configuration.

The power from the engine of the aircraft used to achieve the flight is called take-off power & for light aircraft usually, full power is required during take-off, large transport category (airliner) may use reduced power for take-off, where less than full power is applied in order to prolong engine life, reduce maintaining cost, and reduce noise emissions.

This term is also known as take-off thrust. Pilots use great amount of thrust at take–off to decrease engine wear at take-off. Reduced power are dreaded take-off are normal & frequently used.

The performance is carefully calculated prior to each take-off ensuring proper speed, power setting and flaps are used for weight of the take-off on the runway intended & at the proper temperature. When using this method of take-off, it is always possible to increase to full power if the situation requires.

• Aircraft Tyre (Design & Construction) –

When it comes to safety, Tyres are one of the most important components of the aircraft. They help to absorb the shock of landing & provide cushioning. It also provides the necessary traction for the braking & stopping of an aircraft.

An aircraft is designed to withstand extremely heavy loads while landing, take-off, taxing & parking. The no. of wheels required for aircraft increases with the weight of the aircraft, as the weight of the airplane needs to be distributed more evenly.

The aircraft tyre is specifically designed because the tyre has to withstand more load & also the higher speed at the same time. The number of tyres required for aircraft increases with the aircraft’s weight, as the weight of the aircraft needs to be distributed more evenly. 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. Some of the type used tyre designs are –

Bias – ply tyres –

The Bias-ply tyre consists of casing piles running diagonally at approximately right angles to one another.

The number of piles and the angles at which they are laid dictate strength and load capacity.

High-performance Bias Aircraft tyre features inter-trade reinforcing fabric (ITF), thus provides additional high-speed stability. Reduces tread distortion under load, protects the casing piles from damage and can act as wear indicators on retread able tyres.

Tyre Terminology –

1. Apex Strip – A triangular strip of stiff rubber that is fitted onto the bead core to taper the rigid bead into the flexible body piles in the sidewall.
2. Bead heel – Outer edge of the bead.
3. Bead toe – Inner edge of the bead.
4. Breaker – Breakers are fabric piles placed directly onto the most upper ply beneath the tread rubber. They disperse tread throughout the tire. These breakers are utilized in a limited number of any company’s aircraft tyres.
5. Chafer strip – Reinforces the beads and protects the cord body piles from damage from rim friction or from damage while replacing the rims.
6. Carcass plies – Each nylon ply is held by wire beads across the tyre to keep the tensile strength at the proper level & it’s folded to the side of the sidewall. Each ply is provided with cushion rubber to reduce the shearing force produced between the cords of the tyre 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 molded between the shoulder and the sidewall of a tyre. Its purpose id for decoration only.
8. Flipper strip – A strip of material that is wrapped around the bead bundle & filler to add support & help tapper assembly into the sidewall.
9. Inner Liner – A sheet of special rubber laminated to the inside of the first casing ply of a tubeless tyre so as to ensure retention of pressure when the tyre is inflated.
10. Ply turn-ups – The turned-up ends of plies around the beads. Other plies lock the ends into place.
11. Tread Reinforcing Fabric – Nylon cord plies are located in the tread between the tread grooves & outer ply of the carcass which reduces tread squirm & increases the stability for high speed operations.
12. Rim line - The line is provided near the beads to allow inspection of the tyre fitting with the rim.
13. Shoulder – The area on the side of the tyre between the sidewall & 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 the tyre, its major functions are to protect the casing from the cuts, withstand high speed during take-off & landing, provide traction, resist wear, provide durability during a wide range of temperatures & ensure stability (effective discharge of water in wet runways). The tread compound is designed to suit a wide range of operations.
16. Under Tread - A rubber layer is provided for use in retreading the tyre which provides adhesion of treads to the cord body. Tyre manufacturing Companies make 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 in the shape of the tyre & keep securely fixed to the rim. The wire beads are wrapped with fabric.
18. Venting hole – The hole through which gas is filled from inside the carcass plies.
19. Balance Marker – The Balance Marker consists of red dot, affixed on the sidewall of the tyre immediately above the bead to indicate the lightweight point of the tyre.

Radial Tyre –

Radial tyres are modern designed aircraft tyres & its design is similar to that of aircraft tyres. Typically, the radial tyre offers more landings per trade & lighter weight than the bias tyres, though sometimes at the expense of retread lives. Radial aircraft tyres differs from Bias aircraft tyres in the plies that all run radially from bead to bead approximately at 90 degrees to the centre line of the tyre. Angled belt plies are made between the tread and top casing plies, resulting in a flatter tread & adding strength to the tyre.

Tyre Terminology –

Apex Strip – A triangular piece of stripper rubber which is fitted on to the bead core to taper the rigid bead into the flexible body plies in the sidewall.

1. Aramid Cord protector – The tyre is constructed with an Armid ply insert between the tread and the top belt to prevent the damage to the tyre belts.
2. Bead Heel – Outer edge of the Beed.
3. Bead toe – Inner edge of the Bead.
4. Inner Liner – A sheet of special rubber laminated to the inside of the first casing ply of tubeless tyre so as to ensure retention of pressure when the tyre is inflated.
5. Ply turn-ups – The turned-up ends of plies around the beads. Other plies lock the ends into place.
6. Venting hole – The hole through which gas is filled from inside the carcass plies.
7. Under Tread - A rubber layer is provided for use in retreading the tyre which provides adhesion of treads to the cord body. Tyre manufacturing Companies make this rubber layer thick enough to ensure a high number of retreads.
8. Wire Beads – constructed of steel wire encased in rubber, they help to maintain in the shape of the tyre & keep securely fixed to the rim. The wire beads are wrapped with fabric.
9. Sidewall – The side area of the tire located between the buttress and the beads. Composed of rubber, it protects the carcass from damage.
10. Tread – A layer of rubber on the outer circumference of the tyre, its major functions are to protect the casing from the cuts, withstand high speed during take-off & landing, provide traction, resist wear, provide durability during a wide range of temperatures & to ensure stability (effective discharge of water in wet runways). The tread compound is designed to suit a wide range of operations.
11. Rim line - The line is provided near the beads to allow inspection of the tyre fitting with the rim.
12. Chafer strip – Reinforces the beads and protects the cord body piles from damage from rim friction or from damage while replacing the rims.
13. Belt Pliers – Angled Belt plies serves to add strength to the tyre especially in the bead area.
14. Chafer Strip – Protective layer of rubber & fabric which prevents chafing between cord body plies & the wheel.
15. Balance Marker – The Balance Marker consists of a red dot, affixed on the sidewall of the tyre immediately above the bead to indicate the lightweight point of the tire.

• Rolling Resistance –

Rolling resistance is the force resisting the motion when a body (such as a 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.

The Rolling resistance can be expressed as –

• Tyre Pressure –

Aircraft tyres are generally operated at high pressures up to 200 Psi (16 Bar, 1400 Kpa) for airliners and even higher for business jets.

The main landing gear on the Concorde was typically inflated to 232 Psi whilst the tail bumper gear tires were as high as 294 Psi (20.3 Bar). The high pressure and the weight load on the Concorde tyres were significant factors in the loss of the Air France Flight 4590.

Tests of airliner aircraft's tyres have shown that they are able to sustain pressures of a maximum of 800 Psi (55 Bar, 5500 Kpa) before bursting. During the testing the tyres have to be filled with water in order to prevent the test room being blown apart by the energy that would release by the gas when the tyre bursts.

Aircraft tyres are usually inflated with nitrogen to minimize expansion & contraction from the extreme changes in ambient temperature & pressure experienced during flight. Dry nitrogen expands at the same rate as dry atmospheric gases (Normal air has about 80% Nitrogen), but common compressed air sources may contain moisture which increases the expansion rate with temperature.

The requirement that an inert gas, such as nitrogen be used instead of air for inflation of tyres for certain transport category airplanes are prompted by at least 3 cases in which the oxygen in air-filled tyres combined with volatile gases given off by severely overheated tyre and exploded upon reaching auto-ignition temperature the use of inert gas for tyre inflation will eliminate the possibility of a tyre explosion.

• Brake Forces while Landing –

Aircraft brakes stop moving aircraft by converting its Kinetic Energy to heat energy by means of friction between rotating & stationary discs located in brake assemblies in the wheels. Brakes provide this critical stopping function during landings to enable airplanes to stop within the length of the runway.

Following braking devices are used to decelerate the aircraft –

1. Ground Spoilers.
2. Wheel Brakes (Including Anti-Skid systems & Auto-Brake systems).
3. Thrust Reverser.

Ground Spoilers –

Ground spoilers usually deploy automatically (if armed) upon main-landing-gear-touchdown or upon activation of thrust reversers.

Ground spoilers provide 2 aerodynamic effects –

1. Increased aerodynamic drag contributes to aircraft deceleration.
2. Lift-Dumping increases the load on the wheels and thus increases the wheel braking efficiency.

Wheel Brakes -

Braking action results from friction force between the tires & the runway surface.

The friction force is affected by –

Wheel speed (i.e. Free rolling, skidding, or rocked);

Tyre condition & pressure (i.e. friction surface);

Runway Condition (i.e. Runway friction coefficient);

The load applied on the wheel.

Braking force is equal to the load applied on the wheel multiplied by the runway friction coefficient.

Anti-skid systems are designed to maintain the wheel-skidding factor (also called the slip ratio) near the point providing the maximum friction force, which is approximately 10% on a scale from 0% to 100% locked wheel).

Autobrake systems are designed to provide a selectable declaration rate, typically between three knots/sec. to six knots/sec.

When a low auto brake deceleration rate is selected & the brake pressure is applied usually after a specific time delay to give priority to the thrust reverser deceleration force at high airspeed.

Thrust Reversers –

Thrust reversers provide a deceleration force that is independent of runway conditions. Thrust reverser efficiency is higher at high airspeed therefore, thrust reversers must be selected as early as possible after touchdown (in accordance with standard operating procedures).

Thrust reversers should be returned after reverse idle at low airspeed (to prevent engine stall or foreign object damage) & stowed a taxi speed. Nevertheless, maximum engine speed can be maintained to a complete stop in an emergency.

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

Let’s assume

Weight of the Aircraft (Airbus A-380) = 575000 kg.

Rolling Resistance Coefficient of an Airbus (_rr) = 0.004.

Weight of the towing tractor = 50000 Kg.

Rolling Resistance coefficient of the towing tractor (_rr) = 0.001

Rolling Resistance force of the towing tractor = _rr * m.g = 0.001*50000*9.81 = 0.49 KN.

Rolling Resistance force of an Aircraft = _rr * m.g = 0.004*575000*9.81 = 22.56 KN.

Total Rolling Resistance Force = Rolling Resistance force of an Aircraft + Rolling Resistance force of the towing tractor

= 0.49 + 22.56

= 23.05 KN.

Air-Drag Force –

It is the force that occurs due to the Air Strike effect on the wheel when it moves. The vehicle moves through the air medium of a particular density value with a certain speed this causes the airstrike against the vehicle body & it causes Drag force on the vehicle.

The Aerodynamic Drag is given by the following equation –

ρρ= Density of the air medium.

A = Frontal area of the vehicle which strikes the vehicle.

V = Velocity with which the vehicle moves.

C_{d =} Coefficient of Drag which varies different shapes of the frontal area.

Let’s assume

The Velocity of the Aircraft while Towing = 30 Kmph. (8.33 m/s)

The density of Air medium (ρρ) = 1.225.

The frontal area of the Aircraft = 20 m².

The coefficient of the Drag of the Aircraft = 0.026.

Air Drag Force = 0.5*ρρ*A*V²* C_d = 0.022 KN.

Air Drag Force of the Aircraft = 0.022 KN.

Therefore,

The Total Force that the motor needs to overcome = Total Rolling Resistance Force of an Aircraft + Drag force acting on the Aircraft.

Hence, the Total Force acting = 23.05 + 0.0022

The Total Force that the motor needs to overcome in order to push or pull the Aircraft = 23.07 KN.

The Power required –

The power required by the motor is given by the velocity with which the towing operation takes place.

The average speed of Push/Pull = 20Kmph.

Power required by the motor = Total Force * Velocity = 23.07 * 5.5 = 126.8 KW.

Power required by the motor= 126.8 KW.

The torque output of the Towing Tractor can also be calculated by the following steps –

F_te = The Total Tractive Force 9Rolling Resistance Force + Air Drag Force.

T = Torque Output.

r = Radius of Tyre.

G = Gear Ratio.

For heavy-duty Towing Tractor, we assume –

G = 11 (for delivering high torque)

r = Radius of Tyre = 25 inches = 0.635 m.

The Torque required to Push or Pull for above-stated condition = 1.327KNm.

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

Simulink Model:

• constant blocks are used to feed the parameters such as mass, coefficients and other parameters using product block the resistive forces are calculated.
• using sum block, total resistive forces can be calculated.
• the outputs are visualized using display blocks.

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

B. Also, Design the parameters in excel sheet.

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

Estimation of Duty Cycle:

Based on the calculation done in study 6

The Power Required for towing of the aircraft is 45.26kW.

Motor Considred for the drive train is REB 90

Technical Data:

Type	Voltage	Continuous / Peak power	Working rotation	Max torque	Weight	Cooling
REB 90	400–800 V	60–70 kW / 80 kW	1 500–4 000 rpm	300 Nm	22 000 g	Air / Hybrid (air + fluid)

Considering 60kW as continuous power, so the voltage will be 400V

Battery power is considred to be 550v

Duty cycle is given by VoVbVoVb

where Vo is motor required voltage

Vb is battery voltage.

d=400550⇒0.7272d=400550⇒0.7272

As there will be losses due to the resistance of FET and Inductance.

Correction factor is considred to be 90%

As there is 10% loss, the voltafge demanded by the motor should be 10% more than required

d=0.7272⋅(1+0.1)=0.799≈0.8d=0.7272⋅(1+0.1)=0.799≈0.8

so the voltage demand should be around 440V from the battery.

Assumed Parameters
Mass of aircraft	575000	kg
Mass of the push back truck	1000	kg
Coefficient of Rolling Resistance	0.002
Drag Coefficient	0.025
Air density	1.125	kg/m^3
Frontal Area	150	m^2
Velocity	4	m/s
Uphill gradient	0	deg
Battery Voltage	550	V
Correction Factor	0.8

Block Diagram:

Simulink Model:

Input:

Output:

From the motor:

From the Battery:

B. Also, Design the parameters in excel sheet.