Project-1: Powertrain for aircraft in runways

Part A:-

Overview:- 

What are air crafts and which are types of aircrafts, you know? Most of us will only answer the common ones – airplanes and helicopters. Well, yes, you are not wrong. Airplanes and helicopters are the most common types of aircrafts we may know. But what you may miss out on are different and several other categories in aircraft that you may not know.

From helicopters to gliders to cargo planes, fighter jets, balloons, and more, there are numerous other aircraft types and categories we must all know. Let’s find and learn all about them today

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

Introduction:-

Any vehicle that is manufactured and made to fly in the air is called an aircraft. While the airplane is the most known, familiar, and popular kind of aircraft we know, other vessels that fly through the air also come in this category. All of them have propellers and wings or machinery to run through the air; however, they may vary according to sizes, types, usage, and more.

Classification of Air crafts:- 

Before we get into knowing and studying different types of aircrafts, let us understand how are these aircrafts classified. In most common terms, there are two types of classifications for aircrafts. One is lighter than air aircrafts, known as aerostats, and the other is heavier than air aircrafts, called aerodynes.

Aerostats (Lighter Than Air): Aerostats or lighter than air aircrafts are very more lightweight in weight. These types of light aircraft generally use buoyancy like ships, which help them float in the air. Low-density gas such as hydrogen, helium, or hot air balloons is used to fill in the aircraft. This low-density gas is lighter than air, and hence the name. The most common types of aerostats known to us are hot air balloons and sky lanterns.

Aerodynes (Heavier Than Air): Alternatively, the other aircraft, heavier than air or aerodynes, as we understand, is much higher in weight and size. They push the gas or air downwards; which reaction helps to make aircraft upwards. Since these are dynamic through movements in the air, they are called aerodynes. This dynamic lift through the air can be caused mostly through mechanisms, as you must have already known.

• One is the fixed-wing classification, just like planes. In this category of fixed-wing aircraft, the entire mechanism is relied upon forward speed to create airflow all over wings.
• Another mechanism is rotorcraft, which uses spinning rotors that are like wings. The helicopter is the most commonly known aircraft under this classification.

Types of Aircraft in the world:-

To understand:

1. Why every gram being loaded on the aircraft is weighed with scrutiny?
2. Why do pilots sometimes dump fuel ?

In an aircraft, the centre of gravity (CG) is the point about which the aircraft would balance when it is suspend by that point. As the location of the centre of gravity affects the stability of the aircraft, it must fall within specified limits that are established by the aircraft manufacturer. Both lateral and longitudinal balance are important, but the primary concern is longitudinal balance; that is, the location of the CG along the longitudinal or lengthwise axis

From “Manufacturing” to “Commissioning” and from “On the Ramp” to “Take-off” there are huge variations in the weight and balance of an aircraft. It varies significantly, so striking a correct balance with all loads on an aircraft is significantly important.

Prerequisites:

• Weight of a male person – 88 kg (avg)
• Weight of a female person – 70 kg (avg)
• Weight of children (2-12) years – 35 kg (avg)
• Weight of cabin crew – 75 kg (including 3kg of crew baggage) (avg)
• Weight of fuel in aircraft can be approximated as approx 12000 kgs for 4000 km by an narrow body aircraft (A-320).
• Payload – Passengers, Cargo, Mail, Baggage. (mainly)

Let’s take these weights one by one.

1. Manufacturer’s Empty Weight (MEW): It is the weight of the aircraft “as built” and includes the weight of the structure, power plant (engines), furnishings, installations, systems and other equipment that are considered an integral part of an aircraft.
2. Zero Fuel Weight (ZFW): This is the total weight of the airplane and all its contents including unusable fuel (unusable fuel is the fuel which is required to maintain the structural stability of the aircraft, especially wings), but excluding the total weight of the usable fuel on board (usable fuel is the fuel necessary for the flight). Note: As a flight progresses and fuel is consumed, the total weight of the airplane reduces, but the ZFW remains constant.
3. Operational Empty Weight (OEM) or Dry Operating Weight (DOW): It is the basic weight of an aircraft including the crew, all fluids necessary for operation, (such as engine oil, engine coolant, water, unusable fuel) all operator items and equipment required for flight but excluding usable fuel and the payload.
4. Maximum Zero Fuel Weight (MZFW): Maximum zero fuel weight (MZFW) is the maximum weight allowed before usable fuel and other specified usable agents (engine injection fluid, and other consumable propulsion agents) are loaded. OR (OEM / DOW + Payload = MZFW)
5. Maximum Taxi Weight (MTW) or Maximum Ramp Weight (MRW): It is the maximum permitted weight of the aircraft at which it may be moved on the ground either with its own engine or towed by a tractor. It can also be defined as maximum weight for ground maneuvering including the weight of run-up and taxi fuel. (MZFE + Ramp Fuel = MRW)
6. Maximum Take-Off Weight (MTOW): It is the maximum permitted weight at the start of the take-off. While determining this limit, the manufacturer takes into consideration the strength of the material used for the manufacturing of the aircraft and standard performance variables such as runway temperature, altitude, atmospheric pressure, wind components, flaps, etc. (MZFW + Take-Off Fuel = MTOW)
7. Regulated Take-Off Weight (RTOW): As told in the above definition depending on different factors (e.g. flap setting, altitude, air temperature, length of runway), RTOW or maximum permissible takeoff weight varies for each takeoff. It can never be higher than MTOW. 
8. All Up Weight (AUP): DOW + Payload + Fuel.
9. Maximum Landing Weight (MLW): When aircraft touches the ground it puts force of the runway as well as on the tyres and under carriage, so to ensure structural safety of the aircraft MLW is taken into consideration. Manufactures have calculate this force to be approximately “9” times the weight of the aircraft. Thus when the aircraft has to make an emergency landing or when the weight of the aircraft before landing exceeds the MLW defined by the manufacturer the pilots dump fuel to reduce the weight of the aircraft. (MTOW – Trip Fuel = MLW)

We hope that now you have got an understanding of why each and every baggage is weighed before it is loaded on the aircraft which is not the case when you travel by train. So next time you try to negotiate kgs with the airline staff remember its not that the staff is being insensitive and but you are trying to compromise on your safety.

To enhance your understanding have a look at the problem below:

1. Assume:

• Avg Passenger Weight – 77 kgs
• Avg Baggage Weight – 20 kgs

2. Given Data:

• DOW – 46000 kgs
• TOF – 15000 kgs (Take-Off Fuel)
• ZFW – 62500 kgs
• MTOW – 77000 kgs
• LW – 66000 kgs (Landing Weight)
• TF – 10000 kgs (Trip Fuel)

Find the maximum allowable load (payload) and the underload of the aircraft?

Sol. First we will try to find Operating Weight (OW is not a standard weight defined but is required for the calculations performed) . So, according to the problem given we can find operating weight using the following three methods:

a. DOW+TOF = OW(1) = 46000+15000 = 61000 kgs

b. ZFW+TOF = OW(2) = 62500+15000 = 77500 kgs

c. LW + TF = OW(3) = 66000 + 10000 = 76000 kgs

Now in order to find the maximum allowable payload we will choose the minimum OW and proceed further, which is OW(1).

Now question says to find the Allowable Load (payload). So, MTOW – OW(1) = Payload (1) = 77000 – 61000 = 16000 kgs.

Where Payload (1) is the maximum allowable payload on the aircraft.

If we consider a scenario that the flight has 120 passengers, 600 kgs of Cargo and 600 kgs of Mail. Then,

• Passenger Weight = 120 * 77 = 9240 kgs
• Baggage Weight = 20 * 120 = 2400 kgs
• Cargo Weight = 600 kgs
• Mail Weight = 600 kgs

All of the above cumulates to the Payload (2) = 12840 kgs

Now, Paylaod (1) – Payload (2) = 16000- 12840 kgs = 3160 kgs (Under load)

This means the flight still can accommodate 3160 kgs more.

Objective 2:- Is there any difference between ground speed and air speed?

There are two different types of speed when talking about airplanes – ground speed and airspeed. While ground speed is the airplane’s speed relative to the surface of the Earth, airspeed – at least true airspeed – is its speed relative to the air it is flying in. Below, I will explain the two types of speed in more detail, as well as talk about the four types of airspeed that are commonly used.

Air speed Vs Ground speed

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

Wind's effect on ground speed

The relationship between airspeed and ground speed is fairly simple. Ground speed is simply the sum of airspeed and wind speed. If the aircraft is flying in the same direction as the wind is blowing, the aircraft experiences tailwind, and its ground speed is higher than its airspeed. On the other hand, if the wind is blowing against the direction the aircraft is traveling in, the aircraft experiences headwind, and its ground speed is lower than its 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.

On a perfectly still day, the airspeed 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.

Examples

Suppose we had an airplane that could take off on a windless day at 100 mph (liftoff airspeed is 100 mph). We are at an airport with an east-west runway that is 1 mile long. The wind is blowing 20 mph towards the west and the airplane takes off going east. The wind is blowing towards the aircraft which we call a headwind. Since we have defined a positive velocity to be in the direction of the aircraft's motion, a headwind is a negative velocity. While the plane is sitting still on the runway, it has a ground speed of 0 and an airspeed of 20 mph:

The airplane starts its take off roll and has a constant acceleration a. From Newton's second law of motion, the ground speed V at any time t is:

and the distance d down the runway at any time is:

For a fixed length runway, this specifies the time to be used in the velocity equation. Let's assume that at 5000 feet down the runway, the velocity is 80 mph. Then the airspeed is given by

and the airplane begins to fly. Now another pilot, with exactly the same airplane decides to take off to the west. The wind is now in the same direction as the motion and this is called a tailwind. The sign on the wind speed is now positive, not negative as with the headwind. The acceleration along the ground is the same, so at 5000 feet down the runway, the ground speed is again 80 mph. The airspeed is then given by:

This airplane doesn't have enough airspeed to fly. It runs off the end of the runway.

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

When you arrive at the gate for your flight, more often than not you’ll get a great view of the nose of the aircraft through the terminal window. If you look closely, you’ll be able to see us pilots preparing the aircraft for departure. Funny enough, we can see you peering out at us too, so if we wave, don’t be embarrassed to wave back.

However, the obvious problem with parking facing the terminal is that in order to get to the runway, we need to move backward off the stand first. If this was on your drive at home, you’d just pop your car into reverse, back out onto the street and off you go. Unfortunately, aircraft are unable to do this as they don’t have a reverse gear. In order to get round this problem, we use the assistance of a pushback tug.

Airplanes get towed or pushed by tractors and tugs when jet blast from their engines or prop wash from their propellers will create a hazard to nearby buildings, ground crew, other aircraft & ground handling equipment. Moving aircraft from hangers to aprons does not require pilots if being towed.

Depending on the airport, some aircraft movements have to be made with assistance to ensure the safety of all those working in the area or when the need to start the engines is overkill for the maintenance task required.

Why do Airplanes get towed?

1) Airplanes get towed when the thrust of their engines creates a significant hazard to the immediate area surrounding them. Planes also get towed for maintenance purposes so pilots are not required to move the aircraft as airplane mechanics are trained in the use of the aircraft brakes while towing.

2) When aircraft go in for maintenance or are not required for flight by far the easiest way is to send a tow vehicle to the gate and have the maintenance team tow the aircraft to the hanger or parking areas. By doing this it allows time freedom for the airline, the airport ground controllers, and the maintenance team as pilots are not required to start the engines.

5)- Another reason you might see or experience being towed is when your aircraft has to be towed from the taxiway to the gate. This will be due to the tight confines of the terminal gates and the restricted view the pilots have may require a tow to conduct the arrival safely. As airplanes become larger and airports get busier you may see this quite often.

6)- Even though pilots follow taxi centerlines, airplanes with very large wingspans could create tight spots and any contact made between two aircraft can cause significant damage, lost time, and potentially huge costs, so a simple tow helps prevent this.

Objectice 4:- How an aircraft is pushed to runway when its ready to take off?

What vehicle Tow Airplanes

Depending on the size of aircraft to be towed the tow vehicle can be as small a quad and be as large as a bus. The heavier the aircraft is to be moved, the heavier and more power the tow vehicle has to have. Dedicated tractors or tugs are used to hook onto the airplanes to allow for controlled tows.

A fully loaded Airbus A380 can weigh in excess of 575,000 kg or 575 tonnes! To get that mass moving in reverse requires a serious powerhouse of a vehicle. Commonly referred to a Tractors or Tugs, these workhorses can be seen working at every major airport around the globe.

Towbarless Tug:-

Becoming more popular around the large airports is the Towbarless Tug. These tractors are purposely designed to be able to move any aircraft without the need for any additional apparatus like a towbar.

These Tugs come in a range of sizes to suit all of the larger aircraft flying today and they are heavy, powerful, moving machines,

They work by having the driver reverse up to the nose landing gear of the airplane. The airplane’s front tires are then placed against a stop and a bar or locking arm closes in around the other side of the plane’s tires. Once secured, the Tug will lift the entire landing gear tires off the ground.

This then allows the Towbarless Tug to easily move the airplane around once the pilot/s have released the brakes.

and due to their speed at moving aircraft, they are a popular choice among ground crews and airport ground controllers.

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

 In order to understand the part this 35 feet screen height plays in the takeoff, we first need to look at the various distances that affect the take off performance of an aircraft.

TAKE OFF RUN AVAILABLE:- 

The TORA is the distance from the point at which the aircraft can start its takeoff run to the point at which the the surface can no longer bear its weight. In most cases, this is equivalent to the length of the runway.

THE CLEARWAY:-

This is an area at the end of the TORA that is free from any obstructions exceeding 0.9 meters in height like buildings or trees. The aircraft can use this area in order to achieve the 35 feet screen height.

The clearway may not be immediately obvious, as it is not defined by a paved surface. It can include an area of open ground or even water, so long as it is under the control of the airport. When you add the clearway to the TORA, this gives you the

TAKE OFF DISTANCE AVAILABLE:-

The TODA is the total distance that the aircraft has to start its takeoff run and climb to the 35 feet screen height. On a runway without a Clearway, the TODA will equal the TORA.

ACCELERATED-STOP DISTANCE AVAILABLE:-

The final distance that must be considered for takeoff performance is the ASDA. This is the distance of weight bearing surface available to the aircraft to accelerate and then come to a safe stop in the case of a rejected takeoff.

In order to operate within the TODA, the takeoff speeds must be as slow as possible. This is why flaps and slats are used on take off. They increase the lift generated by the wing, allowing the aircraft to get airborne at a slower speed.

THE ENGINE FAILURE SECNERIO:- 

On a twin engine aircraft such as the 787 Dreamliner, the loss of power from one engine during the takeoff run is one of the more serious events that could happen. Although this is highly unlikely, we always plan for the worst possible scenario. This is where the performance for the 35 feet screen height comes in.

Should an engine fail just as the aircraft lifts off, the performance must still ensure that it reaches the screen height by the end of the TODA on the power of the remaining engine. This is the key part of the takeoff performance.

Even though an aircraft can safely climb away from the runway on just one engine, should the failure happen whilst still on the ground, it would be preferable for the pilots to reject the takeoff and stop on the runway. However, there comes a point where there will not be enough runway remaining in which to stop safely. So how do we know where this point is?

Before every takeoff, the pilots must calculate the speeds, flap setting and engine power required to takeoff safely. This includes the engine failure scenario.

One of the speeds that is calculated is called V1 — “the maximum speed in the takeoff at which the pilot must take the first action to stop the aeroplane within the accelerate-stop distance”.

If an event occurs before the aircraft reaches the V1 speed, the pilots know that they are able to stop safely. Any events occurring after V1, the pilots must continue to get airborne. The decision to stop or go isn’t made in the heat of the moment — it’s a binary decision calculated at a time of low workload.

AIRCRAFT PERFORMANCE BY EVERY FLIGHT:- 

The figures mentioned above vary from flight to flight, day to day and are affected by a number of variables. All these must be taken into consideration by the pilots when planning their takeoff performance.

AIRCRAFT WEIGHT:- 

The most obvious element in this equation is the weight of the aircraft. Just like in your car, the heavier the aircraft is, the slower it will accelerate. If you were to increase the weight of the aircraft, eventually you’d reach a weight at which it could no longer accelerate to the required speed before running out of runway.

Heavier weights also require more lift to fly. In order to generate this lift, the aircraft has to be traveling faster.

RUNWAY SLOP:- 

Another fairly easy factor to understand is that if the runway is sloping upwards, it will naturally take longer for the aircraft to accelerate to the speeds required for flight.

The hotter the air temperature, the lower the air density. Because the engines rely on moving air backwards to accelerate the aircraft forwards, when the air density is low, less air is moved backwards by the engines. This results in less thrust being available and a longer takeoff run being required.

WIND:-

Aircraft like to takeoff into a head wind. With a stronger wind over the wings, the aircraft doesn’t have to be moving as fast over the ground to reach the air speed required to lift off. This means that less runway is required.

Conversely, if there was a strong wind from behind the aircraft, the takeoff distance required would be much greater.

AIRFIELD PRESSURE ALTITUDE:- 

The higher the pressure altitude, the lower the air density. When the air density is low, not only is thrust reduced (as mentioned above) but there are fewer air molecules flowing over the wing at a given speed. This results in less lift. The higher the pressure altitude, the greater the takeoff distance required.

RUNAWAY CONDITION:- 

One of the less obvious aspects, the condition of the runway can affect the drag on the wheels. The greater the drag, the slower the acceleration, the greater the TOD required. Careful assessment by pilots of the current and potential future runway conditions is essential to ensuring a safe departure.

TODA:-

The final element that can affect the performance calculations is the TODA. As mentioned before, the aircraft must clear any obstacles in the climb out by at least 35 feet. The shorter the TODA, the higher the power and more flap setting will be needed.

REDUCED THURST TAKE-OFF:-

The engines on modern jet aircraft are so powerful that very rarely is full power required to get airborne. The harder the engines work, the more fuel they use, the sooner they need servicing and the more noise pollution they create. If you can reduce the power used on takeoff, the engine life will be increased and residents around the airport will be subject to less noise. This is called a reduced thrust takeoff. This is managed by making maximum use of the TODA. Why get airborne 2 kilometers down a 4 kilometer runway when you could use more of it and save some engine power?

THE TAKE-OFF DATA:- 

Depending on the aircraft, it can take a couple of minutes to calculate the data. The 787-9 and 787-10 tend to take a little longer than the 787-8, as there are more takeoff flap setting options. Once the calculations are complete, the OPT displays the figures for flap setting, engine power and takeoff speeds that will be used for takeoff.

Once both pilots have a set of figures, it’s time to check them. One pilot then reads exactly what their OPT has calculated. The other pilot checks that they have exactly the same figures on their screen.

If there are any errors, both pilots must work out why they have different figures. This is often due to one side having a different OAT or QNH setting to the other side. Once the discrepancy has been resolved, the whole process must be completed again. This ensures that no errors slip through.

Once both pilots have confirmed that their numbers tie up, it’s time to load them into the FMC. As the OPT calculations are independent, one pilot sends their numbers to the FMC and once loaded, the other pilot then checks the FMC numbers against their calculated OPT numbers. Yet another chance to catch any errors.

Once the data has been loaded and checked and the auto flight modes for takeoff have been selected, the procedure is complete. All that is left now is to complete a departure briefing and complete the checklists.

(B)-Why aircraft tyres are important:- 

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

An aircraft tyre is designed to withstand extremely heavy loads while landing, take off, taxing, and parking. The number of wheels required for aircraft increases with the weight of the aircraft, as the weight of the aeroplane needs to be distributed more evenly.

Design and construction of tyre:- 

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

1. They support the weight of an aircraft while it is on the ground.
2. It also provides the necessary traction for braking and stopping of an aeroplane.
3. Tyre also helps to absorb the shock of landing and provide cushioning the roughness of takeoff, roll-out, and taxi operations.

Unlike an automobile or truck tyre, it does not have to carry a load for a long period of continuous operation. However, an aircraft tyre absorbs the high impact loads of landing, and also it’s operating at high speeds for a short time when required.

Retreading:- Retreading is methods of restoring a worn tyre by renewing the tread area or by renewing the tread area plus one or both sidewalls. Repairs are included in the tyre retreading process.

Load Rating – Load rating is the maximum permissible load at a specified inflation pressure.

Ply Rating – Ply Rating is used to identify the maximum recommended load rating and inflation pressure for a specified tyre. It is an index of tyre strength.

Speed Rating – The speed rating is the maximum takeoff speed to which the tyre has been tested.

Skid Depth – Skid depth is the distance between the tread surface and the deepest groove as measured in the mould.

Aircraft tyres must have an approved speed and load rating and have sufficient clearance when retracted through landing gear to allow for tyre growth. Tyre growth is the increase in the size of the tyre due to centrifugal forces at high speed.

Aircraft tyres may be tube type or tubeless:-

Tubeless tyres are more advantageous over tube-type. There is no longer the use of tube-type tyre in recent aviation. Nowadays all airliners are using tubeless tyres. Tubeless that are meant to be used without a tube has the word TUBELESS on the sidewall of the tyre.

Aircraft tyres may be radial or bias:- 

 The tires themselves aren't terribly large--- a Boeing 737 rides on 27x7.75 R15 rubber. In English, that means it is 27 inches in diameter, 7.75 inches wide, and wrapped around a 15-inch wheel. The sidewalls aren't terribly thick, and the strength of the tire lies in the cords embedded below the tread, Bartholomew says. They're typically nylon, and more recently a variety known as aramid. Each layer of the casing contributes to its load bearing and air pressure resisting capabilities. Of course, tires can fail, especially when under-inflated or overloaded. Treads can come off and casings can blow out.

In the first moments after a plane touches down, the tires are skidding, not rolling. The airplane essentially drags them down the runway until their rotational velocity matches the velocity of the plane. That's why they smoke upon landing, and why Michelin uses grooves instead of the block patterns seen on your car's rubber---blocks would simply break off. (Most tire wear comes from this moment of contact---where the rubber meets the runway.) The stoutest tires are rated for speeds of up to 288 mph.

To develop a new sort of tire, or test a tweak, Michelin starts with computer simulation, followed by prototyping. Then it tests how the tires do when they're overloaded or pushed past their speed limit, on simulated takeoffs, landings, and taxiing. Like everything in aviation, tires must meet specific and demanding rules---for example, a tire must withstand four times its rated pressure for at least three seconds.

(D) Brake forces:- 

Airplanes rely on a braking system to safely land on runways. At cruising altitude, most commercial airplanes fly at a speed of roughly 500 to 600 mph. When landing, however, they must reduce their speed. A typical 747, for instance, has a landing speed of about 160 to 170 mph. And upon touching the runway, airplanes must quickly brake until they come to a complete stop. How do airplanes brake when landing exactly?

WING SPOILERS:- 

Many airplanes use wing spoilers to assist with braking when landing. Not to be confused with ailerons, spoilers are extendable flaps on the ends of an airplane’s wings. Pilots can raise the spoilers to decelerate the airplane as it approaches the runway. And even while on the runway, pilots will typically leave the wing spoilers raised. Raised wing spoilers create drag, which essentially slows down the airplane so that it’s able to brake more quickly.

DISC BRAKES:-

In addition to wing spoilers, airplanes use disc brakes. Airplane disc brakes are similar to the braking system in automobiles. They consist of a pair of calipers that, when engaged, squeeze pads against the rotors of an airplane’s landing gear.

Disc brakes are designed to remain static at all times. In other words, they don’t rotate with the wheels of an airplane’s landing gear. As the wheels turn, the disc brakes will remain static and stationary. They are a vital component of an airplane’s braking system because they are designed to apply pressure to the airplane’s wheels. Disc brakes will squeeze the wheels, thereby slowing down the speed at which they spin. In turn, this reduces the speed of the airplane so that it can come to a complete stop on the runway.

REVERSE THURST:-

Finally, many jet airplanes use reverse thrust to assist with braking during landings. Reverse thrust is a feature in jet engine airplanes that, as the name suggests, involves the reversal of the engines’ thrust. When flying, the thrust is projected out the rear of an airplane’s engines. When landing, however, pilots may use the reverse thrust feature. Reverse thrust changes the direction of the engines’ thrust. Rather than projecting out the rear, the thrust will be projected out the front. This reversal of thrust provides deceleration that allows airplanes to slow down more quickly when landing.

Part B:

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

Result:-

Let us assume

Total mass of the Air craft including pay load= 580000Kg

Mass of the Towing vehcile= 1000Kg

Coefficient of Rolling Resistance μr= 0.002

Rolling Resistance force is given by Frr=μr*m*g

= 0.002*580000*9.81

Frr = 11.396KN

Power of rolling resistance Prr= 11396 x 4.02

= 45.824KW

So we can say that Frr of Towing vehicle is very less as compared to Aircraft Frr.

Drag Coefficient(Cd)= 0.025

Air density(P)= 1.125Kg/m^3

Frontal area(A)= 150m^2

Velocity(v)= 14.5KmPh=4.02m/s

Aerodynamic force Far= 1/2*Cd*P*A*v^2

1/2*0.025*1.125*150*(4.02)^2

Far = 34.09N

Power of Air drag force Pad= 34.09 x 4.02

Pad= 0.137Kw

Therefore total Power required by the Towing vehicle to move the aircraft over the runway

Pw = 45.97KW

Total Power required by the Towing Vehicle= 45.97KW

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

To the reference of the above values and formulas i have implemented this graph. And as per formula i have taken sone constant for mass, velicity, rolling resistance etc.

To calculate Frr and Fad calculate the total force and then use product block to calculate the total power to use towing vehicle to move the aircraft.

Model link:- https://drive.google.com/file/d/1NDIdrxmOBk7BKNDXxqeiNPEnYkRZ4CFi/view?usp=sharing

Objective 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. 

(Hint :DC7 Block)

Result:- From the 6th question we can assume the Power requirement for the motor is= 45.97KW.

This is the motor output power= 45.97KW

For the calculation of Duty cycle we required input power also.

Input power= Output power+Losses

Let us assum the motor efficiency is 90%.

Efficiency= Output power/Input power

0.90= 45.97/Input power

Input power= 51.0KW

So for this application we required approx 51KW motor rating

The energy required to operate this motor for 1 hour will be

Energy = 51.0 x 3600= 183.6KWh

Duty cycle= Output power/Input power

= 45.97/51.0

= 90%

Assumed parameters are:- 

1)- Total mass of the Air craft including pay load= 580000Kg

2)- Mass of the Towing vehcile= 1000Kg

3)- Coefficient of Rolling Resistance μr= 0.002

4)- Drag Coefficient(Cd)= 0.025

5)- Air density(P)= 1.125Kg/m^3

6)- Frontal area(A)= 150m^2

7)- Velocity(v)= 14.5KmPh=4.02m/s

Block diagram of Power train model

Here we have DC7 model which is Four quadrant chopper model:-

Description:-

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 behaviour, 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.

Simulation:- 

Before starting the simulation, set the initial bus voltage to 515 V via the GUI block ('Initial States Setting' button and 'Cbus' variable).

Start the simulation. You can observe the motor armature voltage and current, the four IGBT pulses and the motor speed on the scope. The current and speed references are also shown.

The motor is coupled to a linear load, which means that the mechanical torque of the load is proportional to the speed.

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 in order 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.

Here we have the controller port for different parameters.

Here we have the converter measurment. 

This model below represent the Power train model where we several block which has their different use. In general the power train model has consist its battery source so i have implemented the battery source over there. 

Battery block discription:- 

(B) Also, Design the parameters in excel sheet.

Excel link:- https://docs.google.com/spreadsheets/d/1iC7ixT9acQd-CFeZYFwyb8ZnoCHC5y-c/edit?usp=sharing&ouid=106212002416908008160&rtpof=true&sd=true