Challenge

Project-1: Powertrain for aircraft in runways

SSanjay Kumar S9 Jun 2021

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

The total weight of aircraft is found by summing up a different type of weight in an airplane. The different types of weight in aircraft are

1) Standard Empty Weight

2) Zero Fuel Weight

3) Operating Empty weight

4) Payload

5) maximum take off weight

6) maximum landing weight

7) maximum ramp weight

Standard Empty Weight:

It is standard weight of aircraft when it is completely built. It consists of all the weight of the body of the plane, structure member, internal parts, and other applications also. It doesnot consider wieght of passenger, baggade, etc.

Zero Fuel Weight:

It the weight of aircraft which considers all weights including unusable fuel weight but it does not consider usable fuel weight because when the aircraft starts operating the usable fuel is consumed and its weight is reduced. The zero fuel weight remains constant even when aircraft is operating.

Operating Empty weight:

Its weight is equivalent to the empty weight of aircraft but it will include some of the additional equipment needed for aircraft and all other stuff too, but it aslo does not inculde usable fuel weight.

Payload:

This is the weight of the aircraft which includes the weight of passengers, baggage, cargo, etc. From this we can find how much weight that the aircraft can carry.

Maximum take-off weight

It is the maximum limit weight for taking off of aircraft. So if the weight of the aircraft goes beyond this weight then it is not advisable to take off the aircraft.

Maximum landing weight

This is the maximum weight of the aircraft which is permitted while landing in airport. If aircraft land beyond this weight then it may cause some damage to the body or structure of the aircraft.

Maximum ramp weight

This is the maximum weight of the aircraft permitted while taxiing the aircraft this includes all weight of aircraft and taxi too.

The above image is the list of some different types of aircraft with the list of weights like Maximum take-off weight, maximum landing weight.

2) Is there any difference between ground speed and air speed?

Yes there is difference between air speed and ground speed

Ground speed: It is the speed which is measured relatively with ground when air craft is flying

Air speed: This is the speed which is measured in aircraft while its flying in air

For example, we can use the above image to know about this concept

In case 1: when the air speed of the aircraft is 120knots which is the same as the ground speed which is measures relatively with the ground so it will reach the same distance while travelling on the ground also.

In case 2: We can see that aircraft experiencing tail wing condition which makes aircraft fly few more ditance so the airspeed of the aircraft is higher than ground speed and the distance travelled in the air will be higher than the ground.

In Case 3 : We can see that aircraft is experiencing head wind condition which reduces the distance travelled by aircraft so the speed ground speed will also be less and is requires les speed to reach same distance while travelling in ground

GS - ground speed

TAS - True air speed

during tail wind condition:

GS = TAS + wind condition

During head wind condition:

GS =TAS - wind condition.

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

It is recommended to use aircraft engine power to move it on the ground at Airport beacuse it may cause some damage and to reduce the fuel consuption and power loss during moving in the ground. Aircraft might have the capability to move on the ground but it is not advisoble, even the aircraft can move backwards by itself on engine power and reverse thrust but it may result in some damage in the aircraft or airport terminal. So in such cases pushback trucks is used. The main work of pushback trucks is to carry the front wheel of aircraft and it will help to move aircraft forward reverse. The reason why its is used is the driver of towing truck or pushback truck have a better vision of airport terminal than the pilot of the aircraft and also power consumption is reduces, and damage occurs due to collidal of aircraft is reduced. This is used to tow the airplane to taxiing path or to pushback the aircraft from the passenger terminal and guide it to runway.

In the above picture we can see the how pushback or towing truck is used.

4) How an aircraft is pushed to runway when its ready to take off

There are three majot steps that aircraft follow before its take off

1) Pushback from terminal

2) Towing

3) Taxiing

Pushback from the terminal:

As we discussed earlier even though the aircraft can move backwards by itself on engine power and reverse thrust but it may result in some damage in aircraft or airport terminal. So in such cases pushback trucks is used. The main work of pushback trucks is to carry the front wheel of aircraft and it will help to move aircraft forward reverse.

Towing:

Towing is direct opposite to pushback of truck. Towing is used for forward movement of aircraft without its engine power. So after pushback from aiport terminal aircraft need to be towed for some distance so in such cases the front wheels of aircraft are carried by towing truck and it pulls the aircraft in forwarding motion.

The reason why towing and pushback is used is the driver of towing truck or pushback truck have a better vision of the airport terminal than the pilot of the aircraft and also power consumption is reduced, and damage occurs due to colloidal of aircraft is reduced

Taxiing:

Taxiing is the phase where aircraft moves on the ground but its own engine power without any other equipment like towing trucks. So in the case where aircraft want to reach the runway, it follows a certain path so in that path trucks cannot be used so in those places taxiing is done. So aircraft undergoes taxing for the certain path to reach runway or after landing it also used to get away from the runway and reach the terminal.

After taxiing is done the aircraft reaches runway and takeoff roll is done. It means it aircraft uses engine power and generates power and runs on the runway and it takes off.

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

Take off power:

It is the power required by aircraft to take off from a runway and start to fly. This power is obtained from the engine of aircraft. This take off power has three factors they are Aerodynamic drag, rolling resistance, thrust force. Drag is a force that acts opposites to the direction of motion of aircraft, so if the drag is less we required less power to fly, and if it is more then more power will be required. Rolling resistance is the type of friction force that acts on the wheel when it rolling on the runway. Thrust force is the force obtained from the propulsion system of aircraft which moves aircraft against all opposing forces. By summing up all these forces and factors, we can get the power required for taking off of aircraft.

Tyre Design:

Aircraft types play an important role in absorbing od the shock which is experienced while landing and it provides cushioning effect while landing, it provides the required traction for braking and to stop aircraft, and it is designed in such a way that to support the weight of aircraft for short periods of time.

Types of tyre used in aircraft are:

1) Radial tyre

2) Bias-ply tyre

3) Tubetype tyre

4) tubeless tyre

Radial tyre: These tyres are made with casing material of rubber coated ply cords which is extend around the beads and are at 90degrees to the centerline of the thread.

Bias ply tyre: These tyres are made with casing material of alternate rubber coated ply cords which is extend around the beads and are at less than 90degrees to the centerline of the thread.

Rolling resistance:

Rolling resistance is the resistance acts on the rolling body when it is rolling in the surface, It is the type of friction force that a vehicle should overcome.

Rolling Resistance force `F_(rr)=μ_(rr)mg`

m - total mass of vehicle

`μ_(RR)` - coefficient of rolling resistance

g- gravitational force

The coefficient of rolling resistance depends on tire material, tire pressure, road roughness, road tempurature ect. In aircraft, rolling resistance happens in two cases one is during take-off aircraft and other is during landing of aircraft.

Tyre pressure:

Aircraft tyres are manufactured to operate under high pressure of 14bar or 200psi. The airliners tires are able to sustain the pressure of a maximum of 800psi or 55 bar this data is obtained from testing which is done in tyres of the airplane. Aircraft are usually infalted with nitrogen to minimize expansion and contrcation from extreme changes in tempurature and pressure experience during flight. In aircraft tyre pressure acts in two cases, one is during take-off aircraft and the other is during the landing of aircraft.

In the above image, we can see the relation between rolling resistance and tyre pressure. As we mentioned earlier the value of the coefficient of rolling resistance is related to tyre pressure in the graph we can see that they are inversely propotional. If the value of tire pressure increases the value of rolling resistance decreases. If the value of rolling resistance increases the value of tire pressure decreases.

Brake forces when landing:

Brake system used in aircraft to deceleration of aircraft while landing in runway is

Aircraft disc brake: These brakes are used when the landing gear is applied and that provide brakes in the wheel of the aircraft. Normally, this system is operated by either hydraulic or pneumatic.

Thrust reversal: In this method, the reverse thrust is provided by the propulsion system in the opposite direction of motion of the aircraft while it's landing, so then the aircraft starts to decelerate. This is also called as thrust reversal.

Spoilers: spoilers are the plates that are hinged with the top portion of the wings of aircraft. So when the aircraft landed on the ground these plates are opened and this will provide drag force against the direction of motion of the aircraft. So it will result in deceleration.

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

For so lets us take the Airbus A380-800 for assumption,

Here hill climbing force is not considered becasue it is not travelling in slope and gradiant value is 0.

Rolling Resistance force `F_(rr)=μ_(rr)mg`

Air Drag force `F_(ad)=1/2 ρAv^2 C_d`

Total tractive force`F_(te)=F_(rr)+F_(ad)`

Total tractive power `P_(te) = F_(te) ×v`

m - total mass of vehicle

`μ_(rr)` - coefficient of rolling resistance

A - Frontal area of vehicle

Cd - Drag coefficient

`ρ` - air density

v - velocity of vehicle

The mass of the Airbus A380-800 is - 575000kg

Lets us consider the mass of truck is - 1000kg

So total mass - 575000 + 1000 = 576000kg

coefficient of rolling reistance - 0.005

drag coefficent - 0.6

frontal area - 20 `m^2`

Rolling Resistance force `F_(rr)=μ_(rr)mg`

`F_(rr)= 0.005*576000*9.81`

`F_(rr)= 28252.8 N`

Air Drag force `F_(ad)=1/2 ρAv^2 C_d`

`F_(ad)= (1/2) * 1.225*20*(7^2)*0.6`

`F_(ad)=360.15`N

Total tractive force`F_(te)=F_(rr)+F_(ad)`

`F_(te)= 28252.8 + 360.15`N

`F_(te)= 28612.95`N

Total tractive power `P_(te) = F_(te) ×v`

`P_(te) = 28612.95 * 7`

`P_(te) = 200290.65`w

Total tractive power`P_(te) =200.29 KW`

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

Total mass is found using add block. All the input assumed parameters are included in a constant block. Then rolling resistance force and air drag force is founded using product block based on the formula. Then the forces are viewed in the display block. Total tractive force is found using add block it is also viewed using display block. Then power is found by using product block and divide block based on known formula then it is also viewed using display block.

7)(i) Design an electric powertrain with a type of motor, its 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.

The above image is the Simulink model of the electric powertrain from which we get speed and torque graph

The model consists of solver configuraation block, scope, PS-simulink converter, electrical and mechanical reference, tire and mass block, DC voltage sorce, DC motor, PWM block, and H- bridge block and it has two sensor block they are rotaional motion sensor block and torque sensor block.