Project-1: Powertrain for aircraft in runways

POWER TRAIN FOR AIRCRAFT TOWING VEHICLE IN RUNWAYS

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

The aircraft gross weight (also known as the all-up weight and abbreviated AUW) is the total aircraft weight at any moment during the flight or ground operation.'][2][3] An aircraft's gross weight will decrease during a flight due to fuel and oil consumption. An aircraft's gross weight may also vary during a flight due to payload dropping or in-flight refuelling. At the moment of releasing its brakes, the gross weight of an aircraft is equal to its take-off weight. During flight, an aircraft's gross weight is referred to as the en-route weight or in-flight weight.

The following image depicts take off weight components.

MTOW-Maximum Take off weight

MLW-Maximum Landing Weight

Type MTOW [kg] MLW [tons]

Antonov An-225 640,000 591.7

Scaled Composites Model 351 Strat launch 589,670

Airbus A380-800!'[2] 575,000 394

Boeing 747-8F 447,700 346.091

Boeing 747-8 443,613 306,175

Boeing 747-400ER 412,770 295.742

Antonov An-124-100M 405,060 330

Boeing 747-400 396,900 295.742

Lockheed C-5 Galaxy 381,000 288.41

Boeing 747-200le 377,840 285.700

Boeing 747-300 377,840 260.320

Airbus A340-500 371,950 240

Airbus A340 6007 367,400 256

Boeing 777F 347,800 260.816

Boeing 777-300ER 351,800 251.29

Boeing 777-200LR 347,450 223168…………………… etc

Maximum taxi weight (MTW)

The maximum taxi weight (MTW) (also known as the Maximum Ramp Weight (MRW) is the maximum weight authorized for manoeuvring (taxiing or towing) c aircraft on the ground as limited by aircraft strength and airworthiness requirements. It includes the weight of taxi and run-up fuel for the engines and the APU (Auxiliary Power Unit)

It is greater than the maximum take-off weight due to the fuel that will be burned during the taxi and runup operations

The difference between the maximum taxi/ramp weight and the maximum take off weight (maximum taxi fuel allowance) depends on the size of the aircraft, the number of engines, APU operation, and engines/APU fuel consumption, and is typically assumed for 10 to 15 minutes allowance of taxi and run-up operations

Maximum take-off weight (MTOW)

The maximum take off weight (also known as the maximum brake-release weight) is the maximum weight authorised at brake release for take off, or at the start of the take off roll.

The maximum take-off weight is always less than the maximum taxi/ramp weight to allow for fuel burned during taxi by the engines and the APU

In operation, the maximum weight for take off may be limited to values less than the maximum take-off weight due to aircraft performance, environmental conditions, airfield characteristics (take-off field length, altitude), maximum tire speed and brake energy, obstacle clearances, and/or en route and landing weight requirements

Maximum landing weight (MLW)

The maximum weight authorised for normal landing of an aircraft. The MLW must not exceed the MTOW The operation landing weight may be limited to a weight lower than the Maximum Landing Weight by the most restrictive of the following requirements

• Aircraft performance requirements for a given altitude and temperature landing field length requirements, approach and landing climb requirements
• Noise requirements

if the flight has been of short duration, fuel may have to be jettisoned to reduce the landing weight. Overweight landings require a structural inspection or evaluation of the touch: loads before the next aircraft operation

Maximum zero-fuel weight (MZFW)

The maximum permissible 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 airplane

2. Is there any difference between ground speed and air speed? There is a difference between ground speed and air speed to understand this we should take in to account wind speed too.

Wind Speed

For a reference point picked on the ground, the air moves relative to the reference point at the wind speed Notice that the wind speed is a vector quantity and has both a magnitude and a direction. Direction is important. A 20 mph wind from the west is different from a 20 mph wind from the east. The wind has components in all three primary directions (north-south, east-west, and up-down). In this figure, we are considering only velocities along the aircraft's flight path A positive velocity is defined to be in the direction of the aircraft's motion. We are neglecting cross winds, which occur perpendicular to the flight path but parallel to the ground, and updrafts and downdrafts, which occur perpendicular to the ground

Ground Speed

For a reference point picked on the ground, the aircraft moves relative to the reference point at the ground speed Ground speed is also a vector quantity so a comparison of the ground speed to the wind speed must be done according to rules for vector comparisons

Airspeed

The important quantity in the generation of lift is the relative velocity between the object and the air, which is called the airspeed Airspeed cannot be directly measured from a ground position, but must be computed from the ground speed and the wind speed Airspeed is the vector difference between the ground speed and the wind speed.

Airspeed Ground Speed-Wind Speed

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.

For example taking wind speed as 20 km/hr and runway is east-west runway the wind blowing towards west and the flight runs at 80 km/hr the wind speed acting in the west and the flight takes off east then the

Airspeed Groundspeed(80)- Wind Speed(-20)-100 km/hr

if the planes runs towards west along the wind blowing direction then

the Airspeed-Groundspeed (80) Wind Speed(20)-60km/hr

Hence there is a difference between ground speed and air speed

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

The risks which may arise from engine ground running relate to the potential for loss of control of the aircraft by those persons occupying the pilot seats in the flight deck. Unwanted consequences from such static running are mainly related to those arising from the unintended movement of the aircraft during engine running effectively a loss of control- especially during high power engine running Damage can occur to the aircraft itself, other aircraft nearby or to airside structures

In addition, there is a risk of injury to ground support personnel who may be in relatively close proximity to the aircraft When modern jet engines are operated at rated thrust levels the exhaust wake can exceed 375 mi/h (325 kn or 603 km/h) immediately

aft of the engine exhaust nozzle. This exhaust flow field extends aft in a rapidly expanding cone, with portions of the flow field contacting and extending aft along the pavement surface (fig 1) Exhaust velocity components are attenuated with increasing distance from the engine exhaust nozzle. However, an airflow of 300 mi/h (260 kn or 483 km/h) can still be present at the empennage, and significant people and equipment hazards will persist hundreds of feet beyond this area. At full power, the exhaust wake speed can typically be 150 mi/h (130 kn or 240 km/h) at 200 ft (61 m) beyond the airplane and 50 to 100 mi/h (43 to 88 kn or 80 to 161 km/h) well beyond this point.

The extensive noise arises from the engine power also dangerous for humans and other living things around the vicinity Hence for the above reasons it is not recommended to use engine power to move on the ground.

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

In aviation, pushback is an airport procedure during which an aircraft is pushed backwards away from an airport gate by external power Pushbacks are carried out by special, low-profile vehicles called pushback tractors or tugs.

Although many aircraft are capable of moving themselves backwards on the ground using reverse thrust (a procedure referred to as a power back), the resulting jet blast or propwash might cause damage to the terminal building of equipment Engines close to the ground may also blow sand and

debris forward and then suck them into the engine causing damage to the engine. A pushback is therefore the preferred method to move the aircraft away from the gate.

Pushbacks at busy aerodromes are usually subject to ground control clearance to facilitate ground movement on taxiways Once clearance is obtained the pilot will communicate with the tractor driver (or a ground handler walking alongside the aircraft in some cases) to start the pushback To communicate, a headset may be connected near the nose gear

Since the pilots cannot see what is behind the aircraft, steering is done by the pushback tractor driver and not by the pilots Depending on the aircraft type and airline procedure, a bypass pin may be temporarily installed into the nose gear to disconnect it from the aircrafts normal

steering mechanism

Once the pushback is completed, the towbar is disconnected, and any bypass pin removed. The ground handler will show the bypass pin to the pilots to make it clear that it has been removed The pushback is then complete, and the aircraft can taxi forward under its own power.

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

Take-Off Power

For light aircraft, usually full power is used during take-off, Large transport category (airliner) aircraft may use a reduced power for take-off where less than full power is applied in order to prolong engine life, reduce maintenance costs and reduce noise emissions In some emergency cases, the power used can then be increased to increase the aircraft's performance. Before take-off, the engines, particularly piston engines are routinely run up at high power to check for engine related problems The aircraft is permitted to accelerate to rotation speed (often referred to as V.) The term rotation is used because the aircraft pivots around the axis of its main landing gear while still on the ground usually because of gentle manipulation of the flight controls to make or facilitate this change in aircraft attitude (once proper air displacement occurs under / over the wings an aircraft will lift off on its own controls are to ease that in)

The nose is raised to a nominal 5-15 nose up pitch attitude to increase lift from the wings and effect lift-off. For most aircraft attempting a take-off without a pitch up would require cruise speeds while still on the runway.

Tyre Design:

Based on the type of plies used the tyres can be

Radial ply tires-

these tyres feature a flexible casing which is constructed of rubber-coated ply cords which extend around the beads and are substantially at 90° to the centerline of the tread. The casing is stabilized by an essentially inextensible circumferential belt.

Bias ply tires

these tyres feature a casing which is constructed of alternate layers of rubber coated ply cords which extend around the beads and are at alternate angles substantially less than 90° to the center

tine of thead

Based on the method for containing the inflation gas the tyres can be:

• Tube -type tyres: -these require tubes for inflation retention
• Tube-type tyre:- these do not required . They are constructed with an inner liner (integral rubber lining that is engineered to prevent the diffusion of the inflation gas into the casing)

Rolling Resistance:

The resistance offered by the tyres against motion of vehicle/aircraft is called as rolling resistance, the rolling resistance is produced during take off/landing in the runway

Tyre Pressure:

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

Tests of airliner aircraft tires have shown that they are able to sustain pressures of maximum 800 psi (55 bar 5.500 kPa) before bursting During the tests the tires have to be filled with water, to prevent the test room being blown apart by the energy that would be released by a gas when the tire bursts

The main landing gear on the Concorde was typically inflated to 232 psi (16.0 bar), whilst its tail bumper gear tires wore as high as The high pressure and weight load on the Concorde tyres were a significant factor in the loss of Air France flight 4590

Brakes Forces When Landing:

In general, when the wheels touch the ground, a set of spoilers raise up quickly, which kills the lift provided by the wings. (There are two sets seen in the image below ground spoilers that only deploy on landing. and spoilers that are used in flight as speed brakes as well as on landing) While the

spoilers provide some drag, their primary purpose is to stop the plane from actually flying, putting all of the weight on the landing gear and in turn making the brakes that much more effective. Stats Allerton Flap Speller Track Fairing Aircraft have highly engineered multi-disc brakes made of a carbon steel material. Manufacturers include Honeywell and Goodrich part of Collins Aerospace in general, the brakes are composed of discs that rotate with the wheel and separate discs that are fixed When pressure is applied-and below you see pressure applied from the right fixed disc on all of the discs-the entire assembly compresses to create the braking action. Carbon brakes are standard today; they cool faster than steel brakes (their predecessor) and can weigh up to 700 pounds less. That represents a significant weight saving for airlines.

Auto Brakes:

Wheel brakes are usually selected to engage automatically after landing. These are called "autobrakes" that all airliners have several levels of autobrake "severity". The crew will decide which is the most appropriate to use for every landing depending upon factors like the length of runway, if it is wet or dry, or if the pilots want to exit the runway at a particular point. "For a short wet runway you might select autobrake 3, or MED on the Airbus. For a long dry runway you might select autobrake 1 or LOW on the Airbus.

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

The rolling resistance for the air plane can be calculated as

F= cm, ag

where

F, rolling resistance (N)

C = rolling resistance coefficient

Mr = rolling mass (kg)

A_g =, acceleration of gravity (9.81 m/s²)

If the mass of a plane is 40000 kg and the rolling resistance co efficient between the aircraft wheel and the runway is 0.02

The force required to overcome the rolling resistance can be calculate as

F_r = 0.02 (40000 kg) "(981 m/s²)

=-7848 N

The friction for the puller can be calculated to

F_f = friction force (N)

where

F_F = frictional force (N)

µ = friction coefficient

W = Weight (N)

M_F = friction mass (ka)

The friction coefficient between a pulling truck rubber wheels and dry runway is 0.9. Since pulling trucks are connected to air crafts nose wheels close to runway we simplify the calculation of required truck mass

M_F = (7848 N)/ (09 (981 m/s²))

= 889 kg

Taking radius of the wheel Ras 0.3m

The torque is given by T-FR

T= 7848*0.3

=2354 Nm

The power for pulling/push the aircraft can be calculated as

P = F*V

V = velocity of pull vehicle taken as 5 km/hr

V =1.388 m/s

P = 7848 1388

=10893 W

=1000 kw

7.Design an electric powertrain with type of motor, it's power rating and energy requirement to fulfil aircraft Towing application 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 Taking the previous example power value 10 kW for this problem

Power = 10 kW

The motor power should be greater than or equal to 10kW assuming it as 10 kw

The energy required can be calculated as E=P'

assuming taxi time of 5 mins.

E=10 (5*60) kJ

=3000kJ

From power equation

Vo*lo = ƞVi*li

where

V_o is the output voltage

Io is the output current

Ƞ is the power efficiency (ranging from 0 to 1)

V_i is the input voltage

li is the input current

Consider DC input voltage as 48V and Power as 12kw

P = Vi*li

12000=48*li

li=250A

The efficiency is calculated as

n=10000/12000

=0.83

From the above power equation

Vo*lo=ƞVi*li

Vo* 250=0.83 *48*250

Vo=40V

The Vout =Vin/1-D

40=48/(1-D)

D= 0.2 the duty cycle has in the range of (0,0.2)

Block Diagram of Power Train