Project-1: Powertrain for aircraft in runways

PART A

Q1-1. Search and list out the total weight of various types of aircrafts.

ans-

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 Stratolaunch	589,670
Airbus A380-800[1][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[3][4][5]	381,000	288.417
Boeing 747-200[6]	377,840	285.700
Boeing 747-300[6]	377,840	260.320
Airbus A340-500[7]	371,950	240
Airbus A340-600[7]	367,400	256
Boeing 777F	347,800	260.816
Boeing 777-300ER	351,800	251.29
Boeing 777-200LR	347,450	223.168
Boeing 747-100[6]	340,200	265.300
Airbus A350-1000	308,000	233.5
Boeing 777-300	299,370	237.683
Boeing 777-200ER	297,550	213.00
Airbus A340-300[7][8]	276,700	190
McDonnell Douglas MD-11	273,300	185
Airbus A350-900	270,000	175
Ilyushin Il-96M	270,000	195.04
McDonnell Douglas DC-10	256,280	183
Boeing 787-9[9]	254,000	192.777
Boeing 787-10[9]	254,000	201.849
Airbus A340-200[7][10]	253,500	181
Ilyushin IL-96-300	250,000	175
Airbus A330-300[11][12]	242,000	185
Airbus A330-200[11][12]

Q2 Is there any difference between ground speed and air speed?

ans-

WIND SPEED-

1)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.

2)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).

3) 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-

1)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.

2) so a comparison of the ground speed to the wind speed must be done according to rules for vector comparisons.

AIRSPEED-

1)The important quantity in the generation of lift is the relative velocity between the object and the air, which is called the airspeed.

2)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

3)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.

4)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 e.g opposite direction

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

5)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.

Q3. Why is it not recommended to use aircraft engine power to move it on the ground at Airport?

ans-

1)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.

2) 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.

3)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.

4)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 .

5) 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.

6) 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.

7)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.

Q4. How an aircraft is pushed to runway when its ready to take off?

ans-

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

2)Although many aircraft are capable of moving themselves backwards on the ground using reverese thrust (a procedure referred to as a powerback), the resulting jetblast or propwash might cause damage to the terminal building or equipment.

3) 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.

4)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.

5)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 aircraft's normal steering mechanism.

6)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.

Q5 Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.

ans-

Take-Off Power:

1)For light aircraft, usually full power is used during takeoff. Large transport category (airliner) aircraft may use a reduced power for takeoff, where less than full power is applied in order to prolong engine life, reduce maintenance costs and reduce noise emissions.

2)In some emergency cases, the power used can then be increased to increase the aircraft's performance. Before takeoff, the engines, particularly piston engines, are routinely run up at high power to check for engine-related problems.

3) The aircraft is permitted to accelerate to rotation speed (often referred to as V_r). 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).

4)The nose is raised to a nominal 5°–15° nose up pitch attitude to increase lift from the wings and effect liftoff. For most aircraft, attempting a takeoff 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 line of the tread.

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

• Tube-type tyres - these require tubes for inflation retention.
• Tubeless tyres - these do not require tubes. They are constructed with an innerliner

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:

1)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.

2)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.

Brakes Forces When Landing:

1)In general, when the wheels touch the ground, a set of spoilers raise up quickly, which kills the lift provided by the wings.

2)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.

3)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.

4) 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

5)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”.

6) 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".

Q6. A. With necessary assumptions, calculate the force and power required to push / pull an aircraft by a towing vehicle.

ans-

The rolling resistance for the air plane can be calculated as

F_r = c m_r a_g

where

F_r = rolling resistance (N)

c = rolling resistance coefficient

m_r = 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 calculated as

F_r = 0.02 * (40000 kg) *(9.81 m/s²)

= 7848 N

The friction for the puller can be calculated to

F_f = μ W

= μ m_f a_g

where

F_f = frictional force (N)

μ = friction coefficient

W = Weight (N)

m_f = friction mass (kg)

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) / (0.9 (9.81 m/s²))

= 889 kg

Taking radius of the wheel R as 0.3m

The torque is given by T=F*R

T= 7848 * 0.3

= 2354 N.m

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*1.388

=10893 W

=10.89 kW

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

ans-

• 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 visualised using display blocks.

Q7A. 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.

ans-

Based on the calculations done in 6A.

Force required to push/pull the aircraft =19.508 KN

Power required =135.478 kw

Let us assume,

The Radius of the Tyre for the Tug - 25inches =0.635m

Gear ratio=8

Transmission Effeciency (nt) =87%

Motor Efficiency (nm)=95%

then,

Torque required for the wheels (Tw)=Total Force *Radius in meters

=19.508 *0.635

=12.387KNm

Motor Torque-Wheel torque/(Gear ratio'nt)

=12.387/(8 0.87)

=1.778KNm
For nm =95%. The required motor Torque (Tm)= 1.778/0.95 =1.871 kNm

Similarly. The total power required by the motor considering all the efficiencies (Pt) = 135.478/(0.87*0.95)=163.917Kw

Let us assume the towing operation was done for a 15 minutes (0.25Hrs) duration.

Then, Total Energy consumed = 163.917* 0.25=40.98 KWh

If we consider the battery capacity=220 kw is used by the towing vehicle then. The duty cycle range to control the speed from O to max speed (3m/s) is given as

Duty Cycle (d)= (Required Power)/ (Rated power)= 163.917/220 =0.75

Therefore the controller will be able to provide a duty cycle ranging from 0 to 75% in order to control the towing speed.

B. Also, Design the parameters in excel sheet.

ans- answer excel sheet uploaded below