Project-1: Powertrain for aircraft in runways

AIM

Part A:

1. Search and list out the total weight of various types of aircrafts.
2. Is there any 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?
4. How an aircraft is pushed to runway when its ready to take off?
5. Learn about take-off power, tyre design, rolling resistance, tyre 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.
7. Develop the model for the calculated force and power using Simulink.
8. A. Design an electric powertrain with type of motor, it’s power rating, and energy requirement to fulfil 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)

1. Also, Design the parameters in excel sheet.a

Part A:

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

In today’s world aircraft plays an important role in the field of engineering. Aircraft are used for various purposes such as moving cargo and people from one place to another. It a combination of many parts such as wings, engines, fuselage, tail and plus the payload and fuel. Each part has a weight associated with it. For each flight the weights are taken into consideration for several reasons.

The total weights of various types of aircrafts are:

• AIRCRAFT GROSS WEIGHT
• MAXIMUM RAMP WEIGHT
• MAXIMUM LANDING WEIGHT
• REGULATED TAKE OFF WEIGHT
• MAXIMUM TAKE OFF WEIGHT
• PAYLOAD
• OPERATING EMPTY WEIGHT
• ZERO FUEL WEIGHT
• MANUFACURTE’S EMPTY WEIGHT

• AIRCRAFT GROSS WEIGHT

Aircraft gross weight is defined as the total aircraft weight at any moment during the flight or ground operation. During the flight the aircraft’s gross weight will decrease due to fuel and oil consumption.

• MAXIMUM RAMP WEIGHT

Maximum ramp weight is defined as the maximum weight authorised for moving (towing) the aircraft on the ground

• MAXIMUM LANDING WEIGHT

Maximum landing weight is defined as the maximum weight at which the aircraft is permitted to land

• REGULATED TAKE OFF WEIGHT

Regulated take-off weight or maximum permissible take off weight varies for each take off depending upon various factors such as flap setting, altitude, air temperature and length of runway. It cannot be higher than maximum take-off weight (MTOW).

• MAXIMUM TAKE OFF WEIGHT

Maximum take off weight is defined as the maximum weight at which the pilot is allowed to attempt to take off.

• PAYLOAD

Payload is the carrying capacity of the aircraft which is usually measured in terms of weight. Payload includes cargo, passengers, crew members, scientific instruments and extra fuel.

• OPERATING EMPTY WEIGHT (OEW)

Operating empty weight is the sum of the empty weight and the crew and includes the baggage. It also includes the fluids necessary for operation such as engine coolant, water, hydraulic fluid and unusable fuel. It excludes usable fluid and payload.

• ZERO FUEL WEIGHT

Zero fuel weight is defined as the total weight of the aircraft which includes all its contents but excludes the total weight of the usable fuel on board. As the flight progresses fuel is consumed, the total weight of the plane reduces, but the zero-fuel weight remains constant.

• MANUFACURTE’S EMPTY WEIGHT

Manufactures empty weight is defined as the weight of the aircraft build that includes the weight of the aircraft, power plant, furnishings, installations and other equipment’s that are considered an important part of the aircraft that excludes baggage, passengers and usable fuel.

The image below represents the take-off weight components

S No	Type of Aircraft	MTOW (Kg)	MLW Ton	TOR (m)	LR (m)
1	Antonov An-225	640,000	591.7	3500
2	Scaled Composites Model 351 Stratolaunch	589,670		3660
3	Airbus A380-800	575,000	394	3100	1930
4	Boeing 747-8F	447,700	346.091	3100	1800
5	Boeing 747-8	443,613	306.175	3100
6	Boeing 747-400ER	412,770	295.742	3090
7	Boeing 747-400	396,900	295.742	3018	2179
8	Boeing 747-200	377,840	285.700	3338	2109
9	Boeing 747-300	377,840	260.320	3222	1905
10	Airbus A340-500	371,950	240	3050	2010
11	Airbus A340-600	367,400	256	3100	2100
12	Boeing 777F	347,800	260.816	2830
13	Airbus A330-900	352,000	251.5	3100
14	Boeing 777-300ER	351,800	251.29	3100
15	Boeing 777-200LR	347,450	223.168	3000
16	Boeing 747-100	340,200	265.300
17	Airbus A350-1000	308,000	233.5
18	Boeing 777-300	299,370	237.683	3380
19	Boeing 777-200ER	297,550	213.00	3380	1550
20	Airbus A340-300	276,700	190	3000	1926
21	Ilyushin Il-96M	270,000	195.04	3115	2118
22	Boeing 787-9	254,000	192.777	2900
23	Boeing 787-10	254,000	201.849
24	Airbus A340-200	253,500	181	2990
25	Airbus A330-300	242,000	185	2500	1750
26	Airbus A330-200	242,000	180	2220	1750
27	Boeing 787-8	228,000	172.365	3300	1695
28	Boeing 767-400ER	204,000	158.758	3414
29	Airbus A300-600R	192,000	140	2385	1555
30	Boeing 767-300ER	187,000	136.08	2713	1676
31	Concorde	185,000	111.1	3440	2220
32	Airbus A300-600	163,000	138	2324	1536
33	Boeing 767-300	159,000	136.078	2713	1676
34	Airbus A310-300	157,000	124	2290	1490
35	Boeing 707-320B	151,000	97.5
36	Boeing 707-320C	151,000	112.1
37	Airbus A310-200	142,000	123	1860	1480
38	Airbus A400M	141,000	122	980	770
39	Boeing 757-300	124,000	101.6	2550	1750
40	Boeing 707-120B	117,000	86.3
41	Boeing 757-200	116,000	89.9	2347	1555
42	Boeing 720B	106,000	79.5
43	Boeing 720	104,000	79.5
45	Boeing 737-900	85,000	66.36	2500	1704
46	Boeing 737-900ER	85,000	71.35	2804	1829
47	Boeing 727-200 Advanced	84,000	70.1
48	Airbus A321-100	83,000	77.8	2200	1540
49	Boeing 737-800	79,000	65.32	2308	1634
50	Boeing 727-200	78,000	68.1
51	Boeing 727-100[17]	72,500	62.4
52	Boeing 727-100C[17]	72,500	62.4
53	Boeing 737-700	70,000	58.06	1921	1415
54	Airbus A320-100[18]	68,000	66	1955	1490
55	Boeing 737-400	68,000	54.9	2540	1540
56	Boeing 377	67,000
57	Boeing 737-600	66,000	54.66	1796	1340
58	Airbus A220-300	65,000	57.61	1890	1494
59	Airbus A319[18]	64,000	62.5	1850	1470
60	Boeing 737-300	63,000	51.7	1939	1396
61	Boeing 737-500	60,000	49.9	1832	1360
62	Airbus A220-100	59,000	50.80	1463	1356
63	Airbus A318[18]	59,000	57.5	1375	1340
64	Boeing 717-200HGW	55,000	47.174	1950
65	Boeing 717-200BGW	50,000	46.265	1950

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

1. Air Speed

Air Speed is the speed of the aircraft relative to the air it is flying in which is also the speed at which the air flows across the aircraft wings. Air speed determines whether there is enough air flow around the aircraft to make it fly.

2. Ground speed

Ground speed is the speed of the aircraft relative to the surface of the earth. Hence it is the horizontal speed. Ground speed determines how fast an aircraft will reach the destination. Ground speed is the sum of the air speed and wind speed.

When the aircraft experiences tail wind, the ground speed is higher than the airspeed. On the contrary if the aircraft experiences head wind, the ground speed is lower than the airspeed. Hence if there is tail wind the aircraft would reach the destination faster than if there was head wind.

There are 3 types of air speeds

1. Indicated air speeds which is calculated directly of the pilots pitot static system
2. Calibrated air speeds is the airspeed adjusted for a variety of errors
3. True air speeds is the actual speed at which the aircraft is moving where correction is made for conditions such at height, temperature of the outside air, etc.

Air speed is important for the pilot as it gives him an idea of how fast he is travelling for take off and Ground speed gives him an idea of how long the aircraft will take to reach its destination.

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

Usually, the aircraft is pushed back to a safe distance from the terminal gate by using a tug vehicle. The tug vehicle is of small size with a high torque and mass.

The same operation can be done by using engine power for moving the aircraft backwards. This is done by using reverse thrust where the blades of the propeller are twisted to take the air from behind the aircraft. This could take a lot of engine power and is hazardous for personnel and equipment. The reverse thrust could cause debris to blow and harm the ground staff or passengers waiting at the terminal gate. The debris could damage the engine and create a fire hazard. Reversing a huge aircraft is very difficult. Hence reversing is done using a tug vehicle to a safe place and then the plane will use its own power to move the plane to the start of the runway.

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

Once the clearance is obtained from the flight control, the aircraft is pushed back from the terminal gate by means of a tug vehicle. By so doing the aircraft is pushed away to a safe place before the engine can be turned ON. This is because there are several dangers that can exist when the aircraft uses the thrust from the jet engine for movement in the ground. Once the aircraft is away from the potential danger hazardous zone, the flight is now ready for taxiing. The engine of the aircraft is then turned ON. The aircraft then moves on its own power, the propulsive power that the jet engine produces for thrust during flight and moves on the ground. The aircraft then moves at a slow speed for safety reasons to the start of the runway. Sign boards and various types of light are used to guide an aircraft to the runway even if visibility is low. Tillers are used to rotate the front wheels to an angle of 45 degrees to steer the aircraft to the start of the run way. The aircraft is now ready to take off.

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

TAKE OFF POWER

During take-off the aircraft goes through a transition from ground on a runway to flying in the air. After taxing up to the starting of the runway, the aircraft is stopped. The engines are run at full power to check for engine related problems. The pilot then releases the brakes, when the aircraft is accelerated rapidly until the necessary speed for take-off is achieved. The take of speed varies depending on the weight of the aircraft, the density of air and aircraft configuration. The air density depends on the position of the airport from sea level and the atmospheric temperature. The required take off speed is to be achieved in case the aircraft has to take off which also depends on the length and slope of the runway.

The take-off speed is relative to the motion of the air. In case of a head wind the take-off speed is much less as there is greater flow of air over the wings. Hence the aircrafts usually take off against the wind. Side wind is usually not preferred as this could disturb the stability of the aircraft. The take-off speeds for the jetliners are usually 240 to 285 Km/hr and is directly proportional to the weight of the aircraft. Some aircraft have difficulty in generating enough lift during take-off. In such cases they are fitted with high lift devices which includes slats and usually flaps which increases the camber of the wings which creates more lift at low speeds. Just after the climb phase, the wheels are retracted into the aircraft and undercarriage doors are closed making the aircraft more aerodynamic.

TYRE DESIGN

Tyre is an integral component of an aircraft in terms of safety. Tyres help to absorb the shock of landing and provides cushion. It also provides the necessary traction for braking and stopping the aircraft.

The aircraft is designed in such a way that the aircraft will be able 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 aircraft needs to be more evenly distributed.

DESIGN AND CONSTRUCTION OF AIRCRAFT TYRE

Carcass piles are used to form the tyres which are commonly known as casing piles. An aircraft tyre is constructed for the following purposes it serves:

• Supports the weight of the aircraft when it is on the ground
• Necessary traction is provided for braking and stopping of the aircraft
• Absorbs the shock of landing and provide cushioning the roughness of take-off.

Tyres also absorbs high impact of landing and operates at high speed for a short time when required.

TECHNICAL ASPECTS OF THE TYRE

• RETREADING

Retreading is a method of restoring a worn tyre by renewing the tread area and also renewing one or both sidewalls. In the tyre retreading process repairs are included.

• 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

Speed rating is the maximum take-off speed to which the tyre has been tested.

• SKID DEPTH

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

ROLLING RESISTANCE

Rolling resistance is the force that resists the motion when the body rolls on the surface.

It is represented by the following equation:

F_rr = μ_r m g

Where ,

F_rr = rolling resistance force (N)

μ_r = coefficient of rolling resistance

m = Total mass of the vehicle (kg)

g = Acceleration due to gravity (m/s²)

• TYRE PRESSURE

Aircraft tyres are designed in such a way that the tyre can withstand heavy loads for short duration of time. The number of tires required for aircraft increases with weight of the aircraft as the weight of the plane needs to be more evenly distributed. The thread pattern in the aircraft tyre is designed in such a way that it can facilitate stability in high crosswind conditions and also for braking effect. Tyres can get overheated if maximum amount of brake is applied in case of aborted take-off or emergency landing. The fuses provide a safer failure mode which prevents the explosion of tyres by deflating it in a controlled manner which helps in minimizing the damage to the aircraft and the objects in the surrounding environment. Aircraft tyres operate at high pressure up to 200 psi.

BRAKING FORCES WHEN LANDING

Aircraft brakes helps to stop a moving aircraft by converting kinetic energy to heat energy by means of friction between rotating and stationary discs located in brake assemblies in the wheels. During landing these brakes provide critical stopping friction which enables the aircraft to stop within the length of the runway. In case of any technical snag the aircraft brakes help in stopping the vehicle before take -off.

Aircraft brakes also prevent motion of the aircraft when it is parked and limits the speed during taxing and can also help in steering the aircraft on the ground by applying different levels of braking force to the left and right-side brakes. Aircraft brakes work in conjunction with other brake mechanisms such as thrust reversers, air brakes and spoilers. Thrust reversers are surfaces which are deployed into the path of the jet blasts from the engine to redirect propulsive thrust in a direction which apposes the motion of the aircraft.

Air brakes and spoilers are flight control surfaces which create additional aerodynamic drag when deployed into the path of air flowing around the aircraft.

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.

A. To push back the aircraft from the terminal gate a towing vehicle is required. Towing vehicle does not require much horsepower but they need lots of torque to push or pull the aircraft.

For calculating the force and power required by the towing vehicle to push or pull the aircraft. The following forces are considered

1. Rolling resistance force
2. Acceleration force
3. Aerodynamic drag force

AIRCRAFT CALACULATIONS:

Mass of the aircraft (m_a) = 48500kg

Coefficient of rolling resistance (μ_r) = 0.03

Acceleration due to gravity (g) = 9.81ms^-2

Frontal area of an aircraft (A) = 85m²

Final velocity of the aircraft (v_f) = 3m/s

Initial velocity of the aircraft (u_i) = 0m/s

Coefficient of drag of an aircraft (c_d) = 0.15

Density of air (ρ) = 1.225 kg/m³

Acceleration time of the aircraft (t_a) = 10seconds

ROLLING RESISTANCE FORCE

Rolling resistance is the force that resists the motion when the body rolls on the surface.

It is represented by the following equation:

F_rr = μ_r m g

Where ,

F_rr = rolling resistance force (N)

μ_r = coefficient of rolling resistance

m = Total mass of the vehicle (kg)

g = Acceleration due to gravity (m/s²)

F_rr = μ_r m g

F_rr = 0.03 x 48500 x 9.81

F_rr (a) = 14274N

The rolling resistance force between aircraft wheels and tarmac road is 14274N

ACCELERATION FORCE

Acceleration force is defined as the rate of change of velocity with respect to time.

It is represented by the formula:

F= m x a

m = mass

a = acceleration

F= m x a

F= m x (vf – v_i) / t

F= 48500 x ( 3 – 0) / 10

F= 48500 x 3 / 10

F= 4850 x 3

F(a)= 14550N

The acceleration force of the aircraft is 14550N

AERODYNAMIC DRAG FORCE

Aerodynamic drag force is the drag force that acts apposite to the relative motion of any object moving with respect to a surrounding fluid.

It is represented by the formula:

F_d = ½ x ρ x A x c_{d x} v²

Where,

Ρ = Density of air (kg/m³)

A = Frontal area ( m ²)

c_d = Drag coefficient

v² = Velocity (m/s)

F_d = ½ x ρ x A x c_{d x} v²

F_d = ½ x 1.225 x 85 x 0.15 x 3²

F_d (a) = 70.284

The aerodynamic drag force experienced by the aircraft when it moves on the ground is 70.284N

TOWING VEHICLE CALCULATIONS

Mass of the Towing vehicle (m_a) = 8000kg

Coefficient of rolling resistance (μ_r) = 0.013

Acceleration due to gravity (g) = 9.81ms^-2

Frontal area of the Towing vehicle (A) = 8m²

Final velocity of the Towing vehicle (v_f) = 3m/s

Initial velocity of the Towing vehicle (u_i) = 0m/s

Coefficient of drag of the towing vehicle (c_d) = 0.60

Density of air (ρ) = 1.225 kg/m

Acceleration time of the towing vehicle (t_a) = 10seconds

ROLLING RESISTANCE FORCE

F_rr = μ_r m g

F_rr = 0.013 X 8000 X 9.81

F_rr (t) = 1020.24N

The rolling resistance force between the towing vehicle wheels and tarmac road is 1020.24N

ACCELERATION FORCE

F= m x a

F= m x (vf – v_i) / t

F= 8000 x ( 3 – 0) / 10

F= 8000 x 3 / 10

F= 800 x 3

F(t) = 2400N

The acceleration force of the Towing vehicle is 2400 N

AERODYNAMIC DRAG FORCE

F_d = ½ x ρ x A x c_{d x} v²

F_d = ½ x 1.225 x 8 x 0.60 x 3²

F_d (t)= 26.46N

The aerodynamic drag force experienced by the Towing vehicle when it moves on the ground is 26.46N

To calculate the total tractive force required, we need to add all the forces obtained

TOTAL TRACTIVE FORCE

F_{T =} F_rr (a) + F(a) + F_d (a) + F_rr (t) + F(t) + F_d (t)

F_{T =} 14274+14550+70.284+1020.24+2400+26.46

F_{T =} 32340.984N

F_{T =} 32.340984KN

POWER REQUIRED TO PUSH OR PULL THE AIRCRAFT

P = F_T * V

P = 32340.984*3

P = 97022.952W

P = 97.022952KW

B. SIMULINK MODEL FOR CALCULATION OF FORCE AND POWER

EXPLANATION OF THE MODEL

• From the above figure for the creation of the Simulink model, firstly we consider all the forces acting on the aircraft such as rolling resistance force, aerodynamic drag force and acceleration force.
• The values are assumed for mass of the aircraft, coefficient of rolling resistance, frontal area, drag coefficient and velocity and substituted in the respective formulas for rolling resistance force, drag coefficient force and acceleration force.

• Similarly for the above figure the forces are calculated for the towing vehicle the values are assumed and substituted in the respective formulas for rolling resistance force, aerodynamic drag and acceleration force.

• Finally, all the forces are added to obtain the total tractive force and the power is obtained by multiplying the total tractive force with the velocity.
• The simulation is run and the both the force and the power values are displayed using the display block.

7. A. Design an electric powertrain with type of motor, its power rating, and energy requirement to fulfil 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)

1. Also, Design the parameters in excel sheet

The following are the assumed parameters:

AIRCRAFT PARAMETERS

PARAMETERS	VALUES	UNITS
Mass of the aircraft	48500	kg
Coefficient of rolling resistance	0.03	--
Frontal area of the aircraft	85	M2
Final velocity of the aircraft	3	m/s
Initial velocity of the aircraft	0	m/s
Coefficient of drag of an aircraft	0.15	--
Acceleration time of the Towing vehicle	10	Seconds

TOWING VEHICLE PARAMETERS

PARAMETERS	VALUES	UNITS
Mass of the Towing vehicle	8000	kg
Coefficient of rolling resistance	0.013	--
Frontal area of the Towing vehicle	8	M2
Final velocity of the Towing vehicle	3	m/s
Initial velocity of the Towing vehicle	0	m/s
Coefficient of drag of the Towing vehicle	0.60	--
Acceleration of the Towing vehicle	10	seconds
Gear ratio	10

The total power required to push or pull the aircraft by the towing vehicle is 97.022952KW and the total tractive force is 32340.984N. To calculate the torque required by the Towing vehicle the following parameters are assumed as shown above:

T = F_{r *} r /G

T = 32340.984 * 0.4 / 10

T = 1293.63 Nm

The torque required for towing the vehicle to push or pull the aircraft is 1293.63 Nm

To design the electric power train of the towing vehicle a motor is selected based on its power rating and the battery required based on energy requirement and duty cycle range to control the aircraft speed from zero to highest.

MOTOR

The motor is selected with a power rating of 97.022KW and torque of 1293.63 Nm . TECO IE2 electric induction motor is selected which has a power output of 110 KW and torque at full load is 1420Nm that satisfies the power output and torque needed for the vehicle.

MOTOR SPECIFICATIONS

Output power – 110 KW, 150 hp

Full load speed – 740 rpm

Full load Efficiency – 94.5%

Full load current – 210A

Full load Torque – 1420 Nm

Rated voltage – 400V/50 Hz

DUTY CYCLE

The rated voltage is 400V and the current is assumed to be 250A. So, the input power of the motor is calculated as product of voltage and current.

P_{i =} V * I

P_{i =} 400 *280

P_{i =} 112000W

P_{i =} 112KW

To calculate the duty cycle we divide output power to input power

𝛿 = P_o / P_i

𝛿 = 97.02 / 112

𝛿 = 0.866

𝛿 = 86%

ENERGY

To calculate the energy required from batteries or battery pack. The energy is obtained by multiplying the output power and time. Assuming the battery usage for 5 minutes is 300 seconds.

E = P_o * t

E = 97.02 * 300

E = 29106kJ

So, the battery pack provides 29106 KJ of energy to the vehicle. Since the battery are rated in kilowatt hour (KWH). We have to convert KJ to KWH we divide it by 3600.

E = 29106/3600

E= 8.08KWH

So, the battery pack should provide at least 8.08 KWH to the vehicle.

POWERTRAIN DESIGN

EXCEL SHEET CALCULATIONS

TOWING VEHICLE SIMULATION POWER TRAIN BLOCK DIAGRAM

RESULTS

Required torque output of the motor	1293.63 Nm
Input power of the motor	112KW
Duty cycle range	86%
Energy required from the batteries	8.08KWH

REFERENCE

https://www.teco.com.tw/fa/ecatalogue_file/en/(Europe)StandardIE2IE3MotorCatalogueAESV-AESU.pdf