Challenge

Project-1: Powertrain for aircraft in runways

TTangalapally Naveen Kumar8 Jan 2022

Project-1: Powertrain for aircraft in runways

Study Case:

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.

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

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)

B. Also, Design the parameters in excel sheet.

Part 1:

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

MTOW = Maximum take-off weight, MLW = Maximum landing weight, TOR = Take-off run (SL, ISA+15°, MTOW), LR = Landing run (SL, ISA+15°, MLW)

Type	MTOW [kg]	MLW [tonnes]	TOR [m]	LR [m]	ICAO category	FAA category
Antonov An-225	6,40,000	591.7	3500		Heavy	Super
Scaled Composites Model 351 Stratolaunch	5,89,670		3660		Heavy	Super
Airbus A380-800^[1][2][3]	5,75,000	394	3100	1930	Super	Super
Boeing 747-8F	4,47,700	346.091	3100	1800	Heavy	Heavy
Boeing 747-8	4,43,613	306.175	3100		Heavy	Heavy
Boeing 747-400ER	4,12,770	295.742	3090		Heavy	Heavy
Antonov An-124-100M	4,05,060	330	2520	900	Heavy	Heavy
Boeing 747-400	3,96,900	295.742	3018	2179	Heavy	Heavy
Lockheed C-5 Galaxy^[4][5][6]	3,81,000	288.417	2530	1494	Heavy	Heavy
Boeing 747-200^[7]	3,77,840	285.7	3338	2109	Heavy	Heavy
Boeing 747-300^[7]	3,77,840	260.32	3222	1905	Heavy	Heavy
Airbus A340-500^[8]	3,71,950	240	3050	2010	Heavy	Heavy
Airbus A340-600^[8]	3,67,400	256	3100	2100	Heavy	Heavy
Boeing 777F	3,47,800	260.816	2830		Heavy	Heavy
Boeing 777-300ER	3,51,800	251.29	3100		Heavy	Heavy
Boeing 777-200LR	3,47,450	223.168	3000		Heavy	Heavy
Boeing 747-100^[7]	3,40,200	265.3			Heavy	Heavy
Airbus A350-1000	3,08,000	233.5			Heavy	Heavy
Boeing 777-300	2,99,370	237.683	3380		Heavy	Heavy
Boeing 777-200ER	2,97,550	213	3380	1550	Heavy	Heavy
Airbus A340-300^[8][9]	2,76,700	190	3000	1926	Heavy	Heavy
McDonnell Douglas MD-11	2,73,300	185	2990	1890	Heavy	Heavy
Airbus A350-900	2,70,000	175	2670	1860	Heavy	Heavy
Ilyushin Il-96M	2,70,000	195.04	3115	2118	Heavy	Heavy
McDonnell Douglas DC-10	2,56,280	183	2990	1890	Heavy	Heavy
Boeing 787-9^[10]	2,54,000	192.777	2900		Heavy	Heavy
Boeing 787-10^[10]	2,54,000	201.849			Heavy	Heavy
Airbus A340-200^[8][11]	2,53,500	181	2990		Heavy	Heavy
Airbus A330-900	2,51,000	1,91,000	3100		Heavy	Heavy
Ilyushin IL-96-300	2,50,000	175	2600	1980	Heavy	Heavy
Airbus A330-300^[12][13]	2,42,000	185	2500	1750	Heavy	Heavy
Airbus A330-200^[12][13]	2,42,000	180	2220	1750	Heavy	Heavy
Lockheed L-1011-500	2,31,300	166.92	2636		Heavy	Heavy
Boeing 787-8^[10]	2,28,000	172.365	3300	1695	Heavy	Heavy
Lockheed L-1011-200	2,11,400				Heavy	Heavy
Ilyushin IL-86	2,08,000	175			Heavy	Heavy
Boeing 767-400ER	2,04,000	158.758	3414		Heavy	Heavy
Airbus A300-600R^[14]	1,92,000	140	2385	1555	Heavy	Heavy
Boeing 767-300ER	1,87,000	136.08	2713	1676	Heavy	Heavy
Concorde	1,85,000	111.1	3440	2220	Heavy	Heavy
Airbus A300-600^[14]	1,63,000	138	2324	1536	Heavy	Heavy
Boeing 767-300	1,59,000	136.078	2713	1676	Heavy	Heavy
Airbus A310-300^[14]	1,57,000	124	2290	1490	Heavy	Heavy
Vickers VC10	1,52,000	151.9			Heavy	Heavy
Boeing 707-320B^[15]	1,51,000	97.5			Heavy	Heavy
Boeing 707-320C^[15]	1,51,000	112.1			Heavy	Heavy
Douglas DC-8-61	1,47,000				Heavy	Heavy

Study Case 2: Is there any difference between ground speed and air speed ?

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.

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

airplanes are equipped with engines rated from 18,000 to nearly 100,000 lb of thrust. Such thrust levels provide for safe takeoff, flight, and landing over a wide range of temperatures, altitudes, gross weights, and payload conditions. However, the exhaust wake from these engines can pose hazards in commercial airport environments. Operators and airport authorities must carefully consider these hazards and the resulting potential for injury to people and damage to or caused by baggage carts, service vehicles, airport infrastructure, and other airplanes.

Power Hazard Areas
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

Foreign Object Damage
Foreign object damage (FOD) caused by high engine thrust can affect airport operations as it relates to

Airplane structure.
Flight controls.
Equipment and personnel.

Abover are the reasons why a towing vehicle is used for moving areoplanes for short distances and in reverse direction

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

Airplanes have engines, and they can use them to move forward along the ground. So they push themselves to the runway.

It is true that most of the time, a small vehicle is needed to push the larger commercial airplanes backwards away from the terminal building, because even if a plane can reverse it’s thrust, it’s not always safe to hit the buildings with that reverse thrust. So the little trucks push the bigger planes back away from the buildings, but after that, the planes can apply a small amount of engine power to roll forward just as all airplanes can.

Study Case 4:Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing ?

Take off power:

On take-off, in order to position the aircraft to a safe height away from terrain and obstacles (i.e. a flight path of maximum height and minimum ground distance desired), the engine thrust is set to a high ‘take-off power’ setting (although this is not necessarily full power) and the aircraft attitude is pitched up to maintain a specific speed (usually in the region of V2 + 15kts). Once the ‘safe height’ is reached the engine thrust can therefore be reduced to a more appropriate (i.e. efficient) setting and the aircraft flight path can be changed to a more appropriate (i.e. efficient) flight path.

First, let's figure out how much power a 747 needs to takeoff:

Assume:

Engine thrust = 284 kN
Takeoff speed = 170 knots
Takeoff power = 90% max power

Using

P=Fv

, converting the variables to SI units, we get

Power=88,948,800W

Or, in other words, around

90MW

_{Exact Calculation:}

The engine can produce static thrust

Ts=58,000 lbf=258 kN

using mass flow rate of

m˙=1,604 lb/s=727.5 kg/s

Now due to principle of action and reaction, the engine must apply the thrust to the air passing through it. We know that

F=ma=mΔvtF=ma=mΔvt

and using

m=m˙tm=m˙t

we get

F=Ts=m˙Δv=m˙veF=Ts=m˙Δv=m˙ve

, where

ΔvΔv

is change of velocity of the air inside the engine, which is equal to exhaust velocity

veve

, since we are starting with still air. We can solve for exhaust velocity:

ve=Ts/m˙≈355 m/s

That's pretty fast. In fact, it is mildly supersonic, though in practice it is average of the just subsonic bypass flow and the faster hot core flow (in which the speed of sound is higher).

We also know that kinetic energy is

E=12mv2eE=12mve2

and, deriving by time, power is

P=E˙=1/2 m˙ v^2 ; P=E˙=1/2 m˙ v^2

but v = Ts / m

So power = 45.7 MW

That's one engine.

_{3.Tyre design:}

Radial tires are the most modern design of aircraft tyres. It is a design that is similar to that of car tyres. Typically, the radial tyre offers more landings per tread and lighter weight than a bias tyre; though sometimes at the expense of retread lives.

Design and Construction of Aircraft 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.

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

Let’s go through some technical aspects of the tyre.

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.

Tyre growth– is the increase in the size of the tyre due to centrifugal forces at high speed.

Brakes:

The brake system on the 787 Dreamliner is controlled by the pilots pressing the tops of the rudder pedals under their feet, demanding the rate of braking which they require. This sends an electronic signal to the Left and Right Brake System Control Units (BSCUs).

These then send signals to the four Electronic Brake Actuator Controllers (EBAC) which control the rate of braking on the wheels. Each wheel has four Electric Brake Actuators (EBA), a kind of piston which presses against the carbon brake discs.

Additional Support:

In addition to the brakes, there are two other systems which help slow the aircraft down on landing. The spoilers and the reverse thrust.

Spoilers

Have you noticed the large panels on the top of the wings raise up on touch down? These are the called the spoilers as they literally spoil the airflow over the wing. This dumps any remaining lift the wings are generating, allowing the wheels to take all the weight and achieve maximum efficiency from the brakes.

Reverse thrust

The final part of the braking process comes from reverse thrust. Just after we have touched down, we pull two levers on top of the thrust levers to engage the reverse thrust, a sort of “reverse gear” for jet engines.

Braking forces:

irst, some requirement assumptions . . .

Landing weight = takeoff weight in case of aborted takeoff = 1500 lbf

Landing distance = 500 ft

Speed (assume aborted takeoff) = 60 kt (100 ft/sec)

We will use Newton’s second law to determine force due to deceleration:

Deceleration: from simple kinematics, acceleration = velocity^2 / distance

= (100 ft/s)^2 / 500 ft = 20 ft / s^2

Mass of aircraft = (weight) / g = 1500/32.2 = 46.58 lbf*s^2 / ft

Force = mass * acceleration (46.58 lbf*s^2/ft) * (20 ft / s^2) = 931.6 lbf

So in this example, the braking (deceleration) force is 931.6 lbf

Part B:

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

Weight of Boeing 787 - 8 = 118,000 kg

no.of Tyres = 10 Tyres

Rolling resistance on tyres = 118000 * 9.81 * 0.03

= 34727.4 N

Drag force

= 0.5 * Air density * Projected area * Velocity ^ 2 * drag co eff

Assume aeroplane is being pulled at 5 m/s

Drag force = 0.5 * 1.293 * 32.29 * 25 * 0.45

= 2348.9 N

Total Force required = 34727.4N + 234N

= 35480.4

Power required = Total Force * velocity

= 35481.4 * 5

= 177.23KW

Torque required = Total Force * R/G

= 35481.4 * 0.67/15

= 1584 n-m

Simulink model Calculating the Above equation:

Study Case 7A: 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.

Simulink Model: