Project-1: Powertrain for aircraft in runways

Question - 1

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

Answer

The overall weight of the Aircraft is measured in different parameters,

• Basic Empty Weight (BEW) - is the weight of the aircraft "as built" and includes the weight of the structure, power plant, furnishings, installations, systems and other equipment that are considered an integral part of an aircraft before additional operator items are added for operation.
• Dry Operating Weight (DOW) - BEW + Weight of Crew (Pilot + Cabin including their bags) + Pantry
• Operating Weight (OW) - DOW + Takeoff fuel (i.e. Ramp Fuel - Taxi fuel)
• Maximum Zero Fuel Weight (MZFW) - DOW + Payload (anything put on the aircraft that generates revenue to the company, e.g. passenger, baggage, cargo, mail and fret)
• Maximum Taxi Weight (MTW) - MZFW + Ramp fuel
• Maximum Takeoff Weight (MTOW) - MZFW + Takeoff fuel, or MTW - Taxi fuel
• Maximum Landing Weight (MLW) - MTOW - Trip Fuel

Whereas weight of some various aircrafts are,

Type	MTOW [kg]	MLW [tons]	TOR [m]	LR [m]
Antonov An-225	6,40,000	591.7	3500
Boeing 747-8F	4,47,700	346.091	3100	1800
Boeing 747-8	4,43,613	306.175	3100
Boeing 747-400ER	4,12,770	295.742	3090
Antonov An-124-100M	4,05,060	330	2520	900
Boeing 747-400	3,96,900	295.742	3018	2179
Boeing 777F	3,47,800	260.816	2830
Airbus A350-1000	3,08,000	233.5
Boeing 777-300	2,99,370	237.683	3380
Boeing 777-200ER	2,97,550	213	3380	1550
McDonnell Douglas DC-10	2,56,280	183	2990	1890
Lockheed L-1011-500	2,31,300	166.92	2636
Lockheed L-1011-200	2,11,400
Ilyushin IL-86	2,08,000	175
Boeing 767-400ER	2,04,000	158.758	3414
Boeing 767-300ER	1,87,000	136.08	2713	1676
Concorde	1,85,000	111.1	3440	2220
Boeing 767-300	1,59,000	136.078	2713	1676
Vickers VC10	1,52,000	151.9
Douglas DC-8-61	1,47,000
Airbus A400M	1,41,000	122	980	770
Douglas DC-8-32	1,40,000
Douglas DC-8-51	1,25,000
Boeing 757-300	1,24,000	101.6	2550	1750
Boeing 757-200	1,16,000	89.9	2347	1555
Tupolev Tu-154M	1,04,000	80
Tupolev Tu-204SM	1,04,000	87.5	2250
Convair 880	87,500
Boeing 737-900	85,000	66.36	2500	1704
Boeing 737-900ER	85,000	71.35	2804	1829
Boeing 737-800	79,000	65.32	2308	1634
McDonnell-Douglas MD-83	73,000	63.28
McDonnell-Douglas MD-90-30	71,000	64.41	2165	1520
de Havilland Comet 4	70,700
Boeing 737-700	70,000	58.06	1921	1415

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Question - 2

Is there any difference between ground speed and air speed?

Answer -

The Ground Speed and the Air Speed are both relative to each other,

where the ground speed is dependent upon the speed of the aircraft, the direction of wind flowing, the force of wind and the air speed is more or less remaining constant depending upon the drive.

The ground speed can be varied as,

1. Wind flowing at headwind - If the wind is flowing at a speed of 20mph, the aircraft has already achieved 20mph without coming in motion. The same is added, if the aircraft needs 180mph to take off now it would only need to achieve 160mph and the remaining 20mph would be fulfilled by the wind flow.
2. Wind flowing at Tail End - If the wind is flowing at tail end the aircraft has to achieve higher speed to match the requirements. If the aircraft creates a lift at 180 mph now with 20mph wind flowing at tail end the aircraft would need to achieve the speed of 200mph to take off.

The Air Speed

The air speed is the relative speed that the aircraft is flying at while in the air. Here the actual calculation of the speed again depends upon the wind direction if it is supporting the motion of the flying direction it would assist if not it would resist.

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Question - 3

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

Answer -

The method of driving the aircraft towards the runway for the park spot is also called as Taxiing (Taxying),

It is operated with all precautions as it depends upon airport to airport what sorrounding can cope up with the thrust which is occured by the rear end of the aircraft. The speed is kept very less until it reaches to the runway so that the aircraft could be stopped in case of any emergency. The distance of the thrust which would be obtained depends upon the speed generated and therefore the rear end has to be taken care of.

The figures depict the zone where the thrust of the aricraft might impact and that zone has to be kept clear.

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Question - 4

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

Answer -

The aircraft is pushed to runway from the parking spot for being ready for the take off

The procedure is followed by the engine which is turned on and the aricraft is moving slowly by taking turn using the Tillers which help the front wheels to rotate by 45 Degrees. This is used when the turn is been taken for reaching to the runway. There are some Tractors, Tugs, Towbars which are used to move the aircraft in pushback condition as it is not counted as safe for reversing the aircraft. The ground staff allocates and once the clearance is received the aricraft is ready to move on the runways. The trucks and tillers look like this,

The Ground Staff guiding the directions

The Truck pulling the aircraft towards the runway,

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Question - 6

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

Answer -

Take Off Power - The speed required for the power to take off also depends upon the relative motion of the air, if it is on the same direction of the take off it would assist and help in better take off with little lesser power, thrust.
In normal situations for the jetliners it required to 240 to 285 kmph for match the requried initial thrust and power. Whereas if the aircraft is smaller it would need to reach at around 100kmph.
The nose is raised to around 5°–15° for the take off.

Tyre Design -

The tyre design is prepared while keeping in mind to withstand heavy load, high temperature, ability to split water, prevent from skidding and many others. The tyre tread is specifically designed to suit the requirements of an aircraft. The radial ply tyres are the best suited tyres for the aircrafts whereas the technology of being the radial ply assists to withstand heavy load and give high efficiency.

Radialy Ply Tyres

Also the tires are corporated with a fusible plugs which deflates the tyres and prevent them from bursting when the temperature reaches at an extensive range.

Rolling Resistance -

Rolling resistance is the force that reists the motion of the surface. The rolling resistance is formed on the opposite side of the motion of vehicle,

The rolling resistance can also be calculated or is also known as,

Fr = Cw

Fr - Rolling Resistance or rolling friction

C = Rolling Resistance Co-efficient

W = m ag

Where, m = mass

ag = acceleration of gravity

Tyre Pressure -

Usually the air pressure in tyres are filled at 220psi to 294 psi depends upon the aircraft weight and usage, also the tyre weights around 120 kg to 200 kg, nitrogen is used to inflate the tyres which keeps the temperature low at all conditions and minimize the expansion and contraction at high temperatures.

Brake Force while Landing -

For stopping a Flight which is landing at a speed of 180kmph high braking pressure is required, which can be delivered using the hydraulic or the electric braking. In hydraulic braking each wheel has a braking module been fitted on 8 wheels and the fluid is pressurized by 3000 pounds per square inch for enhanced braking and while the electric brakes are also known as plug and play as the hydraulic pipes are replaced by the electric wires and the brakes are applied this also saves 141 to 240 pounds.

E-Actuator

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Question - 6

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

Answer -

For calculating the force required to push/pull the aircraft on the flat runway with tarmac road and no other cases considered will be calculated as,

Fr = c * mr * g

Where, Fr = rolling resistance, c = coeffficient of rolling resistance, mr = rolling masss, g = gravitational speed 9.81 m2

In our case, let us consider the weight of an aircraft to be 40,000 kg and the coefficient of rolling resistance be 0.03 lets calculate the rolling resistance,

Fr = 0.03 * 40000 * 9.81

Fr = 11772 N

Mass Required by pulling tug,

Tarmac = 0.8

Ff = c * mf * ag

Where, Ff = Friction Force, c = coefficient of friction, mf = friction mass, ag = gravitational acceleration.

mf = 11772 / (0.8 * 9.81)

mf = 1500 kg

Radius of the wheel = 0.30

Now calculating torque = F*R

T = 11772 * 0.3

T = 3531 N-m

So Power = F * V

Velocity = 10 kmph

= 2.778 m/s

= 11772 * 2.778

= 33,008 W

= 33 kW

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Question - 7

Design an electric powertrain with type of motor, it’s power rating, and energy requirement to fulfill 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.

Answer -

As per the calculations made above,

Power = 33 kW

Torque = 3531 Nm

Towing time = 10 seconds

Energy required as per time = 99kW

Tyre Pressure = 200 psi and 13.78 bar

Towing Velocity = 10 kmph

Weight/mass = 40,000 kg

The specified Energy calculate for a time duration is the moderate or least time for which the tow might be required for different operations the same would be varied at many alternative manners and the same is done possible only by the duty cycle. We have studied the varied duty cycle strategies for contolling the power requirements and operating the vehicles/machines in the required manner. For varying the duty cycle a microprocesser alerts and changes the ratio of power so that the basic requirement of the vehicle are been fulfilled. At current stage majorly tug/towing vehicles used are Fuel operated very few countries have incorporated the Electric operated Tug.

The duty cycle here could be expressed as -

Duty Cycle = Output Power / Input Power

We have the Output Power with us, for finding the Input Power.

As we know

P = V * I

Let us consider the battery specifications here to be

Input Voltage = 440V

Input Current = 85 Amp

So Power Input = 440 * 85 = 37,400 W = 37.40 kW

Now lets find the duty cycle,

Duty Cycle = Output Power / Input Power

Duty Cycle = 33 / 37.80

= 88%

The Duty cycle has to be maintained at 88% based on all assumption that we have considered here.

Motor Type

As we went through the several types of motor the one which would perfectly suit the requirements of the tow truck is the Brushless DC Motor as the speed range required here is less and the torque and power requirement is high the same would be efficient for this purpose. Apart from that the motor would not require the regular maintenance.

Block Diagram of Powertrain