Powertrain for aircraft in runways

Q 1: List out the total weight of various types of aircraft?

Ans 1:

• 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)- (This is the total weight of the airplane and all its contents (including unusable fuel), but excluding the total weight of the usable fuel onboard).
• Maximum Taxi Weight (MTW)MZFW + Ramp fuel
• Maximum Takeoff Weight (MTOW)MZFW + Takeoff fuel, or MTW - Taxi fuel(This is the maximum weight at which the pilot of the aircraft is allowed to attempt to take off).
• Maximum Landing Weight (MLW)-MTOW - Trip Fuel-(This maximum weight at which an aircraft is permitted to land.)

Q2: Is there any difference between ground speed and airspeed?

Ans 2: Airspeed is the vector difference between ground speed and 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. True airspeed is simply the speed at which an aircraft is moving relative to the air it is flying in. As such, it’s also the speed at which the air is flowing around the aircraft’s wings.

The indicated airspeed (IAS) is the speed on the airspeed indicator. This will be different than the ground speed for various reasons, such as wind and the attitude of the aircraft. For example, if the aircraft is diving then the IAS will be greater than the ground speed. In fact, if the aircraft were diving straight down, then the ground speed could be 0 while the IAS was hundreds of knots per hour.

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

Ans3 Although most aircraft are capable of moving themselves backward on the ground using reverse thrust, a procedure called as a power back, it is not typically done due to the following reasons,

• The jet blast from the engines can damage the terminal building and nearby equipment. It can even throw away people standing nearby.
• Engines can blow sand and debris.
• Engines can suck in sand and debris which can cause serious damage to the engine
• It is easier for the truck driver to see the surroundings better than the pilot sitting in the cockpit with limited windows.
• The pushback truck driver knows the airport better than the pilot.
• The plane engines are very loud. This noise can add up substantially when multiple planes are moving around the airport. It won't be a pleasant experience for people sitting inside the terminal, as most people don't even like the sound of powerful motor-bikes.
• It saves fuel. Virgin Atlantic had proposed a new system in which the pushback trucks will push the plane all the way to the runway to save fuel and reduce the impact on the nearby environment.
• Modern planes are huge. See the image below for comparison. It is difficult to navigate such gigantic structures through limited space. An A380 is eight stories high. The pilots won't be able to see anything directly in front of them or anything behind the wings.

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

Ans 4: This can be easily understood by knowing the term taxing. Taxiing is the movement of an aircraft on the ground, under its own power, in contrast to towing or push-back where the aircraft is moved by a tug. The aircraft usually moves on wheels, but the term also includes aircraft with skis or floats.

An airplane uses taxiways to taxi from one place on an airport to another; for example, when moving from a hangar to the runway. The term "taxing" is not used for the accelerating run along a runway prior to takeoff, or the decelerating run immediately after landing, which is called the takeoff roll and landing rollout respectively. ,

If the supposed engine is using its own power in moving from hanger to runway then it may cause damage to the surroundings as engine power is much higher or there may be a loss of control should also be there.

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

Ans 5: Take off the power: Takeoff is the phase of flight in which an aerospace vehicle leaves the ground and becomes airborne.

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. In some emergency cases, the power used can then be increased to increase the aircraft's performance.

Tyre Design: Tyre is designed to withstand extremely heavy loads for short durations. The number of tires increases with an increase in the weight of aircraft. Aircraft tire tread patterns are designed to facilitate stability in high crosswind conditions, to channel water away to prevent hydroplaning, and for braking effect.

Aircraft tires have fusible plugs (which are assembled on the inside of the wheels), designed to melt at a certain temperature

Rolling Resistance: The resistance offered by wheels of aircraft when running on runway, the direction of rolling resistance force is always in the opposite direction of motion of an aircraft.

Tyre pressure: Aircraft tires generally operate at high pressures, has a diameter of 134 cm (53 in) and is changed every 300 cycles while the brakes are changed every 2000 cycles, up to 200 psi (14 bar; 1,400 kPa) for airliners, and even higher for business jets. ... 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.

Brake forces while landing: All modern aircraft have an automatic braking system just like vehicles having an anti braking system(ABS) which avoids the skids of the wheel on the wet surface. During braking passengers experienced a constant force that pushes then on the seat. Brake system automatically applies a wheel brake just enough to provide constant deceleration independent of air resistance, spoiler, and reservers. Immediately after landing aircraft motion is opposed by aerodynamic drag more efficiently then brakes.

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

Ans 6 Force required to push/pull an aircraft with no wind or at constant low speed is equal to the rolling resistance between plane and tarmac.

Fr= Rolling resistance force (N)

Cr=coefficient of rolling resistance

Mr=Rolling Mass (kg)

g = Acceleration due to gravity (9.8 m/s^2)

We know that,

Fr= Cr*Mr*g

Assumptions

Mr=40000 kg

Cr=0.02

Fr=0.02*40000*9.8

=7848N

This force can be pulled by a truck which can be assumed as the number of person n

Ff= friction force (N)

Uf= coefficient of friction

W= weight

Ff=Ur*W

To pull the aircraft by this Ff=Fr

7848=0.9*Mf*9.81

Mf=889 kg

If they blend over 45 degrees then vertical force component = Horizontal force component

With an average of 80 kg per person

No. of person required to produce such force (n)=889/80=12

If we want to calculate the force and power for a towing vehicle

Let the radius of wheel be = 25 cm=0.25 m

Speed of towing vehicle (N)(rpm)=250

CALCULATION OF TORQUE

T=Force*radius

=7848*0.25=5493.6 Nm

Power required is given by

P=T*ῳ

=5493.6*((2*pi*N)/60)=5486.9*((2*3.14*250)/60)=143.822 KW

Q7. Design an electric powertrain with the 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 the powertrain.

Ans 7

From the previous question we have made certain assumptions and the output power(P) obtained is 143.822 KW let assume it as 150 KW by considering safety factor.

Assume the power train for towing application with DC shunt motor

Battery voltage = 750 V

Battery current =250 A

Pinput=187.5 KW

Convertor is a Buck convertor

Tt= Taxi time i.e time required to carry the aircraft to runway

Tt=10 mins

Engery requied to fullfill towing application = P * Tt

= 150*10*60=90 MJ

Let D be the duty cycle which is given by= Ton/T

Variation of Duty cycle 0< D< Dmax

Let the efficiency of transmission system is 0.95

Pin of transmission = P out of chopper = 150/0.95=157.89 kW

Pout= V0*Io

Vo=Pout /Io as, Io = Ib=250 A

Pin= Vb*Ib

Vb=Pin/Ib

Dmax=Vo/Vb

= Pout / Pin=157.89/187.5 = 0.84

Range of Duty cycle 0< D< 0.84