Project-1: Powertrain for aircraft in runways

1. List of various types of aircraft with maximum take-off weight (MTOW) and maximum landing weight (MLW)

Aeroplane	MTOW (tons)	MLW (tons)
Airbus A380-800	633.829	394
Boeing 747-8F	493.5047	346.091
McDonnell-Douglas MD-83	80.4687	63.28
Boeing 737-500	66.1386	49.9

Helicopter	MTOW (tons)	MLW (tons)
Mil Mi-26	61.7295	61.7294
Sikorsky CH-53E	36.75	36.7069
AgustaWestland AW101	17.196	16.0937
NHIndustries NH90	11.685	11.6845

2.

Yes, there is difference between ground speed and air speed. 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.While ground speed is the airplane’s speed relative to the surface of the Earth.

For a passenger aircraft

`V_{ground}=756{km}/{hr}`

`V_{"wind"}=160{km}/{hr}`

`V_{air speed}=V_{ground}-V_{"wind"}`

`V_{air}=596{km}/{hr}`

3.

The only time aircraft use external assistance is to push-back from the gate. Large turbofan aircraft need help to reverse via a push-back tug. The engines are turned on after the push-back is complete and the aircraft can move forward under It’s own power.

All large aircraft are pushed back , they could use there power to do it but due to the noise and fumes plus they burn a lot of fuel.

4.

After all doors have been secured, involves the movement of the aircraft away from the terminal Jetway and along taxiways to a runway. A motorized vehicle called a tug sometimes is used to push the aircraft back from its gate. At some airports, certain aircraft are permitted to power back. This means that following engine start at the gate, the thrust reverses are used to literally back the aircraft away from the gate. The aircraft then moves under its own power along the taxiways. Since aircraft are designed primarily for flight, and are not ground vehicles, they are taxied at very low speeds. Push-back occurs only when the pilot has clearance to do so from Air Traffic Control, which monitors all aircraft movements during taxi.

5.

Take off power

Takeoff is the phase of flight in which an aerospace vehicle leaves the ground. For light aircraft, usually full power is used during takeoff. Large transport category 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.The engine speeds then increase to provide the computed take off power. Modern aircraft flight management computers will determine the power needed by the engines to take off, based on a number of factors such as runway length, wind speed, temperature, and most importantly the weight of the aircraft.

Tyre Design

Aircraft tyre does not have to carry a load for a long period of continuous operation. However, an aircraft tyre absorbs the high impact loads of landing and also it’s operating at high speeds for a short time when required.

Nowadays all airliners are using tubeless tyres and Radial tyre. Aircraft tyres are manufactured with tread rubber with conducting compounds to permit earthing of static charges. Chine tyre used on the nose wheel of aircraft, specially fuselage-mounted jet engines. Chines are circumferential protrusions that are moulded into the sidewall of nose tyres that deflect water sideways to help reduce excess water ingestion into the engines. Tyres may have chines on one or both sides, depending on the number of nose tyres on the aircraft.

Rolling Resistance

Rolling resistance is the force resisting the motion when a wheel rolls on a surface. It is mainly caused by non-elastic effects i.e. not all the energy needed for deformation of the wheel is recovered when the pressure is removed.In case of aircraft, rolling resistance is experienced while takeoff and landing.

The force to move an air plane on an absolute flat runway with no wind at constant low speed is equal to the rolling resistance between the plane and the tarmac.

The rolling resistance for the air plane can be calculated as

F_r = c m_r a_g

where

F_r = rolling resistance

c = rolling resistance coefficient

m_r = rolling mass

a_g = acceleration of gravity

Tyre Pressure

Aircraft tires are usually inflated with nitrogen to minimize expansion and contraction from extreme changes in ambient temperature and pressure experienced during flight. Common compressed air sources may contain moisture, which increases the expansion rate with temperature. But, dry nitrogen expands at the same rate as other dry atmospheric gases. Aircraft tires generally operate at high pressures, up to 1,400 kPa for airliners, and even higher for business jets.

Braking Forces When Landing

Braking action in aviation is a description of how easily an aircraft can stop after landing on a runway. Aircraft braking system

Aircraft disc brakes:-

They are used to brake the wheels while touching the ground. These brakes are operated hydraulically or pneumatically. In most modern aircraft they are activated by the top section of the rudder pedals

Thrust reversers:-

They allow thrust from the engines to be used to slow the aircraft.

Air brakes:-

They are dedicated flight control surfaces that work by increasing drag.

Large drogue parachutes:-

They are used by several former and current military and civilian aircraft and in the Space Shuttle.

Hydaulic Braking System.

Modern T-category airplanes exclusively use highperformance anti-skid controlled disc brakes. The anti-skid valve modulated hydraulic pressure acts on pistons in the pressure plate, which together with the end plate produces clamping force, squeezing rotors and stators together. Clamping force produces friction force and the braking torque, which slows the wheel/tire angular speed and dissipates aircraft motion energy.

Clamping Force(`F_{CN}`)=Hydraulic pressure X Area

Breaking Force(`F_b`)`=mu_b*F_{CN}`

6.

Assumption

1. Absolute flat runway
2. Still air
3. Constant and low speed of aircraft

Enough weight for the pullers are required to create friction forces against the tarmac that equals the plane rolling resistance.

Calculation of rolling resistance

consider Boeing 737-500

maximum take-off mass=60,000kg

Diameter=0.06858

Rolling Resistance force(F_r)=c m_r g

=0.02x60,000*9.81

=11772N

Drag force`(F_D)=1/2C_DrhoAV^2`

=31.85 N

Rolling Resistance for towing vehicle=c m g

=0.02x8000x9.81

=1,569.6 N

The friction force for the puller can be calculated to

F_f = μ W

= μ m_f g

where

F_f = frictional force

μ = friction coefficient

W = weight

m_f = friction mass

Frictional force=rolling resistance force + drag force + Rolling Resistance for towing vehicle

=11772+31.85+1569.6

=13373.45 N

m_f=13373.45/(0.9x9.81)

=1,514.71 kg

Power required for pulling /pushing

Asuming speed of towing vehicle is 10 m/s

`omega=V/R`

`=29.16 {rad}/s`

Torque=radius x force

=0.3429 x 13373.45

=4585.75 N-m

power=Torque x angular Velocity

=133.72 kW

7.

Parameter	Assumed values
Wt.of aircraft	60,000 kg
Wt. of Towing Vehicle	8000 kg
Frontal Area of Aircraft	20`m^2`
Radius of tyre of towing vehicle	0.3429 m
Rolling Resistance coefficient aircraft	0.02
Rolling Resistance coefficient towing vehicle	0.02
Drag coefficient	0.026
Density of Air	1.225
Rated Motor Armature Voltage	400 V
Rated Motor Armature Current	500 A
Armature Resistance	0.04371
Rated Speed	750 RPM
Towing vehicle speed	10 m/s

Cosidering above assumption, power of motor is 200 kW

`P_i=200 kW`

`P_o= 133.72 kW`

Rated Torque=Rated Power/Rated angular speed

=2546.48 N-m

`K_t=T/I_a=5.09`

`I_a=T_{actual}/K_t=900.93 A`

`V_o=P_o/I_a=148.43 V`

So, duty cycle`=V_o/V_i`

`=0.37`

Average taxiing time is 15.8 mins

Enegry requirement=Power x Time

=126.77 MJ