Project-1: Powertrain for aircraft in runways

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

Different terms represent the different weights of aircraft. Terms are MEW, ZFW, OEW, MTOW, RTOW, MLW, MRW.

Manufacturer's empty weight (MEW):

It is the weight of the aircraft and includes the weight of the structure, power plant, furnishings, installations, systems and other equipment that are considered an integral part of an aircraft.

This excludes any baggage, passengers, or usable fuel.

Zero-fuel weight (ZFW):

This is the total weight of the airplane and all its contents (including unusable fuel), but excluding the total weight of the usable fuel on board. As a flight advancements and fuel is consumed, the total weight of the airplane reduces, but the ZFW remains constant.

Maximum zero fuel weight (MZFW):

the maximum weight allowed before usable fuel and other specified usable agents (engine injection fluid, and other consumable propulsion agents) are loaded.

Operating empty weight (OEW): (Roughly equivalent to basic empty weight on light aircraft)

It is the basic weight of an aircraft including the crew, all fluids necessary for operation such as engine oil, engine coolant, water, unusable fuel and all operator items and equipment required for flight but excluding usable fuel and the payload.

Payload:

It is the carrying capacity of an aircraft. It includes cargo, people, extra fuel. In the case of a commercial airliner, it may refer only to revenue-generating cargo or paying passengers.

Maximum takeoff weight (MTOW):

This is the maximum weight at which the pilot of the aircraft is allowed to attempt to take off.

Regulated takeoff weight (RTOW):

Depending on different factors (e.g., flap setting, altitude, air temperature, length of runway), RTOW or maximum permissible takeoff weight varies for each takeoff. It can never be higher than MTOW. More information is on this answer.

Maximum landing weight (MLW):

This maximum weight at which an aircraft is permitted to land.

The following image depicts takeoff weight components.

 

Maximum ramp weight (MRW)/Maximum taxi weight (MTW):

It is the maximum weight authorized for maneuvering (taxiing or towing) an aircraft on the ground.

Aircraft gross weight:

It is the total aircraft weight at any moment during the flight or ground operation. This decreases during flight due to fuel and oil consumption.

Aircraft		Max Payload	Max Range	Payload at given range							MTOW
			At Max Payload		4000		5000	6000	7000	8000
A380-800		84	6550		84	84		84	74.2	52.5	575
A350-1000		67.5	5500		67.5	67.5		62.2	50.3	38.5	316
A350-900		53.3	5700		53	53		50.3	40.1	30.0	280
A330-300		46	4200		46	37.2		26.2	15.2	4.2	242
A330-200		46	4700		46	42.8		32.2	21.6	11.0	242
B777-300ER		69.8	5700		69.9	69.9		65.4	50.7	33.4	351.5
B787-8		43.3	5500		43.3	43.3		39	30.4	21.8	227.9
B787-9		52.5	5250		52.5	52.5		45.2	35.4	25.6	254
B787-10		57.2	4200		57.2	48.7		38.1	27.6	17.0	254
B747-8		76	5900		76.1	76.1		74.1	54.2	34.3	447.7

payload and MTOW in metric tons, range in nautical miles, Numbers are rounded to the nearest half metric ton for payload and metric ton for MTOW.

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

Airspeed:

It is simply the speed at which an aircraft is moving relative to the air it is flying in. as such its also the speed at which the air is flowing the around the aircraft wings.

Ground speed:

On the other hand, is the aircraft speed relative to the ground.

The relationship between airspeed and ground speed is fairly simple. Ground speed is simply the sum of airspeed and wind speed. On the other hand, if the wind is blowing against the direction the aircraft is traveling in, the aircraft experiences headwind, and its ground speed is lower than its airspeed.

On the other hand, when the wind is blowing on the same direction to the aircraft is traveling the aircraft experience tailwind, and the ground speed is higher than the airspeed.

Example:

Imagine an aircraft that cruises at an airspeed of 500 mph that covers a ground distance of 2000 miles.

If there is no wind the aircraft reaches the destination in 4 hrs.’, in this situation the ground speed and airspeed would be the same.

If the wind is blowing with a speed of 100 mph, then the groundspeed would be lower than the airspeed, then the time to reach to destination is increased by one hour according to given above condition.

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

Taxiing refers to the movement of an aircraft on the ground, under its own power. The aircraft moves on wheels. An airplane uses taxiways to taxi from one place on an airport to another; for example, when moving from a terminal to the runway.

The aircrafts always move on the ground following the yellow lines, to avoid any collision with the surrounding buildings, vehicles or other aircrafts. The taxiing motion has a speed limit. Before making a turn, the pilot reduces the speed further to prevent tire skids. Just like cars, there is a certain list of priorities during taxiing. The aircrafts that are landing or taking off have higher priority. The other aircrafts have to wait for these aircrafts before they start or continue taxiing.

The thrust to propel the aircraft forward comes from its propellers or jet engines. Steering is achieved by turning a nose wheel or tail wheel/rudder; the pilot controlling the direction travelled with their feet. The use of engine thrust near terminals is restricted due to the possibility of jet blast damage. This is why the aircrafts are pushed back from the buildings by a vehicle before they can start their own engines for taxiing.

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

Takeoff is the phase of flight in which an aircraft goes through a transition from moving along the ground (taxiing) to flying in the air, usually starting on a runway. Usually, the engines are run at full power during takeoff. Following the taxi motion, the aircraft stops at the starting line of the runway. Before takeoff, the engines, particularly piston engines, are routinely run up at high power to check for engine-related problems. This makes a considerable noise. When the pilot releases the brakes, the aircraft starts accelerating rapidly until the necessary speed for take-off is achieved.

The takeoff speed required varies with air density, aircraft weight, and aircraft configuration (flap and/or slat position, as applicable). Air density is affected by factors such as field elevation and air temperature.

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

The takeoff distance consists of two parts, the ground run and the distance from where the vehicle leaves the ground to until it reaches to 50ft, the sum of two distances is known as takeoff distance. And the power required to take off the aircraft is known as takeoff power; it is varying with the type of aircraft using. The aircraft can be a light weight and heavy weight aircraft, not only that the takeoff power requirement can change according to the atmosphere conditions.

Some conditions that influence take off performance would be aircraft weight, temperature, pressure altitude, wind and thrust.

Full power take off is just that. The engines are brought to full power and when the aircraft reaches a certain speed (Vto), the aircraft leaves the ground.
The crew could also elect to perform a reduced power take off. The aircraft charts would be used to determine this power setting.

Tyre design:

Tyres of an aircraft is designed to withstand extremely heavy loads while landing and takeoff, taxing and parking. The number of wheels required for an aircraft is totally depends on the weight of the aircraft, the count of wheels increases with increasing in weight.

When it comes to safety, tyres are one of the most important components of aircraft, they help to absorb the shock during the time of landing and providing cushioning. It also provides necessary traction for braking and stopping of an aircraft.

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 mold.

Rolling Resistance:

Resistance offered by the tyre during the movement on the ground before taking off, is known as rolling resistance.

When taking off from a runway covered with slush, standing water or snow, the required take-off ground-run distance will be longer than on a dry runway. This is the result of the fact that slush, standing water and snow on the runway will generate a rolling resistance that increases the total resistance on the aircraft during the ground-run.  For this reason, the Joint Aviation Authorities (JAA) have established aircraft certification and operational rules accounting for runway surface conditions (see JAR  25X1591).

Tyre pressure:

Aircraft tires generally operates at high pressure, up to 200 psi, and even higher for business jets. Aircraft tires are usually inflated with nitrogen. The pressure of the tire is changes according to the weight of the aircraft. Each tyre of Boeing 777-300 ER is inflated with 200 psi and weigh up to 120kg.

The test on aircraft tyres shows that they are able to sustain under high pressure of 800psi before bursting. Before using / during the time of testing the tyres are filled with water to prevent from the energy which outcomes during bursting.

Brake force while landing:

A set of spoilers are raised when the aircraft tyres touch the ground, which decreases the lift generated by the wings during takeoff. The spoilers provide some drag which main purpose is to stop the plan from flying.

Not only that the aircraft provided with disk brakes, the aircraft comes to rest due to generation of friction force. The large amount of heat is generated while slowing the vehicle/rotation of the wheels of an aircraft.

The above shown is the arrangement of the disk brakes to the aircraft.

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

Assumptions:

Mass of an aircraft = 55 tons = 55000 kgs.

Rolling resistance for the plane would be

F_r = U_rr*m*g

U_rr = Coefficient of Rolling resistance = 0.03 between the runway and tyre.

m = mass of an aircraft

g = gravitational acceleration

F_r = 0.03 * 55000*9.81 N

F_r = 16186 N

Friction for the puller can be calculated to.

F_f = U*m*g

U = frictional coefficient between the puller tyre and runway = 0.7

16186/0.7 * 9.81 = 2616 kg.

Torque formula = F*r

T = Torque

F = Force

r = radius of the wheel

lets assume radius of the wheel 0.4m

T = 16186 * 0.4 =6474 Nm

Power required to provide to push the aircraft is

P = Power

V = Velocity of taxing vehicle

P = F * V

V = 4Kmph = 1.11mps.

P = 16186 * 1.11= 18KW

7- A. Design an electric powertrain with type of motor, its 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)

1. Also, Design the parameters in excel sheet.

Considering above power = 18KW

P = E/t

E = P*t

E = 18*10 * 60

E = 18 * 600

E = 10800Kj

The above is energy consumed for towing

N = V_o I_o/V_i I_i

P = V_i I_i

Consider DC input voltage as 48V and power as 20KW

20000 = 48 *I_i

I_i = 20000/48 = 416KW

N = 18000/20000 = 0.9 = 90% efficiency.

V_o  = 13V

Duty cycle formula:

Vavg   =         Vin*(Duty cycle)

Vavg     =          average voltage/Output voltage

Vin      =          input voltage/Supply voltage

 43 V = 48 * (duty cycle)

Duty cycle = 0.89 = 90%