Project-1: Powertrain for aircraft in runways
1. Total weight of various types of aircrafts.
Type MTOW [kg] MLW [tons]
Antonov An-225 640,000 91.7
Scaled Composites Model 351 Stratolaunch 589,670
Airbus A380-800 575,000 394
Boeing 747-8F 447,700 346.091
Lockheed C-5 Galaxy 381,000 288.417
McDonnell Douglas MD-11 273,300 185
Ilyushin Il-96M 270,000 195.04
Concorde 185,000 111.1
Vickers VC10 152,000 151.9
Douglas DC-8-61 147,000
Tupolev Tu-154M 104,000 80
Convair 880 87,500
de Havilland Comet 4 70,700
Hawker Siddeley Trident 2E 65,000
Embraer 190[18] 48,000 43
Caravelle III 46,000
Fokker 100 46,000 39.95
Avro RJ-85 42,000 36.74
Handley Page Hermes 39,000
Embraer 175[19] 37,500 32.8
Bombardier CRJ900[20] 36,500 33.345
Beechcraft 1900D 7,765 7.605
Cessna Citation CJ4[25] 7,761 7.103
de Havilland Hercules 7,000
Embraer Phenom 100 4,800 4.43
Manufacturer's empty weight (MEW)
It 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. This excludes any baggage, passengers, or usable fuel2.
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 progresses and fuel is consumed, the total weight of the airplane reduces, but the ZFW remains constant. Maximum zero fuel weight (MZFW) is 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 off3.
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 land3.
Maximum ramp weight (MRW) also called 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.
Refrences:
https://en.wikipedia.org/wiki/List_of_airliners_by_maximum_takeoff_weight
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2) Difference between ground speed and air speed.
True air speed 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.
Ground speed, on the other hand, is the aircraft’s speed relative to the ground. Ground speed is simply the sum of airspeed and wind speed.
One thing that should be noted here is that ground speed is horizontal rather than vertical speed – an aircraft climbing completely vertically would have a ground speed of zero. In other words, while airspeed is what determines whether there is enough airflow around an aircraft to make it fly, ground speed is what determines how fast an aircraft will get to its destination.
Refrences:
https://www.knaviation.net/airspeed-and-ground-speed/
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3) It is not recommended to use aircraft engine power to move it on the ground at Airport.
Aircrafts moving on grounds is known as taxiing. Taxi speeds are typically 30 to 35 km/h (16 to 19 kn)
The exhaust wake from the aircraft engines can pose hazards in commercial airport environments.
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. 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.
That's why we are switching to motor drives taxiing instead of using jet engines.
Refrences:
http://www.boeing.com/commercial/aeromagazine/aero_06/textonly/s02txt.html
https://en.wikipedia.org/wiki/Taxiing
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4) How an aircraft is pushed to runway when its ready to take off.
Taking aircraft till runway is called taxiing of aircraft and for the accelerating run along a runway prior to takeoff, or the decelerating run immediately after landing, are called the takeoff roll and landing rollout, respectively.
So, taxiing is done by generating thrust to propel the aircraft forward, from its propellers or jet engines. Reverse thrust for backing up can be generated by thrust reversers or reversible pitch propellers.
After lining up on runway and cleared for take-off, the pilot will start to advance thrust by propelling fans or by operating jet engines. After spooling of engines it is safe to advance the thrust levers together to the position that will enable the engines to deliver the amount of thrust required for take-off. The required thrust should be attained before the aeroplane’s indicated air speed passes 80kts. The specified speed is typically 80 knots. Below this speed the take-off may be rejected for any reason.
Lifting up is done when the wings are lifting the weight of the airplane off the surface. In most airplanes, this is the result of the pilot rotating the nose up to increase the angle of attack (AOA). The nose is raised to a nominal 5°–15° nose up pitch attitude to increase lift from the wings and effect liftoff. For most aircraft, attempting a takeoff without a pitch-up would require cruise speeds while still on the runway.
Refrences :
https://en.wikipedia.org/wiki/Taxiing
https://www.skybrary.aero/index.php/Take-off_and_Climb_-_A_Guide_for_Controllers
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5) Take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.
Take off power: Take off is the phase of flight in which an aerospace vehicle leaves the ground and becomes airborne and the power required to fullfill this task is Take off power. For aircraft that take off horizontally, this usually involves starting with a transition from moving along the ground on a runway. It is needed becuase for a given aircraft, the takeoff speed is usually dependent on the aircraft weight; the heavier the weight, the greater the speed needed. So speed is achieved by running on runways. The speeds needed for takeoff are relative to the motion of the air (indicated airspeed). A headwind will reduce the ground speed needed for takeoff, as there is a greater flow of air over the wings. Typical takeoff air speeds for jetliners are in the range of 240–285 km/h (130–154 kn; 149–177 mph). Light aircraft, such as a Cessna 150, take off at around 100 km/h (54 kn; 62 mph). Ultralights have even lower takeoff speeds. After this the nose is raised to a nominal 5°–15° nose up pitch attitude to increase lift from the wings and affect liftoff.
So, power required to do all this task is accounted into take off power. Most takeoffs use "derated" thrust to save engine wear. For each takeoff, performance is calculated, the necessary power setting is determined and the thrust setting is made. When using this method during takeoff, it is always possible to increase to full power if the situation requires. The captain always makes the final decision whether to use full thrust or derate.
Tyre Design:
When it comes to safety, tyres are one of the most important components of aircraft. They help to absorb the shock of landing and provide cushioning. It also provides the necessary traction for braking and stopping of an aircraft. And all this is for short times.
An aircraft tyre is designed to withstand extremely heavy loads while landing, take off, taxing and parking. The number of wheels required for aircraft increases with the weight of the aircraft, as the weight of the aeroplane needs to be distributed more evenly.
Tyres are radial type and tubeless. Aircraft tyres are conductive too as they are manufactured with tread rubber with conducting compounds to permit earthing of static charges.
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.
Chines are also called deflectors. Chine tyre used on the nose wheel of aircraft, specially fuselage-mounted jet engines. It diverts runway water away from the engine inlets.
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 body rolls on a surface. It is experienced during take off and landinf of aircraft.
Factors that contribute to rolling resistance are the amount of deformation of the wheels, the deformation of the roadbed surface, and movement below the surface. Additional contributing factors include wheel diameter, load on wheel, surface adhesion, sliding, and relative micro-sliding between the surfaces of contact.
We also have a constant for calculation of rolling resistance force known as coefficient of rolling resistance depnds upon typre pressure and velocity.
c = 0.005 + (1 / p) (0.01 + 0.0095 (v / 100)2)
Where,
c = coefficient of rolling resistance
p = tyre pressure in bar
v = velocity of vehicle in Km/H.
Aircraft tyre pressure:
Aircraft tires generally operate at high pressures, up to 200 psi (14 bar; 1,400 kPa) for airliners, and even higher for business jets. The main landing gear on the Concorde was typically inflated to 232 psi (16.0 bar), whilst its tail bumper gear tires were as high as 294 psi (20.3 bar).
Tests of airliner aircraft tires have shown that they are able to sustain pressures of maximum 800 psi (55 bar) before bursting. During the tests the tires have to be filled with water, to prevent the test room being blown apart by the energy that would be released by a gas when the tire bursts.
Aircraft tires are usually inflated with nitrogen to minimize expansion and contraction from extreme changes in ambient temperature and pressure experienced during flight. Dry nitrogen expands at the same rate as other dry atmospheric gases (normal air is about 80% nitrogen), but common compressed air sources may contain moisture, which increases the expansion rate with temperature.
Brake forces when landing:
The three primary methods of achieving deceleration on the runway during the landing roll or a rejected take off are engine power, brakes and mechanical spoilers. Effective and co-ordinated use of whichever of these are available will result in a stopping distance appropriate to the available runway ahead, or the desired runway exit point if sooner. The key to success is the properly co-ordinated use of all the available methods.
Engine Power: In this the focus is to select all thrust/power levers to the ground idle position promptly, and if available, continue the action through to the selection of reverse thrust or reverse propeller pitch. Selection at these relatively high speeds must be symmetrical because otherwise, directional control may be prejudiced.
Wheel Brakes: It depends upon sufficient friction existing between the tyres and the runway surface achieved through freely rotating wheels. These ensure adequate wheel rotation exists and is maintained before the commanded brake pressure is transmitted to the brake units and takes effect.
An electrical signal is sent from the flight deck to hydraulic actuators near the main landing gear. Hydraulic fluid pressure is used to force the brake unit against the wheel, thus slowing it down. But this resulted in less efficiency due to increase in weight. So we switched to electrical braking, i.e. when the pilots press on the brake pedals, an electrical signal is sent to the brake unit on the wheel. Here, electrically powered actuators are used to press the carbon brake disc against the wheel, slowing it down. Here, when the pilots press on the brake pedals, it 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.
Mechanical Spoilers : This is done by increasing aerodynamic drag on the moving aircraft. This can be achieved by raising upper wing surface panels called ground spoilers or by operation of a tail cone ‘clamshell’ type air brake. Both systems can also be used in the air on some aircraft types as in-flight air brakes, but the extent of their operation may be less in the airborne case than in the ground (weight on wheels) case.
Refrences:
https://en.wikipedia.org/wiki/Takeoff
https://www.aviationhunt.com/aircraft-tyre-construction/
https://en.wikipedia.org/wiki/Rolling_resistance
https://www.engineeringtoolbox.com/rolling-friction-resistance-d_1303.html
https://en.wikipedia.org/wiki/Aircraft_tire
https://thepointsguy.com/guide/how-do-aircraft-brakes-work/
https://www.skybrary.aero/index.php/Deceleration_on_the_Runway
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6) The force and power required to push / pull an aircraft by a towing vehicle.
Refrences:
https://www.engineeringtoolbox.com/plane-pull-force-people-d_2083.html
https://www.engineeringtoolbox.com/rolling-friction-resistance-d_1303.html
http://wattsaviation.co.uk/products-and-services/tyre-sizes-explained.html
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7) An electric powertrain with type of motor, it’s power rating, and energy requirement to fulfill aircraft towing application.
As, from the above solution we found the necessary values of certain quantities to tow the aircraft i.e.
Power = 29.37795 KW
Torque = 1860.6035 Nm
Energy = 0.979265 KWH
All these values are based upon certain assumptions and for aircraft convair 880 ( Mass = 87500 Kg) assuming its
Tyre Pressure = 14 bar
Towing Velocity = 6 Km/H
Radius of wheel = 0.380 m
Towing time = 2 minutes
the values we got after considering these values are the least value to tow this airliner. Now to find the maximum value of duty cycle we need to find the input power supplied to airliner to get this values of parameters required to tow the airliner.
As, vehicle speed needs to be varied for better control so it is done using different values of duty cycle which is actually done by varying voltage supply to motor. And as we know by studying speed control stratageies for EV power is varied using different voltage values.
So, Duty Cycle can be written as
Duty Cycle = Power Output / Power Input
As, we already have power output value now we only need to find power input value which now has to be again assumed for this model.
As,
Power = Voltage * Current ;
Assuming
Input Voltage supply ( Battery Specification ) = 450V;
Input current value = 75 A:
So,
Power Input = 450 * 75 = 33.75;
So, duty cycle will be
Duty Cycle = Power Output / Power Input = 29.37795 / 33.75 = 0.87
So, Duty Cycle will be 0 - 87% for our syatem based upon several assumptions.
Assuming Motor type to be Brushless DC motor as the speed range is very less for towing so this kind of motor will be sufficient enough for system.
Block Diagram Of Electric Vehicle.