Project-1: Powertrain for aircraft in runways
Solution:
1. list out the total weight of various types of aircrafts
Aircraft Gross Weight:
The aircraft gross weight (also known as the all-up weight and abbreviated AUW) is the total weight at any moment during the flight or ground operation.
An aircraft's gross weight will decrease during a flight due to fuel and oil consumption. An aircraft's gross weight may also vary during a flight due to payload dropping.
At the moment of releasing its brakes, the gross weight of an aircraft is equal to its takeoff weight. During flight, ana aircraft's gross weight is referred to as the en-route weight or in-flight weight.
Weight of Various Types of Aircraft Weight :
1. Glider
Glider is a fixed wing plane that is supported in flight by the dynamic reaction of the air against its lifting surfaces, and whose free weight does not depend on an engine. Most gliders do not have an engine, altough motor glider have small engines for extending their flight when necessary by substaining the altitude (normally a sailplane is on a continuously descending slope) with some being powerful enough to take off launch.
Weight of Glider planes : 110 Kg - 200 Kg
2. Powered Lift
A poerted lift aircraft take soff vertically under engine power but uses a fixed wing for horizontal flight. These aircreaft do not need a long runway to take off and land, like helicopters, but they hace a speed and performance similar to standard fixed wing aircraft in combat or other situations.
Weight : 160 Kgs
3. Fighter Aircraft
A fighter aircraft, often referred to simply as a fighter, is a military fixed wing aircraft designed primarily for air to air combar against other aircraft. The key performance features of a fighter include not only its firepower but also its high speed and manuverability relative to the target aircraft.
Weight : 13500Kgs
4. Transport Planes :
Military transpport aircraft or military cargo aircraft are used to airlift troops, weapons and other military equiptments to support military operations. Transport aircraft can be used for both strategic and tractical missions, and are often diverted to civil emergency relief missions.
Weight : 250,000 Kgs
5. Aeroplane Planes
An aerobatic aircraft is an aerodyne (a heavier-than-air aircraft) used in aerobatics, both for flight exhibitions and aerobatic competitions.
Weight : 771 Kgs
2. Difference betwween ground speed and air speed:
Ground Speed
- Ground speed is the airplane's speed relative to the surface of the Earth
- Ground speed is what determines how fast an aircraft will het to its destination
- Ground speed is simply the sun of airspeed and wind speed.
Air speed
- Airspeed is the speed relative to the air it is flying in.
- Airspeed is what determines whether there is enough airflow around an aircraft to make it fly
- It is independent of ground speed.
3. Why it is not recommended to use aircraft engine power to move it on the ground at Airport?
For movement on the ground the aircrafts uses its own engine power, which is called Taxing.
Towing is coupling two or more objects together so that they may be pulled by a designated power source or sources. The towing source may be a motorized land vehicle, vessel. animal. or human, and the load being anything that can be pulled.
Altough many aircraft are capable of moving themselves backwards on the ground using reverse thrust (a precedure referred to as a powerback), the resulting jet prop might cause damage to the terminal building or equiptment. Engines close to the ground may also blow sand and debris forward and then suck them into the engine, causing damage to the engine. A pushback is therefore the preferred method to move the aircraft away from the gate.
Although most aircraft are capable of moving themselves backwards on the ground using reverse thrust, a precedure called as a powerback, it is not typically done due to the follong reasons:
- The jet blast from the engines can damage the terminal building are nearly equipment. It can even throw away people standingnearby.
- Engines can blow sand and debris.
- Engines can suck in sand and debris which can cause series damage to the engines.
- 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. Thisnoise can add up substantially when multiple places 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 truck will push the plane all the way to the runway to save fuel and reduce impact on nearby environment.
Taxing 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 (for water-based travel).
The power for taxing comes from the engines itself. It is a propeller powered aircraft, the propeller provides thrust and pulls the aircraft, like it would in air. If it is a jet engine, the exhaust air that come out of the engine creates a forward force due to Newton's third law and moves the airplane.
Airplane have nose wheel steering, controlled by a cockpit control called a tiller. The tiller allows noes wheel to rotate at quite extreme angles making tighter turns possible. It also reduces the fuel consumption as you do not need much engine power during taxing. If rudders were used, the power has to be increased to make sure sufficient air flows over the rudder surface to make it effective.
Once on the take off call and the airplane gains sufficient speed i.e. enough air flows over the rudders, pilots go back to using the rudder pedals to maintain centre line.
Some large airplanes with multi wheel main gears have a tendency to scrub the tyres on the tarmac when nose wheel is steered. To counter this problem, an automatic main gear steering is inbuilt in the aircraft. This makes the main gears turn the opposite direction to that of the nose wheel, greatly decreasing the wear on the tyres.
Small general aviation aircrafts uses the rudder for turna during taxi. They dont have a seperate control for nose wheel. In such airplanes, to make tighter turns, you could use differentiaol braking. That is, if you want to make a tight turn for example to the left, you would push the upper part of your left rudder pedal which would apply left braking. This allows the airplane to make a sharper turn to the left.
4. Aircraft pushed to runway when its ready to take off.
TOWING :
Pusubacks at busy aerodromes are usuaally subject to ground control clearance to facilitate ground movement on taxiways. Once clearance is obtained, the pilot will communicate with the tractor driver (or a ground handler walking alongside the aircraft in some cases) to start the pushback. To communicate, a headset may be connected near the nose gear.
Since the pilots cannot see what is behind the aircraft, steering is done by the pushback tractor driver and not by the pilots. Depending on the aircraft type and airline procedure, a bypass pin may be remporarily installed into the nose gear to disconnect it from the aircraft's normal steering mechanism.
Once the pushback is completed, the towbar is disconnected, and any bypass pin removed. The ground handler will show the bypass pin to the pilots to make it clear it has been removed. The pushback is then complete, and the aircraft can taxi forward under its own power.
TAXING :
Taxing (rarely spelled taxying) is the movement of an aircraft on the ground, under its own power, in contrast to towing or pushback where the aricraft is moved by a tug. The aircraft usually moves on wheels, but the term also includes aircraft with skils or floats (for water-based travel). 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 acceleratig run along a runway prior to takeoff, or the decelerating run immediately after landing, which are called the takepff roll and landing rollout, respectively.
Takeoff is the phase of flight in which an aerospace vehicle leaves the ground and becomes airborne. For aircraft travelling vertically, this is known as liftoff. For aircraft that take off horizontally, this usually involves starting with a transition from moving along the ground on a runway. For balloons, helicopters and some specialized fixed-wing aircraft such as the Harrier), no runway is needed.
5 : About take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.
Take Off Power:
For light aircraft, usually full power is used during takeoff. Large transport category (airliner) may use a reduced power for takeoff, where les than full power is applied in order to prolong engine lige, reduce maintenance costs and reduce nose emissions. In some e=mergency cases, the power used can then be increased to increase the aircraft's performance. Before takeoff, the engines, particularly piston engines, are routinely run up at high power to check for engine-related problems.
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 speed for jetliners are in the rang of 24-285 Kn/h (130-154 Kn; 149-177 mph). Light aircraft, such as a Cessna 15, take off at around 100 Kn/h (54 Kn; 62 mph). Ultralights have even lower takeoff speeds. For a given aircraft, the takeoff speed is usually dependent on the aircraft weight; the heavier the weight, the greater the speed needed. Some aircraft are specifically designed for short takeoff and landing (STOL), which they achieve by becoming airborne at very low speeds.
Tyre Design :
When it comes to safety, tyres are one of the most impoertant components of aricrafts. They help to absorb of landing and provide cushioning. It also provides the necessary traction for braking and stopping of an aircraft. 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.
A Boeing 737NG & 737MAX uses 6 wheels, Boeing 787 uses 10 wheels, Boeing 777 uses 14 wheels and Airbus A380 uses 22 wheels. Aircraft tyres work under extreme conditions, carrying up to 340 tons and accelerating at over 250 Km/hour at takeoff, in addition to enduring varied environmental stress when in flight and taxing.
Design and Construction of Aircraft tyre :
Carcass piles are used to form the tire. They are sometimes called casing piles. An aircraft tyre is constructed for the purpose it serves.
1. They support the weight of an aircraft while it is on the ground.
2. It also provides the necessary traction for braking and stopping of an aeroplane.
3. Tyre also helps to absorb the shock of landing and provide cushioning the roughness to takeoff, roll-out, and taxi operations.
Unlike an automobile or trucl tyre, it does not have to arry a load for a long period of continous 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.
Aircraft Tyre Construction
Let's go through some technical aspects of the tyre.
Retreading - Retreading is methods of restoring a worn tyre by renewing the tread area or by renewing the tread area plus one or both sidewalls. Repairs are included in the tyre retreading process.
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 strenght.
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 mould.
Aircraft tyres must have an approved speed and load rating and have stufficient clearance when retracted through landing gear to allow for tyre growth. Tyre growth is the increase in the size of the tyre due to centrifugal forces at high speed.
Aricraft tyres may be Radia or Bias:
Almost airliners are using tyre. Bias is an older desgn, and it's mainly used for road vehicles. Radial tyres have the word RADIAL on the sidewall. Radial tires are more expensive than bias=ply tyres. Radial tires are in demand because of their lower life cycle cost and long term value.
Are aviation tyres are conductive?
Yes, Today's tyres are conductive. Aircraft tyres are manufactured with tread rubber with conducting compounds to permit earthing of static charges.
In early days, when tyres were not sufficiently conductive, aircraft used to have a conductive strip hanging down from the axle of the landing gear. Upon landing, the strip would be the first part of the aricraft to touch the earth. The discharges my electricity accumulation the outer surfaces of the aircraft. Now you don't see them anymore.
What is the purpose of chines in aviation tyre:
Chines are also called deflectors. Chine tyre used on the nose wheel of aircraft, specially fuselage-mounted het engines. It diverts runway water away from the engine inlets.
Chines are circumferential protusions that are moluded 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.
Aircraft Tyre Standards:
Each tyre manufacturer produces their own designs of the tyre with different tread patterns, wear limits etc., and in some cases, different names for the same part of the tyre. But all tyres must meet the approved standards before accepted by the FAA or CAA. All commercial aircraft tyres approved under FAA Requirement Technical Standard Order (TSO) C62. A TSO is a minimum performance standard for specified materials, parts, and appliances used on civil aircraft.
Rolling Resistance:
Rolling resistance sometimes called rolling friction or rolling drag, is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface. It is mainly caused by non-elastic effects that is, not all the energy needed for deformation (or movement) of the wheel, roadbed etc., is recovered when the pressure is removed. Two forms of this are hysteresis losses (see below), and permanent (plastic) deformation of the object or the surface (e.g. soil). Note that the slippage between the wheel and the surface also results in energy dissipation. Altough some researchers have included this term in rolling resistance, some suggest that the dissipation term should be treated seperately from rolling resistance because it is due to the applied torque to the wheel and the resultant slip between the wheel and ground, which is called slip loss or slip resistance. In addition, only the so-called slip resistance involve friction, therefore, the name "rolling friction" is to an extra a misnomer.
Rolling Resistance Force Frr = Urr. m. g
m = mas sof the aircraft
g = fravitational constant = 9.8 m/s^2
In analogy with sliding friction rolling resistance often expressed as a coefficient times the normal force. This coefficient of rolling resistance is generally much smaller than the coefficient of sliding friction.
Any coasting wheeled vehicle will gradually slow down due to rolling resistance including that of the bearings, but a train car with steel wheels running on steel rails will roll farther than a bus of the same mass rubber times running on the tarmac. 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. The losses due to hysteresis also depend strongly on the material properties of the wheel or tire and the surface. For example, a rubber tire will have higher rolling resistance on a paved road than a steel raolroad wheel on a steel rail. Also, sand on the ground will give more rolling resistance than concrete. Sole rolling resistance factor is not dependent on speed.
Tyre Pressure:
Aircraft times generally operate at high pressure up to 200 ps (14 bar, 1,400 kPa) for airliners, and even higher for business jets. The main landing gear on theConcorde was typically inflated to 232 psi (16.0 bar), what its tail bumper gear tires were as high as 294 psi (203 bar).
A Boeing 777 fully weights around 700,000 pounds and has fourteen tires:
Therefore, if each of those tires is reacting roughly the same force, then that is 50,000 pounds per tire.
I am cheating bit, because I don't have a close up picture of one of those main tires when the plane weights 700,000 pounds. But the article, above claims that the tire pressure is 200psi. Therefore there should be 250 square inches of surface contact area for each tire with the ground (250*200=50,000) and 250 in area would be 25 inches by 10 or more likely 16X16 inches.
Brakes Force:
Stopping an aircraft landing at 180-200 mph requires a lot of braking force. To do this, the aircraft has brake unit on each of the wheels on the main gear assembly. On landing, Pilots should use aerodynamic braking by applying extra back-pressure on the strick or yoke.
Aircraft disc brakes in the landing gear, 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 ("toe brakes"). In the some older aircraft the bottom section is used instead ("heel brakes"). Levers are used in a few aircraft. Most aircraft are capable of differential braking.
Thrust reversersL That allow thrust from the engines to be used to slow the aircraft.
Air brakes: It is dedicated flight control surfaces that work by incresing drag.
Drogue parachutes: It is used by several former and current military and ocivilian aircraft (examples include the American B-52 and the soivet Tu-134 and Tu-144) and in the Space Shuttle.
6:A. Calculate the force and power required to push / pull an aircraft by a towing vehicle.
To push or pull an aircraft by a towing vehicle is have three types of forces will act on that vehicle.
Those are
- Rolling Resistance Force
- Aerodynamic Drag Force
- Hill Climbing Force
Push/Pull Power Calculation of Towing Vehicle
Let's assume,
Towing Vehicle mass = 50000 kg
Aircraft mass = 183700 kg
Total mass of the vehicle = (50000+183700) 233700 kg
Speed of the vehicle (V) = 10 Km/hr = 2.77 m/s
Rolling Resistance Force
Frr = urr . m. g
= 0.013 . 233700 . 9.8
= 29,773.38N
Aerodynamic Drag Force
F_ad =1/2 ρ⋅v^2⋅A⋅(C_ⅆ_t )+C_ⅆa )
= (1/2) . 1.225 . (2.778)^2 . 20 . (0.5+0.045)
= 51.514N
Hill Climbing Force
F_hc = m . g . sin∅
= 233700 . 9.8 . sin0
= 0N
Total Traction Force
F_te = F_rr+F_ad+F_hc
= 29773.38+ 51.514+0
= 29824.894N
Total Power = (F_tr . V)/1000
= 82.84 KW
6B. To develop the model for the calculated force and power using Simulink
'
Main Model:
7.a: Design an electric powertrain with type of motor, it's power rating, and energy requirement to fulfill aircraft towing application.
Assumation for powertrain Design
Parameter Value
Aircraft mass 183700kg
Towing Vehicle Mass 50000kg
Rolling Resistance Co-efficient 0.013
Air Density 1.225Kg/m^3
Towing Vehicle Drag Co-efficient 0.5
Aircraft Drag Co-efficient 0.045
Frontal Area 20 m^2
Inclination Angle 0 rad
Tyre Pressure 203 PSI/14 bar
Towing Velocity(V) 10 Km/hr = 2.778 m/s
Towing Time(t) 2 min
Radius of the Towing Vehicle Wheel 0.38 m
Therefore from the above model, we have calculator the Traction Force = 29824.8927 N
Power = Force*Velocity
= 29824.8927 . 0.38
P = 82.84KW
As we know Torque(T) = Force(F)* Wheel Radius(r)
T = 29824.9025 . 0.38
T = 11333.45N - m
Required Energy (E) for towing application based on the assumed time, that is E=P*t
E = 82.82 . (120/3600)
E = 2.760KWh
For this application an induction motor or a BLDC can be used with a proper gear system
Induction Motor Rating
Parameters Rating
Output Power 90 KW
Horse Power 120 H.P
Input term of Mechanical Power 95.642 kW
No. of Phases 3
Input Voltage 380V,400V,415V
Input Current 163.3 A,155.1 A,149.5 A
Efficiency 94.10%
Tthe Motor power is the input power of the towing vehicle so to obtain maximum speed, the duty cycle needed is calculated as below;
DutyCycle = Output Power/Input Power
= (82.82/90) . 100
The duty cycle range to control the aircraft speed from zero to highest is from 0 to 92%
MAIN MODEL:
Result:
Block diagram of powertrain for Towing Vehicle
Electrical vehicles, consist of a battery, connected to an electric motor via an inverter and a motor controller. As automotive batteries generally operate on DC current, while grids operate on AC current a converter is needed to transfer power to the battery. One of the Key advantages of an EV is much higher levels of energy efficiency.
7B.To design the parameters in excel sheet.