Project-1: Powertrain for aircraft in runways
1. Search and list out the total weight of various types of aircrafts.
ANSWER:
1. Aircraft Gross Weight:
The aircraft gross weight (also known as the all-up weight and abbreviated AUW) is the total aircraft 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, an 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, although motor glider have small engines for extending their flight when necessary by sustaining the altitude (normally a sailplane is on a continuously descending slope) with some being powerful enough to take off self launch.
Weight of Glider planes : 110 kg - 200 kg
2.Powered Lift
A powered lift aircraft takes off vertically under engine power but uses a fixed wing for horizontal flight. These aircraft do not need a long runway to take off and land, like helicopters , but they have 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 combat 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 : 13500 kgs
4.Transport Planes :
Military transport aircraft or military cargo aircraft are used to airlift troops, weapons and other military equipment to support military operations. Transport aircraft can be used for both strategic and tactical missions, and are often diverted to civil emergency relief missions.
Weight : 250,000 kgs
5.Aerobatic 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
POWERTRAINS WITH WEIGHT:
2.Is there any difference between ground speed and air speed?
ANSWER:
| Ground Speed | Air speed |
| Ground speed is the airplane’s speed relative to the surface of the Earth | Airspeed is the speed relative to the air it is flying in. |
| Ground speed is what determines how fast an aircraft will get to its destination | Airspeed is what determines whether there is enough airflow around an aircraft to make it fly |
| Ground speed is simply the sum of airspeed and wind speed. | It is independent of ground speed. |
FOR BETTER UNDERSTANDING WE ARE ATTACHING THE IMAGES OF BOTH DIFRRENCES:
3. Why is it not recommended to use aircraft engine power to move it on the ground at Airport?
ANSWER:
-Generally most of the airplane can move itself in reverse manner by making use of reverse thrust technology.But in most of the practical it is not possible because when airplanes start using reverse thrust it will consume lot of fuels as well as causes lot of noise and also hazardous for the people working near by.
-The another for not using reverse thrust is that the jet blast can cause damage to terminal buildings or its equipments.Since the engine is also close to the ground it will blow off the sand and debreis forward and sucks it to the engine and causes damage to it.
-To solve this kind of issue we use a towing vehicle which helps to tow the vehicle in reverse dierection and it eill be tugged until it reaches a safe place and from there onwards airplane will move by itself for further take off.
TOWING VEHICLE :
- A) Aircraft can move using their own engine power all the time on the airport apron and taxiways under their own power to go towards runways and after landing taxi to their assigned gate. But the thrust produced resulting jet blast might cause damage to the terminal building or equipment. 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. And also it can reduce the cost for fuel. Taxiing can save money.
- Effectively a loss of control can happen, especially during high power engine running. Damage can occur to the aircraft itself, other aircraft nearby or to airsidestructures. • There is a risk of injury to ground support personnel who may be in relatively close proximity to the aircraft.
It is easier for truck driver to see the surroundings better than the pilot sitting in the cockpit with limited window. The pushback driver knows the airport better than the pilot.It also saves fuel virgin Atlantic hadproposed a new system in which pushback truck will move the aircraft all the way to runway to save fuel and reduce impact of environment.The plane engines are very loud. When more than one plane will add up their sound, than it will not be pleasent for passangers and others near airport.
4. How an aircraft is pushed to runway when its ready to take off?
ANSWER:
A)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.
Towing:
Movement of large aircraft about the airport, flight line, and hangar is usually accomplished by towing with a tow tractor. In the case of small aircraft, some moving is accomplished by hand pushing on the correct areas of the aircraft. Aircraft may also be taxied about the flight line but usually only by certain qualified personnel.Towing aircraft can be a hazardous operation, causing damage to the aircraft and injury to personnel, if done recklessly or carelessly. This article outline the general procedure for towing aircraft. However, specific instructions for each model of aircraft are detailed in the manufacturer's maintenance instructions and are to be followed in all instances.
5. Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.
ANSWER:
Take off power:
Take off power can be predicted using a simple measure of the acceleration of the aircraft along the runway based on force equilibrium.
The forces involved will be.
T is Thrust of propulsion system pushing aircraft along the runway.
D is Aerodynamic Drag of vehicle resisting the aircraft motion.
F is Rolling resistance friction due to the contact of wheels or skids on the ground.
During the take-off run, the imbalance in these forces will produce an acceleration along the runway.
m*(dv/dt)=T-D-F
where, dv/dt is the acceleration along the runway and m is the mass of the vehicle.
The procedure for take-off will be that the vehicle will accelerate until it reaches a safe initial flying speed. The pilot can then rotate the vehicle to an attitude to produce a climb lift and it will ascend from the ground The determination of this safe flying speed or rotation speed V. is a critical factor in determining take-off performance Take-off
rules vary slightly depending on the aircraft category.
For Small commuter aircraft
V=1.1*VSTALL
V=1.05*V control
VSTALL =√(W/0.5CtmaxρS)
where S-Runway length
Take off power= force*displacement
(m*dv/dt)*2*s1 = (T-D-F)*S1
Tyre design :
Designing aircraft tires is a very intense undertaking The tyre is designed to withstand 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. Aircraft tyre generates more heat during landing Aircraft drags the wheel until they match the rotational velocity of wheels. Due to this heat generates. Aircraft's tread pattern is designed to facilitate stability in high crosswind conditions, to channel water away to prevent hydroplaning and for braking effect.
Construction of tyre :
Radial Tyre: It has fibre strands of the ply fabric oriented at 90° to the direction of rotation and the tyre sidewall. This restricts flexibility bidirectional and the flexibility of the sidewall while it strengthens the tyre to carry heavy loads. Due to their unique construction most radial tyres are resistant to penetration ad cuts. Due to stiffer tread they distribute weight evenly. Thus provide greater traction. Radial tyres have an advantage in term of reducing the heat better.
Bias-ply Tyre: It has the fabric bias oriented with and across the direction of rotation and the sidewall. Since fabric can stretchon the bias, the tyre is flexible and can absorb loads. Tyre strength is obtained by adding plies. It is cut resistant is sidewall area. These tyres do not offer as much smoothness in terms of riding quality.
Rolling Resistance:
Rolling resistance is the force resisting the motion when a body (such as ball, tyre or wheel) rolls on a surface. Rolling resistance can be seen in the aircraft when the aircraft takes-off from the runway & while landing at the runway with the help of their wheels.
Rolling resistance can be expressed as Fm g (N).
Where
Frr the Rolling resistance(N)
μrr coefficient of rolling resistance.
m is mass(kg)
g is acceleration due to gravity= 9.81m/s^2
Tyre pressure :
Aircraft tyres operate at such high extremes of pressure, load, and speed, their care and service is critically important. The most important action an operator can take to prevent tyre-related events is to maintain proper tire inflation pressure. Failure to keep aircraft tires properly inflated can lead to very serious consequences. One relatively easy way to help avoid those consequences is to check tire pressures regularly and service them as necessary. Following these three actions is a good way to make sure you get the most value out of your tires and contribute to the safe operation of your aircraft.
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,
Also, the use of an inert gas for tire inflation eliminates the possibility of tire explosion.
Relation to Rolling Resistance and Tire Pressure:
Rolling resistance and tire pressure are inversly proportional.
Braking Forces during Landing :
Following braking devices are used to decelerate the aircraft -
- Spoilers.
- Wheel Brakes (Including Anti-Skid systems & Auto-Brake systems)
- Reverse Thrust
Spoilers:
The mechanical deflection of parts of the wing upper surface 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 and also by increasing the effective downward load on the landing gear and thereby increasing the efficiency of wheel braking
Wheel Brakes:
To be effective, braking action at any speed depends upon sufficient friction existing between the tires and the runway surface achieved through freely rotating wheels.
Anti skid system:
When landing on slippery runways, there's a chance that the wheels may start to skid as the brakes are applied. To stop this from happening and to maintain maximum effective braking, each wheel has anti-skid protection.
Using a variety of sources to determine the aircraft speed, the brake units know how fast the wheels should be spinning. If that speed drops significantly, it's because the current brake pressure on that wheel is too great and the wheel is just skidding over the surface.
In this situation, the anti-skid system automatically reduces the braking on that wheel to a point where the skid stops before reapplying the pressure.
Reverse Thrust :
Reverse Thrust:
Thrust reversers provide a deceleration force that is independent of runway condition. Thrust reverser efficiency is higher at high airspeed therefore. Treversers must be selected as early as possible after touchdown.
Thrust reversers should be returned after reverse idle at low airspeed to prevent engine stall or foreign object damage.
PART B :
- With necessary assumptions, calculate the force and power required to push/pull an aircraft by a towing vehicle.
ANSWER:
The forces required to push/ pull an aircraft by a towing are rolling resistance force and areodynamic drag force.
1) Rolling resistance force:- As we have discussed t is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface. Its governing equation is given as
F = CN
F=C*m*g
where,
Crr= Rolling resistance coefficient m=Mass of the body g= acceleration due to gravity
2)Aerodynamic Drag Force:
It is the force opposing the motion of the body. The drag coefficient is a common measure in automotive design as it pertains to aerodynamics, Drag is a force that acts parallel to and in the same direction as the airflow. The drag coefficient of an automobile measures the way the automobile passes through the surrounding air. When automobile companies design a new vehicle, they take into consideration the automobile drag coefficient in addition to the other performance characteristics. Aerodynamic drag increases with the square of speed; therefore, it becomes critically important at higher speeds. Reducing the drag coefficient in an automobile improves the performance of the vehicle as it pertains to speed and fuel efficiency. The governing equation of these force is given as following:
where.
F{D} = drag force
rho = density of the air
น = flow velocity relative to the object
C{D} = drag coefficient
A = reference area
Calculation:
let us assume that,
Mass of Towing Vehicle= 40,000kg
Mass of aircraft = 155,000kg
Total mass (m)= 40,000+155,000 =195,000kg
acceleration due to gravity inm/s^2=9.8
Frontal Area of the aircraft (A) =18 m²
Speed of the vehicle (2)=25Kmph
converting it into m/sec
u=25*(1000/3600)=6.9445m/sec
Drag coefficient (Cd) =0.75
Air density (P)=1.225Kg/m³
Calculating Rolling resistance Force (Frr) =Crr*m*g
=0.01*195.000*9.8
= 19.11ON
Calculating Aerodynamic Drag Force (Fd)=0.5*p Cd*A* v^2
=0.5 *1.225 *18* 0.75* (6.9445)2
=398.769N
Therefore the total Force required to push/pull the aircrcraft by the towing vehicle (F) Frr+Fd
=19,110+398.769
=19,508.769 N
Calculating the power (p) =Force*Velocity
= 19508.769* 6.9445
=135.478kW
B. Developing the model for the calculated force and power using Simulink:
Blocks Used:
1) Constant
2) Sum
3) Product
4)Square
5)Display
Simulink Model:
FOR Rolling resistance Force (Frr)
FOR Aerodynamic Drag Force (Fd)
WHOLE MODEL WITH ALL CALCULATIONS :
Explaination:
In order to understand the above simulink model we do reverse engineering
• For calculating power we have to multiply both total force(F) and velocity in m/sec for this we have used 'product' block (P-FV).
• For calculating the Total Force(F) we have added both Frr & Fd by using 'Sum' block as shown in the above figure
• To find the value of rolling resistance (Frr) we used product to multiply the values Crr., Total mass(m) & gravity (g) which are to be entered in the 'Constant block.
. Similarly for calculating Drag force(Fd) we have to multiply the velocity in m/sec.Drag coefficient, Frontal area of aircraft(A) and a constant value 0.5 which are to be entered in constant block.
• In order to convert velocity in Kmph to m/sec we have multiplied it with 5/18.
7) A. Designing an electric powertrain with type of motor, it's 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.
Block Diagram of Powertrain:
Figure shows the Towing Vehicle Application
| Assumation for Powertrain Design | |
| Parameter | Value |
| Aircraft Mass | 150000 Kg |
| Towing Vehicle Mass | 40000 Kg |
| Rolling Resistance Co-efficient | 0.01 |
| Air Density | 1.225 Kg/m^3 |
| Towing Vehicle Drag Co-efficient | 0.608 |
| Aircraft Drag Co-efficient | 0.15 |
| Frontal Area | 18 m^2 |
| Inclination Angle | 0 rad |
| Tyre Pressure | 196 PSI/13.51 bar |
| Towing Velocity(V) | 10 Km/hr = 2.778 m/s |
| Towing Time(t) | 2 min |
| Radius of the Towing Vehicle Wheel | 0.4 m |
Now from the above calculation we get the Total Force acting on the Vehicle as:
Total Traction Force(F) - 18877.93056N
Power Required (P) - 104.877392kW
Now, The Torque required by the vehicle to move is given by:
Torque(T) - Force(F)*Radius of the Wheel(R)
Therefore, T = 18877.93056*0.4
= 7551.1722Nm
The Energy required by the vehicle for Towing application is given by:
Energy(E) = Power(P)*Towing Time
= 104.877392*2/60
= 3.496kWh
For this application an electric motor which can be either a BLDC motor or an Induction Motor is choosen for the above power specs is given below:
Here in the above figure, the Peak Motor Output Power given in the Motor Parameters in the input to the Towing Vehicle:
So therefore, Input Power to the Towing Vehicle(kW) - 120
Output Power of the Towing Vehicle(kw) - 104.877392
∴∴, Duty Cycle = OutputPowerInputPowerOutputPowerInputPower;
= 104.877392/120
= 0.87
ThereforeTherefore Duty Cycle = 87%
RESULT:
So we can say that to control the Aircraft Speed from Zero to Highest the Duty Cycle Range will be from 0 to 87% respectively.
The Power Train Block Diagram for the entire Towing application starting from the Aircraft to the Towing Vehicle is given below:
From the diagram we can see that the Battery is supplying the power to the Motorand that is controlled by the Controller unit which is nothing but the Inverter Circuitry. As automotive batteries generally operates on DC while the grid operates on AC, so a converter is needed to transfer power to the battery. Because of these capability of EV vehicle, the efficiency of them are much more(80-60%) than the conventional IC engine type of vehicle(25-30%). This motor is then responsible for controlling the wheels and the brakes through the Transmission and the Gear System.