Project-1: Powertrain for aircraft in runways

PART-A

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

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.

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

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

Civil Aircrafts:

All nonmilitary planes are civil aircraft. These include private and business planes and commercial airliners.

Private aircraft are personal planes used for pleasure flying, often single-engine monoplanes with the nonretractable landing gear. They can be very sophisticated, however, and may include such variants as: “warbirds,” ex-military planes flown for reasons of nostalgia, ranging from primary trainers to large bombers; “homebuilt,” aircraft built from scratch or from kits by the owner and ranging from simple adaptations of Piper Cubs to high-speed, streamlined four-passenger transports; antiques and classics, restored older aircraft flown, like the warbirds, for reasons of affection and nostalgia; and aerobatic planes, designed to be highly maneuverable and to perform in air shows.

Business aircraft are used to generate revenues for their owners and include everything from small single-engine aircraft used for pilot training or to transport small packages over short distances to four-engine executive jets that can span continents and oceans. Business planes are used by salespeople, prospectors, farmers, doctors, missionaries, and many others. Their primary purpose is to make the best use of top executives’ time by freeing them from airline schedules and airport operations.

They also serve as an executive prerequisite and as a sophisticated inducement for potential customers. Other business aircraft include those used for agricultural operations, traffic reporting, forest-fire fighting, medical evacuation, pipeline surveillance, freight hauling, and many other applications. One unfortunate but rapidly expanding segment of the business aircraft population is that which employs aircraft illegally for transporting narcotics and other illicit drugs. A wide variety of similar aircraft are used for specialized purposes, as the investigation of thunderstorms, hurricane tracking, aerodynamic research and development, engine testing, high-altitude surveillance, advertising, and police work.

Antonov An-225 Mriya - 640,000 kg

Boeing 747-8 - 447,700 kg

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.

Lighter-than-air:

Aircraft such as balloons, nonrigid airships (blimps), and dirigibles are designed to contain within their structure a sufficient volume that, when filled with a gas lighter than air (heated air, hydrogen, or helium), displaces the surrounding ambient air and floats, just as a cork does on the water. Balloons are not steerable and drift with the wind. Nonrigid airships, which have enjoyed a rebirth of use and interest, do not have a rigid structure but have a defined aerodynamic shape, which contains cells filled with the lifting agent. They have a source of propulsion and can be controlled in all three axes of flight. Dirigibles are no longer in use, but they were lighter-than-air craft with a rigid internal structure, which was usually very large, and they were capable of relatively high speeds.

Airship - 130,000kg (Empty weight) ,

Weight : 250,000 kgs

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

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

Aerodynamic forces are generated by an object moving through a fluid (liquid or gas). A fixed object in a static fluid does not generate aerodynamic forces. Hot air balloons "lift" because of buoyancy forces and some aircraft like the Harrier use thrust to "lift" the vehicle, but these are not examples of aerodynamic lift. To generate lift, an object must move through the air, or air must move past the object. Aerodynamic lift depends on the square of the velocity between the object and the air. Now things get confusing because not only can the object be moved through the air, but the air itself can move. To properly define the relative velocity, it is necessary to pick a fixed reference point and measure velocities relative to the fixed point. In this slide, the reference point is fixed to the ground, but it could just as easily be fixed to the aircraft itself. It is important to understand the relationships of wind speed to ground speed and airspeed.

Wind Speed

For a reference point picked on the ground, the air moves relative to the reference point at the wind speed. Notice that the wind speed is a vector quantity and has both a magnitude and a direction. The direction is important. A 20 mph wind from the west is different from a 20 mph wind from the east. The wind has components in all three primary directions (north-south, east-west, and up-down). In this figure, we are considering only velocities along the aircraft's flight path. A positive velocity is defined to be in the direction of the aircraft's motion. We are neglecting crosswinds, which occur perpendicular to the flight path but parallel to the ground, and updrafts and downdrafts, which occur perpendicular to the ground.

Ground Speed

For a reference point picked on the ground, the aircraft moves relative to the reference point at the ground speed. Ground speed is also a vector quantity so a comparison of the ground speed to the wind speed must be done according to rules for vector comparisons.

Airspeed

The important quantity in the generation of lift is the relative velocity between the object and the air, which is called the airspeed. Airspeed cannot be directly measured from a ground position but must be computed from the ground speed and the wind speed. Airspeed is the vector difference between ground speed and wind speed.

Airspeed = Ground Speed - Wind Speed

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

For movement on the ground the aircraft uses it own engine power, which is called taxing.

Although many aircrafts are capable of moving in backward using reverse thrust, as result the jet blast or prop wash might cause damage to the terminal building or equipment. Engine close to ground may also blow sand and debris forward and then suck them into the engine, causing damage to the engine.Therefore there are pushback trucks in the airport. A pushback truck lifts the front weel of the aircraft, their role in most airports is to move the aircraft awayfrom the parking spot on to the taxiways, which is called towing.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.

Although most aircraft are capable of moving themselves backwards on the ground using reverse thrust, a procedure called as a powerback, it is not typically done due to the following reasons:

• The jet blast from the engines can damage the terminal building and nearby equipment. It can even throw away people standing nearby.
• 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.
• Engines can suck in sand and debris which can cause serious damage to the engine.
• It is easier for the truck driver to see the surroundings better than the pilot sitting in the cockpit with limited windows.
• The plane engines are very loud. This noise can add up substantially when multiple planes 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 trucks will push the plane all the way to the runway to save fuel and reduce impact on nearby environment.

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

Towing:

Movement of large aircraft about the airport, flight line, and hangar is usually accomplished by towing with a tow tractor (sometimes called a “tug”). 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.

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 (for water-based travel).

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.

Some types of tow bars available for general use can be used for many types of towing operations. [Figure 2] These bars are designed with sufficient tensile strength to pull most aircraft, but are not intended to be subjected to torsional or twisting loads. Many have small wheels that permit them to be drawn behind the towing vehicle going to or from an aircraft. When the bar is attached to the aircraft, inspect all the engaging devices for damage or malfunction before moving the aircraft.

Some tow bars are designed for towing various types of aircraft. However, other special types can be used on a particular aircraft only. Such bars are usually designed and built by the aircraft manufacturer.

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

Takeoff is the phase of flight in which an aerospace vehicle leaves the ground and becomes airborne.

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 (VTOL aircraft such as the Harrier), no runway is needed. Takeoff is the opposite of landing.

Take off performance 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 – Thrust of propulsion system pushing aircraft along runway.

D – Aerodynamic Drag of vehicle resisting the aircraft motion.

F – Rolling resistance friction due to the contact of wheels or skids on the ground.

During take-off run the imbalance in these forces will produce an acceleration along the runway.

dVdt=T-D-F/m

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 climb lift and it will ascend from the ground. The determination of this safe flying speed or rotation speed, V_R, is a critical factor in determining take-off performance.

Small commuter aircraft :

For safety reasons V_R is usually determined as being 1.1 × V_STALL or 1.05 × V_{MIN CONTROL}

which ever is greater. Stall speed, V_STALL, is the lowest speed that the aircraft can be flown before the airflow starts to separate from wings as the angle of attack becomes too great. The wing is assumed in this case to be in take-off configuration or "clean".

It can be calculated based on knowledge of the aircraft take-off configuration and hence the maximum achievable lift coefficient C_L(max). As shown in the previous section , to maintain level flight the lift produced must equal the weight, hence the stall speed can be calculated as,

Vstall=W12CL(max)ρS">Vstall=√W12CL(max)ρS������=�12��(max)��

Minimum control speed, V_MC is a more complex calculation and requires knowledge of the stall characteristics of the tailplane and elevator. For conventional aircraft there is only a small difference between V_R calculations based on stall speed or minimum control speed.

As well as rotation speed there are other safety considerations as shown in the following Figure.

V₁- Abort decision speed. Below this speed the take-off can be safely aborted. After this there will not be sufficient runway length to allow the aircraft to decelerate to a stop.

V₂ – Safe climb speed. V₂ must be no less than 1.2 * V_stall. Below this speed aircraft cannot attain sufficient climb rate.

Transport Aircraft :

V_R must not be less than V₁
V_R must be greater than 1.05 * V_MC
V_R must be set so that aircraft achieves V₂ before reaching a height of 35ft above the runway surface.

Thrust:

The thrust of gas turbine or turbofan engines will be relatively constant during take-off. A good assumption is to use the manufacturer's values for maximum static thrust for take-off calculations.

T=Pshaft×ηV">T=Pshaft×η/V

It is critical to correctly estimate the propeller efficiency for the particular aircraft velocity along the runway. At V=0 the efficiency is 0 so the above equation makes no sense. At V=V_R the efficiency will be in the range 50% to 80% depending on the type of propeller system used and the thrust value at this point will be easy to obtain. In practice, the thrust obtained throughout the take-off roll is roughly constant so this end point value is a good approximation from V=0 to V=V_R.

b.Tyre Design of aircrafts :

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.

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.

Carcass plies are used to form the tire. They are sometimes called casing plies. An aircraft tyre is constructed for the purpose it serves.

Unlike an automobile or truck tyre, it 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.

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 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 mould.

Aircraft tyres must have an approved speed and load rating and have sufficient 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.

d.Tyre Pressure :

Car tyres aren’t just unsafe when they’re old and worn out – you need to ensure you know what tyre pressure you have in your tyres when you drive it because there are critical safety and economic implications.

Car tyre pressure is a measurement of how much air is in your pneumatic tyre, and ensures the tyres wear evenly and maintain the correct level of grip on the road surface. This is commonly expressed as PSI, or pounds-per-square-inch.

Braking 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 maingear assembly. On landing, pilots should use aerodynamic braking by applying extra back-pressure on the stick or yoke. Extreme caution should be used whenapplying brakes at any signi􀂦cant speed, and only when the end of the runway is quickly approaching. Never step on the brakes to make a runway exit. Applyingthe brakes at too high a speed could burn the tires, wear out the brakes, or result in a ground loop or swerve.

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PART-B

6.A. With necessary assumptions, 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, 3 type of forces will act on that vehicle. Those are -(i) Rolling resistance force (ii) Aerodynamic dragforce and (iii)Hill climbing force.

(i) Rolling resistance force(Frr) :

Rolling resistance is the force resisting the motion when a body rolls on a surface. It is the friction force that is needed to beovercome to move a vehicle

Frr = urr * m * g where, urr= Rolling resistance co-efficient (It depends on the tire material , tire structure, tire temperature, road roughness, road material etc.) m= Total mass of the vehicle (vehicle mass + payload) in kg g = gravitational constant , that is 9.8 m/s^2.

Here in this case for towing vehicle for aircraft urr= 0.013.

i) Aerodynamic drag force(Fad) :

Aerodynamic drag force is the force which is required to keep a vehicle moving. There are two component of this force , one isshape drag (due to the shape of the vehicle) and another is skin friction (due to friction between air and skin of the vehicle). When the vehicle moves the velocityof air near boundary is higher than the air surrounding. Both the tug and the aircraft will experience some aerodynamic drag.

Fad = (1/2) * ρ * V^2 * A * (Cd_t + Cd_a)

where, ρ = Air density, that is normally 1.25 kg/m^3

A = Frontal area of the vehicle in m^2

Cd_t = Air drag co-efficient of towing vehicle (It depends on frontal area,shape, protrusions, ducts, air passage etc.)

Cd_a = Air drag co-efficient of aircraft (Itdepends on frontal area, shape, protrusions, ducts, air passage etc.)

v =Velocity of the vehicle in m/s

In this case air drag co-efficient for towing vehicle(Cd_t)= 0.5 and for aircraft or payload(Cd_a)= 0.045.

(iii) Hill climbing force(Fhc) :

Hill climbing force is the force needed to move the vehicle in up gradient. To Hill Climbing force the expression of the equation isgiven below-

Fhc = m * g * sinφ

where, m = Total mass of the vehicle(vehicle mass + payload) in kg

g = Gravitational constant that is 9.8 m/s^2

φ = up gradient angle or inclination angle in radian

In this case up gradient angle(φ) = 0, as there is no inclination.

Push/Pull Power Calculation of Towing Vehicle-

B. Develop the model for the calculated force and power using Simulink.

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7. A. Design 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.

Assumption For Powertrain Design
Aircraft Mass (kg)	575,000 kg
Towing Vehicle mass (kg)	50,000 kg
Rolling Resistance Co-efficient	0.013
Air Density	1.225 kg/m3
Towing Vehicle Drag Co-efficient	0.5
Aircraft Drag Co-efficient	0.09
Frontal area	20 m2
Inclination angle	0 rad
Tyre Pressure	203 PSI/14 bar
Towing Velocity(V)	10 km/h = 2.778 m/s
Towing Time(t)	15 min
Radius of the towing vehicle wheel	0.38 m

Transmission Effeciency (nt) =87%

Motor Efficiency (nm)=95%

Gear ratio=8

then,

Torque required for the wheels (Tw)=Total Force *Radius in meters

=80.047 *0.38

=27.21KNm

Motor Torque-Wheel torque/(Gear ratio'nt)

=27.21/(8 *0.87)

=2.959KNm
For nm =95%. The required motor Torque (Tm)= 2.959/0.95 =3.1148 kNm

Similarly. The total power required by the motor considering all the efficiencies (Pt) = 221.52/(0.87*0.95)=241.88Kw

Let us assume the towing operation was done for a 15 minutes (0.25Hrs) duration.

Then, Total Energy consumed = 241.88* 0.25=60.47 KWh

If we consider the battery capacity=300 kw is used by the towing vehicle then. The duty cycle range to control the speed from O to max speed (3m/s) is given as

Duty Cycle (d)= (Required Power)/ (Rated power)= 241.88/300 =0.80

Therefore the controller will be able to provide a duty cycle ranging from 0 to 80% in order to control the towing speed.

B. Also, Design the parameters in excel sheet.