Project-1: Powertrain for aircraft in runways

Aim

Part A:

1. Search and list out the total weight of various types of aircrafts.
2. There any difference between ground speed and air speed
3. Why is not recommended to use aircraft engine power to move it on the ground at airport?
4. How an aircraft is pushed to runway when its ready to take off?
5. Learn about take off power, rolling resistance, tyre pressure, brake force when landing.
6. A.with necessary assumptions, calculate the force and power required to push/pull an aircraft by a towing vehicle.

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

7. A.design an electric powertrain with the type of motor, its power rating, and energy requirement to fulfil 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 the powertrain.

B.also design the parameters in an excel sheet.

Solution

Q1.

Types of aircrafts

an aircraft is a vehicle that can fly by gaining support from air. It counters the force of gravity either static lift or by using the dynamic lift of an air foil or in a few cases the downward thrust from jet engines.

Types of engine

• Turboprop aircraft
• Piston aircraft
• Jets
• Narrow – body aircraft
• Wide body airlines
• Airbus
• Military aircraft

Types of aircrafts and weight

• Antonov an – 225 mriya

It is powered by six turbofan engine and is the heaviest aircraft ever built with a maximum take off weight of 640 tonnes

• Airbus A380-800: empty weight 611,000lbs 277,000kg Maximum gross take off weight 1,268,000lbs 575,000kg

• Boeing 747-800: empty weigh 485,300lbs 220,100kg Maximum gross take off weight 987,000lbs 447,700kg

• Airbus A340 – 500: empty weigh 370,000lbs 168,000kg Maximum gross take off weight 820,000lbs 372,000kg

• Boeing 777 – 300ER: empty weigh 370,000lbs 168,000kg Maximum gross take off weight 776,000lbs 352,000kg.

• Glider:110kg – 200kg

A glider is a fixed-wing aircraft that is supported in flight by the dynamic reaction of the air against its lifting surfaces, and whose free flight does not depend on an engine. Most gliders do not have an engine.

• Powered lift: 160kg

A powered lift aircraft takes off and lands vertically under engine power but uses a fixed wing for horizontal flight. Like helicopters, these aircraft do not need a long runway to take off and land, but they have a speed and performance similar to standard fixed-wing aircraft in combat or other situations.

• Fighter aircraft: 13500kg

Fighter aircraft are fixed-wing military designed primarily for air-to-air combat. In military conflict, the role of fighter aircraft is to establish air superiority of the battlespace

• Transport planes: 250,000kg

A military transport aircraft, military cargo aircraft or airlifter is a military-owned transport aircraft used to support military operation by airlifting troops and military equipment. Transport aircraft are crucial to maintaining supply lines toforward bases that are difficult to reach by ground or waterborne access, and can be used for both strategic and tactical missions. They are also often used for civilian emergency relief missions by transporting humanitarian aid

• Aerobatic planes: 771kg

An aerobatic aircraft is any craft that is heavier than air (aerodyne) which can be used in flight exhibitions, aerobatic competitions, and the like. For the most part, any aerobatic aircraft will fall into one of two main categories: training and aerobatics.

Q2

Yes there is difference between the ground and the air speed. With reference to the above image. Lets go to differentiate the ground speed and air speed.

Ground speed is the aircraft speed relative to the ground that it explains how speed can aircraft travel in the ground. It is not dependent on the airspeed.

Here air speed is the relative motion between the objective and the air. This is also an important parameter for aerodynamic lift generation. This air speed of the object cannot be measured directly from the ground, it depends upon the ground and the wind speed in fact it is the vector difference between the ground and wind speed.

Q3

The movement of an aircraft on the ground under its own power is called taxing. But to move the aircraft from hanger to the runway the term used is the taxiways.

Although many aircraft are capable of moving in backward using reverse thrust as a result the jet blast or prop wash might cause damage to the terminal building or equipment.

The risks which may arise from engine ground running relate to the aircraft by those persons occupying the pilot seats in the fight deck. In most cases such persons will be maintenance personnel holding specific company – issued approval for the required task. The consequences of loss of control during taxi or towing are the same as apply to these operations generally and this article is concerned only with the risks arising from the static running of one or more aircraft engines.

Unwanted consequences from such static running are mainly related to those arising from the unintended movement of the aircraft during engine running – effectively a loss of control especially during high power engine running.

Damage can occur to the aircraft itself other aircraft nearby or to airside structures. In addition there is a risk of injury to ground support personnel who may be in relatively close proximity to the aircraft.

Q4

Taxing

It is defined as the movement of the air – craft on the ground under its own power where as towing or pushback is where the air craft is moved by the tug. The air craft usually moves on wheels but the term also used for the air craft that has skies or floating equipment. An airplane uses taxiways to taxi from one place on the air-port to another from hanger to the runway

Towing

Movement of large aircraft about the airport, flight line and hanger is usually accomplished by towing with a two 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. However specific instruction for each model of aircraft are detailed in the manufacturing maintenance instruction and are to be followed in all instance. When towing the aircraft, the towing vehicle speed must be reasonable and all persons involved in the operation must be alert. When the aircraft is stopped do not rely upon the brakes of the towing vehicle alone to stop the aircraft. The person in the flight deck must coordinate the use of the aircraft brakes with those of the towing vehicle.

Q5

Take – off power

The amount of power that an engine is allowed to produce for a limited period of time for take-off. The use of take – off power is usually limited to 5min for reciprocating engines and up to 2.30min for gas turbine engines. this may not always be the case. Specifically with respect to reciprocating engines it is the brake horsepower developed under the maximum conditions of the crankshaft rotational speed and the engine manifold pressure approved for the normal take-off.

It is limited in continuous use to the period of time shown in the approved engine specifications. With respect to gas turbine engines, it is the thrust developed under static conditions at a specified altitude and atmospheric conditions of the rotor shaft rotational speed and gas temperature approved for the normal take-off.

It is limited in continuous use to the period of time shown in the approve engine specifications.

Take – off power= force * displacement i.e. (m*dv/dt)*2*S1=>(T-D-F)*S1

Where Sis the runway length. the force involved are T- thrust of propulsion system D- aerodynamic drag which the vehicle resists F- rolling resistance due to the contact on wheels on the ground

Tyre design

The tires help to absorb the shock of landing and provide cushioning.it also provides the necessary traction for the braking and stopping of an aircraft. An aircraft tire is designed to with stand 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 airplane needs to be distributed more evenly.

Design

Carcass piles are used to form the tire. They are sometimes called casing piles. An aircraft tire 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 the braking and stopping of an airplane.

Tyre also helps to absorb the shock of landing and provides cushioning for the roughness of take-off, roll-out and taxi operation.

Unlike an automobile or truck tire it does not have to carry a load for long period of continuous operation. Aircraft tires are manufactured with tread rubber with conducting compounds to permit earthing of static charges.

Rolling resistance

Rolling resistance sometimes called rolling friction or rolling drag is the force resisting the motion when a body rolls on a surface. It is mainly caused by non-elastic effects that is not all the energy needed for deformation of the wheel, roadbed etc. is recovered when the pressure is removed.

Two forms of this are hysteresis losses and permanent deformation of the object or the surface. Note that the slippage between the wheel and the surface also results in energy dissipation. Although some researchers have included this term in rolling resistance some suggest that this dissipation term should be treated separately 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.

Tyre pressure

Aircraft tires generally operate at high pressures up to 200psi(14bar,1400kpa) for airliners and even higher for business jets. The main landing gear on the concorde was typically inflated to 232psi(16.bar) whilst its tail bumper gear tire were as high as 294psi (20.3 bar).

Aircraft tire are usually inflated with nitrogen to minimize expansion and contraction form extreme changes in ambient temperature and pressure experienced during flight. dry nitrogen expands at the same rate as other dry atmospheric gases but common compressed air sources may contain moisture which increases the expansion rate with temperature.

Landing brake forces

On other aircraft tyres the brake units are powered by the hydraulics system. An electrical signal is sent from the flight deck to hydraulic actuators near the main landing gear. Here hydraulic fluid at 3000 pounds per square inch is used to force the brake unit against the wheel thus slowing it down.

Q6.A

The force acting on an aircraft during the push and pull of the towing vehicle are rolling resistance air drag force.

Assumptions:

Let as assume an aircraft of Antonov an-255 plane

Mass of the aircraft m1=24000kg

Mass of the towing vehicle m2=50000kg

Coefficient of rolling ground friction for dry concrete Urr = 0.03

Frontal area of the vehicle A = 35m^2

Drag coefficient of an aircraft Cd(aircraft)= 0.6

Drag coefficient of a towing vehicle Cd(towing)= 0.15

Density of air p=1.225 kg/m^3

Gravity g =9.81 m/s^2

Speed of an aircraft =20kmph = 20 * (5/18)

=5.556m/sec

Rolling resistance force

for the aircraft

Frra= Urr * m*g

Frra=0.03 * 247000* 9.81

Frra=72692.1N

For the towing vehicle

Frrv= Urr * m *g

Frrv=0.03*50000*9.81

Frrv=14715 N

Aerodynamic drag force

Fad =(1/2) * p * A *v^2 *(Cda + Cdt)

Fad=(1/2)*1.225*3355*5.556^2*(0.6+0.15)

Fad=4750.47 N

Total force of the towing vehicle

F=Fad + Frrv

F= 4750.47 + 87407.1

F= 9.2157.57N

Power required

P= F*v

P=92157.57 * 5.556

P = 512.027 KW

The force and power of the towing vehicle carrying the aircraft are 92.157 KN and 512.027KN

Q6.B

The Simulink model was created as shown below for calculating rolling resistance ,aerodynamic drag force and total power by using sum, constant, product, divided and display blocks.

Now run the model and check thee force and power values.

The value of the rolling resistance force is 87.41KN, aerodynamic drag force is 4750N, the total force is 92.16KN and the power is 512KW.

Q7.A

We can use the above parameters and can use the electric powertrains

An airplane pushback vehicle is required to move airplanes away from airport terminals and tow them across the airfield for routine maintenance. The pushback vehicle must be able to generate a large towing force but it also has a high speed to trave quickly between pushback operations.

Let the wheel radius be 0.5m

Maximum torque on wheels

T = wheel radius * force

T = 0.5 * 92157057

T = 46078.785N-m

Let as assumed the induction motor with the given parameters

Input power in terms of mechanical power be 560KW

Duty cycle = output power / input power

=512/560 = 0.91428

= 91.428%

The heavy duty factor for an aircraft is designed for operating extreme local conditions

Q7.B

link for excel sheet and simulink model;https://drive.google.com/file/d/1h95dj0KBxGP6whuGGebMGd4HHTVW-f2Y/view?usp=sharing