Project-1: Powertrain for aircraft in runways

Part A:

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

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

3. Why is it 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, tyre design, rolling resistance, tyre pressure, brake forces when landing.                                                                                

Part B:

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 the calculated force and power using Simulink.

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. 

(Hint :DC7 Block)

    B. Also, Design the parameters in excel sheet.

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

Maximum takeoff weight (MTOW)

The maximum takeoff weight (also known as the maximum brake-release weight) is the maximum weight authorised at brake release for takeoff, or at the start of the takeoff roll.

The maximum takeoff weight is always less than the maximum taxi/ramp weight to allow for fuel burned during taxi by the engines and the APU.

In operation, the maximum weight for takeoff may be limited to values less than the maximum takeoff weight due to aircraft performance, environmental conditions, airfield characteristics (takeoff field length, altitude), maximum tire speed and brake energy, obstacle clearances, and/or en route and landing weight requirements.

Maximum landing weight (MLW)

The maximum weight authorised for normal landing of an aircraft.

The MLW must not exceed the MTOW.

The operation landing weight may be limited to a weight lower than the Maximum Landing Weight by the most restrictive of the following requirements:

• Aircraft performance requirements for a given altitude and temperature:

landing field length requirements,

approach and landing climb requirements

• Noise requirements

If the flight has been of short duration, fuel may have to be jettisoned to reduce the landing weight.

Overweight landings require a structural inspection or evaluation of the touch-down loads before the next aircraft operation.

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

One of the most confusing concepts for young scientists is the relative velocity between objects. 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. 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 cross winds, which occur perpendicular to the flight path but parallel to the ground, and updrafts and downdrafts, which occur perpendicular to the ground.

• If the windspeed is in the same direction of aircraft ,the speed of aircraft increases as shwon in the  fig.a
• If the wind speed is in the opposite direction of aircraft, the speed of aircraft decreases as shown in the fig.b.  

                                 fig a.

       fig b.

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 the ground speed and the wind speed.

On a perfectly still day, the airspeed is equal to the ground speed. But if the wind is blowing in the same direction that the aircraft is moving, the airspeed will be less than the ground speed.

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

 Aircraft Engine power is not recommended to move on the ground at airport according to  the following.

• Using ground tugs to move airplanes on the ground does save fuel in Airplanes.
• It also allows for precise parking as the tug driver can see the area around the airplane better than the pilot can from the flight deck
•  Some aircraft can do a so-called ‘powerback’, but in most cases, airplanes either don’t have this technical capability. Most airplanes can taxi backwards by using reverse thrust. This entails directing the thrust produced by the plane’s jet engines forward, rather than backwards. This method is often used in jet aircraft to brake as quickly as possible after touchdown. It’s also used when making an emergency stop. In some countries, pilots can still taxi their aircraft backwards to their heart’s content, but you’ll never see this at Schiphol. And for good reasons.

 

3. Connecting the air-con

The APU also energizes the plane's climate control systems, hopefully keeping the cabin at a nice temperature while parked. Like ground power, some airports provide conditioned air through large-diameter flexible ducts that plug into a port on the belly of the plane.

Or you might see a truck-mounted unit doing the job, with a duct snaking to the plane. Large, wide-body aircraft need two air connections to keep the cabin comfortable.

4. De-planing

The passengers inside the plane have jumped up, and they're waiting impatiently in the aisle to get off -- right now.

If the gate is equipped, a passenger boarding bridge is positioned by the forward left-side doors.

Otherwise, truck- or cart-mounted stairs roll up, and passengers experience the excitement of walking down the stairs and onto the ramp, being able to look back at their aircraft.

Smaller regional jets and turboprops sit close to the ground, and have stairs built into the inside of the plane's doors, with just a couple of steps to the ramp.

 

5. Unloading the luggage and cargo

 

Pods filled with passengers' bags are handled by a purpose-built machine.

Howard Slutsken

On the right side of the plane, the ramp team has swung into action. After opening the doors to the baggage and cargo holds, a belt-loader or a pod-loader is positioned, depending on the aircraft.

"Rampie" is the industry term for airline employees who load and unload planes.

The rampie inside the belly of a single-aisle plane places each piece of luggage onto the belt, and their partner takes it off the belt and puts it into a baggage cart.

The carts head to the baggage room, and the luggage is dropped onto a conveyor, hopefully showing up on a carousel soon after you've arrived.

Wide-body planes carrying hundreds of passengers needed an efficient way of handling luggage and cargo, so baggage and cargo pods were developed back when jumbo jets first appeared.

Pods are filled with passengers' bags, and handled by a purpose-built machine. One rampie can operate it, and make the pods dance on the loader's platform or in a plane's holds by activating powered wheels.

6. Stocking up with food

Catering trucks join the crowd outside the plane's fuselage. Rising on a scissor lift, the truck's box matches the height of the plane's galley doors.

The catering crew replaces used galley carts with newly stocked ones, each cart coded for a specific location in the galleys.

To service the double-deck Airbus A380 mega-jet, catering trucks reach way up, to the upper galley doors.

7. Cleaning the toilets

Perhaps it's not the most desirable ramp job, but somebody's got to empty the plane's lavatory holding tanks, and refill the fresh water system. Just like a recreational vehicle, this doesn't happen during every stop.

Rampies position a truck- or cart-mounted tank and pump unit, and connect hoses to do the work.

 

8. Refueling

Like your car, a plane's fuel tanks aren't necessarily filled at every stop.

An airline's operations team will have figured out how much fuel is needed for each leg of a plane's daily routing, and when to refuel.

Big tanker trucks connect to the plane's fuel system under the wing, or a pumper truck will hook up to a fuel hydrant in the ramp, then to the jet's tanks, and pump away.

9. Pushback

Pushback is when an aircraft is pushed backwards away from the airport gate by vehicles called tugs or tractors.

Closer to departure, an aircraft tug will park right in front of the nose wheel.

The tug might be directly attached to the plane's nose gear with a tow bar, or could be a "wheel-lift" tug. These tugs cradle the nose gear, then lift it up before moving the plane. That gives the tug driver control over the plane's direction during pushback.

New taxi technologies are appearing, like pilot-controlled tugs, and electric motors mounted to the plane's landing gear. Both promise to save fuel, and reduce airport noise.

Related content

 

10. Boarding and take-off

The crew has finished all the pre-flight preparations, the cabin door is closed, and you're settled into your seat. Your journey begins with a gentle push, in reverse, and you're anticipating the adventures to come.

 

After all checking and  following all instructions completed than aircraft is moved to takeoff position .

 

These are instructions to aircraft is pushed to runway when its ready to take off

 

The following towing and parking procedures are typical of one type of operation. They are examples and not necessarily suited to every type of operation. Aircraft ground-handling personnel must be thoroughly familiar with all procedures pertaining to the types of aircraft being towed and local operation standards governing ground handling of aircraft. Competent persons that have been properly checked out direct the aircraft towing team.

• The towing vehicle driver is responsible for operating the vehicle in a safe manner and obeying emergency stop instructions given by any team member.
• The person in charge assigns team personnel as wing walkers. A wing walker is stationed at each wingtip, in such a position that he or she can ensure adequate clearance of any obstruction in the path of the aircraft. A tail walker is assigned when sharp turns are to be made or when the aircraft is to be backed into position.
• A qualified person occupies the pilot’s seat of the towed aircraft to observe and operate the brakes as required. When necessary, another qualified person is stationed to watch and maintain aircraft hydraulic system pressure.

• The person in charge of the towing operation verifies that, on aircraft with a steerable nosewheel, the locking scissors are set to full swivel for towing. The locking device must be reset after the tow bar has been removed from the aircraft. Persons stationed in the aircraft are not to attempt to steer or turn the nosewheel when the tow bar is attached to the aircraft.
• Under no circumstances is anyone permitted to walk or to ride between the nosewheel of an aircraft and the towing vehicle, nor ride on the outside of a moving aircraft or on the towing vehicle. In the interest of safety, no attempt to board or leave a moving aircraft or towing vehicle is permitted.
• The towing speed of the aircraft is not to exceed that of the walking team members. The aircraft’s engines usually are not operated when the aircraft is being towed into position.
• The aircraft brake system is to be charged before each towing operation. Aircraft with faulty brakes are towed into position only for repair of brake systems, and then personnel must be standing by ready with chocks for emergency use. Chocks must be immediately available in case of an emergency throughout any towing operation.
• To avoid possible personal injury and aircraft damage during towing operations, entrance doors are closed, ladders retracted, and gear-down locks installed.
• Prior to towing any aircraft, check all tires and landing gear struts for proper inflation. (Inflation of landing gear struts of aircraft in overhaul and storage is excluded.)
• When moving aircraft, do not start and stop suddenly. For added safety, aircraft brakes must never be applied during towing, except upon command by one of the tow team members in an emergency situation.
• Aircraft are parked in specified areas. Generally, the distance between rows of parked aircraft is great enough to allow immediate access of emergency vehicles in case of fire, as well as free movement of equipment and materials.
• Wheel chocks are placed fore and aft of the main landing gear of the parked aircraft.
• Internal or external control locks (gust locks or blocks) are used while the aircraft is parked.
• Prior to any movement of aircraft across runways or taxiways, contact the airport control tower on the appropriate frequency for clearance to proceed.
• An aircraft parked in a hangar must be statically grounded immediately.

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

Take off power of aircraft

The amount of power that an engine is allowed to produce for a limited period of time for takeoff. The use of takeoff power is usually limited to 5 min for reciprocating engines and up to 2½ min for gas turbine engines. This may not always be the case. Specifically, with respect to reciprocating engines, it is the brake horsepower developed under standard, sea-level conditions and 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 takeoff. It is limited in continuous use to the period of time shown in the approved engine specifications.

For light aircraft, usually full power is used during takeoff. Large transport category (airliner) aircraft may use a reduced power for takeoff, where less than full power is applied in order to prolong engine life, reduce maintenance costs and reduce noise emissions. In some emergency 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 aircraft is permitted to accelerate to rotation speed (often referred to as V_r). The term rotation is used because the aircraft pivots around the axis of its main landing gear while still on the ground, usually because of gentle manipulation of the flight controls to make or facilitate this change in aircraft attitude (once proper air displacement occurs under / over the wings, an aircraft will lift off on its own; controls are to ease that in).

Rolling resistance coefficient '`mu_(rr)`

                            Rolling Resistance Coefficient μrr is defined by μ_R = F/G, where F is the force necessary to pull the axle of a tire horizontally in the direction of travel, and G is the vertical load on the tire which is assumed to roll on a flat horizontal surface.

Rolling resistance force

                            Force resisting the motion when a body rolls on a surface. It is mainly caused by non-elastic effects, deformation of the wheel, roadbed, etc.

                       

                                    `F_(rr)=mu_(rr)*m*g`.

 Thus rolling resistance of aircraft tyre is 0.01 or less than 0.01

   

Tyre pressure and 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.

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 taxiing.

Design and Construction of Aircraft tyre

Carcass plies are used to form the tire. They are sometimes called casing plies. 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 of takeoff, roll-out, and taxi operations.

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.

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 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.

Aircraft tyres may be Tube-type or Tubeless

Tubeless tyres are more advantageous over tube-type. There is no longer the use of tube-type tyre in recent aviation. Nowadays all airliners are using tubeless tyres. Tubeless that are meant to be used without a tube has the word TUBELESS on the sidewall of the tyre.

Aircraft tyres may be Radial or Bias

Almost all airliners are using Radial tyre. Bias is an older design, 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, this strip would be the first part of the aircraft to touch the earth. This discharges any static electricity accumulated on 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 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.

Aircraft Tyre Standards

Each tyre manufacturer produces their own designs of the tyre with different tread patterns, wear 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 being 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.

 Pressure of tyre

An aircraft tire or tyre is designed to withstand extremely heavy loads for short durations.The number of tires required for aircraft increases with the weight of the aircraft, as the weight of the airplane needs to be distributed more evenly. Aircraft tire tread patterns are designed to facilitate stability in high crosswind conditions, to channel water away to prevent hydroplaning, and for braking effect.

Aircraft tires also include fusible plugs (which are assembled on the inside of the wheels), designed to melt at a certain temperature. Tires often overheat if maximum braking is applied during an aborted takeoff or an emergency landing. The fuses provide a safer failure mode that prevents tire explosions by deflating in a controlled manner, thus minimizing damage to aircraft and objects in the surrounding environment.

 

• 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).

Brake force for landing

 An electrical signal is sent from the flight deck to hydraulic actuators near the main landing gear. Here, hydraulic fluid at 3,000 pound per square inch is used to force the brake unit against the wheel, thus slowing it down.

 In detail:

The 787 braking system

Stopping a 200-tonne aircraft landing at 180 mph requires a lot of braking force. To do this, the 787 has one brake unit on each of the eight wheels on the main gear assembly. On other aircraft types, 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 3,000 pound per square inch is used to force the brake unit against the wheel, thus slowing it down.

This system works fine, but the pipes and actuators that form this part of the hydraulic system come at a considerable weight cost. Extra weight means more fuel burn, which in turn increases costs and carbon emissions. What if the brakes could be powered a different way?

That’s the case on the 787 Dreamliner. Designers did away with the use of the hydraulic system and all its associated architecture and instead used electricity to power the brakes. 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.

By changing to electric brakes, a 787-8 saves 141 pounds per aircraft and a 787-9 saves 245 pounds. The brakes are also known as “plug and play” because electrical wiring replaces the traditional hydraulics and it’s much easier and quicker to change the brake units when needed. Smart features also allow engineers to monitor the brake performance more closely, giving a real-time measurement of wear on the carbon disks.

Electric brakes

The brake system on the 787 Dreamliner is controlled by the pilots pressing the tops of the rudder pedals under their feet, demanding the rate of braking which they require. This 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.

The brake disks themselves are made up of two parts. Firstly, there are the rotors. These are connected to the wheel by drive tabs (in the video below they are the black rectangles on the rotor disks). As these drive tabs are in contact with the inside of the wheel, they spin at the same speed. Depending on the brake manufacturer, there are either four or five of these rotors on each brake assembly.

The second part of the disks are the stators. These sit around each rotor and are fixed in place and thus don’t move. As the wheel turns, the rotors spin round inside the stators.

When the brakes are applied, the four EBAs apply pressure to the first stator. This in turn squeezes the stationary stators up against the spinning rotors and it’s this friction which slows the wheel down. https://www.youtube.com/watch?v=n0nXiQPwHE8

Anti-skid protection

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. All this is done in a fraction of a second.

Autobrake

Pressing on the brakes is pretty straight forward when taxiing in a straight line at low speed. However, when we’re landing in strong winds, it can be a little tricky. We need to use our feet on the rudder pedals to line the nose of the aircraft up with the runway centerline at the last moment. Then, whilst holding that position, slide our feet up to press the toe brakes. Really not very easy when moving at 160 mph.

To help us get the braking underway as soon as we touch down, we have the autobrake system.This provides automatic braking at a preselected rate as soon as the aircraft senses that it is on the ground. It also provides full braking pressure in the case of a rejected takeoff if the speed is above 85 knots (98 mph).

Brake temperature indication

With friction comes heat. As a result, each brake unit displays its temperature on the wheel synoptic page in the flight deck. Here, numerical values relating to brake temperature are shown next to each wheel. A value of 0-4.9 is in the normal range. When a temperature becomes 5.0 or above, an advisory message is displayed to the pilots.

Should the brakes become too hot, there’s a chance that the heat transferred to the wheels could cause the tires to explode. To stop this from happening, when a certain temperature is reached, fuse plugs in the tires melt. This allows the air to be released safely and slowly deflate the tires.

Parking brake

Every so often we need to engage the brakes and keep them on. This is particularly useful on long taxis to the runway and obviously when parked at the gate. The park brake is set by fully pressing down both toe brakes and pulling the parking brake lever up. With this set, we can then release the pressure from the pedals. To release, we just press the brake pedals again.

A helping hand

In addition to the brakes, there are two other systems which help slow the aircraft down on landing. The spoilers and the reverse thrust.

Spoilers

Have you noticed the large panels on the top of the wings raise up on touch down? These are the called the spoilers as they literally spoil the airflow over the wing. This dumps any remaining lift the wings are generating, allowing the wheels to take all the weight and achieve maximum efficiency from the brakes.

Reverse thrust

The final part of the braking process comes from reverse thrust. Just after we have touched down, we pull two levers on top of the thrust levers to engage the reverse thrust, a sort of “reverse gear” for jet engines.

This causes blockers inside the engine to deploy and a door in the side of the engine to slide backward. The air which normally leaves the engine out the back is deflected forward by the blockers and out through the door.

There are two stages of reverse thrust — idle reverse and max reverse. Idle reverse is used on most landings and max reverse is used when the landing performance requires it, normally when the aircraft is landing at hot or high elevation airfields.

This forward directed airflow helps slow the aircraft down but is most efficient at high speeds. If using max reverse, we drop this down to idle reverse at 60 knots (70 mph) and then back to normal thrust as we vacate the runway at around 20 knots (25 mph).

Takeoff and landing performance

For every takeoff and landing which we carry out, we run a performance calculation to ensure that it is safe to do so. A large part of this is based on the braking effectiveness.

On takeoff, we have to calculate the point at which it is no longer safe to stop. This speed, V1, marks the point after which we must continue to get airborne, no matter what the problem is.

The calculation of this speed is based mainly on the ability of the aircraft to stop. If the runway is slippery or a brake unit is inoperative, it will take a greater distance to stop. As a result, the V1 speed will be much slower than in normal dry conditions. This means that we will reach that speed sooner and there will be more runway remaining on which to stop.

The performance on landing isn’t normally as restrictive. The aircraft is a lot lighter having used most of its fuel in flight and we are touching down at the start of the runway. This gives the brakes much more distance to bring the lighter weight aircraft to a safe stop.

6. A. With necessary assumptions, calculate the force and power required to push / pull an aircraft by a towing vehicle. 

  Towing vehicles

For movement on the ground the aircraft uses it own engine power, which is called taxing. ... A pushback truck lifts the front weel of the aircraft, their role in most airports is to move the aircraft away from the parking spot on to the taxiways, which is called towing.Those trucks are called towing vehicles.

  The Towing vehicle  experience two types of forces 

• Rolling resistance force
• Aerodynamic drag force

Thus in aircrafts Runways there are no slope roads so hill climbing force and acceleration forces are no need.

    

To calculate the force and power required to push / pull an aircraft by a towing vehicle. 

  let us assume few parameters for towing vehicle and aircraft respectively.

• Rolling resistance coefficient of truck Urr1=0.006
• Rolling resistance coefficient of aircraft Urr2=0.001
• Mass of the truck m1=40000kgs
• Mass of the aircraft m2=80000 kgs
• Gravitational constant g=9.8m/s^2.
• Air density `rho`=1.225 kg/m^3.
• Drag coefficient of truck Cd1=0.8 (refer above table)
• Drag coefficient of aircraft Cd2=0.05
• Frontal area of truck A1=5 m.^2
• Frontal area of aircraft A2=20 m^2
• Velocity of truck=velocity of aircraft v=3 m/s

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

     Aim: To develop the model for the calculated force and power using simulink

    Parameters or blocks:

• Constant 
• Add
• Product
• Display

  Explanation:

• Open the MATLAB simulink model 
• In the simulink library select the required blocks
• Connect the blocks as per the above equations of force and power required to push/pull the aircraft by the towing vehicle.
• First total rolling resistance force is arranged .
• second Total Aerodynamic drag force is connected.
• Both rolling resistance and aerodynamic drag forces are added .
• Thus total force is calculated.
• To that tatal force velocity of towing vehicle is multiplied to get the required power.

   This is model for calculated force and power of the towing vehicle.

 Results: Run the model of calculated force and power of the towing vehicle .

        Thus the required force and power are calculated using simulink .

• Total force = 3145 N
• Total power = 9.4 kW

 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.  

  A.

AIM: To Design an electric powertrain with type of motor, it’s power rating, and energy requirement to fulfill aircraft towing application in Simulink.

Parameters :

• Battery
• DC motor
• Gear box 
• wheel and axle
• mass 
• Ideal torque sensor
• PS-simulink converter 
• Display
• Solver configuration 
• electrical and rotational references

Explanation :

     To fulfill the towing application main element is Torque , so if the motor of towing vehicle produce required amount of torque to push/pull the air craft than and only it can fulfill towing application .

   To prove that let us assume the above values power and force of the towing vehicle to push/pull of aircraft

• force=3145 N
• power=9.4 kW

  W.K.T torque T=F*r/G

        radius of the tyre=0.67 m

       gear ratio =10

               T= 3145*0.67/10=210 Nm

   thus its required 210Nm torque to fulfill the towing application. 

   Here is the model of electric powertrain 

   In this DC motor is used ,you can use induction motor too but for simple opeartion DC motor is best.

   Ideal torque sensor is used to know the torque produced by the motor.Display is coonected to view value of torque.

  Change the Battery voltage to 1000v as shown in the fiqure.  

 To the towing vehicle additional gear box is required  in order to get the highest torque.

   W.K.T Highest torque is obtained at loest speed,so change the gear ratio to 1500

After all changing parameters , run the model

  Results:

   Run the model , thus 251.5 Nm torque is produced by the motor so the elctric motor can fulfill towing application with highest value of voltage (v=1000v) and highest gear ratio (G=1500).

    Energy= power * time

              =9.4 *60*60

              =33840 J

             = 33.84 kJ

Thus 10kW(~9.4kW) power rating and 33.84kJ energy requirement is must for the electric motor to fulfill towing application.

 Duty cycle calculation

     DC motor

•  Rated power =10kw
• efficiency =90%

The motor output power is the input power of the tugs tractor so to obtain maximum speed, the duty cycle needed is calculated as 

duty cycle=output power /input power

  motor input power =rated motor power/ motor efficiency

                               =10/0.9

                               =11.2 

 power requred to air craft is 9.4 kW

duty cycle=9.4/11.2=0.839

  Thus the duty cycle range to control the aircraft speed from zero to highest is  0 to 83% .

Assumed parameters in tabular form

Block diagram of power train

A battery electric vehicle (BEV) is a vehicle that is powered entirely on electric energy, typically
a large electric motor and a large battery pack. Based on the type of transmission; the use of a
clutch, gearbox, differential, and fixed gearing; and the number of battery packs and motors there
are many variations on the BEV design. However, a basic BEV system is shown in Figure 1.

                B. Also, Design the parameters in excel sheet. 

            Create a excel sheet for power  and  force calculation .

 CONCLUSIOB:

Part A:

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

2. Difference between ground speed and air speed is explained.

3. cleared that  it not recommended to use aircraft engine power to move it on the ground at Airport. 

4.  An aircraft is pushed to runway when its ready to take off is illustrated.

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

Part B:

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 the calculated force and power using Simulink are done.

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. 

(Hint :DC7 Block)

    B. Also, Design the parameters in excel sheet are done successively.