Project-1: Powertrain for aircraft in runways

Aircraft:

Any vehicle that is manufactured and made to fly in the air is called an aircraft.

One is lighter than air aircrafts, known as aerostats, and the other is heavier than air aircrafts, called aerodynes.

Two classifications of Aircrafts:

1.Aerostats(Lighter than air aircrafts)

2.Aerodynes(Heavier than air aircrafts)

Aerostats (Lighter Than Air):

Aerostats or lighter than air aircrafts are very more lightweight in weight. These types of light aircraft generally use buoyancy like ships, which help them float in the air.

Low-density gas such as hydrogen, helium, or hot air balloons is used to fill in the aircraft. This low-density gas is lighter than air, and hence the name. The most common types of aerostats known to us are hot air balloons and sky lanterns.

Aerodynes (Heavier Than Air):

This is heavier than air or aerodynes, as we understand, is much higher in weight and size.

They push the gas or air downwards; which reaction helps to make aircraft upwards. Since these are dynamic through movements in the air, they are called aerodynes.

Classifications:

1.Fixed wing -which is a aeroplanes where their wings are fixed and the mechanism is to adjusted by the little movement in wings

2. Rotor shaft type which is the helicopter where the rotor rotates in the top side for the movements

The aircraft has:

• Basic Empty Weight (BEW) is the weight of the aircraft "as built" and includes the weight of the structure, power plant, furnishings, installations, systems and other equipment that are considered an integral part of an aircraft before additional operator items are added for operation.
• Dry Operating Wieght (DOW) BEW + Weight of Crew (Pilot + Cabin including their bags) + Pantry
• Operating Weight (OW) DOW + Takeoff fuel (i.e. Ramp Fuel - Taxi fuel)
• Maximum Zero Fuel Weight (MZFW) DOW + Payload (anything put on the aircraft that generates revenue to the company, e.g. passenger, baggage, cargo, mail and fret)
• Maximum Taxi Weight (MTW) MZFW + Ramp fuel
• Maximum Takeoff Weight (MTOW) MZFW + Takeoff fuel, or MTW - Taxi fuel
• Maximum Landing Weight (MLW) MTOW - Trip Fuel

These are the different weights of the AIRCRAFT.

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

Ground Speed:

While ground speed is the airplane’s speed relative to the surface of the Earth, airspeed – at least

Air speed:

Air speed is its speed relative to the air it is flying in it.

Ground speed is simply the sum of airspeed and wind speed.

If the aircraft is flying in the same direction as the wind is blowing, the aircraft experiences tailwind, and its ground speed is higher than its airspeed.

On the other hand, if the wind is blowing against the direction the aircraft is traveling in, the aircraft experiences headwind, and its ground speed is lower than its airspeed.

Example

Imagine an aircraft that cruises at an airspeed of 500 miles per hour that has to cover a ground distance of 2,000 miles.

If there is no wind at all, then both the aircraft’s airspeed and ground speed would be the same 500 miles per hour, and the aircraft would reach its destination in four hours.

If there was a 100 miles per hour headwind – wind blowing against the aircraft’s direction of travel – the aircraft would still be traveling at an airspeed of 500 miles per hour. However, its ground speed would be just 400 miles per hour (100 miles per hour slower than its airspeed). And as such, it would take the aircraft five hours to reach its destinations.

Finally, if there was a 100 miles per hour tailwind – wind blowing in the same direction as the aircraft’s travel – the aircraft would still be traveling at an airspeed of 500 miles per hour, but its ground speed would be 100 miles faster. And, at 600 miles an hour, the aircraft would reach its destination in just three hours and twenty minutes.

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

By using jet engines as an aircraft’s primary thrust for taxiing, airlines are expending huge amounts of jet fuel while still on the ground, which could be much better used for flying. With the Cost of Fuel being their single biggest expense, many airlines plan to adopt electric taxiing to save fuel and reduce environmental impacts.

Taxiing is the movement of an aircraft on the ground, under its own power, in contrast to towing 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).

An airplane uses taxiways to taxi from one place on an airport to another; for example, when moving from a hangar to the runway. The term "taxiing" is not used for the accelerating run along a runway prior to takeoff, or the decelerating run immediately after landing, which are called the takeoff roll and landing rollout, respectively.

Why it is not using its own engine to move in grounds?

Actually It does. But while taxiing, the airplane move in a reverse condition as the engine might generate the reverse thrust in it.

Aircraft are unable to do this as they don’t have a reverse gear. In order to get round this problem, we use the assistance of a pushback tug.

And the security reasons also. The engines are turbo engine which will generate more amount of energy for its movement.The aircraft will move in the grounds at the speed of 16 to 20 kmph.So the external vehicle is used instead of own engine.

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

START SMALL – TUGS FOR MOVING LIGHT AIRCRAFT

Look down on yourself. Shoulders… arms… ah, and there it is! The simplest way to move a light-sport aircraft or another small plane: your bare hands. Once in motion, these airplanes can be moved around by hand since they are on wheels. Whoever pushed a car once knows that the force it takes to set such a vehicle in motion is nothing compared to its actual weight. Some propeller planes can even be pulled by their propeller – yeah, it’s strong enough. It holds the plane’s weight in the air, after all.

THE COMMON TOW BAR – A HELPING HAND

Admittedly, pulling a plane by hand can be a cumbersome procedure. An easy and cheap helper is a simple tow bar. These devices are often made of aluminum and therefore very light. You attach them to either the nose wheel or the tail wheel of your aircraft and obtain a practical handle you can steer the plane with it. Its small size and weight even allows to take such a tow bar along on the flight.

TUG #3: ENGINE POWERED CONVENTIONAL TOW BAR TRACTORS AND TUGS

So you have a tow bar, but somehow you still have to do everything with your own manpower. Where’s the fun, right? That’s what people must have thought when they decided that tow bars should have an engine. Ever since tugs and massive tractors with tow bars help pulling aircrafts from A to B. An engine powered vehicle is quite useful, especially when it comes to heavy aircrafts that weigh hundreds of tons.

What used to be a blessing in the flourishing aviation business of the last century has slowly become a relict of an outdated technology, though. Not only does every airplane type require a specific tow bar, taking spontaneous maneuvers off the table. But the mechanics of a tow bar tug are actually pretty much outdated. The cockpit needs to be occupied for every operation and the gross motor skills of tow bar tugs deny clever parking and small turning circles. In aviation time is money, so abandoning your old tow bar tractors can actually save you cash. But for what alternative?

TUG #4: ENGINE POWERED TOWBARLESS TUGS

Given these obvious downsides of tow bar tugs it was quite evident that there had to be another solution. That’s why in the 1980s the first towbarless tug was introduced in France. Since then it has taken the world by storm, cutting out conventional tow bar tractors from many scopes of ground support. The wheel of the aircraft is hydraulically picked up, placed and fixated atop of the tug. Therefore one aircraft tug fits a wide range of aircrafts and does no longer rely on an adapter such as a tow bar.

No doubt: A towbarless tug has plenty of advantages over a tow bar tractor. But it is still not the measure of all things, particularly because of two major minuses: the technology and the handling. For one thing using fossil fuels on your GSE is simply a waste of resources and pollutes your working environment. For another thing operating a generic towbarless tug requires multiple people at a time, one of them sitting in the tug steering it. This doesn’t only raise your personnel costs. It comes with a risk for both your employees and the aircrafts and GSE involved, since human errors are more likely, especially with not automated tugs. The consequences could be observed for example in early 2016 when Iron Maiden’s 747-400 was damaged and two workers were injured in a tug collision.

What is the logical consequence to avoid these problems? You guess it…

TUG #5: ELECTRIC TOWBARLESS REMOTE-CONTROLLED AIRCRAFT TUGS – OR SIMPLY MOTOTOK

A 2008 study by the Institute for Automotive Engineering (ika) at the RWTH University of Aachen, Germany came to the conclusion that it’s only reasonable to replace diesel tractors with electric tugs – both economically and ecologically. The study assumed that hybrid systems will be the next step. In the same year Mototok decided to jump ahead of its time and released its first all-electric remote-controlled aircraft tug, eliminating all problems mentioned earlier.

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

Take OFF Power:

Takeoff is the phase of flight in which an aircraft goes through a transition from moving along the ground (taxiing) to flying in the air, usually starting on a runway. Usually the engines are run at full power during takeoff. Following the taxi motion, the aircraft stops at the starting line of the runway. Before takeoff, the engines, particularly piston engines, are routinely run up at high power to check for engine-related problems. This makes a consid- erable noise. When the pilot releases the brakes, the aircraft starts accelerating rapidly until the necessary speed for take-off is achieved.

The takeoff speed required varies with air den- sity, aircraft weight, and aircraft configuration (flap and/or slat position, as applicable). Air density is affected by factors such as field ele- vation and air temperature.

Operations with transport category aircraft employ the concept of the takeoff V-Speeds, V1 and V2. These speeds are determined not only by the above factors affecting takeoff perform- ance, but also by the length and slope of the runway. Below V1, in case of critical failures, the takeoff should be aborted; above V1 the pilot continues the takeoff and returns for land- ing. After the co-pilot calls V1, Then, V2 (the safe takeoff speed) is called. This speed must be maintained after an engine failure to meet per- formance targets for rate of climb and angle of climb.

The speeds needed for takeoff are relative to the motion of the air (indicated airspeed). A head wind will reduce the ground speed needed for takeoff, as there is a greater flow of air over the wings. This is why the aircrafts always take off against the wind. Side wind is not preferred as it would disturb the stability of the aircraft. Typical takeoff air speeds for jetliners are in the 130–155 knot range (150–180 mph, 240–285 km/h). For a given aircraft, the takeoff speed is usually directly proportional to the aircraft weight; the heavier the weight, the greater the speed needed. Some aircraft have difficulty generating enough lift at the low speeds encountered during takeoff. These are therefore fitted with high-lift devices, often including slats and usually flaps, which increase the camber of the wing, making it more effective at low speed, thus creating more lift. These have to be deployed from the wing before performing any maneuver.

At the beginning of the climb phase, the wheels are retracted into the aircraft and the undercarriage doors are closed. This operation is audible by the passengers as a noise coming from below the floor.

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.

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.

Tyre Pressure:

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).

A carefully thought out pressure maintenance routine will increase the life of the tyre and will reduce the number of wheel changes required.

As all tires can allow a small pressure decrease during normal operations (due to the intense nature of their service life) airplane operators should check tire pressure every 24 hours.

Because putting the right pressure in the tires will always take pressure off the airplane operation.

Rolling Resistance:

When a loaded wheel and tyre is compelled to roll in a given direction, the tyre carcass at the ground interface will be deflected due to a combination of the vertical load and the forward rolling effect on the tyre carcass

The vertical load tends to flatten the tyre's circular profile at ground level, whereas the forward rolling movement of the wheel will compress and spread the leading contact edge and wall in the region of the tread.

At the same time, the trailing edge will tend to reduce its contact pressure and expand as it is progressively freed from the ground reaction. The consequences of the continuous distortion and recovery of the tyre carcass at ground level means that energy is being used in rolling the tyre over the ground and it is not all returned as strain energy as the tyre takes up its original shape.

Braking Power:

Aircraft brakes stop a moving aircraft by converting its kinetic energy to heat energy by means of friction between rotating and stationary discs located in brake assemblies in the wheels.

Aircraft brakes work in conjunction with other brake mechanisms such as thrust reversers, air brakes and spoilers

Aircraft brakes work in conjunction with other brake mechanisms such as thrust reversers, air brakes and spoilers. Thrust reversers are surfaces that are deployed into the path of the jet blast from the engines to redirect propulsive thrust in a direction that opposes the motion of the aircraft. Air brakes and spoilers are flight control surfaces that create additional aerodynamic drag when deployed into the path of air flowing around the aircraft.

Upon receiving a command signal to brake — from the pilot depressing a foot pedal or from the autobrake system — actuators in the brake move a piston to squeeze the discs together, generating a frictional force that slows the rotation of the wheel. The friction between the discs generates heat as the aircraft’s kinetic energy is converted to heat energy. In this function, the brakes act as a heat sink, absorbing tremendous amounts of heat as the aircraft sheds kinetic energy. During RTO stops, the temperature of carbon disc brakes can exceed 1,800° C.

Lets take an example of embrare 90

Weight of the aircraft is 45000kg

Rolling resistance formula is given as

F_r = c m_r a_g (1)

where

F_r = rolling resistance (N, lb_f)

c = rolling resistance coefficient

m_r = rolling mass (kg, lb_m)

a_g = acceleration of gravity (9.81 m/s²)

F_r = 0.02 (45000 kg) (9.81 m/s²)

= 8829 N

Rolling Resistance force is 8829N

Pull over Force is calculated as

In Order to Pull the Aircraft, the vehicle mass should be given as

The friction force for the puller can be calculated to

F_f = μ W

= μ m_f a_g (2)

where

F_f = frictional force (N, lb)

μ = friction coefficient

W = weight (N, lb_f)

m_f = friction mass (kg)

m_f = (8829 N) / (0.9 (9.81 m/s²))

= 1000 kg

Airdrag force is given as

Air drag force is given as 481Nm

So the Total Power of the motor required is 79.139KW for the maximum speed of 30kmph.

Lets take the motor of 80KW

Towing distance is 500m

Time taken to reach the destination is 1minute

Energy required=80*(1/60)=1.33KWh

Block Diagram :

Simulation Model:

Scope

After 2 secs, The IGBT 1 and 3 are open and the pulse signal is 1.

The Voltage magnitude of armature is 360V.

The current obtained is 220A

The total KW is given as 79.4KW

The data of the vehicle:

Kerb weight	1000
Pay Weight	45000
Co-efficient of Rolling Resistance	0.02
Force on Rolling Resistance	9016

Air density	1.25
Width	5.5
Height	10.6
Front Area	58.3
Drag Coefficient	0.19
Speed	30
Speed(m/s)	8.3
Air Drag Force	481

Total Power for Air Drag and RR

79.13977141KW

The Voltage of the motor:360V

Current:220A

Power=79.4KW

Conclusion:

Battery Voltage given as 500V

The voltage for the motor is 380V

The duty ratio is 76%

the Armature voltage is 360V

The current across the armature is 220 A

Power =360*220=79.4KW

Block Diagram:

Calculation Spreadsheet is attached.