(17) Module 2 : Final Project-1 ---> Powertrain for aircraft in runways

Project-1: Powertrain for aircraft in runways

Aim: Familiarization with "Powertrain Of Aircraft In Runways".

Objectives:

1. Search and list out the total weight of various types of aircraft.
2. Is there any difference between ground speed and airspeed?
3. Why is it not recommended to use aircraft engine power to move it on the ground at the Airport?
4. How an aircraft is pushed to the runway when it's ready to take off?
5. Learn about take-off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.
6. With necessary assumptions, calculate the force and power required to push/pull an aircraft by a towing vehicle.
7. Design an electric powertrain with a type of motor, its power rating, and energy requirement to fulfill aircraft towing application. 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.

Answers:

Objective No. (1):

Aircraft Authorized Gross Weight Limits (also referred to as certified weight limits) are laid down in the (AFM) or Associated Certificate of Airworthiness. The Authorized weight limits that can legally be used by an operator or airline are those listed in AFM and the weight and balance manual. The Authorized weight limits are chosen by the customer/ airline and they are referred to as “purchased weight”. The operator may purchase certified weight below the max. design weight because many of the operating fees are based on the aircraft AFM maximum allowable weight values. An aircraft purchase is typically a function of the certified weight purchased.

Maximum weights established for each aircraft, by design & certification must not be exceeded during aircraft operation (ramp or taxying, take-off, en-route flight, approach & landing) & during aircraft loading (zero fuel conditions, center of gravity positions, weight distribution) weights could be restricted on some type of aircraft depending on the aircraft handling requirements, e.g. Aerobatic Flight Aircraft, where certain Aerobatic Manoeuvres can only be executed with a limited gross weight.

Also, the authorized maximum weight limits may be less as limited by the center of gravity, fuel density, and fuel loading limits. The different terms represent different weights or masses. For each flight, the weights are taken into account for several reasons like design, authorization, suitable condition, etc. A brief description of these is below:

Manufacturer's Empty Weight(MEW):
Also called Manufacturer's Weight Empty (MWE) or Licensed Empty Weight. It 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. This excludes any baggage, passengers, or usable fuel.

Zero-fuel weight(ZFW):

This is the total weight of the airplane and all its contents (including unusable fuel), but excluding the total weight of the usable fuel on board.

As a flight progresses and fuel is consumed, the total weight of the airplane reduces, but the ZFW remains constant.

Maximum zero fuel weight (MZFW) is the maximum weight allowed before usable fuel and other specified usable agents (engine injection fluid, and other consumable propulsion agents) are loaded.

Operating empty weight(OEW): (Roughly equivalent to basic empty weight on light aircraft)

It is the basic weight of an aircraft including the crew, all fluids necessary for operation such as engine oil, engine coolant, water, unusable fuel, and all operator items and equipment required for flight but excluding usable fuel and the payload.

Now, it is important to mention that the carrying capacity of an aircraft is known as the Payload. It includes cargo, people, extra fuel. In the case of a commercial airliner, it may refer only to revenue-generating cargo or paying passengers.

Maximum takeoff weight(MTOW):

This is the maximum weight at which the pilot of the aircraft is allowed to attempt to take off.

Regulated takeoff weight(RTOW):

Depending on different factors (e.g. flap setting, altitude, air temperature, length of runway), RTOW or maximum permissible takeoff weight varies for each takeoff. It can never be higher than MTOW.

The following image depicts takeoff weight components for a better idea.

Maximum landing weight(MLW):

This maximum weight at which an aircraft is permitted to land. The maximum certificated design weight at which the aircraft meets the appropriate landing certification requirements. It generally depends on the landing gear strength or the landing impact loads on certain parts of the wing structure. The MLW must not exceed the MTOW.

The maximum landing weight is typically designed for 10 feet per second (600 feet per minute) sink rate at touch down with no structural damage.

Maximum ramp weight(MRW):

Also called maximum taxi weight (MTW). It is the maximum weight authorized for maneuvering (taxiing or towing) an aircraft on the ground.

Aircraft gross weight(AGW):

It is the total aircraft weight at any moment during the flight or ground operation. This decreases during the flight due to fuel and oil consumption.

To have a practical idea a complete listing of the "Aircraft's maximum takeoff weight(MTOW)" is given below with all the needed details:

Airplanes:

MTOW = Maximum take-off weight, MLW = Maximum landing weight, TOR = Take-off run (SL, ISA+15°, MTOW), LR = Landing run (SL, ISA+15°, MLW)

Type	MTOW [kg]	MLW [tonnes]	TOR [m]	LR [m]	ICAO category	FAA category
Antonov An-225	640,000	591.7	3500		Heavy	Super
Scaled Composites Model 351 Stratolaunch	589,670		3660		Heavy	Super
Airbus A380-800[1][2][3]	575,000	394	3100	1930	Super	Super
Boeing 747-8F	447,700	346.091	3100	1800	Heavy	Heavy
Boeing 747-8	443,613	306.175	3100		Heavy	Heavy
Boeing 747-400ER	412,770	295.742	3090		Heavy	Heavy
Antonov An-124-100M	405,060	330	2520	900	Heavy	Heavy
Boeing 747-400	396,900	295.742	3018	2179	Heavy	Heavy
Lockheed C-5 Galaxy[4][5][6]	381,000	288.417	2530	1494	Heavy	Heavy
Boeing 747-200[7]	377,840	285.700	3338	2109	Heavy	Heavy
Boeing 747-300[7]	377,840	260.320	3222	1905	Heavy	Heavy
Airbus A340-500[8]	371,950	240	3050	2010	Heavy	Heavy
Airbus A340-600[8]	367,400	256	3100	2100	Heavy	Heavy
Boeing 777F	347,800	260.816	2830		Heavy	Heavy
Airbus A330-900	352,000	251.5	3100		Heavy	Heavy
Boeing 777-300ER	351,800	251.29	3100		Heavy	Heavy
Boeing 777-200LR	347,450	223.168	3000		Heavy	Heavy
Boeing 747-100[7]	340,200	265.300			Heavy	Heavy
Airbus A350-1000	308,000	233.5			Heavy	Heavy
Boeing 777-300	299,370	237.683	3380		Heavy	Heavy
Boeing 777-200ER	297,550	213.00	3380	1550	Heavy	Heavy
Airbus A340-300[8][9]	276,700	190	3000	1926	Heavy	Heavy
McDonnell Douglas MD-11	273,300	185	2990	1890	Heavy	Heavy
Airbus A350-900	270,000	175	2670	1860	Heavy	Heavy
Ilyushin Il-96M	270,000	195.04	3115	2118	Heavy	Heavy
McDonnell Douglas DC-10	256,280	183	2990	1890	Heavy	Heavy
Boeing 787-9[10]	254,000	192.777	2900		Heavy	Heavy
Boeing 787-10[10]	254,000	201.849			Heavy	Heavy
Airbus A340-200[8][11]	253,500	181	2990		Heavy	Heavy
Ilyushin IL-96-300	250,000	175	2600	1980	Heavy	Heavy
Airbus A330-300[12][13]	242,000	185	2500	1750	Heavy	Heavy
Airbus A330-200[12][13]	242,000	180	2220	1750	Heavy	Heavy
Lockheed L-1011-500	231,300	166.92	2636		Heavy	Heavy
Boeing 787-8[10]	228,000	172.365	3300	1695	Heavy	Heavy
Lockheed L-1011-200	211,400				Heavy	Heavy
Ilyushin IL-86	208,000	175			Heavy	Heavy
Boeing 767-400ER	204,000	158.758	3414		Heavy	Heavy
Airbus A300-600R[14]	192,000	140	2385	1555	Heavy	Heavy
Boeing 767-300ER	187,000	136.08	2713	1676	Heavy	Heavy
Concorde	185,000	111.1	3440	2220	Heavy	Heavy
Airbus A300-600[14]	163,000	138	2324	1536	Heavy	Heavy
Boeing 767-300	159,000	136.078	2713	1676	Heavy	Heavy
Airbus A310-300[14]	157,000	124	2290	1490	Heavy	Heavy
Vickers VC10	152,000	151.9			Heavy	Heavy
Boeing 707-320B[15]	151,000	97.5			Heavy	Heavy
Boeing 707-320C[15]	151,000	112.1			Heavy	Heavy
Douglas DC-8-61	147,000				Heavy	Heavy
Airbus A310-200[14]	142,000	123	1860	1480	Heavy	Heavy
Airbus A400M	141,000	122	980	770	Heavy	Heavy
Douglas DC-8-32	140,000				Heavy	Heavy
Douglas DC-8-51	125,000				Medium	Large
Boeing 757-300	124,000	101.6	2550	1750	Medium	Large
Boeing 707-120B[15]	117,000	86.3			Medium	Large
Boeing 757-200	116,000	89.9	2347	1555	Medium	Large
Boeing 720B[16]	106,000	79.5			Medium	Large
Boeing 720[16]	104,000	79.5			Medium	Large
Tupolev Tu-154M	104,000	80			Medium	Large
Tupolev Tu-204SM	104,000	87.5	2250		Medium	Large
Convair 880	87,500				Medium	Large
Boeing 737-900	85,000	66.36	2500	1704	Medium	Large
Boeing 737-900ER	85,000	71.35	2804	1829	Medium	Large
Boeing 727-200 Advanced[17]	84,000	70.1			Medium	Large
Airbus A321-100[18]	83,000	77.8	2200	1540	Medium	Large
Boeing 737-800	79,000	65.32	2308	1634	Medium	Large
Boeing 727-200[17]	78,000	68.1			Medium	Large
McDonnell-Douglas MD-83	73,000	63.28			Medium	Large
Boeing 727-100[17]	72,500	62.4			Medium	Large
Boeing 727-100C[17]	72,500	62.4			Medium	Large
McDonnell-Douglas MD-90-30	71,000	64.41	2165	1520	Medium	Large
de Havilland Comet 4	70,700				Medium	Large
Boeing 737-700	70,000	58.06	1921	1415	Medium	Large
Airbus A320-100[18]	68,000	66	1955	1490	Medium	Large
Boeing 737-400	68,000	54.9	2540	1540	Medium	Large
de Havilland Comet 3	68,000				Medium	Large
Boeing 377	67,000				Medium	Large
Boeing 737-600	66,000	54.66	1796	1340	Medium	Large
Airbus A220-300	65,000	57.61	1890	1494	Medium	Large
Hawker Siddeley Trident 2E	65,000				Medium	Large
Airbus A319[18]	64,000	62.5	1850	1470	Medium	Large
Boeing 737-300	63,000	51.7	1939	1396	Medium	Large
Boeing 737-500	60,000	49.9	1832	1360	Medium	Large
Airbus A220-100	59,000	50.80	1463	1356	Medium	Large
Airbus A318[18]	59,000	57.5	1375	1340	Medium	Large
Boeing 717-200HGW	55,000	47.174	1950		Medium	Large
Douglas DC-7	55,000				Medium	Large
de Havilland Comet 2	54,000				Medium	Large
Boeing 717-200BGW	50,000	46.265	1950		Medium	Large
de Havilland Comet 1	50,000				Medium	Large
Douglas DC-6A	48,600				Medium	Large
Douglas DC-6B	48,500				Medium	Large
Embraer 190[19]	48,000	43	2056	1323	Medium	Large
Caravelle III	46,000				Medium	Large
Fokker 100	46,000	39.95	1621	1350	Medium	Large
Douglas DC-6	44,000				Medium	Large
Avro RJ-85	42,000	36.74			Medium	Large
Handley Page Hermes	39,000				Medium	Large
Embraer 175[20]	37,500	32.8	2244	1304	Medium	Large
Bombardier CRJ900[21]	36,500	33.345	1778	1596	Medium	Large
Embraer 170[22]	36,000	32.8	1644	1274	Medium	Large
Bombardier CRJ700	33,000	30.39	1564	1478	Medium	Large
Douglas DC-4	33,000				Medium	Large
Vickers Viscount 800	30,400				Medium	Large
Bombardier Q400	28,000	28.01	1219	1295	Medium	Large
Bombardier CRJ200	23,000	21.319	1918	1479	Medium	Large
ATR 72-600	22,800	22.35	1333	914	Medium	Large
Saab 2000	22,800	21.5	1300		Medium	Large
Embraer ERJ 145	22,000	19.3	2270	1380	Medium	Large
ATR 42-500	18,600	18.3	1165	1126	Medium	Small
Saab 340	13,150	12.930	1300	1030	Medium	Small
Embraer 120 Brasilia	11,500	11.25	1560	1380	Medium	Small
BAe Jetstream 41	10,890	10.570	1493	826	Medium	Small
Learjet 75[23]	9,752	8.709	1353	811	Medium	Small
Pilatus PC-24[24]	8,300	7.665	893	724	Medium	Small
Embraer Phenom 300[25]	8,150	7.65	956	677	Medium	Small
Beechcraft 1900D	7,765	7.605	1036	853	Medium	Small
Cessna Citation CJ4[26]	7,761	7.103	1039	896	Medium	Small
de Havilland Hercules	7,000				Medium	Small
Embraer Phenom 100	4,800	4.43	975	741	Light	Small

Objective No. (2):

Air-speed & Ground-speed of an Aircraft:

As mentioned above, true airspeed is simply the speed at which an aircraft is moving relative to the air it is flying in. As such, it’s also the speed at which the air is flowing around the aircraft’s wings.`Ground speed, on the other hand, is the aircraft’s speed relative to the ground. One thing that should be noted here is that it is horizontal rather than vertical speed – an aircraft climbing completely vertically would have a ground speed of zero. In other words, while airspeed is what determines whether there is enough airflow around an aircraft to make it fly, ground speed is what determines how fast an aircraft will get to its destination.

• The aircraft usually operates on land as well as in air and so we need to study their speed differences in-ground and in air
• The ground speed and the airspeed usually change based on the wind component.
• If we consider that there is no wind component then, ground speed = airspeed
• If the wind is blowing in the tail direction of the aircraft then, (airspeed > ground speed) so, airspeed = ground speed + wind component.
• If the wind is blowing in the head direction of the aircraft then, (airspeed < ground speed)so, airspeed = ground speed – wind component.
• Also, gravity plays a major role in increasing the aircraft's speed while it is descending.

• Here wind speed is the vector difference between ground and airspeed. On a particular day, the wind speed may be zero and it is equal to the ground speed.

• If the measured airspeed is greater than the observed ground speed the wind speed becomes positive.

Objective No. (3):

We are assuming passenger commuter aircraft and large airliners. Aircraft move using their own engine power all the time on the airport apron and taxiways under their own power to go towards runways and after landing taxi to their assigned gate.

The only time they use external assistance is to push back from the gate. It is not recommended to use aircraft engine power to move it on the ground at the airport because there are certain extreme cautions for everything around us are there. Large turbofan aircraft need help to reverse via a pushback tractor. The engines are turned on after the pushback is complete and the aircraft can move forward under Its own power.

To be accurate, some aircraft can reverse using a variable pitch prop or thrust reversing on turbofans but generally reversing is done via pushback tractors. Blasting jet reversers blows debris In the crowded gate area creating foreign object damage hazards for adjacent aircraft, gate equipment, or terminal waiting area glass windows.

Generally, most of the airplane can move in a reverse manner by making use of reverse thrust technology. But in most of the practice, it is not possible because when airplanes start using reverse thrust it will consume a lot of fuels as well as causes a lot of noise and also hazardous for the people working nearby.

Applying thrust (gas) can create a blast behind each engine. People, equipment, and anything else in the way can be injured or damaged from the jet blast. Before we apply power to engines the areas in front of each engine are like other supercritical factors that must be carefully negotiated.

Another for not using reverse thrust is that the jet blast can cause damage to terminal buildings or their equipment; it also can affect the crew and passengers on that aircraft. Since the engine is also close to the ground it will blow off the sand and debris forward and sucks it to the engine and causes damage to it.

The immediate area in front of the jet engine creates an area where people and equipment can be sucked into the engine if anything is too close to the intake.

To avoid extreme cautions, it’s not recommended to use aircraft engine power to move it on the ground at the airport.

Objective No. (4):

Taxiing refers to the movement of an aircraft on the ground, under its own power. The aircraft moves on wheels. An airplane uses taxiways to taxi from one place on an airport to another; for example, when moving from a terminal to the runway.

When the aircraft is ready with all the passengers and luggage the aviation, pushback is an Airport procedure during which an aircraft is pushed backward away from an airport gate by an external power. The aircraft always moves on the ground following the yellow lines, to avoid any collision with the surrounding buildings, vehicles, or other aircraft. The taxiing motion has a speed limit. Before making a turn, the pilot reduces the speed further to prevent tire skids. Just like cars, there is a certain list of priorities during taxiing. The aircraft that are landing or taking off have higher priority. The other aircraft have to wait for these aircraft before they start or continue taxiing. The thrust to propel the aircraft forward comes from its propellers or jet engines. Steering is achieved by turning a nose wheel or tail wheel/rudder; the pilot controlling the direction traveled with their feet. The use of engine thrust near terminals is restricted due to the possibility of jet blast damage. This is why the aircraft is pushed back from the buildings by a vehicle before they can start their own engines for taxiing.

• Pushbacks are carried out by special, low-profile vehicles called pushback tractors or tugs.
• These are heavy weighing low profile vehicles with enormous torque to do the job of pushing/pulling the large aircraft from the terminals to the runway.
• The Tractors are designed with extra weight purposely to offer them enough Traction to push/pull heavy aircraft.

Objective No. (5):

(i) Take off the power:

• 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
• The takeoff speed required varies with air density, aircraft gross weight, and aircraft configuration
• The power from the engine of the aircraft used to achieve the flight is called take-off power
• 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 to prolong engine life, reduce maintenance costs and reduce noise emissions.

(ii) Tyre Design:

The aircraft tyre is usually specially designed as the tyre has to withstand more load and also the higher speed at the same time. The number of tires required for any aircraft increases with the aircraft's weight, as the weight of the aircraft needs to be distributed more evenly. Aircraft's tread patterns are designed to facilitate stability in high crosswind conditions, to channel water away to prevent hydroplaning, and for braking effect. some of the tyre design is listed below.

Bias Ply Tyre:

• The bias ply tyre consists of casing plies running diagonally at approximately right angles to one another.
• The number of plies and the angles at which they are laid dictate strength and load capacity.
• High-performance bias aircraft tyres feature inter-tread reinforcing fabric (ITF). This provides additional high-speed stability, reduces tread distortion under load, protects the casing plies from damage, and can act as wear indicators on retread able tyres.

Tire Terminology

1. Apex strip: A triangular piece of stiff rubber which is fitted onto the bead core to taper the rigid bead into the flexible body plies in the sidewall.
2. Bead heel: Outer edge of the bead.
3. Bead toe: Inner edge of the bead.
4. Breaker: Breakers are fabric plies placed directly on the upper-most ply beneath the tread rubber. They disperse stress throughout the tire. This breaker is utilized in a limited number of Bridgestone aircraft tires.
5. Chafer strip: Reinforces the beads and protects the cord body-plies from damage from rim friction or damage when replacing the rim.
6. Carcass plies: Each nylon ply is held by wire beads across the tire to keep the tensile strength at the proper level, and is folded to the side of the sidewall. Each ply is provided with cushion rubber to reduce the shearing force produced between the cords of the tire when it is deformed. Multiple coated nylon cords are crossed alternately on the bias to make the carcass.
7. Decoration line: A projecting, embossed line molded between the shoulder and sidewall of a tire. Its purpose is for decoration only.
8. Flipper strip: A strip of material that is wrapped around the bead bundle and filler to add support and help taper the assembly into the sidewall.
9. Inner liner: A sheet of special rubber laminated to the inside of the first casing ply of the tubeless tire to ensure retention of pressure when the tire is inflated.
10. Ply turn-ups: The turned-up ends of plies around the bead. Other plies lock the ends into place.
11. Tread reinforcing fabric: Nylon cord plies located in the tread between the tread groove and the outer ply of the carcass which reduce tread squirm and increase stability for high-speed operations.
12. Rim line: This line is provided near the beads to allow inspection of how the tire fits with the rim.
13. Shoulder: The area on the side of the tire between the sidewall and the tread.
14. Sidewall: The side area of the tire is located between the buttress and the beads. Composed of rubber, it protects the carcass from damage.
15. Tread: A layer of rubber on the outer circumference of a tire, its major functions are to protect the casing from cuts, withstand high speed during take-off and landing, provide traction, resist wear, provide durability under a wide range of temperatures, and ensure stability (in particular, the effective discharge of water on wet runways). The tread compound is designed to suit a wide range of operations.
16. Under tread: A rubber layer provided for use in retreading the tire and which provides adhesion of tread to the cord body. Bridgestone makes this rubber layer thick enough to ensure a high number of retreads.
17. Wire beads: Constructed of steel wire encased in rubber, they help to maintain the shape of the tire and keep it securely fixed to the rim. The wire beads are wrapped with fabric.
18. Venting hole: The hole through which gas is vented from inside the carcass plies.

Balance marker

A balance marker, consisting of a red dot, is affixed on the sidewall of the tire immediately above the bead to indicate the lightweight point of the tire.

Radial Tyre

Radial tires are the most modern design of aircraft tyres. It is a design that is similar to that of car tyres. Typically, the radial tyre offers more landings per tread and lighter weight than a bias tyre, though sometimes at the expense of retread lives. Radial aircraft tyres differ from biased aircraft tyres in that the plies all run radially from bead to bead at approximately 90° to the center-line of the tyre. Angled belt plies are laid between the tread and the top casing ply, resulting in a flatter tread and adding strength to the tyre.

Tire Terminology

1. Apex strip: A triangular piece of stiff rubber which is fitted onto the bead core to taper the rigid bead into the flexible body plies in the sidewall.
2. Aramid cord protector: The tire is constructed with an aramid ply insert between the tread and the top belt to prevent damage to the tire belts.
3. Bead heel: Outer edge of the bead.
4. Bead toe: Inner edge of the bead.
5. Belt plies: Angled belt plies that serve to add strength to the tire especially in the tread area.
6. Chafer strip: Protective layer of rubber and fabric which prevents chafing between cord body plies and the wheel.
7. Carcass plies: Layers of rubber-coated fabric plies which have the cords running radially from bead to bead. These provide the tire with strength in the sidewall area.
8. Inner liner: A sheet of low permeable rubber laminated to the inside of the first casing ply of a tubeless tire to insure retention of air when the tire is inflated.
9. Ply turn-ups: The turned-up ends of plies around the bead. Other plies lock the ends into place.
10. Rim line: A-line provided near the beads to allow inspection of how the tire fits with the rim.
11. Sidewall: The side area of the tyre is located between the shoulder and the beads. Composed of rubber, it protects the carcass from damage.
12. Tread: The functions of the radial tread are the same as those defined for the bias tire.
13. Under tread: A rubber layer provided for use in retreading the tire and which provides adhesion of tread to the tire carcass. Bridgestone makes this rubber layer thick enough to ensure a high number of retreads.
14. Wire beads: Two-wire bundles (one for each bead) which help to maintain the shape of the tire and anchor it securely to the rim.
15. Venting hole: The hole through which gas is vented from inside the carcass plies.

Balance marker

A balance marker, consisting of a red dot, is affixed on the sidewall of the tire immediately above the bead to indicate the lightweight point of the tire.

(iii) Rolling Resistance:

The Rolling resistance force is mainly Experienced by the Tyre when the vehicle moves over any surface. The rolling resistance force is given by the expression,

Frr = urr * (m.g)

Where

m.g = weight in Newton

urrr = coefficient of rolling resistance.

The coefficient of rolling resistance (or) depends on many factors like the Tyre Pressure, Tyre Temperature, Material of the Tyre, Thread pattern of the Tyre, and also the Road Roughness and Liquids on the Road. These factors determine the rolling resistance force.

(iv) Tyre Pressure:

The pressure generally is very high in an aircraft tire to reduce the rolling resistance and to withstand the weight. Usually, it will be around 200 to 300 psi of pressure and they change based on the type of the aircraft. Tests of airliner aircraft tyres have shown that they can sustain pressures of a maximum of 800 psi. Aircraft tyres are usually inflated with nitrogen to minimize expansion and contraction from extreme changes in ambient temperature and pressure experienced during flight.

(v) Brake force while Landing:

Aircraft disc brakes

Aircraft has disc rotors in the landing gear, used to break the wheels while touching the ground. These brakes are operated hydraulically or pneumatically.

Thrust reversers

Thrust reversers allow thrust from the engines to be used to slow the aircraft. This is also very effective in bringing down the speed of the aircraft. By using a negative angle plane, we are turning the wind that is coming into the propeller to flow in the opposite direction

Air Brake

Air brake dedicated flight control surface that works by increasing the drag force, air brakes are designed to increase drag while making little change to lift, resulting in a higher stall speed. These are some of the types of braking methods used to bring down the aircraft's speed while landing the flight.

Large drogue parachutes

It is used by several former and current military and civilian aircraft (examples include the American B-52 and the soviet Tu-134 and Tu-144) and in the Space Shuttle.

Objective No. (6):

To push or pull an aircraft by a towing vehicle, 3 types of forces will act on that vehicle. Those are -

(i) Rolling resistance force (ii) Aerodynamic drag force 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 be overcome to move a vehicle. The kinetic energy of the wheels is partially converted into heat. The rolling resistance is proportional to the normal force perpendicular to the rolling wheel and is approximated by the rolling resistance coefficient urr. Therefore, the Equation that can be used for the rolling resistance force of the entire system is-

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

urr of Car for different condition-
CONDITION	urr
Tires on concrete or asphalt	0.013
Tires on rolled gravel	0.02
Tarmacadam	0.025
Unpaved road	0.05
Field	0.1 - 0.35

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

(ii) Aerodynamic drag force(Fad): Aerodynamic drag force is the force that is required to keep a vehicle moving. There is two-component of this force, one is shape 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 velocity of air near the boundary is higher than the air surrounding it. Both the tug and the aircraft will experience some aerodynamic drag. For completeness, the aerodynamic drag force caused by the aircraft and towing vehicle can be given by Equation below-

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 (It depends on frontal area, shape, protrusions, ducts, air passage, etc.) v = Velocity of the vehicle in m/s

Concerning the drag equation, the term A simply refers to some reference area. For airplanes, this is generally the planform area of the wing The designers design an aircraft in such a way that the reference area is optimal. So, for calculation, this has been neglected.

Cd for different types of vehicle-
VEHICLE TYPE	Cd
Open Convertible	0.5 - 0.7
Van body	0.5 - 0.7
Ponton body	0.4 - 0.55
wedge-shaped body, head lamps and bumpers are integrated into the body, covered unready optimized cooling airflow	0.3 - 0.4
Motor cycle	0.6 - 0.7
racing car	0.2 - 0.25

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 an up gradient. To Hill Climbing force the expression of the equation is given 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-

Let's assume,the towing vehicle mass = 50000 Kg,

the aircraft mass or payload on towing vehicle = 183700 Kg,

total mass of the vehicle(m) = (50000+183700) = 233700 Kg,

towing vehicle fontal area(A) = 20 m^2

speed of the vehicle(V) = 30 Km/hr = 8.333 m/s

Rolling Resistance Force(Frr) = urr * m * g =0.013 * (50000+183700) * 9.8 =29,773.38 N

Aerodynamic Drag Force(Fad) = (1/2) * ρ * V^2 * A * (Cd_t + Cd_a)= (1/2) * 1.225 * (2.778)^2 * 20 * (0.5+0.045)= 51.514 N

Hill Climbing Force(Fhc) = m * g * sinφ =(50000+183700) * 9.8 * sin0 = 0 N

Total required traction power(Tf) = Frr + Fad + Fhc =29773.38 + 51.514 + 0 =29824.894 N

Push/Pull Power Calculation of Towing Vehicle-

Objective No. (7):

Table for the necessary assumed parameters-

Assumption For Powertrain Design-
Aircraft Mass	183700 Kg
Towing Vehicle Mass	50000 Kg
Rolling Resistance Co-efficient	0.013
Air Density	1.225 kg/m^3
Towing Vehicle Drag Co-efficient	0.5
Aircraft Drag Co-efficient	0.045
Frontal area	20 m^2
Inclination Angle	0 rad
Tyre Pressure	203 PSI/14 bar
Towing Velocity(V)	10km/h =2.778m/s
Towing Time(t)	2 min
Radius of the towing vehicle wheel	0.38 m

Therefore from the excel power calculator we have got the necessary Traction force(F) quantity that is = 29824.89427 N

and Required power(P) = F * V = 29824.894 * 2.778 =82846.928 W = 82.846 KW

As we know Torque(T) = Force(F) * Wheel radious(r) So, from the above equation we have got the required torque(T) = 29824.894 * 0.38 = 11333.45972 N-m.

Required Energy(E) for towing application based on the assumed time, that is E = P * t = 82.846 * (120/3600)= 2.761 KWh

For this application, an Induction motor or a BLDC can be used with a proper gear system.

Fig- Induction Asynchronous motor

Induction Motor Rating-
Output Mechanical Power	Horse Power	Input In term of Mechanical Power	No of Phases	Input Voltage	Input Current	Efficiency
90 KW	120 H.P	95.642 KW	3	380 V	163.3 A	94.10%
				400 V	155.1 A
				415 V	149.5 A

The motor output power is the input power of the towing vehicle so to obtain maximum speed, the duty cycle needed is calculated as below- Duty Cycle = Output Power/Input Power = (82.846/90)*100 = (0.921*100)%, so the duty cycle will be 92.1% The duty cycle range to control the aircraft speed from zero to highest is from 0 to 92.1 %

Towing Vehicles

Towing Vehicle Simulink Powertrain Block model- Though an Induction motor has been chosen for this application here this Simulink model is built based on a DC motor.

Torque Characteristic- Here torque is in unit of N-m.

Speed Characteristic- Here speed is in the unit of rad/sec.

Block Diagram of Powertrain for Towing Vehicle-

Electric Vehicles, consist of a battery, connected to an electric motor (either AC or DC) via an inverter and a motor controller. As automotive batteries generally operate on DC, while the gird operates AC, a converter is needed to transfer power to the battery. One of the key advantages of an EV is its much higher levels of energy efficiency. Typically an EV will achieve a system efficiency of 80% from battery to wheel (roughly 60% from the grid to wheel), while with a conventional IC engine it’s more like 15-25%. This is large because an IC engine is a “heat engine” (i.e. it has to burn fuel and produce heat to operate) and much of all that heat is simply wasted.

Conclusions: All the problem statements are answered and all the needed diagrams or results are also provided.

References:

1. https://aviation.stackexchange.com/questions/12956/what-are-different-types-of-weights-of-an-aircraft
2. https://en.wikipedia.org/wiki/Aircraft_gross_weight
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4. https://m.blog.naver.com/fltops/110226753
5. https://en.wikipedia.org/wiki/List_of_airliners_by_maximum_takeoff_weight
6. https://en.wikipedia.org/wiki/Pushback
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9. https://evreporter.com/ev-powertrain-components/#:~:text=An%20EV%20powertrain%20has%2060,The%20components%20are%20described%20below.&text=Battery%20Pack%20%E2%80%93%20The%20battery%20pack,direct%20current%20(DC)%20output.
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17. https://www.nata.aero/agso/astgcache/1a96deb7-7c34-46db-ace7-df80a2d693ce.pdf