Powertrain for aircraft in runways

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

Weight is the force generated by the gravitational attraction of the earth on the airplane. Each part of the aircraft has a unique weight and mass, and for some problems, it is important to know the distribution. But for total aircraft maneuvering, we only need to be concerned with the total weight and the location of the center of gravity. The center of gravity is the average location of the mass of any object.

An airplane is a combination of many parts; the wings, engines, fuselage, and tail, plus the payload and the fuel. Each part has a weight associated with it which the engineer can estimate, or calculate, using Newton's weight equation:

• w = m * g

where w is the weight, m is the mass, and g is the gravitational constant which is 32.2 ft/square sec in English units and 9.8 meters/square sec in metric units. The mass of an individual component can be calculated if we know the size of the component and its chemical composition. Every material (iron, plastic, aluminum, gasoline, etc.) has a unique density. Density r is defined to be the mass divided by the volume v:

• r = m / v

If we can calculate the volume

• m = r * v

The total weight W of the aircraft is simply the sum of the weight of all of the individual components.

• W = w(fuselage) + w(wing) + w(engines) + w(payload) + w(fuel) + ...

 

The aircraft gross weight (also known as the all-up weight and abbreviated AUW) is the total aircraft weight at any moment during the flight or ground operation. An aircraft's gross weight will decrease during a flight due to fuel and oil consumption. An aircraft's gross weight may also vary during a flight due to payload dropping or in-flight refueling. At the moment of releasing its brakes, the gross weight of an aircraft is equal to its takeoff weight. During the flight, an aircraft's gross weight is referred to as the en-route weight or in-flight weight.

Maximum taxi weight (MTW):

• The maximum taxi weight (MTW) (also known as the maximum ramp weight (MRW) is the maximum weight authorized for maneuvering (taxiing or towing) an aircraft on the ground as limited by aircraft strength and airworthiness requirements. It includes the weight of the taxi and run-up fuel for the engines and the APU.
• It is greater than the maximum takeoff weight due to the fuel that will be burned during the taxi and runup operations.
• The difference between the maximum taxi/ramp weight and the maximum take-off weight (maximum taxi fuel allowance) depends on the size of the aircraft, the number of engines, APU operation, and engines/APU fuel consumption, and is typically assumed for 10 to 15 minutes allowance of taxi and run-up operations.

Maximum takeoff weight (MTOW):

• The maximum takeoff weight (also known as the maximum brake-release weight) is the maximum weight authorized 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 authorized for the normal landing of an aircraft. It 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.

Maximum zero-fuel weight (MZFW):

The maximum permissible weight of the aircraft less all usable fuel and other specified usable agents (engine injection fluid, and other consumable propulsion agents). It is the maximum weight permitted before usable fuel and other specified usable fluids are loaded in specified sections of the airplane.

Types of 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	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	381,000	288.417	2530	1494	Heavy	Heavy
Boeing 747-200	377,840	285.700	3338	2109	Heavy	Heavy
Boeing 747-300	377,840	260.320	3222	1905	Heavy	Heavy
Airbus A340-500	371,950	240	3050	2010	Heavy	Heavy
Airbus A340-600	367,400	256	3100	2100	Heavy	Heavy
Boeing 777F	347,800	260.816	2830		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	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	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	254,000	192.777	2900		Heavy	Heavy
Boeing 787-10	254,000	201.849			Heavy	Heavy
Airbus A340-200	253,500	181	2990		Heavy	Heavy
Ilyushin IL-96-300	250,000	175	2600	1980	Heavy	Heavy
Airbus A330-300	242,000	185	2500	1750	Heavy	Heavy
Airbus A330-200	242,000	180	2220	1750	Heavy	Heavy
Lockheed L-1011-500	231,300	166.92	2636		Heavy	Heavy
Boeing 787-8	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	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	163,000	138	2324	1536	Heavy	Heavy
Boeing 767-300	159,000	136.078	2713	1676	Heavy	Heavy
Airbus A310-300	157,000	124	2290	1490	Heavy	Heavy
Vickers VC10	152,000	151.9			Heavy	Heavy
Boeing 707-320B	151,000	97.5			Heavy	Heavy
Boeing 707-320C	151,000	112.1			Heavy	Heavy
Douglas DC-8-61	147,000				Heavy	Heavy
Airbus A310-200	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	117,000	86.3			Medium	Large
Boeing 757-200	116,000	89.9	2347	1555	Medium	Large
Boeing 720B	106,000	79.5			Medium	Large
Boeing 720	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	84,000	70.1			Medium	Large
Airbus A321-100	83,000	77.8	2200	1540	Medium	Large
Boeing 737-800	79,000	65.32	2308	1634	Medium	Large
Boeing 727-200	78,000	68.1			Medium	Large
McDonnell-Douglas MD-83	73,000	63.28			Medium	Large
Boeing 727-100	72,500	62.4			Medium	Large
Boeing 727-100C	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	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	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	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	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	37,500	32.8	2244	1304	Medium	Large
Bombardier CRJ900	36,500	33.345	1778	1596	Medium	Large
Embraer 170	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	9,752	8.709	1353	811	Medium	Small
Pilatus PC-24	8,300	7.665	893	724	Medium	Small
Embraer Phenom 300	8,150	7.65	956	677	Medium	Small
Beechcraft 1900D	7,765	7.605	1036	853	Medium	Small
Cessna Citation CJ4	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

 

2) Is there any difference between ground speed and airspeed? 

Ground Speed:

• Ground speed is the horizontal speed of an aircraft relative to the Earth’s surface. It is vital for accurate navigation to the destination that the pilot has an estimate of the ground speed that will be achieved during a flight.
• An aircraft diving vertically would have a ground speed of zero. The information displayed to passengers through the entertainment system of airline aircraft usually gives the aircraft ground speed rather than airspeed.
• Ground speed can be determined by the vector sum of the aircraft's true airspeed and the current wind speed and direction; a headwind subtracts from the ground speed, while a tailwind adds to it. Winds at other angles to the heading will have components of either headwind or tailwind as well as a crosswind component.
• An airspeed indicator indicates the aircraft's speed relative to the air mass. The air mass may be moving over the ground due to wind, and therefore some additional means to provide position over the ground is required. This might be through navigation using landmarks, radio-aided position location, an inertial navigation system, or GPS.

Air Speed:

Airspeed is the speed of an aircraft relative to the air. Among the common conventions for qualifying airspeed are indicated airspeed ("IAS"), calibrated airspeed ("CAS"), equivalent airspeed ("EAS"), true airspeed ("TAS"), and density airspeed.

• Indicated airspeed is simply what is read off of an airspeed gauge connected to a pitot-static system,
• Calibrated airspeed is indicated airspeed adjusted for pitot system position and installation error, 
• Equivalent airspeed is calibrated airspeed adjusted for compressibility effects.
• True airspeed is equivalent airspeed adjusted for air density and is also the speed of the aircraft through the air in which it is flying.

Calibrated airspeed is typically within a few knots of indicated airspeed, while equivalent airspeed decreases slightly from CAS as aircraft altitude increases or at high speeds. With EAS constant, true airspeed increases as aircraft altitude increases. This is because air density decreases with a higher altitude, but an aircraft's wing requires the same amount of air particles (i.e., the mass of air) flowing around it to produce the same amount of lift for a given angle of attack; thus, a wing must move faster through thinner air than thicker air to obtain the same amount of lift.

The measurement and indication of airspeed are ordinarily accomplished onboard an aircraft by an airspeed indicator ("ASI") connected to a pitot-static system. The pitot-static system comprises one or more pitot probes (or tubes) facing the on-coming airflow to measure pitot pressure (also called stagnation, total, or ram pressure) and one or more static ports to measure the static pressure in the airflow. These two pressures are compared by the ASI to give an IAS reading.

 

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

• Boeing commercial airplanes are equipped with engines rated from 18,000 to nearly 100,000 lb of thrust. Such thrust levels provide for a safe takeoff, flight, and landing over a wide range of temperatures, altitudes, gross weights, and payload conditions. However, the exhaust wake from these engines can pose hazards in commercial airport environments. Operators and airport authorities must carefully consider these hazards and the resulting potential for injury to people and damage to or caused by baggage carts, service vehicles, airport infrastructure, and other airplanes.
• When modern jet engines are operated at rated thrust levels, the exhaust wake can exceed 375 mi/h (325 kn or 603 km/h) immediately aft of the engine exhaust nozzle. This exhaust flow field extends aft in a rapidly expanding cone, with portions of the flow field contacting and extending aft along the pavement surface (fig. 1). Exhaust velocity components are attenuated with increasing distance from the engine exhaust nozzle. However, an airflow of 300 mi/h (260 kn or 483 km/h) can still be present at the empennage, and significant people and equipment hazards will persist hundreds of feet beyond this area. At full power, the exhaust wake speed can typically be 150 mi/h (130 kn or 240 km/h) at 200 ft (61 m) beyond the airplane and 50 to 100 mi/h (43 to 88 kn or 80 to 161 km/h) well beyond this point.
• One approach to relating these values to airport operations is to consider the hurricane intensity scale used by the U.S. National Oceanic and Atmospheric Administration. A Category 1 hurricane has sustained winds of 74 to 95 mi/h (64 to 82 kn or 119 to 153 km/h). At these velocities, minimal damage to stationary building structures would be anticipated, but more damage to unanchored mobile homes and utility structures would be expected. An idling airplane can produce a compact version of a Category 3 hurricane, introducing an engine wake approaching 120 mi/h (104 kn or 192 km/h) with temperatures of 100°F (38°C). This wake velocity can increase two or three times as the throttles are advanced and the airplane begins to taxi.
• At the extreme end of the intensity, the scale is a Category 5 hurricane, with winds greater than 155 mi/h (135 kn or 249 km/h). Residential and industrial structures would experience roof failure, with lower-strength structures experiencing complete collapse. Mobile homes, utility buildings, and utilities would be extensively damaged or destroyed, as would trees, shrubs, and landscaping. 

Thousands of safe takeoffs and landings occur throughout the world every day. Each operation takes advantage of the benefits supplied by the high thrust levels of modern jet engines. However, during taxi and maintenance activity, this same thrust capability and its related exhaust wake can become a hazard, which can be intensified by a lack of awareness about how the exhaust wake affects the surrounding environment. Techniques and precautions designed to help operators deal with high thrust exhaust wakes are available in Boeing publications and other document sources. Operators should use this information to develop the necessary operational procedures and should address the engine wake hazard issue in their safety awareness and training programs.

 

4) How an aircraft is pushed to the runway when it's ready to take off?  

• Taxiing (rarely spelled taxying) is the movement of an aircraft on the ground, under its own power, in contrast to towing or pushback 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 is called the takeoff roll and landing rollout, respectively.
• When taxiing, aircraft travel slowly. This ensures that they can be stopped quickly and do not risk wheel damage on larger aircraft if they accidentally turn off the paved surface. Taxi speeds are typically 30 to 35 km/h (16 to 19 kn).

Equipment:

Moving Light Aircraft:

Very small airplanes may be moved by human power alone. The airplane may be pushed or pulled by landing gear or wing struts since they're known to be strong enough to drag the airplane through the air. To allow for turns, a person may either pick up or push down on the tail to raise either the nose wheel or tail wheel off the ground, then rotate the airplane by hand. A less cumbersome method involves attaching a short tow bar to either the nose wheel or tail wheel, which provides a solid handhold and leverage to steer with, as well as eliminates the danger of handling the propeller. These tow bars are usually a lightweight aluminum alloy construction which allows them to be carried onboard the airplane. Other small tow bars have a powered wheel to help move the airplane, with power sources as diverse as lawnmower engines or battery-operated electric drills. However, powered tow bars are usually too large and heavy to be practically carried on small airplanes.

  

Tractors and Towbars:

Large aircraft cannot be moved by hand and must have a tractor or tug. Pushback tractors use a low-profile design to fit under the aircraft's nose. For sufficient traction, the tractor must be heavy, and most models can have extra ballast added. A typical tractor for large aircraft weighs up to 54 tonnes (59.5 short tons; 53.1 long tons; 119,000 pounds) and has a drawbar pull of 334 kN (75,000 lbf). Often the driver's cabin can be raised for increased visibility when reversing and lowered to fit under aircraft.

  

 

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

Takeoff Power:

Takeoff is the phase of flight in which an aerospace vehicle leaves the ground and becomes airborne. 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. The nose is raised to a nominal 5°–15° nose-up pitch attitude to increase lift from the wings and effect liftoff. For most aircraft, attempting a takeoff without a pitch-up would require cruise speeds while still on the runway.The speeds needed for takeoff are relative to the motion of the air (indicated airspeed). A headwind will reduce the ground speed needed for takeoff, as there is a greater flow of air over the wings. Typical takeoff air speeds for jetliners are in the range of 240–285 km/h (130–154 kn; 149–177 mph). Light aircraft, such as a Cessna 150, take off at around 100 km/h (54 kn; 62 mph). Ultralights have even lower takeoff speeds. For a given aircraft, the takeoff speed is usually dependent on the aircraft's weight; the heavier the weight, the greater the speed needed.

Tire Design:

• An aircraft tire or tire 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 the 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.

• When it comes to safety, tires 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 the braking and stopping of an aircraft. A Boeing 737NG & 737MAX uses 6 wheels, Boeing 787 uses 10 wheels, Boeing 777 uses 14 wheels and Airbus A380 uses 22 wheels. Aircraft tires 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.

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 braking and stopping an airplane.
• Tyre also helps to absorb the shock of landing and provides cushioning for the roughness of takeoff, roll-out, and taxi operations.

Unlike an automobile or truck tire, 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.

 

• Tread: The tread is made of rubber mixed with other additives to obtain the desired level of toughness, durability, and resistance to wear. The tread pattern is designed to aircraft operational requirements, with the ribbed tread design used widely due to its good traction under varying runway conditions.

• Sidewall: The sidewall is a protective layer of rubber that covers the outer casing ply. It extends from the tread edge to the bead area.

• Tread Reinforcing Ply: One or more layers of fabric that strengthens and stabilizes the tread area for high-speed operation. It also serves as a reference for the buffing process when tires are retreaded.
• Buff Line Cushion: The buff line cushion is made of rubber compound to enhance the adhesion between the tread reinforcing ply and the breakers or casing plies. It is of sufficient thickness to allow for the removal of the old tread when the tire is retreaded.
• Breakers: Breakers are reinforcing plies of rubber-coated fabric placed under the buff line cushion to protect casing plies and strengthen and stabilize the tread area. They are considered an integral part of the casing construction.
• Casing Plies: Alternate layers of rubber-coated fabric (running at opposite angles to one another) provide the strength of the tire.
• Wire Beads: Hoops of high tensile strength steel wire that anchor the casing plies and provide a firm mounting surface on the wheel. The outer edge of the bead that fits against the wheel flange is called the bead heel. The inner bead edge is called the bead toe.
• Apex Strip: A wedge of rubber affixed to the top of the bead bundle.
• Flippers: Layers of rubberized fabric that help anchor the bead wires to the casing and improve the durability of the tire.
• Ply Turnups: The casing plies are anchored by wrapping them around the wire beads, thus forming the ply turnups.
• Chafer: A protective layer of rubber and/or fabric located between the casing plies and wheel to minimize chafing.
• Liner: In tubeless tires, the liner is a layer of low permeability rubber that acts as a built-in tube and restricts gas from diffusing into the casing plies. In tube-type tires, a thinner liner is used to prevent tube chafing against the inside ply.

Aircraft tires are classified in various ways including by type, ply rating, whether they are tube-type or tubeless, and whether they are bias-ply tires or radials. Identifying a tire by its dimensions is also used. Each of these classifications is discussed as follows.

• Common classification of aircraft tires is by type as classified by the United States Tire and Rim Association. While there are nine types of tires, only Types I, III, VII, and VIII, also known as a Three-Part Nomenclature tires, are still in production.Type I tires are manufactured, but their design is no longer active. They are used on fixed gear aircraft and are designated only by their nominal overall diameter in inches. These are smooth profile tires that are obsolete for use in the modern aviation fleet. They may be found on older aircraft.
• Type III tires are common general aviation tires. They are typically used on light aircraft with landing speeds of 160 miles per hour (mph) or less. Type III tires are relatively low-pressure tires that have small rim diameters when compared to the overall width of the tire. They are designed to cushion and provide flotation from a relatively large footprint. Type III tires are designated with a two number system. The first number is the nominal section width of the tire, and the second number is the diameter of the rim the tire is designed to mount upon.For example: 6.00 – 6 is a Cessna 172 tire that is 6.00 inches wide and fits on a rim that has a diameter of 6 inches.

• Type VII tires are high-performance tires found on jet aircraft. They are inflated to high-pressure and have exceptional high load-carrying capability. The section width of Type VII tires is typically narrower than Type III tires. Identification of Type VII aircraft tires involves a two-number system. An X is used between the two numbers. The first number designates the nominal overall diameter of the tire. The second number designates the section width. For example, 26 X 6.6 identifies a tire that is 26 inches in diameter with a 6.6-inch nominal width.

• Type VIII aircraft tires are also known as three-part nomenclature tires. They are inflated to very high-pressure and are used on high-performance jet aircraft. The typical Type VIII tire has a relatively low profile and is capable of operating at very high speeds and very high loads. It is the most modern design of all tire types. The three-part nomenclature is a combination of Type III and Type VII nomenclature where the overall tire diameter, section width, and rim diameter are used to identify the tire. The X and “–” symbols are used in the same respective positions in the designator.
• When three-part nomenclature is used on a Type VIII tire, dimensions may be represented in inches or in millimeters. Bias tires follow the designation nomenclature and radial tires replace the “–” with the letter R. For example, 30 X 8.8 R 15 designates a Type VIII radial aircraft tire with a 30-inch tire diameter, an 8.8-inch section width to be mounted on a 15-inch wheel rim.A few special designators may also be found for aircraft tires. When a B appears before the identifier, the tire has a wheel rim to section width ratio of 60 to 70 percent with a bead taper of 15 degrees. When an H appears before the identifier, the tire has a 60 to 70 percent wheel rim to section width ratio but a bead taper of only 5 degrees.
• Aircraft tires can be tube-type or tubeless. This is often used as a means of tire classification. Tires that are made to be used without a tube inserted inside have an inner liner specifically designed to hold air. Tube-type tires do not contain this inner liner since the tube holds the air from leaking out of the tire. Tires that are meant to be used without a tube have the word tubeless on the sidewall. If this designation is absent, the tire requires a tube.

Tire Pressure:

• To perform as designed, an aircraft tire must be properly inflated. The aircraft manufacturer’s maintenance data must be used to ascertain the correct inflation pressure for a tire on a particular aircraft. Do not inflate to a pressure displayed on the sidewall of the tire or by how the tire looks. Tire pressure is checked while under load and is measured with the weight of the aircraft on the wheels. Loaded versus unloaded pressure readings can vary as much as 4 percent. Tire pressure measured with the aircraft on jacks or when the tire is not installed is lower due to the larger volume of the inflation gas space inside of the tire. On a tire designed to be inflated to 160 psi, this can result in a 6.4 psi error. A calibrated pressure gauge should always be used to measure inflation pressure. Digital and dial-type pressure gauges are more consistently accurate and preferred.

• Aircraft tires disperse the energy from landing, rollout, taxi, and takeoff in the form of heat. As the tire flexes, heat builds and is transferred to the atmosphere, as well as to the wheel rim through the tire bead. The heat from braking also heats the tire externally. A limited amount of heat is able to be handled by any tire beyond which structural damage occurs.
• An improperly inflated aircraft tire can sustain internal damage that is not readily visible and that can lead to tire failure. Tire failure upon landing is always dangerous. An aircraft tire is designed to flex and absorb the shock of landing. Temperature rises as a result. However, an underinflated tire may flex beyond design limits of the tire. This causes excessive heat build-up that weakens the carcass construction. To ensure tire temperature is maintained within limits, tire pressure must be checked and maintained within the proper range on a daily basis or before each flight if the aircraft is only flown periodically.

Rolling Resistance:

Rolling resistance sometimes called rolling friction or rolling drag is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface. 

The "rolling resistance coefficient" is defined by the following equation:

where;

•  is the rolling resistance force 
•  is the dimensionless rolling resistance coefficient or the coefficient of rolling friction (CRF) and
•  is the normal force, the force perpendicular to the surface on which the wheel is rolling.

As an alternative to using  one can use , which is a different rolling resistance coefficient or the coefficient of rolling friction with the dimension of length. It is defined by the following formula:

where;

•  is the rolling resistance force
•  is the wheel radius,
•  is the rolling resistance coefficient or the coefficient of rolling friction with a dimension of length, and
•  is the normal force

Brake Force while Landing:

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. Brakes provide this critical stopping function during landings to enable airplanes to stop within the length of the runway. They also stop aircraft during rejected takeoff events, in which an attempted takeoff is canceled as the airplane is rolling down the runway before it lifts off from the ground due to engine failure, tire blowout, other system failures, or direction from air traffic control. Aircraft brakes also prevent the motion of the aircraft when it is parked, limit its speed during taxiing, and can even help steer the aircraft on the ground by applying different levels of braking force to the left- and right-side brakes. 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.

The following braking methods are used to decelerate the aircraft until it stops:

• Engine brake/Thrust-reverser
• Wheel brake
• Mechanical spoilers

Engine Brake:

The most important action to achieve deceleration from a speed at which the engines are still producing forward motion is to select all thrust/power levers to the ground idle position promptly, and if available, continue the action through to the selection of reverse thrust or reverse propeller pitch. This is the first action to begin deceleration and must especially be achieved without delay when a high-speed rejected take-off is initiated. Thrust reversers and reverse propeller pitch are most effective at high speeds. Once the aircraft groundspeed has reduced sufficiently, thrust/power levers should be returned to the ground idle position to prevent ingestion of any FOD(Foreign Object Debris) which could be present, with reversers stowed once at taxi speed.

Wheel Brake:

To be effective, braking action at any speed depends upon sufficient friction existing between the tires and the runway surface achieved through freely rotating wheels.

Fundamentals to this are:

• Achieving the maximum possible weight on braked landing gear assemblies
• The condition of the tire tread
• The tire inflation pressure
• The condition of the runway surface

Anti Skid Units are fitted to the braking systems of all modern transport aircraft. They modulate applied brake system hydraulic pressure before it is transmitted to the actuators in the brake units so as to obtain optimum braking based upon wheel rotational speed data received at the Unit. A minimum wheel rotational speed must be detected before any brake application will be achieved to prevent tire destruction resulting from a locked wheel and to guard against the risk of Aquaplaning on wet or icy runway surfaces.

Autobrake Systems provide pre-selectable rates of deceleration which usually vary between 3 and 6 knots per second constant deceleration rate. Selection of ‘Low’ auto brake on an aircraft equipped with thrust reversers will usually have the effect of delaying brake application to allow the thrust reversers to work efficiently in reducing the initial high ground speed. Maximum manual braking through the toe brakes can produce deceleration rates of up to 10 kts per second subject to the operation of anti-skid units. Modern landing gear assemblies on fixed-wing transport aircraft are fitted with carbon brakes, although steel brakes may still be encountered on older aircraft types.

Mechanical Spoilers:

The mechanical deflection of parts of the wing upper surfaces and tail cone assembly can assist deceleration in two ways:

1. Directly, by increasing aerodynamic drag on the moving aircraft. This can be achieved by raising upper wing surface panels called ground spoilers or by operating of a tail cone ‘clamshell’ type air brake. Both systems can also be used in the air on some aircraft types as in-flight air brakes, but the extent of their operation may be less in the airborne case than in the ground (weight on wheels) case. Extreme care may be needed if it is permissible for a particular aircraft type to carry out a rejected landing after initial touchdown since not all ground settings of deployed spoilers and air brakes necessarily auto retract to the settings needed for a safe initial climb away.
2. Indirectly by increasing the effective downward load on the landing gear and thereby increasing the efficiency of wheel braking.

 

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

Assumptions:

Parameters:	Value:
1) Mass of Aircraft (Airbus A330) in kg	242000
2) Acceleration due to gravity in m/s^2	9.81
3) Pressure in aircraft tire in bar	14
4) Velocity of aircraft in km/h	10
5) Mass of towing vehicle in kg	50000
6) Pressure in the tow vehicle tire in psi	32
7) Velocity of the tow vehicle in km/h	10
8) Density of the air in kg/m^3	1.25
9) Frontal area in m^2	20
10) Coefficient of rolling resistance for aircraft	0.005
11) Coefficient of rolling resistance for tow vehicle	0.0045
12) Coefficient of drag	0.5
13) Radius of tow wheel in mm	0.38
14) Towing time in min	2

Rolling Force:

For aircraft,

Rolling force is given by the formula:

`Fr=mur*m*g`

where,

`Fr=`rolling force in N

`mur=`coefficient of rolling resistance

m=mass of aircraft in kg

g=acceleration due to gravity in m/s^2

`mur` can be calculated by the formula:

`mu=0.005+(1/p)*((0.01+0.0095)(v/100)^2)`

where,

`mu=`rolling cofficient

p=tire pressure (bar)

v=velocity (km/h)

By substituting,

`Fr=0.005*242000*9.81=11870.1N.......eq1()`

For towing vehicle,

`Fr=mur*m*g`

By substituting,

`Fr=0.0045*50000*9.81=2207.25N.......eq(2)`

Drag Force:

By substituting,

`Fd=(1/2)*1.25*0.5*20*(10*5/18)^2=48.225N.......eq(3)`

Now, the total force is,

`Ft=11870.1+2207.25+48.225`

`Ft=14125.575N`

Power:

`P=Ft*v`

`P=14125.575*(10*5/18)`

`P=39.23kW`

Torque:

`T=Ft*r`

`T=14125.575*0.38`

`T=5367.71Nm`

Energy:

`E=P*t`

`E=39.23*120/3600`

`E=1.307kWh`

 

7) Design an electric powertrain with the 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. 

*From above, it is clear that the power required for towing is 39.23kW.

For this, the 3-phase Induction motor with a rating is given in below table:

1) Motor rating in kW	45
2) Number of phases	3
3) Horsepower	60
4) Frequency in Hz	50
5) Rated voltage in V, Current in A	(240,187.5), (380,118.42), (415,108.43)
6) Efficiency	>80%

Power Input:

Pi=V*I

where, 

V= voltage in volts

I=curren in Amps

Pi=415*108.43

Pi=45kW

Energy:

`E=P*t`

`E=45*120/3600`

`E=1.5kWh`

Duty Cycle:

D=Po/Pi

`D=39.23/45=0.871`

`therefore`The duty cycle range to control the aircraft speed from zero to highest is 0 to 0.871%.

Powertrain:

• As the name suggests, the powertrain provides power to the vehicle. Powertrain refers to the set of components that generate the power required to move the vehicle and deliver it to the wheels.
• An EV powertrain has 60% fewer components than the powertrain of an ICE vehicle. The components are described below.

Components:

• Battery Pack – The battery pack is made up of multiple Lithium-ion cells and stores the energy needed to run the vehicle. Battery packs provide direct current (DC) output.
• DC - AC Converter – The DC supplied by the battery pack is converted to AC and supplied to the electric motor. This power transfer is managed by a sophisticated motor control mechanism  (also referred to as Powertrain Electronic Control Unit) that controls the frequency and magnitude of the voltage supplied to the electric motor in order to manage the speed and acceleration as per the driver’s instructions communicated via acceleration/brakes.
• Electric Motor – Converts electrical energy to mechanical energy, that is delivered to the wheels via single ratio transmission. Many EVs use motor generators that can perform regeneration as well.
• Onboard Charger  – Converts AC received through charge port to DC and controls the amount of current flowing into the battery pack.

Apart from the above core parts, there are multiple hardware and software components in an EV powertrain. Electronic Control Units (ECUs) are basically software programs integrated with the powertrain components to help data exchange and processing, e.g. Powertrain ECU mentioned above. There are several small ECUs in an EV that perform specific functions. The communication between different ECUs in a vehicle is commonly carried over CAN protocol. More examples of core ECUs are:

• Battery Management System (BMS) - A BMS continuously monitors the state of the battery and is responsible for taking necessary measures in case of a malfunction. BMS performs cell balancing to deliver maximum efficiency from the battery pack. It is responsible for communication with other ECUs and sensors, as well as EVSEs to control the charging input, check the current state of charge, and share data about battery specifications. 
• DC-DC Converter – A battery pack delivers a fixed voltage, but the requirement of different accessory systems (e.g. wipers, lights, infotainment system, mirror control) in the EV would vary. The DC-DC converter helps distribute power to different systems by converting the output power from the battery pack to the expected level. After conversion, power is delivered to respective smaller ECUs via a wiring harness.
• Thermal Management System - Responsible for maintaining optimum operating temperature range for powertrain components.
• Body Contro Module (BCM) - The BCM is responsible for supervising and controlling the functions of electronic accessories such as power windows, mirrors, security, and vehicle access control. 

 

References:

1. https://en.wikipedia.org/wiki/List_of_airliners_by_maximum_takeoff_weight
2. https://en.wikipedia.org/wiki/Aircraft_gross_weight
3. https://www.grc.nasa.gov/www/k-12/airplane/weight2.html
4. https://en.wikipedia.org/wiki/Ground_speed#:~:text=Ground%20speed%20is%20the%20horizontal,a%20ground%20speed%20of%20zero.
5. https://en.wikipedia.org/wiki/Airspeed
6. http://www.boeing.com/commercial/aeromagazine/aero_06/textonly/s02txt.html#:~:text=High%20engine%20thrust%20during%20maintenance,elements%20in%20the%20airport%20environment
7. https://en.wikipedia.org/wiki/Taxiing
8. https://www.aircraftsystemstech.com/p/aircraft-tires-and-tubes-aircraft-tires.html
9. https://en.wikipedia.org/wiki/Aircraft_tire#:~:text=Aircraft%20tires%20generally%20operate%20at,294%20psi%20(20.3%20bar)
10. https://www.aviationhunt.com/aircraft-tyre-construction/
11. https://www.aviationpros.com/aircraft/article/10388042/understanding-the-basics-of-aircraft-tire-construction-and-maintenance
12. https://en.wikipedia.org/wiki/Rolling_resistance
13. https://insights.globalspec.com/article/12903/how-do-aircraft-brakes-work
14. https://evreporter.com/ev-powertrain-components/