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Project-1: Powertrain for aircraft in runways
Part A: 1. Search and list out the total weight of various types of aircrafts. ANSWER: AIRCRAFTS : An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of…
Somaraju Vijay Kumar
updated on 09 Feb 2023
Part A:
1. Search and list out the total weight of various types of aircrafts.
ANSWER: AIRCRAFTS :
An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. Common examples of aircraft include airplanes, helicopters, airships (including blimps), gliders, paramotors, and hot air balloons.
The human activity that surrounds aircraft is called aviation. The science of aviation, including designing and building aircraft, is called aeronautics. Crewed aircraft are flown by an onboard pilot, but unmanned aerial vehicles may be remotely controlled or self-controlled by onboard computers. Aircraft may be classified by different criteria, such as lift type, aircraft propulsion, usage and others.
Methods of lift
Lighter than air – aerostats
Aerostats use buoyancy to float in the air in much the same way that ships float on the water. They are characterized by one or more large cells or canopies, filled with a relatively low-density gas such as helium, hydrogen, or hot air, which is less dense than the surrounding air. When the weight of this is added to the weight of the aircraft structure, it adds up to the same weight as the air that the craft displaces.
Small hot-air balloons, called sky lanterns, were first invented in ancient China prior to the 3rd century BC and used primarily in cultural celebrations, and were only the second type of aircraft to fly, the first being kites, which were first invented in ancient China over two thousand years ago. (See Han Dynasty)
_in_flight_over_Manhattan,_circa_1931-1933.jpg)
A balloon was originally any aerostat, while the term airship was used for large, powered aircraft designs — usually fixed-wing.[3][4][5][6][7][8] In 1919, Frederick Handley Page was reported as referring to "ships of the air," with smaller passenger types as "Air yachts."[9] In the 1930s, large intercontinental flying boats were also sometimes referred to as "ships of the air" or "flying-ships".[10][11] — though none had yet been built. The advent of powered balloons, called dirigible balloons, and later of rigid hulls allowing a great increase in size, began to change the way these words were used. Huge powered aerostats, characterized by a rigid outer framework and separate aerodynamic skin surrounding the gas bags, were produced, the Zeppelins being the largest and most famous. There were still no fixed-wing aircraft or non-rigid balloons large enough to be called airships, so "airship" came to be synonymous with these aircraft. Then several accidents, such as the Hindenburg disaster in 1937, led to the demise of these airships. Nowadays a "balloon" is an unpowered aerostat and an "airship" is a powered one.
A powered, steerable aerostat is called a dirigible. Sometimes this term is applied only to non-rigid balloons, and sometimes dirigible balloon is regarded as the definition of an airship (which may then be rigid or non-rigid). Non-rigid dirigibles are characterized by a moderately aerodynamic gasbag with stabilizing fins at the back. These soon became known as blimps. During World War II, this shape was widely adopted for tethered balloons; in windy weather, this both reduces the strain on the tether and stabilizes the balloon. The nickname blimp was adopted along with the shape. In modern times, any small dirigible or airship is called a blimp, though a blimp may be unpowered as well as powered.
Heavier-than-air – aerodynes
Heavier-than-air aircraft, such as airplanes, must find some way to push air or gas downwards so that a reaction occurs (by Newton's laws of motion) to push the aircraft upwards. This dynamic movement through the air is the origin of the term. There are two ways to produce dynamic upthrust — aerodynamic lift, and powered lift in the form of engine thrust.
Aerodynamic lift involving wings is the most common, with fixed-wing aircraft being kept in the air by the forward movement of wings, and rotorcraft by spinning wing-shaped rotors sometimes called "rotary wings." A wing is a flat, horizontal surface, usually shaped in cross-section as an aerofoil. To fly, air must flow over the wing and generate lift. A flexible wing is a wing made of fabric or thin sheet material, often stretched over a rigid frame. A kite is tethered to the ground and relies on the speed of the wind over its wings, which may be flexible or rigid, fixed, or rotary.
With powered lift, the aircraft directs its engine thrust vertically downward. V/STOL aircraft, such as the Harrier jump jet and Lockheed Martin F-35B take off and land vertically using powered lift and transfer to aerodynamic lift in steady flight.
A pure rocket is not usually regarded as an aerodyne because it does not depend on the air for its lift (and can even fly into space); however, many aerodynamic lift vehicles have been powered or assisted by rocket motors. Rocket-powered missiles that obtain aerodynamic lift at very high speed due to airflow over their bodies are a marginal case.
Fixed-wing
The forerunner of the fixed-wing aircraft is the kite. Whereas a fixed-wing aircraft relies on its forward speed to create airflow over the wings, a kite is tethered to the ground and relies on the wind blowing over its wings to provide lift. Kites were the first kind of aircraft to fly and were invented in China around 500 BC. Much aerodynamic research was done with kites before test aircraft, wind tunnels, and computer modelling programs became available.
The first heavier-than-air craft capable of controlled free-flight were gliders. A glider designed by George Cayley carried out the first true manned, controlled flight in 1853.
The practical, powered, fixed-wing aircraft (the airplane or aeroplane) was invented by Wilbur and Orville Wright. Besides the method of propulsion, fixed-wing aircraft are in general characterized by their wing configuration. The most important wing characteristics are:
- Number of wings — monoplane, biplane, etc.
- Wing support — Braced or cantilever, rigid, or flexible.
- Wing planform — including aspect ratio, angle of sweep, and any variations along the span (including the important class of delta wings).
- Location of the horizontal stabilizer, if any.
- Dihedral angle — positive, zero, or negative (anhedral).
A variable geometry aircraft can change its wing configuration during flight.
A flying wing has no fuselage, though it may have small blisters or pods. The opposite of this is a lifting body, which has no wings, though it may have small stabilizing and control surfaces.
Wing-in-ground-effect vehicles are generally not considered aircraft.[12] They "fly" efficiently close to the surface of the ground or water, like conventional aircraft during takeoff. An example is the Russian ekranoplan nicknamed the "Caspian Sea Monster". Man-powered aircraft also rely on ground effect to remain airborne with minimal pilot power, but this is only because they are so underpowered—in fact, the airframe is capable of flying higher.
Rotorcraft
Rotorcraft, or rotary-wing aircraft, use a spinning rotor with aerofoil cross-section blades (a rotary wing) to provide lift. Types include helicopters, autogyros, and various hybrids such as gyrodynes and compound rotorcraft.
Helicopters have a rotor turned by an engine-driven shaft. The rotor pushes air downward to create lift. By tilting the rotor forward, the downward flow is tilted backward, producing thrust for forward flight. Some helicopters have more than one rotor and a few have rotors turned by gas jets at the tips. Some have a tail rotor to counteract the rotation of the main rotor, and to aid directional control.
Autogyros have unpowered rotors, with a separate power plant to provide thrust. The rotor is tilted backward. As the autogyro moves forward, air blows upward across the rotor, making it spin. This spinning increases the speed of airflow over the rotor, to provide lift. Rotor kites are unpowered autogyros, which are towed to give them forward speed or tethered to a static anchor in high-wind for kited flight.
Cyclogyros rotate their wings about a horizontal axis.
Compound rotorcraft have wings that provide some or all of the lift in forward flight. They are nowadays classified as powered lift types and not as rotorcraft. Tiltrotor aircraft (such as the Bell Boeing V-22 Osprey), tiltwing, tail-sitter, and coleopter aircraft have their rotors/propellers horizontal for vertical flight and vertical for forward flight.
Other methods of lift
- A lifting body is an aircraft body shaped to produce lift. If there are any wings, they are too small to provide significant lift and are used only for stability and control. Lifting bodies are not efficient: they suffer from high drag, and must also travel at high speed to generate enough lift to fly. Many of the research prototypes, such as the Martin Marietta X-24, which led up to the Space Shuttle, were lifting bodies, though the Space Shuttle is not, and some supersonic missiles obtain lift from the airflow over a tubular body.
- Powered lift types rely on engine-derived lift for vertical takeoff and landing (VTOL). Most types transition to fixed-wing lift for horizontal flight. Classes of powered lift types include VTOL jet aircraft (such as the Harrier jump jet) and tiltrotors, such as the Bell Boeing V-22 Osprey, among others. A few experimental designs rely entirely on engine thrust to provide lift throughout the whole flight, including personal fan-lift hover platforms and jetpacks. VTOL research designs include the Rolls-Royce Thrust Measuring Rig.
- The Flettner airplane uses a rotating cylinder in place of a fixed wing, obtaining lift from the Magnus effect.
- The ornithopter obtains thrust by flapping its wings.
- MTOW(maximum takeoff weight (MTOW)
The maximum takeoff weight (MTOW) or maximum gross takeoff weight (MGTOW) or maximum takeoff mass (MTOM) of an aircraft is the maximum weight at which the pilot is allowed to attempt to take off, due to structural or other limits. The analogous term for rockets is gross lift-off mass, or GLOW. MTOW is usually specified in units of kilograms or pounds.
MTOW is the heaviest weight at which the aircraft has been shown to meet all the airworthiness requirements applicable to it. MTOW of an aircraft is fixed and does not vary with altitude, air temperature, or the length of the runway to be used for takeoff or landing.
Maximum permissible takeoff weight or "regulated takeoff weight", varies according to flap setting, altitude, air temperature, length of runway and other factors. It is different from one takeoff to the next, but can never be higher than the MTOW.
- MLW maximum landing weight (MLW)
The maximum landing weight (MLW) is the maximum aircraft gross weight due to design or operational limitations at which an aircraft is permitted to land. The MLW is set in order to ensure safe landings; if an aircraft weighs too heavy during touchdown, it may suffer structural damage or even break apart upon landing. Aircraft also have a maximum take-off weight, which is almost always higher than the maximum landing weight, so that an aircraft can weigh less upon landing due to burning fuel during the flight.
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 unusually short duration, such as due to an emergency just after takeoff requiring a return to the airport, it may be necessary to dump fuel to reduce the landing weight. Some aircraft are unable to dump fuel, however. For example, on 3 February 2020, Air Canada Flight 837, a Boeing 767-300, suffered a rear tyre failure during take-off at Madrid–Barajas Airport on its way to Toronto, causing its left engine to catch fire. The pilots managed to extinguish it by shutting the engine down, but as 767-300s are not designed for fuel dumping, it had to stay in a single-engine holding pattern for over 4 hours to burn fuel and achieve its maximum landing weight, while an SAF fighter reported minimal damage to the landing gear. The plane landed safely and nobody was injured.
Sometimes the emergency may be so pressing that the aircraft has no time to dump or burn fuel in order to achieve its maximum landing weight before touchdown; in that case, a risky overweight landing may be permitted. In other cases, the flight crew may fail to dump fuel when it still had the time to do so before landing, leading to fatal accidents such as Aeroflot Flight 1492 on 5 May 2019, where an apparently needlessly overweight landing turned into a crash that killed 41 of the 78 people on board.
Where aircraft overweight landing is permitted, a structural inspection or evaluation of the touch-down loads before the next aircraft operation will be required in case damage has occurred.
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 | 3,500 | Heavy | Super | |
| Scaled Composites Model 351 Stratolaunch | 589,670 | 3,660 | Heavy | Super | ||
| Airbus A380-800[1][2][3] | 575,000 | 394 | 3,100 | 1,930 | Heavy | Super |
| Boeing 747-8F | 447,700 | 346.091 | 3,100 | 1,800 | Heavy | Heavy |
| Boeing 747-8 | 443,613 | 306.175 | 3,100 | Heavy | Heavy | |
| Boeing 747-400ER | 412,770 | 295.742 | 3,090 | Heavy | Heavy | |
| Antonov An-124-100M | 405,060 | 330 | 2,520 | 900 | Heavy | Heavy |
| Boeing 747-400 | 396,900 | 295.742 | 3,018 | 2,179 | Heavy | Heavy |
| Lockheed C-5 Galaxy[4][5][6] | 381,000 | 288.417 | 2,530 | 1,494 | Heavy | Heavy |
| Boeing 747-200[7] | 377,840 | 285.7 | 3,338 | 2,109 | Heavy | Heavy |
| Boeing 747-300[7] | 377,840 | 260.32 | 3,222 | 1,905 | Heavy | Heavy |
| Airbus A340-500[8] | 371,950 | 240 | 3,050 | 2,010 | Heavy | Heavy |
| Airbus A340-600[8] | 367,400 | 256 | 3,100 | 2,100 | Heavy | Heavy |
| Boeing 777-300ER | 351,800 | 251.29 | 3,100 | Heavy | Heavy | |
| Boeing 777F | 347,800 | 260.816 | 2,830 | Heavy | Heavy | |
| Boeing 777-200LR | 347,450 | 223.168 | 3,000 | Heavy | Heavy | |
| Boeing 747-100[7] | 340,200 | 265.3 | Heavy | Heavy | ||
| Airbus A350-1000 | 308,000 | 233.5 | Heavy | Heavy | ||
| Boeing 777-300 | 299,370 | 237.683 | 3,380 | Heavy | Heavy | |
| Boeing 777-200ER | 297,550 | 213 | 3,380 | 1,550 | Heavy | Heavy |
| Airbus A340-300[8][9] | 276,700 | 190 | 3000 | 1926 | Heavy | Heavy |
| McDonnell Douglas MD-11 | 273,300 | 185 | 2,990 | 1,890 | Heavy | Heavy |
| Airbus A350-900 | 270,000 | 175 | 2,670 | 1,860 | Heavy | Heavy |
| Ilyushin Il-96M | 270,000 | 195.04 | 3,115 | 2,118 | Heavy | Heavy |
| McDonnell Douglas DC-10 | 256,280 | 183 | 2,990 | 1,890 | Heavy | Heavy |
| Boeing 787-9[10] | 254,000 | 192.777 | 2,900 | Heavy | Heavy | |
| Boeing 787-10[10] | 254,000 | 201.849 | Heavy | Heavy | ||
| Airbus A340-200[8][11] | 253,500 | 181 | 2990 | Heavy | Heavy | |
| Airbus A330-900 | 251,000 | 191 | 3,100 | Heavy | Heavy | |
| Ilyushin IL-96-300 | 250,000 | 175 | 2,600 | 1,980 | Heavy | Heavy |
| Airbus A330-300[12][13] | 242,000 | 185 | 2500 | 1750 | Heavy | Heavy |
| Airbus A330-200[12][13] | 242,000 | 180 | 2,220 | 1,750 | Heavy | Heavy |
| Lockheed L-1011-500 | 231,300 | 166.92 | 2,636 | Heavy | Heavy | |
| Boeing 787-8[10] | 228,000 | 172.365 | 3,300 | 1,695 | 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 | 3,414 | Heavy | Heavy | |
| Airbus A300-600R[14] | 192,000 | 140 | 2,385 | 1,555 | Heavy | Heavy |
| Boeing 767-300ER | 187,000 | 136.08 | 2,713 | 1,676 | Heavy | Heavy |
| Concorde | 185,000 | 111.1 | 3,440 | 2,220 | Heavy | Heavy |
| Airbus A300-600[14] | 163,000 | 138 | 2,324 | 1,536 | Heavy | Heavy |
| Boeing 767-300 | 159,000 | 136.078 | 2,713 | 1,676 | Heavy | Heavy |
| Airbus A310-300[14] | 157,000 | 124 | 2,290 | 1,490 | 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 | 1,860 | 1,480 | 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 | 2,550 | 1,750 | Medium | Large |
| Boeing 707-120B[15] | 117,000 | 86.3 | Medium | Large | ||
| Boeing 757-200 | 116,000 | 89.9 | 2,347 | 1,555 | 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 | 2,250 | Medium | Large | |
| Convair 880 | 87,500 | Medium | Large | |||
| Boeing 737-900 | 85,000 | 66.36 | 2,500 | 1,704 | Medium | Large |
| Boeing 737-900ER | 85,000 | 71.35 | 2,804 | 1,829 | Medium | Large |
| Boeing 727-200 Advanced[17] | 84,000 | 70.1 | Medium | Large | ||
| Airbus A321-100[18] | 83,000 | 77.8 | 2,200 | 1,540 | Medium | Large |
| Boeing 737-800 | 79,000 | 65.32 | 2,308 | 1,634 | 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 | 2,165 | 1,520 | Medium | Large |
| de Havilland Comet 4 | 70,700 | Medium | Large | |||
| Boeing 737-700 | 70,000 | 58.06 | 1,921 | 1,415 | Medium | Large |
| Airbus A320-100[18] | 68,000 | 66 | 1,955 | 1,490 | Medium | Large |
| Boeing 737-400 | 68,000 | 54.9 | 2,540 | 1,540 | Medium | Large |
| de Havilland Comet 3 | 68,000 | Medium | Large | |||
| Boeing 377 | 67,000 | Medium | Large | |||
| Boeing 737-600 | 66,000 | 54.66 | 1,796 | 1,340 | Medium | Large |
| Airbus A220-300 | 65,000 | 57.61 | 1,890 | 1,494 | Medium | Large |
| Hawker Siddeley Trident 2E | 65,000 | Medium | Large | |||
| Airbus A319[18] | 64,000 | 62.5 | 1,850 | 1,470 | Medium | Large |
| Boeing 737-300 | 63,000 | 51.7 | 1,939 | 1,396 | Medium | Large |
| Boeing 737-500 | 60,000 | 49.9 | 1,832 | 1,360 | Medium | Large |
| Airbus A220-100 | 59,000 | 50.8 | 1,463 | 1,356 | Medium | Large |
| Airbus A318[18] | 59,000 | 57.5 | 1,375 | 1,340 | Medium | Large |
| Boeing 717-200HGW | 55,000 | 47.174 | 1,950 | Medium | Large | |
| Douglas DC-7 | 55,000 | Medium | Large | |||
| de Havilland Comet 2 | 54,000 | Medium | Large | |||
| Boeing 717-200BGW | 50,000 | 46.265 | 1,950 | 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 | 2,056 | 1,323 | Medium | Large |
| Caravelle III | 46,000 | Medium | Large | |||
| Fokker 100 | 46,000 | 39.95 | 1,621 | 1,350 | 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 | 2,244 | 1,304 | Medium | Large |
| Bombardier CRJ900[21] | 36,500 | 33.345 | 1,778 | 1,596 | Medium | Large |
| Embraer 170[22] | 36,000 | 32.8 | 1,644 | 1,274 | Medium | Large |
| Bombardier CRJ700 | 33,000 | 30.39 | 1,564 | 1,478 | Medium | Large |
| Douglas DC-4 | 33,000 | Medium | Large | |||
| Vickers Viscount 800 | 30,400 | Medium | Large | |||
| Bombardier Q400 | 28,000 | 28.01 | 1,219 | 1,295 | Medium | Large |
| Bombardier CRJ200 | 23,000 | 21.319 | 1,918 | 1,479 | Medium | Large |
| ATR 72-600 | 22,800 | 22.35 | 1,333 | 914 | Medium | Large |
| Saab 2000 | 22,800 | 21.5 | 1,300 | Medium | Large | |
| Embraer ERJ 145 | 22,000 | 19.3 | 2,270 | 1,380 | Medium | Large |
| ATR 42-500 | 18,600 | 18.3 | 1,165 | 1,126 | Medium | Small |
| Saab 340 | 13,150 | 12.930 | 1,300 | 1,030 | Medium | Small |
| Embraer 120 Brasilia | 11,500 | 11.25 | 1,560 | 1,380 | Medium | Small |
| BAe Jetstream 41 | 10,890 | 10.57 | 1,493 | 826 | Medium | Small |
| Learjet 75[23] | 9,752 | 8.709 | 1,353 | 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 | 1,036 | 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 |
Helicopters
MTOW = Maximum take-off weight
| Type | MTOW [pounds] | MTOW [kg] | Power output [kW] | Power to weight [W/kg] | Rotor diameter [m] |
|---|---|---|---|---|---|
| Mil Mi-12[27] | 231,485 | 105,000 | 19,200 | 182 | 2 x 35 |
| Mil Mi-26[28] | 123,459 | 56,000 | 17,000 | 343 | 1 x 32 |
| Sikorsky CH-53K | 88,000 | 39,916 | 16,200 | 405 | 1 x 24 |
| Sikorsky CH-53E[29] | 73,500 | 33,300 | 9,810 | 294 | 1 x 24 |
| Boeing CH-47D/F Chinook[30] | 50,000 | 22,680 | 7,058 | 311 | 2 x 18.3 |
| AgustaWestland AW101[31] | 34,392 | 14,600 | 4,698 | 321 | 1 x 18.59 |
| Sikorsky S-92[32] | 26,500 | 12,020 | 3,758 | 312 | 1 x 17.17 |
| Eurocopter EC225 Super Puma | 24,692 | 11,200 | 3,552 | 317 | 1 x 16.2 |
| Boeing Vertol CH-46 Sea Knight[33] | 24300 | 11,000 | 2,800 | 254 | 2 x 15.24 |
| NHIndustries NH90 | 23,370 | 10,600 | 3,324 | 314 | 1 x 16.3 |
| Eurocopter AS532 Cougar | 19,840 | 9,000 | 2,370 | 263 | 1 x 15.6 |
| Airbus Helicopters H160 | 13,340 | 6,050 | 1,910 | 316 | 1 x 13.4 |
| Bell 412EP | 1,1900 | 5,397 | 1,864 | 345 | 1 x 14.0 |
| Eurocopter EC145 C-2 | 7,903 | 3,585 | 1,100 | 307 | 1 x 11.0 |
| Eurocopter EC135 P2+/T2+ | 6,415 | 2,910 | 944 | 325 | 1 x 10.2 |
| Eurocopter EC635 P2 | 6,393 | 2,900 | 1,218 | 420 | 1 x 10.2 |
| AeroVelo Atlas (human powered) | 282 | 128 | 1.1 | 8.5 | 4 x 20.2 |
Convertiplanes
MTOW = Maximum take-off weight
| Type | MTOW [kg] | Power output [kW] | Power to weight [W/kg] | Rotor diameter [m] |
|---|---|---|---|---|
| Bell Boeing V-22 Osprey | 27,445 | 6,150 | 224 | 2 x 11.58 |
| Bell-Agusta BA609 | 7,600 | 1,447 | 190 | 2 x 7.92 |
| Bell XV-15 | 6,009 | 1,156 | 192 | 2 x 7.62 |
2. Is there any difference between ground speed and air speed?
Answer: Airspeed is the vector difference between the ground speed and the wind speed. On a perfectly still day, the airspeed is equal to the ground speed. But if the wind is blowing in the same direction that the aircraft is moving, the airspeed will be less than the ground speed.
GROUND SPEED:
Ground speed is the horizontal speed of an aircraft relative to the Earth’s surface.[1] It is vital for accurate navigation that the pilot has an estimate of the ground speed that will be achieved during each leg of a flight.
An aircraft diving vertically would have a ground speed of zero. 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, inertial navigation system, or GPS. When more advanced technology is unavailable, an E6B flight computer may be used to calculate ground speed. Ground speed radar can measure it directly.
Ground speed is quite different from airspeed. When an aircraft is airborne the ground speed does not determine when the aircraft will stall, and it doesn't influence the aircraft performance such as rate of climb.
AIR SPEED:
he relationship between airspeed and ground speed is fairly simple. 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.
> To give you an actual 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.
The above is the reason why some flights go “out of their way” to avoid headwinds or catch tailwinds. And, why some flights might appear to be traveling at “supersonic speeds,” even though their airspeed – the speed that would actually matter in determining whether or not the flight truly is supersonic – is subsonic.
>> For pilots, both airspeed and ground speed are very important. While the first of those helps them make sure they are flying fast enough to take off, not to stall, and so on, the second one helps them figure out how long it will take them to get from one place to another.
>> On the other hand, if you are a passenger, you will only need to be concerned about the ground speed as that will tell you how fast are you flying from your origin to your destination – how fast you will be able to get to your meeting, meet your relatives, or do whatever else the reason for your travel might be.
3. Why is it not recommended to use aircraft engine power to move it on the ground at Airport?
Answer : 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 are called the takeoff roll and landing rollout, respectively.
Pilots and airlines rely on aircraft tugs to perform towing and pushback operations for commercial, private and military aircraft with general ease. The traction design incorporated into aircraft towing equipment means safe movement and stops, even on snow and ice. But there are even more reasons why airlines rely on airport tugs. This article will explore why aircraft towing equipment is used so extensively at large and small airports in every corner of the world. Keep reading to learn more.
1. AIRCRAFT ENGINES CAN CREATE HAZARDOUS CONDITIONS
Aircraft towing equipment is typically used for the towing and pushback process to avoid some of the significant hazards posed by aircraft engines. When an aircraft's engine is activated, the thrust can create a high-speed wind that can easily cause damage to the airport terminal, surrounding ground vehicles, jetway, baggage and most importantly, ground personnel.
Suppressing the use of engines is especially important when towing a large aircraft, as their more powerful thrust capabilities can become exceedingly dangerous. Engine thrust can easily send any loose items airborne, turn the tiniest grains of dust into hazardous projectiles and create debris that can cause damage to multi-million dollar engines. Additionally, aircraft engines consume a great deal of fuel and generate extreme noise that can be harmful to ground personnel. Using a pushback tug for aircraft is simply a more economical and safer option than running the engines.
2. AIRCRAFT TOWING IS EASIER FOR MAINTENANCE PURPOSES
Towing and pushback tugs for aircraft are also used to make general maintenance easier for ground personnel. When an aircraft needs to be moved to a hangar for maintenance purposes or is not required for flight, the easiest way is to send an aircraft tug to the tow-in gate for transport. Aircraft towing frees up time for the airline, maintenance team, airport ground controllers and pilots who don't need to waste time getting the engines started. It's also not cost-efficient to start aircraft engines just to reposition an aircraft for maintenance purposes. Typically, ground personnel are trained to only need the aircraft brake system when towing a large aircraft.
3. PILOTS HAVE LIMITED VISIBILITY FROM THE FLIGHT DECK
Pilots do not have a clear view of the rear from the flight deck and thus rely on aircraft towing equipment for ground pushback when needed. Once the aircraft is perfectly positioned and far from the terminal tow-in gate and other vehicles, the airport tug is disconnected and the aircraft can use its engines and steering to move to the runway for takeoff.
4. TERMINAL TOW-IN GATES ARE CONFINED SPACES
Another common reason aircraft towing equipment is used in airports concerns aircraft safety from the taxiway to the tow-in gate. Aircraft towing from the taxiway occurs with significant time constraints, so pilots and ground personnel are under extreme pressure to navigate the aircraft quickly and efficiently. The tight confines of the terminal tow-in gate combined with the restricted view of the pilots generally always require a tow in order to arrive safely and on time.
Even though pilots follow taxi centerlines, aircraft with very large wingspans are often faced with the challenge of having adequate clearance. If an airplane connects with another aircraft or hits a gate terminal, it can cause significant damage, huge expenses and contribute to lost time for extra maintenance repairs.
Aircraft towing can prevent contact with other structures because ground personnel have much better visibility from the airplane tug. With the aid of ground personnel walking with the wings and tail, the airport tug driver can precisely position the aircraft to ensure it will not hit a structure, vehicle, person or another aircraft. In addition to this, the airplane tug driver is in constant communication with the pilots to ensure the aircraft will brake if an emergency occurs.
5. PUSHBACK TUGS FOR AIRCRAFT ARE REQUIRED FOR GOING IN REVERSE
Typically, most aircraft cannot move in reverse without the help of aircraft towing equipment. Planes are not designed with a reverse option that pilots can use for backward movement, so pushback tugs for aircraft are the only option when moving aircraft into hangars or away from the terminal building. This is because aircraft are not outfitted with gears or transmission for propulsion – power for movement is derived solely from the engines through thrust. When aircraft tugs are used to tow planes, an airline can maximize safety and optimize efficiency with on-ground operations.
While most commercial airliners with jet engines have thrust-reversing capabilities, they can only be used as additional braking power during landing. In addition to the problems mentioned above associated with using aircraft engines, reverse thrust also has what is known as the lowest-speed-of-operation limit. If reverse thrust is used below the speed of 80kts, it's very likely the engines will become heavily damaged.
4. How an aircraft is pushed to runway when its ready to take off?
ANSWER:
Sitting in the terminal building waiting to be called for our flight is a regular occurrence for most of us – but what’s really going on out there on the ramp while we’re inside staring at our phones
The jet that will carry you to your destination has likely just arrived from somewhere else. When it lands, it’ll undergo a turnaround, changing from an arriving to a departing flight.
There are vehicles and people on the ramp, ready to get your flight back in the air quickly – after all, a plane doesn’t make money sitting on the ground.
Here are the 10 steps from arrival to take-off:
1. Parking the plane
As soon as a plane lands and clears the active runway, the pilots receive taxi instructions from ground controllers. Large airports can have complex and confusing taxiway layouts, while some airports simply have a runway and a ramp area.
Approaching the terminal, the pilots look for the flight’s assigned gate and watch for the ramp team leader to start waving illuminated, bright orange batons.
There could be a lead-in lighting system to help the pilots line up at the gate, or they might just follow the instructions from the ramp lead.
As the plane slows to a stop, the target for the nose wheel is a painted line on the ramp, matching the type of aircraft. That’ll put the plane in the right spot for the passenger boarding bridge.
2. Hooking up the plane
The plane’s engines provide thrust and electrical power while in flight, but all passenger planes have a small jet engine which generates electricity when the plane is parked – an Auxiliary Power Unit, or APU.
The APU is in the tail cone, and the pilots start it up to feed power to the plane’s systems.
But an APU uses costly fuel from the jet’s tanks, so many airports provide a ground power system, or there’s a generator cart parked at the gate. Once the plane’s access panel is opened and the connection is made with a heavy-duty cable and plug, the source of power is switched, and the engines are shut down.
3. Connecting the air-con
The APU also energizes the plane’s climate control systems, hopefully keeping the cabin at a nice temperature while parked. Like ground power, some airports provide conditioned air through large-diameter flexible ducts that plug into a port on the belly of the plane.
Or you might see a truck-mounted unit doing the job, with a duct snaking to the plane. Large, wide-body aircraft need two air connections to keep the cabin comfortable.
4. De-planing
The passengers inside the plane have jumped up, and they’re waiting impatiently in the aisle to get off – right now.
If the gate is equipped, a passenger boarding bridge is positioned by the forward left-side doors.
Otherwise, truck- or cart-mounted stairs roll up, and passengers experience the excitement of walking down the stairs and onto the ramp, being able to look back at their aircraft.
Smaller regional jets and turboprops sit close to the ground, and have stairs built into the inside of the plane’s doors, with just a couple of steps to the ramp.
5. Unloading the luggage and cargo
On the right side of the plane, the ramp team has swung into action. After opening the doors to the baggage and cargo holds, a belt-loader or a pod-loader is positioned, depending on the aircraft.
“Rampie” is the industry term for airline employees who load and unload planes.
The rampie inside the belly of a single-aisle plane places each piece of luggage onto the belt, and their partner takes it off the belt and puts it into a baggage cart.
The carts head to the baggage room, and the luggage is dropped onto a conveyor, hopefully showing up on a carousel soon after you’ve arrived.
Wide-body planes carrying hundreds of passengers needed an efficient way of handling luggage and cargo, so baggage and cargo pods were developed back when jumbo jets first appeared.
Pods are filled with passengers’ bags, and handled by a purpose-built machine. One rampie can operate it, and make the pods dance on the loader’s platform or in a plane’s holds by activating powered wheels.
6. Stocking up with food
Catering trucks join the crowd outside the plane’s fuselage. Rising on a scissor lift, the truck’s box matches the height of the plane’s galley doors.
The catering crew replaces used galley carts with newly stocked ones, each cart coded for a specific location in the galleys.
To service the double-deck Airbus A380 mega-jet, catering trucks reach way up, to the upper galley doors.
7. Cleaning the toilets
Perhaps it’s not the most desirable ramp job, but somebody’s got to empty the plane’s lavatory holding tanks, and refill the fresh water system. Just like a recreational vehicle, this doesn’t happen during every stop.
Rampies position a truck- or cart-mounted tank and pump unit, and connect hoses to do the work.
8. Refueling
Like your car, a plane’s fuel tanks aren’t necessarily filled at every stop.
An airline’s operations team will have figured out how much fuel is needed for each leg of a plane’s daily routing, and when to refuel.
Big tanker trucks connect to the plane’s fuel system under the wing, or a pumper truck will hook up to a fuel hydrant in the ramp, then to the jet’s tanks, and pump away.
9. Pushback
Pushback is when an aircraft is pushed backwards away from the airport gate by vehicles called tugs or tractors.
Closer to departure, an aircraft tug will park right in front of the nose wheel.
The tug might be directly attached to the plane’s nose gear with a tow bar, or could be a “wheel-lift” tug. These tugs cradle the nose gear, then lift it up before moving the plane. That gives the tug driver control over the plane’s direction during pushback.
New taxi technologies are appearing, like pilot-controlled tugs, and electric motors mounted to the plane’s landing gear. Both promise to save fuel, and reduce airport noise.
10. Boarding and take-off
The crew has finished all the pre-flight preparations, the cabin door is closed, and you’re settled into your seat. Your journey begins with a gentle push, in reverse, and you’re anticipating the adventures to come.
Make sure you wave goodbye to the rampies – they’ve worked hard to get you on your way.
5. Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.
Answer:
Takeoff power:
Road planers, dredges, and other equipment require power from some type of engine to perform their designed function. Without a power take-off, it would be necessary to add a second engine to provide the power required to run hydraulic pumps and other driveline attached equipment.
Adding an additional engine is simply not practical, which makes power take-off (PTO) a valuable element in providing power to secondary functions. To recognize their value requires a better understanding of these systems, their various types, and their diverse applications.
Understanding Power Take-Offs
Power take-offs allow mobile crushing plants, road milling machines, and other vehicles to perform auxiliary functions without needing an additional engine to power them. A PTO is a device (a mechanism) usually seated on the flywheel housing, which transfers power from the driveline (engine) to a secondary application. In most cases, this power transfer applies to a secondary shaft that drives a hydraulic pump, generator, air compressor, pneumatic blower, or vacuum pump.
Selecting the Right PTO
PTO choice is critical to provide sufficient power to the auxiliary equipment without severely limiting the main function of the prime mover. Selection of a power take-off requires specific information relating to the application and the power needs of the secondary or driven component.
Here is a quick list of considerations for PTO selection:
- Torque and horsepower requirements of the driven component
- Intermittent or continuous operation
- Application usage
- Speed requirements of the driven component
- Mounting face dimensions and options
- Space allocation
- Method of PTO engagement
Having these specifications available makes the proper selection of a PTO a simple task.
PTO Torque and Horsepower Requirements
Speed and rotation requirements of a PTO are among the most critical specifications in the list above, with speed being necessary for calculating torque. The torque and horsepower requirements of the driven component are essential for optimal performance.
In most cases, the owner’s manual of the driven component will provide this information, but the calculation of these requirements, if necessary, is relatively straightforward using two basic formulas.
- HP = GPM x PSI ÷ 1714
HP (horsepower) = GPM (pump flow in gallons/minute) x PSI (pump pressure required pounds/inch) ÷ 1714 (conversion factor to yield HHP or hydraulic horsepower). This formula provides the horsepower requirement for the driven component, used in calculating the torque requirement.
- T = HP × 5252 ÷ RPM
T (torque) = HP x 5252 (the rpm rate where both torque and horsepower intersect) ÷ RPM (RPM rate of the drive shaft of the driven component).
Keep in mind that these calculations only apply to PTOs that drives a hydraulic pump. In cases where power take-off is providing power to a different type of drive component, it will require the manufacturer’s specifications of the driven element.
Hydraulic PTO on a wood chipper application " data-image-caption="" data-medium-file="https://wptpower.com/wp-content/uploads/2017/03/Morbark-Hydraulic-PTO-300x225.jpg" data-large-file="https://wptpower.com/wp-content/uploads/2017/03/Morbark-Hydraulic-PTO-1024x768.jpg" data-lazy-loaded="1" />The Different Types and Industrial Applications of PTO Clutches
Though they perform the same general function—transferring power from the primary drive shaft to a secondary drive shaft for a driven component—there are various PTO types available that serve specific industrial applications. These diversifications are why WPT Power supplies OEM’s units in agricultural, energy, forestry, and road building sectors, among others.
Pilotless Mechanical PTO
The distinguishing characteristic of this type of PTO is the intentional removal of the pilot bearing. Benefits of this design feature come with an increased side load capacity, reduced inventory, increased uptime and engine life, and a quicker and easier installation. Industrial applications of the Pilotless Mechanical PTO include:
- Chippers
- Rock crushers
- Irrigation pumps
- Water blasters
- A wide variety of other heavy-duty Road Building & Construction machines
Mechanical PTO
This type of flywheel PTO applies to either inline or sideload uses. It includes a sealed-for-life pilot bearing, utilizing a lever-actuated manual clutch. The benefit of this type of PTO is a straightforward installation which minimizes downtime and maintenance requirements. This type most commonly applies to:
- Engine packages
- Pump jacks
- Barge pumps
- Wood chippers
Type 1 PTO
This is a rugged, high-capacity power take off used in a broad range of industrial functions. Characteristic of this type of PTO are the sheaves between heavy-duty spherical roller bearings designed to utilize their full load potential. This bearing arrangement reduces the damage produced by crankshaft loading. Among the most common applications for the Type 1 PTO are:
- Mud pumps
- Dredges
- Rock Crushers
- Mobile chippers
Type 2 PTO
The design of the Type 2 PTO features a heavy-duty side loading capacity using sizeable spherical roller bearings. Actuation of this PTO can be either hydraulic or pneumatic. It is self-adjusting and removes the need for the pilot bearing inside the engine flywheel. Features include reduced maintenance, less chance of premature failures, and improved engine and bearing life since there is no direct loading to the crankshaft. Common applications for Type 2 PTOs include:
- Road building equipment (milling machines, stabilizers)
- Portable Rock Crushers
- Tub grinders
Type 1 vs. Type 2 PTO Clutches
The difference between these two PTO clutch types is their varied functional designs.
- Type 1 PTOs include 2-4 times the side load capacity of a Type 2 PTO, so they best suit heavier, industrial applications with high impact loading.
- Type 2 PTOs allow for high-capacity loading in a smaller footprint and are best for light-to-medium capacity side loading.
Pilotless Over-the-Shaft PTO
This PTO design eliminates the need for the pilot bearing while providing increased side loading or inline potential. Its engineering accommodates the most demanding requirements of high-loading diesel engines. Features include simple installation, reduced downtime, and improved engine service life. This style of PTO is used on inline applications with its hydraulic and air fittings. They are mounted near the bell housing instead of at the rear of the shaft like type 1 and type 2.
GM Style PTO
The GM Style PTO reduces maintenance time and cost by using sealed main bearings and eliminating the need for the pilot bearing. Designed to mount directly to GM® style engines, these operate without the need for any particular PTO or engine adaptations. Notable features include clutch adjustments using an external ball stud and jam nut adjustment points.
Automotive Style PTO
Also known as “flat-faced” style PTOs, they incorporate similar design characteristics, features, and benefits of the GM style PTO. It is a spring-loaded clutch making it easier to engage and disengage than over the center power take-offs. Typical uses include irrigation units, brush chippers, or other gas or diesel engine applications.
Common Operational PTO Clutch Problems and Solutions
PTOs are relatively simple mechanical units with minimal operational problems, but a few common issues are associated with them, and each has a straightforward solution. Here are some of the most frequently encountered issues:
- The Clutch will not disengage. Slipping and overheating are common causes of these issues and are fixable by disassembling, inspecting, and replacing if necessary.
- Clutch will not stay engaged. Improper adjustment is the most common cause, remedied through adjusting engagement torque.
- PTO is hot. A newly installed PTO will run hot for the first 10-20 hours of operation after installation. Several issues contribute to overheating (220º F measured by infrared thermometer at the bearing carrier), including too much or too little grease, excessive sideload, or a new installation. Follow proper lubrication specifications and reduce the sideload to remedy the first two problems.
Tyre design :
- Bias Tire Technology
- ACOT
- Radial Tire Development
- Revolutionarily Reinforced Radial Tire
- Tire Development and Testing
- Retreading Technology
- Shearographic Inspection
Bias Tire Technology
Among the center's most renowned achievements to date is the development of the Tension Control Optimization Theory (TCOT), a new theory of tire design which allows for the simultaneous improvement of several previously incompatible tire performance characteristics in radial truck and bus tires. Highly successful, this theory influenced the development of ACOT, or Aircraft Tire Tension Control Optimization Theory.
Incorporated into Bridgestone aircraft bias tires, this new theory created a technological revolution in tire design by providing greater overload durability and allowing for greater weight reduction.
ACOT
What would happen, if when designing a bias aircraft tire, one were to move away from the conventional “Natural Equilibrium Shape Theory?” Bridgestone engineers took this question to task, and when the results were in, they discovered that they had created a revolution in tire design.
It was discovered that by changing the shape of the case line, away from the "natural shape," carcass cord tension could be controlled and the tire durability greatly enhanced. The compression of carcass cords is the greatest detrimental factor to overload durability as nylon cord is resilient to tension but weak against compression. By increasing carcass tension in the tire's vulnerable areas, compression is reduced, thereby increasing overload durability performance. This translates into greater safety during long taxi and high speed taxi situations as well as improved performance for double load taxi and takeoff.
ACOT technology creates the possibility to reduce tire weights without sacrificing overload durability, and has given Bridgestone the flexibility to design products which best meet individual aircraft needs, maximizing weight reduction and overload performance to provide the best possible tire. This technology has been incorporated into the Improved Bias tire (IBT) which is approximately seven percent lighter that conventional tires, and the Performance Weight Optimized Tire (PWO) which also uses new cord technology to achieve further weight reduction.
Radial Tire Development
After years of experience working with bias tire technology, Bridgestone engineers have applied their expertise in new areas and have successfully developed high performance radial tires. In service, these radial tires have seen outstanding results, enabling Bridgestone to supply radial tires for many new generation aircrafts. Currently available for the Boeing B777, B747-400ER, B767-400ER MLG tire, B737 NLG tire, the Airbus A320 family, and A330/A340 operators.
Advanced Technology Radial Tire Development: RRR (Revolutionarily Reinforced Radial)
Bridgestone has developed new-generation aircraft tires. In order to provide superior safety and optimum economy, the tires feature a newly developed belt structure, which contains ultrahigh strength cord and provides superior modulus. Bridgestone's new belt structure can restrain tire growth under inflation and rotation, and offer improvements in resisting external damage, in performing reliability even while sustaining external damage, in minimizing tire weight and extending tire life by restraining wear.
For further information on RRR (Revolutionarily Reinforced Radial)
Tire Development and Testing
The quality of Bridgestone aircraft tires can be attributed to the care and attention that goes into each step of their creation.
These tires are subjected to strict original equipment manufacturer's specifications. However, long before a Bridgestone tire is submitted for approval, each tire must first meet the company's own set of design objectives, so that by the time it is finally approved, the tire has undergone rigorous scrutiny.
An essential part of aircraft tire design, Finite Element Method (FEM) technology is utilized to predict tire component stress-strain and heat generation characteristics. The tire structure to be analyzed is divided into finite elements, normally triangular or quadrangular. A stress-strain analysis is conducted on the finite element structure as a substitute for the original. Force-displacement relation for each element is combined into a large set of linear equations for the total structure and these equations are solved using computers. Thus, various tire qualities can be tested through FEM simulations, resulting in the development of better products.
After initial development, a prototype tire undergoes inhouse testing. On Bridgestone's testing menu are a variety of tests that are designed to determine a tire's heat resistance, durability and strength. To simulate the difficult conditions to which an aircraft tire is exposed, Bridgestone utilizes advanced state-of-the-art dynamic testers. This machinery is designed to subject aircraft tires to the entire range of performance requirements; taxiing, takeoff, landing, braking, overload and overspeed conditions. These tests enable Bridgestone engineers to prove our tires at performance levels which exceed everyday operating conditions.
Retreading Technology
At Bridgestone new and retread technologies are developed simultaneously with each technology improving the other and with our engineers having hands-on experience in each field. Being very conscious of airline economy as well as of our environment, we assign R&D the equal attention of our engineers who work with the purpose of designing safe, highly durable and retreadable products.
Like new tire technology, retreading technology continues to advance at Bridgestone where each tire is thoroughly tested upon arrival at Bridgestone using holography and shearography, nondestructive inspection methods which reliably detect minute anomalies and separations within the tire carcass, ensuring the integrity of each and every tire that reenters service. Futhermore, at each manufacturing process stage, careful inspection and implementation of quality control mechanisms ensure the high standard for which our tires are known.
Shearographic Inspection
A reliable nondestructive inspection method, shearography is utilized in bead-to-bead inspections to detect anomalies within the tire and to evaluate tire durability.
Capable of detecting small anomalies, this technology provides increased levels of product quality assurance and allows for more certain interpretation of data. Among the anomalies or defects observable using shearography are: separations, broken cords, porosity and voids and fatigue. With its many applications, shearography is an integral part of assuring Bridgestone aircraft tire quality.
Rolling Resistance
Rolling friction and rolling resistance.
The force that resists the motion of a body rolling on a surface is called the rolling resistance or the rolling friction.
The rolling resistance can be expressed by the generic equation
Fr = c W (1)
where
Fr = rolling resistance or rolling friction (N, lbf)
c = rolling resistance coefficient - dimensionless (coefficient of rolling friction - CRF)
W = m ag
= normal force - or weight - of the body (N, lbf)
m = mass of body (kg, lb)
ag = acceleration of gravity (9.81 m/s2, 32.174 ft/s2)
Note that the rolling resistance coefficient - c - is influenced by different variables like wheel design, rolling surface, wheel dimensions and more.
The rolling resistance can alternatively be expressed as
Fr = cl W / r (2)
where
cl = rolling resistance coefficient - dimension length (coefficient of rolling friction) (mm, in)
r = radius of wheel (mm, in)
Rolling Friction Coefficients
Some typical rolling coefficients:
| Rolling Resistance Coefficient | ||
|---|---|---|
| c | cl (mm) | |
| 0.001 - 0.002 | 0.5 | railroad steel wheels on steel rails |
| 0.001 | bicycle tire on wooden track | |
| 0.002 - 0.005 | low resistance tubeless tires | |
| 0.002 | bicycle tire on concrete | |
| 0.004 | bicycle tire on asphalt road | |
| 0.005 | dirty tram rails | |
| 0.006 - 0.01 | truck tire on asphalt | |
| 0.008 | bicycle tire on rough paved road | |
| 0.01 - 0.015 | ordinary car tires on concrete, new asphalt, cobbles small new | |
| 0.02 | car tires on tar or asphalt | |
| 0.02 | car tires on gravel - rolled new | |
| 0.03 | car tires on cobbles - large worn | |
| 0.04 - 0.08 | car tire on solid sand, gravel loose worn, soil medium hard | |
| 0.2 - 0.4 | car tire on loose sand | |
Rolling Coefficients Cars
The rolling coefficients for air filled tires on dry roads can be estimated
c = 0.005 + (1 / p) (0.01 + 0.0095 (v / 100)2) (3)
where
c = rolling coefficient
p = tire pressure (bar)
v = velocity (km/h)
Example - Wheel Pressure & Rolling Resistance Coefficient
The standard wheel pressure in a Tesla Model 3 is 2.9 bar (42 psi). The rolling friction coefficient at 90 km/h (56 mph) can be calculated from (3) as
c = 0.005 + (1 / (2.9 bar)) (0.01 + 0.0095 ((90 km/h) / 100)2)
= 0.011
Increasing the pressure to 3.5 bar reduces the rolling resitance coefficient to
c = 0.005 + (1 / (3.5 bar)) (0.01 + 0.0095 ((90 km/h) / 100)2)
= 0.010
- or
((0.011 - 0.10) / 0.011) 100% = 9%
- 1 bar = 105 Pa = 14.5 psi
- 1 km/h = 0.6214 mph
Example - The Rolling Resistance of a Car on Asphalt
The rolling resistance for all four wheels in a car with total weight 1500 kg on asphalt with rolling friction coefficient 0.03 can be estimated with the generic equation 1 as
Fr = 0.03 (1500 kg) (9.81 m/s2)
= 441 N
= 0.44 kN
- compare car rolling resistance with car air resistance (drag)
The rolling resistance for one wheel can be calculated as
Fr = 0.03 (1500 kg / 4) (9.81 m/s2)
= 110 N
= 0.11 kN
Tyre pressure :
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.
Airliner wheels are subjected to the daily punishment of multiple takeoffs and landings. Tires are exposed to temperatures below -40°C during cruise. At touchdown, rubber temperatures can momentarily exceed 200°C.
Wheels must handle the most extreme torture in aviation: a maximum weight, high-speed rejected takeoff: A fully loaded aircraft accelerates to takeoff speed, then stops on the remaining runway. Tires withstand extreme heat and stress until the aircraft is safely stopped.
Few aircraft components take more daily abuse than the tire and wheel assembly.
Tire vs Tyre
Readers outside of North America likely prefer the spelling “tyre” when referring to the rubber portion of an aircraft wheel. Please bear with me as I use the spelling common in my neighborhood.
Wheel Construction
Aircraft tires are too rigid to be forced onto a rim like automotive tires. Aircraft wheel hubs come in two parts. The inboard and outboard hubs are bolted together with the tire in the center, then pressurized with nitrogen.
Nitrogen Instead of Air
A gas station air pump is fine for filling car tires, but large airliner tires must be filled with an inert, dry gas. Nitrogen is inexpensive and perfect for the job.
Nitrogen-filled tires reduce the chance of fire or explosion (it’s an FAA regulation). Tire rubber is flammable and wheel brakes reach very high temperatures. A large tire with 200 psi of atmospheric air would provide a lot of oxidizing power to feed a fire. Nitrogen does not support combustion, greatly reducing the risk of a tire fire or explosion.
Other Benefits of Nitrogen
- Dry nitrogen contains no water vapor. The lack of moisture reduces tire pressure variations at temperature extremes (water density varies significantly at different temperatures). With the effects of moisture eliminated, change in tire pressure due to temperature is linear and predictable
- Oxygen and moisture in atmospheric air cause corrosion to aluminum and steel wheels. Dry nitrogen eliminates this problem.
- Air and moisture cause oxidation of a tire’s inner liner. Nitrogen won’t degrade the rubber.
- Due to their larger effective molecular size, nitrogen molecules permeate through tire rubber at a slightly slower rate than oxygen molecules. Using nitrogen may marginally contribute to reductions in tire inflation loss by permeation.
Should we use nitrogen in our automobile tires?
An article from Scientific American suggests that maintaining proper tire inflation weekly is far more important than spending extra money for nitrogen.
Keep your tires balanced, rotated, and at the proper pressure to save fuel and maximize tire life.
Tire Pressure
Large airliners are heavy (right?). A Boeing 767 has a max takeoff weight of over 400,000 pounds. A fully loaded 747-8 weighs nearly a million pounds. All that weight rides on a handful of tires.
Automobile tires are pressurized to around 30-40 psi. If large aircraft tires were filled with 35 psi, they would be flat under the weight.
Large aircraft tire pressures are ridiculously high. A Boeing 767-300 main wheel is inflated to 205 psi. The high pressure supports the tire’s maximum rated load of 51,000 lbs.
Tire Safety Devices
Aircraft wheels incorporate safety devices to protect the aircraft and personnel working nearby.
Fusible (or thermal) Plugs
Fusible plugs protect tires and wheels from exploding if the brakes get too hot. A fusible plug is a small hollow bolt filled with low melting-point metal (like solder used for electronics or plumbing).
In the event a wheel becomes too hot, the soft metal in the plug melts at a predetermined temperature to allow the tire to safely deflate.
Fusible plugs often come into play after heavy braking, as would happen during a high-speed rejected takeoff. After the aircraft stops, the hot brake assemblies continue to heat the wheels until the fuse cores reach their melting temperature and deflate the tires.
Fusible plugs are mounted inside the wheel hub. When the plugs deflate the tire, nitrogen is directed over the brakes to aid in cooling. Pretty clever!
Over Pressure Relief Valve (OPRV)
An over pressure relief valve is a hollow bolt with a rupture disk inside. The disk ruptures when nitrogen pressure exceeds the design limit.
OPRVs are installed on most wheel rims to protect tires from over-pressure or explosion that can occur during nitrogen servicing.
On a Boeing 767, the pressure relief valves release pressure at 375-450 psi.
How important are OPR valves? Over-pressurization accidents have dismembered and killed maintenance personnel. Aircraft tires are so strong that the wheel rim and bolts fail before the tire, launching shrapnel outward. OPR valves reduce this risk. Maintenance technicians receive special training before they can service wheels.
TPMS (Tire Pressure Monitoring System)
Some aircraft models have TPMS sensors in their wheels. The system is very similar to the TPMS in automobiles. Cockpit displays show tire pressures for all tires equipped with the sensors.
The TPMS triggers an alert in the cockpit if a tire has low pressure. The UPS fleet has two fleets with TPMS; the 747 and MD-11.
Brake Temperature Monitoring System
Many large aircraft have brake temperature monitoring systems. The photo below shows the system on a Boeing 767-300F.
Each of the 8 boxes represents a main gear wheel (there are no brakes on the nose wheels). Unlike the MD-11 in the previous photo, the Boeing system doesn’t display actual temperatures. The numbers 0-9 represent temperature ranges.
Temperatures 0-2 are cool to warm. The above photo was taken after landing on a long runway, using light braking.
The Normal temperature range is 3-4. It’s typical to see twos and threes after a normal landing. An occasional four after a heavy weight landing on a hot day is common.
High temperature range is 5-9. When brake temps reach the high range, a BRAKE TEMP warning light illuminates. At 5-6, wheel fuse plugs may melt and deflate the tires. If the brakes reach 7-9, the crew will exit the runway and stop the aircraft. Airport fire fighters are called to monitor the landing gear in case of fire. Tire, wheel, and brake replacement may be required. Temperatures this high are typically caused by an emergency landing or rejected takeoff.
Actual brake temperatures: 5 correlates to 371°C – 427°C depending on the type of brakes installed (steel vs. carbon). That’s smokin’ hot!
Big Airliner Tires Are Big
Like cars and trucks, aircraft tires come in many sizes. Tire size data is molded into the sidewall of every tire. A Boeing 757-200 uses H40x14.5-19 tires on the main landing gear. Decoded, the “H” means high deflection, 40 inch tire diameter, 14.5 inch tire width, and 19 inch wheel/rim diameter.
Main gear tire diameter and width for a few popular airliners:
| Aircraft | Diameter | Width |
| Boeing 737-700, 800, 900 | 44.5″ | 16.5″ |
| Boeing 747-8 | 52″ | 21″ |
| Boeing 767-300 | 46″ | 18″ |
| Boeing 777-300 | 52″ | 21″ |
| Boeing 787-8 | 50″ | 20″ |
| Airbus A320 | 46″ | 17″ |
| Airbus A330 | 54″ | 21″ |
| Airbus A350/A380 | 55″ | 21″ |
| McDonnell Douglas MD-11 | 54″ | 21″ |
| Embraer ERJ 170/175 | 38″ | 13″ |
| Embraer ERJ 190/195 | 41″ | 16″ |
| Canadair CRJ700/900 | 36″ | 12″ |
Big Wheels Are Heavy
747-8 main tires weighs 270 lbs each. A fully assembled -8 wheel with hardware is close to 550 lbs!
A Boeing 757 main tire weighs about 150 lbs. Main tires for an Embraer ERJ190 regional jet are about 145 lbs each.
Tire Chines (or deflectors)
Chines are sometimes found on the nose wheels of aircraft with fuselage mounted engines. The edges of the tire sidewalls have a curved protrusion (chine) that deflects standing water outward to reduce water ingestion into the engines.
The Boeing 727 uses chined nose wheel tires as well as several other aircraft with fuselage mounted engines. I’ve seen them on Embraer RJs and a few business aircraft. See if you can spot them!
Who makes aircraft tires?
You might recognize the names of aircraft tire companies. They also manufacture automobile tires! Goodyear, Michelin, Dunlop, and Bridgestone, to name a few.
Who owns the tires?
Airlines often purchase tires directly from the manufacturer and retain ownership for the life of the tire. When tires are sent back to the factory for retreading, the same tires are returned to the airline that owns them.
There are also tire leasing and tire service contracts available. Each airline makes their own deal with tire distributors and manufacturers.
Retread tires? On aircraft?!
An aircraft tire carcass/casing (tire without the tread) is constructed super-tough. A carcass that is eligible for retread is a desirable asset; it has demonstrated that it can stand up to the abuse of airline operations.
Retreading a tire is less expensive than buying a new one. Some tires can be retread as many as 16 times! Airlines often retread tires less than the manufacturer’s limit as an added measure of safety. Another benefit: retreads have more plies than new tires so they can handle more takeoffs & landings.
Don’t retreads fall apart?
Let’s talk about commercial truck retreads for a moment… Big chunks of disintegrated tires litter the sides of busy highways. Is it fair to blame retread tires for the debris?
NHTSA Truck Tire Study
The U.S. National Highway Traffic Safety Administration published a commercial vehicle tire debris study. Researchers analyzed hundreds of tire debris samples to figure out why the tires failed. The results show that retread and Original Equipment (OE) tires fail at about the same rate.
The majority of truck tire failures (retread or OE) are not caused by problems with manufacturing. The number one cause of tire failure is “road hazard” — potholes, nails, car parts, and other hazards on the roadway.
The study lists the second highest cause of tire failure as “maintenance and operational issues” — overloaded trucks, improper tire inflation, and worn out tires. In other words, operators aren’t taking care of their tires.
Back to Aircraft…
Airport crews check runways for debris and damage regularly (far more often than highway crews). This significantly reduces the “road hazard” risk.
To reduce “maintenance and operational” risk, airlines load aircraft within manufacturer limits. Tire pressures are checked and adjusted religiously, so over/under inflation is not a concern.
Maintenance personnel and flight crews check tire condition before every departure. Technicians change tires when they reach the manufacturer’s wear limit.
All this attention to detail makes aircraft tire failures extremely rare.
Who does the retreading?
Most (if not all) aircraft tire manufacturers have retread plants located world-wide (Bridgestone has 5 retread facilities).
Goodyear retreads bias-type airline tires of any manufacturer. This often creates “Frankenstein tires” with logos of the original manufacturer on the sidewall and the Goodyear logo on the retread. They’re fun to spot when doing a preflight walk-around.
How much do tires cost?
Retail tire prices range from a few hundred dollars for regional aircraft to as much as $5000 for a wide-body main tire. Airlines negotiate purchase prices or service contracts with tire manufacturers and distributors.
Mixing Tire Brands
You would never dream of mixing new Goodyear and Michelin tires on a car. Aircraft tires are all manufactured to the same specifications so it’s common to see two different brands on the same landing gear bogie.
Tread Patterns
Aircraft tire treads have several circumferential grooves molded into the tread that help channel water away from the tire surface. Complex patterns that improve traction on automobile tires are not necessary on aircraft because the wheels rotate freely.
Large aircraft land on straight, well prepared runways. Modern runways are “crowned” — the runway gently slopes away from the centerline — to drain water. To further improve drainage and tire traction, runways often have grooves cut perpendicular to the direction of travel.
Airlines don’t rotate tires. A tire’s lifespan is too short to worry about uneven wear.
Large aircraft wheels are not balanced. Tires take a lot of punishment and each landing leaves rubber on the runway. Keeping them balanced would be a losing battle as every landing changes the weight distribution of the tires.
Tires Have Speed Ratings
Most airliners have tires rated for around 220-235 mph. This is way faster than the aircraft is typically traveling on the runway. Takeoff and landing speeds vary between 140-200 mph so there is a good margin of safety in the event an aircraft needs to land at a high speed (due to emergency or equipment malfunction).
The Great Pre-Spin Debate
Tires take a beating every time they touchdown on the runway. Why not have a mechanism to spin-up the tires prior to landing? If tire speeds match the touchdown ground speed, it would keep tire temperatures lower and save a little rubber… right?
It seems like a good idea. If fact, it’s been studied and tried several times throughout aviation history. So, why aren’t tires pre-spun before landing?
One of the earliest ideas was to place small vanes on the wheel hub to catch the airflow. The wheels would spin like a waterwheel. This concept won’t spin the wheels fast enough to match runway touchdown speed. It also adds extra drag which wastes fuel.
Another proposal uses an electric motor on each wheel to pre-spin before touchdown. This adds considerable weight and complexity to an already complicated system. Weight increases fuel burn and reduces payload capacity. Added complexity costs money for initial installation and on-going maintenance.
Other problems with pre-spin:
- Accurately matching wheel speed to the ground speed of touchdown is complicated (adds complexity and cost).
- Crosswind landings – Landing in a crab is an approved and recommended technique on many airliners. This wears a fair amount of rubber off the tread layer that pre-spinning would not prevent.
- A malfunctioning pre-spin system would cause maintenance delays.
- A fair amount of tire wear occurs during taxi.
Tires are relatively inexpensive and considered normal consumable items (like oil, hydraulic fluid, filters, etc) for aircraft operation. Technicians can replace a tire with little or no delay. A pre-spin system would be costly in the long run.
When are tires changed?
Maintenance techs inspect tires after every landing. The grooves molded in the tread are used as wear indicators. Tires are replaced when the tread is worn to the base of a groove. Cuts, sidewall damage, or bulges may require an early tire change.
If a replacement tire isn’t available, the tire can stay in service, even with the first layer of fabric (cord) visible, until it reaches a maintenance base.
On the family car, that would be crazy. Aircraft tires are very different than automobile tires. Aircraft tires don’t need tread grooves for max performance (similar to a smooth Formula 1 racing tire). They’re designed to meet full performance specs, even with the first layer of reinforcement fabric showing.
If you see a tire that looks bald on an aircraft, don’t freak out. Tires are inspected after every flight. They are replaced when they reach the manufacturer’s service limit.
How many takeoffs & landings?
Tire change cycles vary based on runway conditions, weather, and aircraft operating weights. A rough average is about 100 cycles for a main tire on a large aircraft (one takeoff and landing = one cycle). Nose wheel tires last a few more cycles than main tires.
Are tires changed in sets?
Main landing gear and nose tires on large aircraft are usually changed only when they reach wear limits. It’s common to see new and old tires next to each other. Certain types of wear or damage will require tires to be changed in sets.
There are always exceptions. On some aircraft types, technicians change nose wheel pairs together.
How to Change a Tire
Tire changes are actually wheel changes. The whole wheel is removed and replaced, just like changing a flat tire on a car. Wheel changes can be accomplished quickly, often without delaying the next departure.
767 Main Wheel Change
During a 50 minute turn-around, our maintenance technician identified a tire that reached its service limit. The tread layer was worn through to the first layer of fabric. Remember, this is not an automobile tire. Aircraft tires are designed to be flown until the tread grooves are gone. Again, they can be safely flown with fabric showing in order to reach a maintenance base.
Remove the Old Wheel
The worn tire is first deflated for safety. In the photo, a hose can be seen connecting the wheel to a pneumatic jack. The 200 psi of nitrogen in the tire can be used to raise the jack. Might as well put all that pressure to work!
Our replacement wheel assembly with a new Goodyear Flight Leader tire is standing by. The 767-300F uses an H46X18.0-20 tire for the main landing gear. It’s a Big Wheel.
The tire load rating for our main tires is 51,100 lbs (it’s stamped on the tire sidewall). The 767-300F has 8 main wheels. 51,100 x 8 = 408,800 lbs. Our maximum takeoff weight is 408,000 lbs. It’s fun to see how the math works out.
After raising the gear bogie with the jack, the technician removes safety wire and a bolt, then spins off a large axle nut. The old wheel assembly is pulled onto a dolly and moved out of the way.
Installing the New Wheel
The new wheel assembly is moved into position with the dolly. The photos below show the brake assembly: a sandwich of brake rotors and stators along with hydraulic actuating pistons that compress the brake sandwich. Brake rotors are keyed to the inside of the wheel and rotate with the wheel; stators don’t move. Rotors are positioned precisely before the wheel is pushed into place over the brake assembly.
-
Wheel moved into position near the brake assembly -
Wheel slides over the brakes
After securing the new wheel, technicians lower and remove the pneumatic jack. Tire pressure is checked and topped off with nitrogen if necessary. Here’s the truly amazing thing: from start to finish, this wheel change took less than 20 minutes. I can’t find my car’s spare tire that fast!
Portable compressed nitrogen cylinder used to pressurize tires to 200 psi. Cylinder is charged to about 1500 psi. A regulator steps down the pressure to safely pump up the tire.
Airplanes rely on a braking system to safely land on runways. At cruising altitude, most commercial airplanes fly at a speed of roughly 500 to 600 mph. When landing, however, they must reduce their speed. A typical 747, for instance, has a landing speed of about 160 to 170 mph. And upon touching the runway, airplanes must quickly brake until they come to a complete stop. How do airplanes brake when landing exactly?
Wing Spoilers
Many airplanes use wing spoilers to assist with braking when landing. Not to be confused with ailerons, spoilers are extendable flaps on the ends of an airplane’s wings. Pilots can raise the spoilers to decelerate the airplane as it approaches the runway. And even while on the runway, pilots will typically leave the wing spoilers raised. Raised wing spoilers create drag, which essentially slows down the airplane so that it’s able to brake more quickly.
Disc Brakes
In addition to wing spoilers, airplanes use disc brakes. Airplane disc brakes are similar to the braking system in automobiles. They consist of a pair of calipers that, when engaged, squeeze pads against the rotors of an airplane’s landing gear.
Disc brakes are designed to remain static at all times. In other words, they don’t rotate with the wheels of an airplane’s landing gear. As the wheels turn, the disc brakes will remain static and stationary. They are a vital component of an airplane’s braking system because they are designed to apply pressure to the airplane’s wheels. Disc brakes will squeeze the wheels, thereby slowing down the speed at which they spin. In turn, this reduces the speed of the airplane so that it can come to a complete stop on the runway.
Reverse Thrust
Finally, many jet airplanes use reverse thrust to assist with braking during landings. Reverse thrust is a feature in jet engine airplanes that, as the name suggests, involves the reversal of the engines’ thrust. When flying, the thrust is projected out the rear of an airplane’s engines. When landing, however, pilots may use the reverse thrust feature. Reverse thrust changes the direction of the engines’ thrust. Rather than projecting out the rear, the thrust will be projected out the front. This reversal of thrust provides deceleration that allows airplanes to slow down more quickly when landing.
Brake forces
We will use Newton’s second law to determine force due to deceleration:
That is Energy required to break Bf = (½)*m*(Vi– Vf)^2
Where,
- Bf = Breaking Energy in Joules
- m = Mass of the aircraft
- Vi = Initial speed of the plane
- Vf = Final speed of the plane
If we want to find the Breaking Power in wattage as we know Power in Watt = Workdone /time
So in order to power in wattage, we have to divide Breaking Energy by time.
- Power = Breaking Energy/time
Here, time is nothing but the time required to reach aircraft from Initial velocity to Final velocity.
Part B:
6. A. With necessary assumptions, calculate the force and power required to push / pull an aircraft by a towing vehicle.
Answer:
The forces required to push/ pull an aircraft by a towing vehicle are given as follows:
• Rolling Resistance Force: As discussed earlier, it is the force which is responsible for resisting the motion of the
body such as ball, tire or wheel, when its starts to roll on the surface. The governing equation of this force is
given by:
F= C *m*g.
where, C- Rolling Resistance Co-efficient (dimensionless)
m- mass of the body under consideration
g- acceleration due to gravity.
Aerodynamic Drag Force; Drag is the aerodynamic force which opposes the motion of the body. It is actually the resistance offered by the air to the movement of the body. So when a car is moving it is actually displaces
the air which in turn affects the car's speed and its performance. Manufacturers always try to keep the Aerodynamic Drag to the minimum possible value. It is due to the fact that this force has a negative impact on the vehicle's performance and the efficiency. The upright stance of some vehicles gives it a drag co-efficient of 1.30 while a randrop design has the least amount of drag. The governing equation of these force is given as follows:
where,
A - It is the reference area (frontal area of the car)
v- It is the velocity/flow velocity relative to the object (speed of the car)
ρ- Air Density
C- It is the Drag Coefficient which is dimensionless related to the object's geometry and take into account both skin friction and form drag.
Taking the values of towing vehicle TUG GT-35 the specifications are,
Maximum Weight(OR) Gross Weight = 18143kg;
Length = 4.724 m;
Width = 2.260 m;
Frontal area A = Height × Width = 4.724 X 2.260 = 10.67 m^2
Tyre size R = 22.5" = 0.5715m
Drag coefficient Cd = 0.6
Air density p = 1.225kg/m^2
Coefficient of rolling resistance ur = 0.028
Speed v = 12kmph = 12x5/18 = 3.33m/s
Now calculating the forces which are acting in the push or pull of an aircraft by a towing vehicle,
Forces are,
Rolling resistance force = Frr
Airdrag force = Fad
Formulas using:
Frr = urr × m × g
Where m = mass of the body
ur = Coefficient of rolling resistance
g = Gravitation = 9.8 m^2
Fad =1/2x pxAxCdxv^2
p = Air density
A = Frontal area
Cd = Drag coefficient
V = Speed.
Now the calculations are,
Rolling resistance force calculations
Frr=0.028 x 18143 x 9.8
Frr= 4978.43N
Air drag force of a towing vehicle
Fad = 1/2 x p * A * Cd x V^2
Fad=1/2 x 1.225 x 10.67 x 0.6 x 3.33^2
| Fad=43.4827N |
Total Forces acting Ft = Frr + Fad
Ft = 4978.43 +43.48
Ft = 5021.91N
Here we are neglected Hill climbing force and acceleration force.
Total Power Pt = Ft x V
Pt = 5021.91 x 3.33
Pt = 16722.96 W
Pt = 16.722 KW.
Now we calculate the below values,
Total force required to push / pull an aircraft by a towing vehicle = 5021.91 N.
Total power required to push / pull an aircraft by a towing vehicle = 16.722 KW.
B. Develop the model for the calculated force and power using Simulink.
Now we have to create a simulink model for the above calculated force and power, In a simulink model first i have created sunsystems for both Rolling resistance force and Airdrag force, and connected them to a addition block to calculate the Total force. And take a connection from the output of addition block connected it to the product block and speed is also connected to product block. From the output of product block we calculated the power.
Calculations are taken according to the formulas. And display blocks are taken to display the values.
The following figure shows the simulink model to calculate force and power.
Final model :
So now from the above Simulink model, by opening the subsystem of rolling resistance force we can see the following connections. Where the rolling resistance force is calculated for both aircraft and towing vehicle and given their outputs to the addition block to calculatate the total Rolling resistance force. And taken a display block to show the value. And taken a output port of subsystem across the output of addition block.
1 : Rolling resistance force of aircarft Frr
- Aerodynamic Drag Calculation
- Power Calculation
-------------------------------------------------------------------------------------------------------------------------------
7. A. Design an electric powertrain with type of motor, it’s power rating, and energy requirement to fulfill aircraft towing application in Simulink. Estimate the duty cycle range to control the aircraft speed from zero to highest. Make all required assumptions. Prepare a table of assumed parameters. Draw a block diagram of powertrain.
(Hint :DC7 Block)
Answer:
Based on the calculations done in 6A.
Force required to push/pull the aircraftby a towing vehicle =5021.91 N
Power required =16.722 Kw
Let us assume some other required parameters,
The Radius of the Tyre for the towing vehicle = 22.5 inches = 0.5715 m
Gear ratio = 3
Transmission Efficiency (ηt) = 85%
Motor Efficiency (ηm) = 91%
Torque required for the wheels (Tw)=Total Force *Radius in meters
=5.021*0.5715
= 2.86KNm
Motor Torque= Wheel torque/(Gear ratio*ηt)
= 2.86 / (3*0.85)
= 0.402KNm
For ηm =95%, The required motor Torque (Tm)= 0.402/0.95 =0.423 kNm
Similarly, The total power required by the motor considering all the efficiencies(Pt) = 16.722/(0.85*0.91)=21.655Kw
Let us assume the towing operation was done for a 15 minutes (0.25Hrs) duration.
Then, Total Energy consumed = 21.655*0.25 = 5.41 KWh
If we consider the battery capacity =150 kw is used by the towing vehicle then, The duty cycle range to control the speed from 0 to max speed (3m/s) is given as
Duty Cycle (d) = (Required Power)/ (Rated power)= 5.41/150 =0.03
Therefore the controller will be able to provide a duty cycle ranging from 0 to 75% in order to control the towing speed.
Simulink Diagram of powertrain:-
Simulink Diagram of powertrain:-
Inputs:-
Scope_1: Signal builder
Scope_2 : Battery
Output:-
Scope_3: DC Drive output
B. Also, Design the parameters in excel sheet.
| PARAMETERS | VALUES |
| Mass of Towing Vehicle 'truck' (Kg)' | 18143 |
| Total mass(Kg) | 18143 |
| Length of the Towing Vehicle(m) | 4.724 |
| Height of the Towing Vehicle(m) | 2.26 |
| Frontal Area of the aircraft A(m^2) | 10.67^2 |
| Coefficient of Rolling Resistances(Crr) | 0.028 |
| Speed of the Vehicle(Kmph) | 12 |
| Speed of the Vehicle(mps) | 3.33 |
| Coefficient of Drag (Cd) | 1.225 |
| Air density 'p'(Kg/m^3) | 0.6 |
| gravitational constant 'g'(Nm) | 9.8 |
| The Radius of the Tyre for the towing vehicle(inches) | 22.5 |
| The Radius of the Tyre for the towing vehicle(m) | 0.5715 |
| Gear Ratio | 3 |
| Transmission Efficiency | 85% |
| Motor Efficiency | 91% |
| towing operation Time(min) | 15 |
| towing operation Time(hours) | 0.25 |
| Rolling Resistances Force 'Frr'(N) | 4978.43N |
| Aerodynamic Drag Force 'Fd'(N) | 43.4827N |
| Total Force 'F'(N) | 5021.91N |
| Total Power 'P'(KW) | 16.722KW |
| Total Energy 'E'(Kwh) | 5.41 |
| Motor Torque 'Tm'(Nm) | 0.423 |
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