Project-1: Powertrain for aircraft in runways

AIM:

1. To list out the total weight of various types of aircrafts.
2. To study the difference between ground speed and air speed.
3. To explain how it is not recommended to use aircraft engine power to move it on the ground at the Airport.
4. To study how an aircraft is pushed to the runway when it's ready to take off.
5. To learn about take-off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.
6. To calculate the force and power required to push/pull an aircraft by a towing vehicle With necessary assumptions.
7. To design an electric powertrain with the type of motor, it’s power rating, and energy requirement to fulfill aircraft towing application and to draw a block diagram of the powertrain.

OBJECTIVE:

• Listing out the total weight of various types of aircraft.
• Study the difference between ground speed and airspeed.
• To explain how it is not recommended to use aircraft engine power to move it on the ground at the Airport.
• Analyze how an aircraft is pushed to the runway when it's ready to take off.
• To learn about take-off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.
• Calculating the force and power required to push/pull an aircraft by a towing vehicle With necessary assumptions.
• Design an electric powertrain with the type of motor, it’s power rating, and energy requirement to fulfill aircraft towing application and to draw a block diagram of the powertrain.

KEYWORDS: Aircraft, ground speed, airspeed, aircraft engine power, rolling resistance, force, power rating, electric powertrain.

STUDY-1:

The different terms represent different weights or masses. For each flight, the weights are taken into account for several reasons.

A brief description of these is below:

Manufacture's empty weight(MEW):

Also called Manufacturer's Weight Empty (MWE) or Licensed Empty Weight

It is the weight of the aircraft "as-built" and includes the weight of the structure, power plant, furnishings, installations, systems, and other equipment that are considered an integral part of an aircraft.

This excludes any baggage, passengers, or usable fuel.

Zero-fuel weight (ZFW):

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

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

Maximum zero fuel weight (MZFW):

In this system maximum weight allowed before usable fuel and other specified usable agents (engine injection fluid, and other consumable propulsion agents) are loaded.

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.

Maximum Zero Fuel Weight (MZFW) DOW + Payload (anything put on the aircraft that generates revenue to the company, e.g. passenger, baggage, cargo, mail and fret)

Operating empty weight(OEW):

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

Payload:

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

Maximum takeoff weight(MTOW):

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

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 Takeoff Weight (MTOW) MZFW + Takeoff fuel, or MTW - Taxi fuel

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 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 Taxi Weight (MTW) MZFW + Ramp fuel

Regulated takeoff weight(RTOW):

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

Maximum landing weight(MLW):

This maximum weight at which an aircraft is permitted to land. The maximum weight authorised for normal landing of an aircraft.

The MLW must not exceed the MTOW.

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

• Aircraft performance requirements for a given altitude and temperature:

landing field length requirements, approach and landing climb requirements

• Noise requirements

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

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

Maximum Landing Weight (MLW) MTOW - Trip Fuel

The following image depicts takeoff weight components.

Aircraft gross weight:

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

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

​The total weight of various types of aircraft are shown in the table given below,

Type	MTOW [kg]	MLW [tons]	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[14]	192,000	140	2385	1555	Heavy	Heavy
Boeing 767-300ER	187,000	136.08	2713	1676	Heavy	Heavy
Concorde	185,000	111.1	3440	2220	Heavy	Heavy
Airbus A300-600	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[18]	59,000	57.5	1375	1340	Medium	Large
Boeing 717-200HGW	55,000	47.174	1950		Medium	Large
Douglas DC-7	55,000				Medium	Large
de Havilland Comet 2	54,000				Medium	Large
Boeing 717-200BGW	50,000	46.265	1950		Medium	Large
de Havilland Comet 1	50,000				Medium	Large
Douglas DC-6A	48,600				Medium	Large
Douglas DC-6B	48,500				Medium	Large
Embraer 190	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

STUDY-2:

Ground Speed:

Ground speed is the horizontal speed of an aircraft relative to the ground. An aircraft heading vertically would have a ground speed of zero. The information displayed to passengers through the entertainment system of airline aircraft often gives the aircraft ground speed rather than airspeed. For a reference point picked on the ground, the aircraft moves relative to the reference point at the ground speed. Ground speed is also a vector quantity so a comparison of the ground speed to the wind speed must be done according to rules for vector comparisons.

Airspeed:

The important quantity in the generation of lift is the relative velocity between the object and the air, which is called the airspeed. Airspeed cannot be directly measured from a ground position but must be computed from the ground speed and the wind speed. Airspeed is the vector difference between ground speed and wind speed.

Airspeed = Ground Speed - 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.

Wind speed:

For a reference point picked on the ground, the air moves relative to the reference point at the wind speed. Notice that the wind speed is a vector quantity and has both a magnitude and a direction. The direction is important. A 20 mph wind from the west is different from a 20 mph wind from the east. The wind has components in all three primary directions (north-south, east-west, and up-down). In this figure, we are considering only velocities along the aircraft's flight path. Positive velocity is defined to be in the direction of the aircraft's motion. We are neglecting crosswinds, which occur perpendicular to the flight path but parallel to the ground, and updrafts and downdrafts, which occur perpendicular to the ground.

Difference Between ground speed and airspeed:

As mentioned above, true airspeed is simply the speed at which an aircraft is moving relative to the air it is flying in. As such, it’s also the speed at which the air is flowing around the aircraft’s wings.

Ground speed, on the other hand, is the aircraft’s speed relative to the ground. One thing that should be noted here is that it’s its horizontal rather than vertical speed – an aircraft climbing completely vertically would have a ground speed of zero.

In other words, while airspeed is what determines whether there is enough airflow around an aircraft to make it fly, ground speed is what determines how fast an aircraft will get to its destination.

STUDY-3:

Aircraft move using their own engine power all the time on the airport apron and taxiways under their own power to go towards runways and after landing taxi to their assigned gate. The only time they use external assistance is to pushback from the gate. Large turbofan aircraft need help to reverse via a pushback tractor. The engines are turned on after the pushback is complete and the aircraft can move forward under Its own power. To be accurate, some aircraft can reverse using a variable pitch prop or thrust reversing on turbofans but generally reversing is done via pushback tractors. Blasting jet reversers blows debris In the crowded gate area creating foreign object damage hazard for adjacent aircraft, gate equipment, or terminal waiting area glass windows.

The disadvantages of using aircraft engine power to move it on the ground at Airport is given below,

• Fuel consumption.
• Wear and tear on the engine.
• Unnecessary jet blast and noise.

Taxing:

Taxing (rarely spelled taxying) is the movement of an aircraft on the ground, under its own power, in contrast to towing or push-back 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 "taxing" 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.

Aircraft are not always moved with tugs (the small vehicle you refer to). Much of the time, they operate under their own power. Airliners are generally pushed back from the gate using a tug, as that's the simplest and most efficient method. They then taxi to the runway (and all the way up to the gate, after landing) using their own engines to provide thrust. This is true of both jets and propeller aircraft.

Some work is being done on self-contained electric-powered ground propulsion one major player in this area is a company called WheelTug. They use high-torque motors and the aircraft APU to allow the aircraft to move itself without starting its engines or requiring a tug to be connected and disconnected.

STUDY-4:

Pushback:

Pushback is when an aircraft is pushed backward 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.

Phases of take-off flight
The take-off flight is generally divided into two phases namely

1. Take-off ground run
2. Transition and climb phases

(i) Take-off ground run

Take-off ground run During the ground run the airplane starts from rest and accelerates to the take-off speed (VT0 or V1). The flaps and engine(s) are adjusted for their take-off settings. In the case of an airplane with a tricycle type of landing gear, all three wheels remain in contact with the ground till a speed of about 85% of the VT0 is reached. This speed is called ‘Nose wheel lift-off speed’. At this speed, the pilot pulls the stick back and increases the angle of attack of the airplane so as to attain a lift coefficient corresponding to take-off (CLT0). At this stage, the nose wheel is off the ground and the speed of the airplane continues to increase. As the speed exceeds the take-off speed the airplane gets airborne and the main landing gear wheels also leave the ground. When the airplane has a tailwheel type of landing gear, the angle of attack is high at the beginning of the take-off run. However, the tail wheel is lifted off the ground as soon as some speed is gained and the deflection of the elevator can rotate the airplane about the main wheels. This action reduces the angle of attack and consequently the drag of the airplane during most of the ground run. As the take-off speed is approached the tail wheel is lowered to get the incidence corresponding to CLT0. When VT0 is exceeded, the airplane gets airborne. The point at which all the wheels have left the ground is called ‘Unstick point’.

(ii) Transition and climb phases

During the transition phase, the airplane moves along a curved path and the pilot tries to attain a steady climb. As soon as the airplane attains an altitude equal to the screen height, the take-off flight is complete. For airplanes with a high thrust to weight ratio, the screen height may be attained during the transition phase itself.

Phases of take-off flight

STUDY-5:

(a) Take off power

For light aircraft, usually, full power is used during takeoff. Large transport category (airliner) aircraft may use a reduced power for takeoff, where less than full power is applied in order to prolong engine life, reduce maintenance costs and reduce noise emissions. In some emergency cases, the power used can then be increased to increase the aircraft's performance. Before takeoff, the engines, particularly piston engines, are routinely run up at high power to check for engine-related problems. The aircraft is permitted to accelerate to rotation speed (often referred to as V_r). The term rotation is used because the aircraft pivots around the axis of its main landing gear while still on the ground, usually because of gentle manipulation of the flight controls to make or facilitate this change in aircraft attitude.

(b) Tyre design

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

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

Based on the type of plies used the tyres can be:

• Radial ply tires - these tyres feature a flexible casing which is constructed of rubber-coated ply cords which extend around the beads and are substantially at 90° to the centerline of the tread. The casing is stabilized by an essentially inextensible circumferential belt.

• Bias-ply tires - these tyres feature a casing which is constructed of alternate layers of rubber-coated ply cords which extend around the beads and are at alternate angles substantially less than 90° to the center line of the tread.

Based on the method for containing the inflation gas the tyres can be:

• Tube-type tyres - these require tubes for inflation retention.
• Tubeless tyres - these do not require tubes. They are constructed with an inner liner (integral rubber lining that is engineered to prevent the diffusion of the inflation gas into the casing.)

Aircraft tires may be tube-type or tubeless. They support the weight of the aircraft while it is on the ground and provide the necessary traction for braking and stopping. The tires also help absorb the shock of landing and cushion the roughness of takeoff, rollout, and taxi operations. Aircraft tires must be carefully maintained to perform as required. They accept a variety of static and dynamic stresses and must do so dependably in a wide range of operating conditions.

(c) Rolling Resistance And Measurement of Rolling friction:

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 measurement of the rolling friction was accomplished by recording the pull between a towing vehicle and a loaded trailer equipped with the wheel and tires to be tested. The resistance thus measured included, of course, that due to the wheel bearings as well as that of the tires.
The tires and wheels tested included two sizes of each of the types generally classified as standard high pressure, low pressure, and extra-low pressure. The tests were run at various speeds under several conditions of wheel loading and tire inflation pressure. The ground surface conditions investigated were concrete, firm turf, and soft turf.
As an indication of the probable effect on the take-off of the differences in rolling friction occasioned by the various conditions, calculations were made of the distance required to leave the ground for two hypothetical airplanes of different loading characteristics for each case several values of rolling-friction coefficient, covering the range determined by the tests.

Rolling Resistance Coefficient:

The coefficient of rolling friction is the indication of how great the rolling resistance is for a given normal force between the wheel and the surface upon which it is rolling. This ratio is based on the Standard Friction Equation.

The Standard Friction Equation is,

F_r = μ_rN

Dividing by N, you can get the equation for the coefficient of rolling friction,

μ_r = F_r/N

where,

• μ_r is the coefficient of rolling friction for the two surfaces (Greek letter "mu" sub r)
• F_r is the resistive force of rolling friction
• N is the normal or perpendicular force of the wheel on a surface

(d) Tyre Pressure

Aircraft tires operate at such high extremes of pressure, load, and speed, their care and service are critically important. The most important action an operator can take to prevent tire-related events is to maintain proper tire inflation pressure. Failure to keep aircraft tires properly inflated can lead to very serious consequences. The most serious of these is the structural failure of the tire. If the tire operates under-inflated or over deflected/overloaded, the nylon cords which form the structure of the tire go in and out of compression as the tire rotates. This weakens the cords – much like a paperclip which is bent back and forth – until eventually, the cords break. If enough cords break, the entire structure will eventually fail.

Another serious consequence of under-inflation is the thrown tread. Overdeflection increases shear between components in the tire as it rolls in and out of contact and deforms. This results in a more rapid build‐up of heat within the tire than would be evident if the tire were properly inflated. At some point, the excessive heat will cause the rubber to revert, or reverse cure. This reverted rubber is like grease with no strength or adhesion to contain the structure. This can allow the tire to decompose, throwing the entire tread or pieces of it. In addition to destroying the tire, thrown treads often result in expensive aircraft damage.

Rated conditions in Aircraft tyre

Aircraft tires are designed and tested to “rated” conditions. These rated conditions are specified by industry standard’s bodies like The Tire and Rim Association (T&RA) and The European Tyre and Rim Technical Organisation (ETRTO). However, most aircraft are not operated at the rated limits. This means that an operator must consult the aircraft’s Aircraft Maintenance Manual (AMM) or Pilot Operating Handbook (POH) to find out the recommended operating pressure range.

To check the pressure every day

Because of the high pressures and extreme temperatures at which aircraft tires operate, they do not hold air perfectly. In fact, an aircraft tire can lose up to 5 percent of its pressure in 24 hours and still be perfectly serviceable. It’s important to check tire pressures when they are cold if at all possible. Michelin recommends checking a tire’s pressure no sooner than three hours after it has last rolled. Tires that have rolled under load recently heat up, making it very difficult to determine what the proper pressure should be.

(e) Braking System:

In the typical brake system, mechanical and/or hydraulic linkages to the rudder pedals allow the pilot to control the brakes. Pushing on the top of the right rudder pedal activates the brake on the right main wheel(s) and pushing on the top of the left rudder pedal operates the brake on the left main wheel(s). The basic operation of brakes involves converting the kinetic energy of motion into heat energy through the creation of friction. A great amount of heat is developed and forces on the brake system components are demanding. Proper adjustment, inspection, and maintenance of the brakes are essential for effective operation.

Types and construction of aircraft brakes:

Modern aircraft typically use disc brakes. The disc rotates with the turning wheel assembly while a stationary caliper resists the rotation by causing friction against the disc when the brakes are applied. The size, weight, and landing speed of the aircraft influence the design and complexity of the disc brake system. Single, dual, and multiple disc brakes are common types of brakes. Segmented rotor brakes are used on large aircraft. Expander tube brakes are found on older large aircraft. The use of carbon discs is increasing in the modern aviation fleet.

Braking forces when landing:

First, some requirement assumptions . . .

Landing weight = takeoff weight in case of aborted takeoff = 1500 lbf

Landing distance = 500 ft

Speed (assume aborted takeoff) = 60 kt (100 ft/sec)

We will use Newton’s second law to determine force due to deceleration:

Deceleration: from simple kinematics, acceleration = velocity^2 / distance

= (100 ft/s)^2 / 500 ft = 20 ft / s^2

Mass of aircraft = (weight) / g = 1500/32.2 = 46.58 lbf*s^2 / ft

Force = mass * acceleration (46.58 lbf*s^2/ft) * (20 ft / s^2) = 931.6 lbf

So in this example, the braking (deceleration) force is 931.6 lbf

STUDY-6:

Calculating the force and power required to push/pull an aircraft by a towing vehicle With necessary assumptions

In this study, we want to calculate the force and power required to push and pull an aircraft by towing vehicle so we take one of the towing vehicle model and airbus model on the website and consider the data for our calculation.

DOUGLAS TOWBARLESS AIRCRAFT TRACTOR: Model: TBL 280Mk4

The Douglas Tugmaster type TBL- 280 Mk4 towbarless aircraft handling tractor has been designed primarily for pushback, inter-gate towing, and longer distance maintenance towing operations at higher speeds with the following aircraft:
Embraer: ERJ 190/195
McDonnell Douglas: DC9/MD80/MD90
Boeing: B717, B737, B727, B757, B767, B787, and B777.
Airbus: A318/A319/A320/A321, A310/A300, A330 and A340-200/300
Boeing: DC10/MD11
Lockheed: L 1011

Gross weight = 35,000 kg

Width = 3400 mm = 3.4 m

Height = 4400 mm = 4.4 m

Length (excluding coupler) = 8470 mm = 8.47 m

Tyre size = R 22.5 = 571.5 mm

= 0.5715 m

Maximum vehicle speed = 32 kmph

= (32*5/18)

Velocity of the tug = 8.89 m/s

The coefficient of friction depends on the objects that are causing friction. The value is usually between 0 and 1 but can be greater than 1. A value of 0 means there is no friction at all between the objects. A value of 1 means the frictional force is equal to the normal force. It is a misconception that the coefficient of friction is limited to values between zero and one. A coefficient of friction that is more than one just means that the frictional force is stronger than the normal force.

Coefficient of rolling resistance (μrr) = 0.02 (Truck tyre in asphalt concrete road)

AIRCRAFT MODEL:

We are taking an aircraft model as Airbus A310 as considered as pushback operation. The advanced technologies of A310 and some specifications are given below,

The A310 helped pioneer the use of composites in commercial jetliners, with its vertical stabiliser built with carbon-fibre materials that offer significant weight savings over conventional metallic structures. Other major applications of composites on the A310 include floor struts and panels, spoilers and main landing gear doors.

Standard or Higher gross weight = 164000 kg

Height = 15.80 m

Width = 43.90 m

Drag coefficient (Cd)= 0.0265

To find:

The Total Force and Power required to push/pull an aircraft by the towing vehicle.

Formula used:

Total force = Fte = Frr+Fad

Rolling resistance force = Frr= μrr⋅m⋅g

Drag force = Fad = 0.5⋅ρ⋅A⋅Cd⋅v^2

Solution:

Total force = Fte = Frr+Fad

In the first step, we want to find the rolling resistance force and air drag force for both towing vehicle and airbus to obtain the force and power value during the towing process,

To find rolling resistance force

Rolling resistance force = Frr= μrr⋅m⋅g

Here mass (m) = mass of the towing vehicle+mass of the airbus

(m) = 35000+164000

m = 199000kg

Substitute mass (m) value in rolling resistance formula

Rolling resistance force = Frr = 0.02 * 199000 * 9.81

Frr = 39043.8 N

To find the air drag force

Drag force = Fad = 0.5⋅ρ⋅A⋅Cd⋅v^2

According to the International Standard Atmosphere (ISA) values = 1.225 kg/m^3.

ρ = 1.225 kg/m^3

Frontal area A = Height of the airbus * Width of the airbus

A = 15.80 * 43.90 = 693.62 m^2

Substituting the ρ and A values in drag force formula,

Assume that vehicle running at the speed of 20 kmph

V = (20*5/18) = 5.56 m/s

Fad = 0.5 * 1.225 * 693.62 * 0.0265 * (5.56)^2

= 11.258 * (5.56)^2

Fad = 62.594 N

Now find the total force = Fte = Frr+Fad

Fte = 39043.8+62.594

Fte = 39106.394 N

To find the power required by towing vehicle

Therefore find the power value of towing vehicle by equating the total force value in power formula,

Power required for towing vehicle Ptow = Fte * v

= 39106.394 * 5.56

Ptow = 217431.550 W

By converting the unit of power we get,

Ptow = 217.431 KW

To find the torque of the vehicle

Torque (T) = Fte * R

= 39106.394 * 0.5715

T = 22349.30 N-m

Hence power and torque of towing vehicle during the speed of 20kmph is obtained and they are given below

Power = 217.431 KW

Torque = 22822.03 N-m

STUDY-7:

From the above study-6, we obtain the value of the power of towing vehicle and torque to push/pull an aircraft with respect to our given velocity is obtained and now we want to find the energy required for the vehicle.

To find the Energy required for the vehicle

Energy (E) = Ptow * t

where t = time taken for towing

Here we consider the time taken for towing as 20 mins

E = 217.431 * (1200/3600)

E = 72.477 KWh

This above data shows that how much power taken in the speed of 20 kmph and how much energy consumed in 20 mins of time.

In this case, we want to find the input power to drive the duty cycle of the towing vehicle. The output power is considered from the study-6 that values are based upon certain assumptions and calculations from the towing vehicle model as Douglas Tugmaster type TBL- 280 Mk4 from the website.

The formula for duty cycle is given below,

Duty cycle = Power input/Power output

Power = Voltage * Current

Assuming,

Input Voltage supply (Battery specification) = 400 V

Input Current value = 620 A

Now substitute the voltage and current value in the power formula to get input power data,

Power = Voltage * Current

Power Input = 400 * 620 = 248000 W

By converting the unit of power from W to KW we get,

Power Input = 248 KW

Therefore we obtain power input and power output now substitutes these values in duty cycle,

Duty cycle = Power output/Power input

= 217.431/248 = 0.876

Duty cycle = 87.6 % for the towing vehicle Douglas Tugmaster type TBL- 280 Mk4. This duty cycle is obtained for our system based upon several assumptions.

Block diagram of electric powertrain:

CONCLUSION:

Therefore all the various study's about the aircraft is analyzed and calculations to find the force and power required to push/pull an aircraft by a towing vehicle and energy requirement to fulfill aircraft towing application are also determined. The values of the mathematical expression from study-6 and study-7 are given below,

Power = 217.431 KW

Torque = 22822.03 N-m

Energy = 118.335 KWh