Project-1: Powertrain for aircraft in runways
Part A:
1. Search and list out the total weight of various types of aircrafts.
2. Is there any difference between ground speed and air speed?
3. Why is it not recommended to use aircraft engine power to move it on the ground at Airport?
4. How an aircraft is pushed to runway when its ready to take off?
5. Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.
1)
An aircraft's gross weight will decrease during a flight due to fuel and oil consumption. An aircraft's gross weight may also vary during a flight due to payload dropping or in flight refuling.
At the moment of releasing its brakes, the gross weight of an aircraft is equal to its takeoff weight. During flight, an aircraft's gross weight is referred to as the en-route weight or in-flight weight.
Maximum taxi weight (MTW)
The maximum taxi weight (MTW) (also known as the Maximum Ramp Weight (MRW) is the maximum weight authorized for maneuvering (taxiing or towing) an aircraft on the ground as limited by aircraft strength and airworthiness requirements. It includes the weight of taxi and run-up fuel for the engines and the APU (Auxillary Power Unit).
It is greater than the maximum takeoff weight due to the fuel that will be burned during the taxi and runup operations.
Maximum takeoff weight (MTOW)
The maximum takeoff weight (also known as the maximum brake-release weight) is the maximum weight authorised 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.
Maximum landing weight (MLW)
The maximum weight authorised for normal landing of an aircraft.The MLW must not exceed the MTOW.
Overweight landings require a structural inspection or evaluation of the touch-down loads before the next aircraft operation.
Maximum zero-fuel weight (MZFW)
The maximum permissible weight of the aircraft less all usable fuel and other specified usable agents (engine injection fluid, and other consumable propulsion agents). It is the maximum weight permitted before usable fuel and other specified usable fluids are loaded in specified sections of the airplane.
|
Type |
MTOW [kg] |
MLW [tons] |
|
640,000 |
591.7 |
|
|
589,670 |
||
|
575,000 |
394 |
|
|
447,700 |
346.091 |
|
|
443,613 |
306.175 |
|
|
412,770 |
295.742 |
|
|
Antonov An-124-100M |
405,060 |
330 |
|
396,900 |
295.742 |
|
|
381,000 |
288.417 |
|
|
377,840 |
285.700 |
|
|
377,840 |
260.320 |
|
|
371,950 |
240 |
|
|
367,400 |
256 |
|
|
347,800 |
260.816 |
|
|
351,800 |
251.29 |
|
|
347,450 |
223.168 |
|
|
340,200 |
265.300 |
|
|
308,000 |
233.5 |
|
|
299,370 |
237.683 |
|
|
297,550 |
213.00 |
|
|
276,700 |
190 |
|
|
273,300 |
185 |
|
|
270,000 |
175 |
|
|
270,000 |
195.04 |
|
|
256,280 |
183 |
|
|
254,000 |
192.777 |
|
|
254,000 |
201.849 |
|
|
253,500 |
181 |
|
|
250,000 |
175 |
|
|
242,000 |
185 |
|
|
242,000 |
180 |
|
|
231,300 |
166.92 |
|
|
228,000 |
172.365 |
|
|
211,400 |
||
|
208,000 |
175 |
|
|
204,000 |
158.758 |
|
|
192,000 |
140 |
|
|
187,000 |
136.08 |
|
|
185,000 |
111.1 |
|
|
163,000 |
138 |
|
|
159,000 |
136.078 |
|
|
157,000 |
124 |
|
|
152,000 |
151.9 |
|
|
151,000 |
97.5 |
|
|
151,000 |
112.1 |
|
|
147,000 |
||
|
142,000 |
123 |
|
|
141,000 |
122 |
|
|
140,000 |
||
|
125,000 |
||
|
124,000 |
101.6 |
|
|
117,000 |
86.3 |
|
|
116,000 |
89.9 |
|
|
106,000 |
79.5 |
|
|
104,000 |
79.5 |
|
|
104,000 |
80 |
|
|
104,000 |
87.5 |
|
|
87,500 |
||
|
85,000 |
66.36 |
|
|
85,000 |
71.35 |
|
|
84,000 |
70.1 |
|
|
Airbus A321-100[17] |
83,000 |
77.8 |
|
79,000 |
65.32 |
|
|
78,000 |
68.1 |
|
|
73,000 |
63.28 |
|
|
72,500 |
62.4 |
|
|
72,500 |
62.4 |
|
|
71,000 |
64.41 |
|
|
70,700 |
||
|
70,000 |
58.06 |
|
|
Airbus A320-100[17] |
68,000 |
66 |
|
68,000 |
54.9 |
|
|
68,000 |
||
|
67,000 |
||
|
66,000 |
54.66 |
|
|
65,000 |
57.61 |
|
|
65,000 |
||
|
64,000 |
62.5 |
|
|
63,000 |
51.7 |
|
|
60,000 |
49.9 |
|
|
59,000 |
50.80 |
|
|
59,000 |
57.5 |
|
|
55,000 |
47.174 |
|
|
55,000 |
||
|
54,000 |
||
|
50,000 |
46.265 |
|
|
50,000 |
||
|
48,600 |
||
|
48,500 |
||
|
48,000 |
43 |
|
|
46,000 |
||
|
46,000 |
39.95 |
|
|
44,000 |
||
|
42,000 |
36.74 |
|
|
39,000 |
||
|
37,500 |
32.8 |
|
|
36,500 |
33.345 |
|
|
36,000 |
32.8 |
|
|
33,000 |
30.39 |
|
|
33,000 |
||
|
30,400 |
||
|
28,000 |
28.01 |
|
|
23,000 |
21.319 |
|
|
22,800 |
22.35 |
|
|
22,800 |
21.5 |
|
|
22,000 |
19.3 |
|
|
18,600 |
18.3 |
|
|
13,150 |
12.930 |
|
|
11,500 |
11.25 |
|
|
10,890 |
10.570 |
|
|
9,752 |
8.709 |
|
|
8,300 |
7.665 |
|
|
8,150 |
7.65 |
|
|
7,765 |
7.605 |
|
|
7,761 |
7.103 |
|
|
7,000 |
||
|
4,800 |
4.43 |
2)
Ground Speed
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 the ground speed and the wind speed.
3)
- The risks which may arise from engine ground running relate to the potential for loss of control of the aircraft by those persons occupying the pilot seats in the flight deck.
- Unwanted consequences from such static running are mainly related to those arising from the unintended movement of the aircraft during engine running - effectively a loss of control - especially during high power engine running.
- Damage can occur to the aircraft itself, other aircraft nearby or to airside structures.
- In addition, there is a risk of injury to ground support personnel who may be in relatively close proximity to the aircraft.
- When modern jet engines are operated at rated thrust levels, the exhaust wake can exceed 325 kn or 603 km/h immediately aft of the engine exhaust nozzle.
- This exhaust flow field extends aft in a rapidly expanding cone, with portions of the flow field contacting and extending aft along the pavement surface.
- Exhaust velocity components are attenuated with increasing distance from the engine exhaust nozzle. However, an airflow of 260 kn or 483 km/h can still be present at the empennage, and significant people and equipment hazards will persist hundreds of feet beyond this area.
- At full power, the exhaust wake speed can typically be 130 kn or 240 km/h at 61 m beyond the airplane and 43 to 88 kn or 80 to 161 km/h well beyond this point.
-
The extensive noise arises from the engine power also dangerous for humans and other living things around the vicinity.
Hence for the above reasons it is not recommended to use engine power to move on the ground.
4)
- In aviation, pushback is an airport procedure during which an aircraftis pushed backwards away from an airport gate by external power. Pushbacks are carried out by special, low-profile vehicles called pushback tractors or tugs.
- Although many aircraft are capable of moving themselves backwards on the ground using reverese thrust (a procedure referred to as a powerback), the resulting jetblast or propwash might cause damage to the terminal building or equipment. Engines close to the ground may also blow sand and debris forward and then suck them into the engine, causing damage to the engine. A pushback is therefore the preferred method to move the aircraft away from the gate.
- Pushbacks at busy aerodromes are usually subject to ground control clearance to facilitate ground movement on taxiways. Once clearance is obtained, the pilot will communicate with the tractor driver (or a ground handler walking alongside the aircraft in some cases) to start the pushback. To communicate, a headset may be connected near the nose gear.
- Since the pilots cannot see what is behind the aircraft, steering is done by the pushback tractor driver and not by the pilots. Depending on the aircraft type and airline procedure, a bypass pin may be temporarily installed into the nose gear to disconnect it from the aircraft's normal steering mechanism.
- Once the pushback is completed, the towbar is disconnected, and any bypass pin removed. The ground handler will show the bypass pin to the pilots to make it clear that it has been removed. The pushback is then complete, and the aircraft can taxi forward under its own power.
5)
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. 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 (once proper air displacement occurs under / over the wings, an aircraft will lift off on its own; controls are to ease that in).
The nose is raised to a nominal 5°–15° nose up pitch attitude to increase lift from the wings and effect liftoff. For most aircraft, attempting a takeoff without a pitch-up would require cruise speeds while still on the runway.
Tyre Design:-
Based on types of piles used
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
- Tube-type tyres - these require tubes for inflation retention.
- Tubeless tyres - these do not require tubes. They are constructed with an innerliner (integral rubber lining that is engineered to prevent the diffusion of the inflation gas into the casing.).
Rolling Resistance:-
The resistance offered by the tyres against motion of vehicle/aircraft is called as rolling resistance, the rolling resistance is produced during take off/landing in the runway.
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.
Brakes Forces When Landing:-
In general, when the wheels touch the ground, a set of spoilers raise up quickly, which kills the lift provided by the wings. (There are two sets seen in the image below: ground spoilers that only deploy on landing, and spoilers that are used in flight as speed brakes as well as on landing.) While the spoilers provide some drag, their primary purpose is to stop the plane from actually flying, putting all of the weight on the landing gear and in turn making the brakes that much more effective.
Aircraft have highly-engineered, multi-disc brakes made of a carbon-steel material. Manufacturers include Honeywell and Goodrich, part of Collins Aerospace. In general, the brakes are composed of discs that rotate with the wheel and separate discs that are fixed. When pressure is applied—and below you see pressure applied from the right fixed disc on all of the discs—the entire assembly compresses to create the braking action. Carbon brakes are standard today; they cool faster than steel brakes (their predecessor) and can weigh up to 700 pounds less. That represents a significant weight saving for airlines.
Auto Brakes:
Wheel brakes are usually selected to engage automatically after landing. These are called “autobrakes”.that all airliners have several levels of autobrake “severity”. The crew will decide which is the most appropriate to use for every landing depending upon factors like the length of runway, if it is wet or dry, or if the pilots want to exit the runway at a particular point. “For a short wet runway you might select autobrake 3, or MED on the Airbus. For a long dry runway you might select autobrake 1 or LOW on the Airbus".
6)
A
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
https://textrongse.txtsv.com/vehicles/tbl-280
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
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,
Standard or Higher gross weight = 164000 kg
Height = 15.80 m
Width = 43.90 m
Drag coefficient (Cd)= 0.0265
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
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
Drag force = Fad = 0.5⋅ρ⋅A⋅Cd⋅v^2
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 = 348.035N
Now find the total force = Fte = Frr+Fad
Fte = 39043.8+348.035
Fte = 39391.38519 N
Power required for towing vehicle Ptow = Fte * v
= 39106.394 * 5.56
Ptow = 219 W
Ptow = 219 KW
To find the torque of the vehicle
Torque (T) = Fte * R
= 39391.38519 * 0.5715
T = 225120.35 N-m
Power = 219 KW
Torque = 225120.35 N-m
6)
B
Model:-
Blocks used:-
- constant blocks are used to feed the parameters such as mass, coefficients and other parameters
- using product block the resistive forces are calculated.
- using sum block, total resistive forces can be calculated.
- the outputs are visualised using display blocks.
7)
A
Model electric powertrain
Block used:-
- PS Constant
- Solver configuration
- Generic engine
- Torque converter
- Inertia
- Simple gear
- Differential
- Tire
- Vehicle body
- Ideal torue sensor
- Scope
From the above Q.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.
Energy (E) = Ptow * t
where t = time taken for towing
Here we consider the time taken for towing as 20 mins
E = 219 KW * (1200/3600)
E = 73 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
= 219 /248 = 0.88314
Duty cycle =88.314% 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 powertrain:-
7)
B
