Project-1: Powertrain for aircraft in runways
Powertrain for aircraft in runways
1. Search and list out the total weight of various types of aircrafts.
The aircraft gross weight (also known as the all-up weight and abbreviated AUW) is the total aircraft weight at any moment during the flight or ground operation.
An aircraft's gross weight will decrease during a flight due to fuel and oil consumption. An aircraft's gross weight may also vary during a flight due to payload dropping or in-flight refuelling.
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.
The following image depicts takeoff weight components.
MTOW-Maximum Take off weight
MLW-Maximum Landing Weight
|
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 |
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.
The difference between the maximum taxi/ramp weight and the maximum take-off weight (maximum taxi fuel allowance) depends on the size of the aircraft, the number of engines, APU operation, and engines/APU fuel consumption, and is typically assumed for 10 to 15 minutes allowance of taxi and run-up operations.
Maximum takeoff weight (MTOW)
The maximum takeoff weight (also known as the maximum brake-release weight) is the maximum weight 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.
In operation, the maximum weight for takeoff may be limited to values less than the maximum takeoff weight due to aircraft performance, environmental conditions, airfield characteristics (takeoff field length, altitude), maximum tire speed and brake energy, obstacle clearances, and/or en route and landing weight requirements.
Maximum landing weight (MLW)
The maximum weight 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 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.
2. Difference between ground speed and air speed
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.
There is a difference between ground speed and air speed to understand this we should take in to account wind speed too.
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. 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. A positive velocity is defined to be in the direction of the aircraft's motion. We are neglecting cross winds, which occur perpendicular to the flight path but parallel to the ground, and updrafts and downdrafts, which occur perpendicular to the ground.
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.
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.
For example taking wind speed as 20 km/hr and runway is east-west runway the wind blowing towards west and the flight runs at 80 km/hr the wind speed acting in the west and the flight takes off east then the
Airspeed=Groundspeed(80)- Wind Speed(-20) =100 km/hr
If the planes runs towards west along the wind blowing direction then
the Airspeed=Groundspeed(80) - Wind Speed(20)=60km/hr
Hence there is a 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?
Reason :-
Generally, it is not recommended to use aircraft engine power to move it on the ground at the airport because there are some disadvantages like the engine power will create a large noise, and there will be fuel losses while moving the aircraft on airport. The use of engine thrust near terminals is restricted due to the possibility of jet blast damage.
If we talk about safety then during taxiing, aircraft travel slowly. This ensures that they can be stopped quickly and do not risk wheel damage on larger aircraft if they accidentally turn off the paved surface. Taxi speeds are typically 30 to 35 km/h.
For movement on the ground the aircraft uses it own engine power, which is called taxing.
Although many aircrafts are capable of moving in backward using reverse thrust, as result the jet blast or prop wash might cause damage to the terminal building or equipment. Engine close to ground may also blow sand and debris forward and then suck them into the engine, causing damage to the engine.
Therefore there are pushback trucks in the airport. A pushback truck lifts the front weel of the aircraft, their role in most airports is to move the aircraft away from the parking spot on to the taxiways, which is called towing.
Unwanted consequences mainly arising from the unintended movement of the aircraft during engine running.
i) Effectively a loss of control can happen, especially during high power engine running. Damage can occur to the aircraft itself, other aircraft nearby or to airside structures.
ii) There is a risk of injury to ground support personnel who may be in relatively close proximity to the aircraft.
iii) It is easier for truck driver to see the surroundings better than the pilot sitting in the cockpit with limited window. The pushback driver knows the airport better than the pilot
iv) It also saves fuel. virgin Atlantic had proposed a new system in which pushback truck will move the aircraft all the way to runway to save fuel and reduce impact of environment.
v) The plane engines are very loud. When more than one plane will add up their sound, than it will not be pleasent for passangers and others near airport.
4. How an aircraft is pushed to runway when its ready to take off?
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.
There are basically two type of pushings those are :-
a) Towing
b) Taxing
a)Towing:- In the parking areas, where taxing the aircraft is not practical or is unsafe, such as moving aircraft in and out of mainteance hangars, or moving aircraft that are not under their own power or moving backward, then towing of aircraft is performed using the power of a specialized ground vehicle attached to or supporting the nose landing gear. The traditional method of allowing the ground vehicle to move an aircraft is to attach it to the aircraft nose landing gear by means of towbar.
As the pilot can't see what is behind the aircraft, steering is done by pushback tractor driver and 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 towing is completed, the towbar is disconnected and the aircraft can taxiing forward under its own power.
Fig --> Towing Vehicle
Fig:- plane Moving ina airport By using Towing vehicle
b)Taxiing :-
Taxiing is the movement of an aircraft on the ground under its own power while on the suface. The aircraft always moves following the yellow lines, to avoid collision with the surrounding buildings, vehicle or other aircrafts. The taxiing motion has a speed limit. Before making turn the pilot reduces speed further to prevent tire skids just like other vehicles. The reason for taxing is to reach the vehicle into runway or from runway to terminal.
Basically, taxing is used to towing or push-back where the aircraft is moved by a tug.
Image :- Taxing moment of plane
5.Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.
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 Vr). 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.
B] Tyre Design:
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 innerliner (integral rubber lining that is engineered to prevent the diffusion of the inflation gas into the casing.).
C] 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.
D] Tyre Pressure:
Aircraft tires are usually inflated with nitrogen to minimize expansion and contraction from extreme changes in ambient temperature and pressure experienced during flight. Dry nitrogen expands at the same rate as other dry atmospheric gases (normal air is about 80% nitrogen), but common compressed air sources may contain moisture, which increases the expansion rate with temperature.
Tests of airliner aircraft tires have shown that they are able to sustain pressures of maximum 800 psi (55 bar; 5,500 kPa) before bursting. During the tests the tires have to be filled with water, to prevent the test room being blown apart by the energy that would be released by a gas when the tire bursts.
The main landing gear on the Concorde was typically inflated to 232 psi (16.0 bar), whilst its tail bumper gear tires were as high as 294 psi (20.3 bar). The high pressure and weight load on the Concorde tyres were a significant factor in the loss of Air France flight 4590
E] 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. Force and power required to push / pull an aircraft by a towing vehicle.
For this question, the Towing vehicle considered is KAMBLAR Tow tractor TBL 190 and the aircraft considered is Airbus A319
TBL 190 is designed for pushback and maintenance towing of aircraft from MD-80/A319 up to B777/A340.
Length: 8,100 mm
Width: 3,450 mm
Height: 2,050 mm
Thus, frontal area is calculated to be: 7.07m2
Dry weight: 15,150 kg
Working speed: 23 km/h, 30 km/h (14.3 mph)
Ref : https://kalmarmotor.com/en/products/towbarless-tractors/tbl-190/
The Airbus A319 has the following specifications:
Length 33.8m
Wingspan 35.8m
Height 11.8m
Maximum take-off weight 64,000 – 75,500 kg
Weight of Aircraft 35,400 kg
Drag Coefficients (Cd): Taxing: 0.031
Take-off: 0.024
Landing: 0.017
Ref : https://en.wikipedia.org/wiki/Airbus_A319
The frontal area for the Airbus A319 can estimated as
Area = (Width)*(Height)
= (2*2.54)*(2*2.38)
= 24.18m2
The area of the wings can be estimated to be
Area = Width*Height
(35.08-(2*2.54))*(0.3)
=30.72*0.3
=9.2118m2
Hence, the total frontal area to be considered for the aircraft and tow truck will be
=Frontal Area of tow truck + Frontal Area of Aircraft
= Frontal Area of tow truck + (Frontal Area of Wings + Frontal Area of cabin)
= 7.07 + 9.2118 + 24.18
=40.46m2
Now,
push or pull an aircraft by a towing vehicle, 3 type of forces will act on that vehicle. Those are -
A] Rolling resistance force B] Aerodynamic drag force
Note : Hill climbing force and due to constant speed acceleration force is absent in this application.
A] Rolling resistance force
Frr = urr mg
Where, Frr is the Rolling Resistance Force in N
urr is the Coefficient of Rolling Resistance
m is the total mass of vehicle in kg
g (g=9.81) is the acceleration due to gravity in m/s2
Here in this case for towing vehicle for aircraft urr= 0.013
B] Aerodynamic drag force
Fad = (1/2) * p * V^2 * A * (Cd)
Where, Fad is the Aerodynamic Drag Force in N
p is the Air Density
A is the Frontal Area of vehicle in m2
Cd is the Drag Coefficient
V2 is the velocity in m/s
In this case air drag co-efficient for towing vehicle(Cd_t)= 0.5 and for aircraft or payload(Cd_a)= 0.045
We make above calculation in excel and the results as below,
Rolling resistance force = 6440 N
Aerodynamic drag force = 665 N
Total tractive force = 7105 N
Power requried for vehicle = 49.50 KW
We also make simulink model for the above calculation
Note : The excel calculation file and matlab file is attached.
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.
Based on the calculations done in question no. 6A.
Force required to push/pull the aircraft = 7105 N
Power required = 49.50 KW
The Radius of the Tyre for the Tug - 25inches = 0.635m
Gear ratio= 8
Transmission Effeciency (nt) = 87%
Motor Efficiency (nm) = 95%
| Parameters | Values |
| Mass of towing vehicle kg | 15150 |
| Mass of aircraft kg | 35400 |
| Total Area m^2 | 40.46 |
| Coefficent of rolling resistance | 0.013 |
| Speed of the vehicle kmph | 25 |
| Coefficent of Drag | 0.545 |
| Air Density kg/m^3 | 1.25 |
| Tire radious m | 0.635 |
| Gear ratio | 8 |
| Transmission efficency % | 0.87 |
| Motor efficency % | 0.95 |
| Time of operation Hours | 0.25 |
| Total tractive force N | 7105 |
| Power requried KW | 49.5 |
then,
Torque required for the wheels (Tw) = Total Force *Radius in meters
= 7105*0.635
= 4512
Motor Torque = Wheel torque/(Gear ratio*nt)
= 4512/(8*0.87)
= 648 N
For nm =95%. The required motor Torque (Tm)= 648/0.95 = 682 NM
Similarly. The total power required by the motor considering all the efficiencies
(Pt) = 49.50/(0.87*0.95)= 59.89 KW
Form this calculation I found dana TM4 SRI 300 motor series is best for this application the specifications of motor is as follows
Key product data
• Mechanical Interfaces for traction and pump available
• Voltage range1: 48V - 144V
• Peak torque range: Up to 700 Nm
• Cont. power: Up to 60kW
• Peak power capability: Min. 150kW2
• Max. operating speed: 6,000 RPM
so voltage rating of the motor is 144 V
then current is given as 75000/144 = 520 A
Let us assume the towing operation was done for a 15 minutes (0.25Hrs) duration.
Then, Total Energy consumed = 59.89* 0.25= 15 KWh
If we consider the battery capacity = 75 kw is used by the towing vehicle then. The duty cycle range to control the speed from 0 to max speed (6.94 m/s) is given as
Duty Cycle (d)= (Required Power)/ (Rated power)= 59.89/75 = 0.79
Therefore the controller will be able to provide a duty cycle ranging from 0 to 80% in order to control the towing speed.
In order to demonstrate the desiged moodel I use DC7 block as follows
Results :
As seen in above results the duty cycle is maintained the near to 0.8 and also voltage and current are maintained to rated values.
Block Diagram of Powertrain:
Note : The assumed parameters and excel calculation file is attched.