All Courses
All Courses
Courses by Software
Courses by Semester
Courses by Domain
Tool-focused Courses
Machine learning
POPULAR COURSES
Success Stories
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…
Jiji M
updated on 16 Sep 2022
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.
Part B:
6. A. With necessary assumptions, calculate the force and power required to push / pull an aircraft by a towing vehicle.
B. Develop the model for the calculated force and power using Simulink.
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)
B. Also, Design the parameters in excel sheet.
PART A
Answers:
1. Search and list out the total weight of various types of aircrafts.
An average aircraft weighs around 41,000 kg, which is the empty weight. This is the weight of airplane when its fuel tanks are empty and there are no people or luggage on board. The below figure shows the classification of different aircrafts.
The weights considered for an aircraft are :
The above table shows the Maximum Empty Weight and Maximum Take off weight of 6 most recognisable aircarfts.
2. Is there any difference between ground speed and air speed?
Ground speed is the sum of the airspeed and windspeed. If the aircraft is flying in the same direction as that of the wind, the aircraft will experience tailwind and the ground speed becomes higher than the air speed. If the wind is blowing in the opposite direction of the aircraft, then aircraft will experience headwind and the ground speed will become lower than airspeed. Ground speed is considered as the speed of the aircraft with respect to the ground.
Airspeed is the speed at which the aircraft is moving relative to the air it is flying in. It can also be considered as the speed at which the air is flowing around the wing of aircraft. Further, airspeeds are of 3 types; Indicated airspeed, caliberated airspeed and true airspeed.
Indicated airspeed is calculated directly off an aircraft's pilot-static system. It is calculated off the aircraft's dynamic pressure - difference between its total pressure and static pressure.
Caliberated airspeed is the airspeed adjusted for variety of errors.
True airspeed is tha actual speed at which an aircraft is moving relative to the air it is travelling in.
The above three figures shows the relationship between, ground speed, airspeed and windspeed.
3. Why is it not recommended to use aircraft engine power to move it on the ground at Airport?
While using the aircraft engine power to move it on the ground, it creates huge noise in the surroundings. Huge amount of fuel is also consumed while using its own power. The usage of high power mounted engines have risk of blasting and usage of low power mounted engines have risk of impurities on ground entering into engine. Aircrafts usually move using their own engine power on all the apron and the taxiways towards runways, after landing at the assigned gate. The only time, they uses the external support is while pushback from the gate. For large turbofan aircraft they need a pushback tractor to reverse the aircraft. Once the pushback is done, the aircraft will move forward using its own engine power. Aircrafts are pushed back from the gate to prevent reverse thrust from engine being used, which could create high-speed jet blast. Any debris can damage, airport terminals, jetways and ground vehicles. To move the aircraft, we can either use, reverse thrust on engine, or use a tow vehicle to push airplane back. Use of towing is much more safer than reverse thrust as they can cause high power engine to have jet blat during the reverse thrusting.
4. How an aircraft is pushed to runway when its ready to take off?
Pushing aircraft from the parking position to the runway is done using an external power. The method of pushing back the aircraft to runway using external assistance is known as taxiing or towing. Pushbacks are done using pushback tractors. Since pilots are not able to see the rear side of the airplane, the aircraft will be moved back with the help of the pushback tractor. Depending on the type of aircraft and airline procedure, the bypass pin may be temporarily clamped to nose gear to disconnect it from aircrafts's steering. The tug attached to the plane's nose gear cradle the nose gear and then lift it up before moving the plane. In this way, the tractor driver can control the aircraft during pushback. The below picture shows the pushback tractor connected with the aircraft controlling the aircraft at the time of pushback.
5. Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.
Tyre design:
An aircraft tyre is constructed based on its purpose. The tyre need to support the weight of the aircraft when it is on the ground. It need to provide necessary traction for braking and stopping of aircraft. It should also help to absorb shock of landing and provide cushioning the roughness take off, roll out and towing. Below are some technical aspects of aircraft tyre:
1. Retreading- It is the method of restoring a worn tyre by renewing the tread area or by renewing the tread area along with one or both side walls.
2. Load rating - It is the maximum permissible load at the specified inflation pressure.
3. Ply rating- It is an index of tyre strength and used to identify the maximum recommended load rating and inflation pressure for a specified tyre.
4. Speed rating - The maximum take off speed to which the tyre has been tested.
5. Skid depth - It is the distance between the tread surface and deepest groove as measured in the mould.
The aircraft tyre can be tube-type or tube-less and radial or bias. Tubeless tyres are more advantageous than tube-type. As the name suggests, they will not have tube on the sidewall of the tyre, while the tube-type will have the tube on sidewalls of tyre. Most of the aircrafts are using the tubeless type now.
The below figure shows the basic four parts of the aircraft tyre.
Bead - Tyre bead anchors the tyre carcass and provides a dimensioned, firm mounting surface for the tyre on the wheel rim.
Carcass plies - They are also called as casing plies, are applied in layers to give tyre strength and form carcass body of the tyre. Each ply consists of nylon sandwiched in between 2 layers of rubber.
Tread - It is the crown area of the tyre designed to come in contact with ground. It is a rubber compound formulated to resist wear, abrasion, cutting, cracking and heating.
Sidewall - It is a layer of rubber designed to protect the carcass plies. It imparts strength to the cord body.
Chine - Some sidewalls are mounted to form a chine, which is a built-in deflector used on nose wheels for aircraft with fuselage mlounted engines.
Takeoff Power:
Take off of an aircraft is the phase where aircraft leaves the ground and becomes airborne. For light weighted aircrafts, they use full power at the time of takeoff. However, for large aircrafts, they use less power for the takeoff to prolong engine life, reduce maintainance cose and noise emissions. The forces considered while calculating the takeoff power are drag, thrust and rolling resistance.
Thrust is force generated by engine of aircraft to move the aircraft into the air. To maintain the aircraft at constant speed,thrust must be a constant and to climb or descend, thrust will be increased or decreased.
Drag is the force that opposes the relative motion of an object through air. It will always opposes the motion of the object and in aircraft the opposing force to the thrust is drag.
Rolling resistance is the friction due to the contact of wheels of skids on the ground.
The effect of these three forces are considered during the take off.
To analyze takeoff power we are considering parameters like drag force(D), rolling resistance (F), thrust of propulsion(T)
During take-off; m*dv/dt = T-F-D
m-mass of aircraft
dv/dt - acceleration
Safe flying speed, Vr = 1.1*Vstall
Vstall = √((2*(G/S))/(ρ*CLmax))
where, G is aircraft weight, S is aircraft wing area, CLmax is maximum lift coefficient, ρ is air density.
Take-off power = force*displacement.
Rolling Resistance:
Rolling resistance also called as rolling friction or drag is the friction due to the contact of wheels of skids on the ground. It is mainly caused by the non-elastic effects. That means, not all the energy needed for movement is recovered when the pressure is removed. It can come as hysterisis loss and permanent deformation of the object or surface.
Rolling resistance force, F = Crr*N, where N is normal force perpendicular to the surface on which wheel is rolling.
Coefficient of rolling resistance, Crr = √z/d, where z is sinkage depth and d is diameter of rigid wheel.
In aircraft the friction between aircraft and runway will be proportional to the normal force exerted by the aircraft on the runway.
So, F = Crr *(W-L), where W-L is the difference between weight of aircraft and lift which is considered as N. Typical value of Crr is 0.02.
Tyre Pressure:
Aircraft tyres operating pressures are really high. A typical airliner tyre can handle 38 ton of load. It can meet ground around 500 times before a retread. For airliners, pressure is upto 200 psi and it is higher for jets. Below is the tire pressure and maintainance values for a domestic aircraft:
Aircraft tyres are designed to withstand heavy load for short period of time. As the weight of the aircraft is increased, the number of tyres required will be also increased inorder to distribute the whole weight evenly. Tyre tread patterns are designed to withstand cross wind situation, braking effect, and to channel water away for hydroplaning. Aircrafts are usually inflated with nitrogen inorder to minimize expansion and contraction from sever changes in ambient temperature and atmospheric pressure.
Brake Forces:
To land an aircraft, either hydraulic or electric brake systems are used. Since hydraulic brake systems add weight to the aircraft, electric brake systems are mostly used for braking in aircraft. Brake force mainly aims to reduce the distance while landing. Also, there are 2 kinds of brakes in an airplane, air brakes and landimg brakes. While landing, the touchdown velocity should be approximately equal to the Vstall or stall speed. This is achieved by increasing drag and decelerating aircraft to minimum flying speed.
While calculating takeoff power, we had an average acceleration approach, where,
m*dv/dt = T-F-D
dv/dt = -(T+F+D)/m
-(dv/dt) is considered as the deceleration, so braking force= mass*deceleration.
Where, T is thrust, F is rolling resistance force and D is drag.
The above figures shows the landing and deceleration, along with the components of forces acting uring braking.
PART B
Answers:
6. A. With necessary assumptions, calculate the force and power required to push / pull an aircraft by a towing vehicle.
B. Develop the model for the calculated force and power using Simulink.
A. The main two forces acting while pushing or pulling an aircraft by using towing vehicle will be aerodynamic drag and rolling resistance force.
Rolling Resistance can be calculated as;
F=Crr*N, where N is the normal force acting perpendicular to the surface on which wheel is rolling.
N = m*g, where m is the mass and g is the acceleration due to gravity.
We are taking the typical value for Crr, i.e, 0.02.
Aerodynamic drag force can be calculated as;
Fad = 0.5* air density * A*Cd*v²
where A is the frontal area and v is velocity.
Assumptions:
Velocity or speed of vehicle in m/s = 8m/s.
Mass of towing vehicle = 35000 kg.
Mass of aircraft = 140000 kg
Total mass, m = 140000+35000 = 175000 kg
Frontal area, A = 20 m².
Drag coefficient, Cd = 0.5
Coefficient of Rolling resistance, Crr = 0.02
Air density = 1.25 kg/m³
acceleration due to gravity = 9.8 m/s²
Calculating, Rolling resistance force, F = Crr*m*g = 0.02*175000*9.8 = 34300 N.
Calculating aerodynamic drag, Fad = 0.5*air density * A*Cd*v²=0.5*1.25*20*0.5*8² = 400 N.
Total force required to push / pull an aircraft by a towing vehicle = Rolling resistance force+aerodynamic drag = F +Fad = 34300 N+400 N = 34700 N.
Total power required to push / pull an aircraft by a towing vehicle, P = Force *velocity = 34700*8= 277600 W = 277.6 KW.
B. Creating the model using, constant blocks, square block, add block, multiplication block and display.
Here we have used, constant blocks for all the defined values and addition, multiplication blocks to carry out the mathemetical equations mentioned and display block to display the values.
To obtain the power and force, we need to multiply some values and add some values to achieve both. For realizing that we have provided the constant blocks and gave all the assumed values we have taken for the calculations. Then we have provided the addition and multiplication blocks and didplay blocks to show the force and power values. Simulink model created has been 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.
(Hint :DC7 Block)
B. Also, Design the parameters in excel sheet.
A. We are considering the total power and force calculated in the above section 6.A.
Total force required to push / pull an aircraft by a towing vehicle, Ft= 34700 N
Total power required to push / pull an aircraft by a towing vehicle, P = 277.6 KW
Now we need to assume the values of Gear ratio, Transmission efficiency, Motor efficiency, Radius of tyre,r and the time taken for towing, battery capacity used by towing vehicle.
Assumptions:
Gear ratio | 7 |
Transmission efficiency | 85% |
Motor efficiency | 95% |
Tyre radius, r | 15 inches = 0.381m |
Battery capacity | 400 KW |
Time taken for towing | 10 mins = 0.16 hrs |
Wheel torque, Tw = Force * Radius = 34700 * 0.381= 13220.7 Nm
Motor torque,Tm = Tw/(G*transmission efficiency) = 13220.7/(7*0.85)= 2221.96 Nm
Required motor torque with motor efficiency of 95% = 2221.96/0.95 = 2338.905 Nm
Considering all efficiencies, total Power, P = 277.6 /(0.85*0.95) = 343.77 KW.
Total energy consumed for 10 minutes = 343.77 *0.16 =55 KWh.
Duty cycle, D = Required power/Rated power = 343.77 /400 = 0.85 ≈ 85% duty cycle.
We can use a duty cycle from 0 to 85% to control the aircraft speed from 0 to highest.
Simulink model:
Results:
Battery Output:
DC drive output:
B. Below is the design parameters of towing vehicle's total force and power calculated in excel sheet:
Excel file has been attached.
Leave a comment
Thanks for choosing to leave a comment. Please keep in mind that all the comments are moderated as per our comment policy, and your email will not be published for privacy reasons. Please leave a personal & meaningful conversation.
Other comments...
Week 5 Challenge
1. Consider a scenario where an aggressive driver is accelerating very rapidly and braking harshly in a city driving. Is battery better a choice to supply power than UC in this scenario? True False Why? Answer: False. In this scenario, battery is not a better choice in the given driving scenario.The drivers driving…
12 Feb 2024 02:39 PM IST
Week 2 Challenge
1. Compare four different types of fuel cells and state their applications. Answer: The four types of fuel cells are: Polymer Electrolyte Membrane Fuel Cell (PEM) Alkaline Fuel Cell (AFC) Direct Methonol Fuel Cell (DMFC) Solid Oxide Fuel Cell (SOFC) PEM AFC DMFC SOFC Power 0.01 - 250 0.1 - 50 0.001…
01 Feb 2024 12:58 PM IST
Week 4 Session 5
1. Explain the various applications of Power converters in an Electric vehicle. For Example what type of converter will you use for Horn which requires DC and less than 10V. Likewise come up with different applications. Application: Here are some examples of power converter applications in an electric vehicle: DC-DC Converter…
24 Jun 2023 06:28 AM IST
Final Project: Electric Rickshaw modelling
Create a detailed MATLAB model of an electric rickshaw (three wheel passenger vehicle) as per details below: Rear wheels driven by PM brushed type motor Assume efficiency points of motor controller and motor Make an excel sheet of all input and assumed data Results: For any three standard driving cycles show…
23 Jun 2023 06:59 AM IST
Related Courses
0 Hours of Content
Skill-Lync offers industry relevant advanced engineering courses for engineering students by partnering with industry experts.
© 2025 Skill-Lync Inc. All Rights Reserved.