Project-1: Powertrain for aircraft in runways

Part A

Search and list out the total weight of various types of aircrafts.

Weight is a major factor in airplane construction and operation, and it demands respect from all pilots and particular diligence by all maintenance personnel. Excessive weight reduces the efficiency of an aircraft and the available safety margin if an emergency condition should arise. The total weight is the maximum take-off weight. It is the maximum mass at which the aircraft is certified for take-off due to structural or other limits.

Aircraft Type	Example Aircraft	Total Weight (Takeoff Weight)

Average Sized Airplane

Boeing 737-800

80,000 kg

Fighter Jet

Boeing F-18 Hornet

113,646 kg

Cargo Airplane

Airbus A300 600F

165,900 kg

Military Helicopter

Boeing RAH-66 Comanche

7,791 kg

Mid-Size Helicopter

Bell 212

5,080 kg

Turboprop Aircraft

Grand Caravan EX

3,994 kg

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Is there any difference between ground speed and air speed?

The importance of the relative velocity explains why, even today, airplanes take off and land on different runways on different days. Airplanes always try to take off and land into the wind. This requires a lower ground speed, which means the plane can take off or land in the shortest distance travelled along the ground. Since runways have a fixed length, you want to get airborne as fast as possible on take-off and stopped as soon as possible on landing. In the old days, a large "wind sock" was hung near the runway for pilots to see which way the wind was blowing to adjust their take-off and landing directions. Now mechanical or electronic devices provide the information that is radioed to the cockpit. It is important to understand the relationships of wind speed to ground speed and airspeed.

Wind Speed: A reference point picked on the ground, the air moves relative to the reference point at wind speed. The wind speed is a vector quantity and has both magnitude and direction. The wind blowing against the motion of aircraft is called Head wind. We have defined a positive velocity to be in direction of the aircraft motion, head wind is a negative velocity. When the wind blows in the same direction of aircraft motion it is called Tail wind. The sign of wind is now positive.

Ground Speed: The speed on which the aircraft moves relative to the point on the ground. Ground speed is a vector quantity.

Air Speed: The relative velocity between the object and the air is called air speed. 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.

AIR SPEED	GROUND SPEED
Speed relative to air.	Speed relative to ground.
Measured quantity. Using Pitot tube.	Calculated quantity. (Air speed + Wind velocity)

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Why is it not recommended to use aircraft engine power to move it on the ground at Airport?

Using an aircraft's engine power to move it on the ground, known as "taxiing under own power," is generally not recommended due to several reasons. First, jet engines produce strong thrust and exhaust, which can create safety hazards such as jet blast, potentially damaging airport infrastructure, vehicles, or nearby personnel. Second, operating engines at low speeds for extended periods increases fuel consumption and emissions, making it less efficient and environmentally unfriendly. Additionally, engine wear and the risk of foreign object damage (FOD) from debris being sucked into the engines can lead to costly maintenance. Instead, aircraft are often towed using ground vehicles like tugs to ensure safety, efficiency, and reduced operational costs.

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How an aircraft is pushed to runway when its ready to take off?

When an aircraft is ready to take off, it is typically pushed back from the gate using a tow tractor or tug. This process, known as pushback, is controlled by ground crew and ensures safe maneuvering without relying on the aircraft's engines, reducing fuel consumption and minimizing the risk of jet blast. Once positioned on the taxiway, the aircraft starts its engines and taxis under its own power toward the runway, guided by air traffic control (ATC). Pilots follow designated taxi routes, using ground markings and lights while maintaining communication with ATC until they reach the assigned runway for takeoff.

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Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.

During takeoff, an aircraft requires takeoff power, which is the maximum thrust generated by engines to achieve the necessary speed for lift-off.

The tyre design of an aircraft is specialized to withstand high loads, rapid acceleration, and extreme temperatures, often reinforced with multiple layers and nitrogen-filled to prevent explosions at high altitudes.

Rolling resistance, caused by the friction between tyres and the runway, affects acceleration and fuel efficiency, with lower resistance improving performance. Tyre pressure is maintained at extremely high levels to support heavy loads and prevent overheating during takeoff and landing.

Upon landing, brake forces, including wheel brakes, thrust reversers, and aerodynamic drag, work together to slow the aircraft safely, ensuring controlled deceleration and reducing stress on tyres and landing gear.

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

The force to move an airplane on an absolute flat runway with no wind at constant low speed is equal to the rolling resistance between the plane and the tarmac.

The rolling resistance for the air plane can be calculated as

Fr=C⋅mr⋅ag${\displaystyle F_r=C\cdot m_r\cdot a_g}$ (1)

Where,

Fr${\displaystyle F_r}$= rolling resistance (N, lbf)

C = rolling resistance coefficient

mr${\displaystyle m_r}$= rolling mass (kg, lbm)

ag${\displaystyle a_g}$= acceleration of gravity (9.81 m/s2)

EXAMPLE - FORCE REQUIRED TO PULL AN AIRPLANE AT CONSTANT LOW SPEED ON TARMAC

If the mass of a plane is 40000 kg and the rolling coefficient between the aircraft wheel and the tarmac is 0.02

The force required to overcome the rolling resistance can be calculated as:

Fr = 0.02 (40000 kg) (9.81 m/s2)

= 7848 N

This force can be delivered by a pulling truck. Enough weight of truck is required to create friction forces against the tarmac that equals the plane rolling resistance.

The friction force for the puller can be calculated to

Ff=μW${\displaystyle F_f=\mu W}$

=μ⋅mf⋅ag${\displaystyle =\mu \cdot m_f\cdot a_g}$ (2)

Where,

Ff${\displaystyle F_f}$= frictional force (N, lb)

μ = friction coefficient

W = weight (N, lbf)

mf${\displaystyle m_f}$= friction mass (kg)

Required Mass for Pulling Truck:

The friction coefficient between a pulling truck rubber wheels and dry tarmac is 0.9.

Since pulling trucks are connected to air crafts nose wheels close to tarmac we simplify the calculation of required truck mass to:

mf${\displaystyle m_f}$= (7848 N) / (0.9 (9.81 m/s2))

= 889 kg

Power required for pulling truck with a velocity of 5m/s:

P= F*V

Where,

F = total force acting on truck (N)

V = velocity of truck (m/s)

P = 7848* 5

= 39.24 kW

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B. Develop the model for the calculated force and power using Simulink.

MAIN MODAL:

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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)

Assumed Parameters:

Parameter	Assumed Value/Range	Explanation
Voltage Range	0 to 400 V	Assumed voltage range of the DC motor/controller system.
Maximum Motor Speed	100,000 RPM	Assumed maximum speed of the motor.
Nominal Motor Speed	50,000 RPM	Assumed nominal speed under full voltage.
Max Output Power	200 kW	Assumed maximum output power the motor can handle at full speed.
Min Motor Speed (Zero Speed)	0 RPM	Minimum motor speed (at zero speed).
Motor Torque Characteristics	Linear between 0 to max speed	Assumed linear torque-speed relationship.
PWM Control Frequency	20 kHz	Typical PWM switching frequency for controlling DC motors.
DC Motor Efficiency	85%	Assumed motor efficiency at various speeds.
Load Characteristics	Linear	Assumed load torque increases linearly with speed.

Duty Cycle Estimation:

The duty cycle in PWM controls the average voltage applied to the motor. The relationship between speed and duty cycle can be approximated by assuming a linear relationship between motor speed and duty cycle. Here's the basic assumption:

Duty Cycle Range Table:

Aircraft Speed (RPM)	Duty Cycle (%)	Explanation
0 RPM	0%	Zero speed corresponds to zero duty cycle.
25,000 RPM	25%	25% of the maximum speed.
50,000 RPM	50%	Nominal speed; 50% duty cycle.
75,000 RPM	75%	Three-quarters of maximum speed.
100,000 RPM	100%	Maximum speed corresponds to 100% duty cycle.

• The duty cycle will range from 0% at zero speed (no power applied) to 100% at the maximum speed (full power applied).
• The duty cycle is assumed to be linearly proportional to the motor speed, meaning at half of the maximum speed, the duty cycle will be approximately 50%.

Block Diagram of Powertrain:

output:

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B. To Design the parameters in excel sheet.