AERONAUTICAL LECTURING NOTES

What is torque? Define moment? Torque is simply a moment of force. Moment of force is just the product of force and perpendicular distance. Unit “Nm”. What is Moment of Inertia? The moment of inertia measures the resistance to a change in rotation.  Change in rotation comes from torque. Moment of inertia I = mr 2 . Please note moment of inertia strictly depends upon the axis of rotation.

What is linear and angular velocity? The rate of change of linear displacement (distance travelled) with respect to time is called as Linear velocity. Unit is “m/s” The rate of change of angular displacement (Angle travelled) with respect to time is so called as Angular velocity. Unit is “rad/s”. What is linear acceleration and derive unit of it? Linear acceleration is defined as the rate of change of linear velocity with respect to time. We know linear velocity bears the unit of “m/s” So for linear acceleration – (m/s)/s  = “ m/s 2 ”. What is angular acceleration and derive unit of it? Angular acceleration is defined as the rate of change of angular velocity with respect to time. We know angular velocity bears the unit of “rad/s” So for linear acceleration – (rad/s)/s  = “ rad/s 2 ”. What is the relation between Angular and linear quantities? Any angular quantity multiplied by radius of rotation gives the corresponding linear quantity. For ex...

What are the layers of atmosphere? Troposphere- 0 to 10 Kms Stratosphere- 11 to 50 Kms Mesosphere-50 to 80 Kms Ionosphere-80 to 500 Kms Exosphere-500 to Infinity Kms What are the axes of an aircraft? Longitudinal Axis- Along the length of the fuselage Lateral axis- Along the length of wing span Normal axis- Mutually perpendicular to the above two axis What are the moments occuring with reference to those axes? Longitudinal axis- Rolling Lateral axis- Pitching moment Normal axis- yawing

What are the major parts of an aircraft? Main wing Tail wing Powerplant Fuselage Landing gear What is the reason for stall? Define critical angle of attack? If the angle of attack for an aerofoil increases from zero deg, you can watch the increase in lift and drag. If you keep on increasing the AOA, at some point sudden loss of aerodynamic forces will occur. Aerofoil can create aerodynamic forces in a large magnitude when attached flow of air occurs at aerofoil surface.  As the aerofoil gets increased AOA, the flow of air starts detaching from the aerofoil surface. If fully detached then no aerodynamic forces will be generated. That is what the reason for stall. The angle at which stalling starts is the critical angle of attack. What is stagnation point? Stagnation point is the point in the airflow where the velocity gets its zero magnitude because of the presence of object in airflow. The flow deviates/joins between upper and lower surface of the ...

What are the phases of flight? Takeoff Climb Cruise Descent Loiter Landing What is aerodynamic centre? Aerodynamic center is the point in the aerofoil where the pitching moment is constant even though if we change angle of attack. To solve flight dynamics problem it is the pivotal point. What is center of pressure? Centre of pressure is the point where the pitching moment is zero. When angle of attack varies cop varies. So it is tedious if we try to solve dynamics of flight by taking COP as reference.

What are the forces acting on flight? Aerodynamic forces- Lift, Drag and Side fore Propulsive force- Thrust Gravitational force- Weight Buoyancy force- Negligible When air flows over wing it creates resultant. We are solving that resultant in three mutually perpendicular axes. So we get Lift, Drag and Side force. Write down the equation for lift and drag? Lift=0.5*(density)* (square of velocity)*(Wing planform area)* (Coefficient of lift) Drag=0.5*(density)* (square of velocity)*(Wing planform area)*(Coefficient of drag) If lift increases, what will happen to drag? Since lift and drag are just the components of the single resultant force which is created because of the airflow over the aerofoil, drag increases if lift increases.

Add caption Fig 1 What is flight path? The curve which we attain by tracing  Center  of gravity( C.G.) of airplane at every second is known as Flight path. What is flight velocity? The tangent drawn to the flight path at any instant gives flight velocity. What is Relative Air flow? When aircraft moves, atmosphere stays rest. But in our dynamics approach in order to make analysis simple, we are considering aircraft to be stationary and the air as moving. So whatever the flight velocity with which we move, we will feel that much velocity against to that; that velocity is what Relative air flow velocity or free stream velocity. What is angle of attack? The angle between relative air flow and the chord line of aerofoil is the angle of attack. Fig 2 What is angle of incidence? The angle between fuselage reference line and average chord of wing is the angle of incidence. see fig. 1 for reference. you just draw chord line for th...

What is parafoil? A leading edge opened aerofoil is called as “Parafoil”. We know already that leading edge is facing into the wind for aerofoil. Since it has been opened, it just admits the air to flow inside the volume covered by the upper and lower surfaces. How aerofoil creates lift? What is bernouli's principle? How it suits to the aerofoil? Aerofoil has its upper surface curved, whereas bottom is moreover flat. Physically the curved portion accelerates the flow and so the top side airflow is getting increase in velocity. Lower surface is experiencing less velocity when comparing the upper surface. We know from Bernoulis law that for a fluid flow, if fluid velocity increases then pressure drops. In the upper we are feeling less pressure and in the bottom a high one. Bernoulis principle: Total energy of a steady flowing fluid system is constant. Ʃ E= k PE+KE= k mgh+0.5 mv 2 =k dividing both sides by volume ρgh+ 0.5ρv 2 =k High p...

What is aerodynamics? Aerodynamics is the study about the object moving in airflow. Here we will pay our attention to the airflow and also to the object immersed in the airflow. What is aerofoil? If you throw a pencil in air, you see, it flies and comes down instantly. So it is also having ability to fly. Technically speaking, every object is having some figures called Coefficient of lift, Coefficient of drag which governs its motion during flight. The shape which has more coefficient of lift and less coefficient of drag can stay in fly for more. Such a shape is what aerofoil. Aerofoil is having top surface (Upper camber) and lower surface (lower camber). Also it has leading edge and trailing edge where the two surfaces meet. Leading edge is facing to the wind. What is chord line? A line joining the leading edge of an aerofoil to the Trailing edge is known as Chord line. What is camber line? We know that aerofoil is having top surface (upper camber)and bot...

Who introduced the flying concepts? Leonarda Da vinci Drawn aerofoil- ornithopter. He might have developed physical prototype. But still now there is no evidence that Da vinci had fly. But his inventions formed the basics of flight. Who made first successful flight? Wright brothers on 1903. What is aircraft? Aircraft is an object which is able to fly. What is airplane? Fixed wing aircraft with engine or engines (Heavier than air) which can fly in atmosphere because of aerodynamic forces generated by its wings.

What is Body? Body is a matter that is bounded by a closed surface. What are types of body? Rigid body Flexible body (or) Elastic body What is Rigid Body? I explain this with an example. Consider mobile phone. Now you choose any two points on your phone. Now you shake your phone. Does the distance between the assumed two points changed? It doesn’t. That means for a rigid body distance between its points or particles is held constant even though if they undergo any deformation. Practically the distance between particles will be changed. For a rigid body the value of deformation is negligible. What is Elastic body? For an elastic body, distance between the particles changes with respect to forces that it is subjected. 

What do you mean by equilibrium? Equilibrium is a state of rest of a body. Equilibrium equations also include the body moving with zero acceleration (uniform velocity) along a straight line. What is motion? When it will occur? Motion is change of position of a body with respect to time. To have a motion in any direction, the body should have an unbalanced force in the same direction. What is scalar? Give some examples Scalar is a physical quantity that contains only magnitude information. E.g. Mass, Time What is vector? Give some examples Vector is a physical quantity that contains both magnitude and direction information. E.g. Weight, Distance

What is Inertia? Inertia is a property of object through which it resists any change in its state. The  inability of a body to  change its state of rest or of uniform  motion by itself is called inertia. Newtons first law is more concerned with inertia and hence it is called as Law of inertia. What is mass? Mass is simply a measure of inertia. That means heavier bodies can resist forces (that are trying to deform its state) easily than a lighter body. The total number of atoms in an object determines the mass of the object. In SI unit mass is referred in Kg. Mass is a scalar. What is time? Time is a measure of duration between successive events occurring. In SI  system  of units time is measured in Seconds. Its a scalar.

What is space? Space is a region that extends in all directions. All bodies are within the space only. What is matter? Matter is any object that occupies some space. In the above illustration earth is a bigger matter. What is Particle? Particle has mass but no dimensions. So we can call a particle as point too.