Aerodynamics Factors

 Aerodynamics

Several factors affecting on airplane performance. Such as  atmosphere, aerodynamics and aircraft icing.

But aerodynamics  is most important factor. We knowing about what is aerodynamics? Whats importance of aerodynamics knowledge for pilot? 

 

The Wing

To  knowing about  aerodynamic  forces,  a  pilot  must  to understand  basic  terms  related  with  airfoils.

You know about aerofoil?

The aerofoil have six main parts.

1. Leading Edge
2. Trailing Edge
3. Uper Camber
4. Lower Camber
5. Maen  Camber Line
6. Mean Cord Line

Leading Edge:

  The front edge of an airplane propeller blade or wing.

Trailing Edge:

  The rearmost edge of a moving structure, such as an airfoil. the back edge of a propeller blade or aerofoil Compare leading edge.

Upper/ Lower Camber

The camber of an aerofoil can be defined by a camber line, which is the curve that is halfway between the upper and lower surfaces of the aerofoil.

 Chord Line

The  chord  line  is  the  straight  line  intersecting  the  leading  and trailing edges of the airfoil, and the term chord refers to the chord line longitudinal length (length as viewed from the side).

Mean Camber Line

The  mean  camber  is  a  line  located  halfway  between  the upper and lower surfaces. Viewing the wing edgewise, the mean camber connects with the chord line at each end. The mean camber is essential because it assists in shaping aerodynamic  qualities  of  an  airfoil. 

The  measurement  of the maximum camber; inclusive of both the displacement of the mean camber line and its linear measurement from the  end  of  the  chord  line,  provide  properties  useful  in evaluating airfoils.

Review of Basic Aerodynamics The  instrument  pilot  must  understand  the  relationship and differences  between  several  factors  that  affect  the performance of an aircraft in flight. Also, it is crucial to understand  how  the  aircraft  reacts  to  various  control  and power changes, because the environment in which instrument pilots fly has intrinsic hazards not found in visual flying. The basis for this understanding is found in the four forces  acting on an aircraft and Newton’s Three Laws of Motion. Relative Wind is the direction of the airflow with respect to an airfoil.  Angle  of  Attack  is  the  acute  angle  measured  between  the relative wind, or flight path and the chord of the airfoil.

What is  Basic Aerodynamics?

The  instrument  pilot  have to  knowing  the  link  and  differences  between  a number of  factors  that  involve  the performance of an aircraft in flight. Also, it is vital to understand  how  the  aircraft  reacts  to  various  control  and power changes, because the environment in which instrument pilots fly has inherent hazards not found in visual flying. The basis for this understanding is found in the four primary forces acting on an aircraft and Newton’s Three Laws of Motion.Relative Wind is the direction of the airflow with respect to an airfoil. Angle  of  Attack  is  the  acute  angle  measured  between  the relative wind, or flight path and the chord of the airfoil. Flight path is the course or track along which the aircraft is flying or is intended to be flown. 

 

The Four Forces

The four basic forces  acting upon an aircraft in flight are

1.  Lift
2. Weight
3. Thrust
4. Drag

Lift

Lift  is  a  factor  of  the  total  aerodynamic  force  on  an airfoil and acts perpendicular to the relative wind. Relative wind is the direction of the airflow with respect to an airfoil. This force acts straight up from the average (called mean) center of pressure (CP), which is called the center of lift. It should be noted that it is a point along the chord line of an airfoil through which all aerodynamic forces are considered to  act.  The  magnitude  of  lift  varies  proportionately  with speed, air density, shape and size of the airfoil, and angle of attack. During straight-and-level flight, lift and weight are equal.

Weight

Weight is the force exerted by an aircraft from the pull of gravity.  It  acts  on  an  aircraft  through  its  center  of  gravity (CG)  and  is  straight  down.  This  should  not  be  confused with the center of lift, which can be significantly different from the CG. As an aircraft is descending, weight is greater than lift.

Thrust

Thrust is a force that drives an aircraft through the air and can be measured in thrust and/or horsepower. It is a component that  is  parallel  to  the  center  of  thrust  and  overcomes  drag providing the aircraft with its forward speed component.

Three rotation axes

All maneuvering takes place approximately three axes of rotation. One way to define these axes is a Cartesian coordinate system with

• An x axis from left to right,
• A y-axis from top to bottom,
• And a z-axis from near to far.

Your viewing angle within this plane is called the heading, whereas an orthogonal angle is called the elevation. But we can also define three axes of rotation referring to our fighter. They are known as the longitudinal axis, lateral axis, and vertical axis. Imagine a coordinate system with the origin at your fighters center of gravity. The center of gravity is the theoretical point where the entire weight of the aircraft is considered to be concentrated.

The lateral axis is an imaginary axis protruding through the side of the aircraft. A rotation around this axis is known as pitching. This pitch movement is produced by the elevators and will affect your heading and elevation. The longitudinal axis is an imaginary axis protruding through the nose of the aircraft. A rotation around this axis is known as a roll. This roll movement is produced by the ailerons. Consider that a roll will not change your heading. And finally the vertical axis is an imaginary axis protruding through the top and bottom of the aircraft. A rotation around this axis is know as yawing. This yaw movement is produced by the rudder.

 Drag

Drag  is  the  net  aerodynamic  force  parallel  to  the  relative wind  and  is  generally  a  sum  of  two  components:  induced drag and parasite drag.

Induced drag

Induced drag is caused from the creation of lift and increases with angle of attack. Therefore, if the wing is not producing  lift, induced drag is zero. Conversely, induced drag decreases with airspeed.

Parasite drag

Parasite drag is all drag not caused from the production of lift.  Parasite  drag  is  created  by  displacement  of  air  by  the aircraft, turbulence generated by the airfoil, and the hindrance of airflow as it passes over the surface of the aircraft or

components.  All  of  these  forces  create  drag  not  from  the production of lift but the movement of an object through an air mass. Parasite drag increases with speed and includes skin friction drag, interference drag, and form drag.

Skin Friction Drag

Covering the entire “wetted” surface of the aircraft is a thin layer of air called a boundary layer. The air molecules on the surface have zero velocity in relation to the surface; however, the  layer  just  above  moves  over  the  stagnant  molecules below  because  it  is  pulled  along  by  a  third  layer  close  to

the free stream of air. The velocities of the layers increase as the distance from the surface increases until free stream velocity is reached, but all are affected by the free stream.

The distance (total) between the skin surface and where free stream velocity is reached is called the boundary layer. At subsonic levels the cumulative layers are about the thickness of a playing card, yet their motion sliding over one another creates  a  drag  force.  This  force  retards  motion  due  to  the viscosity of the air and is called skin friction drag. Because skin friction drag is related to a large surface area its affect on  smaller  aircraft  is  small  versus  large  transport  aircraft where skin friction drag may be considerable.

Interference Drag

Interference drag is generated by the collision of air streams creating eddy currents, turbulence, or restrictions to smooth flow. For instance, the airflow around a fuselage and around the wing meet at some point, usually near the wing’s root. These air flows interfere with each other causing a greater drag than the individual values. This is often the case when external items are placed on an aircraft. That is, the drag of each item individually, added to that of the aircraft, are less than  that  of  the  two  items  when  allowed  to  interfere  with one another.

Form Drag

Form drag is the drag created because of the shape of a component  or  the  aircraft.  If  one  were  to  place  a  circular disk in an air stream, the pressure on both the top and bottom would be equal. However, the airflow starts to break down as the air flows around the back of the disk. This creates turbulence and hence a lower pressure results. Because the total pressure is affected by this reduced pressure, it creates a drag. Newer aircraft are generally made with consideration to this by fairing parts along the fuselage (teardrop) so that turbulence and form drag is reduced.Total lift must overcome the total weight of the aircraft, which is comprised of the actual weight and the tail-down force used to control the aircraft’s pitch attitude. Thrust must overcome total drag in order to provide forward speed with which to produce lift. Understanding how the aircraft’s relationship between these elements and the environment provide proper interpretation of the aircraft’s instruments.

Newton’s First Law, the Law of Inertia

Newton’s First Law of Motion is the Law of Inertia. It states that a body at rest will remain at rest, and a body in motion will  remain  in  motion,  at  the  same  speed  and  in  the  same direction until affected by an outside force. The force with which a body offers resistance to change is called the force of inertia. Two outside forces are always present on an aircraft in flight: gravity and drag. The pilot uses pitch and thrust controls  to  counter  or  change  these  forces  to  maintain  the desired flight path. If a pilot reduces power while in straight-and-level flight, the aircraft will slow due to drag. However, s the aircraft slows there is a reduction of lift, which causes the aircraft to begin a descent due to gravity. [Figure 2-4]

Newton’s Second Law, the Law of Momentum

Newton’s Second Law of Motion is the Law of Momentum, which states that a body will accelerate in the same direction as  the  force  acting  upon  that  body,  and  the  acceleration will be directly proportional to the net force and inversely proportional  to  the  mass  of  the  body.  Acceleration  refers either  to  an  increase  or  decrease  in  velocity,  although deceleration is commonly used to indicate a decrease. This law governs the aircraft’s ability to change flight path and speed, which are controlled by attitude (both pitch and bank) and  thrust  inputs.  Speeding  up,  slowing  down,  entering climbs or descents, and turning are examples of accelerations that the pilot controls in everyday flight.

Newton’s Third Law, the Law of Reaction

 

Newton’s Third Law of Motion is the Law of Reaction, which  states  that  for  every  action  there  is  an  equal  and opposite  reaction.  As  shown  in  fig the  action  of the jet engine’s thrust or the pull of the propeller lead to the reaction  of  the  aircraft’s  forward  motion.  This  law  is  also responsible for a portion of the lift that is produced by a wing, from the downward deflection of the airflow around it. This downward force of the relative wind results in an equal but opposite (upward) lifting force created by the airflow over the wing.