What is flap and slat ?

1. Flaps : It is secondary control surface . It is installed in trailing edge of  the wings towards in - board section of wing . At the time of landing and takeoff the aircraft speed is slow which can not produce sufficient lift to support the aircraft in air , according to lift formula with increase in co-efficient of lift or surface area of wing the lift increases . By extending the flaps it increases the surface area as well as camber of wing . Flaps are mainly used at time of landing but partially at the time of take off , because when flaps are full extended it produce more drag with little increase in lift .
   
2. Slats : It is also secondary control surface . It is installed in leading edge of the wing in outboard section of wing . It also used at the time of takeoff and landing  .It may be automatically operated or manually  operated . It extended in front of leading edge over the track . When it exdend it provied a slote between wing surface and itself to allow airflow from it . By allowing the air flow smoothly over the wing it energize the boundary layer by which it increases the velocity of air flow which increase the lift production .
   

What is aerofoil and its parts ?

Aerofoil : In American English its airfoil and in British English aerofoil   . It is a shape of  wing , blade ( of propeller , rotor or turbine ) . There are so many designs of aerofoil . The parts of aerfoil are as follows :

1. Chord line : It is imaginary straight line which connecting the leading edge and trailing edge . 
2. Camber line : It is curved line which divide upper camber and lower camber equally .
3. Leading edge : It is point at the front of the aerofoil  having maximum thickness . Some of control surface are present here also . 
4. Trailing edge : It is point at rear portion of aerofoil . Many control surface are installed in trailing edge  of the wing . 
5. Maximum thickness : It is maximum distance between the upper surface and lower surface of aerofoil . 
6. Maximum camber : It is maximum distance between the chord line and the camber line . 
7. Upper surface : It is upper curvature from the camber line of aerofoil . 
8. Lower surface : It is  lower curvature of aerofoil . 
9. Angle of attack : It is angle between the chord line of aerofoil to the relative air flow . 

Four forces acting on aircraft ?

1. Lift .
2. Drag . 
3. Weight .
4. Thrust .

When aircraft seting on ground only weight is act on aircraft but when aircraft during flight the all forces acting on it . During  take off the thrust force is more than drag force and lift force is more than weight force . In straight level UN-accelerated  flight the all forces are in equilibrium . 

1. Lift : It is a force acting vertically  upward to relative air flow . It is lifting force which lifts the aircraft in air . It is created because of pressure difference on wings . It over comes the force of gravity to lift the aircraft . 
2. Drag : It is a force acting opposite to the aircraft motion . It resist the forward motion of aircraft . To reduce the drag force the manufacture makes the aircraft in streamline shape . It causes because of air resistance . 
3. Weight : It is force acting vertically downward to the relative airflow . It is force of gravity which pull the aircraft towards earth . It cause because of mass of every thing which aircraft contains . 
4. Thrust : It is force which propels the aircraft in direction of motion . It is produced by engines, either it is jet engine or piston engine . It over comes the force of drag . 

Aircraft primary control surface ?

• Aileron 
• Elevator
• Rudder

• Aileron :  Aileron is control surface use to roll/bank the aircraft during flight . It installed in trailing edge outboard portion of the both wing . It controls lateral stability of aircraft . Rolling of aircraft performed on longitudinal axis . Ailerons are controlled by pilot from cockpit with the help of control yoke by rotating it . Some aileron also work as flaps called flaperons .                                                                                                          
• Elevator : Elevator is control surface use to control pitching movement ( climbing or diving ) of aircraft during flight . It control longitudinal stability of aircraft . It performed on lateral axis . Elevator are operated from cockpit with help of stick by pulling or pushing it. Elevator are installed in trailing edge of horizontal stabilizer of tail plane . When whole horizontal stabilizer surface is moves to control pitching movement is called as stabilator .                                                 
• Rudder : Rudder is control surface use to yaw/turn the aircraft during flight . It attach to trailing edge of vertical stabilizer , there may be multiple vertical stabilizer or rudder . It provide directional stability to aircraft along vertical axis . Some aircraft have ruddervator which combines the function of elevator as well as rudder . Rudder are control from cockpit with the help of rudder pedal .  
  

Aircraft three main parts ?

1. Fuselage .
2. Main plane/Wings .
3. Tail plane/Empennage .

1. Fuselage : Fuselage is aircraft's main body section which holds the passenger , crew and cargo . In single engine aircarft in which engine attach to fuselage so it also hold the engine .                                                        
   
                             
2. Main plane/ wings : Wings are aerofoil shape surface use to support the aircraft in flight . There are various designs , shapes and size used by aircraft manufacturers . There are three arrangements of wings such as  high wing , low wing ang middle wing . it is attach to the fuselage . 
   
3. Tail plane / empennage : It is the rear portion of aircraft which include stabilizer , elevator and rudder . In triple engine aircraft it include engine also . Yawing  and pitching control are present in it . 
   

Types of aircraft ?

Lighter than air aircraft : They use buoyoncy to float in air like ship floating on water . In which gasbags or canopies , filled with low density gas such as helium , hydrogen , hot air . In which the lift produce is called as aerostatic lift  because it works on differance in density in atmosphere to  inside gasbags or canopies . examples are airship , balloon and kites . 

Heavier than air  aircraft : They use wings to support in air by creating pressure differance on wings . they work on bernaulli's principle as well as on newton's third law of motion . They may be fixed wing or rotary wing aircraft . In which lift produce is called as aerodynamic lift because it not works on buoyoncy of air . the examples are glider , aeroplane , helicopter sailplane etc . 

What is aircraft ?

Aircraft means any machine that can derive support in the atmosphere from the reaction of the air other that reactions of air against the earth's surface by compensiating the force of gravity .
The support produce is called lift . It acts perperpendicular to the relative air flow .