How to Control an Aircraft??

I am immensely happy with the response that i got with my first post.We have seen what makes an airplane fly from the previous post. Now that you've put some space between yourself and the ground, we need to control how the aircraft moves.

This leads to the concept of Axes of Motion.

They are:
1. PITCH
2. ROLL
3. YAW


Yaw is turning your plane left or right. Very similar to turning your bike towards left or right on the road.

Roll is turning the plane around its longer horizontal axis. Similar to bending the bike around the corners.

Pitch is moving the nose of the plane up or down. Comparable to doing a wheelie or a stoppie on a bike.



In the same way as the front wheels of your car or bike is used to turning and bending, there are mechanical parts on the surface of the plane that helps to move the plane in all the three axes of motion.








The three control surfaces that help the plane do the manoeuvres are


1. ELEVATORS
2. AILERONS
3. RUDDERS

Shown here is an A 10- Warthog with all the Control Surfaces.










Remember that Airflow over the plane's surfaces is a crucial part in its operation. When a control surface moves up,the fast moving air over the surface is slowed down. Think of Bernoulli's principle.. faster moving air over the surface, higher lift..slower moving air over the surface, lesser lift.

If any Control Surface is moved up,th air flowing over the surface is also forced to move up. The air that flows upwards creates a downward force at that point. Similar is the case with air moving downwards when the surface is tilted downwards.




The Pitch is provided by the ELEVATORS on the horizontal tail of the plane. When the elevator moves up or down,the plane also moves up or down.This is because the downward force
created by the airflow when the elevator is moved up. And the point at which this downward force is created is far back from the centre of gravity of the plane which makes the plane to pitch up.






Roll is provided by the AILERONS on both the wings. Both the ailerons are connected in such a way that if one of them goes up,the other moves down. When right aileron moves up,right wing has lesser lift while the left wing has higher lift because the left aileron counteracts. When left aileron moves up, left wing has lesser lift while the right wing has higher lift because the right aileron counteracts.Differences in the lifts produced by both the wings causes the plane to roll.






Yaw is provided by the RUDDERS on the vertical tail of the aircraft.When the air changes its direction towards left when flowing around the rudder, the force is exerted towards the right. Since the rudder is at the back of the plane and far from the centre of gravity, a yaw is produced. When the rudder tilts to the right, more lift is created on the right, which "lifts" or pushes the vertical stabilizer to the left. This, in turn, causes the airplane to yaw nose-right. The opposite motion occurs when the rudder tilts to the
left. Thus the counteracting force due to air changing directions and the lift produced cause the plane to yaw.


Control Surfaces that provide the Pitch,Roll and Yaw are called the Primary Control Surfaces(Red Colored).

Secondary Control Surfaces include the Tailwings(Horizontal Stabilizers),Flaps(Leading Edge and Trailing Edge) and Airbrakes(Spoilers).These are used along with the Primary Control Surfaces to perform complex manoeuvres and during take offs and landings.







As we can recollect, there are 6 types of control surfaces to be operated upon by the pilot. How does the pilot move all these surfaces then???

This is accomplished by the control yoke column which is usually at the centre of the cockpit and rudder pedals for the foot.

Moving the yoke sideways allows the pilot to do the Roll.Push the yoke left, the plane does a roll towards left.Push the yoke right, plane rolls right. Push the yoke front and the plane pitches down.Pull the oke back, the plane does a nose pitch up. back causes the plane to Pitch up or down. Since there are two Rudder pedals,i dont have to tell more about it !!

The Secondary Control Surfaces are operated by computers.These surfaces are usually present in the computer controlled aircrafts. Older planes never had these secondary control surfaces.

I have tried my best to explain the concepts in simpler terms as much as possible. Hope you guys enjoy reading this too :)