Do you remember the time when you first rode a bike? Or the time when you first learnt to drive a car? What did the instructor tell you in the very beginning? “This here, is the steering wheel, those are the pedals for brakes, clutch and race, and these are the gears.” used to explain the instructor. An aircraft is no different- although one needs to have balls of steel to be in a piece of metal (composite fibres nowadays) that travels at the speed of sound at 20000 feet. It too, has got controls, until Elon Musk jumps into aviation, which I pray he never does.
Before jumping to the controls, let us talk about the three ways in which an airplane can maneuver in the air.
- Roll- Rotation of an aircraft about the longitudinal axis (imaginary line that joins the nose to the tail of the aircraft)
- Pitch- The up and down motion of an aircraft’s nose is called the pitching motion.
- Yaw- The left and right movement of an aircraft about its vertical axis (an imaginary line cutting the aircraft in the vertical plane and passing through its centre of gravity.)
Basically, aircrafts have two types of controls- primary controls and secondary controls, which respectively operate the primary control surfaces and the secondary control surfaces. If we take a car analogy here, primary control is the brake pedal, and the primary control surface is the brake itself.
- Control Stick – It is similar to a joystick. (a device with which the 90s kids used to play.) It controls two primary surfaces- Ailerons and the Elevators. Moving the stick in left-right direction facilitates the rolling motion, and moving it fore and aft controls the pitching motion.
- Rudder pedals – These are similar to the clutch and brake pedals of a car and are placed in front of the pilot near the foot rest. These control one primary surface- the Rudder, which facilitates the yawing motion of an aircraft.
- Throttle – In most of the aircrafts, this is in the form of a handle, which when pushed farther from the pilot, increases the engine RPM, increasing the forward thrust of the aircraft, and when pulled closer to the pilot, they decrease the RPM, reducing the thrust produced by the engines. These are analogous to the race pedal of a car. Interesting fact- Technologically advanced aircrafts have the facility to reverse the thrust too, which can be used to reduce speed of an aircraft on the ground.
Primary Control Surfaces:- If you ever get a chance, sit on the window seat of the aircraft during a flight. Notice carefully, the wings during the entire flight. You’ll see that the wings seem to be broken, and parts of it to be attached to the main body using hinges. Those actually are no broken parts, but are deliberately kept that way for facilitating control of the aircraft. Those broken, or I’d say, hinged surfaces are called the control surfaces. Primarily, these are of three types-
- Ailerons – These are hinged on the rear end of both the wings of an aircraft and are placed away from the fuselage, towards the wingtips. These move in opposite directions which means, if the aileron on the right side moves up,the one on the left will move down, and vice versa. These control the rolling motion of an aircraft and are operated by the sideways movement of the control stick.
- Elevators – These are hinged on the rear end of the vertical stabilizer of an aircraft (a part of the tail plane of the aircraft). These move in a definite direction, either both the elevators go up, or both of them go down. They control the pitching motion of the aircraft (nose up or nose down), and are operated by the fore and aft movement of the control stick.
- Rudder – It is hinged on the rear end of the horizontal stabilizer (a part of the tail plane of the aircraft). It moves left or right providing yawing (sideways) motion to the aircraft, and is controlled by the rudder pedals. Pushing the right rudder pedal will move the aircraft to the right side, and vice versa.
Secondary control and secondary control surfaces:- These are seldom found in microlight aircrafts, and are basically used to facilitate easy flying of an aircraft. There are many types of secondary control surfaces, let us discuss the two most important ones- Flaps and Slats
- Flaps – These are hinged to the rear end of the wings of an aircraft near the fuselage, and are used to provide additional lift to the aircraft. They are generally operated using flap levers. These are mostly used during takeoffs and landings, when lift is needed at relatively lower speeds. Lesser length of runway is required for takeoff/landing in aircrafts equipped with flaps, since the requisite lift is provided by flaps at lower speeds. They also play one more important role- increasing drag on the aircraft : which is essentially required to land the aircraft and decrease their landing roll. Different aircrafts have different flap configurations, let me stay focussed on the aircraft that I’ve flown in- the Virus Microlight. It has three flaps configurations- 0 deg, 15 deg, 25 deg. The 0 deg configuration basically shows that the flaps are currently in the same geometrical plane as the wings, and therefore are not under use. The 15 deg position basically shows that the flaps are at an angle of 15 degrees with the chord line of the aerofoil, and is essentially used during takeoff, to produce high lift at slower speeds(decreasing runway length). The 25 deg position is normally used during the landing to increase the drag on the aircraft, and land it safely and gently using shorter runway distances.
- Slats – These are aerodynamic surfaces attached to the leading edge of the wings of an aircraft. These too are retracted and deployed by pilots mostly during takeoffs and landings, just like flaps. The Automated variant of slats use a spring mechanism to automatically bulge out during low speeds, or flush in during high speeds. During takeoffs and landings, they provide the aircraft with more lift at lower speeds for a gentle and easy climb. They also allow the aircraft to operate at higher angles of attack(prevention of stall). They are mostly used to decrease takeoff and landing distances just like flaps. If deployed in-flight, they increase the drag on the aircraft.
We have talked and discussed pretty much in detail, about various controls in an aircraft- both primary and secondary. Although an aircraft is not easy to fly, and just the knowledge of the controls explained above won’t make you an aviator, it will still count in case you are an aviation enthusiast like me, who thrives for more and more vis a vis flying. Signing off for the day, it was a pleasure to write for you. Jai Hind.