𝗔 𝗦𝗛𝗢𝗥𝗧 𝗚𝗨𝗜𝗗𝗘 𝗧𝗢 𝗖𝗢𝗡𝗧𝗥𝗢𝗟 𝗦𝗨𝗥𝗙𝗔𝗖𝗘𝗦

 

A SHORT GUIDE TO

CONTROL SURFACES

Have you ever seen those weird rectangular surfaces on the top of the wing deploy after landing? They are spoilers, a type of control surfaces. What are control surfaces? Have you ever wondered about their functionality? Are they essential on planes?

Well, you have come to the right blog for this!

Some of the control surfaces include ailerons, elevators and a rudder, however, in delta-winged aircraft, the ailerons and elevators are merged to form elevons. However, we must not rush, and cover each of the topics slowly.

Let’s begin!

What are ailerons?

Right Wing Aileron

There is a pair of ailerons present on a plane, usually located on the outward trailing edge of each wing. They are used to control the roll of the aircraft- for example rolling to the left requires the left aileron to tilt upwards, deflecting some air up from the left wing, thus pushing the left wing downwards, while the right aileron is required to tilt downwards, deflecting some air down from the right wing, effectively pushing the right wing up.

Ailerons are required to maintain the roll control of the aircraft. But why are they necessary? Let us take a plane without ailerons.

If a gust of wind hits the plane, it may alter the roll of the plane by a little. But over time, the roll angle continues to increase until the plane reaches the maximum bank angle, loses lift, stalls and crashes. We can clearly see how important ailerons are in a plane.

Think it out- Why don’t we want to lose ailerons, especially in a Sopwith Camel?

Hint: It has a rotary engine which rotated clockwise.

(Check the end for the answer, but don’t forget to guess.)

What are elevators?

Elevators on the Cessna Skyhawk

There is a pair of elevators on a plane, usually located on the trailing edge of the Horizontal Stabilizer. The elevators control the pitch of the aircraft. For example, to pitch the plane up, the elevator tilts upwards, deflecting wind upwards and thus pitching the tail down, resulting in the nose pitching up. To pitch the plane down, the elevator tilts downwards, deflecting wind downwards and thus pitching the tail up, resulting in the nose pitching down.

Thus, the elevators are essential for maintaining the pitch control of the aircraft. The elevators are usually attached to each other, and they cannot move independently, unlike ailerons. But why are they necessary?

If a plane had no elevators, it wouldn’t be able to climb at all. It would keep accelerating on the runway, overshoot it, and crash. If a plane lost its elevators mid-flight, it would not be able to pitch up or down. If its nose pitched up by any chance, it wouldn’t be able to level off, and the pitch of the aircraft will continue to increase, until it stalls out and crashes.

 

 What is the rudder?

The rudder of a Thai Airways A321 Neo

The rudder is located on the trailing edge of the Vertical Stabilizer. It is responsible for the yaw control of the aircraft. To yaw the plane left, the rudder tilts left, deflecting air to the left and thus yaws the plane to the left. To yaw the plane right, the rudder tilts right, deflecting air to the right and thus yaws the plane to the right.

Rudders are necessary for maintaining yaw control of the aircraft. But why are they necessary?

If a plane had no rudder, the only way for it to turn would be banking and pulling up. However, that is not an option during takeoff or landing. If a plane encountered crosswinds during landing, it would not be able to correct its heading. Since turning would require a bank, it could suffer a wingstrike on the runway, which could have severe consequences. 

We have completed all the main control surfaces, but what about elevons?

Well, we will cover it now, and also go over some intermediate surfaces.

 

 What are elevons?

The elevons of a Concorde

Elevons are only present in delta-winged aircraft, and there are a pair of them present. They are present on the trailing edge of the delta wing. They perform the role of both ailerons and elevators, i.e., they are responsible for both pitch and roll control of the aircraft. They provide extra lift to a supersonic aircraft when they are in the downward position, but they also pitch the nose downwards. They are usually present in delta-winged combat aircraft, although the Concorde and Tupolev Tu-144 also had them.

Intermediate surfaces (If you read the above information, you may not read this part since you already have a basic understanding of the main control surfaces, this just provides some extra information)

Intermediate Control Surfaces

What are flaps?

Flaps are present on the trailing edge of an aircraft wing. They help to generate extra lift at low speeds and therefore are useful during takeoff and landing. They are retracted during cruise and are deployed during takeoff and landing.

What are slats?

Slats are similar to flaps, but they are present on the leading edge of the wing. The slats help reducing the stall speed of the aircraft, and is retracted during cruise. They are deployed during takeoff landing.

What are flaperons?

Flaperons are a combination of flaps and ailerons and they help provide roll control of the aircraft at low speeds. The flaperons are present between the flaps and ailerons on commercial planes.

What are spoilers?

Spoilers are present on the top of the wing. They disrupt the airflow over the wing and thus reduces the lift. They are only deployed during landing.

What are airbrakes?

Airbrakes can be present in various places in various planes. For example, it is present at the back of the fuselage in the Avro RJ100. It is used to slow down the aircraft after landing. In military aircraft, they are used to achieve a higher descent rate if needed.

 

 Answer to Think it out: -

The Sopwith Camel was a World War 1 era biplane manufactured by Sopwith Aviation Company. According to Newton’s Third Law of Motion, every motion has an opposite reaction. Therefore, as the engine rotated clockwise, the plane tended to roll anti-clockwise. Therefore, the pilot had to apply constant pressure on the stick to keep the plane level. The plane would start rolling and enter a spin if their ailerons were shot off. Therefore, the Sopwith Camel required skilled pilots to fly it. The ailerons were absolutely necessary on the Sopwith Camel.

 

Proof of Concept: -

This will be a new section on some of my Blogs, I hope you enjoy it!

To support my opinions, I will show a few videos of a paper plane with rudders and elevons (since most paper planes are delta-winged). 

Instructions - To add elevons on a paper plane, cut a slit about 1 cm from the spine on the trailing edge of each wing. Carefully fold it to form moveable rectangles on the outer trailing edge of each wing. Now, all you have to do is to adjust the angles of the elevons to get different results. To predict the outcomes, read the section about elevators and ailerons. Combine the knowledge to predict the outcomes of various elevon positions. When the elevons are angled upwards about 8°,the plane offers excellent low speed performance- Never angle it to more than 10°,as it may result in the plane stalling. Angling it downwards will probably cause it to nosedive in delta-winged paper planes, but if you find the golden number (different for each plane), you can cause them to work as flaps, however this works only when the plane has a parallel chord wing or close to that, as angling the elevons downwards will just cause the plane to nosedive and crash, at quite high speeds.

A plane with neither elevon input nor rudder input

A plane with left rudder input. Notice its tendency to bank to the left

A plane with up elevator input. Notice the tendency of its nose to pitch up.

If you liked the style of this blog, please leave a comment.

 Links to my other Blogs: -

A SHORT GUIDE TO WINGLETS

A SHORT GUIDE TO GO-AROUNDS