Aircraft Wing

In this tutorial, you will learn the basics of wings of an aircraft which include its definition, classifications, and its working details. You will also learn about the unique differences between Semi-cantilever and cantilever structures along with Wing Construction processes.

Contents:

1. What is a Wing?
2. Methods of Wing Attachment
3. Basic Features of Wing Construction
4. Cantilever vs Semi-cantilever
5. Stressed Skin Metal Construction
6. Fuel Tanks Arrangement
7. Transport Aircraft Wings
8. The Internal Structure of a Modern Transport Wing

What is a Wing?

The Aircraft Wing is a type of Airfoil that produces the maximum amount of lift to an Aircraft structure for its lateral stability.

• The Aircraft wing is attached, both vertically and horizontally in three different attachments and they are high-wing, low-wing & mid-wing respectively. Based on wing design, it is classified into two types such as cantilever and semi-cantilever.
• A cantilever type of wing structure does not require any kind of external bracing. This type of structure already has all the structural strength and it is found with high-performance in many transport Aircraft.
• Whereas in a semi-cantilever type of wing structure, it acquires strength by both external bracings from struts, wires, and internal support structures to provide high-speed performance. This type of wing design is rarely found in heavier aircraft and mostly found in lighter aircraft.
• To withstand operational stresses, all the wings must be equally spaced and must contain spanwise members of extraordinary strength. The operational stresses are maximum during flight and also upon landing.
• The cost and maintenance of the building of an Aircraft have an impact on the wing design. The Airplane wing design is stable because of the perfect balance of cost, performance, and fabrication techniques with overall strength and weight criteria.

Methods of Wing Attachment

The wings are attached to the Aircraft in a variety of locations both vertically and longitudinally such as high-wing, mid-wing, and low-wing respectively.

• High-wing: The aircraft with a high wing has its wings mounted above the fuselage structure. And the high-wing type usually gives excellent ground clearance when compared to other types.
• Mid-wing: The mid-wing aircraft has its wing portion attached to the mid-portion of the fuselage structure and it uses a symmetric type of airfoil which increases the, range of angle of attack and also avoids spin-stall.
• Low-wing: In a low-wing aircraft, the wing is attached below the fuselage structure and it is observed to show some dihedral.

The following diagram describes the methods of wing attachment:

The above diagram shows the three different types of wing attachments in the fuselage structure which is mounted above, below, and on the mid-portion of the aircraft that shows different performances according to its varied positions.

Basic Features of Wing Construction

The basic features of wing construction are as follows:

• Generally, there are three types of wing structures in conventional aircraft. They are: monospar, two-spar, and multispar.
• The mono spar wing has a single spar element, it is in the midpoint of the chord line of the airfoil.
• The two-spar wing has two spar elements, and one of the spars is located in the leading edge and the other in the rear of the wing.
• The multi-spar wing has two or more spar elements, which increases the overall strength of the aircraft wing structure.
• The wing spar is also called a wing beam and it is the most significant spanwise member of the wing structure. The spar also includes different attachment points in the wing cross-section. The wings of a semi-cantilever design include strut fittings in the midpoint along with the spar.
• Wing ribs or plain ribs transmit the air loads, from the external covering to the spars. To give shape for the wing structure, the ribs are usually spaced at proper intervals along the wingspan. Ribs keep the spars stable against the twisting force and also behave like formers in holding the airfoil’s shape firmly.

The above diagram shows that there are three principal types of fuselages, which have their specifications and vary according to the size and shape of the aircraft. The diagram tells us that, the truss-type is further divided into two major types and they are Pratt truss and Warren truss.

Cantilever Wing vs Semi-cantilever Wing

The following table describes the difference between a cantilever and a semi-cantilever.

Stressed Skin Metal Construction

In this type of metal construction, the skin of the wing structure is riveted to the ribs and stringers. It serves as the basic structure of the wing.

• The Aluminium skin is the predominant load carrying member and has high strength and it is used in most aircraft. The stressed metal skins are very strong and balance the aerodynamic shape.
• Stiffeners or stringers are the members, that help to hold the better aerodynamic shape of the wing structure. It is directly attached to the skin. These are closely spaced on the upper part of the wing structure.
• The stiffeners are the support system, for the entire wing structure as the upper part is normally in compression. By stiffening the compression skin, it helps in resisting the bending loads induced on it.
• It is necessary to make openings in the wing skins for service purposes, these openings weaken the wing structure and decrease the ability to resist twists. So, around the cutout’s doublers are required.

Fuel Tanks Arrangement

The fuel tank is generally located on the internal portion of the wing structure.

• The fuel tank can also be a removable metal container, an integral fuel tank, or a bladder-type fuel tank in a compartment. In a removable tank, the tank is held between spars and ribs and it is usually made up of metal.
• Bladder fuel cells are placed in structurally strong wing areas, which are usually between the spars. These bladder tanks are rubber-like bags, for installation and removal of the wing it does not have large openings.
• The bladder tanks are worked on small openings on the wing surface. So, as to install and remove by rolling the bladder tanks efficiently.
• Integral tanks are usually built along with the basic wing structure which cannot be removed. The forward main spar and the internal section of the wing are secured together to form the fuel bay.

Transport Aircraft Wings

The modern transport aircraft wing consists of ribs, bulkheads, spars, and skin panels with spanwise stiffening members.

• The assembly of the structure includes non-metallic composite components and bonding metal structures along with conventional metal alloys and fasteners. The wing structure must be strong enough to withstand its weight, fuel tank’s weight, engine’s weight, and the forces imposed on it.
• The stresses imposed on the wing structures extremely vary both in magnitude and direction during aircraft transitions. The transport wing design consists of two or more main spars with intermediate spars used in between the main spar structures.
• These intermediate spars help in assisting the main spar while carrying the operational loads imposed on the wing structure. The main supporting structures for the fuselage attachments are the front and the rear spars respectively.
• The wingtips, leading-edge, and trailing edge are the auxiliary structures of the wing. The leading edge of the wing includes the leading-edge ribs, structurally reinforced members, and the component attachment points such as leading-edge flaps and slats. Similarly, the trailing edge also incorporates many structural members for various points of attachment.

The following diagram describes the components of the transport aircraft wing structure:

The above diagram shows, the different components of the transport aircraft wing structure that includes spars, ribs, bulkheads, skin panels, and stiffening members in the mainframe of a modern transport wing.

Internal Structure of a Modern Transport Wing

To achieve the desired structural strength of the wings, the internal structure of the wing is covered with large metal skin panels and also has spanwise stringers attached to it.

• Permanent type fasteners are attached to the leading edge and trailing edge. For inspection and maintenance purposes, the wingtips are removable.
• The wing construction is in three or four assemblies such as left-wing panel, right-wing panel, and center-wing section respectively. These are all held together with permanent fasteners to form a one-piece wing that is attached to the fuselage.
• The fuselage, main landing gear, flight control surfaces fittings that are attached to the wings are secured with interference-fit and close-tolerance fasteners. These fittings are only removable for structural repair.
• An interference-fit fastener is a rivet pin or bolt which is smaller than the hole in which it is installed, as a result, there is no clearance between the fastener and the installation. Hence, it is affected by expansion or contraction due to the temperature changes on it.
• In a basic wing structure, a fuel tank is included. So, that the wing serves as a fuel tank. Hence, it is called an integral fuel tank design or a wet wing. In an integral tank design, the fasteners are applied and sealed with special compounds, and the areas where the fuel tanks are absent are called dry bays.