1 Aircraft Structural Components

The major aircraft structures 

are wings, fuselage, and empennage. The primary flight control surfaces, located on the wings and empennage, are ailerons, elevators, and rudder. These parts are connected by seams, called joints.

All joints constructed using rivets, bolts, or special fasteners are lap joints. Fasteners cannot be used on joints in which the materials to be joined do not overlap - for example, butt, tee and edge joints. A fayed edge is a type of lap joint made when two metal surfaces are butted up against one another in such a way as to overlap.

Internal aircraft parts are manufactured in four ways: Milling, stamping, bending, and extruding. The metal of a milled part is transformed from cast to wrought by first shaping and then either chemically etching or grinding it. A stamped part is annealed, placed in a forming press, and then re-heat treated.

Bent parts are made by sheet metal mechanics using the bend allowance and layout procedures. An extrusion is an aircraft part which is formed by forcing metal through a preshaped die. The resulting wrought forms are used as spars, stringers, longerons, or channels. In order for metal to be extruded, bent, or formed, it must first be made malleable and ductile by annealing. After the forming operation, the metal is re-heat treated and age hardened.

Airbus Wings

Here in the UK and in particular at the Airbus facility in North Wales, our expertise is in the manufacture of aircraft wings. Aircraft wings have to be strong enough to withstand the positive forces of flight as well as the negative forces of landing. Metal wings are of two types: Semicantilever and full cantilever. Semicantilever, or braced, wings are used on light aircraft. They are externally supported by struts or flying wires which connect the wing spar to the fuselage. A full cantilever wing is usually made of stronger metal. It requires no external bracing or support. The skin carries part of the wing stress. Parts common to both wing designs are spars, compression ribs, former ribs, stringers, stress plates, gussets. wing tips and wing skins.

Airbus at Broughton employs more than 5,000 people, mostly in manufacturing, but also in engineering and support functions such as procurement and finance.

Wing Spars

Two or more spars are used in the construction of a wing. They carry the main longitudinal -butt to tip - load of the wing. Both the spar and a compression rib connect the wing to the fuselage.

Compression Ribs

Compression ribs carry the main load in the direction of flight, from leading edge to trailing edge. On some aircraft the compression rib is a structural piece of tubing separating two main spars. The main function of the compression rib is to absorb the force applied to the spar when the aircraft is in flight.

Former Ribs

A former rib, which is made from light metal, attaches to the stringers and wing skins to give the wing its aerodynamic shape. Former ribs can be classified as nose ribs, trailing edge ribs, and mid ribs running fore and aft between the front and rear spar on the wing. Formers are not considered primary structural members.

Stringers

Stringers are made of thin sheets of preformed extruded or hand-formed aluminum alloy. They run front to back along the fuselage and from wing butt to wing tip. Riveting the wing skin to both the stringer and the ribs gives the wing additional strength.

Stress Plates

Stress plates are used on wings to support the weight of the fuel tank. Some stress plates are made of thick metal and some are of thin metal corrugated for strength. Stress plates are usually held in place by long rows of machine screws, with self-locking nuts, that thread into specially mounted channels. The stress-plate channeling is riveted to the spars and compression ribs.

Gussets

Gussets, or gusset plates, are used on aircraft to join and reinforce intersecting structural members. Gussets are used to transfer stresses from one member to another at the point where the members join.

Wing Tips

The wing tip, the outboard end of the wing, has two purposes: To aerodynamically smooth out the wing tip air flow and to give the wing a finished look.

Wing Skins

Wing skins cover the internal parts and provide for a smooth air flow over the surface of the wing. On full cantilever wings, the skins carry stress. However, all wing skins are to be treated as primary structures whether they are on braced or full cantilever surfaces.

Fuselage Assemblies.

The largest of the aircraft structural components, there are two types of metal aircraft fuselages: Full monocoque and semimonocoque. The full monocoque fuselage has fewer internal parts and a more highly stressed skin than the semimonocoque fuselage, which uses internal bracing to obtain its strength.

The full monocoque fuselage is generally used on smaller aircraft, because the stressed skin eliminates the need for stringers, former rings, and other types of internal bracing, thus lightening the aircraft structure.

The semimonocoque fuselage derives its strength from the following internal parts: Bulkheads, longerons, keel beams, drag struts, body supports, former rings, and stringers.

Bulkheads

A bulkhead is a structural partition, usually located in the fuselage, which normally runs perpendicular to the keel beam or longerons. A few examples of bulkhead locations are where the wing spars connect into the fuselage, where the cabin pressurization domes are secured to the fuselage structure, and at cockpit passenger or cargo entry doors.

Longerons And Keel Beams

Longerons and keel beams perform the same function in an aircraft fuselage. They both carry the bulk of the load traveling fore and aft. The keel beam and longerons, the strongest sections of the airframe, tie its weight to other aircraft parts, such as powerplants, fuel cells, and the landing gears.

Drag Struts And Other Fittings

Drag struts and body support fittings are other primary structural members. Drag struts are used on large jet aircraft to tie the wing to the fuselage center section. Body support fittings are used to support the structures which make up bulkhead or floor truss sections.

Former rings and fuselage stringers are not primary structural members. Former rings are used to give shape to the fuselage. Fuselage stringers running fore and aft are used to tie in the bulkheads and
former rings.

Aircraft Empennage Section

The empennage is the tail section of an aircraft. It consists of a horizontal stabilizer, elevator, vertical stabilizer and rudder. The conventional empennage section contains the same kind of parts used in the construction of a wing. The internal parts of the stabilizers and their flight controls are made with spars, ribs, stringers and skins.

Also, tail sections, like wings, can be externally or internally braced.

Horizontal Stabilizer And Elevator

The horizontal stabilizer is connected to a primary control surface, i.e., the elevator. The elevator causes the nose of the aircraft to pitch up or down. Together, the horizontal stabilizer and elevator provide stability about the horizontal axis of the aircraft. On some aircraft the horizontal stabilizer is made movable by a screw jack assembly which allows the pilot to trim the aircraft during flight.

Vertical Stabilizer And Rudder

The vertical stabilizer is connected to the aft end of the fuselage and gives the aircraft stability about the vertical axis. Connected to the vertical stabilizer is the rudder, the purpose of which is to turn the aircraft about its vertical axis.

Ailerons

Elevators and rudders are primary flight controls in the tail section. Ailerons are primary flight controls connected to the wings. Located on the outboard portion of the wing, they allow the aircraft to turn about the longitudinal axis.

When the right aileron is moved upward, the left one goes down, thus causing the aircraft to roll to the right. Because this action creates a tremendous force, the ailerons must be constructed in such a way as to withstand it.

Flight controls other than the three primary ones are needed on high-performance aircraft. On the wings of a wide-body jet, for example, there are as many as thirteen flight controls, including high and low-speed ailerons, flaps, and spoilers.

Flaps And Spoilers

Wing flaps increase the lift for take-off and landing. Inboard and outboard flaps, on the trailing edge of the wing, travel from full up, which is neutral aerodynamic flow position, to full down, causing air to pile up and create lift. Leading edge flaps - Krueger flaps and variable-camber flaps - increase the wing chord size and thus allow the aircraft to take off or land on a shorter runway. Spoilers, located in the center section span-wise, serve two purposes. They assist the high-speed ailerons in turning the aircraft during flight, and they are used to kill the aerodynamic lift during landing by spreading open on touchdown.

Trim Tabs

Connected to the primary flight controls are devices called trim tabs. They are used to make fine adjustments to the flight path of an aircraft. Trim tabs are constructed like wings or ailerons, but are
considerably smaller.

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1 Aircraft Interior Design And Its Significance

Style, sophistication and comfort are three crucial elements that define aircraft interior design. 

In the recent past, numerous researches and studies have been conducted on the aviation design technology but only a small fraction of scientific data is available that takes into account a passengers viewpoint. There have been innumerable passenger interviews and tour reports that have been used to collect the views about multiple aspects that requires to be improved so that an airplane as a comfortable as well as a stylish internal outlook.

Aviation interior designers of well known aero engineering services companies have been delving into minute details and nuances associated with the aircraft interior design and manufacturing. The capabilities of such organizations involve product design and certification assistance, side walls, ceiling panels, stowage panels and many more. These companies also specialize in multiple areas of aircraft cabin interior design and manufacturing.

The aircraft interior support solutions include a combination of interior design initiatives and assemblies that comprise of setting up certification documents. These companies have received accolades from around the globe for their immense contribution in the commercial aircraft and defense sector. 

Other services they offer include:

* Structural Analysis

* Detail Design

* Preliminary Stress Calculation

* Assembly Modeling

* Component Sizing

* Design Modification

* Interface Load Calculation & Substantiation

* DCN Incorporation

* Hand Calculations

* Installation Drawing

* FE Analysis

* Stress Justification Reports

Today aircraft interior design plays an essential role in the buying and selling of an airplane in the defense and commercial sector. 

This is because everyone today aims to have an aircraft whose function and maintenance quality are accurate. For a while, think of an airplane with innovative technology in the radio package, outstanding interior finish but the interior dcor and the arrangement is outdated. Selling such an aircraft would be tough. Furthermore, from a buyers perspective would you be able to look and judge beyond the essential interior dcor standards and concerns and buy an aircraft having other attributes perfect? It is true that other features and amenities are essential, but one should not overlook the value of the obvious. It is essential to notice that a passenger has to sit in the interior for a certain time period when he/she flies from one destination to the other.

In most cases, the aircraft interior design concerns can be resolved quickly. Today top notch aerospace engineering consultancy service companies have forayed into the market and have addressed aircraft design issues and other aero testing services.

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Successful aircraft maintenance depends on experienced extensively qualified employees, devoted to problem solving. Every aircraft requires maintenance checks from light, regular maintenance checks, to heavy periodical maintenance checks. Full technical support is what the operators seek.

Full technical support covers engines, airframes and modifications, components, landing gear changes and engineering. Modification, aircraft dismantling and storage can be included alongside aircraft maintenance.

Aircraft modification

Aircraft modification is primarily to improve older aircraft models through cost effective alteration works,including design and cabin furnishings & layout alterations. When offered as aircraft line maintenance it is part and parcel of supporting a fleet.

Approved line maintenance organisations

Any such work at outstations of an air carrier must be performed by approved maintenance organisations. A carrier is encouraged to apply for outstation line maintenance approval based on management by its main base. Equally, the maintenance organisation of a carrier is regarded as an independent organisation when it performs this work on aircraft that are not its own.
General servicing work is not regarded as line maintenance. Self-handling or entrusting to another company by agreement, the carrier submits application to its local civil aviation management organisation for line maintenance approval at outstations for specific aircraft under its maintenance agreement. A carrier's maintenance organisation takes full responsibility for compliance between maintenance at outstations and 145 requirements to the approved standards.

Airworthiness documentation provided by the aircraft manufacturer must be available onsite at outstations.

Line Maintenance agreements

If a carrier's maintenance organisation entrusts other companies to perform such work or release at an outstation, it has to sign a clear maintenance agreement with the contracted company. The maintenance agreement must include the following:

(1)Technical documentation, material, management procedures provided by the carrier
(2)Training instructions provided by the carrier;
(3)Work scope entrusted by the carrier and authorization instructions;
(4)Maintenance records and reporting methods.

A copy of all these must be kept at the outstation. A line maintenance organisation has full responsibility for compliance to 145 requirements and never performs work at locations out of maintenance certificate approval.

Organisations must have the tools & equipment necessary to perform work at locations listed in maintenance certificates, and special equipment belonging to the carrier by means of agreements.

The benefits of Line Maintenance Outsourcing

Line maintenance is seeing growth as more airlines, struggling with high fuel prices, see this as another area they no longer need in-house. New generation aircraft need outside maintenance specialists who can focus on high-tech entertainment systems, seating, galleys and lavatories.

The one qualification to this is the retirement of older aircraft, with replacement models that have longer specified intervals between inspections. As well as the high tech end, outsourced work will include cabin interiors, which is comparatively low-tech. When you consider repairing an armrest on a seat, for example, that is better outsourced, freeing up skilled mechanics for skilled activities.

Long-haul, widebody aircraft, operators offering a high degree of premium class services,legacy carriers, which typically operate large aircraft on long international flights, will start to shift more of their line work to third-party vendors. Line work has not been heavily outsourced to date, but overnight checks can be economically attractive offering efficiencies, without sacrificing operational performance.

Reciprocal carrier line maintenance contracts may be a casualty of these developments. High tech tasks will require additional training for people who work on some of the in-cabin systems, such as in-flight entertainment, galleys, lavatories and seating.

So, aircraft maintenance, including a comprehensive range of services from A checks and scheduled engine changes, through cabin cleaning and servicing, AOG service and total care programmes relating to cabin maintenance, particularly with respect to in-flight entertainment systems, on-wing engine support, LRU exchange programs and overnight checks with an efficient use of ground time, is the future. This future will be evolutionary, dictated by economics.

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