Aircraft construction is a branch of mechanical engineering , traffic engineering . It includes the design, construction and testing of aircraft and , in some cases, their maintenance . The topic of aircraft construction also covers the construction of airships , helicopters , etc.
Industrial aircraft construction
Large aircraft are for the most part built in the dominant air yards of Boeing or Airbus . For medium and small series machines for commercial use, there are other manufacturers (Canadair, Bombardier, Ilyushin or earlier BAE Systems as well as the manufacturers of sports and business machines). All of these air yards, as well as their suppliers, require approval as a JA or JB company in accordance with international regulations (FAR / JAR).
The large traffic machines consist mainly of aluminum and increasingly of fiber materials. First of all, fuselage sections are manufactured, which are later made into fuselages. The riveting technique is still the most common connection technique, whereby the rivet must have a certain temperature when it is inserted. If the time between removal from the climate chamber and installation has been exceeded, these are discarded as scrap. The finished shell is called a “green plane” because of the color of the primer, although ready-to-fly green planes are sold as final equipment (e.g. Lufthansa Technik in Hamburg converts green 737s into business jets).
Before an aircraft can go into series production and receive its approval, various destructive and non-destructive tests (test flights) are required as well as numerous calculations, analyzes and simulations.
The tests to be carried out are specified in the ATP (Acceptance Test Procedure) and recorded in the ATR (Acceptance Test Report).
Each component sample must also pass qualification tests (often destructive testing).
After completing the qualification, there is then type approval.
Classification of aircraft
The aircraft construction iwS (coll., Actually aircraft construction ) deals with the construction, construction and design of aircraft of various kinds.
Usually, aircraft are initially divided according to their buoyancy principle. There are two basic categories:
- Lighter than air : In aircraft in this category, the lift is based on the Archimedes' principle , so the total weight is lighter than the amount of air displaced and the aircraft flies through static lift . The movement over the ground is called driving .
- Heavier than air : the total weight is heavier than the amount of air displaced. The buoyancy is generated according to Bernoulli's law . Aircraft in this category are usually referred to as aircraft i. e. S. designated.
To distinguish between aerospace and aerospace, the maximum altitude above ground is usually used as a classification criterion. While spacecraft can move outside of the atmosphere, aircraft that move within the atmosphere are called aircraft . Since the atmosphere does not have a strict height limit, a fictitious 100 km limit is generally used.
Constructive classification criteria
Constructive classification criteria, such as: B .:
- Drive technology:
- Wing type:
- Rotary wing aircraft : are motor-driven aircraft that generate lift through the reaction of one or more rotating rotors with the air (e.g. helicopter , gyroplane )
- Swing planes : also ornithopters , generate their lift by swinging the wings, analogous to bird flight
- Fixed wing aircraft : obtain their lift from fixed wings (e.g. glider , powered aircraft )
Further classification criteria
These can be:
- Number of wings: e.g. B. monoplane , one and a half decker , double decker , triple decker
- Wing arrangement: e.g. B. low-wing , middle-wing , shoulder-wing , high-wing
- Wing design: z. B. cantilevered, braced, single-stemmed, multi-stemmed and braced
- Landing type: z. B. Landplane , Seaplane , Amphibious Airplane
- Number of engines: z. B. One, two, three, four-engine are the most common types
- Propeller arrangement: e.g. B. tension screw , pressure screw , tension and pressure screw
There are also further classification criteria for aircraft, e.g. B. by weight, purpose or type of use. These can differ from country to country and, in addition to the type of aircraft, also affect the areas of certification, labeling and taxation (see in particular the classification of aircraft in the German LuftVG according to aircraft classes ).
Structural design of aircraft
Aircraft should be designed for their purpose as far as possible and also be safe and economical. Plus, payload and range are high on a designer's list.
Construction groups in aircraft construction
Aircraft are divided into three main design groups as well as the associated design groups.
- The airframe includes the supporting structure, i.e. the wings or a propeller (helicopter, gyrocopter ). Furthermore, the fuselage and the tail unit, to stabilize the flight characteristics, the control unit and the landing gear (sometimes also the landing gear in the case of helicopters) belong to the airframe. In the case of helicopters, there are also mechanical assemblies and the rotor blades.
- Engine installation
- Propeller systems and functional systems
- The equipment group primarily includes the instrumentation of aircraft, i.e. altimeters , airspeed indicators , radios , compasses , etc. Furthermore, aircraft can also be equipped with other safety or operational equipment. These include, for example, ejection seats or total rescue systems or, in the case of helicopter emergency equipment, cable winches or special measuring instruments.
The basic principle of all construction methods is the structure of the construction: The hull consists of frames , stringers and a cladding, which mostly consists of planking. The surfaces consist of a spar that holds the surface together on the transverse axis. On the spar there are ribs in the shape of a profile , which give and stabilize the shape of the surface. Four construction methods have prevailed since aircraft construction began. These are called:
With the wooden construction, the aircraft is made entirely of wood. The construction of the fuselage is made up of longitudinal straps , frames and plywood planking . Wooden aircraft are still being built in series, such as the Italian Pioneer 300 (see also Asso V ) or the French Robin DR 400 . Mainly, however, gliders were built from wood (for example the Schleicher Ka 6 ). Even with this type of construction, aircraft surfaces were partly covered with fabric.
In order to save as much aluminum as possible, the aircraft with the largest wingspan ever (97.51 m), the large flying boat Hughes H-4, was built from wood in 1942–1947 in the USA. The De Havilland DH.98 Mosquito, which was built in large numbers from 1940 to 1950, was also made of plywood.
The mixed construction combines the wooden construction with a metal tube construction. The metal tube construction mostly formed the fuselage, which was then covered. The surfaces were mostly made of wood. The composite construction is only rarely used in series these days. Aircraft in composite construction: K 8 , Piper PA-18 or current models: SF 25 “Falke” disc , M&D aircraft construction “ Samburo ”, Zlín “Savage”.
Fiber composite plastic construction
The fiber-composite-plastic construction is the construction method currently used for aircraft. With this type of construction, the aircraft is made of synthetic resin reinforced with glass or carbon fibers . Almost all components are made from this material. (Example GRP: glass wing Libelle , Grob G 115.Example CFRP: Schempp-Hirth Ventus )
A distinction is made between three construction methods. These describe the service life or fatigue strength of main construction groups and the reaction of the assemblies in the event of accidents. It tries to reach all destinations at the same time depending on the purpose of the aircraft. Depending on the purpose of the aircraft, one goal can be in the foreground: In the case of training aircraft, this would be the fail-safe philosophy, so that the aircraft largely forgives the pilot even gross control errors and remains in a stable attitude. In the case of aerobatic aircraft, however, this point is placed in the background in order to make the aircraft as manoeuvrable as possible.
Current research topics
Increased performance through more efficient cooling technologies in the turbine, development of new propeller / fan concepts (e.g. ducted propeller)
Airplane and economy
Components of the total cost
The following text explains the breakdown of the total cost of large commercial aircraft from the perspective of airlines.
The total costs are made up of the overhead costs and the individual costs . While the direct operating costs (DOC) can be assigned directly to a specific aircraft, this cannot be done with the indirect operating costs (IOC) (e.g. sales costs). In order to be able to make the total costs of commercial aircraft comparable, mostly only the DOC are used, which can be further subdivided, e.g. B. by distinguishing between variable and fixed cost components. The variable costs depend on the degree of aircraft usage (e.g. fuel costs). Fixed cost shares, on the other hand, are viewed as independent of the use of the device (e.g. insurance costs). The operating cost calculation is based on the aircraft being depreciated over a period of 12-14 years. Assuming constant annual depreciation amounts, a cost scenario can be drawn up for an operating period.
Total costs arise from:
- Financing or depreciation (fixed)
- Insurance (fixed)
- Crew (fix)
- Maintenance (variable)
- Fuels and supplies, i.e. operating costs (variable)
- Fees or charges (variable)
As a rule, the DOC calculation does not take into account the costs for on-board service loading. If you relate the annual DOC to the number of flights, you get the average costs per flight (trip costs) . If you continue to divide by the mean length of the route, you get the costs per kilometer. After dividing again by the number of passenger capacity, you get the unit costs DOC / SKO (SKO - Seat Kilometers Offered) . The unit costs decrease significantly with increasing flight distance.
There are several scheduled maintenance events for civil aircraft:
- Trip check: before each flight (takes about 30 minutes)
- Service check: weekly (takes about 20 hours)
- A-Check: every 250 flight hours (approx. Every 4 weeks)
- B-Check: every 900 flight hours (approx. Every 3 months)
- C-Check: every 3000 flight hours (approx. Every 12 months)
- IL check: first interval every 12500 flight hours (approx. Every 5 years)
- D-Check: First interval every 25,000 flight hours (approx. Every 9 years)
The information is only an example, there are aircraft types for which the manufacturer does not define a D-Check at all (e.g. Dassault Falcon 900 EX).
In most countries it is possible and also permitted to build a person-carrying aircraft yourself; these aircraft are then labeled “Experimental”. Three types have become established:
- Construction of a kit plane
- Build according to a purchased blueprint
- In-house development of an aircraft
Building a kit is the most common method. Advantage: The constructions are generally already tried and tested, with more or less prefabricated components an aircraft can be built in a manageable time frame, usually between 500 and 2000 hours. The kit manufacturer has taken over the procurement of materials. The cost of a kit airplane is between 50 and 80% of the price of a finished model.
When building according to a blueprint, you buy a plan from a designer, which you then use to build the aircraft. However, all components have to be manufactured or procured in-house. Depending on the construction, the time required is 1000–5000 hours, sometimes even longer. For many types of aircraft, only blueprints and no kits are available.
It is also possible to develop an aircraft in-house. However, for a beginner, this is not the usual way to get into aircraft construction. In theory, it is possible to build any object as an airplane if it can be demonstrated that the construct flies reliably and safely.
Building an aircraft yourself is only possible for private individuals. Series production is not allowed. A type certificate is required for this. After completion, the aircraft may only be operated for hobby purposes; commercial use is prohibited.
In Germany do-it- yourself aircraft is usually done by the Oskar Ursinus Association . This association supports the builder in technical and legal matters. Even with the Akaflieg aircraft are even built.
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