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Design of Aircraft Interior Swen I. Scha~ch* FUNCTIONS AND PERFORMANCES OF Al:RCRAw INTERIOR Means of transport serve not only to convey passengers from a place of departure over a certain distance to a place of destination. During the time of travel, further functions and performances must be performed: accommodation in passenger cabin; protection of passengers from harmful impact; serving of food; removal of waste, etc.; and entertainment. With respect to these~further functions, special demands are made on commercial aircraft. Because of the high cost of investment, the operators aim to put the aircraft to maximum use. This is achieved by the adaptability of the means of transport and a wide range of services offered. However, the scope of variation is considerably restricted by specifications meeting physical, economic-technical, and safety requirements. In a way that does not apply to any other means of transport, the weight of the aircraft is of paramount importance in economic considerations. Where air traffic is concerned, a particularly carefu! comparison of the required expenditure with the expected benefit is therefore called for. The interior furnishing of Airbus cabins includes all components that are insured between the dividing wall to the cockpit and the pressure bulkhead in the rear fuselage. This applies to the upper deck, where the passengers are accommodated, as well as to the cargo . . ~ . . . - . ~ . . ,- . . . compartments below. The equipment and turnlshmgs include floor panels and carpeting, lower sidewall panels, upper sidewall panels, overhead stowage compartments, service channel, ceiling panels, dividers, lighting, air-conditioning outlets (blowers, ventilation grids, etc.), passenger seats, flight attendant seals, flight attendant work stations, galleys, lavatories, stowages, passenger information signs, and emergency equipment. These standard furnishings are supplemented by optional items that are installed at the request of a particular airline, such as entertainment systems (audio, video), special provisions for the disabled, sleeping compartments, additional galleys and lavatories, more comprehensive emergency kits, and stairways. Due to different arrangements and variations in the number of items, an almost unlimited variety of interior design configurations is conceivable. This conceivable vanety, however, is in actuality restricted by the installation conditions, mutual overlappings, feasibility, installability, and, not least, safety considerations. Payload Systems, Development and Design, Deutsche Aerospace Airbus, Hamburg, Gerry. 203

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204 Improved Fire- and Smoke-Resistant Materials INTERIOR FURNISHING REQUIREMENTS The aim of aircraft interior design is to create such conditions on board commercial aircraft as are expected by the passengers. To achieve this objective, many requirements must be met. These can be subdivided into two categones: absolutely necessary measures, of vital importance for the passengers; and options that go beyond mere transportation and serve to create pleasant and comfortable Raveling conditions. Looked at another way these requirements can be viewed as including those that provide for (a) the accommodation of passengers, (b) the protection of passengers, (c) passenger services, and (~) passenger entertainment. Accommodation of Passengers In the past, it was common procedure for aerodynamicists, structure specialists, system engineers, etc., to build an aircraft to meet the needs primarily of their respective disciplines. The space available after all systems had been installed was then dedicated to passengers and furnishings in the most advantageous manner. After years of this approach, the mind-set of the development engineers has finally changed, so that accommodating the passengers now means to design the cabin layout according to the passengers' needs. The cabin layout must allow the demands for maximum transport capacity (high passsenger density) or maximum comfort (low passenger density) to be realized. Or, to put it more simply, the means of transport the aircraft and basis for a slightly graded passenger comfort, is built around the cabin, with due consideration, of course, to the physical and technical general conditions applying to an aircraft. In addition to the arrangement of seats, aisles, and escape routes, passenger accommodation also includes stowage space for hand luggage and a coat room. The requirements increase with the flight time; if several different climatic zones are traversed, the corresponding clothing is needed, as are reading matter, work documents, and games to help pass the time and toiletry articles for refreshment. On long-distance flights, passengers will ask for facilities for resting. The demand is due to business executives' needing rest, the transport of disabled, sick, or injured persons, and the need to accommodate replacement crews. The sleeper seats in common use today fulfill these expectations only in part. It is for this reason that regular rest compartments are now offered for crews, for instance. Protection of Passengers The aircraft interior in its entirety is laid out to protect passengers during their stay on board from all impact hazards likely to affect their well-being. The interior furnishing

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Swen ]. Schaich 205 components and He service systems are therefore laid out not only to make the stay on board the aircraft pleasant and comfortable but to provide maximum safety from all kinds of risks both during normal operation and in emergency situations. The function of the passenger seat is to accommodate the passenger and to afford a comfortable position for the duration of the flight. A belt serves to retain and keep the passenger from slipping out of the seat, for instance, during sleep, or in the event of gusts, turbulences, or rough landings. Reasonably dimensioned longitudinal and transverse aisles provide for interference- free traffic during boarding and leaving as well as during flight. These areas also serve as escape routes. Stowage compartments above the passenger seats receive the hand luggage. They can be locked and thus prevent pieces of luggage from dropping onto the passengers in all flight conditions. Dropping luggage presents a double hazard: injury to the passengers by immediate impact, or obstruction or blocking of escape routes. The cabin lighting system can, in connection with an emergency lighting system, help to avoid all sorts of mishaps. Since the equipment installed in the galleys and the provisions kept there can have a considerable weight, dual safety features are installed to prevent their uncontrolled movement. Throughout the cabin, passenger information signs and light signs are fitted that either provide information regarding the use of facilities (e.g., pictograms) or request a certain passenger behavior with the aim of minimizing safety hazards (e.g., "FASTEN SEAT BELT"~. The air-conditioning and cabin pressure control system protects the passengers from the effects of temperature, humidity, and flight altitude and supplies them with breathing air under conditions that resemble as closely as possible those on the ground. The entrance areas and the individual classes are separated by dividers that protect the passengers seated next to the doors from draft and heavy rain entering the cabin while passengers board and leave the aircraft. By suitable arrangement and design, dividers also break the long tube of the cabin down into sections that are furnished in accordance with the respective class standard. Naturally, the dividers are also used for other purposes, such as promoting the corporate image of the airline, advertizing, providing literature pockets, or the reception of folding baby bassinets. All components inside the cabin must be made from approved materials that in case of fire emit only small amounts of smoke and toxic gases and release only a limited amount of thermal energy (ATS 1000, Heat Release 65/651. Only such types of construction are used that, if mechanical failure occurs, do not present an additional risk of injury on account of the structure of the fracture. All these functions are dependent on an aircraft structure that allows installation of all interior furnishing components, as well as the service systems, and that is capable of supporting all occurring loads. Naturally, the cabin interior must offer optimal protection for the passengers, especially under crash conditions and provide means that are absolutely necessary to survival, such as oxygen systems, emergency exits and emergency escape slides, and fire-fighting equipment.

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206 Improved Fire- arm Smoke-Resistant Materials In summary, it can be said that both active and passive safety measures are taken to protect the passengers: Passive features are those that exclude safety hazards (e.g., nonflammable materials). Active features are those that reduce or eliminate existing dangers (e.g., fire extinguishers) . The interior furnishing components are therefore developed on the basis of the following criteria: minimization of risk potential during use, and provisions to reduce or eliminate the risk of accidents in dangerous situations. As with all other features, the protection of passengers, in particular from accidents, can also be extended and improved. However, such schemes make great demands on engineers from various different technical areas and involve considerable costs for development, manufacture, and sometimes even use. Passenger Services Depending on the specific flight, the passengers will be on board the aircraft for a longer or shorter period. During this time, at least the minimum needs of the passengers must be satisfied. But a further spectrum of services that goes beyond the very basic needs can be offered by the airlines to make traveling an attractive and pleasant experience. This means not only the serving of food and drinks in varying quality and selection by attentive flight attendants but also special offers that accommodate individuals' wishes and needs. Here, emerging trends must be carefully observed and analyzed. The trends do not develop uniformly. On the one hand, increasingly exclusive service facilities are demanded and supplied, and on the other hand, inexpensive flights where service is reduced to the absolute minimum are on the increase. Because the passengers pay special attention to the services offered, the airlines formulate particularly varied requirements in order to present their company-specific image. Passenger Entertainment Contrary to travel in ground-supported means of transport, flying usually offers, with the exception of take-off and landing, hardly any welcome diversion. Because the cruise flight takes place at high altitude, it is difficult to make out any details on the ground, and vision is often impeded by clouds and mist. In addition, the number of window seals is relatively small compared to the number of seats per seat row.

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Swen ]. Schaich 207 Although entertainment is not counted among the basic human needs, because of worldwide competition, no airline can afford nowadays not to offer these services. The range of activities offered must be adapted to the operational concept of the aircraft, the flight time, the image of the airline, and in particular the expectations of the passengers. It begins with the distribution of magazines and includes audio and video programs, computer games or complex information systems. These information systems allow the passengers to use information, work, or entertainment programs according to their personal preference. As in the serving of food, the trend here is also for "a la carte." Finally, business executives require communication services. The first and business classes need to be equipped, besides with telephones, with telefax and data services, to be supplemented by a secretariat if necessary. DETERMINING FACTORS Customer Requests and Feasibility Every airline faces the problem of maintaining a company-specific image that uniquely distinguishes it from its competitors. The exterior appearance of the aircraft provides a first impression of the airlines' corporate image, although in most airports passengers are checked in via closed passenger bndges. The interior design of the passenger cabin is also of the utmost importance. It is not merely a question of realizing the services described above; the airlines are also demanding ways and means to present their own specific concept of passenger service, which again means that every airline demands its specifically conceived interior design configuration. For the aircraft manufacturer, this means that standard solutions are not sufficient to meet the actual requirements. In other words, the sales prospects are largely dependent on the degree to which the interior design of the passenger cabin can be adapted to comply with the ideas and wishes of the customer. The aircraft manufacturer's response is therefore to develop types of aircraft that permit a high degree of flexibility where configuration and design of the interior components are concerned. At the same time, the costs for design, manufacture, and installation are kept within certain reasonable limits in order to achieve relatively short and scheduled planning and installation periods, and prices that the market will be prepared to pay. Types of Construction and Materials All aircraft components are designed according to lightweight construction principles because of the direct impact this has on the payload that can be transported. In the area of

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208 Improved Fire- arm Smoke-Resistara Materials interior design, the requirements are very complex since several functions must be fulfilled all at once: stiffness lightweight construction and high-stiffness materials to achieve a maximum payload; safety protection of passengers during flight and in emergency situations, and moderation of the results of accidents; design and color design that follows function and is esthetically satisfying, as well as suitable surface structure and color scheme; durability resistance to wear in the daily contact with passengers, and resistance to environmental conditions such as ozone, ultraviolet radiation, cigarette smoke, and caustic cleaning agents; hygiene dirt-resistant and easy-care surfaces, resistance to food and kindred goods (tobacco, alcohol) and compatibility with cleaning agents and disinfectants; and handling design and instructions suitable in form, fit, and function for the "standard passenger" as well as passengers with special needs, such as disabled people and children. In view of the multiple requirements, composite and hybrid structures are of particular importance. Sandwich structures are of high strength and retain their shape. Metallic materials are practically no longer used, except for mechanically and thermally highly stressed components. The primary structures are covered with preformed parts and then individually finished by means of decor foils, varnishes, or textiles. Barge components are treated in a similar way. Temperature-resistant layers for flammable materials improve the resistance to fire (fire-blocking foam layer for seat cushions). By embedding materials capable of dangerous fracturing behavior in flexible material, the risk of injury in the case of accidents is reduced. Since the passengers have direct access to most of the interior furnishing components, the wear to which these components are subject (through faulty operation, lack of understanding, malice, eec.) and the resulting failures and necessary replacement have to be taken into account. Assembly techniques that allow quick installation with the aid of only a few tools are therefore very important in order to avoid costly {urn-around times. The elements used in this connection are mainly of the plug-in, snap, locking, or clamping type, which calls for a high degree of accuracy to size and inherent stability of the component parts. Special measures are taken where resistance to fire is concerned, since a fire puts the passengers in extreme danger. There are two basic scenarios: n-pightire. A fire breaks out during the flight. The fire-fighting provisions must allow extinguishing the fire or slowing down the rate of propagation so that the nearest airport can be reached. The main objective must be to maintain the capability to fly. Because

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Swen J. Schaich 209 of the passengers, the smoke densities and the toxic constituents of the combustion gases must not exceec! certain values. Post-crash fire. Emergency landings may be accompanied by fires that are the result of fuel leaked from the wings or fuselage in the wake of the crash. In this case, too, the fire propagation must be slowed down to give ad passengers maximum opportunity to leave the aircraft. However, this is only possible if the passengers are not impeded in their movements by smoke, toxic combustion products9 or heat. The technical instructions refer to the release of thermal energy, smoke emission, and toxic gas components. For this reason, many interior furnishing components have had to be replaced at great cost with new materials. Materials such as polyviny~chioride (PVC), acrylonitrile-buladiene-styrene (ABS), or epoxy resins must no longer be used in the cabin; they have been replaced mainly with polyethenmide (PEI), phenolic resins, and others. By joint efforts on the part of aircraft manufacturers' interior design departments and material development departments, new materials that comply with the tightened limit values have been introduced. COMMERCIAL ASPECTS The discussion above may give rise to the impression that everything connected with the aircraft interior only causes considerable problems or rising costs for manufacturer and operator alike. It is true that the costs are high. But this impression is put into perspective if one keeps in mind that the interior design, apart from the service, is the most effective means an airline has for self-representation; in other words, the interior design is a marketing instrument of the highest order and must therefore express the airline's excellence. The manufacturer of interior furnishing components has a sales market that lasts for the whole utilization phase, a period! of 20 to 30 years. Many components need to be replaced during this time for reasons of wear, modification, modernization, or conversion. Proportion of Interior Design Cost;s Compared to Overall Costs The following data give an idea of the financial dimensions behind an aircraft intenor: quoted on the basis of the overall manufacturing costs for the Airbus A340 long-range aircraft; Interior furnishing of the cabin represents approximately 8.5 percent of the overall manufacturing costs of the aircraft. Interior furnishing of cargo compartments represents approximately I.5 percent of the overall manufacturing costs of the aircraft.

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210 Improved Fire- arm Smoke-Resistant Materials In referring to interior furnishing of the cabin and cargo compartments, there are about 8,000 different assemblies, about half of which must be modified to comply with the respective wishes of customers. Effect of Interior Furnishing on Prof.Hability Like other companies, the airlines must aim to make a profit. With few exceptions (e.g., cargo airlines), the largest share of their turnover is realized by the transport of passengers. Depending on the routes, however, earnings can also be improved by transporting cargo in addition to the passengers' luggage. Principally, there are two ways to boost turnover: 1. 2. Increasing the transport capacity. The cabin is bald out to accommodate the maximum number of passengers. Comfort and service are minor consid-erations. In order to achieve as nearly as possible full-capacity utilization, low-price tickets are offered (as, e.g., by charter airlines). Increasing the transport quality. The passengers are offered services and conveniences that exceed the usual standard. Here, a group of travelers is addressed who enjoy special services and are prepared to pay for it. In all instances, the strategy of the airline must be reflected in the cabin layout. The custom-designed interior components must be evaluated with a view to profitability, that is, in terms of additional income to be realized versus the amount of capital investment necessary to achieve it. An example of the above may be the transfer of service facilities to the underfloor area. For example, moving the lavatories to the aft cargo compartment may free additional space on the main deck for other purposes. This example shows very clearly that the cabin layout can significantly influence the profitability of an aircraft. Conversions or Second Interior Furnishing Sets Commercial aircraft are high-technology industrial assets that will be in service for long periods (20 to 30 years). During such a long time, the requirements regarding the interior furnishing of the cabin are subject to many changes due to such factors as change of ownership, modified service concept on account of different flight routes, altered sociological structure of passengers, technological progress, and modernization.

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Swen J. Schaich 211 The basic cabin layout must therefore incorporate a high degree of flexibility in order to provide the preconditions required for adaptation to changed circumstances. The interior furnishing components of an aircraft have a shorter life cycle compared to the airframe. This results from wear (~e constant use by passengers) and also from changes In fashion that make the design of a cabin layout appear outmoded. For these reasons several interior furnishing Sets for the same aircraft may be required during the life cycle of an airframe. Such conversions need to be performed without major modifications to the aircraft, that is, without essential alterations to the structure (modular system, families of parts). Further Development On long-distance flights, the cargo compartments cannot be used, or can be used only in part, for transporting goods because of the payload limitations effective for certain distances. If an airline wishes then to avoid transporting empty stowage, the utilization spectrum of the cargo compartments can be enlarged by transferring service facilities for the passengers from the cabin to the underfloor area. The following several functions may be realized in the underfloor area: storage space for the provisioning of food and beverages (catering), galleys, lavatories, crew restrooms, and passenger lounges. Through separation of the passenger and service areas, the passengers on the main deck will no longer be subject to molestations in connection with galleys and lavatories (traffic, unrest, noises, odors, etc.) and will have greater freedom of movement. This will enhance passenger transport quality. Passenger transport capacity also can be enhanced by installing additional passenger seats in the areas that have become available. This type of utilization extension is the more effective the more service facilities are moved. The advantages offered by the shifting of cabin functions are not restricted to long- distance flights. They are always useful where, without changing the outer dimensions of the aircraft, more space is to be made available for cabin functions. However, cargo compartments will have to be retained to accommodate the passengers' luggage. _. . . .

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