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In-Service Performance Criteria for Aircraft Interiors Hanns-Ioerg Betz * INTRODUCTION Besides flammability, toxicity, smoke emission, wear-resistance, and other technical requirements that are defined in detailed specifications by the aircraft manufacturers, special requirements out of the service experience had to be incorporated in the design of aircraft interiors. Often the specification requirements do not meet the "in-service requirements criteria." In order to create a comfortable feeling for the passenger the aircraft interior must provide durable performance while showing a clean, pleasing, and comfortable cabin without any visible damage. INFLUENCE FACTORS TO THE CABIN PERFORMANCE An ideal airplane interior would have outstanding performance, would not need any maintenance, and would allow a system of servicing that would not damage the furnishings. Unfortunately, up to now and in the near future this is not feasible. Airlines recognize that they are dealing with people and are generally content with the low incidence of vandalism. There are several factors that influence cabin performance. These include: design and manufacturing, material performance, passengers, service personnel, and mechanics. EXAMPLES OF PERFORMANCE PROBLEMS Material Performance The first thing that passengers notice when they board an airplane is the floor covering. Directly, they can see dirt and wear caused by trolley wheels, shuffling shoes, and uneven floor panels. Panel gaps, moving panels, and washers not properly attached allow bolts to show clear marks on both nontextile and textile floor coverings especially on nontextile floor coverings that *Cabin and Cargo Systems, Lufthansa German Airlines, Frankfurt, Germany. 197

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198 Improved Fire- and Smoke-Resistant Materials are installed in areas prone to corrosion or heavy loads. Slip resistance must be maintained throughout the year, especially in the winter, to provide safety for the passengers and crew. During the winter, floors can be made slippery by residues from anti-icing fluids, increasing the potential for mishaps. The next items that passengers see and fee! are the seats. The performance metric for seat cushion behavior is the indentation hardness. Not apparent to the passengers are the safety- enhancing characteristics of the fire-blocking layers. Aged fire-blocking layers may no longer meet fire-blocking star~dards as currently specified. Regular tests of used cushions are carried out to maintain confidence in the material performance. Generally, passengers do not notice inactive bulbs in the lighting system unfit a specific situation occurs where the lights are needed (e.g., when there is a need for a reading light, passenger signals, or floor path markings). Since it is too late to solve the problem during the flight, the airlines do frequent inspections and repairs of these systems, which create unnecessary costs. Passengers and Crews During boarding, passengers may have problems in stowing their hand luggage. The allowable number and size of carry-on bags are defined by the airlines and the International Air Transport Association. Nevertheless, passengers often bring more luggage onboard than allowed. Hand luggage is sometimes too large to fit into the stowage bin opening which results in the use of force to stow the luggage. The consequence is damaged hinges, doors, and structures. Hard hand luggage or bags with special latches can damage walls and decorative laminates, as they are squeezed through the narrow aisles. Thin laminates and lightweight panels are damaged easily and then have to be repaired. Toilets are used to dispose of waste paper towels, diapers? beer bottles, plastic glasses, and sometimes passports, which clogs toilets and disturbs the next passenger, who will have an unusable toilet. REASON FOR PERFORMANCE PROBLEMS Other reasons for performance problems are caused by servicing and maintenance personnel. Servicing Personnel Catering, cargo loading, cleaning, toilet-servicing, and water-servicing personnel are generally low-pa~d, low-skilled people. After a short training course, they are required to learn "on the job." They are always under time pressure, as they do not want to be responsible for departure delays. When problems occur, they try to solve the problems by themselves without

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Hanns-J6erg Betz 199 detailed knowledge of the situation (e.g., resetting systems, trying to switch systems, or trying to override a system). Transporting heavy trolleys with additional parts on top will damage floor panels and floor covering. In cargo compartments, decompression panels are damaged and require repairs. Maintenance Personnel Maintenance mechanics are responsible for keeping the cabin in good condition in terms of performance and appearance. Problems are identified using the cabin log book, the technical log book, quick examinations by mechanics during transits, and specified maintenance checks. In the beginning of the service of a new aircraft, the documentation is incomplete and background information on potential problem areas is not available. During this time, the mechanics are learning from experience and on-thejob training, necessitating additional inspections and functional checks to verify that performance has not been compromised. Design deficiencies cost a significant amount of additional work for the mechanics. The first modifications of the parts improve the situation. If sufficient spare parts are available, the mechanic may exchange the parts without registering a complaint, which allows maintenance trends or poor performance to remain unsubstantiated. PERFORMANCE CRITERIA The appearance and function of the cabin needs to be maintained to a high standard. The aircraft cabin is regularly checked according to maintenance checks, intervals, and tasks. The maintenance checks take the following items into consideration: continuous safety, quality for passengers, materials, and costs per part. Continuous Safety Safety in an aircraft cabin is mandatory. Therefore, regular checks are required by the crews and by the mechanics. At the beginning of the flight, all passengers are asked to become familiar with in-flight safety requirements and evacuation requirements.

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200 Improved Fire- aM Smoke-Resistant Materials FI~nability Requirements In the case of component flammability, it is difficult to ensure the quality and compliance with the applicable rules. Therefore, it is necessary to only allow the use of materials that meet regulatory requirements for flammability. One means to ensure continued compliance with flammability requirements is to have spares in storage of all parts that may be damaged. Since this is obviously not feasible, the mechanic must have He materials and methods available to repair parts that allow continued compliance with performance requirements. Repair matenals and spare parts must meet the latest standard of flammability requirements. There should also be assurance that the component design is tolerant of an acceptable level of damage without influence on the flammabiliyv requirements. Prevention of Cabin Malfunction , ~ Damage may occur due to improperly latched bins, stowed and latched trolleys, and ovens. Therefore, proper checks of all latches before and during flight need to be performed by the cabin crew. Bins not properly locked may cause damage aunt could represent a cianger to passengers. Quality for Passengers To achieve the maximum comfort for the passengers and reduce maintenance, improvements in aircraft interior seats, seat cushions, galleys, lavatory systems, entertainment, cabin lighting systems, and air-conditioning systems are needed. Ideally, seats should not have to be inspected at all and should always function properly and provide complete comfort. Colors, fabrics, and surfaces are chosen that hide dirt and are easily cleaned. Ashtrays are designed to be cleaned without any damage. Seat cushions are designed to fit in the seat structure without internal tearing. The appearance of a new replacement part shouic! not be significantly different from the original installation. Repairs of minor damage need to be easily hidden. A significant amount of maintenance and a number of modifications are required to keep cabin systems, such as lavatories, water systems, and entertainment systems, functioning. in case of system problems during flights, notification of the crew and remediation should occur without disruption of passengers. Airlines need to continue to improve the comfort and convenience of travel for passengers. Therefore, Lufthansa and other airlines are searching for new developments or features for in-flight entertainment and other items to better please our passengers. It is also important to heed trends in passengers' demands or complaints.

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Nanns-J6erg Betz 201 Materials The technical performance requirements for the cabin materials are defined in detailed specifications. Some of the characteristics controlled in materials specifications include: flammability, low-cost producibility, resistance to aging, color stability and reproducibility, mechanical properties, ease of repair, and optimized weight. The weight has an important influence on the fuel costs, payload range, and performance. Costs per Part Many Lufthansa customers complain about high fares for flights. We are often shocked as well with the cost of an interior part. But there are significant nonrecurring and certification costs associated with the development of a part to be installed in an aircraft. Also, the manufacturer has to guarantee excellent product quality and quality control that meet the requirements of the specification. In addition to these costs, the airline has to account for the maintenance, overhaul costs, part service life, and product improvements. These additional costs may reduce the performance tremendously. Having parts in the shop for repair too often results in modification or exchange of the pad. Service and maintenance experience for cabin components are reported to the supplier and aircraft manufacturer. These experiences may lead to modifications to improve the performance. Product support is very important to enable keeping parts in good condition. Maintenance and In-Service Costs Maintenance actions are always seen in connection with high operating costs. These activities range from daily monitoring to an overhaul or D-Check, which has to be performed, in most cases, every 5 to 6 years. At this time, a 747 will have carried about 200,000 to 300,000 passengers per year. Therefore, the frequency of the maintenance inspections is important to achieve a positive result. For economic reasons, it is necessary to reduce the duration and downtime of the airplane. To reduce the downtime, it is necessary to either increase the manpower or to make maintenance activities easy. Accessibility of parts for maintenance actions is very important. Otherwise, delays will result, and passengers will become disappointed or angry. Further delays could lead to other problems such as rotation problems, disruption of inspection intervals of other airplanes, and cancellation of flights (with airline responsibility for hose! accommodations).

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202 Improved Fire- aru] Smoke-Resistant Materials Airlines are looking to reduce the manpower needed to perform maintenance ant! to perform the work with lower-qualified personnel. These trends reinforce the need to improve cabin design and materials performance to a point where, instead of performing maintenance, ground personnel need only check the function and appearance of the cabin. CONCLUSION Aircraft cabin performance criteria are influenced by frequency of required actions, material, people, and design. Cost and quality need to be optimized for weight, part costs, and in-service costs; safety and quality for passengers; and lifetime costs. Airlines need a passenger-pleasing ant! safe airplane at all times with reductions in required maintenance.