NTERNATIONAL R EVIEW OF I NDUSTRIAL AND O RGANIZATIONAL P SYCHOLOGY 2005 from a socio-technical systems viewpoint, which assumes the root causes of

192 I NTERNATIONAL R EVIEW OF I NDUSTRIAL AND O RGANIZATIONAL P SYCHOLOGY 2005 from a socio-technical systems viewpoint, which assumes the root causes of

human error are often many and interrelated, this does pose some consider- able challenges. For example, how can a flight deck be evaluated for its error potential without reference to the skills, knowledge, and abilities of the users (i.e., the pilots)?

The airworthiness regulations must be viewed in a historical context. They evolved fromm ilitary specifications for the design and construction of aircraft and are organized on a ‘system-by-system’ basis. This structure was based on architectures with relatively independent systems and a low level of integration, e.g., each aircraft systemhad its own interface that used analog controls and instrumentation. Airworthiness approval was accom- plished by evaluating each individual systemto show compliance with the relevant requirement (see Applegate & Graeber, 2001). The ‘system-by- system’ approach to human factors certification is inappropriate, as human factors engineers design on a ‘task-by-task’ basis. This task-based approach implicitly crosses the boundaries of many systems, because pilots interact with several systems when performing many flight-related tasks. Many human factors problems lie not within an individual system(or single regulation), but between systems.

Perhaps the greatest challenge will be in deriving valid and reliable human performance measurement instruments and developing assessment processes upon which certification decisions can be made. In the certification of en- gineered aircraft components, what is measured is what is being certificated. In human factors assessments, the adequacy of the flight deck interface is inferred fromthe quality of perform ance of the assessor (or fromtheir opinion). It is not possible to measure the item to be certificated per se, because it is not possible to ‘measure’ the adequacy of the pilot–aircraft interface itself in the same way that you can ‘measure’ other engineering components (Harris, 1997).

In the early days of commercial aviation, any passenger fare was pure profit because all costs were covered by mail revenue. The only real consideration was to try and deliver the passenger alive and preferably unharmed (Kovarik et al., 1999). However, marketing and economic con- siderations in designing a modern aircraft cabin reveal the extent to which this position has changed. Manufacturers aimto design an aircraft interior so that as many features as possible can be adapted to the different requirements of airlines purchasing a single aircraft type, or for when the requirements of a specific airline change. Over the lifetime of a single aircraft, airlines may need to reconfigure the cabin to adapt to market changes in routes, the nature of operations, the type of passenger, and the balance between different classes of travel. In addition, airlines will generally be reluctant to install any non- standard items of equipment, fixtures, and furnishings, since this may reduce the value of an aircraft at resale. However, this ability to adapt and respond to the market has resulted in passengers having an increased range of In the early days of commercial aviation, any passenger fare was pure profit because all costs were covered by mail revenue. The only real consideration was to try and deliver the passenger alive and preferably unharmed (Kovarik et al., 1999). However, marketing and economic con- siderations in designing a modern aircraft cabin reveal the extent to which this position has changed. Manufacturers aimto design an aircraft interior so that as many features as possible can be adapted to the different requirements of airlines purchasing a single aircraft type, or for when the requirements of a specific airline change. Over the lifetime of a single aircraft, airlines may need to reconfigure the cabin to adapt to market changes in routes, the nature of operations, the type of passenger, and the balance between different classes of travel. In addition, airlines will generally be reluctant to install any non- standard items of equipment, fixtures, and furnishings, since this may reduce the value of an aircraft at resale. However, this ability to adapt and respond to the market has resulted in passengers having an increased range of

From an ergonomic perspective, the main users of the aircraft cabin are the passengers and the cabin crew. For passengers, the seat and seating space is of primary importance, particularly on flights of over five or six hours. On flights of lesser duration, a higher degree of discomfort is likely to be tolerated, and this may be one reason why low-cost operations so far have not tested this market. Seating and seat design is often the responsibility of the airline in-flight service department, who are likely to work closely with the marketing department in determining what seating and which at-seat entertainment facilities will be provided. Passenger comfort is known to be related not just to seat dimensions, but to personal space and the loading factor on any particular flight. Passengers prefer to have an empty seat beside them, and by manipulating the seating configuration to optimize the frequency of such occurrences, it is possible to maximize passenger percep- tions of comfort (Brauer, 1998). The regulatory requirements relating to seating design are primarily focused on crashworthiness and flammability considerations. One exception is the UK Civil Aviation Authority, which, uniquely among regulators, specifies a minimum allowable distance between seats (CAA, 1989). The required dimensions are currently under review, following a recent passenger survey and ergonomic assessment (Quigley, Southall, Freer, Moody, & Porter, 2001).

While the cabin is used by passengers on a transitory basis, it is the normal working environment for cabin crew. The workspace available will depend on the aircraft type, but is invariably limited, making for a cramped working environment. Specific ergonomic issues depend on the type of service being delivered and the equipment available, but common complaints include lack of headroom, strain from lifting and carrying passenger baggage, and using service trolleys in narrow aisles. In the galley, industry standard units may have worktops that are higher than optimal for a large proportion of the cabin crew and lack of storage space can lead to heavy, bulky, and cumbersome items being stored above head height. Not surprisingly, factors such as these are associated with a large proportion of cabin crew injuries (FSF, 2002). Operators prefer to maintain flexibility wherever possible, because this allows alterations to the style and provision of in-flight service to be made relatively quickly. However, this contributes to the problemof ineffective galley design, because it is difficult to optimize the galley layout for perform- ing a specific function or task, when the task itself may change on a regular basis.

The regulatory requirements for the design and configuration of the air- craft cabin tend to be aimed at the evacuation of the aircraft. A passenger evacuation in an emergency situation is the most telling test for any aircraft configuration designer, since successful completion of a timed evacuation demonstration under simulated emergency conditions is an airworthiness