Cramped Seating Can 'Trap' and 'Trip' Passengers During Emergency Evacuation

Air Safety Week, Nov 5, 2001

More space needed for today's overweight, aging passengers, study concludes

The combination of larger passengers crammed into tightly packed seats could delay emergency evacuation and contribute to potentially fatal embolisms on long flights. Providing more space between seats, and redesigning them to better accommodate persons of widely varying sizes, could have enormous cost implications to the airlines.

A recent study concludes that economy-class passengers are so tightly packed together that they cannot assume a correct "brace" position for emergency landing, and the seats themselves can be obstacles to quick emergency evacuation of the cabin. The current minimum spacing and design standards for transport-category aircraft allow for too-tight seating, and new standards are needed regarding minimum seat width and a minimum area for feet.

To meet the report's recommended standards, entire rows of seats on current aircraft would have to be removed and, depending on the aircraft, at least one seat per row would have to be removed to provide adequate seat width. One account suggests that as many as 100 seats would have to be removed from the economy sections of airplanes now in service, particularly those aircraft - primarily in charter service - featuring "high density" seating. The economic consequences could be enormous. A single row of six seats in an aircraft, with four of them filled on average per flight, can generate up to $8 million in ticket revenue over a 20-year period. Clearly, if seats were removed to meet expanded minimum space requirements, ticket prices might increase upwards of 25 percent. The counter argument is that while passengers are attracted to low fares, these fares are only made possible by a seating density that could compromise safety.

It is not clear by how much more space between seats - and the wider seats recommended - would speed up emergency evacuation. To this end, the report calls for emergency evacuation trials using various seat configurations, and featuring volunteer "passengers" more representative of today's aging, increasingly overweight population.

The report was prepared by ICE Ergonomics Ltd., a UK-based consulting firm specializing in occupational and vehicle safety research. Its report, "Anthropometric Study to Update Minimum Aircraft Seating Standards," was prepared for the UK's Civil Aviation Authority and for Europe's Joint Aviation Authorities (JAA).

The CAA is the only regulatory body to prescribe minimum seat-space dimension. The ICE study concluded that the CAA's minimum dimensions need to be expanded by at least 3 inches in terms of seat pitch, or the space between rows of seats, and by as much as 10 inches to more adequately accommodate tall people.

The CAA's standards also need to be expanded to address a minimum amount of leg room, seat width, height and length, armrest position, and a performance standard for seat back table latching mechanisms so that they will not fall down when passengers brush against them during an emergency evacuation.

In fact, the study's recommendations are not intended to improve the passengers' comfort. Rather, they are intended to ameliorate the problem of deep vein thrombosis (DVT) on long flights and, more particularly, to expedite emergency evacuation.

The starting point for the study of seating accommodations was a 1989 CAA airworthiness notice (AN64), which by its title mandates "Minimum Space for Seated Passengers." It applies to all transport-category aircraft carrying 20 or more passengers. The document is intended, according to its introduction, to outline the minimum seat pitch (space between seats) "taking into account head, trunk and leg strike areas of the seat in front, the ability to occupy the seat and, if necessary, to quickly vacate the seat and enter the aisle in an emergency."

With all seats in the upright position, AN64 lays out three minimum measurements:

Dimension A: Minimum seat pitch of 26 inches, as measured from the seatback cushion to the seat in front.

Dimension B: Minimum distance of 7 inches from the front edge of the seat cushion to the seat in front.

Dimension C: Minimum vertical space of 3 inches as measured from the front edge of the seat cushion to the backside of the seat in front.

AN64 did not lay out requirements for legroom or for seat height and width. Nevertheless, AN64 seems to be unique. No other regulatory body has published such minimum space requirements. The U.S. Federal Aviation Regulations (FAR) contain requirements for head impact protection, maximum G- loading, damage tolerant single load paths and so forth - but no minimum seat spacing requirements.

Despite the apparent uniqueness of the AN64 standard, the study found it deficient. Dimensions A, B and C are critical, the study authors declared, but the current minima need to be increased. For one thing, AN64 is based on the 5th-95th percentile of passenger sizes, "which means that at least 10% of passengers will not be accounted for," the study observed. When designing a seating system for safety, the minimum dimensions should account for the 1st - 99th percentile of passenger sizes. Even this range would not include children, people with disabilities, and it would "design out" about 1-in-100 passengers.