FAA Office of Aerospace Medicine
Civil Aerospace Medical Institute
PUBLICATIONS
AVIATION MEDICINE REPORTS

Report No: DOT/FAA/AM-02/11

Title and Subtitle: Human Factors Associated With the Certification of Airplane Passenger Seats: Seat Belt Adjustment and Release

Report Date: June 2002

Authors: DeWeese, R., and Gowdy, R.V.

Abstract: Two separate studies were accomplished to investigate human factors issues related to the use of lap belts. Human performance trials were conducted under two protocols to measure and assess: (1) seat belt tension adjustment during normal flight and emergency landing conditions, and (2) the effects on passenger emergency egress performance related to the lift-latch release angle of typical lap belts.

In the lap belt tension adjustment study, subjects were asked to sit in a typical passenger seat and adjust the lap belts as they normally would for take-off or landing during a commercial flight. Participants were then asked to adjust the lap belts as if they were anticipating an emergency landing. The airplane seat used in this study was instrumented to measure the tension in the lap belt, which was recorded for both the normal and emergency conditions. A total of 1182 subjects participated in this study. An analysis of results indicate that most passengers (90%) tighten the lap belt to a tension less than 7 lb. during normal flight conditions and less than 10 lb. for an anticipated emergency. These data indicate that the tension adjustment of lap belts restraining anthropomorphic test dummies in airplane seat certification tests should not exceed 10 lbs. to be representative of belt tension applied by a typical passenger. The current standard practice for adjusting the belt tension prior to these tests was evaluated and found to be adequate in light of these findings.

The lift-latch release angle experiments were designed to study lap belt restrained human subjects as they released the belt buckle and proceeded to egress from a typical passenger seat. Some foreign regulatory authorities require the release angle to be between 70 degrees and 95 degrees, whereas, typical U.S. buckles release between 45 degrees and 60 degrees. Three lap belts with latch release angles of 30 degrees, 60 degrees, and 90 degrees were installed on a triple passenger seat. Subjects were observed and timed as they tried to release the belts and exit from the seat.

Each was instructed to perform the exercise quickly. A total of 201 subjects participated in this study. No significant differences in human performance factors related to the lift-latch angle were detected from an analysis of the data.

Key Words: Lift Latch Buckles, Seat Belts, Transport Airplanes

No. of Pages: 22