Special Conditions Issued for 787 Inflatable Lap Belts
Many safety factors are involved, from the flammability of materials used in the belts to their performance in an incident that involves multiple impacts.
The Federal Aviation Administration has set the special conditions that will allow a unique type of passenger restraint, an inflatable lap belt, to be installed on some seats of Boeing 787 aircraft. The conditions took effect June 13, but FAA is accepting comments until July 18.
The agency's special conditions "can be characterized as addressing either the safety performance of the system, or the system's integrity against inadvertent activation. Because a crash requiring use of the inflatable lapbelts is a relatively rare event, and because the consequences of an inadvertent activation are potentially quite severe, these latter requirements are probably the more rigorous from a design standpoint," the Federal Register announcement states. It was issued in Renton, Wash., on June 13 by Ali Bahrami, manager of the Transport Airplane Directorate in FAA's Aircraft Certification Service.
The 787 will be a twin-engine plane with a two-aisle cabin, maximum takeoff weight of 476,000 pounds, and a maximum passenger count of 381. The inflatable lap belt is designed to prevent head injuries to passengers during an accident. The belt "behaves similarly to an automotive airbag, but in this case the airbag is integrated into the lapbelt, and inflates away from the seated occupant. While airbags are now standard in the automotive industry, the use of an inflatable lapbelt is novel for commercial aviation," FAA said.
The notice said while the belt has two potential advantages -- it could provide significantly greater protection than would be expected with energy-absorbing pads and can provide essentially equivalent protection for occupants of all stature -- it is an active system that must activate properly when needed.
The belt will rely on electronic sensors for signaling and a stored gas canister for inflation. "The consequences of inadvertent deployment as well as failure to deploy must be considered in establishing the reliability of the system," FAA said, adding that Boeing must substantiate that the effects of an inadvertent deployment in flight would not injure occupants.
Among the special conditions are these:
- It must be shown that the inflatable lapbelt will not impede rapid egress of occupants 10 seconds after its deployment.
- The system must be protected from lightning and high intensity radiated fields.
- Once deployed, the belts must not adversely effect the emergency lighting system.
- The belt must function properly after loss of normal airplane electrical power and after a transverse separation of the fuselage at the most critical location.
- It must be shown that the inflatable lapbelt will not release hazardous quantities of gas or particulate matter into the cabin.
- The inflatable lapbelt installation must be protected from the effects of fire such that no hazard to occupants will result.
- There must be a means for a crew member to verify the integrity of the belt activation system prior to each flight or it must be demonstrated to reliably operate between inspection intervals. The notice says FAA considers the loss of the airbag system deployment function alone is a major failure condition.
- The inflatable material may not have an average burn rate of greater than 2.5 inches/minute when tested using the horizontal flammability test as defined in part 25, appendix F, part I, paragraph (b)(5).