Summary
We propose to supersede an existing airworthiness directive (AD) that applies to certain transport category airplanes. The existing AD currently requires either activating all chemical oxygen generators in the lavatories until the generator oxygen supply is expended, or removing the oxygen generator(s); and, for each chemical oxygen generator, after the generator is expended (or removed), removing or restowing the oxygen masks and closing the mask dispenser door. Since we issued that AD, we have identified means to provide a supplemental oxygen system that does not have the unsafe condition. This proposed AD would require installing a supplemental oxygen system in affected lavatories, which would terminate the requirements of the existing AD. We are proposing this AD to eliminate a hazard that could jeopardize flight safety, and to ensure that all lavatories have a supplemental oxygen supply.