The FAA is proposing to amend certain FAR Part 25 airworthiness regulations regarding pressurization systems and oxygen dispensing equipment on transport-category airplanes to accommodate operations at airports with elevations at or above 8,000 ft msl. Currently, the agency makes a finding of an equivalent level of safety (ELOS) when a manufacturer or modifier proposes to certify cabin pressurization systems for operations at these higher-elevation airports.
Additionly, the FAA has been granting exemption requests from the automatic oxygen mask deployment requirements for operations at airports with elevations at or above 14,000 feet. This proposed action would relieve the burden on industry and the FAA that results from project-specific ELOS requests and petitions for exemption to accommodate operations at these high-elevation airports.
For example, regulations limit the cabin pressure altitude to not more than 8,000 feet under normal operating conditions. As such, the rules were never intended to imply that the cabin pressure altitude could exceed 8,000 feet under normal operating conditions. Therefore, the agency proposes adding an exception to allow the pressure to be equal to or less than the airport elevation while the airplane operates at or below 25,000 feet.
Pressurization rules also require a cockpit warning when the cabin pressure altitude exceeds 10,000 feet to alert the flight crew to potential hypoxic conditions. Under the proposal, that warning could be adjusted to change the cabin altitude warning to 15,000 feet or 2,000 feet above the airport elevation, whichever is greater, when operating at high elevation airports. Comments on the notice of proposed rulemaking are due by June 4.