Sistema de Oxigênio da Tripulação

Visão Geral

The crew oxygen system provides flight deck crew and, on relevant aircraft, cabin crew with a supply of breathing oxygen independent of the cabin atmosphere. It serves two distinct scenarios: rapid depressurisation, where the crew must don masks quickly to remain cognitively capable during an emergency descent to a breathable altitude; and smoke or fumes events, where the aircraft's cabin atmosphere may become toxic or incapacitating. Regulations require flight crew members to have oxygen masks immediately available at their stations — reachable within five seconds — and to don masks whenever either crew member leaves their station during cruise at high altitude. The crew system uses high-pressure gaseous oxygen stored in dedicated cylinders, separate from the passenger chemical oxygen generators, providing a longer and more reliable supply.

Como Funciona

Gaseous oxygen is stored at high pressure (typically 1850 psi / 12.7 MPa) in composite-overwrapped or aluminium cylinders mounted in the equipment bay or nose area. A pressure regulator reduces supply pressure to mask delivery pressure, with a diluter-demand regulator at each crew station that delivers oxygen mixed with cabin air at low altitudes (diluter mode) and pure oxygen at high altitudes or 100% mode selected by the crew. Quick-donning masks are stowed in boxes adjacent to each flight crew seat; a single-hand squeeze-to-don mechanism allows a pilot to don the mask and establish an oxygen supply in under five seconds while the other hand remains on the controls.

Modern quick-donning masks include an integrated microphone allowing normal radio and interphone communication while wearing the mask, a pressure-demand mode for high-altitude pure oxygen delivery above 40,000 ft, and a smoke goggle or full-face option to protect the eyes in smoke/fumes scenarios. Cabin crew portable oxygen units — cylinder-and-mask assemblies — are stowed at crew stations and galley areas for use when cabin crew must move through a smoke-filled cabin during emergencies.

Componentes Principais

High-Pressure Oxygen Cylinder: Composite-overwrapped pressure vessels with pressure gauges readable from the flight deck to verify charge level. Cylinders are hydrostatically tested at mandatory intervals.

Pressure Regulators: Two-stage regulators reducing cylinder pressure to a stable intermediate pressure before the crew station diluter-demand regulators.

Quick-Donning Masks: Harness mask with inflatable face seal and single-hand donning mechanism. The diluter lever allows selection of normal (air-diluted) oxygen, 100% oxygen, or emergency (positive pressure) modes.

Portable Crew Oxygen Units: Walk-around bottles — small cylinders with masks carried by cabin crew during cabin inspections in smoke events. Duration typically 15–22 minutes of continuous flow.

Oxygen Quantity Indication: Cockpit gauges or ECAM/EICAS display showing cylinder pressure, allowing crew to assess remaining duration.

Aplicações em Aeronaves

FAR 25.1447 requires flight crew oxygen for all transport-category aircraft. The Boeing 737-800 carries a single high-pressure cylinder serving two pilot positions. The Airbus A320 uses a similar configuration. Wide-body aircraft such as the Boeing 777-300ER and Boeing 787-9 carry larger cylinders to serve two pilots plus an observer station, and may carry additional portable units for relief crew. The Airbus A380-800, with its additional upper-deck crew rest and relief crew requirements, carries an expanded oxygen system with multiple distribution points.

Advantages & Limitations

The gaseous crew oxygen system provides a reliable, consistent supply unaffected by the chemical activation issues of passenger chemical generators. Duration is substantial — typically 90 minutes or more for two crew at cruise altitude — providing ample time to descend to breathable altitudes and complete an emergency landing. Limitations include cylinder weight and volume, which constrain the total oxygen supply, and the need for regular pressure checks and hydrostatic testing that adds to maintenance burden. Human factors considerations — particularly in smoke scenarios where mask donning must occur while simultaneously flying the aircraft and communicating — have driven continuous improvement in mask ergonomics and one-hand donning speed. In extremely rapid decompression events, time of useful consciousness at cruise altitude (approximately 15–30 seconds) means that mask-donning speed is life-critical.