gas generator

A gas generator is a sealed chamber where a controlled chemical reaction produces high-pressure gas on demand. In aviation, these devices are used to supply compressed gas for emergency equipment, pneumatic systems, and actuators without requiring a compressor, electric motor, or external power source. The reaction is typically initiated by an electrical squib or igniter, and the whole process happens in milliseconds.

Most aircraft gas generators burn a solid propellant or decompose a liquid chemical. Solid propellant units contain a pressed charge of a fuel-oxidizer mix, often similar in composition to rocket propellant but formulated for rapid, controlled burn rather than sustained thrust. Liquid systems, such as those using hydrogen peroxide catalytic decomposition, pass the chemical across a catalyst bed where it breaks down into steam and oxygen at high temperature and pressure. The gas output is typically nitrogen, carbon dioxide, or steam depending on the propellant chemistry.

The most visible application is emergency oxygen systems in pressurized aircraft cabins. When cabin pressure drops below a safe threshold, a gas generator fires and produces oxygen that fills drop-down masks throughout the cabin. Ejection seat systems in military aircraft use gas generators to create the pressure pulse that ejects the pilot and seat from the aircraft. Landing gear extension systems, emergency brake applications, and door actuation systems also rely on gas generators for rapid, reliable operation when normal hydraulic or electrical systems are unavailable or too slow.

Gas generators must be manufactured to extremely tight tolerances and specifications. The pressure relief vents, ignition cartridge, and propellant charge are all engineered so that the output pressure and duration match the intended application. Overpressure or uncontrolled gas release can damage connected equipment; underpressure means the system fails to function. Corrosion and contamination are serious concerns because even small particles can clog nozzles or damage seals.

Storage and handling demand respect. Gas generators are classified as explosives in many jurisdictions because they contain an energetic charge. They have shelf lives, usually 10 to 15 years, and must be stored in cool, dry conditions away from heat, impact, and moisture. Maintenance technicians never disassemble or attempt to repair a gas generator; defective units are removed and replaced as complete assemblies. Periodic functional testing is done on aircraft equipped with gas generator systems to confirm they will operate when needed, but the test itself consumes the device.