Lights, Oxygen & Water/Waste

External/internal lighting, crew and passenger oxygen systems, and potable-water and vacuum-waste systems.

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Main ideas

EXTERNAL LIGHTS (ATA 33): navigation/position lights are RED on the LEFT (port) wingtip, GREEN on the RIGHT (starboard) and WHITE at the tail; plus anti-collision beacons (red) and strobes (white), landing, taxi, runway-turnoff and logo lights. Internal lights cover cabin, flight-deck and emergency lighting.
OXYGEN (ATA 35): the flight crew have a diluter-demand/pressure-demand system from bottles; PASSENGER emergency oxygen is commonly supplied by CHEMICAL OXYGEN GENERATORS (which produce oxygen by a chemical reaction when the mask is pulled) or a gaseous system; portable bottles serve first aid and walk-around.
WATER/WASTE (ATA 38): a potable-water system stores and pressurises drinking water to galleys/lavatories; the toilet system is usually a VACUUM waste system that draws waste to a sealed tank, serviced on the ground.
Oxygen systems demand scrupulous cleanliness — oil/grease with high-pressure oxygen is a fire/explosion hazard.
Chemical oxygen generators get HOT in use and are a transport hazard when carried loose.
⚠ Exam trap: navigation lights are RED on the LEFT wingtip and GREEN on the RIGHT; passenger emergency oxygen is often produced by a CHEMICAL generator (not a bottle) that becomes hot as it reacts.

Solved examples

A passenger oxygen mask drops and the passenger must pull the mask towards them before oxygen flows. Why, on a chemical-generator system?
Pulling the mask down pulls a lanyard/firing pin that starts the chemical oxygen generator: a chemical reaction (e.g. sodium chlorate) then releases oxygen for a fixed period. Until the pin is pulled no oxygen is produced, which is why passengers are briefed to pull the mask towards them. The generator gets noticeably hot during the reaction.

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