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 lights are RED on the LEFT (port) wingtip, GREEN on the RIGHT (starboard) and WHITE at the tail; plus red anti-collision beacons and white strobes, and landing/taxi/logo lights. Internal lights cover cabin, flight-deck and emergency lighting.
OXYGEN (ATA 35): flight crew use a diluter/pressure-demand system from bottles; PASSENGER emergency oxygen is commonly from CHEMICAL OXYGEN GENERATORS (which produce oxygen by a chemical reaction when the mask is pulled) or a gaseous system; portable bottles serve first aid.
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 drawing 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 — and chemical generators get HOT in use.
For the B2 technician the lighting circuits/controls and any electrical monitoring of these systems are the focus.
⚠ 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

An observer sees an aircraft at night showing a red light on its left wingtip and a green on its right. Which way is it heading relative to the observer?
Because navigation lights are red on the port (left) wing and green on the starboard (right) wing, seeing red-on-the-left and green-on-the-right means you are looking at the aircraft from more or less head-on/from the front — it is pointing towards you. If you saw green on your left and red on your right, it would be facing away.

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