Module 11A.14–11A.15 — Lights (ATA 33) and oxygen (ATA 35)

Levels

• 11.14 Lights — A1 level 2, B1.1 level 3.
• 11.15 Oxygen — A1 level 1, B1.1 level 3.

11.14 Lights (ATA 33)

External lights

Light	Colour / location	Purpose and key facts
Navigation (position) lights	Red on the left (port) wing tip, green on the right (starboard) wing tip, white at the tail	Show orientation; red and green each cover from dead ahead to 110° on their own side; white tail light covers 140° (70° each side of dead astern)
Anti-collision lights	Red beacons (top and bottom fuselage) and/or white strobes (wing tips, tail)	Flashing lights to make the aircraft conspicuous; red beacon on before engine start/whenever engines run; strobes on the runway/in flight
Landing lights	Wing root, fuselage or gear-mounted, sometimes retractable	High-intensity, forward/down; retractable lights have overspeed limits
Taxi lights	Nose gear	Illuminate the taxi path
Runway turn-off lights	Wing root / nose gear, angled outwards	Illuminate the sides when turning
Logo lights	Horizontal stabiliser, illuminating the fin	Conspicuity
Wing (ice) inspection lights	Fuselage sides	Illuminate wing/engine inlet leading edges to check for ice at night

• Lamp technologies: incandescent, halogen, HID/xenon (strobes use a capacitor discharge through a xenon tube — high voltage; wait for capacitors to discharge before maintenance), and increasingly LED.

Internal lights

Area	Lights
Flight deck	Panel integral lighting (dimmable, often 5 V), flood lights, dome lights, map/chart lights, storm lights (full brightness to counter lightning flash), annunciator lights with test and bright/dim
Cabin	General illumination (fluorescent or LED mood lighting), reading lights in PSUs, signs (no smoking/fasten seat belts/return to seat), lavatory lights and "occupied" signs, entry lights
Cargo	Cargo hold lights, often switched on with door opening; must not be a fire risk (guarded)

Emergency lighting

• Self-contained emergency power supply units (batteries charged from the aircraft bus) provide power for at least 10 minutes after loss of normal power.
• Exit signs, exit locator signs, interior emergency lights (aisle/ceiling), exterior emergency lights illuminating escape slide areas and overwing escape routes.
• Floor proximity emergency escape path marking (electrical or photoluminescent strips) guides passengers to exits in smoke.
• Controlled by a flight-deck switch (OFF/ARMED/ON) and a cabin attendant switch; ARMED in flight so they come on automatically if normal power is lost.
• Checks: battery capacity tests, illumination check, photoluminescent strips charged (exposed to light).

Key fact: Red navigation light on the left, green on the right, white at the tail; emergency lighting units must last at least 10 minutes.

11.15 Oxygen (ATA 35)

Why oxygen is needed

Above about 10 000 ft the reduced partial pressure of oxygen causes hypoxia: impaired judgement, euphoria, loss of colour vision, cyanosis, unconsciousness. Time of useful consciousness falls rapidly with altitude (from several minutes at 25 000 ft to seconds above 40 000 ft). Oxygen is required for crew and passengers after decompression and for therapeutic/first-aid use.

System layout

Users	Typical source
Flight crew	Gaseous oxygen cylinders (high-pressure), quick-donning diluter-demand masks at each crew station (on within 5 s), smoke goggles/full-face masks
Passengers	Chemical oxygen generators in PSUs (most narrow- and wide-bodies) or a gaseous system with distribution lines (some long-range types); masks drop automatically at about 14 000 ft cabin altitude or manually by the crew
Cabin crew / first aid	Portable oxygen bottles with masks; PBE smoke hoods

Sources and storage

Source	Key facts
Gaseous oxygen	Steel or composite cylinders charged to about 1 800–1 850 psi (painted green in many countries; check national colour codes); aviator's breathing oxygen — very dry (to prevent freezing in valves/regulators) and high purity (99.5 %+) — not medical or industrial oxygen
Chemical oxygen generators	Sodium chlorate core with iron powder; started by a firing pin when a mask is pulled down; produce oxygen for about 12–22 minutes; cannot be switched off; outer surface gets very hot (around 250 °C); dangerous goods — handle with safety pins/caps fitted
Liquid oxygen (LOX)	Converters storing oxygen at about −183 °C; mainly military
OBOGS	On-board oxygen generating systems — molecular sieve beds separate oxygen from bleed air (military, some business jets)

Charging (servicing) and distribution

• Charging through a filler valve with a pressure gauge, slowly (rapid filling causes heat of compression — adiabatic heating — fire risk); use a temperature-compensated pressure chart (pressure varies with temperature).
• Overboard discharge: a green blow-out disc on the fuselage skin ruptures if a cylinder over-pressurises (thermal) and vents the oxygen overboard — a missing green disc means a discharge has occurred.
• Distribution: cylinder shut-off valve (open slowly), pressure regulator/reducer (to low pressure, ~70 psi typical), lines (stainless steel/aluminium, identified with oxygen tape), outlets.
• Leak check with approved oxygen leak detection fluid (not soap with oil content).

Supply regulation

Regulator / mask type	Operation
Continuous flow	Constant flow (adjustable by altitude-compensating regulator) into a reservoir bag — passengers, first aid
Diluter demand	Flows only on inhalation; mixes cabin air with oxygen, increasing oxygen ratio with altitude; selector "N" (normal/diluted) or "100 %"
Pressure demand	Supplies oxygen under slight positive pressure at very high altitudes (above about 35 000–40 000 ft) — forces oxygen into the lungs; "EMERGENCY" selection gives overpressure to clear smoke from mask

Indications and warnings

• Crew cylinder pressure on ECAM/EICAS or gauge; low-pressure warnings; regulator flow indicators (blinkers) in masks.
• Passenger system "PAX OXY ON" / masks deployed indications; door-open sensors on PSU boxes on some types.
• Cabin altitude warning (~10 000 ft) and automatic mask deployment logic.

Oxygen safety

• No oil, grease or hydrocarbon contamination — oxygen + oil can ignite spontaneously; use clean hands, oxygen-compatible thread tape/lubricants only.
• No smoking or naked flames; ground the aircraft; avoid servicing during refuelling.
• Open valves slowly; cap open lines; purge lines after maintenance.
• Store cylinders secured, away from heat; chemical generators require special transport and disposal.

Key fact: Gaseous oxygen systems run at about 1 800–1 850 psi; charge slowly using a temperature-correction chart; a missing green overboard discharge disc means cylinder over-pressure discharge.