A320 Lighting

The Airbus A320's lights fall into four groups. The exterior lights make the aircraft visible to others and let the crew see the runway, the taxiway and their own wings. The flight deck lighting lights the instruments, panels and work surfaces. The cabin signs and cabin lighting tell the passengers what to do, and the emergency lighting guides everyone to the exits when the normal lights have failed.

Most of the controls are on the overhead panel: the EXT LT panel for the exterior lights, a row of internal lighting switches, and the SIGNS panel for the cabin signs and the emergency exit lighting. Much of the lighting has automatic logic tied to the landing gear, the flaps, the cabin altitude or the electrical network, and that logic is what type rating questions test. The general principles are in aircraft exterior lighting and flight deck, cabin and emergency lighting. Equipment varies between aircraft (single or dual navigation lights, LED or conventional lamps, the sign switches fitted), and the article says where the FCOM gives alternatives.

Exterior lights and their switches

The exterior lighting comprises the navigation lights, the landing lights, the runway turn-off lights, the takeoff and taxi lights, the logo lights, the anti-collision lights (red beacons and white strobes) and the wing and engine scan lights. The cargo hold lights are interior lighting.

The wing lights light the wing leading edge and the engine air intake so that the crew can see ice accretion. On aircraft with LED navigation and strobe lights, a small blue light below each unit monitors its wear: below a navigation light it flashes, with NAV & LOGO on, when the replacement of that light should be planned; below a strobe it does the same when the STROBE switch is OFF or the BEACON switch is ON.

The lighting is not identical across the family. The FAA's Flight Standardization Board report lists multi-function runway lights as a design difference of the A321neo XLR from the A321neo ACF, at the lowest training and checking level.

Landing, taxi and runway turn-off lights

Each landing light has its own selector. ON extends the light, which comes on automatically once it is fully extended. OFF switches it off but leaves it extended. RETRACT switches it off and retracts it. A green LDG LT memo appears on the ECAM whenever one landing light is extended, so in cruise it gives away a selector left at OFF instead of RETRACT: the light is dark but still out.

The NOSE switch controls the two lights on the nose gear strut. T.O turns on both the taxi light and the takeoff light, TAXI only the taxi light, and OFF both. The RWY TURN OFF switch turns the runway turn-off lights on and off. The taxi, takeoff and runway turn-off lights go off automatically when the landing gear retracts, so a switch left on after takeoff does not leave them lit in flight. The landing lights have no such logic: they stay as selected (the procedures allow LAND to stay ON in the climb), and only RETRACT stows them.

Exterior lights through a flight

The standard operating procedures use the lights as follows:

View full schematic

Strobe, beacon, navigation and logo lights

The two red beacons flash on top of and under the fuselage. The parking procedure switches them off only when all engines have spooled down.

The three white strobes flash in synchronization. At AUTO they come on automatically when the main landing gear is not compressed, that is, in flight; the signal comes from the shock absorber detectors read by the landing gear control and interface units (LGCIUs). On the ground at AUTO they are therefore off, which is why the procedures select ON to cross a runway and return to AUTO after leaving the runway at the end of the landing. A STROBE switch left OFF in flight brings up a green STROBE LT OFF memo, a reminder rather than a caution.

The navigation lights, single or dual depending on the aircraft, are on each wing and in the APU tail cone. With dual lights the switch reads 2, 1 and OFF: position 1 turns on navigation lights 1 and the logo lights, position 2 navigation lights 2 and the logo lights.

The logo lights on the upper surface of each horizontal stabilizer light the company logo on the fin. They share the NAV & LOGO switch, but come on only when the main gear is compressed or, depending on the aircraft, when the slats or flaps are extended (on some aircraft, flaps at least 15°). In clean cruise flight they are off even with the switch on.

Flight deck lighting and the ANN LT test

Every instrument and panel on the flight deck, except the display units, has integral lighting, and the instrument panel also has flood lighting; the brightness of all of it is adjustable. Spot and flood lights cover all work surfaces and the side consoles, and two dome lights give the whole flight deck shadow-free lighting. The controls are spread by area:

• Overhead panel: the DOME switch (BRT, DIM, OFF), which works both dome lights together; the OVHD INTEG LT knob for the overhead panel's own integral lighting; the ANN LT switch; the ICE IND & STBY COMPASS switch for the standby compass light and the light of the external ice indicator between the windshields; and a READING LT knob on each side, which turns that pilot's reading light on and off and sets its brightness.
• Pedestal: FLOOD LT MAIN PNL, for the flood lighting of the main instrument panel; INTEG LT MAIN PNL & PED, one knob for the integral lighting of both the main instrument panel and the pedestal; and FLOOD LT PED, for the flood light in the middle of the overhead panel that lights the pedestal. Lights under the glareshield light the center instrument panel.
• Glareshield: knobs for the glareshield's integral lighting, the FCU display brightness, and the sliding table and map holder lighting.
• Main instrument panel: a CONSOLE/FLOOR switch on each side (BRT, DIM, OFF) for the side console, the briefcase stowage and the floor around that pilot's seat.
• Lateral windows: each pilot has a map light switch and a brightness knob.

The display units have their own brightness controls: an on-off and brightness knob for each PFD, and OFF/BRT knobs on the ECAM control panel, to which an automatic adjustment for ambient light is added. The avionics compartment light, on the maintenance panel, is controlled by the compartment door at AUTO and stays on at ON. When the batteries alone are supplying the aircraft, only the right-hand dome light works.

The ANN LT switch sets all the flight deck annunciator lights to one brightness: BRT for normal operation, DIM to dim them all together, and TEST. At TEST every annunciator light comes on and the figure 8 appears on all the LCDs of the flight control unit, and the crew check that everything lights. While the switch is at TEST the crew must not reconfigure the display units (ECAM/ND transfer) or switch the display management computers.

Cabin signs and cabin lighting

The SIGNS panel carries a SEAT BELTS switch and, depending on the aircraft, a NO SMOKING, an EXIT or a NO PORTABLE ELEC DEVICE (NO PED) switch. Each has three positions:

• ON: the signs are on in the cabin.
• AUTO: the signs come on whenever the landing gear is extended or the slats and flaps are extended at position 1, 2, 3 or FULL.
• OFF: the signs are off.

The SEAT BELTS switch lights the FASTEN SEAT BELT and RETURN TO YOUR SEAT signs. If the cabin altitude exceeds 11,300 ft (±350 ft), all the cabin signs except NO PED come on whatever the switch positions, and so do the cabin lights, depending on how the cabin system is programmed. A low tone chime, also programming-dependent, sounds each time a sign comes on or goes off. While the signs are on, the ECAM shows SEAT BELTS, NO SMOKING, NO PED or NO MOBILE memos, according to the customization.

In an emergency descent, SIGNS ON is the second memory item, after CREW OXY MASKS USE and before EMER DESCENT INITIATE (see A320 memory items). When the aircraft is secured at the end of the day, CM2, the pilot in the right seat, sets the EMER EXIT LT switch and the SIGNS switches to OFF.

The cabin lighting itself, general illumination and the passengers' reading lights, is handled by the cabin intercommunication data system (CIDS), whose decoder/encoder units along the cabin connect the general illumination ballast units; the cabin crew control it from their panels (see A320 cabin systems and CIDS). From the flight deck, the COMMERCIAL pushbutton, where fitted, removes the cabin and cargo lights together with the galleys and other commercial loads, and most cabin lighting is shed in the emergency electrical configuration.

Emergency lighting and exit markers

The emergency lighting comprises the proximity emergency escape path marking (escape path markers and exit markers), the overhead emergency lights, the EXIT signs, the lavatory auxiliary lights, the overwing escape route lighting and the escape slide lighting. The lavatory auxiliary lights are always on. The EMER EXIT LT switch on the SIGNS panel controls the rest:

Whatever the switch position, the LIGHT EMER pushbutton on the purser's panel can turn the emergency lighting on. The escape slide lights and the overwing escape route lights come on automatically when the slide is armed and its door or emergency exit is opened, and they run from internal batteries. Where the escape path or exit markers are electrical, internal batteries supply them for at least 12 minutes (see A320 doors and emergency equipment).

The ARM logic ties in with the electrical system. AC BUS 1 is always lost in the emergency electrical configuration, so at ARM the overhead emergency lights come on, and the shedding of the DC SHED ESS bus when the batteries alone remain is itself one of the triggers for the EXIT signs and exit markers.

Library articles are written for study and exam preparation. They do not replace your aircraft's approved documentation, your operator's procedures or the regulations themselves.