2.3.3.2. Passenger cabin lights
Interior lighting installations for the passenger cabin vary depending on the size of aircraft; this ranges from a small quantity of roof-mounted incandescent lamps, through to integrated lighting concealed within the interior trim. These lights are controlled from the flight attendants' station. LED illumination is being specified on business and passenger aircraft that have pre-programmed settings for specific flight phases and time zones. The systems are automatically controlled to customize the mixing of colours and lighting levels; this is intended to help passengers combat the fatigue of long-distance travel.
Traditionally, each cabin light is controlled individually; this technology is being replaced by a central control unit connected to all the lights in the cabin. Those lights are linked via a data bus to their respective control units; each of the lights can be programmed for different scenarios.
Implemented through software, the lighting in the cabin is a mixed array of colours. LED technology offers higher reliability and reduced maintenance costs compared to incandescent and fluorescent lights. Cabin signs, e.g. 'return to seat' or 'no-smoking', are normally activated by the flight crew; on some aircraft the lights are armed by the crew and then activated automatically. Passenger reading lights are controlled from individual seat controls.
Additional entry floodlights are provided in the door areas. Exit lights are located adjacent to the emergency exits and are clearly visible, irrespective of whether the door is open or closed. Floor path lighting is used to in emergency situations to provide visual identification of escape routes along cabin aisle floor. These systems have sufficient energy to enable passengers to identify aisle boundaries. The system guides the passengers to designated emergency exits in accordance with the specific certification requirements of the aircraft.