Aviation Investigation Report A98H0003
1.6.18 Aircraft Interior Lighting
- 126.96.36.199 - Cockpit and Passenger Cabin Normal Lighting
- 188.8.131.52 - Emergency Lighting, Battery Packs, and Battery Charging System
- 184.108.40.206 - Flight Crew Reading Light (Map Light)
The MD-11 cockpit lighting includes overhead fluorescent lamps for area lighting, flood lights to illuminate the instrument panels, and integrally lighted panels. The cockpit also has supplemental lighting that includes flight crew reading lights (map lights), floor lights, and briefcase lights. The intensity of most of the lights can be controlled by rotary dimmer switches.
Lighting in the cabin includes overhead and side wall fluorescent light assemblies, as well as incandescent light assemblies that provide overhead aisle lighting and door entry lights. Cabin lights can be controlled from the cabin attendant stations.
The MD-11 has an emergency lighting system that illuminates the cockpit and the cabin. The system includes ceiling lights in the cockpit, as well as overhead aisle lights, cabin door handle lights, exit sign lighting, and floor escape path lighting in the cabin.
The emergency lighting system consists of the lighting network and six battery packs, each with a battery charger and control logic that determines the power source. The system, including battery charging, is normally powered by the right emergency AC bus. If normal power is disrupted, the control logic is designed to switch first to the left emergency DC bus, and then if necessary, to the battery packs.
The batteries are on continuous charge whenever the EMER LT switch located in the cockpit is in the ARMED position and the EMER LT switch located at the left mid-cabin attendant station is in the OFF position. This is the normal in-flight switch configuration. Fully charged batteries will allow for about 15 minutes of emergency lighting.
The emergency lights can be turned on by using either the EMER LT switch in the cockpit, or the switch at the attendant station. The lights turn on automatically with a loss of power to the 115 V AC ground service bus.
The first item in the Swissair Smoke/Fumes of Unknown Origin Checklist (see Appendix C) calls for selecting the CABIN BUS switch to the OFF position. Doing so removes the electrical power from the cabin bus that supplies power to most of the cabin electrical services. If the EMER LT switch on the cockpit overhead panel is not switched to the ON position before moving the CABIN BUS switch to OFF, the cabin emergency lights will not automatically illuminate. In such a case, either the pilots or a cabin attendant would need to turn the EMER LT switch on to activate the emergency lights.
220.127.116.11 Flight Crew Reading Light (Map Light) (STI1-32)
The MD-11 cockpit has four map lights installed in the overhead ceiling area (see Figure 16). These lights provide additional illumination for the pilot and first officer positions, and for the left and right observers' stations. On the occurrence aircraft, the captain, first officer and right observer's station lights (PN 2LA005916-00) were manufactured by Hella KG Hueck & Co. (Hella). The left observer's light, PN 10-0113-3, was manufactured by Grimes Aerospace Co., and was a different design than the Hella light.
The Hella map light is designed to pivot up to 35 degrees from its vertical axis through 360 degrees. The light intensity is adjusted by turning the smaller diameter ring on the light head, which also serves as an ON/OFF switch. The size of the light beam, or area of illumination, is adjusted by turning the larger diameter ring on the light head. The map light was equipped with a 11.5 watt (W), 28 V DC tungsten halogen lamp.
The front of the map light is covered by a plastic ball cup; an insulating protective cap is installed on the rear of the light fixture. The protective cap is designed to insulate and protect the metal contact spring, which serves as the positive terminal that applies 28 V DC electrical power to the lamp base.
The Swissair MD-11 flight crew bunk module lights, PN 2LA 005 916-00 SWRA, were also manufactured by Hella. This bunk light was a map light that had been modified by removing the functionality of the ON/OFF switch to meet an FAA certification requirement. Although the bunk light used a different outer housing than the map light, the internal components were identical.
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