Aviation Investigation Report A98H0003
4.1.4 MD-11 Flight Crew Reading Light (Map Light)
- 188.8.131.52 - Transportation Safety Board of Canada
- 184.108.40.206 - United States National Transportation Safety Board
- 220.127.116.11 - United States Federal Aviation Administration
- 18.104.22.168 - Hella Aerospace
- 22.214.171.124 - Swiss Federal Office for Civil Aviation
- 126.96.36.199 - Swissair
During an MD-11 wiring inspection carried out as part of an insulation blanket replacement program, it was noted that an insulation blanket was in contact with the upper part of the recessed map light installed on the right side of the cockpit ceiling. The MPET-covered insulation material had been imprinted and mechanically damaged by the back of the map light fixture, which houses a halogen lamp. Also, one of the ring terminal insulators attached to a wire lead that was attached to the map light, exhibited heat damage. Examination of the left map light found similar but lesser damage. No damage was reported for the observer station map light installations.
This discovery prompted an inspection of 12 additional MD-11 aircraft, which revealed various discrepancies, including cracked protective covers, repairs not in accordance with the component maintenance manual, heat deformation, evidence of arcing, and heat discolouration.
In light of the identified flammability risks associated with MPET-covered insulation blankets, the TSB forwarded an ASA (A000008-1) (STI4-12) to the NTSB so that it could review these preliminary findings and forward them to the FAA.
Subsequently, the SR 111 investigation revealed additional failure modes associated with the map light installation. On 29 December 2000, the TSB issued an ASIL (A000061-1) (STI4-13) apprising stakeholders of these developments.
The NTSB agreed that more should be done to determine the extent of the problem and sent a letter to the FAA encouraging it to take whatever action necessary to alleviate the problems outlined in TSB's ASA A000008-1.
Based on Boeing's Alert Service Bulletin (MD-11 33A069), the FAA issued AD 2000-07-02, which mandated a recurring inspection for the affected lights in the MD-11 cockpit. In January 2001, this AD was superseded by AD 2000-26-15, which required operators of affected aircraft equipped with map lights, as part of their aircraft's "Skybunk" installations, to include these as part of the original recurring inspection requirement. On 15 May 2001, the FAA approved the Hella SB 2LA005916-33-003 as an alternate means of compliance. While incorporating this SB does not terminate the AD, it changes the inspection cycle from every 700 hours to once a year. The AD will remain in force until such time as the unsafe condition related to the map light has been eliminated.
Hella Aerospace is working with Boeing to develop various design improvements to address the map light failure modes discovered during the SR 111 investigation. Proposed design changes include reinforced contact spring protective covers to minimize possibility of cracking and breakage, use of protective covers on the carrier frame to avoid metal-to-metal contact, relocation of spare bulb holder to avoid contact with the ON/OFF switch, and reforming of support brackets to reduce possibility of contact with terminal lugs. As an interim measure, Hella issued SB 2LA005916-33-003 dated 12 December 2000, which incorporates some of these changes. Hella advises that a successful design review, in cooperation with Boeing Engineering, took place in August 2002. Documentation regarding the final flight crew reading light (FCRL) redesign has been forwarded to Boeing and production of the new map light series, based on these product improvements, began in November 2002.
The Swiss FOCA reviewed and reissued AD 2000-07-02 as Swiss AD 2000-246 and AD 2000-26-15 as Swiss AD 2001-109.
In June 2001, SR Technics issued engineering order (EO) 217609.01 to incorporate Hella's SB 2LA005916-33-003. The EO modifies the FCRL (map light) to improve its short-circuit protection. This is accomplished in a variety of ways, including the replacement of the 11.5 watt (W) halogen lamp with a 7.0 W incandescent bulb. SR Technics advises that the EO was fully implemented as of March 2002.
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