Communiqués

TSB # A 08/2000

(Hull, Quebec, 24 May 2000) - The detailed work of examining the wreckage from Swissair Flight 111 is continuing, primarily in Shearwater, Nova Scotia, and in Ottawa at the Engineering Laboratory of the Transportation Safety Board of Canada (TSB). The workload is high, and the pace of the work is influenced by the need to complete a detailed examination and analysis of thousands of pieces of aircraft debris. Some of these pieces have the potential to reveal information about the operation of the aircraft, about the heat patterns and about damage to the aircraft structure and systems. Other aspects of the investigation are also continuing, including those involving operational issues and human performance.

Work is continuing on various fronts:

• There are 20 arced electrical wires that have been found. Work is ongoing to see if it is possible to distinguish between wires that arced because of damage from an external heat source (ie damaged by a fire), and arcing in a non-fire environment. This work is time-consuming and will not be complete for some time.
• Analysis of the airflow testing in the space above the ceiling in the forward section of the aircraft's fuselage is continuing. The interpretation of information from the airflow tests cannot be completed until more information from other aspects of the investigation is available, particularly from further detailed wreckage examination.
• Progress is being made in the examination of the various aircraft systems components. A thorough analysis of this information is being completed in an attempt to determine the status of the aircraft systems at impact and potentially, to shed light on some of the events of the last six minutes of flight. For example, examination of the information from the Full Authority Digital Electronic Controller (FADEC) indicates that the number 2 engine was shut down by crew activity during this period.
• During this investigation, examination of other MD-11 aircraft from more than one operator revealed several damaged flight crew reading lights (often referred to as map lights). The lights are installed in close proximity to thermal acoustical blanket covering material called metallized polyethylene terephthalate (PET). This material has been identified as likely being a significant source of the combustible materials that propagated the fire in this accident and has been the subject of previous TSB Recommendations in this investigation. Investigators found the right-side crew reading light from Flight 111 and it does not show arcing or heat damage. Investigators are continuing to look through the recovered wreckage pieces to find the left-side crew reading light.

In March 2000, the TSB issued a Safety Advisory concerning these map lights. Regulatory authorities, along with the airframe manufacturer and the light manufacturer, have taken initiatives to address the potential safety issues associated with these lights. Operators are now inspecting these light installations on their fleets. At this time, the investigation has not established a connection between this safety issue and the circumstances of Flight 111.

The investigation into this accident is complex and time-consuming. As the investigation continues, more fact-finding and safety analysis will be undertaken. To date, this investigation has led to the identification of a number of safety deficiencies and to safety actions concerning wiring, flight recorders, thermal acoustical insulation blankets, flight crew reading lights, and a review of operating procedures. As other safety deficiencies are validated, further safety action will be pursued.

NOTE: This update is based on information assembled by the investigation staff and will be amended as other facts are gathered. The investigation is not complete and one should not attempt to infer findings as to the causes and contributing factors of this accident on the basis of this update.

-(30)-