SR 111 Investigation Report
3.2 Findings as to Risk
- Although in many types of aircraft there are areas that are solely dependent on human intervention for fire detection and suppression, there is no requirement that the design of the aircraft provide for ready access to these areas. The lack of such access could delay the detection of a fire and significantly inhibit firefighting.
- In the last minutes of the flight, the electronic navigation equipment and communications radios stopped operating, leaving the pilots with no accurate means of establishing their geographic position, navigating to the airport, and communicating with air traffic control.
- Regulations do not require that aircraft be designed to allow for the immediate de-powering of all but the minimum essential electrical systems as part of an isolation process for the purpose of eliminating potential ignition sources.
- Regulations do not require that checklists for isolating smoke or odours that could be related to an overheating condition be designed to be completed in a time frame that minimizes the possibility of an in-flight fire being ignited or sustained. As is the case with similar checklists in other aircraft, the applicable checklist for the MD-11 could take 20 to 30 minutes to complete. The time required to complete such checklists could allow anomalies, such as overheating components, to develop into ignition sources.
- The Swissair Smoke/Fumes of Unknown Origin Checklist did not call for the cabin emergency lights to be turned on before the CABIN BUS switch was selected to the OFF position. Although a switch for these lights was available at the maître de cabine station, it is known that for a period of time the cabin crew were using flashlights while preparing for the landing, which potentially could have slowed their preparations.
- Neither the Swissair nor Boeing Smoke/Fumes of Unknown Origin Checklist emphasized the need to immediately start preparations for a landing by including this consideration at the beginning of the checklist. Including this item at the end of the checklist de-emphasizes the importance of anticipating that any unknown smoke condition in an aircraft can worsen rapidly.
- Examination of several MD-11 aircraft revealed various wiring discrepancies that had the potential to result in wire arcing. Other agencies have found similar discrepancies in other aircraft types. Such discrepancies reflect a shortfall within the aviation industry in wire installation, maintenance, and inspection procedures.
- The consequence of contamination of an aircraft on its continuing airworthiness is not fully understood by the aviation industry. Various types of contamination may damage wire insulation, alter the flammability properties of materials, or provide fuel to spread a fire. The aviation industry has yet to quantify the impact of contamination on the continuing airworthiness and safe operation of an aircraft.
- Heat damage and several arcing failure modes were found on in-service map lights. Although the fire in the occurrence aircraft did not start in the area of the map lights, their design and installation near combustible materials constituted a fire risk.
- There is no guidance material to identify how to comply with the requirements of Federal Aviation Regulation (FAR) 25.1353(b) in situations where physical/spatial wire separation is not practicable or workable, such as in confined areas.
- The aluminum cap assembly used on the stainless steel oxygen line above the cockpit ceiling was susceptible to leaking or fracturing when exposed to the temperatures that were likely experienced by this cap assembly during the last few minutes of the flight. Such failures would exacerbate the fire and potentially affect crew oxygen supply. It could not be determined whether this occurred on the accident flight.
- Inconsistencies with respect to CB reset practices have been recognized and addressed by major aircraft manufacturers and others in the aviation industry. Despite these initiatives, the regulatory environment, including regulations and advisory material, remains unchanged, creating the possibility that such "best practices" will erode or not be universally applied across the aviation industry.
- The mandated cockpit voice recorder (CVR) recording time was insufficient to allow for the capture of additional, potentially useful, information.
- The CVR and the flight data recorder (FDR) were powered from separate electrical buses; however, the buses received power from the same generator; this configuration was permitted by regulation. Both recorders stopped recording at almost the same time because of fire-related power interruptions; independent sources of aircraft power for the recorders may have allowed more information to be recorded.
- Regulations did not require the CVR to have a source of electrical power independent from its aircraft electrical power supply. Therefore, when aircraft electrical power to the CVR was interrupted, potentially valuable information was not recorded.
- Regulations and industry standards did not require quick access recorders (QAR) to be crash-protected, nor was there a requirement that QAR data also be recorded on the FDR. Therefore, potentially valuable information captured on the QAR was lost.
- Regulations did not require the underwater locator beacon attachments on the CVR and the FDR to meet the same level of crash protection as other data recorder components.
- The IFEN Supplemental Type Certificate (STC) project management structure did not ensure that the required elements were in place to design, install, and certify a system that included emergency electrical load-shedding procedures compatible with the MD-11 type certificate. No link was established between the manner in which the IFEN system was integrated with aircraft power and the initiation or propagation of the fire.
- The Federal Aviation Administration (FAA) STC approval process for the IFEN did not ensure that the designated alteration station (DAS) employed personnel with sufficient aircraft-specific knowledge to appropriately assess the integration of the IFEN power supply with aircraft power before granting certification.
- The FAA allowed a de facto delegation of a portion of their Aircraft Evaluation Group function to the DAS even though no provision existed within the FAA's STC process to allow for such a delegation.
- FAR 25.1309 requires that a system safety analysis be accomplished on every system installed in an aircraft; however, the requirements of FAR 25.1309 are not sufficiently stringent to ensure that all systems, regardless of their intended use, are integrated into the aircraft in a manner compliant with the aircraft's type certificate.
- Approach charts for the Halifax International Airport were kept in the ship's library at the observer's station and not within reach of the pilots. Retrieving these charts required both time and attention from the pilots during a period when they were faced with multiple tasks associated with operating the aircraft and planning for the landing.
- While the SR Technics quality assurance (QA) program design was sound and met required standards, the training and implementation process did not sufficiently ensure that the program was consistently applied, so that potential safety aspects were always identified and mitigated.
- The Swiss Federal Office for Civil Aviation audit procedures related to the SR Technics QA program did not ensure that the underlying factors that led to specific similar audit observations and discrepancies were addressed.