Ep 74 SwissAir Flight 111

Engineering News – FLEX Rover (1:40)

This week's engineering failure is SwissAir Flight 111 (4:15). A crash off the coast of Peggy’s Cove (9:10) is believed to be caused by a fire in the ceiling at the front of the plane (15:15). As an outcome of the crash investigation, a number of additional safety risks were identified and corrected (26:00).


Engineering News

SwissAir Flight 111

Episode Summary

Hi and welcome to Failurology; a podcast about engineering failures.  I’m your host, Nicole

And I’m Brian. And we’re both from Calgary, AB.

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This week in engineering news, Astrolab’s Flexible Logistics and Exploration (FLEX) Rover will be part of future Moon missions!

Now on to this week’s engineering failure; SwissAir Flight 111, a McDonnell Douglas MD-11 that crashed off the coast of eastern Canada, claiming the lives of all 229 onboard. 


Aircraft and Flight Crew

The Incident

Probable Cause

Initial Wire Arcing

Fire Detection and Suppression

System failure leading to increased fire propagation

During the fire, silicone elastomeric end caps installed on air conditioning ducts melted, which resulted in the addition of a continuous supply of conditioned air that contributed to the propagation and intensity of the fire.  The 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 during the last few minutes of the flight. The Board recommended that, as a prerequisite to certification, all aircraft systems in the pressurized portion of an aircraft, including their subsystems, components, and connections, be evaluated to ensure that those systems whose failure could exacerbate a fire in progress are designed to mitigate the risk of fire-induced failures.

Standby instruments – Positioning and power supply

Additional safety risks identified

During the course of this investigation, some additional risks that have the potential to degrade aviation safety were identified. Although these factors could not be shown to have played a direct role in this occurrence, the associated deficiencies could potentially lead to other accidents if the deficiencies are not rectified.

Areas of concern

      checklists that do not adequately deal with smoke conditions;

    aircraft designs that do not facilitate the rapid de-powering of electrical systems;

    MD-11 map light design and installation;

      lack of clarity in guidance material and regulations regarding wire separation in confined areas; and

      inadequacy of Supplemental Type Certificate standards to ensure that add-on equipment is compatible with the aircraft's type certificate

In addition to the 14 safety recommendations that the Board has issued during the course of the investigation, nine recommendations are presented in the final report:

      Two recommendations that deal with testing and flammability standards of in-service thermal acoustic insulation materials.

      One recommendation that deals with the application of existing standards for the certification of other materials.

    Two recommendations that focus on aircraft electrical systems, including additional measures for certifying supplementary add-on systems and industry standards for circuit breaker resetting.

      Four recommendations that propose improvements to the capture and storage of flight data as it relates to cockpit voice recorders, flight data recorders, and cockpit image recording systems.   

Safety action taken

As a result of the TSB's findings and recommendations during the course of this investigation, considerable safety action has been taken by various regulatory authorities, airlines, and manufacturers to address the recommendations, advisories, and observations made by the Board. Such action taken has significantly improved aviation safety worldwide.

Safety action taken to date includes the following:

      MPET-covered thermal acoustic insulation blankets have been ordered removed from aircraft;

    new flammability testing criteria have been developed;

    flight crew reading lights have been re-designed;

    additional guidance material for dealing with smoke situations has been issued to flight crews;

    aircraft checklists have been modified;

    numerous inspections have been completed on wiring and components to look for and eliminate potential ignition sources;

    the IFEN system was removed voluntarily from Swissair aircraft; subsequently the design was de-certified; and

      new FAA policies are in place for the certification of in-flight entertainment systems.

 So there you have it, an inflight electrical fire that resulted in the crash of SwissAir Flight 111 with the loss of 229 lives.  Better flammability testing criteria, in-flight fire detection, flight crew reading lights, and checklist redesign could have prevented a tragedy that took 229 lives.

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