Aviation Investigation Report A98H0003

4.1.5  In-Flight Firefighting

  1. 4.1.5.1 - Transportation Safety Board of Canada
  2. 4.1.5.2 - United States Federal Aviation Administration/Transport Canada
  3. 4.1.5.3 - The Boeing Company
  4. 4.1.5.4 - Swissair
  5. 4.1.5.5 - United States National Transportation Safety Board

4.1.5.1  Transportation Safety Board of Canada

The SR 111 investigation identified safety deficiencies associated with in-flight firefighting measures. Subsequently, the TSB issued five ASRs (A00-16 through A00-20) (STI4-14) (STI4-15) (STI4-16)  (STI4-17) (STI4-18) that identified safety deficiencies with respect to in-flight firefighting. The identified safety deficiencies increase the time required to assess and gain control of what could be a rapidly deteriorating situation and reflect a weakness in the efforts of governments and industry to recognize the need for dealing with in-flight fire in a systematic and effective way.

The TSB believes that the risk to the flying public can be reduced by re-examining fire-zone designations in order to identify additional areas of the aircraft that should be equipped with enhanced smoke/fire detection and suppression systems. Therefore, the TSB made the following recommendation:

Appropriate regulatory authorities, together with the aviation community, review the methodology for establishing designated fire zones within the pressurized portion of the aircraft, with a view to providing improved detection and suppression capability. A00-17 (issued 4 December 2000) (STI4-19)

Along with initiating the other elements of a comprehensive firefighting plan, it is essential that flight crews give attention, without delay, to preparing the aircraft for a possible landing at the nearest suitable airport. Therefore, the TSB made the following recommendation:

Appropriate regulatory authorities take action to ensure that industry standards reflect a philosophy that when odour/smoke from an unknown source appears in an aircraft, the most appropriate course of action is to prepare to land the aircraft expeditiously. A00-18 (issued 4 December 2000) (STI4-20)

Aircraft accident data indicate that a self-propagating fire can develop quickly. Therefore, odour/smoke checklists must be designed to ensure that the appropriate troubleshooting procedures are completed quickly and effectively. The TSB is concerned that this is not the case, and made the following recommendation:

Appropriate regulatory authorities ensure that emergency checklist procedures for the condition of odour/smoke of unknown origin be designed so as to be completed in a time frame that will minimize the possibility of an in-flight fire being ignited or sustained. A00-19 (issued 4 December 2000) (STI4-21)

An uncontrollable in-flight fire constitutes a serious and complicated emergency. A fire may originate from a variety of sources, and can propagate rapidly. Time is critical. Aircraft crews must be knowledgeable about the aircraft and its systems, and be trained to combat any fire quickly and effectively in all areas, including those that may not be readily accessible. The TSB believes that the lack of comprehensive in-flight firefighting procedures, and coordinated aircraft crew training to use such procedures, constitutes a safety deficiency. Therefore, the TSB made the following recommendation:

Appropriate regulatory authorities review current in-flight firefighting standards including procedures, training, equipment, and accessibility to spaces such as attic areas to ensure that aircraft crews are prepared to respond immediately, effectively and in a coordinated manner to any in-flight fire. A00-20 (issued 4 December 2000) (STI4-22)

In-flight firefighting "systems" should include all procedures and equipment necessary to prevent, detect, control, and eliminate fires in aircraft. This systems approach would include material flammability standards, accessibility, smoke/fire detection and suppression equipment, emergency procedures and training. All of these components should be examined together and the inter-relationships between individual firefighting measures should be reassessed with a view to developing improved, comprehensive firefighting measures. The TSB believes that an in-flight firefighting system, developed according to a systematic approach and consisting of complementary elements, would result in the most effective in-flight firefighting system; therefore, the TSB made the following recommendation:

Appropriate regulatory authorities, in conjunction with the aviation community, review the adequacy of in-flight firefighting as a whole, to ensure that aircraft crews are provided with a system whose elements are complementary and optimized to provide the maximum probability of detecting and suppressing any in-flight fire. A00-16 (issued 4 December 2000) (STI4-23)

4.1.5.2  United States Federal Aviation Administration/Transport Canada

Both the FAA and TC concurred with the TSB's position with respect to in-flight firefighting, and have advised that a review of existing programs is underway. Upon completion of the review, both regulators, in conjunction with the JAA, will take a harmonized approach to improving the in-flight firefighting system. As of March 2002, the program review involved the following activities:

  • Developing fire tests for materials in inaccessible areas;
  • Developing the most effective means to gain access to hidden areas for the firefighting purposes;
  • Determining the feasibility of fire detection and suppression systems in inaccessible areas;
  • Exploring the feasibility of water spray and nitrogen suppression systems;
  • Developing improved fire/smoke detection systems;
  • Developing ultra fire-resistant interior materials;
  • Enhancing tools to allow for accurate risk assessment of aircraft wiring system threats;
  • Developing new CB technology to prevent the harmful effects of arcing and arc tracking; and
  • Developing certification criteria for new fire detector sensor technology.

4.1.5.3  The Boeing Company

Boeing issued a Flight Operations Bulletin (MD-11-99-04) to all MD-11 operators that discussed various options for dealing with smoke in the cockpit. Boeing also established a Boeing Smoke/Fire Committee to study the operational impact of smoke and fire events on each Boeing-manufactured aircraft.

4.1.5.4  Swissair

4.1.5.4.1  MD-11 Checklists

Swissair issued an Aircraft Operations Manual (AOM) Bulletin (90/99) advising its MD-11 flight crews of a revision to the Smoke/Fumes of Unknown Origin Checklist (see Appendix C – Swissair Smoke/Fumes of Unknown Origin Checklist). Swissair decided to change the checklist to ensure that the EMER LT switch is selected before the CABIN BUS switch is selected. This change was based on an incident on a flight from Singapore to Zurich, during which the cabin crew had to deal with a "dark cabin" after the CABIN BUS switch had been selected. By design, the emergency lights in the cabin do not come on by selecting the CABIN BUS switch to the OFF position, even if the emergency lights are armed.

To save time when following this checklist, Swissair also instructed its MD-11 flight crews to proceed directly to the SMOKE ELEC/AIR selector checklist item, thereby eliminating the requirement to evaluate the results of de-powering the cabin bus and the need to restore power to the cabin bus.

In March 1999, after intensive discussion with the aircraft manufacturer on the new revision, Swissair conducted a test flight in aircraft HB-IWR to validate the new checklist procedure.

Swissair issued an AOM Bulletin (94/99) to advise its MD-11 flight crews about supplemental information on in-flight smoke/fire. The AOM Bulletin describes the Boeing Flight Operations Bulletin MD-11-99-04, "Supplemental Information to MD-11 Flight Crews on Inflight Smoke/Fire Procedures."

In 1993, the MD-11 manufacturer had decided to eliminate the Air Conditioning Smoke Checklist (see Appendix B – Swissair Air Conditioning Smoke Checklist) because all items covered in this checklist were included in the Smoke/Fumes of Unknown Origin Checklist. However, at this time, Swissair decided to keep the Air Conditioning Smoke Checklist because that checklist would provide a faster method of isolating the specific source of smoke/fumes when they were known to be coming from the air conditioning system. Swissair considered the use of this Air Conditioning Smoke Checklist to be less disruptive to aircraft systems, such as flight displays, communications and navigation systems, than the use of the Smoke/Fumes of Unknown Origin Checklist, which requires the generator buses to be turned off sequentially.

In AOM Bulletin (94/99), Swissair also advised its MD-11 flight crews about a revision to its emergency procedures with respect to dealing with smoke and fumes. Swissair indicated that "under certain circumstances the identification of a smoke source could be very difficult and that in some scenarios, where the air conditioning system acts as transportation media but does not represent the smoke source itself, this could lead to misinterpretation of the smoke origin." To standardize with the manufacturer, as well as to clarify and expedite the smoke source identification process, Swissair decided to use the Smoke/Fumes of Unknown Origin Checklist in any given smoke/fumes situation. Swissair cautioned its flight crews that the Smoke/Fumes of Unknown Origin Checklist "will lead to a shutdown of essential aircraft systems."[121] In addition, Swissair amended the Smoke/Fumes of Unknown Origin Checklist to advise flight crews—at the beginning of the checklist rather than at the end—to consider emergency landing, ditching, and fuel dumping.

Swissair issued an AOM Bulletin (111/00) to advise its MD-11 flight crews about a revision to its Smoke/Fumes of Unknown Origin Checklist. OXYGEN MASKS was added as the first item in the Smoke/Fumes of Unknown Origin Checklist. This addition did not represent a change to Swissair practices, as donning an oxygen mask had always been the first memory item when dealing with smoke situations in simulator training. Subsequently, in AOM Bulletin (122/01) Swissair explained the reasons behind the dramatic changes in the presentation of the Smoke/Fumes of Unknown Origin Checklist procedure. This same bulletin informed the MD-11 flight crews that Airbus has combined three "smoke" procedures into one checklist procedure similar to the MD-11 Smoke/Fumes of Unknown Origin Checklist.

4.1.5.4.2  Training

Swissair continued to educate its MD-11 flight crews through AOM Bulletins and Info Flashes (an internal newsletter) on its CB reset policies, checklist revisions, and incidents that involve smoke or odours. Flight crews were informed about increased inspections of map lights owing to heat damage discovered during maintenance.

In recent years, Swissair has revised its ground school refresher training to include briefings based, in part, on the SR 111 experience. The briefings were meant to emphasize the need for effective communications and timely decision making when dealing with smoke of unknown origin.

Swissair revised the part of its cockpit (or crew) resource management training program dealing with smoke emergencies. The program, attended by both pilots and cabin crew, consists of a day of lectures and reaffirmed the company's policies with regard to the new policies and procedures.

4.1.5.4.3  MD-11 Modification Plus Program

In the post-accident environment, Swissair and its maintenance provider, SR Technics, undertook a joint study to analyze all potential factors that may have contributed to the accident. The study focused on exploiting opportunities to minimize the vulnerability of the MD-11 aircraft to an in-flight fire by developing an early warning smoke detection system. The stated intention was to enhance the firefighting and emergency response capability of the MD-11 and not to call into question the type certification of the aircraft. The study resulted in the adoption of the "MD-11 Modification Plus" program.

The program consists of the following enhancements:

  • Miscellaneous Smoke Detector System: This modification installs smoke detectors in the avionics compartment, the cockpit overhead area, and the first-class galley overhead zone of the MD-11. The system consists of a dual-loop smoke detector system, which illuminates an amber MISC SMOKE warning light on the glareshield control panel, together with an aural warning. An emergency checklist entitled MISC SMOKE was created and introduced to the MD-11 crews via AOM Bulletin (123/01).
  • Video Camera Monitoring System: This system installs cameras in the avionics compartment, the cockpit overhead area, and the first-class galley overhead zone to provide a visual confirmation of the presence of smoke. The camera installation includes a dedicated display screen, located on the centre pedestal, to allow the pilots to view the area of interest.
  • Halon Distribution System: This system consists of three fixed Halon bottles connected to a distribution system. The HDS can direct a fire-suppressing agent to the cockpit overhead area, and the first-class galley overhead zone. As these areas are not readily accessible, this modification optimizes the aircraft crew's fire-suppression capabilities.
  • Wire Routing: This part of the program includes a wiring modification designed to enhance separation and increase survivability of flight-critical systems. The modification physically separates the left and right power wires to opposite sides of the cockpit.
  • Oxygen System/Air Conditioning System Improvements: As a fire-hardening measure for its crew oxygen system, Swissair incorporated Boeing's SB MD11-35-021, which replaces aluminium components with steel. Additionally, Swissair has replaced the end caps used in the air conditioning system ducting with a more fire-resistant version.
  • Standby Flight Instruments: This unit is a "mini" primary flight display. It combines all necessary flight-relevant information including standby horizon, speed, altitude, and heading indications. This unit also includes an automatic back-up battery power supply.

To reduce aircraft downtime the "MD-11 Modification Plus" program is being coordinated with the MPET-covered insulation blanket replacement program as required in accordance with FAA AD 2000-11-02.

All modifications have been approved by the appropriate airworthiness authorities and as of January 2003, nine MD-11s previously owned by Swissair, have been modified in accordance with the "MD-11 Modification Plus" program.

4.1.5.5  United States National Transportation Safety Board

On 4 January 2002, the NTSB released five recommendations (A01-83 through A01-87) dealing with recent in-flight fires. Although not directly related to the circumstances of the SR 111 accident, NTSB's efforts reflect a common concern with the provisions currently in place for in-flight firefighting. That is, the TSB recommendations took a systems approach in identifying deficiencies in such areas as detection and suppression, crew coordination, checklist procedures, equipment, and accessibility. The NTSB recommendations focused primarily on deficiencies associated with the actions of aircraft crews in dealing with in-flight fires. The NTSB recommendations complement those of the TSB by highlighting inadequacies in aircraft crew awareness and training that limit their ability to execute effective in-flight firefighting.


[121]    The Boeing Company describes those systems affected by the use the Smoke/Fumes of Unknown Origin Checklist as aircraft subsystems rather than "essential" systems.

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Date modified :
2012-07-27