Fire in the Sky: SwissAir 111 Report



Canadian Transportation Safety Board focuses on in-flight fires

 

On March 27, 2003, the Canadian Transportation Safety Board (TSB) released its long-awaited report into the September 2nd, 1998 crash of SwissAir Flight 111 (SR 111), a McDonnell-Douglas-11 which crashed near Peggy’s Cove, Nova Scotia, killing all 229 people on board.  The TSB’s multi-million dollar investigation focused on in-flight fires, which may overcome an aircraft and its crew before there is time to take advantage of ground-based ARFF. Ironically, the aircraft was only 66 miles and 20 minutes from Halifax when the tragic events began.  This only underlines the dangers faced many times each day by airliners venturing over water or inhospitable terrain, hundreds of miles and hours away from suitably-equipped recovery airports.  

 

This article is organized into five parts, the first four mirror and summarize the TSB report; the fifth is an exclusive interpretation of the report for AFJ readers.

 

1.  Factual Information

 

Shortly after the aircraft reached its initial cruising altitude of 33,000 feet on its way from New York’s JFK airport to Geneva, the crew detected an unusual odor in the cockpit.  At first, the pilots believed it was probably an air conditioning anomaly, but within 4 minutes, the crew had declared a “Pan-Pan-Pan” and requested an immediate return to the nearest airport.

 

Air Traffic Control in Moncton, New Brunswick cleared the aircraft to Halifax, Nova Scotia and down to 31,000 feet, later clearing it down to 3,000 feet, in anticipation of a landing on runway 06 at Halifax. The crew was pre-occupied with checklists for descent and dealing with air conditioning smoke and smoke/fumes of unknown origin. Unable to make a stabilized approach directly into Halifax, carrying fuel for a Trans-Atlantic flight and on the wrong side of Halifax for the 06 approach, the crew requested and was granted time to lose altitude and to dump fuel.

 

Thirteen minutes after first detecting the odor, the autopilot and other electrical systems (yaw dampers, flight control computers, Left Emergency AC Bus, Altitude, Airspeed, cockpit displays) began to fail, and a minute later, the crew declared an emergency.  The last communication from the aircraft was heard only 20 seconds later. Half a minute after that, the cockpit voice and flight data recorders stopped functioning. The crew shut the number 2 engine down while still in flight, possibly because fire-damaged systems gave a false indication that the tail-mounted engine was on fire.  Five minutes later, the doomed aircraft hit the water in a spiral dive (bank angle estimated between 60 and 110o) at approximately 300 knots, subjecting all 14 crew and 215 passengers on board to an unsurvivable force of “in the order of at least 350 g.”  The aircraft broke up into more than 2 million pieces, and then sank into water 90 metres deep.

 

Rescue efforts by local fishermen, the Canadian Coast Guard and the Canadian Navy soon proved futile and the operation then shifted into the recovery mode, which turned out to be a staggering challenge.  Five major attempts over 13 months were made to recover underwater debris, including by Canadian Navy divers, the salvage ship USS Grapple, heavy lift barges, scallop dragger operations and a suction hopper dredge. Remotely operated submersibles were used during all phases of the recovery.  Ultimately, TSB investigators were able to recover almost 98% of the aircraft by weight, much of it in tiny pieces. 

 

The precise location of the two data recorders, ultimately located by a Canadian Navy submarine, and recovered by Navy divers on the 4th and 9th day of the investigation, was complicated by the fact that both were transmitting on the same frequency.  Although they were recovered largely intact, investigators were frustrated to find that electrical power to both units had been cut five minutes before the impact, leaving them without a significant amount of critical data.

 

Although a major setback, this provided clues about the crash: both data recorders were powered from the same source: the Generator 3 (i.e. right engine) bus. During the emergency checklist dealing with smoke/fumes of unknown origin, each of the three engine-driven generators buses is deactivated in sequence to isolate a possible source of smoke/fumes. This procedure may take several minutes per bus, or 20-30 minutes in total (35 mins according to the Chief McDonnell Douglas Test Pilot Tom Moody here).  When the FDR failed, the aircraft was still in a clean configuration - flaps, slats and wheels up. The fact that the aircraft crashed with the hydraulically actuated flaps set to 15o but the electrically actuated slats retracted, contrary to their normal extended position for that flap setting, was yet another indication that the aircraft was experiencing serious electrical difficulties. 

 

Heat and Fire Damage

 

Any fire in the cockpit ceiling did not penetrate the aircraft skin, nor was there any discoloration of the aircraft’s white exterior paint.  Yet there was evidence of a fierce fire in the attic area – hidden above and behind the flight crew seats, all the way back to the cockpit bulkhead and into the first class and even business class cabin. The inside of the aircraft’s skin in this area was heavily sooted. The insulation blankets in the attic, some two layers thick, seemed to protect the aircraft skin from fire. However, the metalized covering of these blankets that were pressed against a maze of wiring and ducting in the attic was damaged or destroyed. 

 

There was also considerable evidence of heat and fire damage to the air distribution ducts in the cockpit and cabin areas, which proved helpful in determining the areas of fire.  Vents near the forward galley, located immediately aft of the cockpit, designed to catch and expel cooking odors, played a role in the transmission of smoke and heat: two of these ducts sustained high heat damage.  Part of the first class ceiling area had been exposed to temperatures as high as 593oC/1100oF for 10 minutes.

 

Floor carpets as far forward as the cockpit and seats as far aft as business class also showed hot material dripping down from the ceiling.  The dripping and sagging cockpit ceiling liner afforded further clues: it begins to soften and sag at between 246-274oC/475-525oF.  Parts of this area were found to be heavily sooted, discolored dark brown and black, blistered and bubbled, suggesting temperatures of at least this magnitude, if not more.  A circuit breaker panel on the right hand side of the cockpit, behind the copilot’s seat, was found to have been exposed to temperatures similar to those from 430-620oC/800-1150oF for 10 minutes. The overhead circuit breaker panel above and between the two pilots’ seats was found to be similarly damaged.

 

Potential Ignition Sources

 

The investigators paid considerable attention to the area of the aircraft between the cockpit and a section just into the first class area of the cabin.  Of particular interest was the attic, the area above the ceiling but below the roof of the aircraft, which was filled with wiring, ducting and insulation blankets. With unmistakable evidence of a fire in the attic area of the cockpit and forward cabin, the obvious question concerned the ignition source. 

 

The investigators concluded the most likely source was electrical energy.  Sections of four bundled power supply cables for the In-Flight Entertainment Network (IFEN) were found with melted copper, an indication of an arcing event. These cable sections, which had been exposed to temperatures in the range of 500oC/932oF for 10 minutes, were found on the ceiling on the right hand side of the cockpit bulkhead.  Examination of these wires suggested two areas of arcing, the first, which did not trip the associated circuit breaker, and a second arc that’s believed to have raised the temperature of the circuit to a level where the circuit breaker likely did trip. The sequence and location of these events suggests that the fire started forward and then initially moved aft with the airflow.

           

Also of great interest were the materials used, notably wire insulation and the thermal/acoustical blankets used in aircraft, in this case, metalized polyethylene terephthalate (MPET) known by its trade-name as metalized Mylar®. 

 

Although MPET had earlier passed the FAA’s vertical Bunsen burner test, the Civil Aviation Administration of China (CAAC) discovered, following from three incidents, that once burning, MPET could be completely consumed by fire.  The CAAC brought this to the FAA’s attention in 1996; the latter agency said that they while they would look into the matter, the tests used by the CAAC were not required for FAA certification.  Less than six weeks after the SR 111 crash, the FAA announced it would develop new specifications for aircraft insulation materials. It was not before 2000 that the FAA mandated the removal of MPET covered insulation blankets. 

 

One area of concern to the investigators was the need to fire-harden aircraft systems. It was noted that the aluminum lines in the flight crew oxygen system could leak at temperatures as low as 427oC/801oF. Above this temperature, the oxygen lines had a tendency to rupture, sometimes in as little as three minutes, introducing pure oxygen into a fire environment, greatly exacerbating the situation.  Similarly, fiberglass ducting and end-caps showed little tolerance to high heat, again providing fire with a fresh air supply and a means of propagation.

 

The TSB conducted airflow tests to determine how smoke and fumes would be influenced by various ventilation fans being turned on and off during the various emergency checklists. It was found that some switch selections caused airflow reversal between the cockpit and the cabin.

 

On Board Fire-Fighting Capability

In terms of the aircraft’s own fire-protection and fire-fighting system, it was noted that in keeping with FAA regulations, there were fire detection and fire suppression systems in the designated cargo areas in the belly and in the engines and Auxiliary Power Unit (APU) as well as lavatories. The cockpit and cabin were not required to have detection or suppression systems; instead there were 8 portable fire extinguishers, five of which were 2.5 pound Halon 1211 and two five pound monoammonium phosphate (dry chemical) extinguishers.  The remaining portable extinguisher was a single 2.5 pound Halon 1211 unit in the cockpit, mounted on the rear wall, out of the immediate reach of the pilots. 

 

The report noted that, in accordance with Joint (European) Aviation Requirements, the cabin crew had received initial and recurrent training on firefighting, including the importance of identifying the source of the fire, the location, handling of fire fighting equipment, communicating with the cockpit and firefighting responsibilities. As was consistent throughout the industry at the time, there was no training in how to deal with fires in the cockpit or in the inaccessible areas, such as the attic. 

 

The investigators also took great note of the aircraft’s electrical supply system, including the power fed to the IFEN as they began to focus on electrical arcing events above the cockpit and over the bulkhead that separates the cockpit from the first class cabin. This arcing could be caused by metal-to-metal contact between an exposed and energized wire and a source of an electrical ground. Arcing events can generate extremely high temperatures by the arc (up to 5000oC/9,000oF or more), the vaporization of molten conductor and local gases.  If flammable materials are nearby, this can be the ignition source for a fire. 

 

The investigators found a total of 21 wires that showed melted copper - an indication of an arcing event. One wire was insulated with irradiated ethylene-tetraflouroethylene (known as XL-ETFE or its trade name, Cross-Linked Tefzel®); the others were insulated either by polyimide (known as PI or its trade-name, Kapton®) or ethylene-tetraflouroethylene (known as ETFE or its trade-name, Tefzel®).

 

The general purpose wire in aircraft HB-IWF was polyimide wire, which although light in weight, a good insulator, resistant to abrasion and producing little smoke when burned, it was susceptible to arc tracking, a process where the insulation, when charred, turns into a conductor, and can, over time, cause a massive arc. The insulation on the IFEN wiring was EFTE, with the exception of the power supply cables which were PTFE (polytetraflouroethylene, known by its trade name, Teflon®) 

 

Owing to differing resistance to abrasion, wires with differing insulation should not be installed in close proximity to one another, as the tougher insulation can, under circumstances of heat and vibration, abrasively wear through the insulation of a wire with softer insulation.  PI is the most resistant to abrasion, EFTE is less resistant to abrasion and cutting than PI; PTFE is the least resistant to abrasion and cutting.

 

It is interesting that the report cites an undated document produced by the MD-11’s manufacturer, advising “that high vibration and wire-to-wire abrasion testing has shown that, when properly installed, the mixing of different approved insulation types has not been a problem.” 

 

The report indicates that as certified and installed on HB-IWF, the original IFEN system design did not incorporate an ON/OFF master switch.  The ability to turn the system on or off was achieved by pulling a circuit breaker.  The report addressed the negative implications of aircraft circuit breakers being used in this manner, including the wear and tear on the circuit breakers, and the subtle suggestion that circuit breakers can be regarded as merely a switch of convenience, rather than a thermal protection device whose tripping should be interpreted as a serious safety event.  In addition, it has been found that manually tripping breakers can significantly change its rated trip setting over time.

 

Of particular interest to the investigators was the IFEN that was certified and installed in the aircraft in 1997 in accordance with an FAA Supplemental Type Certificate (STC).  When SwissAir ordered a suite of IFENs for its fleet, its technical services organization, SR Technics, engaged the services of the IFEN designer, In Flight Technologies (IFT). However, IFT had to engage the services of Hollingsead International (HI) to integrate the IFEN into the aircraft system.  The work would all have to be done in accordance with a FAA Supplemental Type Certificate (STC), which had been granted by the FAA to Santa Barbara Aerospace (SBA).  The Swiss Federal Office of Civil Aviation (FOCA) was willing to accept the FAA-approval, as delegated to SBA.  Thus, roles and responsibilities were arguably spread between four or even five companies and two regulatory authorities, although FOCA did not assume any direct responsibility for authorizing or overseeing the IFEN installation. 

 

The TSB report identifies several irregularities with the installation and documentation of the IFEN, some of it likely caused by the lack of familiarity of HI and SBA staff with the MD-11 or its electrical design philosophy.  FAA monitoring of SBA was also deemed to be lax: a special FAA review done after the crash showed shortcomings in both SBA’s certification procedures and the FAA’s monitoring of the project. SBA subsequently went out of business.

 

There were several in-flight problems reported with SwissAir’s IFEN prior to the crash – overheating and short circuits were noted in several cases. The aircraft’s air-conditioning controller’s range had to be varied to cope with the heating. Inspection of other SwissAir IFEN installations showed installation anomalies. 

 

2. Analysis

The 38 pages comprising this section of the TSB report allow the investigators to marshal their evidence in many of the areas enumerated above.  This is required if the Board is to support the conclusions, and more to the point, to gain the Board’s support for recommendations that might impose significant financial burdens on carriers, regulators, and by extension, travelers and taxpayers. A properly analyzed finding is more likely to result in a conclusion, as will be found in the next section. 

 

This section identified that neither fatigue, nor incompetence on the part of the flight crew or air traffic controllers nor criminal activity directed at the aircraft were involved. However, it did note that all six aircraft power bus feed cables are routed together near the overhead switch, creating a risk that all services provided by these cables could be lost by a single point failure. 

 

Development of Fire

 

What is particularly interesting about this section is the degree to which the investigators, normally disciplined to comment only on facts that can be ascertained, delve into speculation.  As much out of necessity, the words such as likely, could reasonably be linked to, possible appear with unprecedented regularity. The most likely source of ignition for the fire which spread throughout the attic in the cockpit was “an electrical arcing event involving breached wire insulation that ignited nearby MPET-covered insulation material.”  This event likely took place above the cockpit bulkhead.  Investigators believe the fire developed and propagated aft, out of the cockpit ceiling area, and into the ceiling over the galley area. The hot temperatures likely melted the insulation on Tefzel® wiring, which caused arcing, and a tripping of various circuit breakers.

IFEN Design, Installation and Certification

The original design of the IFEN had it wired to the Cabin Bus, which would be the first to be isolated during any emergency load shedding. However, because the Cabin Bus could not provide sufficient electrical power to the original IFEN installation (a full 257 seat configuration) the 115 volt AC Bus was used instead. This change was not signaled to the pilots, who did not know that the IFEN was powered when they may have believed it was not.

The investigation looked at the convoluted manner in which the task of installing the IFEN was managed by SwissAir and regulated by the FAA. The contracting and subcontracting between SwissAir, SR Technics, IFD, HI and SBA almost ensured that responsibilities and accountabilities were diffused. The report stated that along with the hands-off roles played by the FAA and FOCA, “the overall result was the IFEN STC project management structure did not ensure that all the required elements were in place to design, install and certify a system that would be compatible with the MD-11 Type Certificate.”

3. Conclusions

This is a summarization of the most relevant findings:

 

1.      Aircraft standards for material flammability are inadequate. This allowed fire to spread and intensify which ultimately lead to the loss of control of the aircraft.

2.      MPET insulation blankets, duct end caps, fasteners, foams, adhesives are flammable.

3.      Current circuit breaker design does not afford sufficient protection

4.      The fire most likely originated in the cockpit bulkhead area, near a power supply cable for the IFEN. This area lacked a fire detection and suppression system.

5.      Aircrew were expected to use sight and smell to detect smoke.

6.      The lack of an integrated fire-fighting plan lead to more effort being given to landing the aircraft than locating and dealing with the fire.

7.      Certification standards lack consideration of fire as a failure mode.

8.      The lack of access to certain areas in the cabin (i.e. attic) made it difficult, if not impossible to fight fires in those areas.

9.      Checklists for dealing with smoke and fumes were so lengthy (25-35 minutes) that they allowed other ignition sources.

10. Emergency checklists did not emphasize the need to land the aircraft.

11. Shortfalls in aviation industry installation, maintenance and inspection of wire were noted.

12. The fire hazard of contamination (lint, debris, metal swarf etc) is not fully understood by the aviation community.

13. High intensity map-lights were a potential source of fire risk, especially if contamination is present.

14. Aluminum oxygen lines were susceptible to leaking, pin-holing by arcs and rupturing into a blowtorch, exacerbating any fire situation.

15. Best practices with respect to the use of circuit breakers are not yet universal. (i.e. don’t use as a switch and any resets must be justifiable).

16. Both Cockpit Voice and Flight Data recorders should be powered by separate sources, and also from a source independent of the aircraft system.

17. The FAA’s STC process was fundamentally flawed.

18. Databases for capturing wiring anomalies were inadequate.

 


4. Safety Action


The report identifies the safety action that has taken place since the crash, the safety action required and concerns that TSB has about safety.

Safety Action Taken

Some of the safety action taken includes:

 

MD-11 and aircraft wiring: The investigative and regulatory bodies of three countries (Canada, US and Switzerland), the manufacturer (Boeing) and the airline (then SwissAir) have taken action to deal with wiring issues in the MD-11 and wiring in general.


Data Recorders: TSB and NTSB have urged their respective regulatory bodies to require 2 hours of data recordings (vs. the current 30 minutes) and to ensure sources of power that are both independent of each other, and under emergency conditions, independent of the aircraft. 

 

Insulation Materials: TSB recommended that regulatory authorities take urgent action to reduce of eliminate the risk caused by MPET insulation blankets and to validate all insulation materials against more rigorous standards than currently exist.

 

In-Flight Firefighting: TSB made five recommendations to ensure a more aggressive approach to fighting in-flight fires within the accessible and inaccessible areas of the fuselage.

In-Flight Entertainment Systems: TSB recommended a review of the STC process that approved the system in question. This was followed up by the FAA, FOCA and SwissAir, the result being the system in question is no longer approved and is no longer in service.

 

Circuit Breaker Reset Philosophy: TSB noted that a single philosophy on the use of circuit breakers has yet to emerge.

 

Standby Instrumentation: TSB issued two advisories addressing inadequacies in the requirements for standby instruments, noted the lack of requirements for standby communication and navigation equipment, and observed on the lack adequate training in their use under simulated emergency conditions.

 

Material Flammability Standards: TSB recommended revision of standards to preclude any on board materials that would sustain or propagate fire. TSB also recommended more rigorous testing of wiring for failure mode as a potential ignition source or which could exacerbate a fire already in progress.


Safety Action Required

TSB is still calling for safety actions in five areas:


Thermal Acoustic Insulation Materials: Regulatory authorities should develop a more rigorous test regime to prevent the certification of any materials that could sustain or propagate fire.

Interpretation of Materials Flammability Test Results: The TSB recommended that regulatory authorities take action to ensure accurate and consistent interpretation of requirements for flammability.

IFEN STC: TSB recommends that every IFEN system installed under STC should be reviewed for emergency load shedding.

Circuit Breaker Reset Philosophy: TSB recommends that regulatory authorities establish standards for resetting circuit breakers.

Accident Investigation Issues: TSB recommends regulatory authorities take measures to improve the intelligibility of Cockpit voice recordings, implying that pilot boom microphones would provide more useful data than cockpit area microphones. The Board also recommended that Quick Access Recorders, used by many airlines to maintain quality standards, and which often capture many additional parameters not captured by the FDR, be fed to the FDR, where they are more likely to survive a catastrophic event.  Finally, the board recommended that regulatory authorities develop harmonized requirements for cockpit image recording, that could help investigators actually see what was happening in the cockpit, rather than attempting to reconstruct it from FDR and CVR data.

Safety Concerns

TSB identified 10 areas of continuing safety concern. Those not covered here in the interest of space have been mentioned elsewhere in this article.  Many expressed frustration at the slow pace of progress on remedial action.

 

In-Flight Firefighting Measures:  The TSB is concerned that “there was a lack of awareness in the industry about the potential seriousness of odor and smoke events.”  Similarly, the Board “remains concerned with the pace of progress in mandating that all aircraft crews have a comprehensive firefighting plan that starts with the assumption that any smoke situation must be considered to be an out of control fire until proven otherwise, and that an immediate response based on that assumption is required.”


Aircraft Fire-Hardening: The TSB would like to see a more timely response to the need to rid aircraft of flammable materials and “disagrees that the eventual reduction or elimination of flammable materials and anticipated technological advances adequately deal with the near-term risk. Therefore, the Board is concerned that regulatory authorities have not taken sufficient action to mitigate the risks identified in the TSB’s [previous recommendations in this area.]”

 

Aircraft Wiring: TSB remains concerned about the inadequacy of flammability testing requirements for aircraft wire and the limitation of the current Federal Aviation Regulation, FAR 25.1353(b), concerning the installation of wire, which in the Board’s opinion, needs to be resolved. The TSB remains concerned that, the in-service performance of ETFE wire (Tefzel®) may not be fully known. The ropensity for certain types of wiring insulation to wet or dry arc-track needs to be addressed.

 

Contamination: The TSB is concerned that the role of contamination (dust, lint, swarf etc.) in propagating fires is not well enough understood.

 

Arc-Fault Circuit Breakers: Although the TSB felt such devices would provide major improvements over existing circuit breaker technology, they felt that they would not trip the circuit prior to the ignition of nearby flammable material.

Role of FAA: The TSB was concerned that some of the FAA’s authority to approve modifications installed after manufacture had been delegated without sufficient controls being put in place. It found that 10% of In Flight Entertainment systems had been designed, installed and certified without a means for the flight crew to isolate the IFE without interfering with essential aircraft systems.

 

Checklist Modifications: The TSB was concerned that “given a lack of checklist modification and approval standardization within the airline industry, airline operators may unknowingly introduce latent unsafe conditions particularly to emergency checklists.”

 

5.  Interpretation

 

The report was the culmination of a staggering task and represents a mind-numbing attention to an investigative challenge of mind-numbing proportions.  The investigative team, headed by former RCAF pilot Vic Gerden, broke new ground in investigating the accident.   

 

The many ironies of this crash (newish aircraft, reputable operator, competent crew, aircraft bought down, in part by an IFEN that included gambling) were exceeded only by the sheer tragedy of the event. With 229 lives snuffed out, and the loss felt by families, friends and businesses, this was a terrible event.  It is perhaps appropriate the TSB engaged so liberally in speculation on this investigation – to do otherwise would have dishonored the dead, and insulted the living. The report makes sweeping recommendations for the manner in which aircraft are designed, built, maintained, operated and regulated.  And rightly so, as there are still weaknesses in the aviation safety structure, and as readers of this journal appreciate more than any, weaknesses in the safety net that come into action when the primary safety devices fail. 

 

However, it remains to be seen, indeed, it already seems to be all too evident that the full remedial force of this investigation will be treated like so many of its predecessors – given nodding acknowledgement, but insufficient action.  TSB’s frustration, in the safety concern section, is palpable.  It is doubly ironic that in Canada, where there have been two commissions of inquiry previously (The SR 111 crash continues a trend in Canada that there is major crash every 10 years. It began in 1963 with the crash of an Air Canada DC-8 near Montreal, the 1970 crash of another Air Canada DC-8 near Toronto, a series of crashes that lead to the Dubin Commission of Inquiry in 1980 and the crash of an Air Ontario F28 at Dryden in 1989.  Sadly, the recommendations of the previous crashes wax and wane, such that we still find ourselves dealing with issues that were supposed to be addressed, once and for all, as the result of tragedies past.

 

Without taking too much umbrage with an otherwise impressive report, it is noted that passenger oxygen was never deployed: this would only have lasted for 15 minutes in any event and because it mixed oxygen with cabin air, would not have saved passengers from the toxic effects of smoke. Even the flight crew oxygen system, which allowed the pilots to select between normal diluted flow, 100% oxygen or emergency pressure would only have lasted 119 minutes - less time than might be required for an emergency diversion under the worst possible circumstances.

 

There was speculation right after the crash by both lay and expert commentators that the crew might have been able to land the aircraft at Halifax had they been more aggressive in descending and less concerned with following the lengthy checklist for dealing with smoke of unknown origin (and with dumping fuel). Assuming the crew could have controlled the aircraft in the final moments of its flight, the TSB report states that “considering all of the factors, the SR 111 landing would have likely required more runway than the 8,800 feet available on Runway 06 at the Halifax International Airport.”  This would have created a ground event that would have involved an aircraft landing with a substantial amount of fuel and exiting the runway - a major challenge to any ARFF unit.

 

 AFJ readers may find it interesting that the report makes only passing reference (two sentences) to the Halifax airport response team.  The report states that “Aircraft Firefighting Services at Halifax International Airport met the availability and equipment requirements of the CARs.” (Canadian Aviation Regulations),” without citing what category the airport was operating at (Category 8), or observing on the fact that the CARs do not meet ICAO SARPs for a number of criteria, including rescue and response time, even though the Halifax Airport is an internationally listed airport with significant international traffic.  Readers will note from previous articles in AFJ that Canadian regulations do not require any more than one Fire-Fighter per vehicle.  The report did give the Halifax ERS unit full credit for its response time, saying “The Aircraft Firefighting Services were activated at 0120 and, within one minute, the response vehicles were in place adjacent to the runway of intended landing.”  While the report engages in considerable speculation about the origins and effects of the in-flight fire, it does not speculate what might have happened had the aircraft been able to make it to the runway, which was admittedly improbable, aside from the fact that it would have likely gone off the end of the runway, under circumstances of passengers and fuel that would have severely tested Halifax’s emergency response services.

 

TSB investigators found that industry standards for reporting of fleet-wide electrical anomalies lacked the level of detail that would have helped in the investigation. This deficiency in the Service Difficulty Reporting System has subsequently been addressed, at least in part, by the FAA and the airline industry.  The point here is that lack of evidence is not proof of a lack of a problem.

 

The report cited previous studies of in-flight fires were the time between detection and the aircraft crashing varied from 5 to 35 minutes. In the case of SwissAir 111, the time was approximately 21 minutes. Ironically, one of the methods used to detect fire and smoke is by smell, yet, as the report pointed out, the highly efficient air filters in aircraft environmental systems can actually delay the detection of fumes.  Prior to the accident, fumes and smoke were often assumed to be related to the air conditioning vent systems of galley ovens. Operational policy was not to initiate a diversion but instead to follow checklists to identify and deal with the problem - which is exactly what the crew of SwissAir were doing when they ran out of time and control.

                                               

Talking on television, one of the TSB investigators opined that they felt lucky the aircraft hit the water – instantly extinguishing the fire and aside from the catastrophic impact damage, at least preventing further loss of evidence from fire.  Any fire event, be it pre- or post-crash, has the potential to destroy evidence.  It suggests that once all has been done to save the people affected, the fire fighter’s response – and that of regulators and engineers, needs to be focused on saving the evidence from damage.

 

Let us hope that the regulators will not succumb to the same illusion as did the blameless occupants of this flight did: “Out of sight; out of mind.”  This report, dealing with fire in the sky, and its predecessors, dealing with fire on the ground, ought never to be set aside by the passage of time. To do so, is to fail to learn from our mistakes, surely the most certain sign of stupidity.  

The full report can be seen at: http://www.tsb.gc.ca/en/reports/air/1998/a98h0003/eReport/sr111_200303.pdf

 Tefzel Wiring Insulation - Its flaws and an Answer

Mike Murphy

 

 
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