08 July 2002:
Mr. John Britten, Transportation Safety Board (TSB) of Canada, presented
an overview
of the investigation of the SwissAir 111 accident that occurred September
2, 1998 near Peggy’s
Cove, Nova Scotia, Canada. The TSB’s mandate is to advance transportation
safety; conduct
independent investigations; report findings as to accident causes,
contributing factors and safety
deficiencies; make safety recommendations; and effect safety communications.
The approach
taken by the TSB is advance safety through the identification and
validation of safety
deficiencies that are found through the investigation process, focus
on “why” and “how” (i.e.,
“systems approach”), and communicate to the authorities who can best
effect change including
regulators and the aviation industry. The TSB’s safety products include
aviation safety
recommendations, aviation safety advisories, aviation safety information
letters, dialogue with
“change agents,” confidential draft reports with safety issues under
consideration, and final
reports with recommendations and safety concerns.
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| The
Reconstruction |
Mr. Britten
reviewed the flight path and events timeline of the SwissAir 111
accident
from the time the flight crew detected an unusual odor in the cockpit
until the flight data recorder
stopped recording. A synopsis follows (all times are UTC):
• 01:10:38 Flight crew detects unusual odor in cockpit
• 01:12 No unusual odor reported in cabin area. Odor suspected to
be from air conditioning system. Decision is made to divert and
land. Bangor, Maine and Boston, Massachusetts are seen as options
for divert destinations.
• 01:13 Assessment made of some smoke visible in ceiling area of
cockpit.
• 01:14:15 Flight 111 declares “PAN, PAN, PAN,” reports smoke in
cockpit, and requests a diversion to Boston. Flight 111 is cleared
to descend to FL310 and starts a right turn for the diversion.
• 01:15:08 Moncton Centre advises Flight 111 Halifax airport is
a closer alternative
for landing.
• 01:15:36 Flight 111 indicates that Halifax is the preferred diversion
airport.
• 01:19:37 Flight 111 is informed by Moncton Centre that they are
30 miles from the threshold of Runway 06.
• 01:19:50 Flight 111 informs Moncton Centre that they will need
more than 30 miles (at 21,000 feet).
• 01:21:27 Flight 111 informs Moncton Centre that they must dump
fuel before landing.
• 01:21:56 Flight 111 indicates to Moncton Centre that they are
able to accept a turn to the south to dump the fuel.
• 01:22:01 Flight 111 is cleared by Moncton Centre to turn left
to a heading of 200 degrees, and to maintain 10,000 ft.
• 01:23:30 Flight 111 is cleared by Moncton Centre to continue turning
left to a heading of 180 degrees.
• 01:24:09 The aircraft autopilot disconnects.
• 01:24:42 Flight 111 informs Moncton Centre that they are declaring
an emergency.
• 01:24:53 Flight 111 informs Moncton Centre that they are starting
fuel dumping and must land immediately.
• 01:25:40/41 FDR and CVR stop recording information.
• 01:31:18 Aircraft strikes the water.
The initial operational elements following the accident were:
• Communication – families considered first; providing facts, not
speculation, was very important
• Coordination – initial participants included various Government
and public services organizations, as well as the US NTSB, Swiss
AAIB, SwissAir, and Boeing
• Family Assistance – SwissAir and Delta had primary responsibility,
with the RCMP, Medical Examiner and TSB having roles as well.
• Criminal (Police) & Coroner’s Investigation
• TSB Safety Investigation
• Recovery of human remains
• Identification of remains
• Recovery of wreckage
• Personal effects
The aircraft wreckage was located in 200 meters of water, in a debris
field approximately
the size of a football field. Surface ships were the first units
to arrive on scene for search and
rescue efforts, and were later joined by aircraft. Side-scan radar
operations from surface ships
were conducted to assist in locating the wreckage, and a Canadian
submarine also assisted with
the search. Initial recovery efforts, involving dive teams, concentrated
on the recovery of human
remains. Joint US-CA diving efforts continued for approximately
two weeks. The six main
recovery methods were water surface and beaches, divers (CDN Navy,
CCD, USN Grapple),
heavy lift barge, scallop dragger, remotely operated vehicles, and
a dredge ship. Each of the six
main recovery methods contributed effectively to the retrieval of
victims and wreckage, and
much of what was done was without precedent. By December 1998, 100%
victim identification
had been completed. More than 2 million aircraft pieces were recovered
during the operation,
representing 98% of the total wreckage.
The investigation team reconstructed the forward 300 inches of the
aircraft, which is
where most signs of burning were found. Circuit breaker panels with
indications they had been
subjected to extreme heat and arced wires, both ship and after market,
were found in the
recovered wreckage. Investigation techniques included database tracking,
temperature
templates, photogrammetry panoramas, object modeling, 3-D CAD modeling,
and electronic
document conversion and management. Analysis of rotating components
was also conducted.
The technical challenge that the investigation team faced involved
the degree of destruction,
small/unidentifiable/missing parts, extensive fire damage, arced
electrical wires, flight recorder
limitations, and the multiple investigative techniques that were
required. The volume of the
pieces of wreckage also posed a significant challenge. Of the more
than 2 million pieces of
wreckage recovered, more than 21,000 were tracked (14,700 aircraft
wreckage related, 2100
personal belongings, 4200 medical/other). There were also more than
13,700 paper documents
and 100,000 emails, approximately 2000 heat damaged electrical wires
and components, 160
miles of wire (average 3 ft lengths), and over 150,000 photos and
600 videos associated with the
investigation. Mr. Britten advised that selected SwissAir 111 safety
communications are
available at the TSB Internet web site www.tsb.gc.ca.
As of 19 June 2002, the TSB has issued 14 Aviation Safety Recommendations,
four
Aviation Safety Advisories, and two Aviation Safety Information
Letters, and has conducted
informal liaison with “agents of change.” On 9 March 1999 the TSB
issued a Safety Deficiency
for flight recorder duration and power supply that addressed the
short (30-minute) duration of
cockpit voice recorders, the need for an independent power supply,
and the concern for
separate
electrical buses. On 11 August 1999 another Safety Deficiency was
issued that
identified
shortcomings in the in-service fire resistance of metallized polyethylene
terephthalate (PET)
covered insulation blankets in aircraft, which was found to burn
quite readily, and the
flammability test criteria currently being used. Another Safety
Deficiency was issued on 4
December 2000 that identified the lack of a coordinated and comprehensive
approach to in-flight
firefighting, insufficient smoke/fire detection and suppression
systems, the need to recognize the
importance of making prompt preparations for a possible emergency
landing, the excessive time
required to troubleshoot smoke/fire problems, and the inadequate
access to critical areas within
aircraft. On 27 August 2001 another Safety Deficiency was issued
that identified the need for
aircraft flammability standards that prevent the use of materials
that sustain or propagate fires,
certification tests to evaluate a wire’s failure characteristics
under realistic conditions, and
addressing systems whose fire induced failure may exacerbate a fire
in progress (e.g., oxygen
systems).
Aviation Safety Advisories have been issued that deal with MD-11
wiring, MD-11 flight
crew reading light installations, controller knowledge of flight
crew emergency procedures, and
MD-11 standby (secondary) instruments. Aviation Safety Information
Letters have been issued
that address flight crew reading light design and overhead aisle
and emergency lights. Mr.
Britten stated there have been numerous safety actions taken globally
that involve procedures,
checklists, equipment, design and airworthiness directives (ignition
sources and thermal acoustic
insulation material). He added that the FAA has taken safety actions
regarding ignition sources,
flight crew reading lights, fuels (thermal acoustic insulation cover
material), in-flight
firefighting, in-flight entertainment systems, wiring, flammability
standards, and flight recorders.
Mr. Britten concluded with a review of safety issues that remain
under consideration:
• Residual risk –
- MD-11 wiring
- Flight recorder duration and power supply
- Flight crew reading light
- Thermal acoustic insulation material
- In-flight firefighting
- Material flammability standards
• Supplemental Type Certificate Process
• Circuit Breaker Reset Philosophy
• Investigative techniques
- Quality of CVR information
- QAR data
- Image recording
- Non-volatile memory
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