Accident Overview

On September 2, 1998 Swiss Air Flight 111, a Boeing/McDonnell Douglas MD‑11, departed John F. Kennedy (JFK) International Airport, New York at 0018 UTC (2018 EDT) on a flight to Geneva, Switzerland. The flight included 215 passengers, and a crew of two pilots and twelve flight attendants. Approximately one hour into the flight, the pilots detected an unusual smell. Fourteen minutes later the pilots declared an emergency. Six minutes after the declared emergency, Flight 111 impacted the ocean about five nautical miles southwest of Peggy’s Cove, Nova Scotia, Canada. The aircraft was destroyed and there were no survivors.

History of Flight

 

0018.00 UTC Departs JFK

0110.38 UTC–The first indication to the flight crew of an anomalous situation was their detection of a strange odour in the flight deck. The flight crew noticed some smoke in the flight deck, but it appeared to dissipate. When a flight attendant was queried, it was determined that there was no evidence of smoke or odours in the cabin. The flight crew decided that the odour and smoke was associated with the air conditioning system.

0114.15–while 66 nautical miles southwest of Halifax, the flight made a PAN PAN PAN radio transmission, and indicated to air traffic control that there was an in‑flight problem in progress and the crew requested a diversion to a convenient place, initially requesting a return to Boston which was 300 nautical miles behind them. The controller suggested Halifax, which by then was only 56 nautical miles away. The flight crew donned oxygen masks at this time.

0116.34–the controller cleared the flight to descend to 10,000 feet. Following a handoff to another air traffic controller, the flight was further cleared to 3,000 feet. The crew requested an intermediate altitude of 8,000 feet until the cabin was ready for landing

0117.50–cabin crew informed

0119.37–30 miles from threshold

0119.38–from this time a series of communications with air traffic control attempted to position the airplane for an extended approach into Halifax. At this time, the crew informed ATC that fuel dumping would be required prior to landing at Halifax, so a series of manoeuvres was begun to position the airplane for fuel jettisoning and then an approach to Halifax.

0120.48–fuel dumping discussed by flight crew

0122.27-closest point to airport

0123.53–the flight was positioned 35‑40 nautical miles from Halifax in case they needed to get to the airport in a hurry. The flight crew acknowledged and asked for clearance to begin dumping fuel, and further requested a block altitude of 9,000 to 11,000 feet. The controller cleared the flight for any altitude between 5,000 and 12,000 feet.

0124:42–the flight declared an emergency (Mayday Mayday Mayday) and indicated that an immediate landing was necessary. The flight also informed the ATC controller that fuel dumping had commenced.

0124.09–Autopilot 2 disconnects.

0124.09–Descent begun, clearance to descend was initially given at 0116

0125:02, the flight again declared an emergency. The controller acknowledged this transmission, which was the final communication from Swissair Flight 111.

0125.41– VHF and Flight Recorders lost

0126.04—Transponder unserviceable

0130–approximately, observers on the ground saw a large aircraft fly overhead and heard its engines.

0131–several observers heard a sound described as a loud clap; seismographic recorders in the region also recorded a seismic event at 0131:18, which coincided with the time the aircraft struck the water

System Failures

During the descent, beginning at 0124:09 (descent clearance by ATC given at 0116) and continuing for the next 92 seconds until the flight data recorder stopped functioning, multiple system failures were recorded. The first event was the disconnection of the autopilot. At 0124:18, both pilots confirmed that the autopilot had disconnected, and its associated aural warning tone continued until the cockpit voice recorder ceased recording. The Canadian TSB speculated in the accident report that the flight crew may have attempted to engage the other autopilot at this point, but there was no evidence that it engaged, and the aural warning did not cease, indicating that the circuitry for warning cancellation may have already been compromised by the fire

At 0124:46, the cabin crew informed the flight crew that electrical power in the cabin had been lost, and the cabin crew was using flashlights to continue landing preparation. The accident report indicated that this may have been the result of the flight crew depowering the cabin electrical bus, per procedure. At 0124:54, the failure of lower yaw damper A was annunciated, followed by the annunciated failure of flight control computer 1 at 0124:57.

At 0125:06, the left emergency AC bus failed, followed immediately by the loss of airspeed, altitude, and total air temperature indications. At the same time, the transponder mode C, which transmits altitude information, stopped transmitting, but transponder mode A (which transmits aircraft identification) continued transmitting. Also, at this time, the pilot’s instrument displays went blank.

At 0125:33, the first officer reported that his instrument displays were all blank, followed by the failure of upper yaw damper A. Following these failures, the flight data recorder failed, so no further information was recorded. At 0125:41, the cockpit voice recorder also failed

At 0126:04, both the Mode A, and Mode C transponder signals failed. At some point following the failure of the data recorders, engine No. 2 experienced a loss of thrust resolver angle, which would cause thrust to remain fixed at the value present when the failure occurred. The investigation further concluded that fire‑related wire failures in the flight deck ceiling could also have resulted in a No. 2 engine fire warning, causing the flight crew to shut down that engine. Wreckage examination results were consistent with that engine not operating at impact.

 

3.1 Findings as to Causes and Contributing Factors

1. Aircraft certification standards for material flammability were inadequate in that they allowed the use of materials that could be ignited and sustain or propagate fire. Consequently, flammable material propagated a fire that started above the ceiling on the right side of the cockpit near the cockpit rear wall. The fire spread and intensified rapidly to the extent that it degraded aircraft systems and the cockpit environment, and ultimately led to the loss of control of the aircraft
2. A segment of in‑flight entertainment network (IFEN) power supply unit cable (1‑3791) exhibited a region of resolidified copper on one wire that was caused by an arcing event. This resolidified copper was determined to be located near manufacturing station 383, in the area where the fire most likely originated. This arc was likely associated with the fire initiation event; however, it could not be determined whether this arced wire was the lead event.
3. There were no built‑in smoke and fire detection and suppression devices in the area where the fire started and propagated, nor were they required by regulation. The lack of such devices delayed the identification of the existence of the fire and allowed the fire to propagate unchecked until it became uncontrollable.
4. There was a reliance on sight and smell to detect and differentiate between odour or smoke from different potential sources. This reliance resulted in the misidentification of the initial odour and smoke as originating from an air conditioning source.
5. There was no integrated in‑flight firefighting plan in place for the accident aircraft, nor was such a plan required by regulation. Therefore, the aircraft crew did not have procedures or training directing them to aggressively attempt to locate and eliminate the source of the smoke, and to expedite their preparations for a possible emergency landing. In the absence of such a fire fighting plan, they concentrated on preparing the aircraft for the diversion and landing.
6. There is no requirement that a fire‑induced failure be considered when completing the system safety analysis required for certification. The fire‑related failure of silicone elastomeric end caps installed on air conditioning ducts resulted in the addition of a continuous supply of conditioned air that contributed to the propagation and intensity of the fire.
7. The loss of primary flight displays and lack of outside visual references forced the pilots to be reliant on the standby instruments for at least some portion of the last minutes of the flight. In the deteriorating cockpit environment, the positioning and small size of these instruments would have made it difficult for the pilots to transition to their use, and to continue to maintain the proper spatial orientation of the aircraft

3.2 Findings as to Risk

2. 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.
3. 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.
4. 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 the cabin crew were using flashlights while preparing for the landing, which potentially could have slowed their preparations.
5. 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.
6. 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.
7. While the SR Techniques 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.
8. The Swiss Federal Office for Civil Aviation audit procedures related to the SR Techniques QA program did not ensure that the underlying factors that led to specific similar audit observations and discrepancies were addressed

3.3 Other Findings

2. The 13‑minute gap in very‑high frequency communications was most likely the result of an incorrect frequency selection by the pilots.
3. The pilots made a timely decision to divert to the Halifax International Airport. Based on the limited cues available, they believed that although a diversion was necessary, the threat to the aircraft was not sufficient to warrant the declaration of an emergency or to initiate an emergency descent profile.
4. The flight crew were trained to dump fuel without restrictions and to land the aircraft in an overweight condition in an emergency, if required.
5. From any point along the Swissair Flight 111 flight path after the initial odour in the cockpit, the time required to complete an approach and landing to the Halifax International Airport would have exceeded the time available before the fire‑related conditions in the aircraft cockpit would have precluded a safe landing. If emergency had been declared earlier, any other military or civil airports within range
6. Air conditioning anomalies have typically been viewed by regulators, manufacturers, operators, and pilots as not posing a significant and immediate threat to the safety of the aircraft that would require an immediate landing. Crash near Athens of a B737 where the crew was incapacitated due aircraft failing to pressurize on departure
7. Actions by the flight crew in preparing the aircraft for landing, including their decisions to have the passenger cabin readied for landing and to dump fuel, were consistent with being unaware that an on‑board fire was propagating.
8. Air traffic controllers were not trained on the general operating characteristics of aircraft during emergency or abnormal situations, such as fuel dumping.
9. The first officer’s seat was occupied at the time of impact. It could not be determined whether the captain’s seat was occupied at the time of impact.
10. The pilots shut down Engine 2 during the final stages of the flight. No confirmed reason for the shutdown could be established; however, it is possible that the pilots were reacting to the illumination of the engine fire handle and FUEL switch emergency lights. There was fire damage near a wire that, if shorted to ground, would have illuminated these lights.
11. When the aircraft struck the water, the electrically driven standby attitude indicator gyro was still operating at a high speed; however, the instrument was no longer receiving electrical power. It is unknown whether the information displayed at the time of impact was indicative of the aircraft attitude.
12. Coordination between the pilots and the cabin crew was consistent with company procedures and training. Crew communications reflected that the situation was not being categorized as an emergency until about six minutes prior to the crash however, soon after the descent to Halifax had started, rapid cabin preparations for an imminent landing were underway.
13. No smoke was reported in the cabin by the cabin crew at any time prior to CVR stoppage; however, it is likely that some smoke would have been present in the passenger cabin during the final few minutes of the flight. No significant heat damage or soot build‑up was noted in the passenger seating areas, which is consistent with the fire being concentrated above the cabin ceiling.

Courtesy of Wikipedia.org