What happened
On 2 September 1998, a McDonnell Douglas MD-11 operating as Swissair Flight 111 departed New York's JFK International Airport for Geneva, Switzerland. The aircraft was carrying 215 passengers and 14 crew members. Approximately 53 minutes into the flight, while cruising at flight level 330, the flight crew detected an unusual odor in the cockpit.
As the crew investigated, they observed smoke, which they attributed to the aircraft's air conditioning system. The pilots initially intended to divert to Boston, but after consulting with air traffic services, they elected to head toward Halifax International Airport in Nova Scotia, Canada. During the descent and approach, the crew began discussing fuel dumping to manage the aircraft's weight.
As the flight progressed, a rapid succession of critical system failures began to occur. The aircraft's flight data recorder captured a series of malfunctions, and the crew declared an emergency, stating they needed to land immediately. Shortly thereafter, radio communications were lost, and the flight recorders ceased functioning. Approximately 20 minutes after the initial smell was detected, the aircraft struck the ocean surface near Peggy's Cove, Nova Scotia. The impact destroyed the aircraft, and there were 229 fatalities.
The investigation
The investigation into the loss of Flight 111 was a complex undertaking involving the examination of technical, operational, and maintenance factors. Investigators analyzed the flight profile, the aircraft's systems, and the sequence of events leading up to the loss of contact. The inquiry also looked into the impact of various supplemental type certificates (STCs) on the aircraft's electrical systems and the adequacy of existing circuit breaker designs.
Findings
- A fire was spreading above the aircraft ceiling in the forward section, which the crew was unaware of during their descent.
- The rapid failure of aircraft systems followed the detection of smoke and preceded the loss of communication.
- The investigation identified concerns regarding the certification of certain electrical components, specifically how some non-essential systems could interfere with essential aircraft functions when power is removed.
- There were identified risks associated with the design of arc-fault circuit breakers and their ability to prevent the ignition of flammable materials.
- The investigation noted that the modification of emergency checklists by operators could potentially introduce latent safety risks if not standardized.