Air France Flight 447 Disaster, 1st June 2009
In June 2009, an Airbus 330 flying from Rio de Janeiro, Brazil to Paris, France went missing over the Atlantic Ocean. For nearly two years the fate and whereabouts of its 12 crew members and 216 passengers remained a mystery until unmanned submarines discovered the wreckage in April 2011. Using the data recorded by the recovered black boxes of the aircraft, the French civil aviation safety investigation authority, the BEA, were able to write a final report on the accident, concluding that the crash had occurred due to "the absence of any training, at high altitude, in manual aeroplane handling", "low exposure time in training to stall phenomena, stall warnings and buffet", and "the crew’s failure to diagnose the stall situation and consequently a lack of inputs that would have made it possible to recover from it" after the Captain had left the two co-pilots to fly the plane while he rested (BEA, 2012).
‘Black boxes’ consist of a flight data recorder (FDR) and a cockpit voice recorder (CVR), sometimes combined in the same unit. The FDR is situated at the highest point of the plane, usually the tip of the tail fin, and collects parameters required to determine accurately the aeroplane flight path, speed, altitude, configuration and operation. The CVR records and stores the audio of the microphones and earphones of the pilots’ headsets and of an area microphone installed in the cockpit. These systems can help investigators in the case of an accident consider whether the cause was a pilot error or a system failure.
The first prototype 'black boxes' designed to be used to provide crucial information following airplane crashes, were produced in 1956 by David Warren of the Aeronautical Research Laboratories in Melbourne, Australia, after three Comet 1 crashes caused the whole fleet to be grounded. Warren was involved in the accident investigation and realised that it would be useful for investigators if there had been a recording of what had happened on the plane just before the crash (What is a Black Box?).
The “coding apparatus” for flight recorders - which maintains a continuous recording of aircraft flight data such as engine exhaust, temperature, fuel flow, aircraft velocity, altitude, rate of descent and other vital information - was first invented and patented by Professor James 'Crash' Ryan, a mechanical engineer at the University of Minnesota (Ryan, 1960). The patent for the device was approved in November 1960 following the Trans Australia Airlines Flight 538 crashing into the sea that same year.
It is now required by the International Civil Aviation Organisation that a FDR and CVR be installed in all aircraft with a maximum certificated take-off mass of over 5700kg with the capability to survive conditions likely to be encountered in a severe accident. This includes withstanding an impact of ±3400g for 6.4ms, a penetrative resistance of 500lbs over a quarter square inch, temperatures of 1100°C for 30-60 minutes or 260°C for 10 hours, and the hydrostatic pressure of 20,000ft under sea level for 30 days. These regulations are the bare minimum (ICAO, 1990).
When FDRs and CVRs were first introduced, they consisted of a tape recorder that could hold two hours of voice recordings and up to ten hours of data information. However tapes were very easily damaged due to its moving parts, and the quality of any recordings could be affected by sudden movement from turbulence or impact. In 1985 the solid state boxes known today were first introduced, which are far more difficult to damage. Because they sink quickly, they now contain an emergency location transmitter (ELT) that produces a 2km signal for 30 days to make it easier for them to be discovered in the case of an aircraft accident at sea.
In the case of Flight AF447, the FDR indicated that the aircraft's three pitot tubes became clogged with ice, causing the loss of accurate airspeed indications, a situation not anticipated by the design engineers of the aircraft. The loss of airspeed indications caused the autopilot, flight director, and autothrust to disconnect, leaving the co-pilots in full control of the plane. The pilot flying, PF, reacted by pulling the plane into a steep climb and stalling it. The stall warning sounded for fifty seconds, but neither pilot mentioned that they were stalling. The co-pilot not flying - PNF - "asked the PF several times to descend" (BEA, 2012). Although Bonin did reduce the vertical speed, thus stopping the stall warning, he didn't pull the plane fully out of the climb and soon the stall warning was sounding again.
The final report of the accident states that "from an operational perspective, the total loss of airspeed information that resulted from this was a failure that was classified in the safety model", leading to the autopilot disabling. The sudden loss of autopilot caused "the failure of the attempts to understand the situation and the de-structuring of crew cooperation fed on each other until the total loss of cognitive control of the situation". With neither co-pilot able to recognise the required response in order to recover the stall, the plane fell 37,500ft into the sea.
The Federal Aviation Administration (FAA) published a report in 2013 based on accident and incident data collected from black boxes between 2001 and 2009, including the disaster of flight AF447. The study states that "pilots sometimes rely too much on automated systems and may be reluctant to intervene" as well as lacking "in-depth knowledge and skills to most efficiently and effectively accomplish the desired flight path management related tasks". As a result encourage airline pilots to maintain proficiency in manual flying and "develop guidance for flightcrew strategies and procedures to address malfunctions for which there is no specific procedure" to ensure that the same mistakes are not made again (FAA, 2013).
BEA. (2012). Flight AF 447 Final Report. Le Bourget: BEA.
FAA. (2013). Operational Use of Flight Management Systems, Report of the PARC/CAST Flight Deck Automation WG. Washington: FAA.
ICAO. (1990). ICAO Annex 6 Volume 1 Section D.
Ryan, J. (1960). Flight Recorder. Minnesota: US Patent.
What is a Black Box? (n.d.). Retrieved from National Geographic Channel: http://natgeotv.com/uk/air-crash-investigation/black-box