Tuesday, June 30, 2009

Air France Flight 447

Air France Flight 447 was a scheduled commercial flight from Rio de Janeiro, Brazil, toParis, France, on 1 June 2009 that broke apart in flight and fell into the Atlantic Oceanwith the loss of all 216 passengers and 12 crew members.[2]

The aircraft, an Air France Airbus A330-200 registered as F-GZCP, took off on 31 May 2009 at 19:03 local time (22:03 UTC). The last contact with the crew was a routine message to Brazilian air traffic controllers at 01:33 UTC, as the aircraft approached the edge of Brazilian radar surveillance over the Atlantic Ocean, en-route to Senegalese-controlled airspace off the coast of West Africa. Forty minutes later, a four-minute-long series of automatic radio messages was received from the plane, indicating numerous problems and warnings. The exact meanings of these messages are still under investigation, but the aircraft is believed to have been lost shortly after it sent the automated messages.[3]


Air France Flight 447
Air France Airbus A330-200 aircraft, similar to the one used for Flight 447
Accident summary
Date1 June 2009
TypeUnder Investigation
Site
(approximate)
Passengers216
Crew12
Fatalities228
Survivors0
Aircraft typeAirbus A330-200
OperatorAir France
Tail numberF-GZCP
Flight originRio de Janeiro-Galeão International Airport
DestinationParis-Charles de Gaulle Airport




























Investigation

East-west cross-section of Atlantic Ocean portion in which Air France Flight 447 crashed, showing depth of the sea floor. The vertical scale is greatly exaggerated for contrast purposes.

The cause of the crash is unknown. France's Bureau d'Enquêtes et d'Analyses pour la Sécurité de l'Aviation Civile (BEA) is in charge of the official investigation.[87] The BEA released a press release on 5 June, that stated: [88]

A large quantity of more or less accurate information and attempts at explanations concerning the accident are currently being circulated. The BEA reminds those concerned that in such circumstances, it is advisable to avoid all hasty interpretations and speculation on the basis of partial or non-validated information. At this stage of the investigation, the only established facts are:

  • the presence near the airplane’s planned route over the Atlantic of significant convective cells typical of the equatorial regions;
  • based on the analysis of the automatic messages broadcast by the plane, there are inconsistencies between the various speeds measured.

BEA[89]

The main task currently occupying the investigators is recovering parts of the aircraft, primarily the flight recorders. BEA chief Paul-Louis Arslanian said that he is not optimistic about finding them since they may be under as much as 3,000 m (9,800 ft) of water and the terrain under this portion of the ocean is very rugged.[90] Investigators are hoping to find the aircraft's tail, since the black box is located there.[91] Although France has never recovered a black box from similar depths,[90] there is precedent for such an operation: in 1988, an independent contractor was able to recover the cockpit voice recorder of South African Airways Flight 295 from a depth of 4,900 m (16,000 ft) in a search area of between 80 and 250 square nautical miles (270 and 860 km2).[92][93] The black box contains a water-activated acoustic "pinger", which should remain active for 30 days, allowing search for the location of the signal origin.[94]

[edit]Airspeed inconsistency

Prior to the disappearance of the aircraft, the automatic reporting system, ACARS, sent messages indicating disagreement in the indicated air speed (IAS) readings. A spokesperson for Airbus claimed that "the air speed of the aircraft was unclear" to the pilots.[64] Paul-Louis Arslanian, of France's air accident investigation agency, confirmed that F-GZCP previously had problems calculating its speed as did other A330 aircraft stating "We have seen a certain number of these types of faults on the A330 ... There is a programme of replacement, of improvement".[95] The problems primarily occurred on the Airbus A320, but, awaiting a recommendation from Airbus, Air France delayed installing new pitots on A330/A340 yet increased inspection frequencies.[96]

There have been several cases where inaccurate airspeed information led to flight incidents on the A330. Two of those incidents specifically involved pitot probes, one of the types of sensor used to measure airspeed.[97][Note 3] In the first incident, an Air France A340-300 (F-GLZL), en route from Japan to France, experienced an event at 31,000 feet (9,400 m) in which the airspeed was incorrectly reported and the autopilotautomatically disengaged. Bad weather together with obstructed drainage holes in all three pitot tubes were subsequently found to be the cause.[98] In the second incident, an Air France A340-300 (F-GLZN) en-route to New York encountered turbulence followed by the autoflight systems going offline, warnings over the accuracy of the reported airspeed and two minutes of stall alerts.[98]

On 6 June 2009, Arslanian said that Air France had not replaced pitot probes as Airbus recommended on F-GZCP, saying that "it does not mean that without replacing the probes that the A330 was dangerous."[96] Air France issued a further clarification of the situation:

"1) Malfunctions in the pitot probes on the A320 led the manufacturer to issue a recommendation in September 2007 to change the probes. This recommendation also applies to long-haul aircraft using the same probes and on which a very few incidents of a similar nature had occurred."

Since it was not an airworthiness directive (AD), the guidelines allow the operator to apply the recommendations at its discretion. However, Air France implemented the change on its A320 fleet where the incidents of water ingress were observed.

"2) Starting in May 2008 Air France experienced incidents involving a loss of airspeed data in flight (see two incidents above) in cruise phase on A340s and A330s. These incidents were analysed with Airbus as resulting from pitot probe icing for a few minutes, after which the phenomenon disappeared."

After discussing these with the manufacturer, Air France sought a means of reducing these incidents, and Airbus indicated that the new pitot probe designed for the A320 was not designed to prevent cruise level ice-over. However, in 2009 tests suggested that the new probe could improve its reliability, prompting Air France to initiate and accelerate the replacement program,[99] however not before F-GZCP underwent its major overhaul on April 16.[100] On 4 June, Airbus issued an Accident Information Telex to operators of all Airbus models reminding pilots of the recommended Abnormal and Emergency Procedures to be taken in the case of unreliable airspeed indication.[101] By 17 June 2009, Air France has replaced all Pitot tubes on its A330 type aircraft.[84]

French Transport Minister, Dominique Bussreau, said "Obviously the pilots [of Flight 447] did not have the right speed showing, which can lead to two bad consequences for the life of the aircraft: under-speed, which can lead to a stall, and over-speed, which can lead to the aircraft breaking up because it is approaching the speed of sound and the structure of the plane is not made for resisting such speeds".[102] On 11 June 2009, a spokesman from the BEA reminded that there was no conclusive evidence at the moment linking Pitot malfunction to the AF447 crash, and this was reiterated on 17 June 2009 by the BEA chief, Paul-Louis Arslanian.[84][103][104]

The incident which befell Flight 447 has some parallels with incidents involving A330 aircraft flown by other carriers.[105][106][107][108] Three similar reports are on file at the Australian Transport Safety Bureau (ATSB), with two incidents relating to Airbus A330 with the flight computer problems, plus one which involved a Boeing 777.[Note 4][109] In the October 2008 incident, this fault caused injuries to passengers and damage to the aircraft on Qantas Flight 72, en route from Singapore to Perth, Western Australia, which was forced into a dive by a malfunctioning ADIRU. These incidents often started with the autopilot disengaging and sending ADIRU failure messages. Incorrect speed indications were also observed.[109] The type of airframe and model of ADIRU involved in the Qantas Flight 72 incident were also previously involved in another incident on Qantas Flight 68, 2006.[98] A memo leaked from Airbus suggests that there was no evidence of ADIRU malfunction on Flight 447 similar to the failure in the Qantas incidents.[110] However, the Qantas aircraft were equipped with ADIRUs manufactured by Northrop Grumman, while Flight 447 was equipped with an ADIRU manufactured by Honeywell.[106]




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