French investigators have detailed the new South Atlantic search location for the cockpit and data recorders of Air France flight AF447, following the refinement of signals detected last year by a nuclear submarine.
The initial search phase following the loss of the Airbus A330 on 1 June 2009 was based on a region lying largely within, as well as to the north of, a circle of 40nm (74km) radius centred on the aircraft's last known position.
During an initial recovery phase last year the submarine Emeraude had concentrated on searching the western and southern part of this region, while the northern and eastern part - including the area viewed as the most likely crash site - was allocated to towed pinger locators, which were considered more efficient.
Although not designed to track acoustic beacons of the type fitted to the flight recorders of AF447, the submarine's detection capabilities were enhanced during this initial search, increasing from a 2,000m (6,600ft) distance, over 10-30 June, to 3,200m over 1-10 July.
The French defence ministry says that specialists have used a new algorithm to re-examine acoustic signals detected on 1 July. Following this analysis, says the ministry, these specialists have determined that the submarine's equipment could have picked up transmissions from the flight recorders.
While the ministry says that locating the recorders is "far from a certainty", French investigation agency Bureau d'Enquetes et d'Analyses has identified a new search zone, measuring some 14nm by 6nm but located on the southwestern rim of the original 40nm circle.
This point is also some 40nm from the last known position of the A330, on a bearing approaching the opposite of its direction of travel on the Rio de Janeiro-Paris air route.
One of the vessels involved in an intensive search during April - over a primary zone to the north of the A330's last known position - is to conduct a sweep of the area. The vessel, the Seabed Worker, is supported by autonomous underwater vehicles.