The casing or chassis of the flight data recorder from Air France flight AF447 has been found (above) at a depth of 4000 metres  at the mid Atlantic crash site but the memory module is missing.

This diagramatic photo, also released by the French accident investigator, the BEA, shows the chassis and missing component before being enclosed in the unit, which records the operations of a very wide range of systems and functions during a flight.

The flight data recoder mounting and memory module: BEA image

The chassis photo was taken overnight on the first dive of a remote controlled device (a Remora 6000) from the search and recovery vessel Ile de Sein, which has cranes capable of lifting up to 5 tonnes at a time to the surface.

The BEA hasn’t said anything about how the dislodging of the memory module from its chassis might affect its readability if it is also found and recovered.

All 228 people on board AF447 died on June 1, 2009, when the Air France Airbus A332  crashed during a flight from Rio de Janeiro to Paris.

The jet was also equipped with a cockpit voice recorder. This and the flight data recorder are designed to survive severe impact stress.

The recovery ship will also attempt to retrieve human remains that were found inside sections of the wreckage when it was located by a search vessel early in April, as well as other aircraft components that may reveal more about the state of the jet before it crashed while flying through a belt of tropical storms.