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Old 3rd Jun 2009, 12:55
  #685 (permalink)  
Dutch Bru
 
Join Date: Aug 2008
Location: Belgium
Age: 59
Posts: 72
On the likelihood of DFDR and CVR salvage


The Indonesian Adam Air B734 that crashed in the Makassar Strait off Sulawesi on 1 January 2007 had its DFDR and CVR located after 3 weeks at depths of 2000m and 1900m respectively. According to the accident report underwater locator beacon (ULB) signals from the flight recorders were picked up on 21 January 2007 by a US oceanographic vessel Mary Sears and their positions logged.

Just to give an idea of some of the constraints concerning this type of operations, according to the accident report: "Mhe Mary Sears was required to pass within 500 meters of a beacon before it could detect a return. The US Navy Supervisor of Salvage shipped a towed pinger locator (TPL) from Washington, DC, to Makassar. This device is a sonic detector with umbilical cable capable of detecting the underwater locator beacons from the PK-KKW flight data recorder and cockpit voice recorder (if they are still operating), down to a depth of 20,000 feet." The speed with which the TPL was towed through the water was 2-4 kts in the case of the Adam Air B734.

Due to several circumstances (including an initial lack of specialised equipment and disputes about the costs of the salvage operations), the actual salvage started only on 24 August 2007, with the DFDR and CVR being retrieved from the ocean floor by Phoenix International on 27 and 28 August respectively. Functional data were retrieved from both recorders.

Also to give an idea of the specificities of this type of operation, the following text from the accident report: "The underwater survey and recovery used a small ROV, Remora 6000, which was capable of descending to a water depth of 3000 meters. The ROV had three visual cameras and two fixed lights fitted on the front of the vehicle, which were used for visual scanning. The visual range of the camera was about 10 meters. The ROV was also equipped with underwater sonar with good resolution horizontally up to 100 meters. The width of the sonar beam is about 50 meters at a distance 100 meters from an object. The position of the ROV relative to the ship was measured using an underwater positioning system and the ship used differential global positioning system equipment. The coordinates provided by the ship and the ROV were used to mark the location of the aircraft wreckage and these were mapped into a computer. The ROV had a pair of robot arms that were capable of lifting a 25 kg object of a maximum dimension of about 30 cm by 40 cm. The ROV was in the water for about 109 hours and completed five dives."

Although the AF A332 wreckage is arguably at greater depth (between half and double as deep) then that of the Adam Air B734, the above may give an idea of the challenges and constraints of the salvage operations with regard to the AF 332 DFDR and CVR. It would not be impossible though, since the salvage company at the time, Phoenix Intl, states on its website that 6000m is now the max depth of its remotely operated vehicle (ROV), provided of course that the ULB signals are picked up and pinpointed within 30 days.

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