Says Contacts Are Old, Had Been Previously Discounted

The Australian Transportation Safety Bureau (ATSB) says that recent articles suggesting that sonar images gathered during the underwater search for MH370 could be aircraft debris are incorrect.

The sonar contacts mentioned in the articles are old ones that were already assessed and discounted months ago.

The ATSB says the articles also incorrectly describe ‘Category 3’ sonar contacts as being the most likely to be aircraft debris. In fact, they are the least likely to be aircraft debris. Category 3 is assigned to sonar contacts that are of some interest as they stand out from their surroundings but have low probability of being significant to the search. The underwater search so far has identified more than 400 seabed features that have been classified as Category 3.

According to the ATSB website, there are three classifications for sonar contacts which are identified during the course of the underwater search.

Classification 3 is assigned to sonar contacts that are of some interest as they stand out from their surroundings but have low probability of being significant to the search. The underwater search so far has identified more than 400 seabed features that have been classified as category 3.

Classification 2 sonar contacts are of more interest but are still unlikely to be significant to the search. There have been more than 20 features that have been classified as category 2. These objects may or may not be man-made, but expert analysis of the sonar imagery ranks them as having a low probability of being an aircraft debris field.

Classification 1 sonar contacts are of high interest and warrant immediate further investigation. When a Classification 1 sonar contact is reported, the search vessels are instructed to gather higher resolution/ high frequency sonar data flying the AUV or towfish closer to the seafloor, (an altitude of between 35 meters and 50 meters). If the high-resolution sonar data looks promising, a photo mission is then run at very low altitude (between 8 meters and 10 meters) to identify positively any objects on the seafloor. Generally, these contacts are rare, as only two have been marked to date. One was determined to be a rock field, and the second was found to be an old wooden shipwreck.

(ATSB image: Mosaic of shipwreck debris field with photo of anchor taken by Echo Surveyor VII classified as Category 1)

FMI: www.atsb.gov.au