Recently, RESON South Africa (PTY) Ltd was contracted to locate the submerged wreck of a Lesotho Defense Force Eurocopter BO105 helicopter. The helicopter crashed into the Katse Dam during a low-level filming flight on 22 nd May 2003, killing two of the five occupants.
A team of South African police divers were mobilized immediately after the crash to recover the bodies. When it was realized that the wreck was beyond their reach, a diving team from Durban was contracted. After eight days of fruitless video and echosounder searches in water depths of 90m to 170m the team leader finally convinced the authorities to agree on sub-contracting with RESON to locate the wreck.
Upon signing the contract, the Cape Town-based RESON field team packed their gear and flew to Durban for an 8-hour overnight road trip into the small mountainous country of Lesotho. The SeaBat 8101-ER (Extended range) Multibeam echosounder was mobilized and calibrated on a small 4.9m pleasure boat. Approximately 36 hours after authorities contracted RESON, the search began and within 45 minutes a likely sonar target was seen at 94m depth and 100m outside the original search area. A comprehensive survey of the valley uncovered no other unusual targets and efforts were concentrated on the most promising contact. The next morning the dive team lowered a video camera down to the site and identified it as the severely damaged wreckage of the helicopter containing one of the missing bodies. The cockpit was lifted later the same day and the remaining body was successfully recovered.
After the wreckage was initially located, additional survey work was undertaken at other various dam locations. A total of seven different surveys were completed within two operational days.
The SeaBat 8101 Multibeam Echosounder measures discrete depths, enabling complex underwater features to be mapped with precision. Dense coverage is achieved utilizing up to 4,000 soundings per second for a swath that up to 480 meters in width, even as the survey vessel travels at speeds in excess of 18 knots. With the optional Extended range package, depths can reach to 400m.