Malaysia Airlines flight MH370’s black-box pingers. Technical acoustic information that may be useful to reporters and researchers

The mystery of the missing Malaysia Airline flight MH370 is closer to being solved as authorities have revealed that they have tracked the final unexplained signal emitted by the jet, to the same point in the Indian Ocean, where the jet was believed to have crashed. Time will tell whether this is a definitive lead […]
The mystery of the missing Malaysia Airline flight MH370 is closer to being solved as authorities have revealed that they have tracked the final unexplained signal emitted by the jet, to the same point in the Indian Ocean, where the jet was believed to have crashed. Time will tell whether this is a definitive lead or a false alarm. We all hope it is the beginning to a successful answer. Calling the latest development a promising lead, retired Air Chief Marshal Angus Houston, who is leading the search, said that an Australian navy ship had detected two sets of pulse signals that sounded just like an emergency locator beacon. While the first set was heard on Saturday and lasted for two hours and 20 minutes, the Ocean Shield ship then lost contact with the “pings” but turned around and later heard further signals for 13 minutes, the Sydney Morning Herald reported. However, the ship lost contact again and has been trying to relocate the signals. Houston said that in the search so far it is probably the best information that the team has had, adding that the search team is encouraged that it is very close to where it needs to be. He added that he would want more confirmation before he could say ‘this is it’. Here is a list of the equipment that is being employed by the searchers. If you find this information useful, please mention ATICourses.if you use the materials that we have gathered. ATIcourses has a strong set of courses in underwater acoustics and oceanography that provide additional information. Some of our instructors are willing to provide more in-depth information to reporters who are actively covering the Malaysian flight MH370 investigation to provide accurate, in-depth information. Contact us at ati@ATIcourses.com More info
1. Beacon Black Box Locator Acoustic 37.5 KHz Pingers An underwater locator beacon (ULB) or underwater acoustic beacon, also known informally as a pinger, is a device fitted to aviation flight recorders such as the cockpit voice recorder (CVR) and flight data recorder (FDR). ULBs are also sometimes required to be attached directly to an aircraft fuselage. ULBs are triggered by water immersion; most emit an ultrasonic 10ms pulse once per second at 37.5 kHz ± 1kHz. Maximum detection range A 37.5 kHz (160.5 dB re 1 μPa) pinger can be detectable 1–2 kilometres (0.62–1.24 mi) from the surface in normal conditions and 4–5 kilometres (2.5–3.1 mi) in good conditions. A 37.5 kHz (180 dB re 1 μPa) transponder pinger can be detected 4–5 kilometres (2.5–3.1 mi) in normal conditions and 6–7 kilometres (3.7–4.3 mi) in good conditions. SPECIFICATION: • Operating Frequency: 37.5 kHz  ± 1 kHz (Doppler can shift the measured frequency) • Operating Depth: Surface to 20,000 feet (6100 m or 3.33 nmi) • Pulse Length: Not less than 9 milliseconds (10 millisecond nominal) • Pulse Repetition Rate: Not less than 0.9 pulse per second (1 pulse per second nominal) • Acoustic Output, Initial: 1060 dynes/cm2rms pressure at 1 meter (160.5 dB re 1 UPa/ meter) • Acoustic Output, After 30 days: 700 dynes/cm2rms pressure at 1 meter (157.0 dB re 1 UPa/meter or about 70 % of the nominal range as it degrades) • Radiation Pattern: Rated output over 80 percent of sphere, near omni-directional • Size: 1.3″ diameter x 4″ long (DK100/DK120) • 1.3″ diameter x 2.97″ long (DK130/DK140) • Weight: Less than 7 oz (including battery) (DK100/DK120) • Less than 4.9 oz (including battery)(DK130/DK140) • Power Source: Lithium Battery • Expected range: about 2 nmi slant range radius from source for 37.5 KHz Expected Transmission Loss at 37.5 Khz assuming absorption of 4.2 dB per KIM plus spreading loss of 20 log R or 60 dB + 10 log r for R> 1000 meters 37.5 KHz ———————— 0.31 mi .62 mi 1.25 mi 3.25 mi 6.2 mi 10 mi 100 mi mi Range in KM ———————— 0.5 1 2 5 10 16 160 KM TL =20 log Rkm*1000+ alpha*Rkm 56.1 64.2 74.4 95.0 122.0 151.3 776.1 TL (dB) TL =20 log Rkm*1000+ alpha*Rkm for RKM <1 Km 56.1 64.2 71.4 88.0 112.0 139.2 754.0 TL (dB) TL =60 +10*log Rkm+ alpha*Rkm for RKM.>1 2. Autonomous Underwater Vehicle – Bluefin-21 Search Vehicle   The Bluefin-21 is a highly modular autonomous underwater vehicle able to carry multiple sensors and payloads at once. It boasts a high energy capacity that enables extended operations even at the greatest depths. The Bluefin-21 has immense capability but is also flexible enough to operate from various ships of opportunity worldwide.
Depth Rating 14,763 ft (4,500 m)
Endurance 25 hours @ 3 knots with standard payload
EdgeTech 2200-M 120/410 kHz side scan sonar for search Reson 7125 400 kHz multibeam echosounder for site mapping   http://www.bluefinrobotics.com/products/bluefin-21/   3 Side Scan Sonar Option – EdgeTech 2200   The Full Spectrum chirp side scan sonar is a calibrated wide band digital FM sonar that provides quantitative and qualitative, high resolution, low-noise side scan imagery. It simultaneously transmits linearly swept FM pulses and the user may select the combination of these frequencies dual simultaneous as follows:   120/410 kHz, (most likely for Malaysia Airline Flight 370 Search) 75/410 kHz, 75/120 kHz or 300/600 kHz.   A Digital Signal Processor (DSP) in the Full Spectrum (FSDW) electronics on the AUV or ROV holds the two chirp waveforms to be transmitted.   ATI thinks the side scan frequency is likely to be 120/410 KHz which will give ranges of 250 m to 500m at 120 KHz and 130M to 200m at 400 Khz.   That will imply short detection ranges even for the 120 KHz sonar, say 250 – 500 m per side. The 410 KHz is then used at shorter range (130 – 200 m) to get a higher resolution image. The search pattern must overlap to leave no coverage holes, so the offsets in range between passes may be at most 90 percent of the assured range.   Expected Operational Ranges for the EdgeTech 2200- side scan sonar, depending on Water temperature and salinity. The absorption factor is estimated based on a model from Francois and Garrison, JASA 1982, and a depth of 50m. Absorption decrease slightly as the side scan is towed deeper. The range is to each side and the search rate is likely to be limited to 2.5 or 3.0 knots to keep the autonomous underwater vehicle (AUV) near the bottom on a long cable scope. Quoted from http://www.edgetech.com/docs/app_note_range.pdf  
  • Freq : 120Khz, Range: 250 to 500m
  • Freq: 410kHz, Range: 130 to > 200m
 
  • Freq : 75kHz, Range: 700 to 800m. 1000m is possible at extreme depths and with special pulses
  • Freq : 270kHz, Range : 150 to 300m
  • Freq : 540kHz, Range: 100 to 150m
  • Freq : 850kHz, Range: 50 to 75m
  http://www.edgetech.com/docs/2200-m_brochure_073107.pdf   4. SeaBat 7125 – Reson 7125 400 kHz multibeam echosounder   The fundamental acoustics with 400 kHz for high resolution, high density surveying which exceeds the most stringent of specifications, and 200kHz for greater range performance. The SeaBat 7125 can be installed on any platform from survey vessels to ROVs and AUVs down to 6000m water depth.   The 400 kHz multibeam echosounder is a multibeam mapping sonar. ATI would expect that it will need to be towed about 150 – 400 m off the bottom to get good signal to noise. It is likely used to map the wreckage after it has been found using the side scan sonar.   Then ATI expects some short range video to confirm and map the wreckage.   http://www.teledyne-reson.com/products/seabat-feature-packs/fp3-frdh/  
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New NOAA ship helps gather data

NOAA’s newest ship, the “Hassler”, has some of the most sophisticated equipment available to collect that data. The scientific research being done aboard the Hassler will have some very practical applications. The “fish” being deployed into the water is actually a side-scanning sonar device that enables the team of scientists and NOAA officers to make […]
NOAA’s newest ship, the “Hassler”, has some of the most sophisticated equipment available to collect that data. The scientific research being done aboard the Hassler will have some very practical applications. The “fish” being deployed into the water is actually a side-scanning sonar device that enables the team of scientists and NOAA officers to make a detailed survey of the sea floor. “The side-scan is very important because it gives us a very high resolution picture of the sea-bed.  It allows us to clearly see obstructions and wrecks,” Lt. Cmdr. Ben Evans said. And in shallow water it is capable of scanning a very wide area of the sea-floor. This data, along with depth readings from multi-beam sonar devices, is used by NOAA to produce maps and charts to guide merchant vessels transiting the port of Hampton Roads. “The port is a huge economic engine for the area, so we want to make sure those container ships can come in fully loaded and know exactly how much water they have underneath of their hulls,” Andrew Larkin with NOAA said. Keeping the maps and charts up to date is a constant process because like the crew of the Hassler, the sea floor is constantly on the move. “The out-flow from rivers or storms can move the sand and mud in the area to the approaches of the Chesapeake Bay,” Larkin added. “Occasionally we’ll see things like wrecks, a ship could go down or a container could fall off a ship and block the channel.” The technology aboard the Hassler enables scientists to find and record changes to the sea floor in a fraction of the time this process used to require. “What used to take mariners with a sounding line, it would take em two minutes to do one sounding.  Now we’re doing 1,028 about 20-times a second,” David Moehl said. In fact, the Hassler and her crew are gathering more data than was ever possible.


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More on Sonar Search for AF 447

Information about sonar and side-scan sonar is presented in the short course Sonar Signal Processing Jul 14-16, 2009 Beltsville, MD The sonar search for the Air France Flight 447 flight and voice recorder continues with out any reported success. The underwater sonar has an acoustic frequency of 37.5kHz, transmitting initially with 1,060 dynes/cm2, and has […]
Information about sonar and side-scan sonar is presented in the short course Sonar Signal Processing Jul 14-16, 2009 Beltsville, MD The sonar search for the Air France Flight 447 flight and voice recorder continues with out any reported success. The underwater sonar has an acoustic frequency of 37.5kHz, transmitting initially with 1,060 dynes/cm2, and has a battery life of at least 30 days. Maximum detection range is 2–3km. The water depth is about 3500 m, so a towed sonar is required to get deep enough to have a chance to hear the pinger. There is useful information at http://www.hydro-international.com/issues/articles/id1098-Air_France_Flight_AF.html French authorities have dispatched five ships: IFREMER research vesselPourquoi Pas; two tugboats, Fairmount Glacier and Fairmount Expedition; naval frigateVentôse; and nuclear submarine Emeraude.Ventôse has assisted with recovery of floating debris and bodies. Emeraude will conduct an initial search listening for the black-box pinger. Once this has been located, Pourquoi Pas shall carry out a side-scan sonar survey and there are plans to then deploy a mini-submarine to carry out a detailed photographic survey leading to recovery operations. The accident location is 1,000km from the Brazilian coastline and the sea floor is extremely rugged (making side-scan sonar operations troublesome) and around 3,500 metres deep (making it difficult to detect the black-box pinger with a maximum range of 2–3km). Both operations will require a submersible or deep-tow capability for sensor deployments. Subsequent recovery of substantial aircraft parts will be an almost-impossible task and operations will probably be limited to flight recorder recovery and a detailed sonar and photographic survey. http://www.hydro-international.com/issues/articles/id1098-Air_France_Flight_AF.html