Malaysia Airlines (Kuala Lumpur) missing flight MH 370 of March 8 with 239 passengers and crew members on board remains missing. The next phase of the search is likely to move the search area several hundred miles to the south in the southern Indian Ocean.

The Associated Press first reported this change, citing Martin Dolan, chief commissioner of the Australian Transport Safety Bureau (ATSB).

The Bluefin-21 will be redeployed in this new area. The exact new area is still being determined.

On May 26 Martin Dolan issued this statement about the search:

By Martin Dolan, Chief Commissioner

It’s now been more than 11 weeks since Malaysia Airlines flight MH 370 disappeared from air traffic control radar after taking off from Kuala Lumpur on a scheduled passenger service to Beijing.

Despite one of the most intensive and coordinated air and sea search efforts ever undertaken, there has not yet been any sign of the missing aircraft.

The complexities surrounding the search cannot be understated. It involves vast areas of the Indian Ocean with only limited known data and aircraft flight information. While it is impossible to determine with certainty where the aircraft may have entered the water, all the available data indicates a highly probable search area close to a long but narrow arc of the southern Indian Ocean.

It is now highly unlikely that surface debris from the aircraft will be spotted. This means that the most effective way to continue the search is to look for MH370 under the water.

The search will be a major undertaking.

The complexities and challenges involved are immense, but not impossible.

Following an announcement by the Prime Minister of Australia in late April, and at the request of the Malaysian government, the ATSB is planning an intensified underwater search of a 60,000 square kilometre area—roughly the size of Tasmania.

As part of its search operations, the ATSB’s initial work involves:

reviewing existing information, from an expert satellite working group, to refine a search zone of up to 60,000 square kilometres in the southern Indian Ocean
conducting a bathymetric survey to map the search area
consulting with domestic and international authorities—including various oceanographic institutions and private companies—to prepare the plan and specialist services required for the next search phase.
The bathymetric survey— or mapping of the ocean floor— has already commenced, with the Chinese survey ship Zhu Kezhen conducting a survey of the areas provided by the ATSB. Zhu Kezhen will shortly be joined by a contracted commercial survey vessel in June. Taking around three months to complete, the bathymetric survey will give us crucial knowledge of the seafloor terrain needed to begin the underwater search.

The intensified underwater search will aim to locate the aircraft and any evidence (such as aircraft debris and flight recorders) to assist with the Malaysian investigation. The equipment used for the search will likely include a towed sonar, an Autonomous Underwater Vehicle with mounted sonar, and optical imaging equipment. We expect the search to begin in several months and take up to 12 months to complete.

The search will be a major undertaking. The complexities and challenges involved are immense, but not impossible. The best minds from around the world have been reviewing, refining and localising the most likely area where the aircraft entered the water, which is why we remain confident of finding the aircraft.

On May 26 the ATSB issued this detailed statement on the considerations of where it will search for MH 370:

Background

At the request of the Malaysian Government, Australia is leading the search for missing Malaysia Airlines Flight MH 370 in the Indian Ocean. The search is a complex operation that involves vast areas with only limited data and aircraft flight information available.

Over-water searches

Over-water aircraft accident locations are usually found by conducting a broad-area aerial search. The search area is generally determined by a combination of:
Position information from ground-based radar systems (maximum range is generally 250 NM)
Position information automatically transmitted from the aircraft at regular intervals

Position reports from the crew

Re-tracing the planned flight route

Eye-witness reports (possibly located on the shore, on other aircraft or on ships)

Uncertainty in the position of an accident location increases with time from the aircraft’s last known position (fix) so the search area will expand accordingly as the position data becomes ‘stale’.

Once floating wreckage is observed, reverse-drift techniques can be used to help determine the aircraft impact location. Only a small-area underwater search is then required to locate the wreckage and map the wreckage field. This underwater search can be aided by the underwater locator beacons fitted to flight recorders. As the beacons have a limited duration of nominally 30 days and to minimise the inaccuracies of the reverse-drift calculations, it is important that an aerial search is commenced as soon as possible and the floating debris is found quickly.

In the case of MH 370:

The aircraft departed Kuala Lumpur at 1641 UTC
The final automatically transmitted position from the aircraft occurred at 17:07 UTC
No radio communications were received from the crew after 17:19 UTC
The final ATC (secondary) radar fix occurred at 17:22 UTC
At 17:25 UTC the aircraft deviated from the planned flight route
The final primary radar fix occurred at 18:22 UTC
The satellite communications log indicated the aircraft continued to fly for another 6 hours
No confirmed eye-witness reports were received
The search in the Australian search and rescue zone commenced on 18 March (10 days after the aircraft went missing)

As a result, the search area for MH 370 has remained very large. A useful comparison is the search for Air France Flight 447 (AF 477), which crashed in the Atlantic Ocean on 1 June 2009. The AF447 aircraft was programmed to send its position automatically every 10 minutes, there were a number of fault messages transmitted via satellite during the last few minutes of flight and it was following the planned flight route. The search for the aircraft began on 1 June and the first surface wreckage was discovered on 6 June, 5 days after the accident. Given the relative accuracy of the aircraft’s last known position, a circular search area of 40 NM was defined (17,240 km²). After a search effort involving five separate phases, the aircraft wreckage was located on the ocean floor almost two years later.

As none of the traditional sources of data could be used to locate the aircraft wreckage from MH 370, it has been necessary to use novel sources of data and analysis techniques. This has led to a larger than typical search area; and there have been changes to its location as validation and calibration checks have been performed and the analysis is refined.

Determining the search area for MH 370

The flight path of MH 370 has three distinct sections; one under secondary radar in which the aircraft transponder was operational and ACARS messages were being transmitted, a primary radar section during which the aircraft was being tracked solely by air defence radar systems and the final stage for which the only information available was the satellite communications log data.

ACARS and radar data

The final ACARS transmission was at 17:07 UTC and provided location reports from the initial stage of the flight as well as a recording of the aircraft fuel remaining. The final secondary radar point was at approximately 17:22 UTC. The final primary radar point was at 18:22 UTC. Figure 1 shows the first and second sections of the flight.

Figure 1: MH 370 Flight path derived from Primary and Secondary radar data:

Source: NTSB/Google

Satellite communications (SATCOM) data

Following the loss of primary radar, the only available information was from satellite signalling messages, also referred to as ‘handshakes’, between the ground station, the satellite and the aircraft’s satellite communication system.

For each transmission to the aircraft, the ground station recorded the burst timing offset (BTO) and the burst frequency offset (BFO).

Figure 2: Satellite communications schematic:

Source: Inmarsat

Burst Timing Offset (BTO)

The BTO is a measure of the time taken for a transmission round trip (ground station to satellite to aircraft and back) and allows a calculation of the distance between the satellite and the aircraft. Based on this measure, a possible location ring can be mapped on the surface of the earth (Figure 3). An analysis of SATCOM system parameters showed that the accuracy of the rings was ± 10 km. This analysis was validated using recorded BTO values from the initial stage of the flight when the aircraft’s position was known.

Figure 3: Satellite ring derivation:

Source: Inmarsat

There were 7 handshakes between the ground station and the aircraft after the loss of primary radar data. The location rings calculated from the recorded BTO values are shown in figure 4.

Figure 4: MH 370 timing (UTC) with corresponding rings arrowed:

Source: Inmarsat/Boeing /Google

The information from the BTO places the aircraft somewhere on each ring at the corresponding time. By taking the maximum speed of the aircraft into account, the rings can be reduced in length to arcs – there are some areas of the rings it simply could not have reached.

Burst Frequency Offset (BFO)

The BFO is the measure of the difference between the expected frequency of the transmission and the frequency received at the ground station. This difference is attributed to various sources including the Doppler Effect from the motion of the satellite and the aircraft, as well as some processing effects. Once the known components that contribute to the BFO are resolved, the remainder can be used to estimate the speed and direction of the aircraft. There are a large number of speeds and headings that can be consistent with a BFO recording. These are limited, however, by the operational constraints of the aircraft.

Candidate paths of different speeds were created which met the BTO ring location/time constraints and the predicted BFO values of these paths have been compared with the recorded values. The better the match, the higher the probability that the path was close to that of MH370.
Final handshake message at 00:19 (7th arc)

The 00:19 signalling message (7th arc) was a logon request from the aircraft. This is consistent with the satellite communication equipment on the aircraft powering up following a power interruption. The interruption in electrical supply may have been caused by fuel exhaustion.

Note on the satellite communication

The satellite’s normal function is essentially communication and it was never initially intended to have the capability to track an aircraft. Following the Air France 447 accident, Inmarsat engineers began recording the BTO in order to provide another potential means of geo-locating aircraft in the event of a similar accident.

Aircraft Performance Calculations

Estimates of fuel consumption were calculated from the time of the last recorded fuel quantity, using a range of flight paths and speeds. The results of these calculations were consistent with fuel exhaustion occurring close to the 7th arc.

Validation

Several teams independently provided both satellite communications and performance analysis as part of the validation process. The location of 9M-MRO on previous flights as well as the locations of other aircraft in the air at the same time were all used to validate the techniques.

Other information

Surface search

An international air and maritime force conducted a surface search of drifted regions along the 7th arc from 18 March to 28 April 2014. A drifted region is created by modelling the movement of an area of water over the time period when the surface search is conducted. During this time, no debris was identified to be likely from MH 370.

Underwater search

Acoustic detections possibly related to underwater locator beacons were made by two vessels in the refined probability area from 5 – 8 April 2014. To further investigate these signals, a search of the ocean floor around the detections was performed by a number of vessels. To date no further sign of MH370 has been detected.

Hydrophones

Low frequency hydroacoustic signals present in the Indian Ocean are being examined to determine whether they can provide any information to help define the search area. These signals are recorded by hydrophones as part of the United Nations Comprehensive Nuclear-Test-Ban-Treaty Organisation (CTBTO) or the Integrated Marine Observing System (IMOS).

Use of waypoints

Comparison of possible flight paths with tracks using waypoints is also under consideration.

Air Routes

There is only one published north-south air route in the south-eastern Indian Ocean. Air route M641 connects Cocos Island to Perth and has four waypoints. The air route crosses the area where the four acoustic signals were detected.

Shape of the search area

At the time MH 370 reached the 7th arc, the aircraft is considered to have been descending. A study completed after the Air France 447 accident concluded that the majority of aircraft in loss of control accidents were found within 20 nautical miles (32 km) of their last known position. This provides a reasonable limitation for the size of the search area across the arc.

Additionally the Australian government through the ATSB on May 26 explained how it is searching for missing flight MH 370:

Background

The Australian Transport Safety Bureau (ATSB) is leading the underwater search for missing Malaysia Airlines flight MH 370. All the available data indicates the aircraft entered the sea close to a long but narrow arc of the southern Indian Ocean.

The search is a complex operation that will involve a range of vessels, equipment and expertise to cover 60,000 square kilometres of ocean floor.

Bathymetric survey

During the first stage of the search, the ATSB is tasking a Chinese PLA-Navy ship to undertake a bathymetric survey of the 60,000 square kilometre search area. A contracted commercial vessel with join the survey in June. The bathymetric survey will provide a map of the underwater search zone, charting the contours, depths and hardness of the ocean floor.

While the ocean depth of the search zone is understood to be between 1000 m and 6000 m, we currently have very limited knowledge of the sea floor terrain facing the underwater search operation. The information we receive from the bathymetric survey will give us crucial data to plan and conduct the intensified underwater search.

How the survey’s done

The operation will involve a ship surveying the ocean floor using multi beam sonar, which is capable of collecting high quality data to water depths of up to 6,000 m.

Multibeam sonar is a common offshore surveying tool that uses multiple sound signals to detect the seafloor. Due to its multiple beams it is able to map a swath of the seabed under the ship, in contrast to a single beam sonar which only maps a point below the ship. Different frequencies are used to map different water depths, with higher frequencies (>100kHz) used for shallow water and low frequencies (<30 kHz) for deep water.

Generally, the multibeam sonar transducer is mounted rigidly to the hull of the survey vessel and its position can be calculated very accurately. Other parts of the multibeam system include auxiliary sensors such as motion-sensing systems and Global Positioning Systems (GPS) to ensure accurate positioning, motion sensing and sound speed measurement system.

A modern multibeam sonar transducer typically uses the Mills Cross telescope array. The sound is transmitted from transducers that are perpendicular to the survey track. Consequently, the sound pulses forms a transmit swath that is wide across-track and narrow along-track. The returning sound pulses, which are mainly recording the impedance contrast and seafloor topography, are received by the receivers which are mounted parallel to the survey track. These return beams are narrow across-track.

Unlike the sidescan sonar which commonly produces only acoustic backscatter data (i.e. hardness), the multibeam sonar generates both water depth and seafloor hardness data concurrently.1
How many vessels will be involved in the survey

The Chinese PLA-Navy ship Zhu Kezhen (872) is already in the search area conducting a bathymetric survey of an area provided by the ATSB. A contracted survey vessel will arrive in the search area in early June.

How long it will take?

It is expected that the bathymetric survey will take around three months to complete, but this will depend on a number of factors, such as weather conditions, during the survey operations.
The underwater search will begin when we have enough data from the bathymetric survey to start searching. This means that the underwater search will begin while the survey is still being completed.

On June 4 the ATSB issued a request for specialist help in determining the new search area (all proposals are due by June 30):

The ATSB has released a request for tender to acquire the services of a specialist company capable of conducting a deep-water search under ATSB direction for missing Malaysia Airlines Flight MH 370.
Engaged as a prime contractor, the company will provide the expertise, equipment and vessel(s) necessary to undertake an intensified underwater search for the missing Boeing 777 aircraft in the defined zone in the southern Indian Ocean.

While the precise search zone is currently being established by an international search strategy working group, it is expected that the successful tenderer will search an area up to 60,000 square kilometres based on the ‘seventh handshake’ arc where the aircraft last communicated with the Inmarsat satellite. Definition of the search zone will be finalised within two to three weeks.

The successful tenderer will localise, positively identify and map the debris field of MH 370 using specialist equipment such as towed and autonomous underwater vehicles with mounted sonar and/or optical imaging systems.

The intensified search will begin in August 2014 and is expected to take up to 12 months, depending on weather conditions. The successful tenderer will use the data from a bathymetric survey (already underway) to navigate the search zone, which has water depth between 1000 and 6000 metres.

The search vessel(s) used by the prime contractor may also be coordinated with other vessels also undertaking search activities in the search zone on behalf of other countries.

A copy of the request for tender is available on the AusTender website at http://www.tenders.gov.au. Request for tender submissions are due by 5.30pm AEST on June 30, 2014.

At the request of the Malaysian Government, the ATSB is leading the search for missing Malaysia Airlines Flight MH370.

Search for MH 370 Facts and Statistics: