Reports/The Operational Search for MH370/The surface search

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The surface search

The surface search for MH370 lasted from 8 March 2014 until 28 April 2014 and was initially a search and rescue operation. The intent was to locate the aircraft as quickly as possible in order to rescue any potential survivors. The areas searched were based on information from a range of sources and progressively refined analysis in relation to the aircraft’s most likely flight path.

Early in the surface search the Malaysian Government convened the Joint Investigation Team (JIT) comprising experts from the People’s Republic of China, France, Malaysia, United Kingdom, United States and Malaysian Government officials. Soon after, a satellite communications working group (SATCOM WG) was also formed and included experts from Inmarsat and Thales. These groups of experts worked together to provide advice to the Malaysian Government on the surface search areas.

By the end of the surface search an area of several million square kilometres had been searched by aircraft and surface vessels in the South China Sea, Andaman Sea, Bay of Bengal and Indian Ocean, however no items of debris from MH370 were recovered or positively identified.

The following section sets out the chronology of the surface search, the search assets used, the areas of focus at different times and the information or analysis used to define each area.

Malaysian led surface search

Search operations commenced on the day that MH370 went missing, 8 March 2014, and were led by Malaysian and Indonesian authorities in areas around Malaysia until 23 March 2014.

East of the Malay Peninsula

Initially search and rescue (SAR) operations were coordinated by Kuala Lumpur Aeronautical Rescue Coordination Centre (KL ARCC) and were conducted to the east of the Malay Peninsula in the South China Sea between 8 and 15 March 2014 (Table 6). This area was based largely on the last contact with the aircraft and where the SSR transponders ceased to operate.

 

Table 6: Initial surface search SAR operations east of Malaysia

Dates: 8–15 March 2014
Event: Malaysia (KL ARCC) initial surface search area.
Search area location: East of Malay Peninsula (South China Sea).
Search activity: Aerial and surface search.
Guiding advice: Malaysia Air Defense.
Data used in planning
search area refinement:
Malaysia Air Defense secondary surveillance radar data. Track BD764 7 March 2014 1642:07–1728:37 UTC recorded at 10 second intervals.
Search equipment: 28 aircraft from the People’s Republic of China (2), Japan (5), Malaysia (10),Singapore (4), Thailand (1), United States (2) and Vietnam (4).
34 vessels from the People’s Republic of China (7), Malaysia (19), Singapore (3), United States (3) and Vietnam (2).
Search area: 573,000 km2

Source: DCA Malaysia

 

The areas covered during the search operations in the South China Sea are shown in Figure 6.


Figure 6: Surface search east of the Malay Peninsula 8 to 15 March 2014

Figure 6: Surface search east of the Malay Peninsula

Source: Google Earth, annotated by DCA Malaysia


 

West of the Malay Peninsula

From 8 to 15 March 2014, the same time as the surface search in the South China Sea east of the Malay Peninsula, SAR operations coordinated by the Royal Malaysia Air Force, were conducted to the west of the Malay Peninsula (Table 7).

 

Table 7: Initial surface search SAR operations west of Malaysia

Dates: 8–15 March 2014
Event: Malaysia (Royal Malaysia Air Force) initial surface search area.
Search area location: West of Malay Peninsula
(Strait of Malacca, Andaman Sea and the Bay of Bengal) and West of Sumatra.
Search activity: Aerial and surface search.
Guiding advice: Malaysia Air Defense.
Data used in planning search area refinement: Malaysia Air Defense primary radar data. Track BE144 7 March 2014 1729:09–1802:59 UTC recorded at 10 second intervals.
Search equipment: 36 aircraft and 35 vessels from Australia, Bangladesh, the People’s Republic of China, India, Indonesia, Malaysia, New Zealand, Republic of Korea, Singapore, Thailand, United Arab Emirates and the United States.
Search area: 4,560,000 km2

These search operations were undertaken in the Strait of Malacca, Andaman Sea, Bay of Bengal and west of Sumatra from 8 to 15 March 2014 (Figure 7, areas subject to search operations shown in white and blue). This area was searched based on the primary radar data which indicated an unidentified aircraft had flown up the Strait of Malacca, thought to be MH370.


Figure 7: Surface search areas west of the Malay Peninsula 8 to 15 March 2014

Figure 7: Surface search areas west of the Malay Peninsula 8 to 15 March 2014

Source: Google Earth, annotated by DCA Malaysia


 

Northern and southern corridors announced

In the first week of the surface search an analysis of Inmarsat satellite communication (SATCOM) data for MH370 indicated that the aircraft had flown for a further six hours after the final radar capture at the northern tip of Sumatra. The initial satellite data analysis indicated that the aircraft had flown along one of two corridors; one to the north in the direction of Kazakhstan or one to the south to the Indian Ocean. This new information led to the suspension of SAR operations to the east and west of the Malay Peninsula on 15 March 2014.


Figure 8: Southern corridor

Figure 8: Southern corridor

Source: Malaysia, ICAO Third Meeting of the Asia/Pacific Regional Search and Rescue Task Force (APSAR/TF/3) Working Paper 06, Maldives, 25 – 29 January 2015


An aerial search coordinated by KL ARCC and Badan SAR Nasional (BASARNAS), the Republic of Indonesia National Search and Rescue Agency, was conducted within the southern corridor indicated by the SATCOM data from 18 to 23 March 2014 (Table 8).

 

Table 8: SAR operations southern corridor

Dates: 18–23 March 2014
Event: Malaysia (KL ARCC) and Indonesia (BASARNAS) refined surface search area.
Search area location: Within S1-S3 (Malaysian designation – refer Figure 8 and Figure 9) of the southern corridor.
Search activity: Aerial search
Guiding advice: Timing information obtained from satellite data and aircraft performance data was used to identify a northern and southern corridor along which MH370 may have flown with probable final location close to the 6th arc.
Data used in planning search area refinement: MH370 Inmarsat satellite data unit logs and advice from SATCOM WG and data compiled by the JIT.
Search equipment: Eight aircraft from India, Japan, Malaysia, Republic of Korea, United Arab Emirates and the United States.
Search area: 1,630,000 km2

Source: DCA Malaysia

By 24 March 2014, further analysis of the SATCOM data established that the data was only consistent with flight paths along the southern corridor ending in the southern Indian Ocean.


Figure 9: KL ARCC and BASARNAS S1, S2 and S3 search areas (18-23 March 2014)

Figure 9: KL ARCC and BASARNAS S1, S2 and S3 search areas (18-23 March 2014)

Source: Malaysia, ICAO Third Meeting of the Asia/Pacific Regional Search and Rescue Task Force (APSAR/TF/3) Working Paper 06, Maldives, 25 – 29 January 2015


 

Australian led surface search

On 17 March 2014, with the southern corridor extending into the Indian Ocean and the Australian search and rescue region, Australia assumed responsibility for coordinating the SAR operation for the aircraft, at Malaysia’s request. The Australian Maritime Safety Authority (AMSA) was responsible for coordinating this activity using aircraft and surface vessels operating from Western Australia until 28 April 2014. AMSA continued to take advice on the areas to search from the JIT and SATCOM WG based on the progressive analysis of the Inmarsat satellite communication logs and other aircraft performance analysis.

The surface search was focused on the identification and recovery of any debris from the aircraft floating on the sea surface. When AMSA took over the coordination of the surface search nine days had passed since the aircraft went missing. It was therefore necessary to define the areas to be searched by aircraft and surface vessels based on the analysis indicating where the aircraft may have ended the flight and the calculated drift of a range of possible types of floating debris in the days after 8 March 2014.

A drift modelling working group was set up by AMSA, comprising a number of organisations including: CSIRO, Asia-Pacific Applied Science Associates, the United States Coastguard, the Bureau of Meteorology and Global Environmental Modelling and Monitoring Systems to ensure that best practice drift modelling was put in place for the surface search. The drift modelling was also informed by the deployment of self-locating datum marker buoys (SLDMB) from aircraft and vessels throughout the surface search. A SLDMB is a drifting surface buoy fitted with a GPS that is used to measure surface ocean currents. The marker buoy has an expected lifetime of over 20 days once deployed in the ocean. Similarly, real-time wind and wave data from the search area was used to continuously update the drift models.

 

Initial southern Indian Ocean surface search area

The initial Australian led MH370 surface search area was determined to be a 600,000 km² area of the southern Indian Ocean approximately 2,500 km from Perth, Western Australia (Table 9). The area was determined by assuming the aircraft had made a southern turn shortly after the last radar capture at the northern tip of Sumatra and flew until fuel exhaustion.

 

Table 9: Initial southern Indian Ocean surface search SAR operations

Dates: 18–19 March 2014
Event: Australia (AMSA) initial surface search area.
Search area location: S1/S2 16
Search activity: Aerial visual and radar search.
Guiding advice: MH370 Inmarsat satellite data unit logs and advice from SATCOM WG to AMSA. Data compiled by the JIT in conjunction with NTSB.
Data used in planning search area refinement: The actual satellite location.

Turn south occurred at the northern tip of Sumatra.
Performance predictions based on speed and range only with no wind consideration.
Only positional information from Malaysian primary radar data.
Length of arc to the south constrained by maximum aircraft groundspeed
Lateral navigation set to ‘track’ mode.
Two speeds provided ‘best fit` with longest and straightest tracks reaching the 6th arc.

Assumed speed and altitude to last radar point were final ACARS values.
Search equipment: Aircraft from Australia, New Zealand and the United States.
Two merchant vessels responded to urgency broadcast and transited to and through search area.
Search area: Refer to Table 10.

Source: ATSB

Search areas in the southern Indian Ocean designated S1, S2 and S3 (Figure 10) were defined from estimates of the aircraft’s performance and endurance. In particular, two hypothetical speeds (469 and 475 knots) that resulted in the longest, straightest tracks that reached the 6 th arc derived from the SATCOM data. These tracks intersected the arc in areas S1 and S2, so they were used to define the initial search area.


Figure 10: Possible southern final positions S1–S3 based on MH370 maximum range

Figure 10: Possible southern final positions S1–S3 based on MH370 maximum range

Source: ATSB, using JIT data


On 18 and 19 March 2014, areas S1 and S2 were corrected for drift which provided the surface search areas for those days (Figure 11 and Figure 12).


Figure 11: Area searched 18 March 2014

Figure 11: Area searched 18 March 2014

Source: AMSA


Figure 12: Area searched 19 March 2014

Figure 12: Area searched 19 March 2014

Source: AMSA


Table 10: Search area information 18 to 19 March 2014 (Not included here.)

 

Satellite imagery debris detections

While the initial surface search activity in the southern Indian Ocean was based on the analysis of the aircraft’s possible flight paths and maximum endurance, other information was being actively sought including satellite imagery. AMSA, working with the Australian Geospatial-Intelligence Organisation, had requested governments with low earth orbiting satellites to gather imagery in and around the MH370 search area (see section on Satellite imagery analysis). Imagery was analysed for possible aircraft debris and the information was passed to Australian Geospatial-Intelligence Organisation and AMSA.

From 16 to 27 March 2014, a number of potential debris sightings were made in satellite imagery including seven in the region of 43–45⁰S, 90–97⁰E. The objects were estimated to be between 5 m and 24 m in length. The surface search was refocused to this area to investigate these sightings and subsequent aerial sightings (Figure 13 and Table 11).

Search activity transitioned to a search and recovery operation from 25 March 2014.

Table 11: Satellite imagery search area

Dates: 20–27 March 2014
Event: Australia (AMSA) satellite imagery search area.
Search area location: Approximately 42⁰S–46⁰S
Search activity: Satellite visual and radar search (multiple nations).

Aerial and surface visual/ radar search.

Datum marker buoys deployed by air to assist in future drift modelling.
Guiding advice: MH370 Inmarsat satellite data unit logs and advice from SATCOM WG to AMSA
Commercial satellite imagery of objects possibly related to MH370 received by AMSA
Data used in planning search area refinement: Assessment of commercial satellite imagery indicates possible debris approximately 148 km southeast of the initial search area.
Search equipment: Aircraft from Australia, New Zealand, United States, Japan, the People’s Republic of China and the Republic of Korea.
Vessels from Royal Australian Navy (RAN) and the People’s Republic of China.
Search area: Refer to Table 12.

Source: ATSB

 


Figure 13: Cumulative area searched from 18 to 27 March 2014

Figure 13: Cumulative area searched from 18 to 27 March 2014

Source: AMSA


Table 12: Search area information 20 to 27 March 2014 (not included here)

There were also possible debris detections from 20 to 23 March 2014, by French satellites at a location 80 to 150 km west of the 7th arc (these are discussed further in the Satellite imagery analysis section).

 

Refined surface search area

By 27 March 2014, following further analysis, the JIT had more confidence in MH370’s speeds derived by the primary radar data captured around Malaysia. The analysis indicated that the aircraft’s rate of fuel burn was higher during this segment of the flight than first thought and therefore its maximum range was decreased. The most probable track moved north to the S3 area and two new search areas designated S4 and S5 were defined (Figure 14). The corresponding drifted areas during this period of the surface search were areas A and B (Figure 15).

The fuel analysis also provided more confidence that the 7th arc represented the point of fuel exhaustion for the aircraft so a recommendation was made to search in a north-easterly direction along the 7th arc from the S3/S4 area boundary (Table 13).

Table 13: Refined surface search area

Dates: 28 March – 3 April 2014
Event: Australia (AMSA/ATSB) refined surface search area.
Search area location: S3/S4 overlap drifted Area A, S3/S4 overlap, drifted Area B.
Search activity: Aerial and surface visual and radar search of areas drifted from the 7th arc by drifting group comprising AMSA, Global Environmental Modelling and Monitoring Systems, CSIRO, Asia-Pacific Applied Science Associates and United States Coast Guard.
Satellite search (multiple nations) of areas drifted from the 7th arc.
Guiding advice: S3/S4 starting from southerly region of S4.

MH370 Inmarsat satellite data unit logs and advice from SATCOM WG.

Briefing by the JIT by telephone from Kuala Lumpur on 27 March 2014 to ATSB embedded team at AMSA.
Data used in planning search area refinement: Greater confidence in increased speeds from primary radar thus increased fuel burn.
More confidence that 7th arc was fuel exhaustion point.
Search equipment: Aircraft from Australia, New Zealand, United States, Japan, the People’s Republic of China, Republic of Korea and Malaysia.
Vessels from the RAN and the People’s Republic of China.
Search area: Refer to Table 14.

Source: ATSB

 

Figure 14: Defined search areas 27 March 2014 (including 7th arc and maximum range cruise boundary) (not included here)

Figure 15: Original and drifted search areas 28 March 2014 to 28 April 2014 (not included here)

Figure 16: Move to refined area 28 March 2014 – planned and cumulative area searched (not included here)

On 28 March 2014 a search of the drifted S3/S4 overlap area (Area A) was commenced. More than 50 objects were sighted and reported on that day (Table 14). Examination of images and recovery of items by surface vessels did not identify any items considered associated with MH370. A search of drifted Area B (Figure 15) within area S4 was undertaken on 2 and 3 April 2014.

 

Figure 17: Area searched and planned to 3 April 2014 (not included here)

Table 14: Search area information 28 March 2014 to 3 April 2014 (not included here)

 

Second refinement surface search area

A second refinement to the SATCOM data analysis was provided by the JIT on 1 April 2014 which indicated the most probable aircraft path crossing at the S4/S5 area boundary. On 2 April 2014 further aircraft performance and flight path analysis starting further to the northwest of Sumatra had the effect of moving the most probable area to the northeast along the 7th arc into areas S4 and S5. Probable impact areas red, yellow and green were then defined (Figure 18). A 20,000 km² priority red area and lower probability yellow and green search areas extending to the southwest along the 7th arc were also defined.

Figure 18: Defined areas at 2 April 2014 showing red, yellow and green boxes, air route M641 and maximum range cruise boundary (not included here)

This analysis was used to guide the remainder of the surface search. Other areas of interest possibly indicating the location of MH370 were incorporated into the search as they became available. The S4/S5 drifted areas C, D, E and F were searched during this period (Figure 15 and Table 15).

Table 15: Second refinement to surface search area

Dates: 3–28 April 2014
Event: Second refinement to surface search area.
Search area location: S3/S4 overlap drifted Area A (3 April). S3/S4 overlap drifted Area B (3–7 April).

Drifted red box (3–7 April). Drifted Ocean Shield flight recorder underwater locator beacon (ULB) hearing report (8–12 April). Drifted Haixun 01 ULB hearing report (13–17 April). Drifted yellow box (18–20 April). Drifted S3/S4 ATSB refined area (21–28 April).

S4/S5 starting at S4/S5 boundary and defined by red/ yellow/green areas.
Search activity: Aerial and surface visual and radar search of areas drifted from 7th arc by expert drifting group of AMSA, Global Environmental Modelling and Monitoring Systems, CSIRO, Asia-Pacific Applied Science Associates and United States Coast Guard.
Satellite search (multiple nations) of areas drifted from the 7th arc coordinated by Australian Geospatial-Intelligence Organisation with areas advised by AMSA/ATSB.
Guiding advice: Areas S4 and S5 starting at S4/S5 boundary and defined by red/yellow/green areas.

MH370 Inmarsat satellite data unit logs and advice from SATCOM WG.
Briefing by the JIT on 2 April 2014 from United Kingdom, United States, Kuala Lumpur to AMSA (ATSB and NTSB embedded).
Follow-up written briefing (refer JIT report at appendix B).
Curtin University report (appendix H) on possible hydroacoustic event in search area (4 and 10 April 2014).
Reported acoustic detections Haixun 01 (4–5 April 2014).
5 April advice from JIT by email on effect of eclipse (resultant cooling and doppler correction) on Inmarsat’s IOR-3 satellite on the signal frequency translation. This resulted in an increase to 425 knots groundspeed and shift to green zone.
Reported ULB detections Ocean Shield (5-10 April 2014).

MH370 PIC Microsoft flight simulator data analysis provided to AMSA/ ATSB by Australian Federal Police (19 April 2014).
Data used in planning search area refinement: Based on the satellite timing data, the aircraft will be located near the 7th arc.

Two scenarios were developed 1A and 1B based on the considered extents of the turn to the south.

  • Scenario 1A had the aircraft fly south immediately after the first arc.
  • Scenario 1B had the aircraft passing waypoint LAGOG before flying south.

The 1B scenario had the aircraft passing close to a northwest point (8⁰ 35.719’N, 92⁰35.145’E) at 1912. This was an initial qualitative assessment of the possible radar coverage from multiple data sources. This point was speculated and used as the furthest point west the aircraft was likely to have flown.
The measured doppler profile closely matched that expected from an aircraft travelling in a southerly direction.
One analysis showed that the best fit for the doppler frequency was at a ground speed of 400 knots, with slightly 'less' best fits at 375 and 425 knots.
A Monte Carlo style analysis, using a number of different starting positions on the second arc also gave a best fit at 400 knots. A most probable speed range of 375 to 425 knots was selected.
One analysis used a combination of aircraft performance and doppler data, obtained from the satellite, to generate a range of probable best fit tracks. This work was supported by a root mean square analysis.
Flight planning carried out by Malaysia Airlines independently showed that there was sufficient fuel on board the aircraft to reach the positions determined by the analysis.
The length of the 7th arc that defined the most probable area was obtained from the overlay of the results of all approaches.
Given the probable battery life of the ULBs and the number of assets available to conduct the underwater search, it was decided to break the underwater search for the ULBs into three smaller areas (red, yellow and green).
The width of the areas was defined by the probable position of the 7th arc, half of the glide range (40 NM) and the area the towed pinger locator (TPL) could cover before the ULB batteries expired.

The area that was crossed by air route M641 was classified as red (Priority 1), the next two priorities, yellow and green, were then defined moving south along the arc from this position.
Search equipment: Aircraft from Australia, New Zealand, United States, Japan, the People’s Republic of China, the Republic of Korea and Malaysia. Vessels from the RAN, Royal Malaysian Navy, Royal Navy, United States Navy and the People’s Republic of China.
Search area: Refer to Table 16.

Source: ATSB

The S4/S5 area boundary on the 7th arc was considered the best starting point due to convergence of a number of candidate paths using independent techniques and because airways route M641 (Figure 16) passed through that location. The equivalent groundspeed of hypothetical flight paths ending in this region was about 363 knots. At this time, drifted Area B was being searched.

On 3 April 2014 the surface search (one mission) of a drifted red area was commenced. This continued until 6 April 2014 when further advice was received from the JIT regarding the cooling effect of an eclipse on the satellite, shifting the calculated groundspeed up to 425 knots and moving more probable paths to the green zone. The aerial search on that day was revised in response to that information.

Sonobuoys were deployed by Royal Australian Air Force P3 Orion aircraft to passively listen for underwater locator beacons. As information relating to the possible location of MH370 was provided to the ATSB, the location of the surface, satellite search and sonobuoy drops were adjusted.

The following items of interest influenced the search areas defined during this period:

  • The People’s Republic of China vessel Haixun 01 reported possible underwater locator beacon (ULB) detections (4 to 5 April 2014) (See The acoustic search for the underwater locator beacons section).
  • Curtin University reported a possible hydrophone detection (4 and 10 April 2014) (See Hydroacoustic analysis section).
  • Ocean Shield reported possible ULB detections (6 to 10 April 2014) (See The acoustic search for the underwater locator beacons section).
  • Five data points were recovered from the PIC’s home flight simulator (19 April 2014) (See Pilot in Command’s flight simulator section).

Table 16: Search area information 3 to 7 April 2014 (not included here)

Following the reported acoustic detections made by Haixun 01 and Ocean Shield on 8 April 2014 the search areas were redefined (Table 17).

Table 17: Search area information 8 to 17 April 2014 (not included here)

The search areas were again refined from 18 April 2014 following the completion of the search in acoustic detection areas to focus on other areas of interest (Table 18).

Table 18: Search area information 18 to 28 April 2014 (not included here)

Details of the daily surface search coverage up to 31 March 2014 can be found on the AMSA website.

On 31 March 2014, the search for MH370 transitioned to an investigation phase with the surface search still coordinated by AMSA as part of a larger interagency response which included ATSB, the Australian Departments of Defence, Foreign Affairs and Trade and Infrastructure and Regional Development headed by the Joint Agency Coordination Centre (JACC).

Search operations coordinated by AMSA were undertaken from 18 March to 29 April 2014 (42 days). A total of 21 aircraft and 19 vessels from Australia, the People’s Republic of China, Japan, Malaysia, New Zealand, the Republic of Korea, United Kingdom and the United States were involved in the AMSA-led surface search.

An animation showing the daily progress of the aerial surface search areas is available for viewing on the ATSB YouTube Channel

 

Debris sightings and recoveries

During the surface search a number of floating objects in the drifted search areas were reported by aircraft, including wooden pallets and fishing equipment. None of these items were assessed as being associated with MH370. Over thirty items of debris were recovered by surface search vessels. All of these items were considered unlikely to be associated with MH370.

Source: The Operational Search for MH370, Australian Transport Safety Bureau, 3 October 2017
https://www.atsb.gov.au/publications/investigation_reports/2014/aair/ae-2014-054/




Extracts from The Operational Search for MH370 have been included here for reference purposes, particularly the sections which relate to the history of the flight; times and events; the aircraft's satellite data unit (SDU); and the Pilot in Command’s flight simulator.