Assistance to Malaysian Ministry of Transport in support of missing Malaysia Airlines flight MH370, on 7 March 2014 UTC

More than 20 items of debris have been recovered and identified as likely to be, almost certainly or definitely originating from MH370. The first of these was the flaperon, found on La Réunion Island on 29 July 2015. Other items have been located along the east and south coast of Africa, the east coast of Madagascar and the Islands of Mauritius and Rodrigues in the Indian Ocean. A complete list of recovered items was published by the Malaysian investigation team and can be found at www.mh370.gov.my/index.php/en/.

An oceanographer from CSIRO was involved in the initial sea surface search for MH370 coordinated by the Australian Maritime Safety authority (AMSA). CSIRO continued to assist in the search for MH370 by completing work predicting landfall areas for floating debris, and analysing the drift of recovered debris.

In April 2016, the ATSB commissioned CSIRO to perform a detailed study of the drift of the recovered debris. The final report of this study has been released concurrently with this report and should be read in conjunction with this section. The CSIRO report and can be found on the ATSB website.

The aim of the CSIRO drift study was to determine the probability of locations along the 7th arc (defined by SATCOM analysis as between 45°S and 22°S) being the origin of the recovered debris.

A forward-tracking numerical simulation was created. Within the simulation, flaperons and other modelled debris were deployed on and around the 7th arc and allowed to drift freely. The simulated paths of the debris were calculated and compared against information from three sets of observations:

1. The extensive aerial and surface search conducted between 18 March and 28 April 2014.

2. The absence of debris from MH370 found anywhere along the coast of Australia.

3. The timing and location of parts from MH370 found on islands in the western Indian Ocean and on the east coast of the African continent.

The following is a summary of the results from the CSIRO drift analysis:

1. From the number and size of items found to date from MH370 there was definitely a surface debris field, so the fact that the sea surface search detected no wreckage argues quite strongly that the site where the aircraft entered the water was not between latitudes 32°S^[4] and 25°S along the 7th arc. Those latitudes are also contra-indicated by an absence of aircraft parts being found off Africa earlier than December 2015.

2. Latitudes south of 39°S are quite strongly contra-indicated by the arrival times of the flaperon and other debris reaching Africa, and the fact that those items were many while findings anywhere on the Australian coastline were nil.

3. The absence of debris being found on African shores in 2014 suggests that the impact site was likely not north of 25°S.

4. Assuming that the crash was within ~25 NM of the 7th arc (ATSB 2016), this leaves only points between 36°S and 32°S that are less than ~25NM from the arc but outside the area that was searched in late 2014 and early 2015.

5. There is a region within the 36-32°S segment of the 7th arc, near 35°S that is most consistent with all of the following lines of evidence, taken together including:

a. The absence of detections during the 2014 surface search.

b. The absence of findings on the WA coastline.

c. The July 2015 arrival time of the flaperon at La Reunion Island.

d. The December 2015 and onwards (only) arrival times of other debris in the western Indian Ocean.

__________

4. Latitudes and longitudes specified as integers, or accompanied by the word ‘near’ in the drift modelling section of the report have an implied uncertainty of 1/2°.

1. There is a very high level of confidence in the search results to date in the current indicative search area. The high resolution sonar coverage is very high and the data has been subjected to a very thorough analysis. The area has been searched to a level of confidence >95% without identifying the aircraft debris field.

2. The analysis of the last two SATCOM transmissions, the likely positon of the aircraft’s flaps at impact and results from recent end of flight simulations has allowed a revision of the distance required to be searched away from the 7th arc. 99% of the DST Group analysis results lie within 25 NM to the east and west of the arc.

3. A residual probability map based on the comprehensive satellite communication data analysis and updated with the latest search results and the CSIRO drift analysis identified a remaining area of high probability between latitudes 32.5°S and 36°S along the 7th arc.

4. The participants of the First Principles Review were in agreement on the need to search an additional area representing approximately 25,000 km² (the orange bordered area in Figure 14). Based on the analysis to date, completion of this area would exhaust all prospective areas for the presence of MH370.

Figure 14. Remaining prospective area to find the wreckage of MH370

Source: ATSB

Click image to enlarge 

Throughout the search, data from a communications satellite along with aircraft performance data has been used to attempt to reconstruct the flight path of MH370 from the time of the last radar contact. Information recorded by a satellite ground station at the time of handshakes^[2] with MH370 was used to estimate the track of the aircraft. SATCOM information from two unanswered ground to air telephone calls was also available. This information showed that the flight continued for approximately five and a half hours after the last radar data.

The methodologies for the calculation of flight paths were included in the ATSB’s reports MH370 – Definition of Underwater Search Areas report of 26 June 2014 and updated on 18 August 2014, MH370 – Flight Path Analysis Update of 8 October 2014 and MH370 – Definition of Underwater Search Area Update of December 2015.

The calculations identified seven ‘arcs’ which lead to the definition of the search area along the current north-south line of the 7th arc (which is regarded as the primary datum for determining the search area). It was then necessary to define which section of the 7th arc has the highest likelihood of finding the aircraft and the width of the search area to the east and west of the arc; encompassing aircraft performance limits and end of flight scenarios.

The DST Group provided expert analysis of the available SATCOM data relating to MH370. The analysis used models of the Inmarsat SATCOM data, aircraft dynamics, and meteorological data to determine likely flight paths. The DST Group analysis has been published in the book, Bayesian Methods in the Search for MH370. The methodology was subjected to a set of validation experiments to ensure that the set of predicted flight paths aligned with actual flight data for previous flights of the accident aircraft (registered 9M-MRO) and other flights in the air at the same time as the accident. Further burst frequency offset (BFO) analysis performed by DST Group was contained in the ATSB report of 2 November 2016, MH370—Search and debris examination update.

At the First Principles Review meeting, experts discussed their work to refine the analysis and considered the possible analysis techniques, validations and accident result scenarios. Their particular focus was the effect of the sonar search results to date on the probability map for the search area.

Search results and likely aircraft autopilot mode

The DST Group analysis which used a dynamic model of the aircraft, examined five different lateral aircraft autopilot control modes:

1. Constant magnetic heading (CMH).

2. Constant true heading (CTH).

3. Constant magnetic track (CMT).

4. Constant true track (CTT).

5. Lateral navigation (LNAV).

The initial analysis assumed equal likelihood (uniform probability) across the lateral aircraft modes throughout the southern portion of the accident flight. The results of the analysis suggested that based on the satellite data, the aircraft was more likely to be operating at the time in the CTT or LNAV lateral control modes. These lateral control modes generally resulted in the aircraft’s flight path being towards the southern end of the search area. The remaining three lateral control modes generally resulted in the aircraft’s flight path ending north of the CTT and LNAV results, up to 33°S in latitude along the 7th arc.

The southern portion of the search area which mainly encompasses the CTT and LNAV lateral control mode results has been thoroughly searched with underwater assets (deep tow, AUV, and ROV). Based on the results of the underwater search, the probability distribution was updated to reflect the new information of the unsuccessful search which then favoured the other control modes.

Flight crew advice

During the First Principles Review meeting, flight crew with extensive experience on the aircraft type indicated that the aircraft is usually flown in the LNAV or CMH lateral control modes.

This information, combined with the results from the areas already searched to increases the likelihood in the northern section of the probability map in Figure 13.

__________

2. A handshake in satellite communication is a series of signalling messages that establish or maintain a communication channel.

The following factors which affect the width of the search were defined previously, in the ATSB publication MH370 – Definition of Underwater Search Area Update of December 2015:

• Tolerance in the calculation of the arcs.
• A series of end of flight simulations conducted in 2014.
• A basic turn analysis.
• A review of previous accidents.
• The maximum range of the aircraft if glided after fuel exhaustion.

Analysis of these factors resulted in three areas of decreasing probability at 20 NM, 40 NM, and 100 NM from the 7th arc.

The latest ATSB report of 2 November 2016, MH370—Search and debris examination update, provided new information relating to the end of flight. This new information included:

• The analysis of the debris recovered from MH370 indicating that the flaps were likely in a retracted position.
• The analysis of the BFO from the final two SATCOM transmissions which indicated that the aircraft was likely to be on an unstable flight path.
• Results from recent simulations showed high rates of descent broadly consistent with the BFO analysis. These simulations indicated that the aircraft was likely to be within 15 NM of the 7th arc.

This information provided significantly more weight to the aircraft being located closer to the arc than the ATSB concluded in 2015—probably within 25 NM, with locations closer to the 7th arc a higher likelihood.

This analysis, and the implications for the width of the search area were presented at the First Principles Review meeting. All participants were in general agreement that the distance required to be searched from the arc could be reduced to 25 NM from the 7th arc with a weighting to the west to account for the arc altitude^[3].

__________

3. The reference 7th arc (search datum) is at an altitude of 40,000 ft. It is likely that the aircraft was at a lower altitude (and therefore closer to the sub-satellite point) at the time of the final SATCOM transmissions and so the distance to the west of the reference arc which should be searched is slightly more.

DST Group have used the Bayesian approach to incorporate multiple sources of analysis into a single probability map, or probability density function (PDF), of the location of the aircraft.

The main PDF is generated from the analysis of the satellite data and the search area width analysis. The residual PDFs show the effects of the other analyses (i.e. search results and drift analysis) on the probabilities.

Figure 11 shows the result of the SATCOM PDF updated with the search results. The areas searched were removed from the PDF. The residual probability is located in areas yet to be searched, with two clear areas of interest: north of the current search area and south of the current search area.

Figure 11. Updated probability distribution with the results of the underwater search.

Source: Google Earth / DST Group

Figure 12 shows the SATCOM PDF with the CSIRO drift study of the flaperon arrival at La Reunion Island likelihood overlaid. The alignment of the high likelihood point of origin of the flaperon from the drift analysis (green) and the peak of the northern SATCOM analysis PDF can be clearly seen (red circle).

Figure 12. Updated probability distribution with the results of the underwater search and the drift analysis results overlaid

Source: Google Earth / DST Group

Figure 13 shows the search probability distribution based on the SATCOM data and CSIRO drift analysis. The section south of the indicative search area (pink box in figure 12) becomes much less favourable once the drift results are incorporated.

Figure 13. Updated probability distribution with the results of the underwater search and the drift analysis

Source: Google Earth / DST Group

In May 2014 the Governments of Australia, Malaysia, and People’s Republic of China agreed that the Australian Transport Safety Bureau (ATSB) would coordinate the underwater search for MH370. The primary objective was to assist the ICAO Annex 13 investigation by locating and positively identifying the aircraft wreckage. It was also essential that any searched area assessed as not containing the aircraft could be discounted with a high degree of certainty.

In November 2016, the high priority underwater search area defined in the ATSB’s previous reports was in its final stages of being searched. As such, the ATSB determined that a review of all available information relating to the search area definition was required. Participants at the three-day meeting held from 2-4 November 2016 at the ATSB office in Canberra included experts from each field of expertise where information was available to assist in the search area determination.

Accordingly, there were representatives at the meeting from all of the organisations participating in the Search Strategy Working Group including Australia’s Defence Science and Technology Group (DST Group), Boeing, Thales, Inmarsat, the National Transportation Safety Board of the US, the Air Accidents Investigation Branch of the UK and the Department of Civil Aviation, Malaysia. In addition, there were representatives from the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Geoscience Australia, Curtin University, Malaysia Airlines and the People’s Republic of China.

The aim of the First Principles Review meeting was to consider the results of the underwater search to date, examine the data and analysis associated with the accident flight, and the definition of the search area. The meeting also focussed on new analysis relating to recovered aircraft debris.

Abbreviated minutes

The first day of the meeting focused on a comprehensive review of the satellite communications (SATCOM) data, and the analysis methods used to estimate the aircraft’s final location. The meeting included presentations from all organisations with subject matter expertise related to the SATCOM system. The review re-examined the detailed assumptions, calculation methods, and validations that led to the definition of the search area. The analyses had been verified using data from previous flights. The meeting participants determined that techniques used were acceptable and the results for the analysis of the accident flight were valid.

The second day of the meeting focused on the debris that was recovered from the islands to the east of Africa and the African coast from Tanzania to South Africa. CSIRO presented the analysis which examined the rate of movement (drift) of the flaperon (found on La Réunion Island in 2015) and other items, and its correlation to drift models. The results of this analysis identified an area of likely origin of the recovered debris (i.e. the aircraft’s impact location). ATSB experts presented conclusions from the examination of the recovered flap section with respect to the likely configuration of the aircraft at the end of flight. The meeting participants determined that the analysis presented on the debris and subsequent results were valid.

The results of the underwater search were also presented including the search methods, completed coverage, sonar data interpretation, quality assurance and confidence in the results. A presentation on the hydro-acoustic data at the time of the accident allowed meeting participants to determine that hydro-acoustic analysis did not contribute any useful new information to the search.

On the third day, the meeting examined how the results of the search to date, the flight path modelling based on the satellite data, the drift modelling and the debris analysis may assist in the definition of any future search activities and the priorities for such activities.

To assist with the underwater search for 9M-MRO, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) undertook an analysis of existing ocean data from the Global Drifter Program^[3]. The analysis used the behaviour of drogued and undrogued drifters^[4], as well as numerical simulations using ocean models. The purpose of this work was to trace any recovered debris to its likely point of origin. However, a drifter’s geometry and buoyancy is not generally representative of aircraft debris and it was considered that the drift characteristics might also be different. To account for this difference, the CSIRO engaged in field work, studying how aircraft debris moves through the water compared to drifters, with regard to wind and ocean currents. This data was incorporated into numerical simulations in order to predict the drift behaviour of aircraft debris with more confidence.

As part of the ongoing field testing, the drift behaviour of replica flaperons and other recovered aircraft parts is being assessed. Replica flaperons were constructed with dimensions and buoyancy approximately equal to that of the recovered flaperon (Figure 7), which was float-tested during the detailed examinations in France. The replica flaperons were deployed into a bay for short term tests during various weather conditions. Longer term tests were then performed in the open ocean. For comparison, undrogued drifters were deployed alongside the flaperons. Drogued drifters were also used, because they move predominantly with the currents, as opposed to wind and waves. Data for currents was then able to be subtracted from the flaperons’ drift data so that wind and wave behaviour could be assessed in isolation.

Figure 7: Flaperon recovered from Reunion Island on 29 July 2015

Source: Bureau d’Enquetes et d’Analyses (BEA)

Field tests demonstrated that the replica flaperons drift similarly to undrogued drifters:

• In low wind conditions, the flaperons move slightly faster than undrogued drifters due to the energy absorbed from waves.
• In higher winds, the energy absorbed from waves was less significant, and the flaperons’ behaviour was analogous to the undrogued drifters’.

The replica flaperons presented their raised trailing edge to the wind, allowing waves to propel them in the wind direction. If waves tipped or turned the flaperons, the wind quickly reoriented them, so the direction of movement remained consistent.

Replicas of two other recovered items of debris drifted at a rate that was practically indistinguishable from undrogued oceanographic drifters in all wind conditions. Therefore, the trajectories of undrogued oceanographic drifters were valid for use in the analysis.

Preliminary results from the updated drift analysis indicated that the current search area was a possible origin for the recovered debris.

Using the collected field data, a new forward-tracking numerical simulation was performed. Within the simulation, flaperons were deployed on and around the current search area and allowed to drift freely. Results after 500 days of simulated drift are presented in Figure 8. For comparison, Figure 9 shows the results of a simulation where the original undrogued drifter model was used. By comparing the two figures, it can be seen that the flaperons generally moved further west within 500 days due to the extra speed at low winds.

Figure 8: Simulated location of flaperon-type drifters after 500 days

Source: CSIRO

Figure 9: Simulated location of undrogued drifters after 500 days

Source: CSIRO

Small errors in the simulation can result in large divergences over time. As such, an examination of the debris behaviour in the first months after the accident was conducted.

Figure 10 illustrates the starting location of the simulated drifters along the 7th arc. After eight months of simulated drift (Figure 11), some initial conclusions can be drawn about the drifter’s path with respect to debris discovered to date. A significant number of drifters arrived on the coast of Western Australia. Similarly, a number of drifters had arrived on the coast of Africa. The colour of each drifter identifies its starting location as marked along the arc.

• Drifters starting in the southern half of the current search area or below (dark blue, green, light blue) can be observed on and around the coast of Western Australia, with many drifting towards Tasmania. No debris has been discovered on the Australian coast. This indicates that a starting location within the current search area, or further north, is more likely.
• A significant number of red drifters have already reached the coast of Madagascar and mainland Africa. This is not consistent with the time at which debris was discovered. The first item of debris was not discovered on Reunion Island until 16 months after the accident. This suggests a reduced likelihood of debris originating from the northernmost areas shown in Figure 10 (red and white coloured regions).

Refinement of the drift analysis is continuing. Flaperon replicas are currently deployed in the open ocean along with drogued and undrogued drifters, and replicas of smaller debris. This is to study the longer-term drift behaviour of the parts in conditions similar to those expected in the Indian Ocean. The long-term tests may provide additional improvement to the simulations and confidence in the backtracking results.

Figure 10: Simulated starting location of undrogued drifters

Source: CSIRO

Figure 11: Simulated location of undrogued drifters after 8 months

Source: CSIRO

A significant number of drifters from the light blue and green areas have made landfall on the West Australian coast. Similarly, drifters from the red and white areas have begun to make landfall on the African coastline. Neither are consistent with times and/or locations at which MH370 debris was discovered, therefore reducing the likelihood of debris originating from these locations.

Analysis

Damage to the internal seal pan components at the inboard end of the outboard flap was possible with the auxiliary support track fully inserted into the flap. That damage was consistent with contact between the support track and flap, with the flap in the retracted position. The possibility of the damage originating from a more complex failure sequence, commencing with the flaps extended, was considered much less likely.

With the flap in the retracted position, alignment of the flap and flaperon rear spar lines, along with the close proximity of the two parts, indicated a probable relationship between two areas of damage around the rear spars of the parts. This was consistent with contact between the two parts during the aircraft breakup sequence, indicating that the flaperon was probably aligned with the flap, at or close to the neutral (faired) position.

Numerous other discrete areas of flap damage were analysed. Some of the damage was consistent with the flaps in the retracted position, while other areas did not provide any useful indication of the likely flap position. It was therefore concluded that:

• The right outboard flap was most likely in the retracted position at the time it separated from the wing.
• The right flaperon was probably at, or close to, the neutral position at the time it separated from the wing.

__________

3. Visit www.aoml.noaa.gov/phod/dac/ for further details.
4. A drifter is a satellite-tracked buoy which either has a subsurface sea anchor attached (drogued) or not (undrogued).

The ATSB report MH370 – Definition of Underwater Search Areas, December 2015 outlined the previous simulations that the manufacturer had undertaken to assist in determining the aircraft’s behaviour at the end of the accident flight.

In April 2016, the ATSB defined a range of additional scenarios for the manufacturer to simulate in their engineering simulator. Reasonable values were selected for the aircraft’s speed, fuel, electrical configuration and altitude, along with the turbulence level.

The results of the simulation are presented in Figure 6. The results have all been aligned to the point two minutes after the loss of power from the engines. This is the theorised time at which the 7th arc transmissions would have been sent.

Figure 6: Results from simulated scenarios

Source: ATSB

This figure illustrates the resulting flight paths from the simulations performed by the manufacturer and aligned at a point consistent with when the final BTO transmission may have occurred.

The simulations were completed in the manufacturer’s engineering simulator. The engineering simulator uses the same aerodynamic model as a Level D simulator used by the airlines. The simulator is not a full motion simulator but instead is used when a high level of system fidelity is required. The appropriate firmware and software applicable to the accident aircraft can be loaded.

The results of the simulations were that:

• The aircraft was capable of travelling rearwards (from the direction of travel) approximately 21 NM.
• Simulations that experienced a descent rate consistent with the ranges and timing from the BFO analysis generally impacted the water within 15 NM of the arc.
• In some instances, the aircraft remained airborne approximately 20 minutes after the second engine flameout.
• In an electrical configuration where the loss of engine power from one engine resulted in the loss of autopilot (AP), the aircraft descended in both clockwise and anti-clockwise directions.
• In some simulations, the aircraft exhibited phugoid motion^[2] throughout the descent.
• Simulations that exhibited less stable flight resulted in higher descent rates and impact with water closer to the engine flameout location. In some simulations, the aircraft’s motion was outside the simulation database. The manufacturer advised that data beyond this time should be treated with caution.
• Some of the simulated scenarios recorded descent rates that equalled or exceeded values derived from the final SATCOM transmission. Similarly, the increase in descent rates across an 8 second period (as per the two final BFO values) equalled or exceeded those derived from the SATCOM transmissions. Some simulated scenarios also recorded descent rates that were outside the aircraft’s certified flight envelope.
• The results of the scenarios, combined with the possible errors associated with the BTO values indicate that the previously defined search area width of ±40 NM is an appropriate width to encompass all uncontrolled descent scenarios from the simulations.

The simulated scenarios do not represent all possible scenarios, nor do they represent the exact response of the accident aircraft. Rather, they provide an indication as to what response the accident aircraft may have exhibited in a particular scenario. As such, the results are treated with caution, and necessary error margins (or safety factors) should be added to the results.

It was not possible to simulate all likely scenario conditions due to the limitations of the simulator. Specifically, flight simulators are unable to accurately model the dynamics of the aircraft’s fuel tanks. In the simulator, when the fuel tank is empty, zero fuel is available to all systems fed from the tank. However, in a real aircraft, various aircraft attitudes may result in unusable fuel (usually below engine/APU inlets) becoming available to the fuel inlets for the APU/engines. If this resulted in APU start-up, it would re-energise the AC buses and some hydraulic systems. This could affect the trajectory of the aircraft. Similarly, the left and right engines may also briefly restart, affecting the trajectory.

__________

2. A long-period oscillation of pitch axis, perpetually hunting about level attitude and trimmed speed.

Currently, more than 20 items of debris have been brought to the attention of and are of interest to the investigation team. The items have been located along the east and south coast of Africa, the east coast of Madagascar and the Islands of Mauritius, Reunion and Rodrigues in the Indian Ocean. A list of items recovered was published by the Malaysian investigation team and can be found at www.mh370.gov.my/index.php/en/.

The right flaperon has been examined by the French Judiciary and confirmed to have originated from 9M-MRO. Six further items of debris have previously been examined by the ATSB, comprising a:

• section of the right outboard flap fairing
• panel section from the right horizontal stabiliser
• piece of engine cowling
• closet panel section from the closet adjacent to door R1
• inboard section of the right outboard flap
• trailing edge section of the left outboard flap.

Both flap sections had unique identification numbers that were able to be linked, through manufacturing records, to 9M-MRO. The remaining examined items were confirmed as Boeing 777 parts and had identifying features linking them to a Malaysian Airlines origin, however there were no unique identifiers to link the parts directly to 9M-MRO. The parts were therefore determined to have almost certainly originated from 9M-MRO, given that the likelihood of originating from another source is very remote. The ATSB debris examination reports are available at www.atsb.gov.au/mh370-pages/updates/reports/.

Outboard flap failure analysis

The recovered right, outboard wing flap section (Figures 12, 13 and 14) was examined for any evidence of interaction with mechanisms, supports and surrounding components that may indicate the state of flap operation at the time of fracture and separation from the wing. The purpose of the examination was to inform the end-of-flight scenarios being considered by the search team. The most significant items of evidence in relation to this are documented below.

Figure 12: Location of recovered outboard flap section

Source: DST Group (Modified by ATSB)

Figure 13: Inboard section of outboard flap

Source: ATSB

Figure 14: Inboard section of outboard flap (inverted)

Source: ATSB

Flap position

The trailing edge outboard wing flaps form part of the aircraft’s high-lift control system and are deployed to alter the shape of the aircraft wing, improving lift at lower aircraft speeds during takeoff, approach and landing. The outboard wing flaps have defined stages of flap deployment between ‘up’ (retracted / cruise position) and 30-units of extension (landing position).

A fibreglass and aluminium seal pan is located at the inboard end of the outboard flap. It houses the inboard auxiliary support, comprising a deflection control track (support track) and carriage assembly. The support track is affixed to the rear of the wing. Using rollers in the carriage assembly, the inboard end of the flap is guided along the support track as the flap moves through its deflection range. The track is fully inserted into the flap in the ‘up’ position and progressively withdrawn from the flap as the flaps are deployed (Figure 15). The inboard auxiliary support track and carriage assembly were not present with the recovered debris.

Two adjacent aluminium stiffeners within the inboard seal pan area exhibited impact damage. The damage was significant because it was indicative of impact damage and the only component in the vicinity of the stiffeners, capable of independent movement within the seal pan, was the support track. Measurements of the support track position at the various stages of flap deployment, indicated that the track would have to be fully inserted into the flap in the retracted position to be adjacent to the damaged stiffeners (Figures 16, 17 and 18).

An outwards-fracture of the fibreglass seal pan initiated at a location adjacent to the damaged aluminium stiffeners (Figure 19). The damage was most likely also caused by impact from the support track. That damage provided further evidence of the support track position within the flap seal pan cavity, indicating that the flaps were retracted at the point of fracture and separation from the wing.

Figure 15: Outboard flap, inboard auxiliary support

Source: Boeing (modified by ATSB)

Figure 16: Outboard flap location of damaged stiffeners within the seal pan cavity
Source: Boeing (modified by ATSB) / ATSB

Figure 17: Outboard flap, damaged stiffeners within the seal pan cavity
Source: ATSB

Figure 18: Outboard flap, damaged stiffeners within the seal pan cavity
Source: ATSB

Figure 19: Outboard flap, fractured seal pan (forward)

Source: ATSB

Contact damage between the flaperon and outboard flap

The flap seal pan was also fractured adjacent to the rear spar. The fracture resulted from external impact, puncturing the fibreglass and plastically deforming the supporting aluminium structure within the seal pan cavity (Figure 20). Comparable damage was noted at the outboard, rear spar and surrounding structure of the adjacent flaperon (Figure 21). It was noted that the two areas in question are aligned when the flaps are in the retracted position, with a significant offset existing at other stages of flap extension (Figure 22).

Figure 20: Outboard flap, fractured seal pan (aft)

Source: ATSB

Figure 21: Flaperon, outboard side damage

Source: Direction générale de l'armement / Techniques aéronautiques (modified by ATSB)

Figure 22: Flaperon and outboard flap from below, showing relative alignment of rear spar rivet line (highlighted) in the flaps retracted (left) and extended position (right)

Source: ATSB

The final satellite communication (Satcom) transmissions between the Inmarsat Ground station and 9M-MRO occurred at 00:19 on the 8th March 2014. These transmissions were the aircraft logging on to the Satcom system, likely after an interruption to the power that supplies the satellite data unit (SDU) – an integral part of the Satcom system.

The Use of Burst Frequency Offsets in the Search for MH370 – Defence Science and Technology (DST) Group paper.

The ground station Satcom logs recorded the burst timing offset (BTO) and the burst frequency offset (BFO) for each received message. A complete explanation of the BTO and BFO is provided in the ATSB publication, MH370 – Definition of Underwater Search Areas, August 2014.

The BFO is a function of the Doppler shifts imparted on the communication signal due to the motion of the satellite and the aircraft. The relationship is more complicated than a direct Doppler calculation because the aircraft software contains Doppler compensation that offsets the Doppler shift due to the aircraft motion. Although the aircraft attempts to compensate for its own motion, it does this under the assumption that the communications satellite is in notional geostationary orbit and it does not include the vertical component of the aircraft velocity.

Analysis of the BFO value can provide information about the relative motion between the satellite and the aircraft. Figure 1 shows all the BFO recordings from 9M-MRO. The comprehensive analysis provided by the Defence Science and Technology (DST) Group (Bayesian Methods in the Search for MH370) indicated that the aircraft was likely on a southerly heading at 18:39. From that point until 00:11, all the solutions of the analysis showed a continuing southerly track.

Figure 1: Recorded BFO values throughout the flight

Source: ATSB

This graph illustrates the measured BFO recordings throughout the flight with the appropriate error bars on the measurements. After 18:39 the BFO values follow an approximately linear trend until the final two values at 00:19.

The trend of the BFO values from 18:39 until the 6th arc (00:11) is due to the change in location of the aircraft and can be linearly approximated (Figure 2). If this linear approximation is extrapolated to 00:19, and if neither the Satcom system nor the aircraft flight path were altered after 00:11, a BFO value of approximately 260 Hz would have been expected.

Figure 2: Linear approximation of the BFO values between 18:39 and 00:11

Source: ATSB

This graph illustrates 5 BFO values recorded between 18:39 and 00:11 and the linear approximation of the BFO at 00:19. The first 5 values correspond to the 2nd-6th arcs. During this time the aircraft is likely to be following a relatively constant southerly track. Continuing this linear trend to 00:19, a value of 260Hz would be expected.

The recorded values of the BFO for the two messages at 00:19 were the following:

Table 1: Recorded BFO values at 00:19

To explain this difference between the expected BFO value (260 Hz) and the recorded BFO values (Table 1), an examination was undertaken of the elements that contribute to the BFO.

This analysis includes a number of approximations, and the results should be interpreted as an approximate guide on the range of possible descent rates at the time of the last two SATCOM messages that were sent from 9M-MRO. DST Group intend to publish a more detailed version of the analysis in the near future. It should be noted that small refinements in the analysis may result in descent rate calculations that differ slightly from the values published here.

In the analysis it is assumed that there were no major changes to the satellite system between 00:11 and 00:19. Therefore the contributing elements consist of the:

• tolerance or error of the BFO
• direction of travel of the aircraft
• oven-controlled oscillator warm-up drift
• descent rate of the aircraft.

BFO tolerance or error

A statistical analysis of the BFO error from all the 20 previous flights of 9M-MRO identified that the distribution was approximately Gaussian (see DST Group book – link above) with a standard deviation of 4.3 Hz. ±3 standard deviations (12.9 Hz) is a conservative choice for the error.

Direction of flight

For any given speed, the estimated BFO differences can be plotted against the predicted heading of the aircraft (Figure 3). The maximum variation in the BFO differences based solely on change in direction is approximately 20 Hz.

Figure 3: Variation in estimated BFO differences at 00:19 for given track angles and groundspeed

Source: DST Group

This graph indicates that the lowest BFO differences, and therefore the closest to our measured values, would be attained for any given speed by continuing in a southerly direction.

Oscillator warm-up drift

The oven-controlled crystal oscillator (OCXO) maintains the oscillator in the satellite data unit (SDU) at the design temperature. The performance of the OCXO in maintaining the correct temperature directly affects the transmitted frequency. When power is first applied to the SDU, the transient temperature variation associated with the OCXO warming-up causes a variation in the output frequency. This is referred to as warm-up drift.

To further understand this behaviour, the manufacturer of the SDU performed multiple power-up tests on several SDUs. It was observed that individual SDUs exhibit different warm-up drift characteristics. The differences were the magnitude of the frequency deviation, the time to reach steady state as well as the general shape of the curve.

Variations in the time in which the SDU (and OCXO) was not powered, prior to powering on, affected both the magnitude of the drift and the time taken for the frequency to stabilise, however the characteristic (or general shape of the curve) was not affected.

All available information indicated that, after power-up, the SDU in 9M-MRO exhibited a decay characteristic, represented in Figure 4. The values recorded shortly after power up would therefore be greater than the steady state value.

Figure 4: Representation of 9M-MRO SDU decaying warm-up characteristic (not to scale)

Source: ATSB

This graph illustrates the warm-up characteristic of the 9M-MRO SDU. After power is restored to the SDU, the OCXO drift results in BFO value being above the steady state value until the OCXO has stabilised.

The maximum OCXO drift value observed in the previous data of 9M-MRO was around 130 Hz and if the power interruption was sufficiently short, the OCXO drift could be negligible.

Descent rate

The remaining element to explain the difference in the predicted BFO value and the recorded BFO value is the descent rate of the aircraft. Analysis shows that at locations consistent with the search area and at the time of the last transmission, the descent rate affects the BFO value at -1.7 Hz per 100 ft/min.

Results of analysis

Due to the uncertainties associated with the end-of-flight scenario, it is not possible to define a specific descent rate from the recorded BFO values. Instead, using the limits of each contributing element, a range of possible descent rates, consistent with the recorded BFO values can be determined.

Case A and Case B below represent the boundary cases for the minimum descent rate and the maximum descent rate respectively. For each transmission at 00:19, Case A applies assumptions that reduce the required rate of descent to match the recorded BFO. Case B does the opposite and applies assumptions which increase the required rate of descent.

A. Minimum Descent Rate

• Southerly direction,
• Maximum positive error of measured BFO for 00:19:29 and 00:19:37 (~ 13 Hz),
• No OCXO drift – very short duration power interruption.

B. Maximum Descent Rate

• Northerly direction,
• Maximum negative error on measured BFO at 00:19:29 and 00:19:37 (~ -13 Hz),
• Maximum OCXO drift – 130 Hz (as observed in other power-up logons of 9M-MRO).

Table 2 and Figure 5 following provide the resulting descent rates based on cases above for the log-on request at 00:19:29 and the log-on acknowledge at 00:19:37.

Table 2: Derived descent rate boundary cases

Figure 5: Association of BFO differences to descent at 00:19

Source: ATSB

The ATSB would like to acknowledge the following organisations for their input and continued assistance with the analysis:

• Air Accidents Investigation Branch (UK)
• Australian Bureau of Meteorology
• Australian Defence Science and Technology Group
• Boeing
• Commonwealth Scientific and Industrial Research Organisation
• Department of Civil Aviation, Malaysia
• Inmarsat
• Malaysian Airlines Berhad
• Malaysian Ministry of Transport
• National Transportation Safety Board (US)
• Thales.

Those involved have dedicated many hours outside of normal duties to advance the collective understanding of the event. The main focus has always been in finding the aircraft to assist the Malaysian investigation team and to bring closure to the families of the passengers and crew of MH370.

Published: 7 October 2016 (amended 17 August 2017)

Debris examination – update No. 5

Identification of wing trailing edge debris recovered from Mauritius

Introduction

An item of composite debris was recovered on the island of Mauritius around 10 May 2016. The item profile was consistent with the trailing edge of an aircraft wing. The item was subsequently collected by a member of the Malayisan investigation team and hand-delivered to the Australian Transport Safety Bureau for identification.

This document is a brief summary of the item identification, designated part number 6. It follows the previous identification and examination reports available on this website at www.atsb.gov.au/mh370. This summary is released with the concurrence of the Malaysian ICAO Annex 13 Safety Investigation Team for MH370.

Identification

Part No. 6

A part number was identified on a section of the debris, identifying it as a trailing edge splice strap, incorporated into the rear spar assembly of a Boeing 777 left outboard flap. This was consistent with the appearance and construction of the debris.

Adjacent to the part number was an “OL” part identifier, similar to those found on the right outboard flap section (Examination update 3). The flap manufacturer supplied records indicating that this identifier was a unique work order number and that the referred part was incorporated into the outboard flap shipset line number 404 which corresponded to the Boeing 777 aircraft line number 404, registered 9M-MRO and operating as MH370.

Figure 1: Left outboard flap trailing edge section showing part identification numbers

Source: ATSB

Conclusion

Part number 6 was a trailing edge section of Boeing 777 left, outboard flap, originating from the Malaysia Airlines aircraft registered 9M-MRO.

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Download PDF of the Debris report 5

Published: 22 September 2016

Debris examination – update No. 4

Preliminary examination of two items of debris recovered near Sainte Luce, Madagascar

Introduction

Two items of fibreglass-honeycomb composite debris were recovered near Sainte Luce on the south-east coast of Madagascar, having reportedly washed ashore in February 2016. They were hand-delivered to the Australian Transport Safety Bureau on 12 September 2016. The items were initially reported in the media as being burnt.

This document summarises the ATSB’s preliminary examination of the items for any evidence of exposure to heat or fire.

Examination

No manufacturing identifiers, such as a part numbers or serial numbers were present on either item, that may have provided direct clues as to their origin. At the time of writing, the items had not been identified and work in this respect is ongoing.

A dark grey colouration was present on a significant proportion of both sides of each item (Figures 1, 2 and 3). Detailed examination of these areas showed that the colour related exclusively to a translucent resin that had been applied to those surfaces (Figure 4).

A cross section through the panel showed a clear delineation between the dark resin and the other surface coatings without any evidence of gradual transition. The lighter grey surface areas resulted from a thinner film of the same resin applied over an off-white background. Figure 5 shows the cross section directly and Figure 6 shows the same section at an oblique angle. This confirmed that the dark colour of the coating was an inherent property of the resin, and not the result of exposure to heat or fire.

Despite no evidence of overall gross heat damage, two small (<10mm) marks on one side of the larger item and one on the reverse side were identified as damage resulting from localised heating (Figures 2 and 3). A burnt odour emanating from the large item was isolated to these discrete areas. The origin and age of these marks was not apparent. However, it was considered that burning odours would generally dissipate after an extended period of environmental exposure, including salt water immersion, as expected for items originating from 9M-MRO.

Figure 1: Smaller composite panel

Source: ATSB

Figure 2: Larger composite panel showing discrete area of heat damage

Source: ATSB

Figure 3: Reverse side of larger composite panel showing discrete areas of heat damage



Source: ATSB

Figure 4: Close-up of applied coatings

Source: ATSB

Figure 5: Cross-section through composite skin, showing surface colouration through thickness

Source: ATSB

Figure 6: Higher magnification image of Figure 5, showing clear delineation between layers

Source: ATSB

Summary

The following findings were made during a preliminary examination of two items of composite debris, recovered near Sainte Luce, Madagascar. At the time of writing, work is ongoing to determine the origin of the items, specifically, whether they originated from a Boeing 777 aircraft.

1. The dark grey colouration on the outer surfaces of the items related to an applied resin and was not the result of exposure to heat or fire.
2. Three small marks on the larger item were indicative of localised heating. The age and origin of these marks was not apparent.

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Download PDF of the Debris report 4

Published: 12 May 2016 (amended: 24 May 2016 and 17 August 2017)

Debris examination – update No. 2

Identification of two items of debris recovered from the beaches in South Africa and Mauritius

Introduction

On 22 and 30 March 2016, two items of debris were independently found on beaches at Mossel Bay, South Africa and Rodrigues Island in Mauritius. Both items were delivered to the relevant Civil Aviation Authorities in South Africa and Mauritius. Assistance from the Australian Transport Safety Bureau (ATSB) was requested by the Malaysian Government in the formal identification of the items to determine if they came from the Malaysia Airlines Boeing 777 aircraft, registered 9M-MRO, operating as MH370.

The items were packaged in South Africa and Mauritius respectively and delivered safe-hand to the ATSB in their original packaging, in the custody of the ICAO Annex 13 Safety Investigation Team members.

This document (Update 2) is a brief summary of the outcomes from the identification of these items, designated as Part numbers 3 and 4. It follows the identification of Part numbers 1 and 2, the outcomes of which were released by the ATSB in Update 1 on 19 April 2016. This debris identification summary is released with the concurrence of the Malaysian ICAO Annex 13 Safety Investigation Team for MH370.

Quarantine and marine ecology

On arrival into Australia, both parts were quarantined at the Geoscience Australia facility in Canberra. The parts were unwrapped and examined for the presence of marine ecology and remnants of biological material. Visible marine ecology was present on both parts and these items were removed and preserved. The parts were subsequently cleaned and released from quarantine.

Identification

Part No. 3

Part number 3 was initially identified from the partial Rolls-Royce stencil as a segment from an aircraft engine cowling. The panel thickness, materials and construction conformed to the applicable drawings for Boeing 777 engine cowlings.

There were no identifiers on the engine cowling segment that were unique to 9M-MRO, however the Rolls-Royce stencil font and detail did not match the original from manufacture. The stencil was consistent with that developed and used by Malaysia Airlines and closely matched exemplar stencils on other Malaysia Airlines Boeing 777 aircraft (Figure 1).

There were identical inboard and outboard stencils present on the cowlings of each of the engines and the location of the stencils was found to vary between engines. Taking that into consideration, there were no significant differentiators on the cowling segment to assist in determining whether the item of debris was from the left or right side of the aircraft, or the inboard or outboard side the cowling.

On 17 May 2016, the ATSB was provided with an earlier photograph of the item, taken on 23 December 2015. This photograph showed the part was significantly colonised by barnacles at the time it arrived on the beach (Figure 3).

Part No. 4

Part number 4 was preliminarily identified by the decorative laminate as an interior panel from the main cabin. The location of a piano hinge on the part surface was consistent with a work-table support leg, utilised on the exterior of the Malaysia Airlines Door R1 (forward, right hand) closet panel (Figure 2). The part materials, dimensions, construction and fasteners were all consistent with the drawing for the panel assembly and matched that installed on other Malaysia Airlines Boeing 777 aircraft at the Door R1 location.

There were no identifiers on the panel segment that were unique to 9M-MRO, however the pattern, colour and texture of the laminate was only specified by Malaysia Airlines for use on Boeing 747 and 777 aircraft. There is no record of the laminate being used by any other Boeing 777 customer.

Figure 1: Comparison of Boeing 777 engine cowling stencils

Note the thickness of the “ROYCE” lettering and the serif geometry on the main ‘R’s (enlarged for ease of comparison).

Source: Malaysian MOT / ATSB

Figure 2: Comparison of recovered item with Malaysia Airlines Boeing 777 Door R1 panel assembly



Source: Malaysian MOT / ATSB

Figure 3: Photograph taken 23 Dec 2015 showing Part No. 3 significantly colonised by barnacles



Source: Schalk Lückhoff

Conclusions

At the time of writing, work was ongoing with respect to the marine ecology samples. The results from these tests will be provided to the Malaysian investigation team once complete. In terms of the identification of the two items of debris, it was concluded that:

• Part No. 3 was a Malaysia Airlines Boeing 777 engine cowling segment, almost certainly from the aircraft registered 9M-MRO.
• Part No. 4 was a Malaysia Airlines Boeing 777 panel segment from the main cabin, associated with the Door R1 closet, almost certainly from the aircraft registered 9M-MRO.

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Download PDF of the Debris report 2

Published: 15 September 2016 (amended 17 August 2017)

Debris examination – update No. 3

Identification of large flap section recovered off the Tanzanian coast

Introduction

On 20 June 2016, a large item of debris was found on the island of Pemba, off the coast of Tanzania. Preliminary identification from photographs indicated that the item was likely a section of Boeing 777 outboard flap (Figure 1).

Assistance from the Australian Transport Safety Bureau (ATSB) was requested by the Malaysian Government in the formal identification of the item, to determine if the item came from the Malaysia Airlines aircraft, registered 9M-MRO and operating as MH370. The Malaysian investigation team secured the item of debris and arranged shipping to the ATSB facilities in Canberra.

This document (Update 3) is a brief summary of the outcomes from the identification of the item, designated as Part number 5. It follows the identification of Part numbers 1 through 4, the outcomes of which were released by the ATSB in Updates 1 and 2, available on the ATSB website at www.atsb.gov.au/mh370.

This debris identification summary is released with the concurrence of the Malaysian ICAO Annex 13 Safety Investigation Team for MH370.

Identification

Part No. 5

Part number 5 was preliminarily identified from photographs as an inboard section of a Boeing 777 outboard flap. On arrival at the ATSB, several part numbers were immediately located on the debris that confirmed the preliminary identification. This was consistent with the physical appearance, dimensions and construction of the part.

A date stamp associated with one of the part numbers indicated manufacture on 23 January 2002 (Figure 2), which was consistent with the 31 May 2002 delivery date for 9M-MRO.

All of the identification stamps had a second “OL” number, in addition to the Boeing part number, that were unique identifiers relating to part construction. The Italian part manufacturer recovered build records for the numbers located on the part and confirmed that all of the numbers related to the same serial number outboard flap that was shipped to Boeing as line number 404. Aircraft line number 404 was delivered to Malaysia Airlines and registered as 9M-MRO.

Based on the above information, the part was confirmed as originating from the aircraft registered 9M-MRO and operating as MH370.

Figure 1: Inboard section of outboard flap (inverted)

Source: ATSB

Figure 2: Exemplar part number and date stamp

Source: ATSB

Further analysis

At the time of writing, the flap section was being examined for any evidence of interaction with mechanisms, supports and surrounding components (such as the flaperon, which abuts the inboard end of the outboard flap) that may indicate the state of flap operation at the time of separation from the wing. This information may contribute to an increased understanding of end of flight scenarios.

Conclusions

It was confirmed that Part No. 5 was the inboard section of a Boeing 777 right, outboard flap, originating from the Malaysia Airlines aircraft registered 9M-MRO.

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Download PDF of the Debris report 3

Published: 19 April 2016 (amended 17 August 2017)

Debris examination – update No. 1

Identification of two items of debris recovered in Mozambique

Introduction

On 27 December 2015 and 27 February 2016, two items of debris were independently found, approximately 220km apart, on the Mozambique coast. Both items were delivered to the relevant Civil Aviation Authorities in Mozambique and South Africa in early March 2016. Assistance from the Australian Transport Safety Bureau (ATSB) was requested by the Malaysian Government in the formal identification of the items to determine if they came from the Malaysia Airlines Boeing 777 aircraft, registered 9M-MRO, operating as MH370.

The parts were packaged in Mozambique and South Africa respectively and delivered safe-hand to the ATSB in their original packaging, in the custody of the ICAO Annex 13 Safety Investigation Team members.

The following is a brief summary of the outcomes from the debris examination. This debris examination summary is released with the concurrence of the Malaysian ICAO Annex 13 Safety Investigation Team for MH370.

Quarantine and marine ecology

On arrival into Australia, both parts were quarantined at the Geoscience Australia facility in Canberra. The parts were unwrapped and examined for the presence of marine ecology and remnants of biological material. Visible marine ecology was present on both parts and these items were removed and preserved. The parts were subsequently cleaned and released from quarantine.

Identification

Part No. 1

The first part was initially identified from a number stencilled on the part (676EB), as a segment from a Boeing 777 flap track fairing (Fairing No. 7) from the right wing (Figure 1). All measurable dimensions, materials, construction and other identifiable features conformed to the applicable Boeing drawings for the identified fairing.

The 676EB stencil font and colour was not original from manufacture, but instead conformed to that developed and used by Malaysia Airlines during painting operations (Figure 2). The part had been repainted, which was consistent with the operator’s maintenance records for 9M-MRO.

Figure 1: Location of flap track fairing panel No. 676EB

Source: Boeing 777 aircraft maintenance manual (modified by ATSB)

Figure 2: Flap fairing outer surface showing stencil location and comparison

Source: ATSB

Part No. 2

The second part was primarily identified from images showing the materials, construction and “NO STEP” stencil, as a segment of a Boeing 777 RH horizontal stabilizer panel (Figure 3). All measurable dimensions, materials, construction and other identifiable features conformed to the Boeing drawings for the stabiliser panel.

The part was marked on the upper surface in black paint with “NO STEP”. The font and location of the stencil were not original from manufacture, however the stencilling was consistent with that developed and used by Malaysia Airlines (Figure 4).

A single fastener was retained in the part. The fastener head markings identified it as being correct for use on the stabiliser panel assembly. The markings also identified the fastener manufacturer. That manufacturer’s fasteners were not used in current production, but did match the fasteners used in assembly of the aircraft next in the production line (405) to 9M-MRO (404) (Figure 4).

Figure 3: Location of horizontal stabiliser panel No. 3 upper

Source: Boeing 777 Parts Catalogue (modified by ATSB)

Figure 4: Stabiliser panel “NO STEP” stencil and fastener comparison

Source: ATSB, Boeing

Conclusions

At the time of writing, ongoing work was being conducted with respect to the marine ecology identification as well as testing of material samples. The results from these tests will be provided to the Malaysian investigation team once complete. Nevertheless, from the initial examination it was concluded that:

Part No. 1 was a flap track fairing segment, almost certainly from the Malaysia Airlines Boeing 777 aircraft, registered 9M-MRO.

Part No. 2 was a horizontal stabiliser panel segment, almost certainly from the Malaysia Airlines Boeing 777 aircraft, registered 9M-MRO.

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Download PDF of the Debris report 1