MH370 and Other Investigations

Introduction

In two previous posts, (here and here), we have presented the assumptions and analyses for reconstructing our best estimate for MH370’s path into the SIO. Often referred to as “UGIB” after its authors Bobby Ulich, Richard Godfrey, Victor Iannello, and Andrew Banks, the model was developed using exhaustive data sets and technical documentation available from both public and confidential sources, and includes:

• Radar data collected by military and civilian installations in Malaysia
• Timing and frequency measurements collected by the Inmarsat satellite network
• Aircraft performance data for Boeing 777-200ERs
• Historical performance data for airframe 9M-MRO
• Navigation and speed modes for automated flight
• Drift analysis of debris that floated and was recovered in East Africa
• Aerial search results from March and April 2014
• Weather data along the flight path

The work included the development of an accurate fuel consumption model, as well as a statistical metric for the expected random noise inherent in the recorded satellite data. These improvements allowed the rejection of hypothetical flight paths that were previously believed to be possible.

An important assumption of UGIB is that from 19:41 UTC until impact, MH370 flew with the autopilot and autothrottle engaged and with no pilot inputs. The results of that work suggest that the final hours of the flight were due south in the Indian Ocean along E93.7875° longitude, which matches a great circle between the waypoint BEDAX (about 100 NM west of Banda Aceh, Sumatra) and the South Pole. The Last Estimated Point (LEP) was defined as the intersection of E93.7875° longitude and the 7th arc, with coordinates S34.2342 E93.7875°. The debris field was postulated to be close to the LEP, as the end-of-flight after fuel exhaustion was expected to be a short distance.

The final BFO values at 00:19:29 UTC and 00:19:37 UTC suggest that MH370 was in an increasingly steep descent with a downward acceleration of around 0.7g. That, combined with the missing IFE log-on, are consistent with an impact relatively close to the 7th arc. Boeing simulations of the end-of-flight (assuming no pilot inputs) suggest an impact within 8 NM of the 7th arc. Other simulations with a PC-simulator in which a bank was imposed to match the BFO-derived downward acceleration suggest that the impact should be within 5 NM of the 7th arc. Yet, two subsea searches along the 7th arc near the latitude of 34°S, covering a much larger width of 110 km, failed to find the debris field.

The first search, conducted by GO Phoenix with a towfish, had a width of 40 km (7 km inside, 33 km outside the 7th arc) when scanning near 34°S latitude. Although this search failed, there were some areas that were missed due to terrain avoidance, shadows, equipment failures, and tracking errors, which does open the possibility that the debris field was passed over by GO Phoenix and not detected.

The second search was conducted by Ocean Infinity using a fleet of autonomous underwater vehicles (AUVs), and extended the width inside the 7th arc by 42 km and the width outside of the 7th arc by 29 km, for a cumulative search width of around 110 km (49 km inside, 61 km outside). Due to the greater maneuverability of the AUVs, the search area included some of the steep slopes that were deliberately avoided by GO Phoenix due to challenging terrain. Despite this wider and more thorough search, the debris field again was not found.

In a previous article, we postulated that the debris field may have been missed due to terrain avoidance and/or shadows, or detected but not properly interpreted by reviewers. In particular, there is a steep slope that lies about 33 km due south of the LEP and 27 km from the 7th arc that was not scanned by the GO Phoenix’s towfish and appeared to have been only partially scanned by Ocean Infinity’s AUVs.

The figure below shows the ocean depth along a line of constant longitude in the vicinity of the LEP. The previously identified steep slope to the south of the LEP has a grade of about 30%. To the north, another slope has a grade of 44%. The slope to the north was beyond the limits of the search boundaries of GO Phoenix, but was scanned by Seabed Constructor’s AUVs, so we focus on the steep slope to the south.

New Information about the Previous Search

Working with Ocean Infinity, we were able to obtain a more accurate outline of the area searched with their team of AUVs. The outline is shown by the four yellow lines in the figure below. As shown in the figure, the two inner yellow lines show the approximate limits of the GO Phoenix search area, and the outer lines show the limits of the Ocean Infinity search area. Also shown in the figure are olive-green areas which represent areas that were not scanned by GO Phoenix’s towfish due to steep terrain. These and other areas of missing or low-quality data were made available by Geoscience Australia.

Looking again at the steep slope to the south of the LEP that we previously suspected was not fully scanned, we can see that our suspicions were correct. The portion of the steep slope that was not scanned by the GO Phoenix towfish is about 60.3 km². Of this, about half was later scanned by Ocean Infinity AUVs, leaving about 30.5 km² of seabed surrounding S34.53° E93.84° that was never scanned. We designate this area as a “High Priority Search Area”.

The figure below is a closer view of the High Priority Search Area and surrounding terrain.

Discussion

Ocean Infinity has expressed a desire to resume the subsea search for MH370 in the Southern Indian Ocean (SIO), hopefully during the next austral summer that begins this December. As the a) final BFO values, b) the lack of IFE log-on, and c) the end-of-flight simulations all suggest an impact close to the 7th arc, a high priority should be to scan the areas closest to the 7th arc that were either never scanned or have low quality data before searching new areas further from the 7th arc. However, with pilot inputs, it is possible that MH370 glided after fuel exhaustion beyond the areas that were previously scanned. Therefore, searching wider along the 7th arc should also be part of the search plan if areas closer to the 7th arc are unsuccessful in locating the debris field.

The reconstructed route of MH370 proposed by UGIB remains a leading candidate for the hypothetical route to the SIO because of the accuracy of the physical models, the breadth of the data sets analyzed, and the statistical rigor applied to the BTO and BFO data. The analysis does assume there were no pilot inputs after 19:41 UTC, and the autopilot and autothrottle were engaged until fuel exhaustion. A steep slope to the south of where UGIB predicts MH370 crossed the 7th arc happens to lie along the extended path of the reconstructed route, and much of this slope remains unscanned. For this reason, the unscanned area surrounding S34.52 E93.84 should be designated a High Priority Search Area.

Acknowledgement

I’d like to thank Ocean Infinity for their help in defining the geographic boundary of their subsea search for MH370. I’d also like to thank Don Thompson for his help in GIS file format conversions.

According to a report released by Blaine Gibson and Richard Godfrey, another item has been recovered from a beach in Madagascar, and that part is similar in appearance and discovery location to parts that are from MH370. The new part is believed to have washed ashore in March 2017 and was discovered by a local fisherman at that time, but was unknown to the public until recently.

In a recent blog post that summarizes the finding of the report, Godfrey claims the debris item is likely the remnant of the left main landing gear trunnion door. In this article, we show that we can be very confident that the new debris is NOT a trunnion door.

Misidentification of the New Debris

In a short technical note, MH370 Independent Group (IG) members Mike Exner, Don Thompson, Tom Kenyon, and I show why the new debris cannot be the trunnion door. To determine the approximate size of the trunnion door, we first examine a photo of the underside of a Boeing 777 in which the trunnion door can be seen. Then, using the known wing span of the B777 as a scaling reference, we can determine the approximate dimensions of the trunnion door, which are shown in the figure.

Next, we observe that the trunnion door is attached to the landing gear mechanisms by two brackets, each requiring four fasteners, as shown in this figure. That allows us to determine the position of where we would expect to see through holes through the new debris if indeed it is the trunnion door.

Finally, we compare the debris depicted in Gibson and Godfrey’s report with an outline of the trunnion door, and note that there are no through holes for fasteners in the locations expected. Nor do the dimensions of the new debris match the outline of the trunnion door.

Another piece of evidence that weighs against identification as the trunnion door is the color of the paint, which is white. As Bobby Ulich says in a recent blog comment, the B777s that were operated by Malaysian Air at that time had undersides that were painted grey, not white, as seen in the next photo of 9M-MRO. Although the grey paint might have faded, other debris from MH370 that was previously recovered had identifiable paint such as livery colors and text lettering, so there is only a very small possibility that none of the grey paint would be recognizable.

Cannot Determine Landing Gear Position

There are four parallel, penetrating, narrow cuts on the new debris in which the penetrating objects appear to have entered on the interior surface of the debris and exited from the exterior, white surface. Gibson and Godfrey propose that the cuts could have been caused by rotating engine parts that separated from a disintegrating engine upon impact with the ocean. Whatever the cause of the cuts, the authors believe the damage is consistent with the main landing gear that is lowered based on the direction that the penetrating objects entered and exited the debris.

We’ve already shown that the new debris is not the trunnion door, nor is it any other part of a landing gear door, so it is not possible to surmise the position of the landing gear based on the damage to the new debris. Even if the new debris was part of one of the landing gear doors, there is no reason to believe a rotating engine part caused the damage. Components on one of the shaft assemblies in the engines would tend to fly radially outward from the engine. Yet, the landing gear doors are located aft of the engines, which are positioned forward of the wings, which means the landing gear doors are not along a projectile path. Also, when the landing gear is extended, the exterior surfaces of the doors, not the interior surfaces, are facing the engine.

Lowering the Landing Gear Does Not Increase Damage

Gibson and Godfrey propose that the landing gear might have been lowered to cause a high-speed impact designed to break up the aircraft and sink the aircraft as fast as possible to hide the evidence of the crash. However, this is not consistent with maximizing the kinetic energy of the impact, as lowering the landing gear would add drag, and could limit the attainable airspeed. After fuel exhaustion, the flight control mode would degrade from NORMAL to SECONDARY, and there would be no envelope protection that would prevent an overspeed of the aircraft. The pilot flying would only need to lower the nose by pushing forward on the yoke to ensure the aircraft would shatter upon impact.

Conclusion

The new debris recovered from Madagascar may eventually prove to have probative value. However, the debris is not part of a trunnion door from the main landing gear, nor can the debris provide any insights into the position of the landing gear when the aircraft impacted the ocean. Work continues to identify the debris and to determine any new clues about the disappearance of MH370.

Acknowledgement: This article benefited from discussions with and suggested edits from Mike Exner, Don Thompson, and Tom Kenyon.

Update 1 on February 1, 2023

Based on the construction of the composite layers, Don Thompson, Mike Exner, and other contributors to this blog believe that the new debris is more likely from the racing yacht Vestas Wind rather than from a Boeing 777. Vestas ran aground near Cargados Carajos Shoals in November 2014, and one or more pieces may have separated and floated to Madagascar.

Godfrey refutes this, and now claims that “a closer examination of the recent debris find in Madagascar proves that it is from a Boeing aircraft and cannot be from marine provenance. The key difference is the lightning protection system used on Boeing aircraft with composite materials, which is fundamentally different to the lightning protection system used in marine applications with composite materials. ” Godfrey offers this close-up photo, which he believes shows an aluminum mesh that offered lightning protection for MH370. He believes the mesh was supplied by Dexmet.

Don Thompson refutes the claim that the mesh is related to lightning protection, a dubious claim that was regurgitated by Geoffrey Thomas at airlineratings.com. Don says:

The material highlighted in the photographs referred by the Gibson-Godfrey paper, and ensuing comments from the second author is not an LSP [lightning strike protection] layer; rather, it is a ‘media flow’ layer necessary on the ‘bag’ side of the composite lay-up in a resin-infusion process. That is, the resin-infusion process used by the constructor of the V065 yacht hull, its internal bulkheads and interior decks.

It’s important to understand that an LSP layer will lie immediately under the surface finish on the external face of a panel/structure as any intermediate CFRP (or GFRP) layers will form an (electrical) isolation layer.

Further, the aggregate mix surface coating that is evident in further photographs referred by the second author, and has been argued as somehow typical of B777 panels where surface protection may be necessary, is also evident on decking in video clips that document the rebuild of the seven VO65 yachts ready as they were prepared for the 2017-2018 Volvo Ocean Race. It is a common deck surface coating manufactured by Akzo Nobel/International.

Also, consider the comments from a retired, senior Boeing design engineer whose role afforded him extensive and detailed knowledge of Boeing’s composite fabrication techniques on the B777. For example: that the orientation of CFRP tape tows on the exposed side of the panel is alien to the techniques specified for the B777; that the combination of CFRP fabrication and the panel’s thickness is also alien to a B777’s construction.

The claim that this piece of flotsam originates from 9M-MRO, or any Boeing 777, is demonstrably false. Demonstrably, from the very features evident in the many images shared by the authors of the Dec 12th paper in support of their conclusion for the origin of the piece of flotsam.

The further claim that oceanographic drift studies discount this piece of flotsam originating from the Cargados Carajos Shoals in Nov-Dec 2014 before its alleged recovery from a beach near Antsiraka, Madagascar, is also demonstrably false. That assertion is false because the piece of flotsam did originate its drift, after its separation from ‘Vestas Wind’, at the Cargados Carajos Shoals on Nov 29, 2014, or within the few weeks before the yacht was salvaged and removed. How many times it beached, lay stranded, and washed out to sea again through the cycle of seasonal tides and storms is unknown, as is its final beaching and recovery time, thus rendering drift predictions irrelevant.

So, we now know that the new debris is not part of a trunnion door from the main landing gear, nor can the debris provide any insights into the position of the landing gear when the aircraft impacted the ocean. The new debris is almost certainly not from a Boeing 777, and is very likely from the Team Vestas Wind racing yacht that ran aground in the Cargados Carajos Shoals in November 2014.

Facts are stubborn things.

Update 2 on February 7, 2023

In light of the strong evidence that the new debris is from the Vestas Wind yacht that ran aground in the Cargados Carajos Shoals on November 29, 2014, I thought it would be instructive to study the path of debris that might have broken free of Vestas Wind from the accident.

To study the path of debris, I used the drift results generated by CSIRO’s David Griffin, PhD, that were created for studying how debris from MH370 drifted from hypothetical impact points along the 7th arc. In particular, I used the results of the BRAN2015 model for “generic” debris, i.e., debris that was subjected to “Stoke’s Drift”, modeled as 1.2% of the wind, but with no additional leeway drift. This is appropriate for the floating debris such as the flat panel recovered from Vestas Wind. In CSIRO’s drift simulation, 86,400 “trials” (virtual particles) were injected along the 7th arc on March 8, 2014, and the paths of these particles are tracked. Luckily, 204 of those trials passed within 100 km of the Vestas Wind accident site on November 29, 2014, so the path of those trials after that date should approximate parts of Vestas Wind that separated on that date.

In particular, I studied the timing of debris that beached on the shores of Madagascar, where a trial was classified as beached if there was negligible movement over the course of three days. Of the 204 trials, 61 trials (30%) eventually beached on the Madagascar coast. The following video shows the simulated paths of the debris originating from Vestas Wind:

Based on this simulation, we make the following observations:

• The first debris from Vestas Wind would reach the beaches of Madagascar in February 2015, less than 3 months from the time of the accident.
• Of the debris beaching on Madagascar, more than half would arrive before May 2015, around 5 months from the time of the accident.
• Very few debris would arrive after August 2015, around 9 months from the time of the accident. (The simulation ended on December 29, 2016.)

Any debris that was recovered in 2016 or later likely beached at an earlier time (likely between February and August of 2015), was swept out to sea, and then beached another time at a later date. This is likely what occurred for the new debris described by Gibson and Godfrey.

As Don Thompson noted in a private communication, tropical cyclone Enawo made landfall on Madagascar March 7, 2017, and the storm surge caused major flooding along the coast. The European Commission’s Joint Research Center published an extensive report on the storm, including the damage, as well as the number of people that were injured, missing, or died. A satellite image of the cyclone over Madagascar from that report is show below.

This tropical cyclone likely was responsible for the debris from Vestas Wind beaching on the coast of Madagascar in March 2017.

In the last blog article, I explained in simple technical terms why WSPR data cannot be used to track aircraft over long distances, and certainly cannot be used to reconstruct the flight path of MH370. The article concluded:

At long distances and at low transmission powers, the received signals from hypothetical aircraft scatter are simply too weak by many orders of magnitude. What is claimed to be discernable “anomalies” in signal strength attributable to forward scatter by aircraft are within the expected deviations in signal strength for long distance skywave propagation involving refraction off the ionosphere. Although aircraft scatter could be detected if the aircraft were close to either the transmitter or receiver and if the transmitted power were sufficiently strong, the detection of the aircraft requires signal processing to separate the Doppler-shifted scattered signal from the much stronger direct signal, and this data is not available in the WSPR database.

Since publishing that article, even more evidence supporting these conclusions was presented by me and other contributors in 667 blog comments, which include analyses of experimental data of HF scatter off of aircraft, and statistical analyses of the WSPR-tracking claims. I considered writing a new blog article with the updated results, but reasoned that the informed already understood that WSPR-tracking was junk science, the uninformed wouldn’t appreciate the significance of the new results, and the WSPR proponents were too dug in to do anything but continue to double down on their flawed theory.

A question often asked is “How were aircraft successfully tracked in validation tests?” Those that have studied the tests respond that the tests were not scientifically rigorous, and the positive results simply reflect the biases of the WSPR proponents, i.e., the data were cherry-picked to support the claims that historical WSPR data could be used to track aircraft.

One of the participants in the validation tests was Mike Glynn, who was an airline captain for Qantas. Mike has commented on the blog that he now agrees that the validation tests he helped conduct were not scientific. I repeat his comment below in its entirety and without edits:

Having just read this thread it’s appropriate that I comment on a couple of things.

My involvement with RG goes back to learning that he was after an appropriate flight to test his method of detecting aircraft via WSPR. I was in possession of a candidate plan, which happened to be my final flight in Qantas, although I was not aware of that fact at the time.

The flight was a ferry of a 747 with an oil leak in the number 4 engine which could not be repaired in Johannesburg and had to be flown, empty, to Sydney.

I had experience in post-maintenance air-tests in the 747 and this was considered desirable by QF.

The flight was planned overhead Perth and Adelaide then direct to Sydney, and due to the unusual routing, I thought it may have been a suitable candidate for a test of WSPR.

The kick in the tail was that we only got as far as Perth due to the oil leak accelerating during the flight and we diverted to Perth and landed with the engine still running, with the oil quantity indication bouncing off zero, but still with sufficient oil pressure to keep the EICAS quiet.

So, I contacted RG and the test went ahead. The test was not a success. RG initially appeared to be tracking the aircraft till it crossed the African coast, although there was a cross-track error of 20NM or so. He eventually reported that the aircraft had landed in Melbourne.

This was obviously incorrect, but he had been making some wrong assumptions regarding the aircraft type, weight and tracking and so we decided on another test which was a flight plan of a QFA330 from Apia to Adelaide.

I supplied RG with the details of the flight including weight, type and time of departure. We had done a search of most flight-trackers and the flight was not on the sites we checked. Only after the analysis was complete did we find a site which had the flight recorded; however, I do not believe RG found and used this site.

An informational error on my part at the beginning of the plan meant RG turned the aircraft the shortest way towards Australia (to the Right) after take-off, however there is a procedure for departures on RWY 08 at APIA to turn left due to terrain. RG had stated that WSPR does not supply a direction of turns so I accepted the error at the start of the plan due to the incorrect turn.

After a couple of days RG informed me that the flight was tracking to Brisbane.

We were preparing to stop the test at that point but the following day he stated that the aircraft was tracking to Sydney and the following day he stated that the aircraft had flown to Adelaide from overhead Sydney and landed there.

This was correct; however, no documentation was given to me to substantiate how he had arrived at this conclusion.

Considering the process so far, I wanted to do another test and had another one, an A380 flight from Sydney to an Asian port, ready to go.

RG declined another test as he wanted to start on the MH370 analysis. I wasn’t happy with this, but it was his decision.

However, my opinion remains that the test process was not scientific.

When RG produced his MH370 analysis it made little sense to me as an airline pilot. The track to the north of Sumatra is very irregular and I found it difficult to reconcile it to anything an airliner would fly.

I had not heard of the “loiter” hypothesis either, so the holding pattern was new to me.

I asked RG whether he had considered the weather in the area in his analysis and he said he hadn’t. Despite comments made about the weather analysis on this thread, the results make sense to me as an airline pilot, particularly the diversion away from the thunderstorms off the south coast of Sumatra.

Recently, however, I have revisited the WSPR track analysis. My knowledge of the characteristics and limitations of WSPR is basic, and I simply don’t have the appropriate background to comment on that with any authority.

However, as a former RAAF pilot, I was trained in the principles of radio navigation and off-airways navigation. Andrew Banks arrived at my squadron just as I was leaving and was trained in the same techniques.

In my opinion, the methodology used in the construction of the WSPR track does not conform to any known principles of aircraft navigation that I am aware of.

It is arbitrary in the extreme and, I believe, constructed only to satisfy the constraints of the only solid data available, the BTO and BFO data.

I realise now that I should have looked at this earlier. and avoided looking as if the construction of this track makes any sense from an aviation POV.

Thats my error.

I will be explaining why I believe this in due course.

Thank you for your time and understanding.

Mike

Perhaps this is a positive step towards a more scientific discussion of the flaws in using historical WSPR data to track aircraft.

“I do not believe that historical data from the WSPR network can provide any information useful for aircraft tracking.”

Prof. Joe Taylor (K1JT), Nobel Prize in Physics, Inventor of WSPR

Despite many stories in the media repeating claims that historical WSPR data can be used to track MH370, there are many reasons why these claims are patently false. There is broad agreement among acknowledgeable researchers that have investigated these claims, and a handful of these researchers have documented their concerns. For instance, amateur radio enthusiast Hayden Haywood (VK7HH) has created a video explaining why, in simple terms, WSPR can’t track airplanes. MH370 investigator Steve Kent published a paper that formally treats skywave propagation and scatter off airplanes, and concludes there is insufficient signal strength (by many orders of magnitude) for WSPR to detect aircraft over long distances. In fact, even WSPR creator Joe Taylor (K1JT), who won a Nobel prize in physics for his research on pulsars and gravity, told fellow MH370 Independent Group (IG) member Mike Exner, “I do not believe that historical data from the WSPR network can provide any information useful for aircraft tracking.”

WSPR Background

WSPR (pronounced “whisper”) is an acronym for “Weak Signal Propagation Reporter”. Amateur radio stations implementing WSPR send and receive messages using low-power transmissions to test propagation paths on the Low Frequency (LF), Medium Frequency (MF), High Frequency (HF), and Very High Frequency (VHF) amateur radio bands. When a participating station successfully decodes the transmission transmitted by another participating station, it sends that information to a central database, and that information is available to the public for retrieval. For each 110-second contact between stations (“spots”), the available information includes station call signs, locations, transmitted power, and three parameters discriminated by the receiver: signal-to-noise ratio (S/N), frequency, and frequency drift. The proposed theory is that recorded deviations (“anomalies”) in the (S/N) and the frequency shifts/drifts are related to radio wave interactions with aircraft some thousands of kilometers distant from either amateur radio station.

The theory behind using bi-static radar (i.e., transmitter and receiver in different locations) for aircraft detection and tracking is well-known, and books (e.g., this) have been written on this subject. A special case is when an aircraft crosses the “baseline” between transmitter and receiver, resulting in a “forward scattered” signal caused by the diffraction around the silhouette (projected area) of the aircraft. The Forward Scatter Radar Cross Section (FSRCS) is typically much larger than the RCS that conventional mono-static radar uses to detect targets. It is this forward scattered signal that is of interest here in evaluating whether WSPR signals can be used to reconstruct the path of MH370.

In this article we apply the well-developed theory of bi-static radar to demonstrate that WSPR signals cannot be used to detect MH370 in the manner claimed in this paper. The relevant equations are presented in the Appendix, and the inputs and the calculational results for the test cases can be found in the accompanying table in the Appendix.

Detection of MH370 Before Radar Coverage Was Lost

We consider the claim that the WSPR data shows that MH370 was detected on the night of the disappearance at 17:16 UTC when it was still under radar coverage as it flew over the Gulf of Thailand towards waypoint IGARI, before the turnback, at FL350 (37,200 ft). At that time, a WSPR transmission from a station in Switzerland (HB9CZF) was received by an Australian station near Canberra (VK1CH) over a distance of 16,527 km on 14.097 MHz at a transmitted power of 1 W. The distance from the Swiss transmitter to the aircraft was 9,868 km and the distance from the aircraft to the receiver was 6,660 km, as depicted in this figure from the paper:

Although WSPR contacts greater than 16,000 km are rare, this spot shows they can indeed occur. Based on the distance between the stations, the transmission from Switzerland reached the Australian station via skywave propagation in which the radio waves were refracted off the ionosphere and reflected off the Earth’s surface (“hops”) about 5 times.

WSPR Signals Forward Scattered from an Aircraft Would be Undetectable at Long Distances

The column labeled “Case 1” from table in the Appendix shows the inputs and the calculational results for this scenario. Assuming that the propagation loss is the same as for free-space propagation, the expected strength of the direct signal at the receiver is -110 dBm, which is about the same value claimed in the paper when considering hops between the ionosphere and the Earth’s surface. This suggests that the refraction and reflection losses were either calculated to be very small, or were neglected.

At 14.097 MHz, the wavelength is 21.3 m, and the FSRCS for the B777-200ER for waves directly incident to the top or bottom is estimated to be 18,791 m², or about 23 times the projected area. The forward scattered signal at the receiver is estimated to be -210 dBm, or about 100 dB (10 orders of magnitude) weaker than the direct signal. Can a signal of this strength be detected and decoded by the WSPR software?

Whether the signal could be detected by the radio and decoded by the software depends on the achievable noise level, as a minimum signal-to-noise ratio (S/N) of around -30 db is required by the WSPR software, where the noise level is referenced to a bandwidth of 2.5 kHz. I ran some simple experiments on my Flex 6400 amateur radio to measure the achievable noise level on the 20-meter band at my home in suburban Roanoke, Virginia. At 10:30 am on December 19, 2021, on a quiet part of the band, when connected to a horizontal resonant antenna, and after setting the bandwidth to 2.5 kHz, I measured a noise floor of -102 dBm. This largely consists of manmade and natural noise received at the antenna. To determine the sensitivity of the radio independent of the environmental noise, I disconnected the antenna and connected the radio to a resistive dummy load of 50 ohms. The noise level dropped to -105 dBm. By using the radio’s built-in pre-amplifier configured for its maximum gain of 32 dB, the noise level further dropped to -129 dBm. (Pre-amplification improves sensitivity but increases the distortion from strong signals, and so must be used judiciously.) Even though this noise level would be very difficult to achieve under real conditions, I used this noise level as the reference for calculating (S/N) values on 20 meters.

So, for the forward scattered signal strength of -210 dBm, the (S/N) would be (-210 – -129) = -81 dB. This is 51 dB weaker than WSPR requires (-30 dB), i.e., the forward scattered signal is 5 orders of magnitude too weak to be detected and decoded by WSPR! Considering the very favorable assumptions we made regarding propagation loss, incident angle, and noise floor, we can be quite confident that the WSPR signal originating in Switzerland at 17:16 UTC did not interact with MH370 in any way that was detectable in Australia, as was claimed.

WSPR Signals Forward Scattered by an Aircraft Would Be Masked by the Stronger Direct Signal

Assuming the skywave propagation loss was equal to the free-space propagation loss, the WSPR signals originating in Switzerland and forward scattered by MH370 over the Gulf of Thailand would be received in Australia with a strength of around -210 dBm. However, the direct radio waves that did not interact with the aircraft would be received with a strength of around -110 dBm. That means that the direct signal strength would be about (-110 – -210) = 100 db (10 orders of magnitude!) stronger than the scattered signal. Under these circumstances, the combined signal (direct plus forward scattered) would be absolutely indistinguishable from the direct signal, even if above the noise level (which it was not).

However, the equations presented in Appendix A predict that it IS possible for radio waves to forward scatter from an aircraft and be detected under the right conditions. For example, Joki et al. studied how broadcast TV transmissions at around 50 MHz may be passively used to detect, identify, and track airliners over a distance of hundreds of kilometers. Some of the factors that determine whether the aircraft could be detected include:

• The projected area of the aircraft
• Strength of the direct signal received, i.e., high power transmitters near the receiver increase the signal strength
• The distance of the aircraft to the receiver, i.e., the proximity of the aircraft increases the strength of the forward scattered signal
• The frequency of the transmission, higher frequencies increase the FSRCS and therefore the strength of the forward scattered signal
• Frequency-based signal processing to separate the direct signal from the Doppler-shifted forward scattered signal

Recently, amateur radio operator Nils Schiffhauer (DK8OK) claims to have observed aircraft scatter by analyzing the signal from an AM broadcast of China Radio International (CRI), which operates on 17.530 MHz with a 250 kW carrier, and uses a beam antenna with a gain of 25 dBi towards Europe. Nils’ location is near Hannover Airport in Germany, some 7,600 km away from the CRI transmitter in Xianyang, China. The figure below depicts a “waterfall” plot showing aircraft scatter over a period of 3 hours. The Doppler-shifted signals from many aircraft are clearly visible in the lower sideband (LSB), some 5 to 20 Hz below the carrier frequency.

After processing the data from a 1-hour measurement, Nils calculated that the carrier strength was -59.1 dBm, the average Doppler signal strength was -105.9 dBm, and the average noise level was -108 dBm.

I was curious if the forward scatter equations in Appendix A would produce calculational results consistent with Nils’ measurements. After using FlightRadar24 to observe flights passing near his residence, I estimated that planes landing on Hannover Airport’s Runway 27R would generally pass within a lateral distance of about 2 km and about 0.85 km (2800 ft) above his residence, which is a slant range of about 2.2 km . A good number of those airplanes were B737s, which I used to calculate the FSRCS. The inputs and the results from the calculations are shown in the column labeled “Case 2” from the table in Appendix.

We know the location, power, and antenna gain of the transmitter, and since we know the received strength of the carrier was -59 dBm, we can calculate the additional propagational loss of the skywave path due to refractions from the ionosphere and reflections from the Earth’s surface, which we estimate to be around -33 dB. The signal strength of the aircraft scatter is then calculated to be around -102 dBm, which is only 4 dB stronger than the measured value of -106 dBm. Considering that the value of FSRCS is assumed to be in the most favorable direction, the measured strength of the aircraft scatter is entirely consistent with the calculated value.

Nils concludes that since the signal from the aircraft scatter is 47 dB below the carrier, it would be impossible to look at the combined signal (which is all that is available in the WSPR database) and determine the contribution of the aircraft scatter. We strongly agree.

WSPR Signal Deviations are Not Related to Aircraft

Based on the extremely small signal generated by a hypothetical interaction with MH370 at 17:16 UTC, there can be little doubt that at that time, the WSPR database did not record a spot between Swiss and Australian stations consistent with forward scatter from the aircraft.

Yet it’s claimed that there was a detectable deviation in the recorded (S/N) values between the Swiss and Australian stations that is indicative of forward scatter from MH370. To evaluate this claim, Mike Exner and Bobby Ulich produced the following graph which shows the (S/N) for all WSPR contacts between the Swiss (HB9CZF) and Australian (VK1CH) stations over an time interval of around 16 hours. The particular (red) spot deemed as “anomalous” clearly shows no greater deviation from the trend than any other spot. What is claimed to be “anomalous” is within the scatter range of the other points. The dynamic characteristic of the ionosphere is all that is needed to explain these deviations.

To further demonstrate that there is nothing anomalous about the spot at 17:16 UTC, Mike and Bobby produced the following graphs which show that the reported values of frequency and frequency drift at 17:16 UTC are in no way anomalous to the other values recorded on that day for HB9CZF-VK1CH WSPR contacts.

Conclusions

This article attempts to lay out in simple technical terms why WSPR data cannot be used to track aircraft over long distances, and certainly cannot be used to reconstruct the flight path of MH370. At long distances and at low transmission powers, the received signals from hypothetical aircraft scatter are simply too weak by many orders of magnitude. What is claimed to be discernable “anomalies” in signal strength attributable to forward scatter by aircraft are within the expected deviations in signal strength for long distance skywave propagation involving refraction off the ionosphere. Although aircraft scatter could be detected if the aircraft were close to either the transmitter or receiver and if the transmitted power were sufficiently strong, the detection of the aircraft requires signal processing to separate the Doppler-shifted scattered signal from the much stronger direct signal, and this data is not available in the WSPR database.

Acknowledgements

This article benefited from many private communications with Mike Exner, Don Thompson, Bobby Ulich, Steve Kent, Nils Schiffhauer, John Moore, and Ed Anderson. I also acknowledge the many insightful blog comments from Mick Gilbert, Sid Bennett, and @George G.

Update on December 22, 2021

I asked Joe Taylor for a comment on the material covered in this article. Here was his response, shared with his permission:

As I’ve written several times before, it’s crazy to think that historical WSPR data could be used to track the course of ill-fated flight MH370. Or, for that matter, any other aircraft flight…

I don’t choose to waste my time arguing with pseudo-scientists who don’t understand what they are doing.

Appendix: Equations and Table of Results

where the variable definitions and the inputs and results for the two cases can be found in the table below:

Reference: Passive Radar Technology, Prof. Christopher Baker, University of Birmingham, NATO STO-EN-243-02.

A source has disclosed that an Italian satellite that is part of the COSMO-SkyMed constellation detected three floating objects on March 21, 2014, near where MH370 is believed to have crashed in the Southern Indian Ocean on March 8, 2014. This information was never publicly released.

The three floating objects were detected at 34.9519°S, 91.6833°E; 34.5742°S, 91.8689°E; and 34.7469°S, 92.1725°E.

The detections are significant because we know that a French satellite that is part of the Pleiades constellation detected what appears to be man-made floating debris on March 23, 2014, only 35 NM from where the Italian satellite had detected floating debris two days earlier. The French Military Intelligence Service shared four proximate images from Pleiades 1A with Geoscience Australia (GA) in March 2017, which then performed detailed analyses and determined that a cluster of nine objects that are probably man-made appear in one of the images near 34.5°S, 91.3°E. Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) then used this position information along with advanced ocean drift models to calculate the most likely point of impact (POI) to be 35.6°S, 92.8°E.

There is no definitive proof that either satellite detected floating debris from MH370. Our source also could not definitively state that there were no other floating objects detected near the 7th arc by these two satellites. However, the source believes that if there were other objects detected, they would have been shared with the MH370 search team.

The two satellites used different physical principles for detecting floating objects. The Pleiades satellite used optical sensors to capture images in multiple bands of color to achieve a pixel size of 0.5 m x 0.5 m. On the other hand, the COSMO-SkyMed satellites use Synthetic Aperture Radar (SAR) sensors to continuously scan the earth’s surface. Unfortunately, COSMO only obtained a wide-angle, low-resolution capture of the objects. On a subsequent satellite pass, attempts to capture the objects at high resolution were not successful.

Prior to 2014, researchers had already investigated using satellite SAR data to detect floating debris. For instance, in 2011, using SAR data from the crash of Air France 447 off the coast of Brazil in 2009, researchers presented a numerical method for processing the SAR data from COSMO-SkyMed to detect floating metallic objects. (HT Don Thompson.) Likely, those who have analyzed the COSMO data from March 2014 would know if the detected objects are metallic.

To determine if the objects detected by Pleiades and COSMO-SkyMed were from a common source, we used the results of a complex drift model (BRAN2015) developed by CSIRO and shared by oceanographer David Griffin. The results include the trajectories of 86,400 virtual drifters, representative of generic debris sitting flat on the surface. The virtual drifters start along the 7th arc on March 8, 2014, between latitudes 8°S and 44°S, and the trajectories are tracked for 1000 days. Our method was to find the two virtual drifters that best match the position and timing of the detections from the the two satellites. If those two virtual drifters started from nearby locations on March 8, likely the objects detected by the satellites came from a common source.

The results from the drift analysis are shown in the figure below. The yellow circles show the path of the virtual drifter that passed closest to the COSMO objects on March 21. The red circles show the path of the virtual drifter that passed closest to the Pleiades objects on March 23. These two virtual drifters start within 3.5 NM of each other on March 8, near to 35.4°S, 92.8°E. The proximity of the starting positions is consistent with a common source for the objects detected by the two satellites. That position is about 83 NM to the southwest of where a previous study estimated that MH370 crossed the 7th arc, and within the 140 NM radius recommended to search.

In order to better estimate the likelihood that these objects were from MH370, we pose the following questions:

1. Were there other detections of floating objects along the 7th arc by Pleiades, COSMO-SkyMed, or any other satellites?
2. Were the COSMO-SkyMed detections on March 21 determined to be metallic objects?
3. Exactly what areas along the 7th arc were surveilled by Pleiades, COSMO-SkyMed, or any other satellites?
4. Will Airbus (the operator of the Pleiades satellites) provide the images for each color band so that independent researchers can analyze the raw data? (HT Bobby Ulich)

I recently submitted a FOIA request to the FBI for all documents related to MH370, which disappeared more than seven years ago. Yesterday, the FBI responded that the request was denied due to “a pending or prospective law enforcement proceeding”. This is identical to the response I received two years ago after I submitted a similar request. It implies the US intelligence community has relevant material that it will not release due to an open criminal investigation.

The FOIA request was one last attempt to obtain more information about MH370.

Independent investigators continue to use the data already in the public domain to guide future search efforts to find the debris field in the Southern Indian Ocean (SIO). Notably, Bobby Ulich continues to lead an effort that uses the timing and location of recovered debris, combined with CSIRO’s drift model results, to assess the most likely point of impact (POI), including uncertainty estimates of that position.

However, there exists other evidence not yet released that could aid researchers in localizing the POI:

• All of the Malaysian military radar data.
• Radar data from other sources, including the Singapore radar source operating in the vicinity of the Andaman Sea.
• Existing subsea sonar data from Ocean Infinity to determine precisely what areas were searched and which areas have low quality or missing data due to steep terrain, sonar shadows, or equipment anomalies.
• Any probative evidence discovered by the French judicial investigation.
• Unpublished debris analysis, e.g., spoiler and vortex generator baseplate. (HT Mike Exner)
• Boeing’s participation in detailed fuel calculations to confirm that our fuel models, which were used to help determine the southern-most limit of the POI, are accurate. Those models must include the effects of non-standard atmospheric temperatures and turning off the extraction of bleed air used to pressurize the cabin.
• NTSB flight data and Inmarsat satellite data that were used by Australia’s DSTG to investigate the measurement error in recorded BTO and BFO values. (HT Don Thompson)

We are nearing the end of what is left to analyze that can realistically help us find the debris field in the SIO. Unless new data or insights are publicly released, there is not much more that the analysts can add to our understanding of the disappearance.

On the 7th anniversary of the disappearance of MH370, members of the MH370 Independent Group have released separate reports that analyze two wing parts that have been recovered from East Africa. The two parts represent the first and most recent pieces of MH370 that have been found. Both reports conclude that the flight likely ended in a high speed descent.

The first report, authored by Tom Kenyon, is the culmination of several years of work of structural analysis of the right flaperon that was recovered from Reunion Island in July 2015. After performing a Finite Element Analysis (FEA) on a numerical model of the flaperon and reviewing photographs of the damaged part, Tom believes that the damage on the part is not consistent with damage expected if the flaperon was attached to the wing as it impacted water. Rather, the damage to the two hinge attachments is consistent with high cycle fatigue from torsional flutter, which likely led to separation from the aircraft while still airborne. Based on Tom’s review of simulations of uncontrolled descents for the B777, he concludes the expected airspeeds are well beyond design limits that lead to flutter and structural failure.

The second report, authored by Mike Exner and Don Thompson, analyzes a part that was recovered from Jeffreys Bay, South Africa, in August 2020. Based on an evaluation of features and markings, the authors positively identify the part as either spoiler #8 or spoiler #9 from the right wing from a Boeing 777, and by extension, almost certainly from MH370.

The authors observe that the spoiler detached at structures that attach the spoiler to the rear spar of the right wing. The fracture along a chord line is consistent with bending of the spar along the span of the wing. At high airspeeds, wings dynamically flex due to flutter, and the dynamic aeroelastic loads that are induced will rapidly grow until the wing structurally fails.

A visualization of wing flutter can be seen in this video of a scaled model of a B747 in a wind tunnel.

The high speed descent theorized in both reports is consistent with the final BFO values recorded by the Inmarsat Ground Earth Station (GES) on March 8, 2014, at 00:19z. Those values suggest the plane was in a 0.7g downward acceleration. Without inputs from a skilled pilot, the aircraft would have impacted the ocean shortly after reaching this condition, which would mean the debris field on the seabed is relatively close to the 7th arc.

Today, the Indonesian transportation authority KNKT released a Preliminary Report on Swriwijaya Air flight SJ182, a Boeing 737-500 that crashed after departing Jakarta on Jan 9, 2021. From the report:

On 9 January 2021, a Boeing 737-500 aircraft, registration PK-CLC, on a scheduled domestic flight, took off from Soekarno-Hatta International Airport, Jakarta, to Supadio International Airport (WIOO), Pontianak, at 0736 UTC (1436 LT).

The flight was cleared by Air Traffic Control (ATC) to depart on a Standard Instrument Departure (SID) ABASA 2D to Flight Level (FL) 290. After taking off from Runway 25R, the autopilot was engaged at altitude of 1,980 feet. The pilots subsequently requested a heading change to 075° to enable them to deviate from weather. ATC responded with clearance for heading 075° and the flight began a turn to the right. ATC then instructed the flight to stop climbing at 11,000 feet due to conflicting departure traffic from Runway 25L.

About 10,600 feet, the aircraft heading started turning to the left. About 10,900 feet, the autopilot disengaged, and the aircraft turned to the left and started its descent. At 14:40:37 LT, the radar target of the aircraft disappeared on the ATC radar screen. Thereafter, ATC attempted to obtain information of SJY182 aircraft by calling several times, activating and calling on the emergency frequency, and asking other pilots that were flying nearby. All efforts were unsuccessful to get a response from the SJY182 pilot.

About 1455 LT, the Air Traffic Services (ATS) provider reported the occurrence to the Indonesian Search and Rescue Agency (Badan Nasional Pencarian dan Pertolongan/BNPP), and at 1542 LT, declared the uncertainty phase (INCERFA) of SJY182. The distress phase of SJY182 (DETRESFA) was subsequently declared at 1643 LT.

At the time of issuing this preliminary report, the memory unit of the Cockpit Voice Recorder (CVR) has not been recovered and the search is continuing.

The Komite Nasional Keselamatan Transportasi (KNKT) acknowledged that the safety actions taken by the Directorate General of Civil Aviation (DGCA) and Sriwijaya Air were relevant to improve safety, however there are safety issues remain to be considered. Therefore, the KNKT issued safety recommendations to address the safety issues identified in this report.

This investigation involved the participation of the National Transportation Safety Board (NTSB) of the United States of America as the State of Design and the State of Manufacture, and the Transport Safety Investigation Bureau (TSIB) of Singapore as States providing assistance. Both agencies have appointed their accredited representatives to assist in this investigation in accordance with the provisions in ICAO Annex 13.

The investigation is ongoing. Should further safety issues emerge during the course of the investigation, KNKT will bring the issues to the attention of the relevant parties and issue safety recommendation(s) as required.

Notably, there are findings related to the behavior of the autothrottle, as the thrust to the left engine was reduced during the climb:

After the aircraft climbed past 8,150 feet, the thrust lever position of the left engine started reducing, while the thrust lever position of the right engine remained. The FDR data also recorded the left engine (N1) was decreasing whereas the right engine N1 remained.

The SJY182 pilot requested to the Terminal East (TE) controller for a heading change to 075° to avoid weather conditions and was approved. The TE controller predicted the heading change would make the SJY182 conflicted with another aircraft that was departing from Runway 25L to the same destination. Therefore, the TE controller instructed the SJY182 pilot to stop climbing at 11,000 feet.

The FDR data recorded that when the aircraft’s altitude was about 10,600 feet the aircraft began turning to the left. The thrust lever position of the left engine continued decreasing while the thrust lever position of the right engine remained.

At 14:39:54 LT, the TE controller instructed SJY182 to climb to an altitude of 13,000 feet, and the instruction was read back by an SJY182 pilot at 14:39:59 LT. This was the last known recorded radio transmission by the flight.

The highest aircraft altitude recorded in the FDR was about 10,900 feet, thereafter the aircraft started its descent. The AP system then disengaged with a recorded heading of 016°, the pitch angle was 4.5° nose up, and the aircraft continued to roll to the left to more than 45°. The thrust lever position of the left engine continued decreasing while the right engine thrust lever remained.

About 5 seconds after the aircraft started its descent, the FDR data recorded the autothrottle (A/T) system disengaged and the pitch angle was more than 10° nose down.

At 14:40:48 LT, the radar target of the aircraft disappeared on the TE controller radar screen. Thereafter, the TE controller attempted to obtain information of SJY182 aircraft by calling the flight several times, activating the emergency frequency and calling SJY182 on that frequency. The TE controller also asked other pilots that were flying nearby to attempt contact with the flight. All efforts were unsuccessful to get any response from the SJY182 pilot.

The data from the FDR indicates the start of the turn to the left coincided with a reduction in thrust from the left engine, which would cause a yaw-induced bank to the left, although that was likely moderated by the autopilot. After the autopilot disengaged, the left thrust continued to decrease, the plane rolled left to a bank angle of 45°, and the plane rapidly descended. The pilots were not able to recover from this upset attitude.

Comment: The preliminary report does not discuss what pilot inputs occurred after the turn to the left began, neither while the autopilot was engaged nor after it disengaged. Correct right rudder input would have helped control the aircraft; incorrect left rudder input would have exacerbated the problem.

Introduction

Independent researchers investigating the disappearance of MH370 today released a new technical report to guide the next search for the debris field on the floor of the Southern Indian Ocean (SIO). The report provides the scientific and mathematical foundation that was used to define the recommended search area that was disclosed last month. The authors of the report are Bobby Ulich, Richard Godfrey, Victor Iannello, and Andrew Banks.

The full report, including all appendices, is available for download. What follows is a brief summary of the important results.

The flight of MH370 was analyzed from takeoff to impact in the SIO using a comprehensive, fully integrated model. The model was developed using exhaustive data sets and technical documentation available from both public and confidential sources, and includes:

• radar data collected by military and civilian installations in Malaysia
• timing and frequency measurements collected by the Inmarsat satellite network
• aircraft performance data for Boeing 777-200ERs
• historical performance data for airframe 9M-MRO
• navigation and speed modes for automated flight
• drift analysis of debris that floated and was recovered in East Africa
• aerial search results from March and April 2014
• weather data along the flight path

A total of 2,300 possible flight paths were evaluated, and an overall probability metric was defined that incorporates the information from all the data sets. The highest probability flight path was identified as due south from waypoint BEDAX, which is about 185 km (100 NM) to the west of Banda Aceh, Sumatra, and an impact in the SIO near S34.2342° E93.7875°, which is 4380 km (2365 NM) from BEDAX.

The work included the development of an accurate fuel consumption model, and well as a statistical metric for the expected random noise inherent in the recorded satellite data. These improvements allowed the rejection of hypothetical flight paths that were previously believed to be possible.

Turnback Across Malaysia

After takeoff, the climb was normal, and the aircraft leveled at a cruise altitude of FL350 (35,000 ft standard altitude), tracking towards waypoint IGARI in the South China Sea. After flying by waypoint IGARI, the transponder was disabled as the aircraft turned towards waypoint BITOD. On passing the FIR boundary between Malaysia and Vietnam, the aircraft began turning back towards the Malay peninsula, and flew towards Kota Bharu airport, as shown in the figure below.

The civilian radar installation at Kota Bharu captured MH370 as it flew towards and then away from Kota Bharu. An analysis of this radar data shows that the aircraft climbed from FL350 to about FL385 (true altitude of 40,706 ft) and accelerated to near its maximum operating speed of Mach 0.87 as it passed to the north of Kota Bharu. It then flew across the Malay peninsula and towards Penang Island, where a civilian radar installation at Butterworth Airport captured the radar targets. As it passed to the south of Penang Island near Penang Airport, it slowed down to a speed closer to Mach 0.84, and turned to the northwest over the Malacca Strait.

Flight over the Malacca Strait and Around Sumatra

The flight over the Malacca Strait was captured by Malaysian military radar, as disclosed in a briefing to family members in Beijing in March 2014. After passing Penang Island, the aircraft proceeded on an exact course to waypoint VAMPI, and intercepted airway N571. The last radar target was captured at 18:22:12 about 10 NM after passing waypoint MEKAR on N571. The flight over the Malacca Strait, around Sumatra, and towards the South is shown in the figure below.

In the report, it’s deduced that soon after the aircraft was beyond Malaysia radar coverage, MH370 began a “lateral offset” that would position the aircraft about 15 NM to the right of N571, possibly to ensure separation from other traffic. Once this offset was completed at around 18:29, a descent began, and when the altitude reached FL250 (well below the minimum altitude of FL275 for traffic on N571), the aircraft turned directly towards waypoint IGOGU on a westerly course.

On reaching IGOGU, it’s deduced that the aircraft continued its descent and turned due south, flying along the FIR boundary between Malaysia and India. It leveled at around FL100 (10,000 ft standard altitude), and continued south until reaching the FIR boundary of Indonesia. It then turned to the west, away from Indonesia, and flew along the FIR boundary.

It’s further deduced that the final course change was due south towards waypoint BEDAX. After passing BEDAX, a climb to FL390 began at around 19:24, ending at around 19:41. The aircraft continued on a due south course at LRC speed towards the South Pole until fuel exhaustion occurred in the SIO at around 00:17.

The authors observe that the trajectory last covered by Malaysian radar was to the northwest along N571. Only when beyond Malaysian radar coverage was a descent to a lower altitude initiated, which was followed by turns to the west and south. It’s hypothesized that the intention was to lead the searchers into believing the trajectory continued along N571 to the northwest, as the transit at low altitude would have been below the radar horizon of Indonesian and Thai radar installations. It is only because of the analysis of the satellite data first performed by Inmarsat that we know the flight path continued into the SIO. Very likely, the party responsible for the diversion was not aware that this data set was recorded and could be later used to deduce a path.

The entire flight path is summarized in the figure below.

Possible MH370 Sighting by Kate Tee

Kate Tee was on a sailboat on 7th March 2014 southeast of Great Nicobar Island and northwest of Sumatra. She reported seeing a large aircraft coming towards her from the north, flying at an unusually low altitude. At around the same time, she reported that the sailboat gybed accidentally. This gybe event and the track of the sailboat were recorded on the GPS system on board, and serves to define a position and an approximate timestamp for her sighting. In this time interval, the sailboat was close to waypoint NOPEK along the FIR boundary between Malaysia and India, which may help to explain her sighting.

The figure below depicts the path of MH370 at 18:55:57 and the GPS track from the sailing boat every five minutes from 18:25 to 19:25. The GPS track from the sailing boat and the deduced flight path of MH370 appear to align.

Probability of Various Paths to the SIO

In order to rank the likelihood of various reconstructed paths to the SIO, the available data sets were compared to predictions from the mechanistic models, and the match between the measured data and the models were used to develop probabilities for each path. For each path, probabilities were calculated for four classes of measured data:

• Measured satellite data compared with model predictions for navigation, weather, and data statistics
• Observed fuel endurance with model predictions from fuel consumption models
• Observed location and timing of recovered debris with predictions from drift models
• Failure to find floating debris compared with the areas targeted by the aerial search

The overall (composite) probability for a path was calculated as the product of the of the probabilities of the four classes of data and then normalized to produce a probability density function (PDF) in which the cumulative probability across all latitudes is unity.

Each panel in the figure below shows the probabilities for each class of data, followed by the overall probability. If only considering the match to the measured satellite data presented in the first panel, the probability is highest for the path ending near 34.3°S latitude. However there are many other prominent peaks for paths ending along the 7th arc to the north and south of 34.3°S, so further discrimination is required using the other three data sets.

Peaks corresponding to end points to the south of 34.3°S are rejected because of low probabilities of matching the observed fuel endurance and the reports of the recovered debris in East Africa. On the other hand, end points to the north of 34.3°S are rejected because the impact would have produced a floating debris field that would have been detected by the aerial search with a high probability. What remains is a single prominent peak at 34.3°S, which represents a due south path from a position near waypoint BEDAX towards the South Pole.

Search Area Recommendation

The analysis presented above suggests that MH370’s flight path in its final hours followed E93.7875° longitude, corresponding to a great circle path between waypoint BEDAX and the South Pole. Using this result, the last estimated position (LEP) is S34.2342° E93.7875°. Although some of the subsea was previously searched in this vicinity, the terrain is challenging, and the debris field might have been not detected, or detected and misinterpreted. There is also the possibility that there was a controlled glide after fuel exhaustion, and an impact well beyond what was previously searched.

To define the search area near the LEP, three cases were considered, each with an associated search area. The highest priority search area, A1, of 6,719 NM² (23,050 km²), assumes there were no pilot inputs after fuel exhaustion. The search area of next highest priority, A2, encompasses 6,300 NM² (22,000 km²), and assumes there was a glide towards the south after fuel exhaustion. The lowest priority, A3, is the controlled glide in an arbitrary direction with an area of around 48,400 NM² (166,000 km²). The three search areas are shown in the figure below.

Discussion

A new report is now available that suggests that MH370’s flight path in its final hours followed E93.7875° longitude, corresponding to a great circle path between waypoint BEDAX and the South Pole. The report concludes that an impact near S34.2342° E93.7875° is most likely.

The technical details are included in the report so the analytical results can be evaluated, reviewed, and replicated by other investigators.

Three end-of-flight scenarios were considered, and a recommended search area for each scenario was defined and prioritized. As parts of the recommended search areas were already searched by GO Phoenix and Ocean Infinity, we recommend a thorough review of the existing sonar data, recognizing that the quality of the data in that vicinity varied due to challenging terrain.

As there are no ongoing MH370 search activities, the authors of the report believe the new technical results provide credible evidence that justifies a new search.

Update on March 9, 2020 – Civilian Radar Data

A newer version of the civilian radar data is now available as an Excel file. This data set represents the raw data from the Kota Bharu and Butterworth radar heads before the data was processed and stored by the radar network. This data set was used for the calculations in the report. Also included in the Excel file is the methodology for converting the raw data to latitude and longitude.

Update on March 12, 2020

The best estimate of the point of impact (BE POI) has been renamed the last estimated position (LEP), which is a more accurate description. The location is unchanged.

Update on January 7, 2021 – Links for CSIRO Drift Results

Some contributors are performing their own drift studies using the results from the CSIRO calculations. The following links can be used to download the results as MATLAB data files. The calculations were performed for floating particles that are considered “generic” and for floating particles that are hydrodynamically and aerodynamically similar to the flaperon.

Generic particles: http://www.marine.csiro.au/~griffin/MH370/data/br15_MH370_IOCC_tp3l1p2dp_arc7_4408_15_tracks.mat

Flaperon particles: http://www.marine.csiro.au/~griffin/MH370/data/br15_MH370_IOCC_tp3l1p2dpf10_20_99_arc7_4408_15_tracks.mat

[This is the web version of a paper written by me, Bobby Ulich, Richard Godfrey, and Andrew Banks. The PDF version is available here.]

1 Introduction

Presently, there is no active search to find MH370’s debris field on the seabed of the Southern Indian Ocean (SIO). The last search was conducted by Ocean Infinity, who consulted with official and independent researchers, and subsequently scanned the seabed along the 7th arc as far north as S25° latitude. Since then, independent researchers have continued to analyze the available data to understand what areas of seabed are the most likely, and why previous search efforts have been unsuccessful. The objective is to define a manageable area for conducting a new search of the seabed.

In a previous post [1], we presented an overview of Bobby Ulich’s research [2], aimed at more precisely locating the point of impact (POI) using statistical criteria that requires that random variables (such as the reading errors of the satellite data) are not correlated, i.e., are truly random. A subsequent post [3] describes the work of Richard Godfrey et al. [4] to analytically evaluate a large number of candidate flight paths using these and other criteria. The results of that work suggest that the final hours of the flight were due south in the Indian Ocean along E93.7875° longitude, which matches a great circle between the waypoint BEDAX (about 100 NM west of Banda Aceh, Sumatra) and the South Pole. The POI was estimated to lie close to the 7^th arc around S34.4° latitude.

Work continues to evaluate candidate paths using an accurate integrated model that includes satellite data, radar data, flight dynamics, automated navigation, meteorological conditions, fuel consumption, drift models, and aerial search results. That exhaustive work is nearing completion, and documentation of the methods and the results is ongoing. Like the previous work [4], the ongoing work suggests that the final trajectory of MH370 was most likely along a due south path along E93.7875° longitude.

In the interest of providing information in a timely manner, we have chosen to recommend a search area based on this most likely path. A comprehensive paper which expands upon the methods and results presented in previous work [2,4], and provides further justification for the selected path, will be available in the near future.

2 Last Estimated Position (LEP)

Using the results of the analysis presented above, the last estimated position (LEP) is based on a final trajectory of a constant longitude of E93.7875°, which is consistent with the aircraft traveling due south from waypoint BEDAX towards the South Pole. The LEP is based on a location exactly on the 7^th arc, and the uncertainty associated with the LEP helps define the limits of the recommended search area.

When the SDU logs onto the Inmarsat network, the SDU begins the log-on sequence by first transmitting a log-on request, which is followed some seconds later by transmitting a log-on acknowledge. For MH370, those were the final two transmissions, transmitted at 00:19:29 (BTO = 23,000 μs) and 00:19:37 (BTO = 49,660 μs), respectively. From past work [6,7], we also know that the BTO values for the log-on request and log-on acknowledge are “anomalous” in that the raw values are outliers that require a correction. Fortunately, the required corrections are repeatable, and can be determined by analyzing prior flights.

Using the Inmarsat transaction logs for MH371 and MH370 [8], the BTO log-on statistics from March 7, 2014, 00:51:00, to March 8, 2014, 16:00:00, were analyzed to determine what offsets might be applied to log-on requests and log-on acknowledges. There were 29 cases in which there was an R-channel burst just after the initial (R600) log-on request and subsequent (R1200) log-on acknowledge. Of those 29 cases, the number of packets in the burst was 3 for 20 bursts, 2 for 6 bursts, and 1 for 3 bursts. The average of each burst was used as the reference for the log-in request and log-on acknowledge. In 4 of the 29 cases, the correction for the log-on request was near zero, i.e., the BTO values were not anomalous, so only 25 cases were included for log-on request statistics.

For the log-on requests, the mean offset from the R-channel burst is 4,578 μs with a standard deviation of 94 μs. The maximum offset was 4,800 μs (+222 μs from the mean) and the minimum was 4,380 μs (-198 μs from the mean).

For the log-on acknowledge, we considered a correction of the form (a + N × W), where a is a constant, N is an integer, and W represents the delay per slot. We found that the standard deviation of the correction error (using the average of the R1200 burst as the reference) to be minimized for W = 7812.0 μs. That’s very close to the 7812.5 μs value suggested by the 128 Hz internal clock of the SDU. By forcing W=7812.5 μs, the mean error to the correction is 23 μs, and the standard deviation is 30 μs. The observed standard deviation is very close to the 29 μs that DSTG recommends to use for “normal” R1200 values [7]. The consistency of the standard deviation of the corrected anomalous values with the standard deviation of the values not requiring a correction is reassuring. The total correction to the BTO for log-on acknowledges is therefore (23 + N × 7812.5) μs.

Using these log-on corrections produces corrected BTO values at 00:19 equal to:

00:19:29: 23000 – 4578 = 18422 μs
00:19:37: 49660 – 23 – 4 × 7812.5 = 18387 μs

We combine these values to determine the BE value of BTO by using the inverse of the variance as weighting, yielding a BE value of BTO = 18,390 μs (σ = 29 μs). Using this BE value of BTO with the longitude of E93.7875° and an assumed geometric altitude of 20,000 ft results in a position of S34.2342° E93.7875° at 00:19:29, which we assign as the LEP.

3 Terrain Near the LEP

Figure 1 shows the subsea terrain in the vicinity of the LEP using data provided by Geosciences Australia [5]. Some of this area has already been searched by GO Phoenix (managed by the ATSB) using a towfish, and by Ocean Infinity (OI) using Seabed Constructor and its team of AUVs. However, as can be seen in Figure 1, some of the previously searched area has challenging terrain with steep slopes, and the debris field may have been either not detected due to terrain avoidance or shadows, or detected but not properly interpreted by reviewers. In particular, there is a steep slope that lies about 20 NM due south of the LEP that was not scanned by the towfish and appears to have been only partially scanned by the AUVs.

Figure 2 shows the ocean depth along a line of constant longitude in the vicinity of the LEP. The previously identified steep slope to the south of the LEP has a grade of about 30%. To the north, another slope has a grade of 44%. This slope was beyond the limits of the search boundaries of GO Phoenix, but was scanned by Seabed Constructor’s AUVs.

4 No Pilot Inputs after Fuel Exhaustion

In order to define the search area limits, we first consider no pilot inputs after fuel exhaustion. For this case, the search area limits are defined by the uncertainty of the LEP and the uncertainty of the uncontrolled flight path before impacting the ocean.

4.1 Uncertainty Due to BTO Noise

The uncertainty in the BTO produces a corresponding uncertainty in the position of the 7^th arc. The calculated sensitivity of the arc position to the BTO is 0.104 NM/µs, i.e., a 1-µs increase in BTO pushes the 7^th arc outward (southeast) by 0.104 NM. The 1-σ uncertainty of the arc position due to BTO noise is therefore 0.104 NM/µs × 29 µs = 3.0 NM.

4.2 Uncertainty Due to Altitude at 00:19:29

The LEP is based on an assumed altitude of 20,000 ft that is reached at 00:19:29, i.e., 1.5 to 2 minutes after fuel exhaustion. As the BTO represents the range between the aircraft and the satellite, the position of the 7^th arc as projected on the surface of the earth depends on the altitude. As the aircraft would be between 0 and 40,000 ft at this time, we assign this altitude range as the 2-σ limits. The calculated sensitivity of the BTO to altitude is 12.8 µs/10,000 ft. The 1-σ uncertainty of the arc position due to altitude uncertainty is therefore 0.104 NM/µs × 12.8 µs = 1.33 NM.

4.3 Uncertainty of Turn Between Fuel Exhaustion and 00:19:29

Boeing conducted 10 simulations to determine the behavior of MH370 after fuel exhaustion with no pilot inputs [9] using a high-fidelity simulator for the 777-200ER aircraft. The trajectories for these simulations are shown in Figure 3. For each simulation, the autopilot was automatically disengaged after fuel exhaustion, and the aircraft turned slightly either to the right or to the left depending on a number of factors, including the electrical configuration, the initial conditions of the flight parameters, and the meteorological conditions. Within the 2-minute interval between fuel exhaustion and the log-on request at 00:19:29, the slight turn shifted the location that the aircraft crossed the 7^th arc relative to where it would have crossed the 7^th arc if the autopilot had remained engaged and the course was maintained. For the 10 cases, the lateral shift along the arc varied between 1.1 and 8.8 NM. As we don’t know how well the 10 cases represented the actual conditions, we conservatively assign a 1-σ uncertainty of 8.8 NM along the 7^th arc due to the slight turn between fuel exhaustion and crossing the 7^th arc.

4.4 Uncertainty of Trajectory Between 00:19:29 and the POI

In all 10 of the Boeing simulations, the aircraft banked after the autopilot was disengaged following fuel exhaustion. The magnitude and direction of the bank that develops is the net effect of a many factors, including thrust asymmetry, rudder inputs from the Thrust Asymmetry Compensation (TAC), rudder trim input, lateral weight imbalance, aerodynamic asymmetry, and turbulence, any of which increases the bank angle. On the other hand, the tendency to bank is opposed by the dihedral effect of the wings and the low center-of-mass. For all the simulations, the POI was within 32 NM from the 7^th arc crossing at 00:19:29, as shown in Figure 3.

In some of those simulations, the bank was shallow, and phugoids lasting many minutes developed. In only 5 of the simulations did the rate of descent exceed 15,000 fpm while also experiencing a downward acceleration exceeding 0.67 g, which are the values of descent rate and downward acceleration derived from the two final values of the BFO. For these cases, the POI occurred between 4.7 and 7.9 NM from the point where the descent rate first exceeded 15,000 fpm. Other simulations of a banked descent after fuel exhaustion [10] suggest that an uncontrolled Boeing 777 would travel an additional distance of about 5 NM after a downward acceleration of 0.67 g and a rate of descent of 15,000 fpm simultaneously occur.

None of the Boeing simulations predict that the aircraft was in a steep descent as the 7^th arc was crossed, so there is an unexplained discrepancy between the Boeing simulations and the descent rates derived from the final BFO values. In light of this discrepancy, we choose to not limit the distance traveled after crossing the 7^th arc by only considering the distance traveled after the steep descent. Instead, we assign a 2-σ value of 32 NM for the distance traveled after crossing the 7^th arc, based on the farthest distance that was observed in all 10 simulations, irrespective of the magnitude and timing of the descent rates.

4.5 Uncertainty Due to Navigation Error

There are two autopilot modes that could result in a trajectory that nominally follows a great circle between BEDAX and the South Pole. After passing BEDAX, if the autopilot remained in LNAV and the active waypoint was the South Pole (entered as 99SP, S90EXXXXX, or S90WXXXXX), the aircraft would fly along the longitude E93.7875° within the accuracy of the GPS-derived navigation. In this case, the expected navigational error would be much smaller than other sources of error, and can be safely ignored.

The other possibility is that after passing BEDAX, the autopilot was configured to fly along a constant true track (CTT) of 180°. Selecting this mode would require manually changing the heading reference switch from NORM to TRUE, as directions on maps, procedures, and in ATC communications are normally referenced to magnetic north, except in polar regions.

Unlike LNAV mode in which the cross-track error of the target path is continuously calculated and minimized, errors in track (which may be positive or negative) in CTT mode produce error in the due south path that may accumulate without correction. We assume here that that course is nominally 180° True, with a 1-σ uncertainty of 0.1 deg (0.001745 rad). As the distance between BEDAX and the 7^th arc along the line of constant longitude is around 2365 NM, the cross-track error has a mean value of zero and a 1-s uncertainty of 4.1 NM. However, since the path crosses the 7^th arc at an angle of 46 deg, the 1-σ uncertainty in position along the 7^th arc is increased to 5.9 NM.

4.6 Search Area Based on No Pilot Inputs

Assuming there were no pilot inputs after 19:41, the uncertainties in the POI are summarized in Table 1. The 1-σ uncertainty along the 7^th arc is 19.2 NM, and 16.3 NM normal to the 7^th arc.

Table 1. Summary of POI Uncertainties Assuming No Pilot Inputs

To achieve a confidence level of 98% requires searching an area defined by ±2.3-σ limits, with the LEP at its center. Based on this, the recommended area is 91 NM × 74 NM, and the total area is 6,719 NM², or 23,050 km². This area is depicted as A1 in Figure 4.

5 Controlled Glide Due South

We next consider the case in which there was a controlled glide after fuel exhaustion, which would extend the search area beyond the search area based on no pilot inputs. For a Boeing 777 gliding at an optimum speed, a glide ratio of about 20:1 can be achieved. This corresponds to a descent angle of 2.86°, and a continuous reduction in altitude of 1000 ft for every 3.29 NM traversed. Assuming an initial altitude of 42,400 ft (based on a standard altitude of 40,000 ft), the impact could be as far as 140 NM from the point of fuel exhaustion (ignoring the headwind at some altitudes, which would reduce the ground distance of the glide). If the glide started at a lower altitude, or if non-optimum airspeed was flown, the glide distance would be less. The uncertainty associated with the glide distance is much larger than other uncertainties, so we assume that with a glide, the POI might have been as far as 140 NM from the LEP, and use that as the southern limit.

The width of the search area as defined by a controlled glide is more difficult to estimate. If an experienced pilot wished to continue the flight path on a due-south course, that could be accomplished quite precisely. For example, if the autopilot mode was CTT before the fuel exhaustion, then a constant (true) track of 180 deg could be maintained using the indicated track shown in the navigation display. On the other hand, if the autopilot mode was LNAV before fuel exhaustion, then the cross-track error could be minimized by following the “magenta” line defined by the BEDAX-South Pole leg. In either case, the search area width could be limited to less than 10 NM to either side of the projected flight path.

Because we cannot be sure that there was an attempt to precisely follow a due south path, we assign a generous width to this part of the search area, centered on the due south path. A width of +/- 33 NM results in an additional search area of 6,300 NM² (22,000 km²), and produces an area in similar size to A1. It is depicted as A2 in Figure 4.

6 Controlled Glide in an Arbitrary Direction

If there was a controlled glide that did not continue along the path flown prior to fuel exhaustion, it is nearly impossible to predict the direction. For instance, a path to the west would shield the pilot’s eyes from the rising sun to the east. A path to the northeast would extend the glide due to the tailwind. A path to the west would create more distance to the Australian shoreline. A path towards the northwest would be towards Mecca. Any of these directions is less likely than a continuation of the due south path, but it becomes nearly impossible to prioritize among these or other directions. Instead, we define area A3 as the circle with a radius of 140 NM, excluding the areas already included in A1 and A2. The area is roughly 48,400 NM² (166,000 km²), and is depicted as A3 in Figure 4.

7 Conclusions

Recent analyses suggest that MH370’s flight path in its final hours followed E93.7875° longitude, corresponding to a great circle path between waypoint BEDAX and the South Pole. Using this result, the last estimated position (LEP) is S34.2342° E93.7875°. Although some of the subsea was previously searched in this vicinity, the terrain is challenging, and the debris field might have been not detected, or detected and misinterpreted. There is also the possibility that there was a controlled glide after fuel exhaustion, and an impact well beyond what was previously searched.

To define the search area near the LEP, three cases were considered, each with an associated search area. The highest priority search area of 6,719 NM² (23,050 km²) assumes there were no pilot inputs after fuel exhaustion. The search area of next highest priority encompasses 6,300 NM² (22,000 km²), and assumes there was a glide towards the south after fuel exhaustion. The lowest priority is the controlled glide in an arbitrary direction with an area of around 48,400 NM² (166,000 km²).

8 References

[1] Iannello, “A New Methodology to Determine MH370’s Path”, May 31, 2019, https://mh370.radiantphysics.com/2019/05/31/a-new-methodology-to-determine-mh370s-path/

[2] Ulich, Technical Note presented in [1].

[3] Iannello, “A Comprehensive Survey of Possible MH370 Paths”, June 30, 2019, https://mh370.radiantphysics.com/2019/06/30/a-comprehensive-survey-of-possible-mh370-paths/, excerpted from [4].

[4] Godfrey, Ulich, Iannello, “Blowin’ In The Wind: Scanning the Southern Indian Ocean for MH370”, June 24, 2019, https://www.dropbox.com/s/9rpcnslz9g4izet/2019-06-30%20Blowing%20in%20the%20Wind%20-%20Scanning%20the%20Southern%20Indian%20Ocean%20for%20MH370.pdf

[5] “MH370 Data Release”, Geosciences Australia, https://www.ga.gov.au/about/projects/marine/mh370-data-release

[6] Ashton, Shuster-Bruce, College, Dickinson, “The Search for MH370”, The Journal of Navigation, Vol 68 (1), January 2015.

[7] Davey, Gordon, Holland, Rutten, Williams, “Bayesian Methods in the Search for MH370”, Defense, Science, and Technology Group, Australia, November 30, 2015.

[8] Iannello, “The Unredacted Satellite Data for MH370”, June 12, 2017, https://mh370.radiantphysics.com/2017/06/12/the-unredacted-inmarsat-satellite-data-for-mh370/

[9] Iannello, “End-of-Flight Simulations of MH370”, August 2018, https://mh370.radiantphysics.com/2018/08/19/end-of-flight-simulations-of-mh370/

[10] Iannello, “MH370 End-of-Flight with Banked Descent and No Pilot”, June 4, 2017, https://mh370.radiantphysics.com/2017/06/04/mh370-end-of-flight-with-banked-descent-and-no-pilot/

Update on March 12, 2020

The best estimate of the point of impact (BE POI) has been renamed the last estimated position (LEP), which is a more accurate description. The location is unchanged.