A week after MH370 went missing, the Malaysian government dropped a shocker: Inmarsat, the satellite communications provider, had recorded signals from the plane that allowed them to calculate the plane’s distance from the satellite about once an hour for nearly six hours.
At first, the Malaysians only released a rough sketch of the final arc: two matching fragments of a circle, 3000 miles in radius, that stretched from Kazakhstan in the north to the remote Indian Ocean in the south. This in itself was a major step forward, in that it drastically reduced the numer of possible places the plane could have gone. But even more enticingly it suggested that if we had the numerical values for all the pings, and could figure out what speed the plane was flying at, we would be able to identify the route that the plane was taken and thus its precise final destination.
The scientists at Inmarsat recognized this immediately, and as Chris Ashton et al relate in their paper in the Journal of Navigation, they quickly plugged in the most logical speed value — typical airliner cruise speed, around Mach 0.83 — and concluded that the plane flew either to the middle of Kazakhstan or almost directly south into the Indian Ocean. (See image above.) As a result, the Malaysian government submitted a request to the Kazakh government asking that it be allowed to set up a search operation in the country, and planes were dispatched to search the ocean surface near the southern potential end point. Hopes were high. After satellites spotted what appeared to be floating material in the southern ocean, Australian Prime Minister Tony Abbott told his country’s parliament that it was a “potentially important development.’’
Of course the idea that the plane flew straight and fast, as airliners typically do, was just an assumption. Theoretically, it could have flown from ping ring to ping ring at any number of speeds along any number of routes, including straight, curvy, and zig-zag. Most of these alternatives would have resulted in the plane winding up at a lower latitude. And indeed, within a few days the authorities abandoned the southernmost search area and started scouring a section of the ocean much further north. The decision to shift the search zone appears to have been heavily influenced by a second set of data also derived from the handshakes exchanged between the plane and the satellite: the so-called BFO (“burst frequency offset”) data. After much head-scratching, Inmarsat believed that they had come up with an algorithm that allowed them to understand the physical implications of this data, and it told them that a) the plane had definitely gone south, not north, and b) the plane had not been flying straight and fast, as initially supposed, but instead taken a slower and/or meandering course and wound up about a thousand miles from the initial search area.
Frustratingly, for those of us who were watching from the sidelines and eager to understand what was going on, neither Inmarsat nor the Malaysians were willing to either release their numerical data nor to explain their BFO algorithm. We just had to take their word for it. Which was enormously frustrating, since it seemed tantalizingly plausible that if we had the data and understood the physical processes that generated it, we would be able to mathematically solve for the location of the plane. Et voila: mystery solved.
Finally, after much pressure from the public, the Malaysians did finally release most of the Inmarsat data in May; the following month, the Australian Transport Safety Bureau (ATSB) released a report which explained how the then-current search area had been arrived at and explained in some detail how the BFO algorithm worked.
Many independent experts, including members of the Independent Group, leapt at the chance to finally get under the hood of the BFO algorithm and see if they could reach their own conclusions about where the plane went. In time, however, their optimism faded. In turns out that the BFO data offers only a very imprecise gauge of a plane’s location or direction of travel. To test the algorithm, for instance, scientists working for the search effort compared BFO data received from a known flight with the plane’s actual path. They found that, of the thousands of possible paths that matched the BFO data, even the one that most closely matched the actual flight was hundreds of miles off in places.
We seemed to be almost back to where we started: we had a set of ping rings that showed us seven quite accurate (within 10 km, the ATSB estimates) arcs along which the plane must have been at seven moments in time, but with only vague intimations of where along those arcs the plane actually was.
Gradually, however, without much fanfare, it has become clear that other, non-BFO techniques can provide insight into how MH370 was traveling after it disappeared from radar, and these in turn offer a strong suggestion about where the plane went.
- Geometrical. The distance between the ping rings, especially in the middle portion of the flight between 19:41 and 22:41, is consistent with straight-line flight.
- Aeronautical. Jet planes are remarkable forms of transportation, but they are efficient only in a fairly narrow range of speeds and altitudes. That is to say, they are happy when flying high (35,000 to 42,000 feet) and fast (Mach 0.78 to Mach 0.84, give or take, which translates to 450-484 knots at 35,000 feeet). At those altitudes, there is nothing for them to bump into, except for an occasional thundercloud. So airliners tend to go from here to there in a pretty close approximation to a straight line. As an addendum to that thought, I would like to add that airliners (so I’m told) are not that easy to hand-fly at 35,000 feet, the way one would hand-fly a single-engine Cessa at 5,000 feet; airline pilots generally let the autopilot steer the plane, and an autopilot can keep a plane essentially glued to a very, very straight line. So to recap: airliners spend most of their time flying high, fast, and straight. This is especially true over the open ocean, and extra especially true if one’s purpose is to fly to the remotest corner of an ocean one can find. There is simply no reason to, say, suddenly turn five degrees to the left before proceeding ownward. That’s not to say that one can’t, or that it’s physically impossible, to make some random turn in the middle of nowhere for no reason. It’s just very hard to think of a reason why someone would do that. So we’d expect MH370 to have flown south in a straight line. Oh, and this is especially true, of course, if the pilots have taken a poison pill, been hacked to death, or succumbed to hypoxia. In such cases we would definitely expect the plane to fly south in a straight line, unless before they lost consciousness someone programmed a zig-zag series of waypoints into the autopilot just to flummox investigators in the future. Again, not impossible, but not very likely-seeming, either.
- Historical. As described in my post “What We Know Now,” several people have traced the radar track that MH370 followed before it disappeared from primary radar in order to calculate what speed the plane was traveling at. Richard Godfrey’s calculated average groundspeed is 504 knots, which translates into an airspeed of 496 knots. This lies at the fast end of the normal operational speed range, suggesting that the hijackers were in a hurry to get somewhere.
- The Brian Anderson technique. In the same post I describe a technique IG member Brian Anderson devised to estimate the speed of the plane between 18:28 and 19:40, based on an inferred point of closest approach to the satellite. The technique yields a best fit at about 494 knots.
- Ping-ring Gap Inference. One of the peculiar features of MH370’s flight to the south, which presumably began some time after 18:22, is that the early portion of that flight, accordiing to the ping rings, was nearly tangential to the ping rings. As a result, if you start from any given point on the 19:41 ping arc, and head for a point that is, say, 450 nm away on the 20:41 ping arc, you will find that there is a very small angular distance between that course, and a course that intersects the 20:21 ping arc 500 nm away. This is not as true later on; as the plane moves progressively away from the satellite, its course becomes less tangential to the ping rings, and the distance traveled less sensitive to the angle of the course. The surprising upshot of all this is that, so long as you start with a reasonable speed between 19:41 and 20:41, you always wind up traveling at more or less the same speeds during the next two intervals: about 510 knots during the first interval, and about 505 knots during the second. In essence, the plane’s ping rings don’t just narrow down where the plane was, they actually tell us how fast it was moving.
I believe that this last technique has not been described before so I’m going to go into a bit more detail. As an example, let’s look at three routes based on recently published models (two by IG members, one by Ashton et al). In each case, I drew the line on Google Earth, then measured the distance between the points where this line crossed the ping rings. (There are numerous sets of ping rings available to choose from, all slightly different; I chose rings built from calculations supplied by Richard Godfrey, but I’ve also tried other sets of ping rings as well, the results are broadly similar. Note that each of the models was constructed different sets of ping rings, and the initial segment in particular is highly sensitive to the location of the rings, which is why the early speeds vary so widely.) Here are the results:
Note that this technique doesn’t allow you to learn anything about the speed prior to 20:41. However, as noted above, Brian Anderson’s technique suggests a speed between 19:40 and 20:40 of about 494 knots, and Malaysian radar data allows us to calculate a speed prior to 18:22. All of these speeds are very approximate, yet they seem broadly consistent with groundspeeds in the vicinity of 500 knots.
What kind of speed mode could underlie this observed pattern of speeds? There are basically three options: constant Mach, LRC, and ECON. Constant Mach is self-explanatory; the plane will maintain a constant Mach number, which corresponds to a lower true airspeed as the ambient temperature decreases. LRC, or long-range cruise, is a calculated Mach number that decreases as the weight of the plane decreases due to fuel burn. Finally, ECON speed is calculated based on input fuel and time costs and takes into account temperature, weight, and headwinds, but unfortunately is complex in ways that we can’t model so will have to leave off the table for the time being.
As the plane flies to the south, all of the factors will tend to make it gradually fly more slowly over the ground. Prevailing tail winds turn to head winds. The temperature decreases. And the plane grows lighter as the fuel burns off. Yet the speeds we’ve derived from the ping rings don’t show much of a decrease until the very end. Thus in my estimation a constant Mach mode offers the best fit, as seen below:
A couple of points to observe:
- The speeds derived from the spacing of the ping rings are consistently about 10 knots faster than Mach 0.84. If the technique I’ve described is valid, that implies that the hijackers were, in the vernacular, hauling ass.
- There are a lot of uncertainties involving this technique, so I would caution against putting too much weight in the details. For instance, the ping rings are only accurate to about 10 km; moving the 20.41 ping ring 5 miles inward would reduce the speed during the preceding interval by that many knots, and increase the speed of the subsequent interval. The headwinds calculations are also a huge source of uncertainty, since we don’t know how accurate the data are or, more importantly, where exactly the plane’s track actually ran.
- I am reluctant to read too much into the discrepency between 19:41-20:41 and subsequent intervals because it is derived using a different technique.
- Having said that, it may be significant that the speed is 10+ knots too high for the two hours before 22:41, and 10 knots too low afterward. (I repeat: “may be”!) If there were in fact a marked slow down during this interval, it could be due to a) a pre-programmed change in heading or engine thrust setting b) much stronger than estimated winds aloft, most likely associated with the southern jetstream, or c) the plane was actively being steered during the final 90 minutes.
This latter line of reasoning may have been what led Emirates’ Tim Clark to say that he thinks the plane was under control until the end.
@jeffwise: Can you please give a little more information about the paths you are comparing? For instance, the assumptions of what happened between 18:28 and 19:41; the azimuth of the path after 19:41; and the navigational mode? For instance, the path presented in the Ashton paper is neither constant speed nor constant true track. The speeds calculated are a strong function of the assumptions I am questioning.
Best-fit model to a turn at IGOGU at 18:39 (just ahead of the 1st missed phone call) gives initial velocity of 450 knots, initial heading of 186.3 degrees, magnetic track and constant mach modes. Final position -33.5 geodetic latitude and 94.4 longitude. Ulich found a fairly similar track for this mode. However, I find rms BTO error of 15 microseconds and rms BFO error of 2.3 hz, both well within the expected errors of 26 microseconds and 2.3 hz to 2.8 hz from both the pre-IGARI portion of the flight and from the MH21 data presented in the Ashton et al. paper.
@sk99: Thank you proposing a new path with some details. I would like to try to replicate it. Did you include temperature and winds? Can you provide the position and speed at the ping times? Was the magnetic track constant starting at 18:39?
VictorI:
Wind and temp data are from files that I downloaded from here:
http://ready.arl.noaa.gov/gdas1.php
For completeness, I extracted temp and winds for 3 times (18:00, 21:00, and 00:00) and all pressure levels from 18000 to 39000 feet. Will provide table of positions and velocities later. Yes, magnetic heading was constant (thus a curvy path on the ground.) One improvement I found necessary is to take small time steps when integrating along a curvy path; I now take 1 minute steps. I also found it advisable to interpolate in time when computing BTOs – before I was rounding the timestamps to the nearest minute, but now keep track of fractional minutes.
Another thing I have done has been to make a more careful study of the BTO and BFO values from the pre-IGARI phase (where they can be compared to ADS data), from during the AES reboot, and from the MH21 diagram. Aside from the instrumental artifacts that Inmarsat has noted, the BTO and BFO both seem to be robust and reliable.
@sk99: I assume you mean the magnetic track was constant and not the magnetic heading, i.e., the ground speed was affected by wind but the azimuth was not. I already have the wind and temperature data in my model, so no need to supply that, but thank you. I also use an integrator to calculate the path with a one-minute time step, which is I believe sufficiently accurate given the coarseness of the wind and temperature data and the mild slope of the magnetic declination.
Oops, yes – magnetic TRACK is followed. (I have magnetic heading as a mode as well, but it doesn’t do anything interesting.)
@Jeff:
Re: “decision to shift the search zone appears to have been heavily influenced by the BFO data (which) told them…the plane had…taken a slower and/or meandering course and wound up about a thousand miles from the initial search area.”
Corrections:
1. s21 is 1,500 – not 1,000 – miles NE of the original (= current) search location.
2. Absent path circuity near Sumatra, the BFO data COUNTER-indicates s21. Period. To claim the ATSB’s decision to move the search to s21 was “heavily influenced” by the BFO data is to completely misrepresent both the underlying science AND the ATSB’s own “spaghetti at the wall” cornucopia of rationalizations given in the April 1 column of Appendix A of its June 26 Report.
@ sk999;
What is the value of FFB (Fixed Frequency Bias) that you used?
@Jeff, anyone
Re +10kts, -10kts.
We have learned that, for certain flight modes, speed reduces with decreasing weight due to fuel burn.
What would be the weight reduction equivalent to a -20kts airspeed change?
Cheers
Will
@ MuOne:
Approximately:
20 kts = 4% of airspeed = 8% of weight
(Optimum airspeed is roughly proportional to the square root of weight.)
How We Can Tell How Fast MH370 Was Flying?
Simples: How fast it was flying north or south can be calculated from the BFO.
How fast it was flying east or west can be calculated from the BTO (the ping arcs).
Sk999 has advanced the art considerably by interpolating BTO and BFO values between the pings to produce a continuous path rather than one consisting of 1-hour straight segments.
Everyone (ATSB, Inmarsat, IG, Ulich, Cole) does the reverse calculation, assuming a track or speed, then calculating the BFO values at the arc locations, then modifying the assumption.
I didn’t the impression that sk999 was doing anything radically different. The interpolation remark seemed to imply use of high time resolution at ping times. I am sure sk999 will clarify.
BFO bias is more complex than a simple offset. The AES R and T signals bounce around different channels and frequencies, and it is clear that there are systematic offsets in the BFOs. I chose to use 36ED at the reference (this is the frequency used for ping rings 1-6). Frequency 36D3, one of the main R channel frequencies at the gate, is high by 4 hz, so I adjusted its values down by that amount. Frequency 36E3, the other main frequency, looks OK. The T channel frequencies are high by about 5 hz, but I have not used them in the final analysis. The single C channel frequency has an unknown offset – I decided to use the two sets of BFOs as is, and looked to see if they stood out in the final fit (which they did not.) Note that all these offsets were determined from the early phase of the flight when MH370 was either parked at the gate (before push-back) or in level flight. The final BFO bias is then 150 hz.
Regarding fine time steps and interpolation, I have advanced MY state of the art, but I suspect others have done it already.
In further regard to BFOs, it is worth discussing the behavior during the time between 16:28:15 and 16:29:41. Before this, the BFO is around 88 hz. There is a gap of about a minute time, then the next signal at at 16:29:17 has a BFO that is high by 10 hz. I first thought this might be unstable behavior, but then realized it coincides with pushback. From the voice communication transcripts we know that pushback was authorized at 16:27:45, and the request for taxi came at 16:32:13, so the plane pushed back and started its engines in that interval. My guess is that the AES frequency compensation mechanism was not working yet, so the jump of 10 hz was the full Doppler from the aircraft moving. We know that the plane used gate C1, so a pushback would move it NNW (at least initially), in the right direction to cause the frequency to increase.
@ sk999:
” so the plane pushed back and started its engines”
Perhaps the plane first starts engines while it is still connected to external power, then is pushed back?
Anyone:
Any answers to the following questions would be much appreciated !
1. Uncertainty of the Inmarsat ‘raw’ BFO values before/after ~ 18:25 ? +/- 30 hz ?
Any estimate of how much uncertainty exists in the (undisclosed raw values).
2. At the Inmarsat ground station, how is the received frequency calculated or the difference from the sent frequency calculated ?
What is the uncertainty of this frequency for small handshake messages ?
3. Compensator Algorithm.
How can the terms and parameters for this algorithm be independently determined/verified before/after ~ 18:25 ?
Is there a specific ‘bias’ term in the algorithm to correct for the partial compensation ?
Is there a specific plane altitude and rate term which is inactive ?
If there are any satellite specific position and velocity terms in the algorithm – would they work in handshake mode ?
Are there any default or last values which are used in the algorithm ?
4. Are there any other terms (non-satellite position, velocity terms) that could be added/activated/deactivated which could disguise/alias the apparent flight path
of MH370 ?
5. Assuming the compensator algorithm has existed since ~ 2000 and that Inmarsat is aware of the non-stationary motion of this satellite, what was Inmarsat – Chris Ashton trying to understand for the ‘analysis breakthrough’ ?
The North or South turn BFO difference is approximately 60 -70 hz (with the assumed compensator algorithm).
This difference would be ~ 0 for a ‘perfect’ compensater.
6. Is there any ‘lag response’ of the plane transmit frequency with the value that the compensator is calculating ?
Is there a plane transmit frequency control loop ? Is this a closed/open control loop ?
7. Can experts/hijackers make changes to the algorithm and or modify parameters from the front panel (of MITEQ ?)in the EE bay ?
Does this require a reboot ? Do front panel changes require some access code ?
8. Assuming possible hijackers are gaining access to the EE bay via the hatch door, can they do this fast enough such that the ‘Mayday’ button could not be activated in time by the pilot ?
9. Is it possible for hijackers to have gained access to the EE bay prior to the flight ?
Thank you.
@jeffwise: As we have discussed offline, I believe the anomalies you are seeing in the ground speed is an artifact of your assumptions that the ping arcs are exactly correct. A number of us have found paths consistent with a constant air speed or Mach number if you allow the plane to cross the ping arc within some variability as indicated by the expected error of +/- 9 km of satellite-aircraft range.
The drop in ground speed for the last segment (22:41 to 00:11 UTC) is explained by the drop in air temperature and the head wind at the more southern latitudes. This again is consistent with the constant Mach number assumption.
I have performed trade studies where I set the latitude at 19:41 and find the resulting true track paths that match the BTO and BFO values by varying the initial longitude, Ma number, and azimuth. For starting latitudes between 6N and 6S, the azimuth varies between about 174 and 196 deg and the Mach number is always between 0.81 and 0.82.
@Gysbrecht: A number of us numerically integrate along the path as @sk99 has done, which allows the effect of wind, temperature, and magnetic declination to be more accurately included in the model, and also allows the continuous variation of speed, track, or any other variable. However, in my approach, I only try to match the satellite data at the ping times.
Henrik has a model in which he fits curves to the BTO and BFO data and he produces paths that match the curve fits at each instant of time and not just at the ping times. Of course, he has to make assumptions about the values of the BTO and BFO between the ping times, which is not easy if there is a course change. I am not aware of anybody else that has a model of this kind.
@sk99: I have not forgotten about the magnetic track calculations. I will try to do that today after I finish up some other work. I already have that navigational mode as an option in my model so it should not take too much time.
@sk99: I checked your magnetic track path, assuming a turn south from IGOGU. I calculate a bearing of 186.4 deg (magnetic), a Mach number of 0.742 and an endpoint of (-33.7,94.4), which is not too far from your result of (-33.5,94.4). The RMS BFO error is 3 Hz (bias of 150 Hz). However, the RMS range error for the pings is 16.2 km (54 us).
The upshot is I cannot confirm that this path matches the BTO data, although it does seem to match the BFO data. Since our endpoints and magnetic track are close, I suspect our path integrators are similar. Perhaps our ping arc assumptions are a bit different.
It’s a number crunchers wet dream!
Greg – far too many questions.
VictorI
Sorry to not be clearer – 186.3 is ground heading. Magnetic is 187.2. See if that helps. Also, because the velocity is lower than standard, I lowered the altitude to 10 km (33,000 feet) on the grounds that it might be more fuel efficient.
One final point – I do not include the 24:11 point, since as others have found, a lower speed is needed for the final leg on these particular types of tracks.
@sk99: Yes, without including the 00:11 point, it is possible to find magnetic tracks that fit. However, there are rhumb line paths that do not require a drop in Mach number before 00:11. Even with constant Mach number, the ground speed falls in the last leg, because the drop in temperature reduces the air speed and the head wind reduces the ground speed. For this reason, I place a higher probability on paths that do not require a drop in speed before 00:11, unless the plane is following an ECON speed profile.
@VictorI, Thanks for taking the time to analyze this technique. In reply, I would say that, as I write in the piece, you can certainly find paths that are consistent, within a certain margine of error, with constant-Mach throttle settings. But in fitting the data in this way, are you eliminating a legitimate signal? The ping rings don’t have to be exactly correct to generate the pattern I’ve noted; they just have to be wrong in more or less the same direction. For instance, I’ve tried this idea with different people’s ping rings, which are bigger or smaller by up to 5 or 10 miles, and they all produce a similar effect.
At one point I was thinking about titling this post “Is MH370 Trying to Tell Us Something?” because I feel that there’s an interesting pattern in the ping rings that no one has brought to public attention, and not coincidentally this method generates a speed range that is broadly in agreement with the documented speed pre-18:22 and with Brian Alexander’s 19:41-to-20:41 analysis. I see a legitimate philosophical difference between your position in mine: should we start with the assumption that the ping ring data we have is more or less accurate, and ask what we can deduce from it, or insist that the plane must have been flying straight at a single Mach setting, and find the interpretation of the data that best fits that assumption? Both approaches have their merits. To make my argument more robust would require rigorous analysis of BTO offsets and consequent margins-of-error, which other IG members have been working on over the recent weeks; perhaps they will reach a sufficient level in the near future that they could shed light on this topic.
@jeffwise: I don’t think it is necessary to insist the plane is flying straight and at a single Mach number. Rather, I am trying to find paths that are consistent with autopilot modes, which include paths of constant Mach number and constant true tracks. We know from the satellite data obtained when the plane was on the ground that the BTO values have scatter, so I (and most other modelers) allow the paths to vary from the exact BTO within the range of expected scatter. In fact, you can make the argument that it is very low probability that the BTO values are exactly matched at the ping times.
And the knives come out.
Ben Sandilands | Nov 24, 2014
“Is Australia being taken for a fool?”
http://www.twitlonger.com/show/n_1sim6tj
Niccolò Machiavelli is clapping.
Who’s going to out whom?
I get the feeling as every neighbour of Malaysia seems uncooperative … Malaysia got themselves in some kind of multi way “sit-down” with them. So in order to keep the peace in the region they can’t go after the hijackers as the hijacker have threatening operatives in the neighbouring countries… Many countries say no radar, other countries deny eye witness accounts etc etc
I see ATSB Crash Investigator Peter Foley – in addition to making his thoroughly distasteful “champagne on ice” comment – is also running their ridiculous debris-to-Indonesia-and-not-Australia claim back up the flagpole.
Is anyone saluting?
I’ve finally figured out the common thread running through the various aspects of the MH370 misinformation campaign conducted by the US government/media complex in March/April:
– pumping up “wild altitude changes” reports
– pumping up the “fisher eyewitness” account
– “confirming” the co-pilot’s cell phone connection with a telco tower
– “confirming” the authenticity of acoustic pings at s21
The common thread: they all SEEMED to corroborate the primary radar track and/or post-primary radar Inmarsat signal data.
Given…
– the lack of ANY independent physical evidence to support EITHER track
– that EACH item above has proven, under actual scrutiny, to be INCOMPATIBLE with the track data
– the implausibly bad decisions taken by the JIT over the past 8+ months
– the cold response to data requests from independent analysts whose sole aim is to expedite the plane’s recovery
…I think those analysts should start seriously exploring scenarios in which ONE or BOTH tracks have been fabricated.
@Brock: The only complicity I see on the part of the US, UK, and Australia is their unwillingness to expose all of the lies of Malaysia and perhaps other ASEAN member states. My guess is the quid pro quo is access to military bases and intelligence to fight terrorism and to counter the expansion of Chinese influence in the region.
YES indeed Brock.
Fabrications.
Remember what the NYT’s Keith Bradsher’s said? It couldn’t have been more clear: the game being played involves the RADAR data.
Nihonmama
Posted October 19, 2014 at 10:50 PM
“Their conclusion, reached in the past few weeks, helped prompt the decision to move the focus of the search hundreds of miles to the southwest…
The main evidence for the conclusion lies in a re-examination of Malaysian military radar data and in a more detailed analysis of electronic ‘handshakes,’ or pings…
…a comprehensive international review has found that the Malaysian radar equipment had not been calibrated with enough precision to draw any conclusions about the aircraft’s true altitude.
‘The primary radar data pertaining to altitude is regarded as unreliable” said Angus Houston…Martin Dolan, the chief commissioner of the Australian Transport Safety Bureau, agreed with Mr. Houston. ‘There’s nothing reliable about height’…
Mr. Houston and Mr. Dolan declined to discuss any details about the Malaysian radar readings…
SO THE DISMISSAL OF THE RADAR ALTITUDE DATA PROMPTED A CHANGE IN THE FOCUS OF THE SEARCH.” (CAPS mine).
Did you get that?
Without a peep (in that article) from any Malaysian officials, and from the pulpit in Australia — sans any details as to who conducted the “comprehensive international review” of Malaysia’s military radar system — or an explanation of the technical basis for determining that Malaysia’s system was not “calibrated with enough precision” — it was announced that Malaysia’s military altitude data was so imprecise that it was being dismissed. Which then allowed the authorities to CHANGE the SEARCH focus.
http://www.twitlonger.com/show/n_1sd7gtn
Re: ATSB Oct. 8 Analysis Update: performance limits are depicted under two scenarios:
Fig.2: Turn south at 1828
Fig.3: Turn south at 1840
At constant 500kgs: if you turn south 12 minutes = 100nmi sooner, then you hit the 19:41 arc 128nmi further south. Because (trig).
If you ENTER the Inmarsat merry-go-round 128nmi further south, you EXIT it 183nmi further SW along the 6th arc. Because (trig).
For perspective: 183nmi is 3.5 degrees of longitude along the 7th arc.
Why is this important? Because, if ATSB were portraying these charts honestly, Fig.2 should look exactly like Fig.3, but with the “Inmarsat arc dial” rotated about 8 degrees clockwise. Each flight path (FL250, 300, 350, 400) should exceed the 7th arc by the same amount in each figure, and be about 183nmi SW (for FL400 – slightly less distance for the others, if their speed reduction is assumed to occur PRIOR to crossing the 19:41 arc) around the arc – because total distances travelled (and speeds, and altitudes) have not changed. AT ALL.
Fig.2 does exhibit this property (3 degree clockwise rotation of Fig.3) in general. But careful inspection shows two clear deviations:
– FL350 is truncated (doesn’t fly as far past the 7th arc as it did in Fig.3), and
– FL400 is not plotted at all (though logic requires it MUST appear, 183nmi WSW of its position in Fig.3, and exceeding the 7th arc by the same proportion)
It may not come Thursday. Heck, it may not come until well into 2015. But I predict another “refinement” in our future: the priority search area moving SW yet again, due to “brand new insights” into MH370’s performance limits. And Dr. Ulich’s path (finally) getting the attention it deserves.
Yet another step along a path which seems with increasing clarity to be an exercise in RUNNING OUT THE CLOCK.
How did Malaysia just get a UN SECURITY COUNCIL seat if the obstructing of the MH370 investigation is all in its lap?
And which country is the largest financial supporter of the United Nations?
Hello All,
I am happy to find here a number of individuals, with whom I had a chance to discuss MH370 at Duncan’s blog several months ago.
I did not give up the idea of the possibility of other flight modes, particularly a “Constant thrust” mode. Recently I achieved a fairly good BTO/BFO agreement by employing a simple ODE-based model, which accounted for a really constant thrust (in terms of N), Coriolis & wind force (wind is interpolated GDAS1), as well as the approximate linear change in the aircraft’s mass. Achieved BTO residuals correspond to the ping rings errors up to about 1 km, and the largest BFO error about 2.5 Hz. The terminal point for such a scenario is predicted to be almost exactly where the 7th arc crosses the Broken Ridge (right in the deep trench). Specifically that area is not searched yet, but included into ATSB/Fugro plans.
It is interesting that a good match is only valid for the assumed constant altitude at around 4700 m (say 4300 to 5000 m). The other interesting thing is that virtually any additional improvement in physical formulation further reduces BTO/BFO errors (coincidence?). Finally, without accounting for wind impact (i.e. Coriolis only) the terminal point is the location of Chinese Ping, but BTO/BFO residuals are getting worse.
However, the main conclusion I came to, is a sad thing: the terminal point depends on the hypothesis about flight mode, and provided BTO/BFO data are not helpful here. It is likely possible to suggest another flight mode/model, and achieve a good BTO/BFO match again, resulting in a different terminal point.
Can anyone tell me why the northern arc is discarded? Because of BFO data? I realized it is a wrong answer. If one assumes a plugoid mode of the flight, possibility of which is indicated by the radar data, periodical vertical speed enters the equation. It is not compensated by the aircraft’s terminal, so the impact of vertical component on BFO is comparatively large. So, should the northern arc be brought back onto the table?
Speaking about a “constant thrust” mode a lot of things depends on how the stability of the aircraft is controlled. I would like to learn more how the altitude, response to cross-wind (if any), response to the change in mass, and thrust itself are controlled in this mode. If anyone knows ‘quick’ answers, these would be greatly appreciated.
Best Regards,
Oleksandr.
It turned out my propagator code still had some approximations left over from spherical earth days, so I have hopefully cleaned those out. The slightly modified track (with fits as good as before but with slightly modified parameters) is here:
https://docs.google.com/spreadsheets/d/1CzSkN2ErnagOEOP8ktZ21vgC5WmnrAWBpr88P8GH-3w/pubhtml
If anyone wants to do a detailed comparison at one particular point in time, I can print out all the parameters I calculate (about 48).
In the spirit of the theme of the article (i.e. determining the speed of the aircraft), it is worth pointing out that the first leg after the turn at IGOGU (assuming that that is where the turn happened) does just that – however, not in the way that the article envisages. The first full ping at 19:41 occurs when the aircraft is traveling essentially parallel to the ping ring. What that means is that the BTO says nothing about the location or speed of the aircraft, but it tightly constrains the heading. Once you know the heading, the BFO gives you the velocity. If one ignores all the later data, one finds a velocity of 400 knots. My velocity obtained using the full track is considerably higher – 451 – and misses the measured BFO by 5 hz. (Caveat emptor – I have adjusted the BFOs for systematic offsets between different frequencies, as described in a previous post. YMMV.)
@ sk999 Nov 24 7:57 PM:
I cannot reproduce your arithmetic. Just to illustrate my method of calculation per my post of November 23 at 6:30 AM:
Location IGOGU N7.517 E94.417 at 18:40 UTC
Yap’s EXCELlent BTO&BFO calculator gives:
BFO = 128.03 + 0.08887*Vy (Hz)
Where Vy = latitudinal velocity component (N positive) in knots
Vy = – 450.4 kt for BFO = 88 Hz, or – 7.5 degrees of latitude per hour.
Latitude at 19:41 is then N7.517 – 7.628 = S0.108
The longitude of the 1941 arc at latitude S0.108 is E93.7
Therefore the longitudinal velocity component Vx = (93.7 – 94.417)*60/1.017 = – 42.3 kt
The resulting groundspeed is 452 kt on heading 185.4 degrees.
This assumes a constant speed and and track between 18:40 and 19:41. The preferred method is to do similar calculations for smaller intervals using interpolated values of BFO and BTO. Comments welcome.
Geysbreght,
I cannot speak for the equation you are using; however, I warned of offsets – my bias may be 4 hz lower than what other people assume, which would account for the difference.
@ sk999:
On Nov.23 at 8:23 AM you wrote: ” The single C channel frequency has an unknown offset – I decided to use the two sets of BFOs as is, and looked to see if they stood out in the final fit (which they did not.) (…) The final BFO bias is then 150 hz.”
In my example I only used C-channel and R-channel BFO’s. The default bias in Yap’s spreadsheet is 150 Hz (which I used).
Correction to my post of 7:46 AM: The only BFO used in the example is 88 Hz at 18:40, the average of 86 C-channel messages received between 18:39:55.354 and 18:40:56.354.
To explain the equation in my post of today at 5:30 am:
For location IGOGU N7.517 E94.417 at 18:40 UTC, bias 150 Hz, the calculated BFO is 128.03 Hz at zero speed.
For 500 kt groundspeed on headings 0, 90, 180 and 270 degrees the BFO is 172.46 Hz, 128.46 Hz, 83.59 Hz and 127.59 Hz, respectively.
The difference between 500 kt North and 500 kt South is 88.87 Hz, i.e. 0.08887 Hz/kt GS.
The difference between 500 kt East and 500 kt West is 0.87 Hz, i.e. for practical purposes the BFO is insensitive to east-west components of groundspeed.
The above BFO values were obtained with Yap’s calculator. The values obtained with other calculators may be slightly different, but the same principle should apply.
@Gysbreght: I have checked your values of BFO for FFB = 150 Hz for IGOGU at 18:40. At 500 knots, my values are: 173.4, 129.5, 84.8, 128.6 Hz for true tracks of 0, 90, 180, and 270 deg, respectively. These are close to your reported values.
Victor
If the aircraft can be shown to have travelled in a straight line after clearing Sumatra, then the question of deliberate action is substantially proved
A 777 has autopilot modes which revert to basic magnetic heading once the programmed Flight management computer tracks reach a route discontinuity i.e. The programmed route ends.
If the aircraft was flying on a southerly magnetic heading (or track) from Sumatra, the changes in magnetic variation as it progressed would have caused the track made good to curve towards the east substantially as the variation around Sumatra was around zero, and the the variation near where the aircraft is thought to have crashed is 25-30 west.
There are only two ways to make a 777 follow a dead straight line in this scenario and both require knowledge of the navigation system.
One is to program a waypoint into the FMC. The other is to switch the aircraft heading reference to TRUE, and fly a true heading for the entire flight.
Neither can be done accidentally.
Therefore if it can be established that such was the case, then many questions about this flight can be dealt with in the light of the knowledge that the flight south was deliberate.
Watching the image, it looks like the auto pilot was set to flight litteraly to geografic south pole.
This is consistent with a deliberate plan.
http://s9.postimg.org/kj78p109b/ocean_currents_vs_ping_rings_flight_paths.jpg
The 500kt flight paths south, published by both Jeff Wise and Duncan Steel, both also happen to accord perfectly, with the sea-current-adjusted crash-site implied by all of the debris sighted in the SIO by various nations (like China, France, and Thailand) in March 2014…
which debris also must have been washing ashore near Perth, Reunion, and Mozambique, by virtue of the SIO ‘gyre’ circulation into which the fragments were entrained.
Thus, numerous lines of evidence appear to point to an impact near 85E,45S ballpark plus-or-minus a degree or so… After a flight at a remarkably constant 500kt from the passenger-incapacitating U-turn at 1:22-24am onwards, to and perhaps past 8:20am or so…
the distance of this suggested crash site, past the final ping rings, may require either a human-controlled glide down, or an auto-piloted plugoid descent, as it appears to be incompatible with any rapid spiral descent…
The best-fit 500kt flight path southwards appears completely inconsistent with a magnetic-south auto-pilot setting. (Magnetic South is located south of Australia, so that the a/c would have slewed eastwards and ‘tried’ to ‘duck under’ Australia, to anthropomorphize.)
Rob has suggested a generally similar flight path at Mach 0.81, as well as the calculations & contrail observations of Dr. Ulrich implying a LRC at Mach 0.84 towards the 7th ring near 40S, 84E.
Explicitly, sited contrails, forum user Rob, Duncan Steel, Dr. Ulrich, & Jeff Wise all wind up with a tightly clustered family of routes towards the ballpark of 40S, 84E… And which, if followed a further 700-800km, would also intersect the debris fields supposedly sighted via satellite during the first few weeks of the investigation… Which debris fields were entrained in the narrow band of SIO sea currents which naturally circulate past all suspected and confirmed wreckage finds near Perth, Reunion, and Mozambique…
Thus, rigorous theories, reliable observations and confirmed findings all coincide remarkably… Even additionally with an ultimate human controlled glide (up to 150km from FL430) scenario, given the range from 7th ping ring to satellite sighted debris (approximately 750km).
So, according to the requirements of scientific method, there wouldst must be one more logical deduction to derive from the available data, for this hypothesis to metaphorically stride from the 7th ping ring to the debris field a further 5 degrees of arc southwards. I suspect that some form of human input could , and also would be required to , account for that speculated connection…
Rising cabin temperatures in dawn sunlight, increasing cabin pressure as plane descends on one engine, warning alarms and jarring turbulent motions, jolt a hardy and fortunate few into organized action… Siphoning fuel out of the APU to restart main engines and fly on fumes for a further hour, on minimal power??? Perhaps the plane was rescued from a stall, by the copilot, who arguably replied on emergency radio at 1:30am, broadcast SOS thereon at 1:43am, and tried to phone at 1:52am ?? Perhaps the plane was still airborne after 9am, albeit on very limited electricity?
http://i.imgur.com/YAALZID.jpg
https://en.wikipedia.org/wiki/Ninety_East_Ridge
As is immediately obvious from the images of the OP, all of the previously mentioned best fit flight paths share the very curious feature, of traveling straight down the spine, of the 90E ridge, which marks the boundary between E and W parts of the IO. That mirrors the early flight behavior of MH370 tracking radar boundaries.
Perhaps this may be attributed genuine significance? Perhaps suggests FMT at IGOGU over this natural geologic feature??
@Erik Nelson, You wrote, “rigorous theories, reliable observations and confirmed findings all coincide remarkably…” Are we talking about the same case? No confirmed aircraft debris was spotted from the air. One piece of wreckage has been confirmed as having come from MH370 but as has been suggested here it is problematic. The other two pieces from Mozambique are even more problematic. Dr Ulrich’s endpoint was never considered plausible from a fuel standpoint. Etc. Oh, and while I believe that the IG’s interpretation of Inmarsat data is correct, insofar as it predicts an endpoint within the current search area, I have argued that the data could also be interpreted as indicating that the plane went north, if hijackers changed a parameter in the Satellite Data Unit. So, to make a long story short, the idea that the plane went south per the DSTG/ATSB/IG is far from a foregone conclusion.