One of the most misunderstood insights into the riddle of MH370 is how the plane’s final path can be derived from Inmarsat BTO data alone.
Recall that the data, which was generated after someone on board caused the Satellite Data Unit (SDU) to re-logon to the Inmarsat Satellite 3F-1 over the Indian Ocean at 18:25, comes in two flavors. The first, the Burst Timing Offset (BTO) data, reveals how far the plane is from the satellite at a given time. This can be mathematically converted into a set of “ping rings” along which the plane must have been at a given time. The BTO data is very well understood and fairly precise, providing an accuracy of within 10 km.
The second, the Burst Frequency Offset (BFO) data, is more more complicated and much fuzzier than the BTO data; its inherent uncertainties are equivalent to a position error of hundreds of miles. It doesn’t have a single physical correlate but is related to how fast a plane is going, what direction it is headed, and where it is located.
For a time after MH370 disappeared, searchers hoped that they could combine these two data sets to identify the area where the plane issued its final ping. After months of work, however, they determined that this would be impossible. The BFO data is just too vague. However, along with the bad news came some good: it turned out that by the clever use of statistics they could figure out where the plane went using the BTO data alone. The methodology developed by Australia’s Defense Science and Technology Group (DSTG) and explained in an ATSB report entitled “MH370 – Definition of Underwater Search Areas” released last December.
Many independent researchers do not understand the technique and believe that it is invalid. For instance, reader DennisW recently opined that “The ISAT data cannot, by itself, be used to determine a flight path. One has to invoke additional constraints to derive a terminus.” But I believe that the DSTG position is correct, and that one does not need to invoke arbitrary additional assumptions in order to calculate the plane’s track. I’ll explain why.
First, some basics. Imagine that you have two ping rings, one created an hour after the other. For the sake of simplicity, let’s say the rings are concentric, with the later ring’s radius 300 nautical miles bigger than the earlier one’s. Let’s further assume that the plane crossed some arbitrary point on the innermost ring. If that’s all we know, then the plane could have taken any of an infinite number of routes from the first to the second. It could have travelled radially directly outward at 300 knots. Or, if traveling straight at 400 knots, it could have turned left or right at an angle. Or, it could have traveled faster than 300 knots on any number of meandering paths. So, the fact of the matter is that this simple understanding of the plane’s situation indicates that it could have traveled by wide number of paths and speeds to a wide range of points on the second arc.
However, there are some pecularities of commercial aviation that narrow the possibilities considerably. The most important is that planes can only travel in straight lines. They can turn, but in between turns they will fly straight. Knowing this vastly reduces the number of paths that MH370 could have taken between 19:41 and 0:11. It could not of simply meandered around the sky; it must have followed a path of one, two, three, four, or more straight segments.
Through the marvels of modern computing, researchers can generate a huge number of random routes and test them to see which fit the observed data. It turns out that if the plane flew straight in a single segment, the only routes that match the data are those that are fast, around the speed that commercial jets normally fly, and end up over the current search area. If you assume that the flight involved two straight segments, it turns out the ones that fit best are those in which the two segments are nearly in a straight line and are also fast and wind up over the current search area.
If you suppose that the flight after 19:41 involved a larger number of segments, your computer’s random generation process will be able to come up with valid routes that are neither straight nor fast, and do not end up in the current search area. But to come up with such routes, the computer will have to generate many, many others that do not fit. So it is extremely unlikely that by random chance the plane would have happened to travel a slow, curving route that just happened to “look like” a straight, fast route.
“Well,” you might object, “presumably whoever was in control didn’t fly randomly, they had a plan, so modeling by random paths isn’t appropriate.” But a plan of unknown characteristics is equivalent for our purposes to a random one. After all, there is no imaginable reason for someone to fly a plane over empty ocean in the dark at a slower-than-usual rate, making slight turns every hour or so. (Before you say that they might have done it to throw searchers off their trail after the fact, bear in mind that whoever took the plane would have had no way to know that Inmarsat had started logging BTO values a few months before, let alone imagine that they would be able to conduct this kind of analysis.)
When DSTG ran the math, they came up with a probability distribution along the arc that looks like the image at top.
Worth noting that the peak of the curve, and the lion’s share of the area under it, lie in the southern half of the search box, but it also has tails that extend past the box in either direction.
When the search of the seabed began, many expected that the plane would be found in short order. When it wasn’t, the burning question then became: how far out from the 7th arc should we search? A one-dimensional question had now become a two-dimensional one. Based on past loss-of-control accidents and flight simulations, the ATSB decided that an out-of-fuel 777 with no pilot would enter a spiral dive and impact the surface within 20 nautical miles. Mapping the two probability distributions (i.e., where the plane crossed the 7th arc, and where/how far it flew after that) yielded the following probability distribution:
I believe that we have to take the image above with a grain of salt, as I don’t think it is really possible for a plane to fly more than 40 km by itself. It’s generally agreed that the only way the plane could have plausbily gone further than that is if the pilot was conscious and actively holding the plane steady in a glide, in which case it might have gone as far as 100 nm.
A few months before the ATSB publlshed this analysis, a further set of information about the impact point of MH370 became availalble: the plane’s right-hand flaperon washed up on Réunion Island. Reverse-drift analysis was performed by several independent groups to determine where the flaperon might have started its journey. The German institute GEOMAR came up with the following results:
As you can see, the probability distribution hardly overlaps at all with the probability distribution derived from the BTO data; it only touches at the northeastern corner of the search box. Drift analysis performed by other groups reached a similar conclusion. Using a branch of mathematics called Bayesian analysis, it’s possible to take two probability distributions and merge them into a single one. I’m not a mathematician myself, but intuitively one would surmise that given both the BTO and the drift-model data sets, the new peak probability are should lie somewhere between the northern end of the current search box and Broken Ridge.
The ATSB report disagreed, arguing that the drift analysis
… made no meaningful changes to the ATSB search area due to the relative weighting of the significance of the drift analysis in comparison with the analysis based on the satellite data. While this debris find is consistent with the current search area it does not provide sufficient information to refine it.
What this means is that the ATSB considers the BTO data and its analysis “hard” and the reverse-drift analysis “soft,” because the random motion of ocean currents introduces a large amount of uncertainty. However, the reported also noted that “if additional debris is identified it will be included in the analysis to provide further information on the location of source areas.” Indeed, after the report came out other pieces of debris were found, and drift modeling of these pieces be used to refine the search area. Indeed, after I published last week’s guest post by MPat, reader Ge Rijn pointed out:
Over those 20 years in MPat’s model only 7 out of 177 buoys landed in Australia. Those 7 all passed the search box under 36S… [this] points clearly to the trend the more south you go under ~36S the more likely it becomes buoys (debris) will land on Australia and the more north you go above 36S the less likely it becomes buoys~(debris) will land on Australia. This is also because the more south you go under ~36 the currents tend to go further east and the more north you go around 36S the currents tend to bend stronger to the north avoiding Australia. And this is exacly what the facts about found debris shows us till now.
Note that 36 degrees south is just shy of the northern end of the current search area; as Ge Rijn observes, historical drift data suggests that if the plane had crashed south of this latitude, debris should have been found in Australia, which it obviously hasn’t.
The size and species mix of barnacles growing on ocean debris could provide clues as to which waters it floated through; oxygen isotope analysis can provide information about the temperature of the waters that it floated through. As far as I know, no such analyses have been conducted. For a long while now, the ATSB’s weekly update reports have included the phrase “In the absence of credible new information that leads to the identification of a specific location of the aircraft, Governments have agreed that there will be no further expansion of the search area.” The fact is, though, that further information is available, and it could be used to determine which of the two possible explanations is more likely: that the plane passed over the current search area and was held in a glide, or crossed the seventh arc further (but not too much further) to the northeast.
@Jeff, fair enough. I appreciate it. Thank you!
@Brian
The aircraft had to have had an almost pure South heading at 19:40 to produce the observed Doppler residual (as I recall). I’ll run some numbers tonight to verify. Just drove from the beach house to the ranch, and I have a few messes to clean up here.
@DennisW (Hope you dont throw me in Clancy bag;)
for the record, yet another group in the game??
fairly more advanced that my loved enemy, this cult has over 10M units worldwide, and as we can see also ability to induce things like armed raid on government, yet not confirmed direct command and control – all the sheeps are already probably well self-organized though…
http://www.stopgulen.com/
The only thing that gives the notion of the “northern” FMT on the “N571 – Mekar – Nilam – Igogu” track any traction, is the Malaysian radar, which is totally uncorroborated by any other source, and which I don’t trust or accept.
Have any of the mathematicians run the BFO’s with variable ROC’s for a “southern” FMT on the “L774 – Merim – Uprob” track (which is an infinitely more sensible track, if it was a “debiberate” “planned” event.) ?
There is also a second, plausible way, that the aircraft could have been on it’s way to Uprob.
What if there was an emergency between Igari and Bitod, and what if the crew intended to return to KL, and what if they turned, with the intention to intercept the R208 for the return at Upron, but “in the heat of the moment”, accidentally selected “Uprob” instead, and became incapacitated soon after ?
@ROB
I was unable to make sense of the ISAT between the time the plane passed over the Malay peninsula and the FMT. I always start my paths at 19:40. Will take a look at 18:40 relative to direction.
Part flap in Canberra.
http://www.foxnews.com/world/2016/07/18/suspected-mh370-wing-flap-reaches-australian-investigators.html
Note sea state from RNZAF Orion with ship as reference, date unstated.
@ Gysbreght. Previously I have been warned about posting Boeing copyright documents. The diagram is at the Training manual, 27-51-00 p53 and Maintenance Manual 27-51-00 p57. In the second it is captioned “Boeing Copyright Unpublished Work”. In the first the same diagram bears no such warning. Advice from anyone please?
@Ge Rijn. I do not think the MH17 outer flap part came off in flight. To the contrary the investigation report indicates this and other wing parts were near the wreckage of the aircraft forward section, which was burnt. The flaperons and inner flaps seem to have been burnt (the report apparently misidentifies this item as an inner flap).
What I was getting at is that its comparatively undamaged state is indicative that the MH370 parts (from outer flap and flaperon) might have been ejected likewise during a high speed crash where there is no fire. The trailing edge damage on the outer flap part could have happened then too, though the flaperon t.e. damage looks inconsistent with that, more like flutter or a ditching so contradictory.
Yes the lack of spoiler actuators could make a difference in the MH17 case, depending on whether either was thrown downwards as much as forwards in impact shock, supposing a high speed crash in both. The MH370 leading edge does seem to have hit the actuating structure, “outboard flap support mechanism” being the Boeing term.
Thanks for the close up of the l.e. damage
@All
An intersting observation that I have made on this fascinating MH370 story is that there seems to be 2 main camps of theory believers.
1) Those that think MH370 was not a conspiracy and it
crashed in the SIO.and most likely the Captain did it.
2) Those that think MH370 was a conspiracy and it was sophisticatedly hijacked and was flown to the Maldives.
[rest of the comment deleted by JW. Ken S, no one who has any technical understanding of the MH370 data believes that the plane went anywhere near the Maldives. To assert that is simply misinformation. To be clear, I do not maintain this blog as a forum for any wild speculation that happens to fly into someone’s head. This is about the scientific assessment of actual data.]
@Rob @all
Now the outboard flap piece has arrived in Canberra.
It seems it has gone straight to Australia instead of first to Malaysia as the other pieces (except flaperon) which is a good thing IMO:
http://www.nbcnews.com/news/world/possible-malaysia-airlines-mh370-debris-found-pemba-island-n611421?cid=sm_twitter_feed_world
@jeffwise said:
‘@Julie, I don’t want to discuss methods but now that I’m alerted I have ways to tell whether it’s from you or not, and I’ll keep an eye out.’
Jeff, Can I also suggest that you put the ‘Leave a Reply’ section on a https:// (secure) page – there should be plugins available for that.
That would prevent anyone monitoring/capturing users’ email addresses and user names that are being entered on your site in plain text.
@Middleton, Thanks for the tip, I’ll look into that.
@Jeff
Ok Jeff, this is your blog and you have every right to censor me and manage it as you see fit.
I will keep my comments based more on the scientific aspects, data , and try to explain the technical aspects more clearly in my theory so technical people can wake up and get this.
Cheers,
@Brian A.
Yes, I was looking for a minimum possible ground speed at 19:40 which is indeed around 403 knots at a heading of 180. (Aircraft assumed close to the equator.)
I do not recall what heading your analytics assumed.
For headings on either side of 180, I get something like the following (i.e. simple reciprocal cosine scaling):
180 +/- 10 ~410 knots
180 +/- 20 ~430 knots
180 +/- 30 ~465 knots
180 +/- 40 ~526 knots
@DennisW – you said ”
I was unable to make sense of the ISAT between the time the plane passed over the Malay peninsula and the FMT..
”
Which is also my problem with any path to the SIO. The data chain must be consistent from between IGARI and BITOD to FMT then to final fuel.
@David
Hopefully soon the ATSB will come with a report on the Pemba-piece.
They will certainly be able to determine how the piece seperated IMO.
At least now they have a similar piece as the flaperon in their hands without the constrictions of a criminal investigation (as has the French investigation on the flaperon).
I expect the outcome of this investigation on the outboard flap section to be decisive in which attitude the plane entered the water and at which ~speed.
In other words; IMO it’s going to tell how, most probably, the last part of the flight and the crash took place.
@Ge Rijn
I expect nothing from the Aussies. Where are the bioforensics on the pieces they already have? Nada.
The ATSB is not charged with releasing such information. It goes to Malaysia, and nothing is heard about it. I would wonder if the French have provided bioforensic info to Malaysia relative to the flaperon finding.
@ Ge Rijn. Thanks. Yes, though the reconstruction, as distinct from identification, might take a while.
https://www.malaysiakini.com/news/348966
This quotes the media release as saying the ministers are meeting on 21st, 22nd July. Maybe right but it doesn’t.
https://www.atsb.gov.au/media/5770765/dca-atsb_debris-examination_mh370_18july2016.pdf
@Ge Rijn. PS, for a reconstruction I hope they get access to the French flaperon findings.
@DennisW
I expect them to come with their own final report on this piece and the other pieces.
They will report them first to Malaysian officials I assume but they have their own responsebility in this regard independent from Malaysia.
Just like the NTSB was involved in similar investigations. With sometimes very conflicting conclusions from the countries who lead the investigation (EgyptAir/SilkAir suicide crashes f.i.).
If Malaysia will not release their conclusions I don’t expect the ATSB will assist in covering up for them.
I assume they allready have a lot of information, also on the bio-forensics.
They are only not going to reveil it to the public as long the investigation is ongoing.
Just like the French will not do (on different grounds).
But they won’t let Malaysia dictate them what to release or not in the end.
So, I’m not concerned or distrusting about that at all.
As @David says; it might take a while but I’m sure the ATSB will release all their findings to the public as time comes.
https://postimg.org/image/s4v87qx5j/
Dr. Bobby Ulich has suggested two generally similar routes:
early FMT onto a 192-deg TRUE TRACK overflying Maimun Saleh WITN airport
early FMT onto a 192-deg track through waypoint IGEBO and extending straight through conspicuous contrails off the coast of Indonesia, and in the far SIO
IF Dr. Ulich’s contrails drifted west, due to winds aloft, by approx. ~10nm in the approx. ~30min between MH370’s passage through the area, and the capture of the satellite images…
THEN Dr. Ulich’s “Maimun Saleh” path reconciles with his best-fit 192-deg TRUE HEADING route…
and implies, that the a/c turned off of N571 (or very similar route) at approx. 18:28, veering onto a SSW track at 192-deg…
towards waypoint MUTIA, a waypoint associated with landing approaches to WITT Banda Aceh airport.
Dr. Ulich may also have identified the contrail resulting from the FMT off of N571 towards MUTIA. The contrail accords very well with the FMT depicted for his best-fit 192-deg TRUE TRACK route, especially allowing for wind-induced deformation, as well as drift, of the contrail over ~30min from generation to imaging,
Dr. Ulich states:
=================
It seems quite fortunate in hindsight that the Satellite Data Unit is communicating just when the aircraft makes a turn. This may not be coincidental. It would seem plausible that the time for making a (third?) landing attempt was growing short for several reasons, not the least of which was that the aircraft was nearly abreast of the last airport(s) available for an emergency landing before heading out to open sea. Therefore it appears that actions were taken, and two of those steps appear to be first restoring electrical power (thus rebooting the Satellite Data Unit) and then turning the aircraft to the nearest airport (Maimun Saleh). [[to MUTIA to WITT ?]]
The route which best fits the satellite data with steady true air speed passes directly over the Maimun Saleh Airport (without descending). [[over MUTIA ?]]
I infer that the flight crew made a purposeful turn and headed directly to it. This route is in the process of turning between 18:27:00 and 18:28:36 UTC… The initial bearing to Maimun Saleh Airport [[MUTIA ?]] after the turn is 192.36 degrees, and the approximate time of passage over that airport is 18:34:23 UTC on March 7, 2014.
IF the a/c overflew waypoint MUTIA on a heading of ~192-deg at approx. 18:35…
THEN it would have (very nearly) overflown waypoint NADIN, on the same heading, at approx. 18:43, when unknown parties may have detected a faint “cabin disintegrating” distress call & request for landing.
Whereas w/p MUTIA is the NW waypoint associated with landing approach to WITT Banda Aceh airport, so NADIN is its SW landing waypoint. Failure to contact Indonesian authorities, and rapid depressurization & resulting crew incapacitation from fracturing of the fuselage, could account for an implied failure to turn hard to port onto a ENE approach vector towards WITT BAC, and a resulting continuation of SSW velocity vector, out into the deep SIO, on a ~192-deg TRUE TRACK (or great circle ??) route.
Inexpertly, perhaps the acting pilot(s) preferred to land at WITT BAC on a NNW heading, approaching from the south, fearing re-ignition of a left-wing / left-engine fire amidst east-to-west crosswinds ??
@Ventus45 said;
“accidentally selected “Uprob” instead, and became incapacitated soon after ?”
In which case the aircraft would have flown to UPROB – directly across
the Strait and over north Sumatra. The Indonesians say it didn’t fly
across their airspace.
@buyerninety
The Indonesians are telling the facts that they have.
@all
Multiple _official_ paths MH370 took can be calculated. I’ll leave it with that clue.
@Ken S, @Bugsy, @ MH
Re: Crashing a B777 intentionally into the ocean (posting two days ago)
Although a B777 is not the same as an A330 there are some similarities. AF447 crashed into the Atlantic at high speed and produced more than 600 pieces of floating debris at the crash site and nothing that I am aware of on shore (Wikipedia & Google searches). 9M-MRO on the other hand produced no proven debris in the ocean but a accumulating pile of debris on various shore lines. Of course the impact site of 9M-MRO may have been missed but logically it infers some different mechanism of entry into the water rather than a difference between Airbus/Boeing and Indian/Atlantic Oceans. All a bit strange.
Some of the conspiracy theories are far fetched but the integrity of the BTO/BFO dataset post SDU reboot is questionable. If the data is honest 9M-MRO should be in the SIO on the 7th arc. So if it’s not there, even allowing for a small risk of a false negative, is it reasonable to deduce that the BTO/BFO dataset post SDU reboot is dishonest?
More to the point there is an obvious disconnect between the BTO/BFO and drift data which needs explaining. As Sir Tim Clark said early on in the mystery of 9M-MRO someone in authority knows what happened. Perhaps the soon the convened tripartite meeting would be a good place to start?
@Trond
If the relevant civilian Indonesian radar was switched off/being serviced/going through an upgrade process in the early hours of 8-9th March 2014 (is this possible?) then yes they are being honest in the sense that 9M-MRO was not seen however it could still have entered Indonesian airspace.
@StevanG
The problems any alternate search area definition has to address are the following:
1. A statistical (or other) basis for constraining the length of the arc to be searched: From the northern end of the Go Phoenix search to Christmas Island (for example) is 2800km along the arc. The original ATSB search area was 1000km long and was reduced to 600km when the second ATSB model, Data Error Optimisation, was dropped. Any alternate model has to indicate a short length of arc when the uncertainties implicit in the model and errors in the data are properly addressed. There is no point searching only 25% of the area that an alternate model suggests if that model can’t yield a practical length.
2. What width to search: Even if an alternate model indicated a length of arc 500km long (less than one fifth of the distance mentioned above) achieving the same width as the current search area requires a search area just over 60000sq.km. To search to the glide limit (in one direction only) would require 83000sq.km. Of course, a narrower width would give a smaller search area but that relies strongly on the unpiloted model (and one BFO data point) which is now strongly deprecated here.
3. Lack of flight model verification on a corpus of other flights: The Constrained Autopilot model was checked against a number of flights. I don’t see how more exotic flight based models can achieve this.
I have not yet seen any (believable) alternate model that could lead to a practical search even if the money and will were available.
@SteveBarret: “AF447 crashed into the Atlantic at high speed and …”
To be precise, AF 447 crashed in a nose-up attitude, on a flight path 45 degrees down, groundspeed 100 kts, vertical speed 100 kts, airspeed approx. 140 kts.
@Richard Cole
I totally agree with what you’ve just said iro search area requirements…
BTW, any update on the search progress, particularly iro Equator outside the arc, would be gratefully received (by me, at least)
Regards, Rob
@David, GE Rijn
The Tripartite Ministers Meeting was originally scheduled for 19th and 20th July, if my memory serves me rightly. Now we learn it’s 21st and 22nd July.
I know that only a week ago, it wasn’t clear who the new Aussie Transport Minister would be (due to the recent general election) which might be the reason why the meeting is delayed, alternatively and possibly more significantly, the delay – assuming there was a delay – might be to allow the ATSB to make an analysis of the outboard flap, ie how it got separated from the wing.
@Rob. The ATSB would have but three days in possession though they could have made a head start from photos. Still, that would be an ask.
But musing, supposing evidence emerged of end-of-flight, how significant would that be?
Issues:
-In the ATSB’s eyes which would be the less certain, the arc selected (ie route) or its width (end-of-flight)? If the former this evidence would have limited importance and vv.
-Is change of either at the expense of concluding the current search warranted?
@Gysbreght
You are correct. High speed was not the correct term to use. AF447 was not a controlled ditching just above stall speed. I am not a pilot or engineer.
Dr. Ulich states:
================
The air speed of 9M-MRO could have been controlled using one of several different methods. First, there are three methods that may be selected manually using the Mode Control panel (MCP): (1) constant True Air Speed (TAS), (2) constant Indicated Air Speed (IAS), or constant Mach number. Second, the Flight Management Computer (FMC) may be used to set variable speed profiles, including (1) Long Range Cruise (LRC), (2) Maximum Range Cruise (MRC), or (3) ECON (economy) mode utilizing the Cost Index (CI) parameter.
===========
Now, according to Dr. Ulich’s
“Figure 4 – Revised 7th Arc Locations for ECON Mode with Cost Index Values Indicated”
every Flight Management Computer (FMC) controlled cruising speed mode, from MRC to LRC to maximum-possible all-out speed, commands such high airspeeds, that all 7th arc crossings are west of 90E, and south of 37S.
IF so, and IF the a/c actually crashed E of 90E, hence 37S or farther N…
THEN the a/c may not have been flying on an FMC-controlled cruising speed profile.
IF the a/c attempted a landing, then maybe the auto-throttle engaged in either THR (constant thrust?) or SPD or HOLD ? Or, obvious alternatives are constant TAS / IAS / Mach ?
Dr. Ulich’s
“Figure 16 – LRC Mach Number Versus Weight”
shows that FMC-controlled speed profiles decrease Mach-number as the aircraft lightens from fuel consumption, especially at lower altitudes (FL330-350). However, I understand that the FMC commands FLCH to higher altitude in order to maintain M#. Nevertheless, higher altitudes are colder, with lower M1 speeds. So either way, perhaps one ought to expect to observe a decreasing airspeed over any ghost-flight, as the aircraft lightens and ascends.
I understand Dr. Ulich accounted for those effects. Thus, those who favor more northerly crash sites (including Inmarsat ??) from 36S and N-wards, may be implicitly presuming a non-FMC-controlled speed mode, of either constant TAS / IAS / M, and/or some AT setting e.g. HOLD / SPD / THR.
What happens to altitude, without the FMC ?
According to “B777 – Systems Summary: Automatic Flight”:
===========
When a conflict occurs between the VNAV profile and the MCP altitude, the airplane levels and the pitch flight mode annunciation becomes VNAV ALT. VNAV ALT maintains altitude. To continue the climb or descent, change the MCP altitude and push the altitude selector, or change the pitch mode.
============
If that is actually relevant, and if the a/c was not constantly descending during the southern flight, then it was maintaining a quasi constant altitude. If so, then it’s scientifically possible, that a landing was tried, speed & altitude reduced, and that the plane leveled off upon reaching the reduced altitude (20-25K feet ?). VNAV ALT may be a plausible “default” VNAV setting appropriate for an autonomous “ghost-flight” scenario (?).
If so, then does the a/c maintain “radio altitude” or “pressure altitude” or … ?? In meteorological practice, how does ambient temperature actually affect pressure, especially at high altitude ? On the ground, H-pressure areas are usually cold, dense air masses… but I understand that reverses at high altitude, above the cold dense airmass, where the air is thinner and exerts less pressure, than surrounding higher temperature airmasses.
If so, then as an aircraft flies south into colder air, at high altitude, it will descend, to maintain “constant pressure altitude”. Flying through denser air in turn requires lower airspeeds to produce the same lift, so again again one might expect gradually decreasing airspeeds, over the “ghost flight” phase (?).
@David
I have to be careful here, as I don’t want to bee seen as displaying bluster, but between you and me, I sure the ATSB are confident they’re on the right part of the arc. They are confident the DSTG Bayesian analysis is valid. The problem all along has been getting a consensus on the end of flight scenario.
There are two main camps: one says spiral dive after flameout (no pilot input), the other says piloted, extended glide (or perhaps, powered descent) after 00:19.
If the flap damage points to flaps down at time of impact, it will strengthen the ATSBs argument to get funding to extend the search downrange of the DSTG hotspot.
@Steve Barret
What do you see as an obvious diconnect between the BTO/BFO data and the drift data?
@David
If evidence emerged about the end-flight being a low speed impact/ditching event wouldn’t that be significant?
Or the opposite; if evidence emerged it must have been a high speed impact?
Assuming evidence emerges on a low speed impact/ditching I think this won’t compromise the 7th arc but only the widht of the search area and probably its position on the 7th arc.
They would be pressed to define a new search area if this would happen. Including the latest drift analysis. Or not if roven it must have been a high speed impact.
I think therefore it would be of crusial significance. And not in least also because this probably will mean proof the plane was piloted till the end.
@ROB
I can go a long way with you with your possible glide-scenario.
Only one thing I think you keep ignoring:
If the current hot spot was right and the plane glided even further south, debris should have been found in Australia.
According the latest latest drifter based studies, debris beneath 36S can be expected to land on Australia. North of 36S it won’t (as is what reality shows us).
According all other drift studies the crash area must be north or slightly north of the current search area.
I think this can not be ignored anymore.
As you seem to keep insisting on this I like to hear on what arguments you ignore the drift data.
@Ge Rijn
Obviously, something has to give here and for me, the thing that has to give is any drift study predicting landfall in Australia, because the evidence to date just does not give it any support.
This is how I’m seeing it: The Bayesian Analysis (which incidentally, I have full confidence in) suggests that the aircraft crossed the 7th arc in the current search zone. The debris recovered to date overwhelmingly suggests a controlled ditching, in my humble opinion. The debris is of a specific enough kind to effectively rule out any other impact scenario. Two of the flaperon seal/closing panels have reached the other side of the Indian Ocean, one ended up in Mozambique, the other on the shores of Madagascar, incidentally, they ended up not a million miles away from their flaperon. These panels that were probably next to each other on the wing!
And, if you believe as I do that the pilot’s intention was to deliberately loose the plane in a remote, uninhabited region, then the current search zone would have been the ideal spot.
So don’t expect me any time to fall on my sword. And don’t put any reliance on any drift study that says pieces should have ended up in Australia, because such a study is obviously bases on false assumptions.
@Richard Cole
Good points, IMO.
@ROB
As you I think also it was not a high speed impact and I also suspect a controlled ditching.
But none of this is proven yet. It could as well have been a kind of ‘AF447’ impact or something else. There’s just not enough evidence and facts yet to be sure IMO.
The facts we have though are the debris and its landing points, no debris in Australia (or Sumatra/Java), the Inmarsat data and the drift data.
Those data are not only based on assumptions but also on facts and scientific methods.
To put that aside as based on false assumptions is your fair right but I think then you also should be able to explain what’s false regarding those assumptions and facts.
MH370 was probably using its standard pressure-based altimeter, which measures uncalibrated Pressure Altitude, which relates to actual altitude approx. as:
Pressure Altitude = Altitude + (1013 – QNH) × 27
Altitude = Pressure Altitude + (QNH – 1013) x 27
where QNH is local sea level surface pressure (in hPa). So, if local surface pressure is less than the “standard atmosphere” sea level pressure (1013hPa), then actual altitude is less than Pressure Altitude, et vice versa.
Flying The Big Jets (4th Edition)
Stanley Stewart
===============
Radio altimeters are only used on final approach, for accurate height measurement above the runway threshold, and in fact are only activated below 2500 feet.
The pressure altimeter is the primary instrument for altitude indication, but since it measures air pressure, which varies throughout the day in one place, and also varies from area to area, further problems are encountered…
In the cruise, local pressure settings are not required, as above a certain height standard pressure setting of 1013.2 hectoPascals or 29.92 inches of mercury is set on all altimeters… The altitude at which the altimeter is changed from the local altimeter setting to the standard setting is known as the transition altitude (TA) and varies throughout the world… from anything between 2000 feet to 18,000 feet. Up to TA, altitudes are given in thousands of feet, and thereafter in Flight Levels, where the last two zeroes are omitted, e.g. 35,000 feet becomes Flight Level 350 (FL350). On descent, the level at which the altimeter is changed from the standard setting to the altimeter setting (QNH) is known as the Transition Level (TL) and varies according to TA.
@Richard Cole
I also think you name good points.
In this regard I think of several statistical forward drift studies done, starting in several 5 degree long boxes along the 7th arc from 36S till ~20S and compare those outcomes with where the actualy debris landed.
IMO a southern boundery of a possible crash latitude has allready been establisched on 36S.
I assume you will find a most probable starting box for the debris within 5 degrees latitude.
The widht of the box will then depend on wether the plane glided or dived down.
And I think only the found debris can answer that question.
@Steve Barrett posted “More to the point there is an obvious disconnect between the BTO/BFO and drift data which needs explaining.”
Yes Steve, I think that is the key question that needs an explanation right now. Why is there this disconnect between these data sets (drift data and the ISAT data)?
You would think that if MH370 crashed in the SIO there should be a convergence between these 2 data sets indicating a common search area somewhere along the 7th arc which satisfies both data sets but we are not seeing any such convergence here.
Clearly there is a problem here either with the drift data analysis or the ISAT data. Since I don’t believe that the analytics done on the BTO/BFO data is incorrect, nor do I believe that the analysis of the drift data is completely inaccurate, we must look at our assumptions and start to question more the intergrity of this ISAT data.
I strongly believe that the ISAT data (from 18:25 UTC onwards) is highly suspect IMO. I think as the search in SIO comes to an end, with no wreckage found, now is a good time for us to review these basic “likely assumptions” and start to look at some unlikely assumptions, like a possible spoof of the ISAT data or the possibility this data was completely corrupted or fabricated in some way.
Just continuing to do the math on this, believing that the ISAT data is correct, will only lead us to one conclusion only which is MH370 is somewhere along that 7th arc and nothing else is possible.
Like Albert Einstein once said, ” Insanity is doing the same thing over and over again expecting a different result.”
@Ken S
Like I asked Steve Barret. I don’t see an obvious disconnection between the ISAT data and the drift data. Can you tell me which obvious disconnection you see?
Obvious the drift data at this moment still leave a much broather range of possible crash areas along the 7th arc than the ISAT data although the latest drifter based forward models allready point to an area between ~36S and ~28S. And this is still in convergence till ~32S with possible flightpaths based now on the ISAT data and its assumptions.
Nothing sure yet but I don’t see where the drift data are conflicting or disconnected with the ISAT data.
Maybe you like to explain.
@Ge Rijn
The two specific drift studies I am referring to is the analysis done by Meteo France and Brock McEwen’s recent drift study. Both these drift studies concluded that MH370 crashed closer to the Equator with the Meteo France report specifically stating that the origin of the flaperon was ” close to the Equator near Indonesia”.
The findings in these drift studies clearly contradict the ISAT data which indicates that the plane went down in the SIO. This is the disconnect I am referring to.
@Ken S, the drift studies don’t contradict the Inmarsat data. Rather, their peak probability zones are in a different area than those of the DSTG analysis. However, lower probability areas do overlap the current search area, particularly at the northern end.
@Jeff
Yes Jeff , we do see, in particular in the GEOMAR study, this lower probabilty towards the northern end of the 7th arc (closer to Equator) but even in this study there seems to suggest, at the very least, that there are some basic assumprions used for calculating the search area that must be wrong because even this deift data analysis does not align with the current search zone
@all
After reading the last day or two of posts I am close to pouring gas on myself and lighting a match.
Rather, … there are some basic assumprions used in the drift data analysis that must be wrong when their conclusions do not align with the current search zone.
@DennisW
And I was hoping to share a beer or two with you and swap stories, once this is all over.
@Gysbreght
Well if your analogy is correct then we should be finding MH370 in the current search zone very soon.
@Ge Rijn
You said:”Those data (ISAT and drift) are not only based on assumptions but also on facts and scientific methods.
To put that aside as based on false assumptions is your fair right but I think then you also should be able to explain what’s false regarding those assumptions and facts”.
Donald Rumsfeld would be proud to have penned that :). But joking aside, and no offence intended, seems to me then there are different classes of facts and scientific methods. the ISAT data nould not have been spoofed, or misinterpreted, IMHO. Not just my opinion, but the opinion of many others, others even more qualified to express an opinion on the matter than myself (tongue in cheek, here of course)
Therefore suspicion must fall on the validity of the drift analyses. Forecasting drift patterns in the SIO is more akin to forecasting the weather over the next 12 months, so many variables and little understood processes at work that the task is practically impossible. Best left to the Shaman. I don’t meant to sound flippant, but that’s how I view it.
And BTW, no way can you compare MH370 to AF447. With AF447, there was an entire fin floating in the water. With MH370, we have a few very specific items, mostly RH wing trailing edge, detached in a manner strongly suggesting a ditching.
@Ken S:
Well, “current search zone” was a bit ‘tongue-in-cheek’, a convenient copy/paste from your comment.
Actually I never supported the current search zone. With mathematical gymnastics that goes over the head of most readers but does not fail to impress them it is entirely based on the ‘constrained autopilot dynamics’ and the ‘unresponsive pilot’ theory. Both hypotheses are not suported by any factual evidence.