The ATSB has just issued a lengthy and detailed new report explaining its latest thinking regarding the underwater search for MH370 in the southern Indian Ocean, available here. For the most part the media are reporting that its basic point is that the current search area is the right one. While that’s true, there are some more interesting points buried within in it, and within its companion volume from Australia’s Defence Science and Technology Group (DSTG) which explores the logic in further depth.
Here are my bullet points—I invite readers to add their own, or to correct or elaborate upon my points.
— One of the most jaw-dropping revelations in this report is that after 18:01:49 there was just a single radar return point. Note only does this contradict data shown to passenger family members soon after the disappearance (see Victor’s note below, and the image above), it also raises questions about the reliability of that piece of radar data. Since it was detected at the far limits of the radar equipment, it is relatively inaccurate, and as a stand-alone piece of data it is much more likely to be anomalous.
— The report reiterates that the only way to deliberately depower the SDU is by pulling circuit breakers in the E/E or isolating the left AC bus from the cockpit, but offers no explanation of why this might have happened prior to 18:25.
— It turns out that the time to recycle SDU is not 2.5 min but only 60 seconds. This is particularly important when it comes to laying out an end-of-flight scenario that presumes fuel exhaustion.
— The report says that after fuel exhaustion ditching not possible, with or without a conscious pilot. There has been a great deal of debate about the possibility of ditching in this forum, and I hope (but doubt) that the report will lay the issue to rest.
—At last, we know the cost index for the initial portion of the flight: it was set at 52. Of course there is no reason to assume that the later portion of the flight was conducted at this setting but it helps us calibrate likely flight modes.
— Overall point: With these two documents, the Australian authorities have shed a commendable quantity of light onto the subject of how they have determined the likely flight paths that MH370 took after it disappeared. It is heartening to note that they have greatly shrunk the length along the 7th arc along which the plane might plausibly lie: by my reckoning, from about 630 nm to 380 nm. And the “fried egg” of maximum probability is smaller still, only about 150 nm long. However, I find it baffling that, given the incredible level of effort poured into figuring out how the plane might have traveled prior to fuel exhaustion, there seems to have been basically zero time spent figuring out how the plane would likely have traveled after the fuel ran out. Frankly, I was expecting a lot of analysis along the lines of Brock McEwen’s work on this topic. As it is, it seems that instead of examining flight modes they took a guesstimate from accident-investigation experts and added a fudge factor. The result is that, while this latest analysis shrinks the search’s target area on one dimension, it makes it fatter on the other. In current southern search area, they’ve looked about 18nm inside, 30nm outside 7th arc. According to the new report, they should expand the search box to a width of 80 nm, symmetric around the 7th arc. This is not progress, and I think the ATSB can do much better (and hopefully will in a future report.)
Some additional points from Victor Iannello
Before I could post the above thoughts, Victor emailed me some observations of his own, which I include here unedited:
“There are some very strange results reported starting on page 17. Here are some comments related to that and the BFO bias:
1. As the attached graphic illustrates, if we are to believe that primary radar data exists every 10 seconds up to 18:02 and then only a single capture at 18:22, the slide presented to the NOK on Mar 21 at the LIDO hotel is false or includes data not used in the report.
2. There is a statement that the ground speed observed by the radar prior to 18:02 is relatively high and implies the aircraft would be at low altitude. While this would be allowed from Ma number and available thrust considerations, the indicated air speed would be extremely high, the airframe would be stressed, and the fuel efficiency would be incredibly wasteful. This is not consistent with the fuel calculations after 18:22.
3. The groundspeeds they calculate from the radar data have tremendous variability, even after the Kalman filter is applied. I estimate the peaks to be about 550 kn (!) We need the raw radar data to see what the hell they are doing.
4. The bias term was observed to be time-varying and modeled with a SD of 25 Hz. But there is also a statement that “Substantial effort was made to characterise this structured bias. It was found to have a geographic dependency but it has not been possible to determine a quantitative function to compensate for this change in bias.” This implies the drift might not be a simple OCXO drift issue. In fact, perhaps it is the correction term that has a geographic dependency rather than the oscillator drift.
Overall, I am not sure their work adds much value over the deterministic approach that the IG and others has followed. The PDFs and assumptions on heading/speed changes of previous flights are practically irrelevant.”
He later added:
“Their approach of randomly spaced turns, accelerations/decelerations, and climb/descents will always favor straighter, more constant speed paths that fit the BTO data. Since commercial flights are relatively straight to conserve fuel, it predicts those flights relatively well. If MH370 flew relatively straight, it should work there, too. But there are no guarantees the flight was near straight. For instance, if the flight flew south, a circle “loiter” above Sumatra would be ranked low, as would a curved path that followed the coast of Sumatra. There is bias in their model that is not acknowledged. Also, fuel calculations are only indirectly included by limiting the range of speeds. The model seems overly complicated for the value of what is produced. It seems developed more to impress than to enlighten.”
UPDATE: 12/4/15
Reader Paul Smithson asked “how much of the newly-defined priority area has already been searched?” In the image below I’ve outlined in black the area already searched (via Richard Cole) on the “fried egg” map. (Click to enlarge) The original 120,000 sq km search area is outlined in red; the new 120,000 sq km search area is outlined in purple. As you can see, almost all of the high-probability area has already been scanned. As more and more is searched, the probability density of the area being scanned will decrease, so that search becomes ever less fruitful. The effort expended between now and the end of the scheduled search will, by my seat-of-the-pants estimate, increase the probability distribution coverage from aroun 85 percent to 90 percent.
@Gysbreght: Yes, I read that article about Air Canada 143 before I posted. My interpretation is that the flaps could not be fully extended before landing, but were partially extended when the plane was flying at a higher speed (fast enough for the RAT to generate sufficient power but slow enough to allow some flap deployment).
The reason I said “perhaps the ATSB is correct” is because the MH370 is a different Boeing aircraft, so there are unknowns (to us). If it is true that aerodynamic control is reduced at low speeds when only the RAT is supplying hydraulic power, the chances of a successful ditching are greatly reduced.
Flap extension is simply not available with only RAT power, independent of airspeed. Also, regardless of the probability of a ditching being successful, the ATSB statement is incorrect.
Finally, landing and stopping within the confines of a runway is much more difficult than on the unlimited space of the ocean.
@Gysbreght: We all agree that a ditching does not require thrust. I am questioning whether sufficient aerodynamic control exists when only RAT power is available.
You assert that flap extension is not available with only RAT power, independent of speed. Do you have a reference that makes this statement for a B777? That would be very helpful.
@Gysbreght: I believe your statement that the RAT cannot lower the flaps on a B777 is correct. Looking at the cockpit hydraulic display as presented in the B777 FCOM, the RAT only powers “Flight Controls”, which excludes the flaps.
A ditching would have to performed at higher than normal landing speeds if the flaps are not available, which would make an already difficult maneuver even more difficult.
@VictorI:
I never implied that a landing without engines, on the runway or on water, was easy.
The following was collected before I read your last post:
FCOM 13.20.4: The RAT, when deployed, provides hydraulic power only to the primary flight
control components connected to the center hydraulic system. The RAT provides
hydraulic and electrical power throughout the flight envelope. (…)
FCOM 3.20.18:Flap and Slat Modes
Three modes of flap and slat operation are possible:
• primary (hydraulic)
• secondary (electric)
• alternate (electric).
The flaps and slats can operate independently in either the primary or secondary
mode. However, independent flap and slat operation in the alternate mode is not
possible.
Primary mode hydraulic power is supplied by the center hydraulic system.
Secondary and alternate mode electrical power is supplied by the left and right AC
busses.
The secondary mode is automatically engaged whenever the primary mode fails
to move the flaps or slats to the selected position. Once engaged, the secondary
mode remains engaged until the affected system surfaces are fully retracted or
center hydraulic system pressure is restored.
In the secondary mode, the flaps and slats are positioned by electric motors.
Because autoslats are unavailable, the slats are fully extended at all flap positions
(if airspeed is less than 239 knots) to improve stall handling characteristics. If
airspeed exceeds 239 knots, the slats retract to the midrange position (the
midrange index on the slat position indicator), or will not extend beyond the
midrange position.
(END of B777 FCOM quotes)
According to the Final Report of the Board of Enquiry into the Gimly incident:
“Without power, the aircraft had no flaps or slats with which to control the rate and speed of descent. (…) As they approached Gimli, Captain Pierson and First Officer Quintal discussed the possibility of executing a side-slip to lose height and speed in order to land close to the beginning of the runway. This the Captain did on the final approach and touched down within 800 feet of the threshold.”
That last problem is obviously absent in the middle of an ocean.
Just following this debate: Shah would have been well aware of the perils of running out of fuel if the plan was a smooth ditch? Why run it dry? One for the Shah noosemen.
@Gysbreght,
Two interesting points from the latest ATSB report:
1/ The failure to complete the expected IFE setup at 0021 could have been attributed to the “the IFE system being selected off from the cockpit overhead panel at some point after the 18:25 logon”.
2/ Following the APU autostart, the APU could have possibly “a maximum operating time of approximately 13 minutes and 45 seconds”.
Given that previously ultimate fuel exhaustion was thought to have been the point of partial logon; it now appears possible that the APU could have operated for sufficient time to provide during a complete descent. With APU, you have flaps.
OZ
@VictorI,
When the engines flame out they still rotate. A windmilling engine still rotates the accessory gearbox which has the hydraulic pump attached.
Although not functioning at peak performance they will act as a “RAT” for the left and right hydraulic systems.
The Gimli glider could not have performed what it did without them.
OZ
@matty-Perth : maybe it really didn’t run out of fuel?
@..ALL
QUESTION: What if the plane was intentionally flown till fuel exhaustion to prevent the aircraft leaving an oil slick on the surface of the ocean?
QUESTION: What about using GROUND EFFECT to fly very low to bleed off airspeed AND exhaust the fuel AND ditch safely? Is that something only test pilots are capable of doing?
My drift study comparison – finally complete:
https://drive.google.com/file/d/0B-r3yuaF2p72RnNtRVZuSVdHaG8/view?usp=sharing
Comments appreciated, as always.
I’m amazed that this report doesn’t use Bayesian methods to take into account that no trace of wreckage has been found within the search area so far. That is surely the most obvious application of Bayesian probability to this situation – since Bayes can take account of the information that the plane HAS NOT been found (whereas a strictly frequentist approach cannot). The “fried egg” likelihood distribution is rubbish, given that we know the plane just ain’t there. Given the evident work put into compiling this report (and the strong credentials of the people who wrote it) I’m amazed they didn’t finish the job…
The ATSB notes that the amount of fuel available to the APU after main engine flame-out depends on airplane attitude and acceleration, but does not seem to take these parameters into account properly.
Lets do a little thought experiment. Imagine yourself sitting in the cabin and able to communicate with the pilot. You have the tray-table pulled down and placed a glass on it, half filled with water or other fluid. You then ask the pilot to do the following manoeuvres, each time starting from wings level steady cruise flight, while you observe the fluid surface in the glass in front of you.
First, you ask the pilot to set up a coordinated turn, let’s say to 40 degrees of bank. The glass stays where it is, the fluid level in the glass doesn’t change.
Next, you ask the pilot (after returning to wings level) to pitch down, then up, and down again in a phugoid-type motion. Again, the glass stays where it is, and the fluid level doesn’t move.
Then, after returning to wings level, steady cruise flight, you ask the pilot to pull the thrust levers back to idle. This time you have to hold the glass to prevent it from sliding forward, and you see the fluid level pitching up in the glass by about 5 degrees. Then ask the pilot to pitch down to maintain constant airspeed, and you’ll see no further change in the fluid level in the glass, it remains at 5 degrees pitched up.
So what is the amount of fuel available to the APU with both engines flamed out and the airplane pitched 4 degrees nose-down?
@Matty – Perth
“Just following this debate: Shah would have been well aware of the perils of running out of fuel if the plan was a smooth ditch? Why run it dry? One for the Shah noosemen.”
anybody skilled enough to make the plane go dark would be well aware of that, idea that he went to SIO with intention to ditch the plane after fuel exhaustion is plainly stupid
@Gysbreght,
Have you been using speedbrakes to assist your descent? Have you deployed flaps and slats at any time during said descent?
My point is that up to now the thinking was that the APU flamed out at a particular event (incomplete logon). We now have anywhere from there to 12 minutes 45 seconds on (depending on inlet availability).
OZ
@OZ:
No, if I had I would have said so. If you use speed brakes you have to pitch down more to maintain airspeed. Same for flaps. Slats don’t change AoA and hence pitch for given airspeed. My point is that the ATSB’s estimate of the fuel available to the APU is probably wrong.
@Eoghanf, That’s a superb observation.
@Gysbreght,
Why am I trying to maintain airspeed if I want to ditch the aircraft?
I have no schedule to meet nor any real need to optimize my glide.
I can wash my speed off with pitch or combinations of pitch/speedbrake.
I can introduce slats/flaps on the way down, allowing a higher pitch angle.
The objective after flameout is not to maintain speed…it is to control the descent (high or low). There is now room for events which have not previously been considered.
You are probably right that the fuel available figures are out…I understand these are from Boeing….but may be conservative on their side.
OZ
@OZ:
“Why am I trying to maintain airspeed if I want to ditch the aircraft?”
It doesn’t matter whether you maintain airspeed or allow the airplane to accelerate or decelerate. The fluid level is a function of the perceived acceleration, which is the vector sum of the acceleration of gravity and the airplane’s own acceleration. That vector sum depends on thrust minus drag. When the engines flame out, the fuel in the tank moves forward, irrespective of whether you maintain pitch and altitude, or pitch down to maintain airspeed. Difficult to grasp?
@OZ
“1/ The failure to complete the expected IFE setup at 0021 could have been attributed to the “the IFE system being selected off from the cockpit overhead panel at some point after the 18:25 logon”.”
Meaning that at least around 18:25 IFE was active (and very possibly it was active all the time until after that time)!
And thus airshow was available to the passengers until after 18:25!
Is there any information indicating otherwise?
Gysbreght,
Re: “The fluid level is a function of the perceived acceleration…”
No. You are forgetting this is a dynamic case, not static. Moreover, in case of the APU-fuel problem, the situation is a way more complex: you need to consider actual piping design, presence of valves, etc.
The ATSB talks about the fuel available to the APU fuel inlet. That’s what I’m responding to, the fuel in the wing tank. The fuel in thew plumbing after the inlet is not sufficient for 13 minutes 45 seconds running time.
If the plane was ditched:
1. If the plane was still structurally sound, how long would it take before it submerged completely?
2. If sound, wouldn’t the passenger and crew have instituted emergency procedures and deployed the doors, vests, and chutes? Meaning these items would have been detected floating somewhere, right?
I just have a very difficult time with only one piece of evidence (the flaperon) being found. The lack of more is deafening. That’s why the ditching may be a better theory. But then if it was ditched, why weren’t doors opened, chutes deployed, and vests donned?
@Adam. Exactly. Whether there was a crash or a ditching, and no matter where the plane landed along the 7th arc south of the equator, it is hard to imagine why there was not more floating debris that was recovered by now.
@adam –
My problem is a whole aircraft was not detected while ditched and floating about. With the fast satellite resources available it really should have been seen. If it crashed into the ocean then all sorts of debris should have been detected.
@adam
“But then if it was ditched, why weren’t doors opened, chutes deployed, and vests donned?”
Because its cold wet and hostile on the outside in the SIO. I have read somewhere that the B777 is designed to float indefinately if intact. It would be much safer to stay inside with doors shut than to venture outside.
@Brock and all,
Well done to Brock on the drit analyses’ analysis.
My take away from his analysis is that, if both the drift studies and INMARSAT’s indications are genuine, the flaperon had to have come off much earlier during the flight.
Question to aviation experts, as also tweeted by Brock, what impact on flight capability would a missing flaperon have? Is it possible for a B777 sans flaperon to fly on for hours? Could a missing flaperon force the abandonment of a landing attempt at the IO end of the Malacca Straits (as per Dr Ulich’s latest)?
Regarding the new ATSB Report upon first glancing, it seems again much ado about the end of flight scenario, SDU, engine flameout, fuel exhaustion, Rat-tat-tat, etc. I don’t get the degree of importance there, to me it seems much more interesting and important the time from 17:21 to 18:25 reboot, was SDU on the entire time, was automatic switching (buses and the IDG’s) done, was a breaker pulled in the EEbay, they don’t expound on that early part. What about at 17:21 and 18:25, was anything engine related and if so would Rat-tat-tui have deployed making Dr, Bobby’s contrails in and out of the Straits? Was IFE disabled from the cockpit circa 17:21 but SDU remained in an “on” mode? Was there a cascading series of malfunctions to the Straits? And to the point of regardless if it was a controlled ditching or a crash in the SIO, that no life jackets or bodies were found does that signify that no one was coherent to get out of the aircraft? Still too many questions.
“A controlled ditching scenario requires engine thrust to be available to properly control the direction and vertical speed at touchdown and to provide hydraulic power for the flight controls including the flaps.
The final SATCOM transmission was considered by the satellite working group to be due to a power interruption to the SDU..[because] engine flame-outs triggered the APU auto-start that restored power to the SDU. This evidence is therefore inconsistent with a controlled ditching scenario.”
But what if the plane had been flying very low?
This could be the reason why after the left engine flame out and the 00:19 log-on there was no IFE connection due to … “the IFE and/or SDU becoming inoperative (due to impact with the water) before the connections could be set up.”
So if the plane was flying at a very low altitude with thrust, then soon after the left-engine flame out, the plane would descend to the water very quickly (less than 3 minutes).
Is this a plausible scenario?
@CliffG:
If the airplane was flying low when the second engine flamed out it would have entered the ocean close to the 7th arc, but it hasn’t been found there.
@Cheryl:
The end-of-flight scenario defines the width of the search area. Earlier that was arbitrarily set at about +/- 20 NM, now they propose no less arbitrarily +/- 50 NM, whereas with human inputs the airplane could have flown 100 NM past the 7th arc.
1. If the cause was an accident or a deliberate ditching, why the stonewalling and mis (and contradictory) information?
2. If Shah wanted to make a political statement, he failed.
patience, dear pax, patience….when they find this damn thing, what will be revealed on the last 20 minutes, or so, of the CVR will clear things up immensely (sic), especially the symbolic nature of the intended ditching “target zone”….they are getting closer every day …closer and closer….about another 300 nm more to the west….so, in response to Shah’s political statement….it’s just to early…..but well worth the wait….I think we all owe posterity that much.
@Gysbreght
“If the airplane was flying low when the second engine flamed out it would have entered the ocean close to the 7th arc, but it hasn’t been found there.”
If it was flying low then it should be some 500-1500 miles up from the current search area.
But ATSB seems to be reluctant to even discuss about searching there…
@MuOne: airlandseaman wrote a 5-page piece on July 31, 2015, in which he argued thus:
1) separation during flight WAS indicated by state of flaperon (leading edge pristine, trailing edge in shreds), BUT
2) this in turn suggested trailing edge damage was due to FLUTTER, which in turn suggested high speed, which suggested impact soon thereafter.
From the paper:
“it indicates an in-flight breakup, most likely due to very high speeds, flutter and perhaps loss of hydraulic/electrical power to the Flaperon actuator post fuel exhaustion. This scenario is consistent with the steep, spiral descent observed in the B777-200 simulator.”
https://www.dropbox.com/s/jfninslr7z5kuay/Implications%20from%20the%20Reunion%20Debris%20found%20July%2029.pdf?dl=0
While this seems to me to rule out flaperon loss hours before impact, I invite aviation experts to weigh in.
(I expect some of them will be reluctant to confirm this for you, MuOne; ambiguity has for some time, now, been the weapon of choice for those keen to keep us watching and waiting, rather than what we all SHOULD be doing: taking concerted ACTION to finally hold search leaders accountable.)
@Brock,
I have read Mike’s paper and it struck me as odd to call the trailing edge shredded, or having a rugged edge. In the Reunion photos, it is clearly visible that the underside has a long clean linear lateral break.
When I asked Mike on twitter how that linear break feature could be explaied he responded with a single word: flutter.
I am not yet convinced.
@Brock:
I wouldn’t call myself an “aviation expert” because I’m aware of the limits of my “expertise” and of all the aspects of “aviation” that I know almost nothing about.
I’ve stated my opinion about the IG’s high-speed spiral dive theory in general, and the flutter theory in particular, countless times and don’t see a point in repeating that.
For those that haven’t seen it, there is a new blog post by @DennisW in which he theorizes that the French investigators have shared with the DSTG some evidence that the flaperon experienced damage from aerodynamic flutter. For this reason, the DSTG report makes strong claims against the possibility of a controlled ditching.
Read the full posting at: http://tmex1.blogspot.com/
Gysbreght,
Thank you that I know. I was getting at the sole performance of SDU/AES at fuel exhaustion losing it’s power, “engine” related at end of flight which stands to reason. The SDU/AES unit, in and of itself is not determining search area (the communication data from it, reverse engineered, yes). What I was getting at is they are not saying much about the quirky performance of the SDU/AES for the hour prior to and leading up to 18:25. As far as just the SDU/AES is concerned, that time to me seems more intriguing than the normal course it would take losing it’s power supply at the end. I guess basically what I am saying is that has all been gone over regarding the SDU at the end, but it is still shrouded in vagueness at 18:25.
Are you saying then that the 00:19 log-on of the SDU/AES determines point of impact into water (if no spoofing involved)?
With reference to oPreliminary MH370 Flaperon Failure Analysis by Tom Kenyon
2015 October 15 on Duncan Steel’s blog
He noticed a similarity of Flaperon damage between the Reunion Island and Asiana’s hard landing at SFO.
It would seem to me that perhaps MH370 came to a similar hard landing as Asiana …
@Eoghanf As far as I know, we have no experience or data to come up with a Bayesian prior as to the significance or not of not having found the underwater debris. The best analog, AF447, was a far easier search but there the successful Bayesian method ignored the prior search results in deciding where to look.
No, I didn’t say that. The 00:19 log-on together with the times taken by the APU and the SDU to get ‘on-line’ defines when the second engine flamed out and the autopilot disconnected. That alone doesn’t determine the time and location of impact.
Dennis – The miracle on the Hudson involved a plane that had just taken off – would it necessarily be going slower than a 777 that had to get down from over 30,000 feet without power??? I for one wouldn’t know.
One thing I have noticed is that the DSTG/ATSB have always been pretty sensitive to what was being said around the traps. Ditching has gotten some traction of late and I sense they might defending their line here, and trying to keep everyone on the right page without the narrative getting away from them? They are BFO purists at the beginning and end of the day.
If the French have data that the DSTG are not allowed to divulge then there is not much point in passing it on when it does not impact the conduct of the search?
Regarding the Bayesian analysis for AF447, the search zone it derived most defnitely did incorporate the previous negative search results:
arxiv.org/pdf/1405.4720
Bayesian analysis is not magic – there is still a lot of guesswork and fuzzy approximation involved (e.g., what is the probability that the current MH370 search would have seen wreckage if it were actually there?)
In the “Bayesian Methods” report Figs.10.5 through 10.7 are quite interesting. Noteworthy is the almost constant heading in Fig.10.5, the curious jump from M.79 to M.81 in Fig.10.6, and in Fig.10.7 that all values of BFO estimated by the ‘particle filter’ at 23:15 are outside the 1-sigma lines for the assumed measurement noise.
I’ve plotted the mean values of BFO residual error in Fig.10.7 against time:
https://www.dropbox.com/s/0eb1srfeplvgx87/BFOresidu.jpg?dl=0
Noteworthy here is the distinct trend in the mean BFO error from +3 Hz to -8 Hz.
But according to the authors of the report “The BFO residuals are statistically consistent with the empirical error model.”.
FYI: attached is a link to a jpeg file illustrating where the Fugro ships are actually searching as we speak. In the absence of further updates by Dr. Cole, I’ve taken Mr. Chillit’s latest image, found its coordinates by superimposing a proper bathy map (and aligning topography), and finally superimposing my most recent copy of Dr. Cole’s search map (and aligning coordinates).
As you can see, Fugro Equator is searching out to a point quite neatly “pointed to” by the tiny finger extending westward from the SW corner of the black “searched” line in Jeff’s map, above. Since it is well beyond this finger, it is also well outside the box (red rectangle, above) the ATSB has just – JUST – redefined in its Dec. 2, 2015 publications.
https://drive.google.com/file/d/0B-r3yuaF2p72a3oxM1J0YVRBUFk/view?usp=sharing
Posterity will be very interested in these facts; it saddens me that real-time discontent is so slow to the boil. A chilling sign of the times, I suppose.
@Brock: Perhaps the “finger” represents a raised middle finger directed at us?
On a more serious note, I think the search team is trying to systematically scan the priority zone while occasionally diverting to check out “hunches” such as those end points suggested by Simon Hardy or Bobby Ulich.
@Victor: thanks for the chuckle, and the observation.
But regardless of their motivation, the ATSB should be able to show us both…
a) fuel analysis, and
b) debris drift analysis
…demonstrating those spots are at least FEASIBLE. They have done neither. The expert work they themselves endorse in fact rule these search locations OUT.
@Brock: It is not hard to show that there are paths allowed by the speed and turn time constraints delineated in the DTSG report that are not part of the current search zone. For instance, if the plane turned south at 18:28 (just after the satellite data) and traveled at M0.84 at FL340 while exactly matching the BTO, I calculate a crossing of the 7th arc at -39.8,84.5. This is clearly outside of the search area. This path is “nearly but not exactly” straight in that the southern track varies between 191.3 and 194.1 degrees.