If you were leading a high-profile international aircraft investigation, in command of the world’s most qualified technical experts and in possession of all the relevant data, would you bother listening to a rag-tag band of internet commenters, few of whom actually work in the space or aviation industry, and none of whom have access to all the data?
Most likely, you’d say: certainly not! But as time goes by, and the puzzle remains curiously impenetrable, you might find it worthwhile to pay a listen to what the amateurs were saying. You might even abandon some of your own conclusions and adopt theirs instead.
This appears to be the case in the search for Malaysia Airlines Flight 370, which disappeared en route from Kuala Lumpur to Beijing back in March. From the beginning, the authorities running the investigation — first, Malaysia’s Ministry of Transport, and later the Australian Transportation Safety Board (ATSB) — held their cards close to the chest, releasing very little information about the missing plane and maintaining a posture of absolute conviction. The investigators’ self-confidence reached its apex in April, when their methodology led them to an area of ocean where underwater accoustic signals seemed to be coming from pingers attached to the plane’s black boxes. Officials assured the press that the plane would be found in “days, if not hours.” But then it wasn’t. A scan of the seabed found nothing; the pingers were a red herring (perhaps literally!). Back to square one.
Meanwhile, on the internet, a group of amateur enthusiasts had come together from all around the world to trade ideas and information about the missing flight. The group, which came to call itself the Independent Group (IG), emerged from various online comment threads and eventually grew to about a dozen individuals. This was a truly spontaneous, self-assembling crowd: there was no vetting of credentials, no heirarchy of any kind. (Full disclosure: I count myself among this group.) Basically, if you seemed to know what you were talking about and could comport yourself in a collegial fashion, you were accepted into the crowd.
While the mainstream press was reporting the ATSB’s pronouncements as received wisdom, the IG was raising red flags. IG members were among the most vocal critics of the ATSB’s contention that the accoustic pings probably came from black-box pingers. And later, after a public outcry led Inmarsat to release a trove of data received from the aircraft, and the ATSB issued a report explaining how it had come to identify its current search ear, the IG dove into the new information with abandon, quickly identifying holes in the data and weaknesses in the official approach. In a pair of papers, the group recommended its own search area, hundreds of miles to the southwest of the ATSB’s officially designated zone.
Today, the ATSB has released an update to its earlier report, explaining why it has decided to reassess its conclusions and move its search zone to a new area — one that overlaps, as it turns out, with the IG’s recommended area. (In the graphic above, the white bracket shows the ATSB area; I’ve added a yellow dot to show the IG area.) Needless to say, this has caused elation within the ranks of the IG, who see the move as vindication of their methods, and indeed validation of their combined efforts over the last few months.
A few observations on the new report:
— One of the reasons the ATSB gives for the shifting of the search area is the recognition that Inmarsat data related to an unsuccessful ground-to-air telephone call attempted at 18:40 indicated that the plane had already turned south at that time. The IG had been basing its analyses on this data point for months.
— Since the June report, the ATSB has improved its BFO model by taking into account various factors — such as temperature shifts caused by the Inmarsat satellite passing through the Earth’s shadow and the mis-location of the Perth ground station in an important Inmarsat algorithm — that IG member Mike Exner has been working through in detail for months.
— The ATSB has fundamentally changed its approach in how it is assessing the plane’s likely path. In its June report, the focus was on what I call the “agnostic” approach: it generated a large number of flight paths based on as few initial assumptions as possible, then graded them based on how well they fit the timing and frequency data received by Inmarsat. This resulted in a population of potential flight paths that fit the data well, but did not make any sense in terms of how a plane might be flown. Some of the routes, for instance, involved multiple changes in heading and airspeed. Today’s report explicitly excludes such flight paths. The ATSB and the IG alike now assume that the last several hours of the flight were conducted without any human input — the crew were presumed to be incapacitated by hypoxia or other causes, so the plane flew on autopilot until it ran out of fuel and crashed. This has been the IG’s starting point for ages, and the fact that the ATSB has now adopted it is a major reason for why the two group’s search areas have now converged.
— You can see in the graphic above how an emphasis on matching the Inmarsat data will tend to lead you in one area (“Data error optimisation”) while an emphasis on routes that comport with real-world autopilot functioning will lead you to another (“Constrained autopilot dynamics”). To be sure, they overlap, but the peak area of one is far from the peak area of another. I think it’s important to realize this, because it helps us to understand why it has been so hard to get a handle on where MH370 went, why the official search area keeps moving, and why knowledgeable people have been furiously debating possible flight paths for months: the BFO and BTO data just do not match up that well. In order to arrive at its recommended area, the IG has been willing to accept much wider deviations from Inmarsat data points than the ATSB has been comfortable with.
— Finally, it’s worth nothing that the ATSB approach is superior to the IG’s in one important regard: it is at heart statistical, looking at families of potential routes rather than proposing and assessing one at a time. There is a tendency, as an individual–and I have fallen into this myself–to cook up a solution, run an analysis, and to be so impressed with the result that one wants to shout about it from the rooftops. (Ask me about RUNUT some time.) The IG has come up with a search area essentially by pooling together a bunch of individual solutions, each of which is generated by a different set of procedures and different set of assumptions. It’s a herd of cats. To really move the ball forward a more rigorous approach is needed, one that takes each procedure and sees how it would play out if the assumptions are methodically modified.
The upshot is that, since the early days of the investigation, the attitude of search officials has changed radically. Once dismissive of amateurs’ efforts to understand the incident, they have clearly begun to listen to the IG and to turn to it for insight and ideas. Indeed, you could say that since the release of Inmarsat data and the issuance of the ATSB report in June, the search for MH370 has become effectively crowdsourced: a de facto collaboration between the professionals and a spontaneous assemblage of knowledgeable experts.
UPDATE:
The overlap between the ATSB’s analysis and the IG’s is more evident in the image below, courtesy of Don Thompson. It shows the fan of values calculated by ATSB to match likely autopilot settings.
Re. Sharp corner in radar track.
I’d like to mallow an earlier statement of mine: “The gist of it is, if there is a discontinuity (physically impossible sharp turn) in the early radar track, there is no way that the later track is that of MH370”.
I had an inspiration in the shower this morning and came up with a scenario, which would create a sharp corner in the radar track:
Summary:
– Some incident shortly before the sharp corner in radar track
– Subsequent loss of control followed by an accelerating dive
– Entering near vertical dive with roll
– Recovery of control, arresting roll and leveling off in direction of out-going tangent of sharp corner.
Theoretically, a similar scenario would work as well. Here the dive is replaced by a vertical climb and spiral, followed by a leveling off. (Not sure whether the acrobatic abilities of the 777, would allow such a maneuver though).
A visualisation can be found here:
https://www.dropbox.com/s/5clik9n10qpwffc/AlternateExplanationSharpCornerRadarTrack.pdf?dl=0
One major implication of this dive (and/or climb) scenario is, that the post event altitude would be quite different to the prior flight altitude.
Cheers,
Will
MuOne: Thank Jehovah that someone besides me has epiphanies in the shower. It’s an interesting phenomena, isn’t it?
Luigi:
Wow, you are beginning to write like a true tweaker there, good buddy! Re your analysis of the 18:28 frequency shift, can you exhaust all possibilities beyond that of a high rate of climb (i.e., beyond the motion of the aircraft)?
I do get what you are alluding to: a descent to an FL <350 would provide for an approach to Penang or KL, while we do have the report of the FO Fariq's cell phone ping by the Penang tower. This would in turn further indicate Malaysia in terms of the destination/motive, with the climb back to FL350 initiating c. 18:25 in turn indicative of the end-phase of the period representative of a loss of post-diversion equilibrium.
Please share: can you reconcile a descent from beginning at KB and progressing to Penang and a climb back to FL350 (e.g., equilibrium) achieved no later than 18:28 with the IG's high probability point in terms of fuel consumption, times to the ping arcs as constrained by the data, etc.? Now that you are officially in the tweaker camp, you may as well give it a shot. 😉
MuOne: that’s phenomenon, of course.
@Rand,
Realizing that you had your epiphany in the shower, was an awkward moment! Fixed it by turning the shower to cold. LOL.
Re dive or climb as explanation for sharp corner, there are two different implications for the turning off of SDU:
1. Dive: Emergency, SDU turn off co-incidental caused by failure
2. Climb: Deliberate, SDU turn off purposefully hiding ADS-B data, BFO. Albeit the latter might be co-incidental as far as planning is concerned.
Cheers
Will
BTW, Luigi, and just for fun: I put the probability that your mother is Italian and your father American at .60 and that your parents met post-WWII (1945 – 1955) at .25 probability. I would put the probability that you live on or are originally from the East Coast at .60. These values are representative of the highest values that I have assigned to the problem in the course of developing this speculative guess. It could, quite obviously, be way off (e.g., you could be from Calgary and an ancestor bore the name Luigi), but nonetheless it is representative of my best stretch guess.
Focus!
Luigi – climbing after he has left radar cover might indicate he was a bit lower than normal to escape it a bit sooner in the first place? If he left the SDU on deliberately did he want them to know where to look, because even a twit like me would be wary of leaving a trail via satellite if I was in stealth mode. Or maybe in the throes of a meltdown and it didn’t really matter by then?
One thing – I’d be a lot more comfortable with the data if they didn’t have these little anomalies sitting around. To really understand the data you need to understand all of it – ideally.
MuOne: I assume that you are referring to the turn at IGARI once again. Remind me: why are you noodling with the dynamics of a climb or a dive at the turn? Is either required for a fit somewhere?
And that is precisely why we shower in separate showers, so don’t fret about it.
@Luigi,
Re: Your post Oct. 19th 5:46 p.m.:
Your reference for the 800 kph speed is the Inmarsat paper; it is not from the ATSB. The period of time covered starts at 18:25; it does not cover the radar track. The speed is an assumed speed; it is not measured. Your comparison of this speed to the speed I calculated for the radar track is apples to oranges.
Re: Your Post Oct. 19th 11:32 p.m.:
About a month ago I published 6 pages of analysis of the BFO data between 18:25 and 18:40 in my original white paper. It describes the maneuvers, such as turns and climbs, needed to match that data, assuming it is valid. Figure 5-9 on page 30 is particularly enlightening.
I’m wondering if such a climb, rather than being a mid-air event, could be an aborted landing followed by a takeoff?
That would require an airport on the ring of this data point, but would be a plausible explanation for a steep climb.
@Rand
I’m afraid you didn’t do too well on your probability assessments there, buddy.
I’ll leave it to others to noodle the problem of the 18:25-18:28 BFO data for a bit. I merely note that, if the data has a physical interpretation, it seems most likely to represent a brief, rapid climb, fighter-pilot-style. It therefore could be a fourth line of of evidence supporting major altitude changes during the return to Malaysia. The other three are: (1) reporting apparently sourced to Malaysian military officials right after the disappearance, as manifested in the Mar 14 NYT map (for example); (2) eyewitness accounts from Kota Bharu; (3) the cell tower reconnect in Penang.
As far as the impact on the high-probability search area is concerned, as I said above, I’m guessing that accepting the changes in altitude would imply a faster fuel burn during the return to Malaysia, leaving less fuel for the final leg. I will leave the calculations on how altering those parameters would affect the SIO end-point to the enthusiasts.
@Matty
To me, the most obvious explanation for the satcom reboot is to give Hishammuddin one last chance to beg for a safe return of the aircraft. My guess is this incident was about humiliating Hishammuddin, and HH did not want to be humiliated. Thus, an irresistable force met with an immoveable object, with the usual tragic consequences. It’s about duelling egos — it’s a cockfight and a pissing contest. I really doubt the satellite ping trail was on Zaharie’s mind.
And, yes, there are quite a few anomalies in the satellite data (that’s the real world), although nothing that to me would call into question the general conclusion about a turn to the south with an SIO end-point.
@Dr. Ulich
I stand corrected: the Journal of Navigation article was written by the Immarsat folks, not the ATSB.
Yes, the Immarsat modeled speed values are from just after the radar contact ended, fair point. I don’t doubt that this plane was travelling at a high rate of speed during the “dark” phase of the Malaysia return/retreat. I do doubt that you can infer a fixed speed for the entirety of this period or a level altitude based on the miniscule amount of radar data that has been revealed by the Malaysian authorities. Simplifying assumptions have been reified here, at the cost of ignoring the actual evidence. And, I do doubt that the high speed has anything to say about the reported descent coming into Malaysia. I’d like to see the doghouse plot for the 777, please. Until I see otherwise, my guess is that a pilot gunning the plane could fly at high mach while coming in low with no difficulty, and I suspect that’s exactly what happened. As we have covered above, so far as Boieng’s fly-by-wire system is concerned, “do what thou wilt shall be the whole of the law.”
Could you post a link to your analysis encompassing the 18:25-18:28 BFO data? I’d be interested to see it.
Luigi: well, that’s what can happen when you stick your neck out with intransigence: sometimes your head gets chopped off.
You can read Dr. Ulich’s paper at the link below – and get a John Florentino update (Musical Chairs…) to boot.
http://www.mh370hunt.com/location-mh370/
@Rand:
Thanks for the peep re that website.
@Luigi: here are the 4 “sources” you use to justify this alleged altitude drop during the westbound leg:
#1. Altitude indications of primary radar during westbound track: roundly discredited by radar experts (unless frequently recalibrated, altitude readings quickly deteriorate into random number generators; these radar installations were NOT frequently recalibrated)
#2. The altitudinal estimates of two fishermen (on what basis do you set their credibility any higher than that of, say, Mike McKay?)
#3. The “leaked” cell phone story (from anonymous US sources, at a time when both “the pilot(s) did it” AND “used more fuel, therefore search further north” were narratives the JIT was pushing (science has since proven the latter false, and will get to the former in due course.)
4) BFO values from 18:25-18:28 (which have been analyzed TO DEATH by the NTSB, the ATSB, the IG, Dr. Ulich, and others – with ALL of them rejecting the notion that they indicate an altitude shift)
I think, Luigi, that science is suggesting strongly to you that it is time to abandon any theory which a) trusts as accurate the radar- and Inmarsat-indicated path of MH370, yet b) includes wild swings in altitude during its westward leg. It is, quite simply: “if a), then not b)”.
I stress the “if a)” part…
@Luigi,
As requested, here is the link to my white paper “The Location of MH370”:
https://drive.google.com/file/d/0BzOIIFNlx2aUVy0tLXZFUjVic0E/edit?usp=sharing
On the subject of eyewitnesses, Katherine Tee has a new post on Twitter:
“I agree that what happened to MH370 is being covered up”
http://t.co/0hKHwvcfPp
Speaking of what science strongly suggests:
Dear IG members: here’s the statement which, if publicly endorsed by your group, would REALLY help me in my quest for truth:
“Based on performance limits set out by the ATSB in Figure 3 of its June 26 report, and refined in Figure 3 of its October 8 update, we consider hypothetical flight paths which have MH370 turning south at or before 18:40 UTC – yet crashing at s21 latitude on the 7th Inmarsat arc – to be infeasible. The reason is that paths terminating this far north require average speeds so inefficiently slow that MH370 would run out of fuel well before 00:19 UTC – the time of fuel exhaustion strongly indicated by the Inmarsat signal data.”
I am asking you merely to state in words what those charts already scream out in technicolour to the educated reader. In this regard, I hope – and think – that this is not too much to ask.
Feel free to suggest edits, if these would help you get more comfortable with the statement.
If you are busy developing your own performance model to pressure-test the ATSB’s, then please so indicate, so I can express my apologies for the distraction, and appreciation for your efforts.
If any other qualified individual wishes to endorse this statement (and/or suggest edits), I’d be likewise very grateful.
Brock,
I’m not sure I get your point. In the 26 june report the northern performance limit on the 7th arc was at 18 degrees south. In the 8 october update is has moved to 27 degrees south. It seems the ATSB agrees that S21 latitude is infeasible when the turn south is assumed to occur before 1840 UTC?
Hi @Rand
“MuOne: I assume that you are referring to the turn at IGARI once again. Remind me: why are you noodling with the dynamics of a climb or a dive at the turn? Is either required for a fit somewhere?”
Yes, I am noodling with the turn at IGARI. The fit I am chasing is the sharp corner in the radar track. For MH370 to have been, where the ATSB report says it was at 18:22 requires that the complete track, from KLIA to 18:22 is plausible.
The corner near IGARI was shown by Ron Black to be too sharp to be a level flight turn (and inspired his two planes theory).
In my view, finding a plausible explanation for that sharp corner is a necessary condition for the later radar track to be that of MH370. This in turn is a necessary condition for the path models using that position as initial condition to produce good end point predictions.
If my suggested climb or dive scenario can be rejected for technical reasons, there is nothing left that would validate the 18:22 radar return to be that of MH370 and the last known position would move back to the sharp corner that Ron identified.
PS.: For further reading on the impossibility of the sharp turn etc, Ron’s Blog can be found here:
https://plus.google.com/app/basic/stream/z133cdxrbvj0jbs5y04cebpx4zq5gxs4a3k#_MB0
Cheers,
Will
@Dr. Ulrich
Thank you for posting the link to your monograph, which appears quite interesting. I’ve so far only had time to give the analysis of the 18:25-18:26 BFO data a once-over (plus give a quick skim to the rest), so these are preliminary comments.
Like you, I’m inclined to suspect that the unexplained BFO spike in the data is due to motion of the plane (the Immarsat folks prefer to leave this as an open question). My “analysis” above was based on eyeballing tables 1 and 9 of the Immarsat paper and doing some back-of-the-envelope arithmetic. I’m glad to see that the conclusions aren’t that far from your own. As I understand it, you posit that the spike is the result of a brief, high-speed “impulse” climb (as I did above), but also incorporates the effects of a major turn whose start and end headings happen to bracket the line-of-sight to the satellite, leading to a cancelling out of the turn’s contribution to the BFO. You state:
“The green solid line in Figure 5-9 is the predicted BFO assuming an increase in altitude
took place beginning at 18:25:30 UTC, followed by a 97 degree left turn beginning at
18:27:00 UTC and ending at 18:28:36 UTC. The turn times are from the Maimun Saleh Airport route fit. The Rate of Climb needed to match all the data points is an initial (and very brief) ~6,000 feet per minute at 18:25:34 followed by a ~2 minute period
of relatively constant ~2,000 feet per minute Rate of Climb. The altitude increase due to this climb scenario is roughly 4,000-5,000 feet.”
I don’t have any major problem with this analysis. I will remark that a climb alone is a simpler scenario, and I do find the near identity of the bracketing BFO values in the sequence a bit of a coincidence for any scenario involving a heading change.
It does seem remarkable that we have been left hanging by Immarsat on the question of whether these BFO values can simply be explained away by electronic gremlins — if they can’t, these data points can tell us a lot about a critical transition in the flight.
@Gysbreght – thanks for the chance to clarify.
With your last sentence, I couldn’t agree more. It should be trivially straightforward for a member of the IG to publicly agree that s21 is infeasible under a swift turn south (as you say, it is a mere expression of AGREEMENT with the ATSB’s Oct.8 update).
Yet it has proven difficult. I’ve been trying since April to get anyone (including the IG) to join me in public acknowledgement of this thoroughly uncontroversial truth. So far, no luck.
In fact, the IG seems to be going in the OPPOSITE direction – just last month, they published their “decompression scenario” – a scenario which turns south swiftly, and ends at s21. I disputed its feasibility within an hour of it being published – and a subsequent report did (to be fair) reduce it to an unannotated set of faded pixels – yet no FORMAL retraction has (to my knowledge) ever been issued.
In fact, Mike Exner (who has claimed a leadership role within the IG on this scenario) stated to me just last week that he deemed s21 MORE likely than s30. He suggested that endurance at 323KGS is “similar” to that at cruising speed – a view emphatically contradicted by the ATSB’s Oct.8 update. He has not responded to my requests for clarification of this curious stance.
I’m holding out hope that the IG is performing primary research, and would rather speak only to the results of their own modeling.
For clarity: the s18 intersection you quote is as far north as it is because – and ONLY because – of the murky “passed near a NW point” comment inserted by the ATSB into their June 26 report. That will be my NEXT topic…but first things first.
@Brock,
The endurance of the 777 increases as the altitude falls from FL 35000. This can be seen in the data provided by NewAmericanCenturySucks (whose writing style is quite similar to yours). You can find this data by searching on that name and “Trent 892” For example, during LRC at 35000 with a weight of 200,000Kg, the data shows a consumption of 3085 Kg/hr per engine. In Holding mode, the plane has a lower fuel flow rate at elevations as low as 1500 feet, ranging from a low of 2760Kg/hr at 20000 up to 3060Kg/hr at 1500. In other words. the plane can fly for a longer time at lower elevations. And the true airspeed drops from 475 knots to as low as 210 knots. This is the reason you are having trouble to get anyone to agree with you: the distance traveled by the plane at e.g. 10000 feet can be less than half of that traveled at LRC or MRC. Similar data for the 200LR with GE90 engines is available, and it shows the same trend.
@Dave Reed – profuse thanks for responding.
In posting those tables (on the site you’ve visited, under the moniker you name), you will also have noted that I asked for independent corroboration from experts that these were Trent892 performance tables – for the simple reason that they were provided to me as unannotated image files from someone I didn’t know. Five months later: I still await confirmation.
Are you able to confirm that those tables are authentic? If so, wonderful – but then I have several follow-up questions; for example, the 2 tables – one for LRC, and one for Holding – do not dovetail into each other very well (same alt & speed, but very different fuel flow). I’d love to learn all I can about endurance at 323KTAS – under any and all flap configurations.
Dave, if both those tables and your interpretation of them are correct, then how do you explain the ATSB’s assertion (per Fig.3, Oct.8 update) that at altitudes BELOW FL200 (and speeds BELOW around 350KTAS, if you simply backsolve the speeds from their charts), MH370 lacked the endurance to reach the 7th arc? Is the ATSB, in your opinion, dead wrong?
Brock,
I don’t know if the tables are authentic. However, there is a second source at lukas1992.bplaced.net/_777-family.pdf. (I’m avoiding posting links, because my earlier attempts at posting have failed.). This document is a template for FCOMs, so many pages are marked in red “do not use for flight”. However, it is information clearly furnished by Boeing and I see no reason to think the data is wrong.
We don’t need this data to see that low true air speeds are possible at lower altitudes. We can use the data from the Qatar Airways 777 Flight Crew Operations Manual, linked to in Jeff’s “What We Know Now” post. That manual is for the LR version with GE90 engines, but the same trends of lower fuel flow at lower altitudes and speeds is evident.
You comment that the two Trent 892 tables don’t mesh states the tables show different fuel flows at the same altitude and speeds. Actually, in every entry the speed in the Holding table is lower than the LRC table for corresponding altitudes.
Is the ATSB “dead wrong”? I doubt they are wrong, but in any case I think we would all be wise to avoid “back calculating” unless the source data and its underlying assumptions are unambiguously understood.
@whomever would answer it
I would really like a definitive answer on the question of whether an airliner like the 777 can cover ground faster or must necessarily go slower at reduced altitude.
Such few references to the issue I’ve found on aviation forums seem to indicate that reducing altitude compared to standard cruise permits increased TAS, e.g., this discussion:
http://www.pprune.org/tech-log/222127-flight-below-optimum-altitude.html
I suspect that the maximum attainable TAS doesn’t vary that dramatically over a wide range of altitudes, but I’d sure like to see the numbers.
@Luigi:
If you can post the exact question you’d like answered (so I don’t get it wrong), will put it in an email to my cousin. Waiting for him to get back from a trip.
In “MH370 Search Area Still Too Far North, Independent Experts Suggest (UPDATED)” (Posted September 22, 2014 at 12:47 PM), I said:
“The US seemed to arrive at a conclusion as to the specific whereabouts of MH370 BEFORE Inmarsat.”
and
“Malaysia believes (I’d submit, correctly) that ‘data from US spy satellites monitored in Australia could help find missing Malaysia Airlines flight MH370 but the information is being withheld.'”
[https://twitter.com/nihonmama/status/446207783763836928]
The Malaysians’ hunch is likely spot-on.
In the wake of Gough Whitlam’s passing, up pops an SBS interview with former US spy Christopher Boyce (see THE FALCON AND THE SNOWMAN).
At the time he was monitoring Pine Gap (from TRW), PG had a SAT that could see/hear Russia AND China. @ 5:55: http://t.co/lGpccRfSOw
Are we to believe that Pine Gap didn’t/couldn’t *see* MH370?
Interestingly, the interview also includes Boyce’s claim that the US (read: CIA) infiltrated Australia’s politics, which led to Whitlam’s ouster as PM.
@Dave – thanks again for responding.
Re: dovetailing: my tweet to the source of those two unlabeled (so I can’t even confirm they belong to each OTHER, let alone the right plane) tables has gone unanswered for 144 days, now (despite two follow-ups), so I hope you’ll forgive the fuzziness of my memory.
I’ve refreshed it: I was concerned that, for any given combo of altitude and weight, the 2 tables each quoted fuel flow for 1 and only 1 KIAS – and these KIAS values differed dramatically from each OTHER, as you’ve noted. This seemed odd to me, as I would have thought that any two of those values would generally pin the third to within a fairly narrow range. I also seem to recall mutual inconsistencies between KIAS and Ma (BEYOND the required corrections for altitude) being pointed out to me by another pilot. It was enough for me to question whether these tables were in fact reliable.
If you’ve read through those Metabunk threads, you’ll already know that, after its collection of online pilots failed to confirm or deny anything remotely related to commercial aircraft endurance, I tried on my own to corroborate the ATSB’s “too slow hurts endurance” principle in other ways:
1) I found a Delgado/Prats study (link posted to Jeff’s “MH370 Search Area Moves Further South Again” blog, Sept.10 11:55pm) which suggests that, for an A320, endurance is maximized at only about 13% below MRC. Useful, I thought, in relative terms. Spectacularly useful, I thought, when I compared those results to the SE edge of S1/S2/S3, in Fig.3 of the ATSB’s June 26 report: when I fit one point, I essentially replicated the entire performance arc. The key figure is 6a: I extracted those data points, and computed relative endurance (100+Xaxis)/(100+Yaxis) as a function of relative speed (Xaxis).
2) I discovered that, in 2005, the (then) world record for commercial aircraft endurance – not range, ENDURANCE – was set while flying at 514KGS. (If your interpretation of the tables is correct, shouldn’t they have slowed down to 325KGS, so as to smash this record?)
3) I researched the underlying physics. I concluded that, for long flights involving minimal turns, minimum throttle is achieved by getting up and “over” the atmosphere, and staying there. Ploughing through dense air at low altitudes wastes fuel. I suspect that holding speeds are preferable because of the relatively reduced fuel wastage during TURNS – not a consideration for the MH370 southward leg.
4) I read that the ATSB RE-confirmed in October the basic principle that endurance fades at ultra-low speeds/altitudes. If endurance is so “durable” at low speeds, why does the ATSB – here in OCTOBER – still plot an endurance arc that CROSSES the 7th arc at s27=FL200=350KTAS, thereby ruling out everything north=lower=slower?
Finally: I think you are inferring too much from my “backsolved speeds” comment. No fancy model or grand assumption drives out those speeds – for me, it was a simple matter of plotting them accurately in Google Earth, noting their length, and dividing by the Inmarsat arc-provided times. With the turn-south point now narrowly bounded, the position on the 7th arc pretty definitively determines the speed required to reach it.
For the geek squad: I messed up the one and only formula I’ve ever presented on this site (immediately above, in response to Dave, item 1):
/ should be *
because NMI/HR * FF/NMI = FF/HR
(…and I call myself a mathematician…)
Brock,
Apologies if I get this wrong, but to me you seem to confusing endurance and range. Maximum endurance is obtained at the minimum fuel consumption per hour. Maximum range is obtained at minimum fuel consumption per mile. The ATSB ‘performance limit’ is the maximum range calculated for the fuel on board, not the maximum endurance. Airplane cruise performance data (and the delgado/prats paper) are about range, for endurance you have to consult the holding data.
For any given weight and altitude, the speed for maximum endurance is less than the speed for maximum range. Just to give an idea of the speed difference, it can be shown with a set of simplifying assumptions for the aerodynamics (parabolic drag polar) and the engine (constant thrust-specific fuel consumption for jets) that the theoretical maximum range speed is 1.32 (the 4th-power root of 3) times the maximum endurance speed. In practice the speedratio will be somewhat less, mainly because the engine specific fuel consumption is not constant.
Brock (addendum to my previous post),
The Delgado/Prats fig.6a is for FL380/M.78. At those conditions the speed ratio reduces further due to Mach drag-rise.
Brock,
You’re wondering why no one wants to go on record saying a slow flight to the northeast is impossible. Well, it’s not impossible. To reach a northeastern portion of the southern arc, the plane would have to have flown at a slow average speed; this doesn’t necessarily mean it was flying at a slow airspeed. For instance, it could fly fast, land (as per Victor), then take off and fly fast again. It could fly in a zig-zag path; it could fly to the northeast, turn around, and come back again.
Frankly I’m a little baffled as to why you’re so obsessed with this issue. Why do you care whether a northeastern-ish flight route can be ruled out or not? It’s not like anybody seems to think it went that way, anyhow.
Jeff
Hi Brock,
I see that you have started a lively discussion on PPRuNe’s TechLog. Now you have to separate the wheat from the chaff.
Thanks Jeff, for your comments to Brock. I have been reluctant to engage in this thread because it is such a distraction. As we stated on Sept 26th, and ATSB confirmed Oct 8th, the most likely scenario (ATSB A1) leads to the current 30NM X 320NM Equator survey area straddling the 7th arc. Let’s just hope Discovery starts the search along the nominal 7th arc first (most likely end point), and expands out to each side of the nominal 7th arc, rather than starting 15NM inside and tracing back and forth while adding 1 NM to each pass, similar to the Equator sequence. Better to start with the most probable arc and expand out (more and less) if it does not show up on the first pass.
@Jeff: thanks so much for responding.
Yes, I agree with you: if path circuity is introduced, the northern latitudes become accessible. That’s why I added the “swift turn south” condition”. I will clarify the wording of that condition to also forbid landings, etc. – sorry if it wasn’t clear I meant to carve out ALL path circuity from this statement. Your group’s “decompression scenario” turns swiftly, heads DIRECTLY into the arcs (no landing), and ends at s21. This requires 323KGS – too slow – the plane will run out of fuel well before 0019. I am only asking for paths like THIS to be publicly declared infeasible.
Why is this scenario important? Because of the properties it shares with the one the ATSB used to justify where it chose to listen for the FDR (identical, in fact, per REAL-TIME disclosure, and differing only by a murky, now-abandoned path circuity pin the retroactive disclosure). Once ultra-slow paths are definitively ruled out, the next step is to invite the ATSB to explain precisely what they meant by “passed near a NW point at 1912”; if they can’t explain this, then we have exposed a cover-up (it will have been proven they were searching where they knew MH370 was NOT). If we expose a cover-up, we may finally learn the truth of MH370’s fate.
Why is it important to ME? I empathize with the families in their search for closure. Most on this thread – understandably – think the key to this is finding the plane. However, I think – and suspect the families will confirm – that the key to this is finding the TRUTH.
@Gysbreght: no, I am not confusing the two concepts: at 323KTAS, MH370 runs out of fuel before 0019, and thus – if constrained to the 323KTAS PATH – lacks both the range AND the endurance to reach s21. That’s why they’ve taken to just calling it a “performance limit”.
Don’t forget, Gysbreght: it is the ATSB’s own performance line that indicaties quite clearly that, once already at cruise speed and altitude, endurance is actually maximized at surprisingly high altitudes and speeds. Otherwise, why does the performance limit CROSS at s27, as you’ve noted?
Yes, I am very pleased to see the lively discussion on PPRUNE. Some of the comments there are helping me understand the physics behind jet engine fuel efficiency deterioration at low speeds/altitudes – the key to understanding why these scenarios are infeasible.
Brock:
” I am not confusing the two concepts: at 323KTAS, MH370 runs out of fuel before 0019,”
I still think you are not entirely clear. At speeds below MRC the airplane may not have the RANGE to reach the 0019 ARC, but may well have the ENDURANCE to fly beyond 0019 UTC.
@Nihonmama
>> If you can post the exact question you’d like answered (so I don’t get it wrong), will
>> put it in an email to my cousin. Waiting for him to get back from a trip.
You might put the question as follows:
“What is the relationship between altitude and maximum attainable true air speed for a 777 airliner under manual control?”
Notes:
1. Ideally, I’d like to see an answer in the form of a chart (doghouse plot). Specific altitudes of interest might include 35000 ft (normal cruise), 23000 ft (lowest altitude mentioned in Mar 14 NYT chart), 12000 ft (mentioned in an early CNN news story), and 5000-10000 ft (values tossed around in some early reports, IIRC). At the very least, I’d like a fairly quantitative answer on how maximum attainable TAS varies with altitude.
2. To emphasize, I am interested only in maximum attainable TAS, *not* operating speed under various automated flight modes or respecting normally-observed considerations related to fuel economy and safety. I think this would most closely correspond to the “Vne” (never-exceed speed) in aviation-speak, which is analogous to the redline speed on a car.
3. My purpose in asking the question is to determine if there is any substance to the sole justification offered here to disregard abundant evidence of a descent into Malaysian airspace — to wit, the claim that the plane’s estimated ground speed during this phase of the flight is incompatible with such a descent.
4. My question is entirely unrelated to the debates here about the speed, altitude, flight mode and fuel economy during the final southward leg of the flight, a subject about which I have no opinion.
@Gysbreght: no. I will attempt to clarify:
At the risk of sounding pedantic: aircraft endurance is NOT like that of a car travelling along a highway, where the slower you go, the more your endurance INcreases (but not necessarily range, as you note). If this were true, the 7th arc would be accessible nearly all the way up to the equator (if you look at a map, you will see that it curves up to very close to Indonesia); it is HIGHLY accessible in terms of RANGE.
The ATSB limit says – and various independent results confirm – that, any slower than a threshold speed, and fuel flow per hour actually INCREASES as speed decreases further. Endurance – not range – is what prevents access to the 7th arc in the northern climes.
A thought experiment by which we attempt to both drive a car and fly a plane – each at 1mph – might be instructive, here. One vehicle will exhibit maximum endurance; the other will exhibit very poor endurance.
All we’re debating here is HOW slow a 777-200ER can go before its endurance stops increasing, and starts fading (after incorporating such things as power per unit fuel, as a function of altitude) – and I’ve been told by many (including Mr. Exner) that the ATSB’s performance limit should be taken as definitive in this regard.
Max endurance – by unambiguous geometric interpretation of the ATSB’s limit – is achieved at the speed at which the performance limit extends beyond the 7th arc by a maximum percentage of total distance travelled. Per Fig. 3 (June 26 OR Oct.8 reports), this is MUCH faster (and higher) than 323KTAS/FL100.
@Brock, You’re sucking up a lot of the oxygen in this forum. If you haven’t found the answers you’re looking for here, I don’t think you will. Please wrap it up.
Wrapping up (last post on this topic):
Dear IG: I would appreciate it if any of you could publicly agree with the following statement:
“If the performance limit given by Figure 3 in the ATSB’s October 8 update is accurate, the ‘Decompression Scenario’ path depicted in our September 10 report is infeasible.”
Thanks, Jeff. Sorry to trouble.
If the sea is awash with junk I was assuming there would be a bit on the bottom also, and maybe plenty of red herrings for the search team – so far nothing? But some feverish late crunching.
Luigi – Anomalous data ordinarily means the whole lot goes in the bin, particularly as there isn’t much to begin with – but this is not research. Just another in a list of assumptions. Crunchers will insist that they are sure the rest of the numbers are legit, but have no idea what happened to some of it? Not in science – but this is a search.
@Matty – Interesting, isn’t it? No sea floor debris, no surface debris. Sure, this could be an effort to avoid the ridicule like the last round. But whatever became of the 58 rock-like anomalies?
Folks, it’s time to take a deep breath and relax. The most likely resting place for 370 has *never* been searched with sonar. The Fugro Equator has not been searching. It has been surveying. Fugro Discovery has just arrived on scene, and is expected to start the search very soon (hours). If it makes 1NM parallel tracks like the GO Phonix did north of the current Equator survey area, it will require ~320 X 30 = 9600 NM of linear search distance, or about 100 days at 4 kts (a guess on speed). So don’t expect miracles.
Discovery has arrived on scene.
https://db.tt/teFiyPRd
@airlandseaman
Mike,
100 days. Right now I’m as excited as you. Hopefully the Fugro vessels will eventually find 370 in the area recommended by the IG. Your work has always been excellent. On behalf of a group of Chinese people who gathered online to follow/discuss the search of 370 since the very beginning, I just want to express our appreciation and admiration for the IG. Thank you!
Surprisingly, no one has commented the probability distributions shown in figure 5 of the ATSB update of 8 october. Why is the shape of the distribution for the ‘constrained’ paths so different from that for the ‘optimized’ paths? Are both sets of paths generated with the same ‘error models’ for BTO and BFO as defined on page 26 of the ATSB report of 26 june?
JS – Everything corrodes at a snail pace that far down so I was guessing that there would be some assorted junk lying about once you covered enough ground. It could be a frustration to them as it wears on.
@Gysbreght
The constrained autopilot method has a tighter distribution because there are fewer uncertainties and assumptions. Given a baseline assumption that the aircraft was flying under autopilot control at a typical altitude, there are only a few possible modes of navigation, heading or track and airspeed possible. The data error optimization method attempts to minimize the error on BFO observations, which, unfortunately, is a weaker function of the heading. It is weak because most of the AES Doppler is suppressed, leaving a small residual signal.
@Luigi,
Do you happen to have links to the CNN story which mentions 12,000 feet? And indeed any other references to low altitude scenarios?
Thanks,
Kate
@airlandseaman,
Thanks for replying. But I find this is an odd statement:
“It is weak because most of the AES Doppler is suppressed, leaving a small residual signal.”
That is almost (not quite, I admit) like saying that Celsius is a week measure of temperature because 273 degrees of the absolute temperature has been suppressed. If there was no frequency compensation applied by the aircraft, then the Doppler frequency shift would not add anything to the rate of change of the BTO, because it would only reflect the rate of change of the distance to the satellite.
I suspect that the difference in shape is mainly due to the error model that has been applied to the BFO. That error model strongly affects the BFO-based paths, and has little effect on the selection process for the AP-based paths. Unfortunately the ATSB has not felt obliged to elaborate on this.