Australian officials have concluded that the $180 million search for missing Malaysia Airlines Flight 370 has failed. In a report timed to coincide with the wind-down of the two-year-long inspection of the southern Indian Ocean, a panel of experts convened by the Australian Transport Safety Board opined that the plane most likely lies somewhere in a zone of open ocean about the size of New Hampshire to the northeast of the current search area.
This new zone probably won’t be examined. The three countries responsible for the search — Australia, Malaysia, and China — have already stated that no further attempts to find the plane will be undertaken, unless compelling new evidence emerges.
In short, the biggest mystery in the history of modern aviation doesn’t look like it will be solved anytime soon. So it’s a good moment to take stock about what we know and what to expect in the future as we try to make sense of frustrating and tragic irresolution:
The investigators now say they have a pretty good handle on how the plane went down.
Ironically, while admitting failure, the Australian report reflects the experts’ increased confidence that they understand more or less what happened the night of the vanishing.
Based on automatic signals — “pings” — exchanged between the plane and a navigation satellite during the final six hours MH370 was in the air, investigators believe that after the airliner vanished from radar screens over the Malacca Strait it must have taken a final turn to the left and flown south on a magnetic compass heading (one of several possible navigational modes a plane can use). It then flew straight until it ran out of fuel and dived into the ocean at high speed, smashing apart into small fragments.
The scenario would be consistent with pilot suicide, but the report does not mention the secret Malaysian police report leaked earlier this year that revealed that captain Zaharie Ahmad Shah had saved a set of points on his home flight simulator in which he flew with zero fuel in the remote southern Indian Ocean. The simulator data could reasonably be interpreted as evidence he planned a suicide flight, or it could be a freak coincidence. The ATSB has long maintained silence regarding the possible identity of the perpetrator, saying that its job is to figure where MH370 went, not why it went there.
The plane is almost certainly not in the huge patch of ocean investigators spent two years searching.
The investigators long believed that the plane’s impact point lay within a nearly 50,000-square-mile rectangle calculated by Australia’s Defense Science Technology Group. But this high-probability zone has now been searched out using towed side-scan sonar arrays and autonomous underwater vehicles. Apparently, the plane isn’t there.
Some observers have speculated that the wreckage might have been missed by the sonar scan, perhaps falling into the shadow of a seamount or the depths of a ravine. The report, however, throws cold water on this idea, explaining that the technology is capable of searching all but the most rugged 1.2 percent of the search area, and therefore, “There is a high degree of confidence that the previously identified underwater area searched to date does not contain the missing aircraft.”
The new proposed search area probably won’t be examined.
If the plane isn’t in the priority search area, then it must be somewhere else. But the range of possibilities is limited. If it crashed any farther north, the debris field would have been spotted during the massive aerial search conducted just after the disappearance. If it crashed south of the current search area, debris would have been swept to the coast of Australia and likely been discovered by beachcombers. By a process of elimination, then, the endpoint could only be in a fairly tightly constrained area, about one eighth the size of the current search zone and adjacent to its northeastern edge.
“The participants of the First Principles Review were in agreement on the need to search [this] additional area,” the report states. But this extra area is large — about 10,000 square miles — and it would take months and tens of millions of dollars to scan. In its previous agreement with China and Malaysia, Australia stipulated that the search would only continue if “credible new evidence leading to the identification of a specific location of the aircraft” were found. This new analysis will not likely fit that bill.
What if the new area is searched and the plane still isn’t found?
That, the report states, “would exhaust all prospective areas for the presence of MH370.” That is to say, if the plane isn’t there, then the searchers weren’t just unlucky, their analysis was altogether wrong, and something else entirely must have happened to the plane.
But what? One possibility is that they misinterpreted one of the satellite pings. For instance, the ATSB has long puzzled over the value of the final ping but recently became convinced it must indicate that the plane was plummeting in a steep, fatal dive. If this conclusion is wrong, and the plane was instead being held in a long Sullenberger-esque glide by a suicidal pilot, then the plane’s endpoint could lie anywhere in a much larger swath of ocean.
Another possibility is that the ATSB misinterpreted all the satellite data. After MH370 disappeared from radar over the Malacca Strait, it was electronically invisible, flying over empty ocean in the dark of a moonless night. It could have gone anywhere in the world and no one would have been the wiser. Then, mysteriously, just three minutes later, its satellite communication system switched back on. This is not something that happens accidentally, or that most pilots know how to do. And yet, it is this baffling event that provided everything investigators know about the plane’s final hours. Could this strange satcom behavior have been the result of tampering by sophisticated hijackers, in order to feed investigators misleading clues? Twice I’ve asked teams within the investigation whether the satcom data could have been altered; both times they told me that they assumed that it was good.
Now that the ATSB has thrown in the towel, such questions will remain in limbo. The search will not be officially ended, only suspended. This means that according to international aviation treaties search officials will not have to issue a comprehensive final report. And so potentially vital clues about the fate of the airplane will remain hidden away indefinitely.
The mystery will endure.
(This article originally ran on December 21, 2016, in New York magazine.)
@VictorI: I’ve read again what you wrote. I hope someday you can clarify what you meant.
@ROB
“Please could you help clarify something for me? You said recently that at a heading of 180deg, a great circle and a constant magnetic heading were essentially the same? My understanding was a constant magnetic heading would gradually deviate from 180deg as it proceeded south, due to the magnetic deviation.”
You are right to be confused. I am talking fast and loose, and should be more precise. At a true heading of 180, a great circle and the heading track will be the same. I took it a step further and made the assumption that magnetic heading and true heading were close enough not to make a significant difference for a simple first pass look. Of course, the magnetic heading deviation from true depend on location on earth.
It was never really clear in previous discussions when the AP overflew a waypoint whether it continued on the same magnetic heading or the same true heading. My guess it is selectable. In any case whether true or magnetic, only CHANGES in the magnetic deviation (or declination if you prefer) as the plane continues would matter for a magnetic heading. A relative fixed declination would have little to no impact since it would be preserved as the aircraft continued.
Sorry for the confusion. My fault entirely.
@Cosmic:
I have no issues with that and do agree in principle. There are many peculiar things with this flight. But you will also note, as many have here over the years, that if you involve 239 individuals and people in authorities and governments and corporations and air traffic control and airports and search efforts you will sooner or later realise that you are dealing with a mass of people that have enough of singularities to astonish anyone if you look close enough and relate them to one and the same event. Your example with the wedding ring (off the shelf) is worth nada in that perspective and belong in Reader’s Digest at best. And a few more could probably be pulled away. We had a Baltic Sea ferry (Estonia) that sank some thirty years back now; the share of Swedes and not least Finns and Estonians who was related to, knew someone or knew someone who knew someone onboard that ship (or how exactly they counted, i don’t remember) was truly astonishing. I believe all Estonians and more or less all Finns could be counted. And some third of all Swedes (i don’t remember). So when you calculate the odds, you need to take into consideration all the people who are effectively taken into account and what their lives look like day after day.
@Johan
It was not my intention when mentioning the Inmarsat employee, to provoke such a reaction, only mentioned as an anomaly, Merry Christmas
@VictorI: I’ve read again what you wrote and it hasn’t become any clearer. I trust it will become crystal clear when you produce .flt files saved before and after the manual change of altitude, as Jeff Wise requested at 10:42 AM today.
@VictorI: At 45S1 the IAS was 191 kt, but that was at a higher groundspeed. You wrote earlier: “Between 45S1 and 45S2, the user was manually flying at 37600 ft with decreasing airspeed.”
It’s difficult to understand what you wrote at 4:10 PM today in the context of your earlier statements.
@JeffWise @Rob
I had read these pages before. This is an elegant way of ATSB saying that the assumptions used by DTSG in their particle filter model were wrong because MH370 is not located in the area predicted by the model. For those interested, these assumptions are listed on page 60 of the book produced by DSTG authors. The lateral navigation mode assumption is number 3 on the list.
I have a problem with the infinite fuel assumption number 4. They mix up the concept of endurance with range over the ground. Endurance is unrelated to the course of the aircraft and should have been as important a constraint as the BTO and BFO measurements. Not so.
Inmarsat used a very different approach to define the surface search area at the start.
One of the inventors of the particle filter concept is the leader of the DSTG team so it is not unreasonable to see that method selected by ATSB. But I have not seen any discussion of the merits of this approach versus that used by Inmarsat.
It looks to me that Inmarsat was pushed aside by the Australians who were paying the bills for the search.
From the Inmarsat article – “Many techniques may be used to generate an aircraft flight path consistent with the BTO and BFO measurements, bounded by the physical capabilities of the aircraft and its assumed operating mode. Several different agencies worked on this issue in parallel, both independently and collaboratively. What we present here is a simplified flight path reconstruction technique to illustrate how the measurements may be transformed
into a reasonable flight path. It should be emphasized that other members of the
international investigation team developed far more sophisticated models factoring in
aircraft and avionics performance characteristics to determine the final underwater search area.”
More sophisticated does not mean more accurate.
@Hank, Aptly put.
So does anyone care to blow the dust off their fuel consumption tables and take a whack at 33 degrees south?
@JeffWise
As a pilot you know about endurance versus range. For others.
If you believe that the RAT deployed at arc 7 this means that the 43,800 Kg of fuel at 01:07 MYT was consumed by 08:19 MYT with allowance for engine SFC model, fuel measurement accuracy at 01:07, and minimum usable fuel.
The important constraint is that the fuel lasted exactly for an endurance/duration of of 7:12. Not 7:20 or 7:00. This is a huge constraint on Mach and altitude profiles. It has nothing to do with the route or winds. It does not matter whether the aircraft flew in circles. Range and path over the ground is a different problem.
Any flight path that causes MH370 to arrive at arc 7 without exactly zero fuel (subject to some uncertainty) is not viable.
If the 120K km2 zone around arc 7 was achievable with the 43,800 kg, a closer zone would be. But excess fuel is not consistent with the fuel starvation assumption. But there are many flight paths that could burn fuel to bingo exactly at arc 7.
If you assume flight at a constant altitude, there would be one Mach number that would consume an exact amount of fuel over 7:12. Then the route through winds at this Mach would need to last exactly 7:10 at arc 7.
@Gysbreght: This is not complicated. If the altitude is changed in the MAP window while paused, the IAS remains nearly constant but the TAS changes. (As discussed previously, there is also some distortion of the IAS.) If you need precise numbers, you will have to wait.
@jeffwise: It makes no sense to eliminate a terminus because there is too much fuel. Just choose a lower altitude at the same ground speed, which implies a higher IAS, and you will burn fuel faster. For the range of latitudes of interest, the challenge has been proving there is sufficient fuel for a particular scenario, not whether there is too much fuel.
@Hank@all
I have long argued that the ISAT data is not a predictive tool. It cannot be use to define a terminus. it is a qualifying tool. It can be use to rule out the Maldives, Bay of Bengal, Kazakhtstan, and other popular destinations.
@CosmicAcademy,
I don’t recall Duncan ever “speaking out in public on a dedicated blog against the satellite expertise of a reknown Sat provider.” He was trying to correct the impression in the mainstream media and blogs at the time that the satellite was in a geo-stationary orbit. He respected the Inmarsat expertise, and their innovative approach in using the BTO and BFO data to help solve the dilemma.
@Brian
I have issues with Duncan, but competence and integrity are not among them.
@Hank,
@Jeff Wise,
There is no viable route to 33S.
I have tried fitting all navigation methods for over two years and here is a brief summary of what I have learned.
The only BTO/BFO routes ending inside the +/- 40 NM search area (at ~37.5S) are great circles and true tracks, but none of these can reach the 7th arc. They all run out of fuel before 00:17. No wonder ATSB didn’t find anything there.
Magnetic track routes matching BTO/BFO end near 34S. Only Holding speed reaches the 7th Arc, but it has several % excess fuel. You can’t fix this by using a different altitude, because that changes the speed and you lose the BTO fit. You might fix it by having the APU burn fuel from 17:23 or even18:23 until fuel exhaustion, but then what would power the SDU reboot at 00:18? You also can’t fix it by assuming a constant KIAS was selected instead of Holding for the same reason. Finally, it requires two southward turns, one prior to 18:40 to ~205 degrees and then a second one to the south. For all these reasons, I don’t consider a magnetic track route to be a realistic candidate.
There are no magnetic heading routes that fit the BTO/BFO.
True heading routes fitting BTO/BFO end at 35S. Only Holding speed has sufficient endurance, with PDA ~3%. Right on the money for 40,000 hour engines. A single FMT at 18:38 passes through Anoko. A route discontinuity there sets the default nav method to TH. In my opinion, this is the only viable route. That’s it. Just one. It’s very surprising. It has been searched, but not to the full width.
In my opinion a great circle route to 23S is not a viable candidate because it has a very long loiter, it does not appear to match the debris drift predictions, and the air search failed to locate floating debris there.
The DSTG probability map is almost fatally flawed because it did not include an accurate fuel model. That would have eliminated everything south of 36S, which is most of the integrated probability and also most of the 120,000 sq km.
If you ask a pilot, as ATSB did, which navigation methods he would use, the answer is obvious: LNAV (great circles) or magnetic heading. They normally don’t fly anything else. It’s too bad ATSB did not ask the FMC which it would choose when it had the chance. Maybe we’ll find out someday.
@SusieC:
I know you weren’t. Got carried and was curious about Fairbairn myself. Good we perhaps have gotten further there. The Estonia was twenty years ago by the way. Not thirty.
I would perhaps not call Duncan Steel “world famous” either, but he’s a decent guy. (I don’t pretend to know him).
Merry Christmas to you all. We are starting now.
@Gysbreght. Sim points again. In my view, more likely than sitting there for some time during the leg south what he would have done was fast forward from co-ordinate 3 (10N) to 4, (45S1), saving the flight file as he eliminated fuel, experimenting with the software. A 30-odd seconds pause there hands-off while the aircraft turned slowly left 15 deg @ something like 0.4 deg/sec (average HVel world at this and the next point), while traversing the couple of nm to 5, 45S2), when he entered a drop in altitude. The only purpose I can see for that is again an experiment to see how the program reacted.
Returning from surmise to specifics and the one batch of good in-flight data, at co-ordinate 2 (5N) during the trip up the Strait , the sideslip (XVel body axis) there of over 1700fpm is to me a puzzle, zero rudder trim, nil bank. Any ideas?
@Bobbby Ulich. As you know the ATSB had Boeing fuel consumption estimations which were compatible with “the DST Group PDF” (Dec 15 Definition of Underwater Search Area.
Bu anyway, about your,”You might fix it by having the APU burn fuel from 17:23 or even 18:23 until fuel exhaustion, but then what would power the SDU reboot at 00:18?” It is possible that the APU would cut out when the left main fuel pump lost pressure, then when the APU fuel pump cut in, accessing the ATSB’s residual fuel it might autostart. Very speculative and a maybe which could be looked into if worth it.
To add to confusion, as to residual fuel I have raised doubts about that before. With the new confidence that the aircraft would enter a steep dive early after fuel exhaustion that supply looks even more tenuous.)
@David,
Yes, of course I am aware of the basic Boeing range estimates. Unfortunately, these have never been described in sufficient detail to be independently calculated.
But the search results to date also seem to indicate they are either wrong, or they don’t matter.
Here’s why. The fuel model doesn’t change the fitted route. It only allows one to estimate the PDA for that route. If the Boeing fuel calc’s were correct, and if the correct route were either a great circle or a true track, ATSB would have found the aircraft already since it would be in the center of the searched area. Since there are no magnetic heading routes that fit the sat data, so that only leaves mag track and true heading. The mag track has 2-turn FMT issues as well as the fact that no one can imagine why anyone would ever fly such a route. So we are left with only true heading. With reduced fuel flows (I.e., without the temperature compensation) one can fit the same route by using a higher speed setting such as MRC but at a lower altitude so the ground speed is the same. In addition, the endurance is the same with a PDA near 3-4%. The end point is also the same at 35S. Therefore you still have only one solution. True heading to 35S. It does not matter at this point whose fuel model you believe. The predicted location stays the same.
Think about it this way: the lateral navigation method has a certain ground speed to fit the sat data. You can fly that same ground speed at different fuel burn rates just by changing the speed mode and the altitude. Changing the fuel burn rate changes the PDA needed to achieve the known endurance. Then one can compare the calculated PDA with the known/estimated value to see which combination of speed mode and altitude was actually flown, but that is basically an academic exercise. It does not change the end point location. The only location where the fuel model actually determines feasibility is 37.5S, and we already know the aircraft is not at that location.
@David
IRO the APU endurance, one other thing to possibly add to to the mix: The RH flaperon body appears to have been broken off relatively cleanly from its two hinges, at the same point, close underneath the flaperon underside. This, in my opinion, would only happen if the APU was running at the time of impact, and powering both hydraulic actuators. If the APU had not been running, the RAT would have been the only source of hydraulic power, and the RAT can only power up the outboard actuator. The inbosrd actuator would be bypassed, and offer no resistance to inboard hinge movement. The flaperon would have been twisted off, in other words it would have been torn away from its hinges in a progressive manner, if only the outboard hinge offered resistance to torque forces.
@VictorI: If the IAS remains nearly constant then the dynamic pressure should remain nearly constant. I’m waiting for your .flt files.
@VictorI
I find your remark; ‘@jeffwise: it makes no sense to eliminate a terminus because there is too much fuel’ and further explanation interesting.
To me it suggests the difference between possible ghost-flight flight paths and possible flight paths with a consious pilot behind the controls before and after FMT.
With the latter too much fuel could be burned several ways as you suggest or it could be jettisoned too IMO.
Both though require a pilot in control after FMT.
Which IMO is a far more logical basic assumption then the basic assumption this whole search was based on: A pilot controlled flight that for some mysterious, unproven, unlogic reasons turned into a ghost-flight after FMT.
The fact that the search failed so far IMO is a strong indication it wasn’t a ghost-flight before or after FMT.
@DrBobbyUlich
Just so its clear – if the APU is burning fuel from 17:23, which engine
runs out of fuel first, the left or the right?
What is your view on what the Cost Index was set at?
IMO it comes down on going back to the drawing board.
But then based on the assumption the flight was an all pilot-controlled flight.
After FMT flown in a mode leading to a probably pre-calculated destination somewhere north of 36S.
The debris and decoy based drift-analysis now limit the crash area between ~35S and ~30S.
The Inmarsat data could cover a much wider range of possibilities as for one @Brian Anderson suggests. Which the drift-analysis now exclude.
In a new attempt based on an all controlled piloted flight it could be usefull to find Inmarsat-data based flight-paths that match the new drift-analysis based crash area IMO.
Merry Christmas everyone!
@DrBobbyUlich said, “You can’t fix this by using a different altitude, because that changes the speed and you lose the BTO fit.”
That is only if you are constraining yourself to certain autothrottle modes or other constraints in your model. If you are using SPD, you can lower the altitude, keep the ground speed the same, and increase the IAS. This would increase the fuel burn.
@David: What you believe is sideslip at 5N is really due to crosswind. The wind is 270/25 at this point, and the wind correction angle is about 2.3 deg.
@Gysbreght: If you check one of my recent posts, you will see that I explained that the dynamic pressure value is erratic. Your argument is based on false data.
@VictorI: That depends on what you consider to be ‘false data’. We’re not talking of a slight drift here.
Between 45S1 and 45S2 the dynamic pressure increased by a factor of 3.29. Do you consider that a “gradual readjustment”? And isn’t it a strange coïncidence that the gradual readjustment just happens to coïncide with the increase of airdensity between 37650 ft and 4000 ft?
@Gysbreght: “Gradual readjustment” referred to the rate of change of that adjustment, not the cumulative amount of change. The readjustment continues while the simulation is paused. And no, I don’t think the correlation of the dynamic pressure to air density is random. It is nonetheless an incorrect value.
I could spend a lot of time trying to understand exactly under what conditions the dynamic pressure results in a particular value when a parameter such as altitude is changed in the MAP window. This would involve studying how the value is affected by the timing of changing the variables and saving the flight file, all while the simulation is paused. Yves first alerted me of this anomaly. I verified for myself that the value was incorrect and was dependent on the timings of the save. For me, that’s enough to reject the value as incorrect, and not try to use it. I am advising that you do the same, the same way I advised that other variables in the flight file should be ignored.
It’s your choice as to whether you want to continue to use bad values to concoct incorrect theories such as simulated flying in gale force winds.
What I am able to confirm is Yves’ results that if you start with the 45S1 condition, you can manually fly the plane by leveling out of the bank and maintaining altitude to achieve the pitch, bank, heading, and position at 45S2. We can have confidence in these particular values in the 45S2 data set because they were not altered when the altitude was manually changed from 37,600 ft to 4,000 ft.
Another parameter that Yves checked was the spool down of the engine, as indicated by Pct Engine RPM (N2). Yves found that it takes 68 seconds from fuel exhaustion to attain the value at 45S1. It takes another 27 seconds to reach the value at 45S2. This is another indication that the aircraft was flown between 45S1 and 45S2.
In short, there is no mystery about how the plane was flown between 45S1 and 45S. It was manually flown at near constant altitude and with pilot input. After the simulation was paused at 45S2, the altitude was changed from 37,600 ft to 4,000 ft, and the flight file was created. We have no knowledge about the simulation after that point.
If you have further questions, perhaps you can contact Yves directly. His email address can be found on the title page of his flight dynamics paper. He is an acknowledged expert that has consulted for companies on the flight dynamics incorporated in Flight Simulator. I have found him to be knowledgeable, precise, open-minded, and responsive. He was an ideal collaborator for our paper.
Respected Sir / Madam ,
I am regularly following the updates on MH370 search . I feel very sad for the MH370 families .
As i was thinking all these days where the plane could have been in-spite of the exhaustive search that is being conducted without any result tilll date .
One rare possibility that occurred to me is that , The Plane could been submerged in sea and is prevented by a thick Antarctic ice sheet from surfacing .
The plane could be under the Antarctic ice sheet somewhere . This is my wild Guess .
I just wanted to share my thoughts and this remote possibility that came to my mind.
Good Luck
Regards
Ramesh
@VictorI: When a scientist talks about “readjustment”, shouldn’t he be curious what it is adjusted to?
@Gysbreght: Speaking of curiosity, the plain fact is that you are obviously not curious enough to do your own experiments, as I have been advising you do now for some time. On the other hand, I was curious enough to install FS9 and FSX, learn the intricacies of the software, run my own experiments, and collaborate with an acknowledged expert in the field, from whom I learned a great deal more.
If you believe there is value in studying what causes the erratic values of the dynamic pressure, I encourage you study it for yourself. But until you do, and you are able to fully understand the meaning of that value, you are being intellectually disingenuous to use that value to concoct theories when you have been advised by an acknowledged expert in the field (Yves) that the value is incorrect.
@VictorI: “you are being intellectually disingenuous”
It’s time to quit this exchange.
@buyerninety
If there was a field of anal-retentive savants, you would have to be the best. Your literal diligence here pushes us to a higher standard, thank you.
@Rob
I hope you do not find my jestful comment offensive. It truly must be a constant struggle to tame and focus the double edged sword of your HFA. Most of the time (teasing) I feel fortunate to witness a small part of your process.
@all
Just wanted to wish everyone a Merry Christmas and Ed – thanks for the kind words a few pages back. Much appreciated!
@Jeff
Is there any chance of a paperback version of The Plane That Wasn’t There being available? If not I’ll find some way of getting it on iPhone. Thanks!
@VictorI,
Yes, if you are not using the usual ECON or Holding autothrottle modes, and if you change both the commanded IAS and the altitude in the correct way, you can achieve a constant desired ground speed with different fuel flows and therefore different PDAs to achieve a given endurance.
@DrBobbyUlich, In other words, in order for the fuel to have run out around 33 degrees south, the person flying the plane would have had to have chosen in a deliberately inefficient manner.
@buyerninety,
Thanks for your excellent questions.
The Flight Plan Cost Index was 52 (ECON 52). I have primarily been looking at LRC (ECON 180), Flight Plan (ECON 52), MRC (ECON 0), and Holding. The last ACARS data before diversion are consistent with ECON 52 at FL350. It is clear that the radar track from ~17:23 to 18:22 was flown at higher speed, and LRC at FL360 matches it rather well. If my fuel model is correct, a speed lower than MRC (Holding, actually) is necessary after the FMT to match the fuel exhaustion at 00:17:29 with the expected PDA. No ECON speed works in this case. Ignoring the temperature increase in fuel flow, which is similar to the Boeing results, speeds between Flight Plan and MRC are possible. LRC is not; the PDA is still too low. Similarly, Holding is not viable in this case because the PDA is too high.
Operation of the APU from 17:23 until 00:20 uses about 2.8% of the available fuel if it is electrically loaded and less if it is not. The primary effect on fuel flow is actually the increased aircraft drag due to opening the inlet door, and subsequent increase in fuel flows to both main engines. I’m not sure whether APU operation would change the fuel balance between left and right tanks. Perhaps you or another reader can answer this question. In my opinion, most of the extra fuel flow is shared almost equally between left and right tanks (because of the aircraft drag), and therefore it would not change the fact that the right engine would flame out first regardless of the APU operation.
@Jeff Wise,
You said: “In other words, in order for the fuel to have run out around 33 degrees south, the person flying the plane would have had to have chosen in a deliberately inefficient manner.”
What I said was that there is no autopilot navigation mode from FMT onward that produces a 7th Arc terminus at 33S and which is consistent with the BTO/BFO data. The details of the fuel model and the exact combination of speed mode and altitude are immaterial to this conclusion.
I also said the fuel model is an academic exercise at this point in time. It can only rule in or out the straight and fast routes ending near 37.5S, and the unsuccessful search there has already eliminated the straight and fast routes. For the remaining slow and curved routes that do fit the BTOs/BFOs, it is possible to achieve both the required ground speed (to match the BTOs/BFOs) and fuel flow (to match the expected PDA) because we have two independent variables to adjust (speed mode and altitude). Many combinations give the same ground speed, but only one of which produces the expected PDA. This is true for any reasonable fuel model, and one can find a slow and curved solution regardless of whether you use the lower or higher fuel flow model. The higher fuel flow model gives Holding at ~FL370, and the lower fuel flow model requires Flight Plan or MRC at ~FL320 for the same true heading route. In my opinion, the Holding at FL370 makes more sense than the Flight Plan speed at FL320, but that is just an opinion. Both fit the sat data and give similar PDAs in the expected range,
@DrBobbyUlich: First, there is not a HOLDING autothrottle mode for flying route legs as you claim. If a pilot wishes to fly at holding speed while not in a holding pattern, he could use the CDU to open the HOLD window in the FMC, select PPOS (present position) as the Next Hold, and note the Best Speed, without actually choosing to enter a holding pattern. This speed could then be entered by pressing the Speed Button knob in the MCP, which opens the Speed window, and the speed can be dialed in. But the best holding speed changes with weight, so to stay at the holding speed requires pilot input along the route. The plane would actually be flying in SPD mode. Without pilot input, SPD would remain constant.
Secondly, flying in SPD mode is not at all unusual, although flying at holding speed between waypoints would be. In fact, SPD mode is commonly used when outside of radar range so that ATC can maintain maintain proper spacing of aircraft.
@all
Season greetings to everyone 🙂
May the New Year ahead find the answers everyone is looking for.
@VictorI,
Thanks for the information on the steps to enter a Holding speed. Which document best describes the procedures you mentioned?
@DrBobbyUlich: The information on automated flight is distributed across the FCOM Chap 11. Also, I have gained considerable knowledge by flying flights from takeoff to landing using the FSX PMDG 777 simulator.
If you have found an autothrust mode in which holding speed is continuously calculated and maintained without pilot input, I’d like to see it. I don’t think it exists.
@DrBobbyUlich.”I’m not sure whether APU operation would change the fuel balance between left and right tanks.” The APU draws fuel from the left main tank. Normally the tank crossfeeds are kept closed.
@Victorl. Sideslip. Yes as you say this is crosswind. My body vectors defaulted to the conventional.
Falling from the engine rpm at 45S1,”Yves found that it takes….another 27 seconds to reach the value at 45S2.”
I have the engines at 45S1 already at only a thousanth of a percent, 0.30rpm, so little left to slow further. Are we talking about the same figures?
Separately, I would expect the engines to be windmilling a deal faster than that. Maybe engine speed is from a false datum?
@VictorI.I see “Pct rpm” from elsewhere is really percent upon a hundred though the above still applies at 30 rpm.
@Susie Crowe
Please be assured, I try always to take your good natured teasing in good spirit. Yes you are right on the button, it is indeed a two edged sword. Happy Christmas.
@ all
A MERRY CHRISTMAS to ALL, and Happy Hanukkah.
@David First, the 100% value of N2 for a GE-90 engine is 9,332 rpm. As I explained in the paper, the PSS B777 uses an incorrect value of 29,920 rpm.
Relative to the coastdown and windmill rotational speeds, I don’t believe that the PSS B777 accurately models these. However, since the coastdown curve after fuel exhaustion is repeatable, we can use the RPM to estimate the time in the simulation that elapsed after fuel exhaustion, as Yves has done. This allowed the calculation of the elapsed time between 45S1 and 45S2. It was quite clever.
So at 45S2 we have an anomalous AGL and an anomalous dynamic pressure. I wonder, is the pitch value also anomalous?
@Gysbreght: The value of AGL is the altitude before it was changed using the MAP window, and therefore acts a marker of the previous altitude. The pitch doesn’t change when a value in the MAP window changes, so we have high confidence in its validity. The dynamic pressure changes in an unpredictable way with a change in altitude, and should be ignored. This has all been explained before.
@VictorI
Can I run this past you, please?
The scenario: the aircraft is navigating in LNAV, outbound from ANOKO, proceeding toward ISBIX, commanded constant airspeed M0.78 at commanded FL350, intending to stay on this same great circle path, at same airspeed and altitude until fuel exhaustion, but the pilot is incapacitated for some reason, before he can input a final, manual waypoint. On reaching the route discontinuity at ISBIX, the autopilot reverts to constant magnetic heading of 186.23, and continues at constant M0.78, at FL350 until fuel exhaustion. In your estimation, would it then cross the individual arcs at the required times, and cross the 7th arc at a point between S32 and S35.5? Or would this be impossible, without a gradually reducing airspeed?
Assuming FMT at ANOKO occurs at 18:36, and ISBIX is overflown at 19:28:30.