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Originally Posted by RichardC10
(Post 8386704)
I have done some simulations of whether the route of the flight could be determined if the arcs from the interim Inmarsat pings were available. So far we only have the final arcs (the north and south 'corridors').
I used the final published arc as the set of possible ‘destinations’ of the flight. One example destination on this arc was chosen, this determines the speed and heading from the last recorded radar position to achieve that final position, and hence where the hourly pings would be emitted over the 7 hours of the flight (and thus the distance from the Inmarsat sub-satellite point, which is what Inmarsat measures). A constant speed and heading was used as a first approximation. The results of this example can be compared with the same calculation for each point along the published final arc, each of which requires a different heading and speed from the last recorded radar position and generates a different set of predicted ping arcs (distances from the sub-satellite point). An overall error can be calculated for each point along the published final arc. The result is that there is only one constant heading course from the last recorded radar position that matches the example set of ping arcs, that is the destination is uniquely defined by the interim and final ping arcs (if interim arcs exist). There is a (rough) mirror course in the southern hemisphere which may be hard to distinguish as the last recorded radar position was close to the equator. I also added a random error (noise) to the ping signals derived from course to the example destination, with the magnitude of the error being 50km on the ground (Gaussian, one sigma). This increases the error in deriving the final course giving an uncertainty of around plus/minus 100km in recovering the final destination – but it does not invalidate the technique. I haven’t yet tried putting in a course with a change of heading along the route, but the method seems quite sensitive so I suspect such a course change could be recovered from the data. Many headings or speed changes would increase the final error, obviously. So if the interim pings are available (to someone), and hence their arcs, it is very likely that the destination (or at least one in each hemisphere) could be derived with reasonable errors, at least up to the final ping. Notes: 1. This is a rough piece of work done quickly to see whether the concept works. I have made a few assumptions that seem reasonable. 2. in this first try I have used simple Cartesian geometry (flat plane) rather than spherical geometry. The differences are relatively small as the area covered is reasonably close to the equator. A full spherical interpretation will not change the conclusion that the set of arcs define a single destination (or rather one in each hemisphere) but obviously would be needed to interpret the actual interim ping arcs. There was a post earlier today where someone was referring to rhumb lines and loxodromes, he reckoned with all pings you could use them to calculate various heading data, me no idea what they are, just wondering if you did and is the idea useful |
papershuffler said
The Malaysians' trust in the US may be ebbing as many of the recent stories come from 'US sources', i.e. leaks, and are critical of the Malaysians. If there is sensitive data you really need to know it's not going to go any further. The Malaysians may be thinking, 'You're going to blame either our pilots, procedures, or maintenance instead of your US-made aircraft, why should we work with you?' Would you want to work with someone who may not be able to help, and could just stab you in the back, repeatedly? Then insist that you are to blame as their investigative bodies may conclude (e.g. Egyptair)? (During one of the investigations I worked on several years ago, a copy of a request for information to a US state containing many sensitive details was uploaded to the state's public online library and made available for all to view. The state refused to remove it . It made relationships rather frosty.) First, those "leaks" are pretty much the only reason 14 countries aren't still wasting time looking in the Gulf today - remember, the official Malaysian position pretty much never changed from it going down there until US Officials "leaked" the plane flying for 5+ more hours... (only after which time did India and Australia really get involved searching places the plane could actually be) Second, the Malaysian Governments biggest concern should be trying to find 200+ lives that may be able to be saved for all anyone knows Third, the Malaysian Government can clearly not even begin to do this themselves, and has more than a little issue with transparency, consistency and even coming to grips with basic common sense (how long were they going to keep us looking in a gulf they knew on day 1 they had evidence it wasn't in, anyway? And how long was it going to take before they took seriously the possibility the pilot could ever be involved? And on and on...) Forth, it is hardly JUST the US that is telling them to be more transparent; we have seen similar from just about every country involved in this search (especially Vietnam and China, the two countries Malaysia jerked around the most at the beginning of all this) Shoot, there are even endless reports that most of their own people and a few scattered officials are furious and distrustful of the way Malaysia is handling this! Lastly, you seem to be under the impression it can not under any circumstances ever possibly be the "pilots, procedures, or maintenance" that is at fault here and absolutely MUST be because it was a "US-made aircraft" - being you have a god-like ability to be so all knowing, I suggest you tell the Malaysian Government exactly what happened and where the plane is then (just don't feel too bummed when they dismiss you outright; you have to understand they have actual evidence saying whatever your theory is, it is already basically impossible) As I said before, just a flat out disgusting post consistent with a useless tin-foil hat wearing conspiracy nut, not a person with even basic level of critical thinking that should actually be taken seriously by anyone It's offensive really even having to read the drivel when we have people possibly laying somewhere dying because of the Malaysian 'maybe we'll help, maybe we won't - we'll tell ya later' games with all involved; games you apparently full-heatedly support them playing |
As opposed to earth orbiting which is what the GPS satellites are. Hence the ability to get a 3D fix using the latter
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Tomnod FWIW has released image maps of what seems to be the Australian Search sector - Indian Ocean
Example: Tomnod lat, lon 4.213168, 90.440788 |
Final ACARS report detailed it. I will try to find the posts that reported this.
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Originally Posted by GarageYears
(Post 8386247)
I keep seeing questions related to why the SATCOM system was sent pings, etc, and discussion related to ACARS use, MAS subscription to the ACARS reporting service to Boeing (or not), but isn't it also the case that the SATCOM transceivers at ALSO available for voice comms?
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Originally Posted by RichardC10
(Post 8386704)
.
The result is that there is only one constant heading course from the last recorded radar position that matches the example set of ping arcs, that is the destination is uniquely defined by the interim and final ping arcs (if interim arcs exist). There is a (rough) mirror course in the southern hemisphere which may be hard to distinguish as the last recorded radar position was close to the equator. |
Originally Posted by papershuffler
(Post 8386626)
The Malaysians may be thinking, 'You're going to blame either our pilots, procedures, or maintenance instead of your US-made aircraft, why should we work with you?' |
Deriving the course from the Inmarsat pings
Originally Posted by Heli-phile
And......?
So what heading/ speed did you use and was was the results? |
"Be transparent" could mean anything up to "we know exactly what happened to the airplane and we know that you know. And we are giving you a chance to announce it first." Just saying. That is a valid position to take, as it is their airline, and the flight originated in their capital. A number of nations will doubtless be happy to assist. The UK and US are obliged to since Engines and Aircraft were built in those two nations. Therefore, UK and US will be none too interested in a cover up. What they'll want is an actual investigation. My experience with morals and ethics in the third world advises me that this requires some effort to elicit, and pressure at time not to fall into the same old same old corruption that a certain airline captain was vocally against. Without considerable international pressure, I don't have faith in important evidence (e.g. maintenance records) making it to the investigative team, whoever and wherever they may be. We've seen it all before; as time goes by, the shock will abate and career- and face-saving will take precedence, if it hasn't already. It will be interesting when/if the fate of MH370 is finally discovered, how much involvement the Malaysians wish to take in the proceedings. (Personal opinion/suspicion: if it hadn't been (more-or-less) confirmed that the FO Fariq Abdul Hamid was the last voice heard and therefore still alive, I suspect the negative stories discrediting Capt Zaharie would have gathered more pace...) |
rigbyrigz,
Thanks for more confirmation of the WP being changed pre-ACARS report. Think I will still leave it as "apparently" though, as some data seems to be "confirmed" then debunked later when Malaysia decides to actually share the data instead of whatever they decided their theory of it was at whatever moment. As far as your note - any system failure would have sent out an emergency ACARS. If the Transponder did drop because of a catastrophic event it would have. If merely turned off, I am not 100% sure. (but I think it would have) Hopefully someone else can clarify that last bit |
Originally Posted by GarageYears http://www.pprune.org/images/buttons/viewpost.gif I keep seeing questions related to why the SATCOM system was sent pings, etc, and discussion related to ACARS use, MAS subscription to the ACARS reporting service to Boeing (or not), but isn't it also the case that the SATCOM transceivers at ALSO available for voice comms? Yes, 777 cockpit SAT comms out of the tin, and optionally, in-seat passenger satellite linked phone service. Right, so that puts to bed the occasional "well-if-they-aren't subscribed to Boeing's data monitoring... why does the satellite ping them" comment I've seen. The pings are there just as much for the cockpit voice comms link, as any data that may or may not be sent over the same link. |
Deriving the course from the Inmarsat pings
So what you have done is say you cannot join the dots if there is only 1 dot..... OK
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That last PING arc.
There still seems to be confusion over the 40° elevation angle arcs accredited to the last 'ping' timed by the Inmarsat IOR at 64°E over the equator.
The graphic below should provide insight into how that elevation relates to any angle subtended from the earths center in any plane. Note the graphic doesn't indicate the top or bottom of the earth sphere is North or South, as it could equally be 154°E or 26°W. Also, from 35,768km above the equator, the full disc is not seen, as reference to the graphic will show. 90° elevation is on the beam centerline, but at an earth elevation of 50° the angle subtended from the center of the earth is 35° and the angle at the satellite is 5° of its overall half beam-width of 8.7°. http://oi62.tinypic.com/kvrqt.jpg When plotted on a transverse Mercator chart/map, the ring drawn will start being circular immediately below the satellite, but as the angle gets bigger the Mercator projection makes the projection elongated in a polar direction. If drawn on a equidistant projection, the circles would remain just that. Those who have referred to the AMSA search graphics will note that the tracks supplied by the NTSB are based on two different ground speeds, and they reproduce the diverging tracks. The track indicating the faster speed is the westward one. |
For me this looks like there has been failure situation / slow decompression or problem with Oxygen for crew, they might have started diversion, altitude change, possible some issue with the Avionics, I don't know the T7 systems, so can't comment on details of this. At one stage they have BOTH become incapacitated, and descended in altitude, flown on until running out of fuel (Similar Helios) What exactly caused this to happen, none of us can only speculate in, but what is important is to create the most likely scenario and work with this. Most such scenarios it will the most simple and least spectacular version that will be the truth. Unfortunately it doesn't seem what is postulated is the simplest solution to all the information that we know, even if that answer isn't one that we'd like it to be. Coming up with a half-baked hypothesis (and I'm not trying to insult anyone here) and suggesting the plane flew off in the murky blue yonder for 7 hours or so until it flamed out, doesn't seem to fit with the last radar track point and the INMARSAT ping arc. |
What are all these photos turning up in the media of jets in the jungle.
jets under the water "showing" wings and windows ? Have they all been debunked and the media just using them to sell newspapers ? |
Range can be extended by lowering cruise speed?
The Malaysian government has released an image showing maximum distance aircraft could have travelled - is this based on range at cruise speed or less?
As far as I know, range can be extended by flying at slower than the typical cruise speed listed as 490 kt? What is the best range speed? Speed The speed which gives the maximum range for a given aircraft weight and altitude is called best range speed. Flying at higher speeds than the best range speed increases the drag and the fuel flow, and therefore reduces the range. Lower speeds than the best range speed reduce the drag and the fuel flow, but they also reduce the distance traveled per time which is more dominant, and therefore reduce the range. SKYbrary - AP4ATCO - Factors Affecting Aircraft Performance During Cruise |
Waypoint programmed but not executed.
For direct access to my "nearest suitable", I have often pre-programmed (but not executed) a "Direct to ABC" and sat there watching a dotted pink line with an accurate track arc peeling out from the nose.
Would that sort of behaviour cause a log event in the ACARS or would you have to "Execute" for it to log? |
ACARS at 1:07
If a plausible theory says that the 1:07 ACARS is that of the 12 minutes window to change a waypoint to do the westward turn. I wonder if it is likely the other subsequent waypoints of the new path that are keyed in would appear in the ACARS message? Afterall ACARS contains enough capability of interfacing with the FMC on flight path changes - in uplink and downlink modes.
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Do we actually know, other than third hand unsourced rumours from Reuters or the WSJ :
1. if the thing actually flew through the waypoints then turned to the new tracks, or just flew near them ? 2. when Vietnamese or Malaysian air traffic actually declared a SAR phase and messaged this to neighbouring country's air traffic services organisations ? 3. if Burmese or Bangladesh radar ever painted anything ? 4. if 'goodnight' etc was all that was said (bad) or was just tacked on to the end of a normal frequency change acknowledgement (good) ? 5. where the story about the new wpt in the FMS came from ? Until we know these for sure, all that we know is that the aircraft is ... missing. |
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