Malaysian Airlines MH370 contact lost
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If you knew the accurate groundspeed hour by hour you will finish up with a very narrow probable track band.
As you increase the speed range you will get a wider band.
I presume from successive Doppler they have been able to deduce a reasonable accurate speed range hence the track band was determined and the cessation of transmissions determined the track box length.
As there is uncertainty between transmission cessation and aircraft crash they would attempt to refine the box based on estimated fuel exhaustion. Fuel burn is probably the most problematical of the assumptions, next is the descending flight path once transmissions ceased.
The flight path could be near vertical as some have supposed or a shallow glide in any direction.
And lastly there are the pings.
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I presume from successive Doppler they have been able to deduce a reasonable accurate speed range hence the track band was determined and the cessation of transmissions determined the track box length.
The speed is calculated from a 777s' performance envelope (they knew how much fuel it had, and when it presumably ran out.)
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The zigzags would have had to be very consistent otherwise the arc angles would not have been uniformly spaced.
The aircraft vector in relation to the satellite will exhibit a Doppler shift or did I miss something?
The aircraft vector in relation to the satellite will exhibit a Doppler shift or did I miss something?
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You've got it right, but I don't think the doppler shift provides enough precision to determine speed. But I don't know that it doesn't either. I just haven't heard any claims of such.
You have a good point about the linear pattern of the later shifts displayed in the burst chart. That does indicate continous cruise with no turns.
You have a good point about the linear pattern of the later shifts displayed in the burst chart. That does indicate continous cruise with no turns.
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Propduffer, I suspected you referred to Doppler as a speed indicator; I didn't, I referred to it as a direction indicator - Doppler low to mean opening range.
olasek, in theory. In practice at the precise moment of the ping time the aircraft would have had to present the same Doppler as the previous pings.
olasek, in theory. In practice at the precise moment of the ping time the aircraft would have had to present the same Doppler as the previous pings.
I feel it likely that the person flying the plane wasn't aware of the ongoing handshakes between the satellite and the aircraft. Everything else was turned off - transponder, ACARS, no response to ATC. Why leave another form of "communication" alive - unless you were unaware of it.
So I think you have to assume a relatively constant velocity once established on the track south. If you believed you were completely "dark", the most important consideration was distance. The further away you got, the less likely you would ever be found.
Anyway assuming a constant velocity is already a difficult enough task. To try and calculate the effects of random changes during this final leg would appear pointless on the grounds of futility.
The recent comment about the inflight entertainment is intriguing. Things started to happen while passengers would still have been awake and some would have been watching flight path (or whatever moving map package was part of the IFE). So is may have been necessary to disable the IFE so passengers were unaware of the turn back. If so, that implies the turn back was very gradual. If on the other hand the plan was a steep climb with the packs off to disable the passengers, the IFE doesn't really matter. Why worry about the IFE if the passengers were about to be aware there was something wrong but would shortly become incapacitated. So something here doesn't quite fit.
The other thing is the passenger phones. I know some hear are sick of discussions about phones. But after 2 months searching I don't think we are in a position to discount any possible information that could aid understanding. A low level flight across Malaysia would have generated calls from any able passengers. And also handset registration with the phone networks from any phones left (on even if all the passengers were disabled at this point). So that doesn't make sense either. Possibly a phone jammer. Even an accomplice in the cabin could not have ensured that all phones were put in flight mode and / or turned off.
The other thing that would concern me as the pilot would be the chance that one passenger (and it would only take one) might have a sat phone on board.
So I think you have to assume a relatively constant velocity once established on the track south. If you believed you were completely "dark", the most important consideration was distance. The further away you got, the less likely you would ever be found.
Anyway assuming a constant velocity is already a difficult enough task. To try and calculate the effects of random changes during this final leg would appear pointless on the grounds of futility.
The recent comment about the inflight entertainment is intriguing. Things started to happen while passengers would still have been awake and some would have been watching flight path (or whatever moving map package was part of the IFE). So is may have been necessary to disable the IFE so passengers were unaware of the turn back. If so, that implies the turn back was very gradual. If on the other hand the plan was a steep climb with the packs off to disable the passengers, the IFE doesn't really matter. Why worry about the IFE if the passengers were about to be aware there was something wrong but would shortly become incapacitated. So something here doesn't quite fit.
The other thing is the passenger phones. I know some hear are sick of discussions about phones. But after 2 months searching I don't think we are in a position to discount any possible information that could aid understanding. A low level flight across Malaysia would have generated calls from any able passengers. And also handset registration with the phone networks from any phones left (on even if all the passengers were disabled at this point). So that doesn't make sense either. Possibly a phone jammer. Even an accomplice in the cabin could not have ensured that all phones were put in flight mode and / or turned off.
The other thing that would concern me as the pilot would be the chance that one passenger (and it would only take one) might have a sat phone on board.
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The Inmarsat packets from the A/C contained an identifier code which has been compared to a MAC address. The identity of these packets as being from MH370 has been positivitly confirmed.
As for the radar: the Vietnamese state that they saw it turn around (circa 1:22) Thai radar picked up what could only be the same target approching Kota Bharu at 1:28 and the Malaysians picked up what can only be the same track shortly after that.
There is no doubt that this was MH370.
As for the radar: the Vietnamese state that they saw it turn around (circa 1:22) Thai radar picked up what could only be the same target approching Kota Bharu at 1:28 and the Malaysians picked up what can only be the same track shortly after that.
There is no doubt that this was MH370.
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Looking at the Inmarsat data, the variation in BFO between the contacts is such that I cannot see how a reliably accurate determination of BFO at each of the handshakes can be determined based only on the one value. Way back we heard about some sort of signal 'elevation' determination at the satellite ("40 degree arcs") - was that a false report or was it in fact simply referring to the BTO?
Do I understand that there is NO 'best fit' northerly route based on the BTO/BFOs?
Do I understand that there is NO 'best fit' northerly route based on the BTO/BFOs?
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I'll reply again using different wording
there mathematically must be a theoretical best for north, but validation tests against other flights indicated with great certainty it was south.
there mathematically must be a theoretical best for north, but validation tests against other flights indicated with great certainty it was south.
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The determination of the southern arc was made because of a doppler rate change that occurred when the satellite made a u-turn in the sky. The Inmarsat drifts north of and south of the equator in a 24 hour cycle. It forms a figure 8 against the sky. When it made one of those turns the doppler shift of MH370 changed in such a way as to determine which track it was on.
If the satellite was drifting south and MH370 was flying south, and then the satellite made a u-turn and headed north, it would be expected that MH-370 would be seen as moving away even faster.
Had MH370 been on the northern arc, it would have been seen to move more slowly away from the satellite when the satellite made the northern turn.
If the satellite was drifting south and MH370 was flying south, and then the satellite made a u-turn and headed north, it would be expected that MH-370 would be seen as moving away even faster.
Had MH370 been on the northern arc, it would have been seen to move more slowly away from the satellite when the satellite made the northern turn.
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I think this link has been put up before but it is relevant to the current discussion.
Considerations on defining the search area - MH370
Considerations on defining the search area - MH370
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one passenger (and it would only take one) might have a sat phone on board.
Thuraya and Immarsat satphones might reveal their position to within a few hundred nm via the spot beam used, but not Iridium which is probably the most popular network.
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If you read back a few dozen pages, you'll find that Inmarsat used the signals from a number of aircraft crossing the region to "calibrate" their model. More effective, and simpler because no need to borrow a 777 to do it.
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Inmarsat Satellite Position and Velocity
@BOAC at 1st Jun 2014, 23:54 :
I calculate that Inmarsat 3-F1 reached its furthest North latitude at about 19:33 UTC on 7 March.
This site has a table of satellite positions at the "ping" times, and shows the maximum North latitude at 19:41 :
Aqqa on MH370
The site also has large files of satellite position and velocity in Excel or CSV formats. I downloaded one of the Excel files, and previously computed very close to the same velocity (about -82 m/s, i.e., South, at the last "ping").
That would give a maximum Doppler of 400 Hz for an aircraft due North or South of the satellite, but less than 40 Hz at the presumed last position, since that position is almost orthogonal to the satellite groundtrack then.
Here's one explanation of how the satellite data could have been processed:
https://www.siam.org/news/news.php?id=2151
It links to this 31 MB set of slides:
http://www.utdallas.edu/~zweck/MH370_UNM.pdf
Slide 47 shows the ground track of the satellite. It's a teardrop shape rather than a figure 8, due to the very slight eccentricity of the orbit. It also links to the aqqa.org site, so all 3 of these sources are probably by the same person (John Zweck).
For any STK users, here's the AGI page on MH370:
AGI Blog
I calculate that Inmarsat 3-F1 reached its furthest North latitude at about 19:33 UTC on 7 March.
This site has a table of satellite positions at the "ping" times, and shows the maximum North latitude at 19:41 :
Aqqa on MH370
The site also has large files of satellite position and velocity in Excel or CSV formats. I downloaded one of the Excel files, and previously computed very close to the same velocity (about -82 m/s, i.e., South, at the last "ping").
That would give a maximum Doppler of 400 Hz for an aircraft due North or South of the satellite, but less than 40 Hz at the presumed last position, since that position is almost orthogonal to the satellite groundtrack then.
Here's one explanation of how the satellite data could have been processed:
https://www.siam.org/news/news.php?id=2151
It links to this 31 MB set of slides:
http://www.utdallas.edu/~zweck/MH370_UNM.pdf
Slide 47 shows the ground track of the satellite. It's a teardrop shape rather than a figure 8, due to the very slight eccentricity of the orbit. It also links to the aqqa.org site, so all 3 of these sources are probably by the same person (John Zweck).
For any STK users, here's the AGI page on MH370:
AGI Blog
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Slide 47 shows the ground track of the satellite. It's a teardrop shape rather than a figure 8, due to the very slight eccentricity of the orbit.
The 8 shape is visible from a "lateral" view (exchanging longitude coordinates for altitude ones).
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