Malaysian Airlines MH370 contact lost

[Vinnie Boombatz]

Geomagnetic South Pole

Thanks to A69 (*8052) and flt001 (*8068) for posting the link to the AAIB data.

A lot of posters have stated that the autopilot in TRK mode would follow a constant magnetic heading.

The geomagnetic South pole is now at about 80 S, 107.5 E.

Magnetic Poles

If the heading had been set to due South (magnetic), that would seem to give a track somewhere between the 400 KTAS and 450 KTAS curves on the last AAIB figure:

https://www.facebook.com/17856688885...614509/?type=1

MAGVAR is about zero over Kuala Lumpur, and increases to around 20 E at the last positions shown on the AAIB routes. For MH 180, that would favor the 450 KTAS line.

Historical Magnetic Declination | ngdc.noaa.gov

[mickjoebill]

Former chairman of NTSB speaks out

Live interview with former chairman of NTSB James Hall on Al Jazeera.
James Hall is chairman of Hall Associates.
Context was accident investigation

Summary
Strange that no confirmation of wreckage.
"If wreckage had been found, that information has to be made available to the families and then made available in a responsible manner via media to worldwide audience watching this disaster playout"

"Unfortunate that Malaysian govt is not competent to handle an investigation of this magnitude"

6 underwater investigations he dealt with took 6 weeks to get underwater vehicles to the known crash location, hard to put a time frame on this investigation as aircraft location is not yet known.

"In a normal investigation (by transportation bureaus such as in Australia and China) investigators not politicians handle investigation, then as information is identified it becomes public so it is a transparent investigation so the world knows that the facts being put forward are the correct facts."

"In this investigation facts come forward only to be corrected, its no wonder the families have lost confidence."
Ends

ABC Australia report families held a protest at Malaysian embassy in Beijing, demanding more information, they clashed with police.
Id be doing the same, there needs to be an explanation of how the authorities have determined that there are no survivors?

[500N]

"Unfortunate that Malaysian govt is not competent to handle an investigation of this magnitude"

"In this investigation facts come forward only to be corrected, its no wonder the families have lost confidence."

Glad someone calls a spade a spade !

[UnreliableSource]

Inmarsat

Though Inmarsat analysis undoubtedly have been key to home in on a crash site, the Doppler method might not tell the full story. A jitter assessment would have to be performed on ping return clock rather than on return data. Maybe the sat guys here know how much raw data, or data about the raw data, is logged?

Normal telecoms (digital side of the sat modem at the earth station) would not yield anything useful. It is possible the raw analogue RF was being digitised and captured for diagnostic purposes. I guess that their business model sees them handle very short messages. If a message isn't received, they won't get a real-time complaint, but a complaint many hours or days later. It would be a useful function to be able to go back and tell the customer that their signal wasn't relayed because it was off-freq/garbled/too-weak/overmodulated/oh-it-really-was-our-fault/whatever.

Sat earth stations have very precise frequency and time standards. Incoming RF would be downcoverted to an Intermediate Frequency (IF) that would be supplied to the sat modem for demodulation. If this IF was digitised by a SDR receiver tied to the station frequency standards, then reconstruction of the original analogue waveform arriving at the earth station would be possible.

The analysis of this waveform has been the rocket science here. I would struggle to separate doppler shift from other sources of frequency drift, especially with so little data to work with. There would have had to have been some serious maths at work, coupled with data from other aircraft and detailed historical information about the exact beam coverage patterns of their sat.

Another possibility is that deeper analysis found some too-weak-to-demodulate-so-not-initially-noticed signal on the "IF-tapes" for their POR bird. The IOR plus POR recordings would then give triangulation.

[BWV 988]

It is possible the raw analogue RF was being digitised and captured for diagnostic purposes.

Thanks for the thorough explanation US. Do you mean 24/7 sampling at 3+ GHz could be taking place in the sat? I understand the reasoning but doubt the practicalities.

[ghw78]

Driver Airframe in post 8101 queries the effect of altitude and speed on amount of fuel required to fly a set distance.

From Boeing Data for B777-200ER.
Long Range Cruise. Engines RR Trent 892
All up Weight at start of distance, 200.0 Tonnes
Time in hours and minutes, fuel burn in 1,000s kg

Distance Flight levels
(nm) 100 200 300 400
Fuel Time Fuel Time Fuel Time Fuel Time
600 11.5 1.50 9.1 1.37 7.5 1.28 6.6 1.22
1200 23.3 3.18 18.8 3.12 15.6 2.52 13.9 2.38
2000 38.5 6.08 31.2 3.21 26.4 4.45 23.5 4.19

[mickjoebill]

What happened to the ship that was just a few hours away from the wreckage sighted by RAAF ..turned back due weather?


ABC reporter Wed morning;
80km surface wind yesterday.
Seas eased and less rain today.
NZ Orion heading off first.
HMAS Success would be probably first ship to scene if something sighted by air.
Ocean Shield heading from Sydney today with "black box finder"

[grounded27]

China and Malaysia clearly want to just close this book, why are other nations investing so much $ in finding the Malay mess?

[Sir Richard]

ghw78

From Boeing Data for B777-200ER.
Long Range Cruise. Engines RR Trent 892
All up Weight at start of distance, 200.0 Tonnes
Time in hours and minutes, fuel burn in 1,000s kg

Distance -------------- Flight levels
(nm)_______100__________200___________300____________400
_________Fuel Time______Fuel Time_______Fuel Time________Fuel Time
_600_____11.5 1.50_______9.1 1.37________7.5 1.28_________6.6 1.22
1200_____23.3 3.18______18.8 3.12_______15.6 2.52________13.9 2.38
2000_____38.5 6.08______31.2 5.21_______26.4 4.45________23.5 4.19

Easier to read?

[auraflyer]

China and Malaysia clearly want to just close this book, why are other nations investing so much $ in finding the Malay mess?

1. Because there is a moral obligation to the victims and their families.

2. Because there is a practical (and economic) incentive: modern airliners should not just disappear. Knowing how one has will allow attempts to be made to avoid future repetitions.

[boguing]

Dillboy asked in 7743 "I'm wondering how long it will be before it is announced that the South China sea is to be revisited."



Not before somebody realises that the sat pings are a distraction.

What are the odds of the longest ever suicide/terrorist/unmanned autopilot flight also being solved by the first and novel use of technology that was never designed for the purpose?

[4Greens]

True and best comment on situation re search. Australian Commander 'We are not searching for a needle in a haystack. We are searching for the haystack'.

[sandos]

Originally Posted by BWV 988

Thanks for the thorough explanation US. Do you mean 24/7 sampling at 3+ GHz could be taking place in the sat? I understand the reasoning but doubt the practicalities.

I think he means on the ground-station. This would work if the satellite just very stupidly relays the signal in its raw form somehow and doesn't interpret/regenerate it before. I'm a bit hazy in this area, but I know its possible to do with wavelenghts in fibre so RF should be amenable to something similar. And yes, I would not be (very) surprised if the ground-station actually does some full sampling of the IF frequency, and maybe even saves it for later. Extremely valuable for finding faults etc.

If you didnt know there are SDR USB-dongles that can do ~3Mhz bandwidth full sampling costing ~10$. That a satellit ground-station is capable of something similar is not weird.

[Richard W]

When UnreliableSource said

It is possible the raw analogue RF was being digitised and captured for diagnostic purposes

he was clearly thinking of a recording at IF. The signal could well be reduced to a few key parameters, and even transmitting it raw would have take bandwidth numerically less than the IF.

[Lonewolf_50]

Originally Posted by boguing

What are the odds of the longest ever suicide/terrorist/unmanned autopilot flight also being solved by the first and novel use of technology that was never designed for the purpose?

"Necessity is the mother of invention."

Not sure if you bothered to read the piece on how INMARSAT applied their knowledge of their own systems to the science of radio waves and satellites to come up with estimates of the aircraft's position at various points in time.

Had other means been successful, they'd not have had to figure this out on the fly. As someone pointed out in that article, they " ... did about a year's worth of research less than two weeks."

That may be a slight overstatement, but it indicates how many man hours they applied to the problem to try and find a solution. During the first two days of the search, a lot of observers in the PPRuNe threads opined that they weren't finding any wreckage due to looking in the wrong place. That "wrong place" was the South China Sea.

Originally Posted by 4Green

Australian Commander 'We are not searching for a needle in a haystack. We are searching for the haystack'.

Indeed. The haystack (or the first bits of straw from the whole haystack) are apparently being blown about by wind and wave.

[Sober Lark]

Regarding the marker buoys dropped from fixed wing aircraft over debris in the SAR zone, can anyone advise how many days these devices are trackable for?

[daikilo]

If we assume Inmarsat could have digested more data from MH370, would it not be prudent for ICAO to recommend to its members to find means to ensure such data will be transmitted in any failure or deliberate disconnect scenario?

[RichManJoe]

Possible INMARSAT rf processing

I am not knowledgeable about the rf front end for the INMARSAT, but I am knowledgeable about AEHF and a few other communication satellites, and I would hypothesize they are similar. The comms between the satellite and the ground terminals (in this case, the aircraft terminal node controller (TNC)) use a form of PSK. All of the baseband and "IF" processing is done synchronously using digital processors, so there are digital to analog (D/A) converters prior to the upconverters and A/D's immediately following the downconverters. I don't know what the state of technology is today, but the converters may be sampling on the order of 400 MSPS to 1GSPS. For the receiver, the first digital process which is performed following the A/D is a fast fourier transform to channelize the data. This is then followed by a phase lock loop (PLL), which removes the doppler. By simply logging this phase correction used in the PLL (simply a number indicating radians per sample period) and sending it in the downlink to the INMARSAT earth station in Australia, INMARSAT would be able to reconstruct the doppler. This may be normal payload telemetry.

[Stefan Wolf]

Fox News Channel's Bill O'Reilly called this accident correctly one week prior to the Malaysian Prime Minister's official announcement yesterday. O'Reilly said the plane was at the bottom of the Indian Ocean. You might not like his political views, but he nailed it-- unlike countless armchair experts in our profession.

[costalpilot]

Good to know they found it stefan