Malaysian Airlines MH370 contact lost
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Have I missed it somewhere? How do they Know :
A. The radar tracks WERE 370 without IFF
B. The origin of the "waypoints"
Does MAS subscribe to ADS-C?
Please do not de-bunk unless you KNOW and can give the evidence!
A. The radar tracks WERE 370 without IFF
B. The origin of the "waypoints"
Does MAS subscribe to ADS-C?
Please do not de-bunk unless you KNOW and can give the evidence!
Additionally, you will have significantly different Inmarsat distance data if the plane did a 180 and tried to return along its original heading as opposed to making a left turn to cross over the peninsula along the Malaysian/Thai border as described by the authorities.
I believe they have a very high degree of confidence that the plane they saw was MH370.
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ELT
Does the 777 even carry an airframe ELT (the life rafts/slides have them but they are not automatic unless the slide is deployed)?
are you getting confused with the FDR sonar locating beacon (SLB)?
are you getting confused with the FDR sonar locating beacon (SLB)?
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Could it be that MH370, with the flight crew incapacitated, the passengers dying, flew an erratic track because the ADIRU was damaged and intermittently commanded turns which ultimately resulted in this aircraft flying south until it crashed in the sea due to fuel exhaustion?
If I smash up a computer, what do you think the odds are that it'll (a) stop working / fail in many respects vs. (b) start doing something specific like sending an email every hour. I'm pretty sure you'd chose (a)....
Likewise having the flight systems damaged such that they change heading periodically but otherwise function perfectly, seems almost impossible.
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Buttrick, air defence radars since their conception have been able to assess height. In very simple terms, there is a radar sweep in the vertical plane as well as the horizontal.
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I haven't seen anyone post the other gem from today's press conference when a reporter asked if the SAR aircraft were being air refuelled, where that was technically possible, and had they asked the USA to provide tankers to do the honours. The reply was "no we haven't but I will now, now that you've asked!"
An Australian poster here made the point very clearly, days ago on PPRune, that the RAAF assets could air refuel so they weren't limited to just 2 hours on station in the Southern Indian Ocean. Sad then that they haven't done it.
An Australian poster here made the point very clearly, days ago on PPRune, that the RAAF assets could air refuel so they weren't limited to just 2 hours on station in the Southern Indian Ocean. Sad then that they haven't done it.
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Timing between satellite and transceiver
Some insight can be gained here:
Timing advance - Wikipedia, the free encyclopedia
GSM and Inmarsat C both use time division multiplex technique, the principle is the same.
Think of many a/c (transmissions) wanting to land at the same destination airport (satellite) with all a/c coming from different origination airports (airborne transceivers)
- Each a/c (transmission) has a time slot assigned when it's supposed to arrive.
- For obvious reasons those time slots may not overlap.
- Radio waves behave different than a/c : they can not fly holding patterns.
- So take off time of the radio transmissions (a/c) have to be timed, such that all transmissions (a/c) arrive at the satellite (destination airport) in their assigned time slots.
- ATC at destination (the satellite) has to measure the distance between origin and destination, so it can tell ATC at origin (airborn transceiver) when the a/c (transmission) has to take off.
- This distance measuring happens by measuring round trip times.
Timing advance - Wikipedia, the free encyclopedia
GSM and Inmarsat C both use time division multiplex technique, the principle is the same.
Think of many a/c (transmissions) wanting to land at the same destination airport (satellite) with all a/c coming from different origination airports (airborne transceivers)
- Each a/c (transmission) has a time slot assigned when it's supposed to arrive.
- For obvious reasons those time slots may not overlap.
- Radio waves behave different than a/c : they can not fly holding patterns.
- So take off time of the radio transmissions (a/c) have to be timed, such that all transmissions (a/c) arrive at the satellite (destination airport) in their assigned time slots.
- ATC at destination (the satellite) has to measure the distance between origin and destination, so it can tell ATC at origin (airborn transceiver) when the a/c (transmission) has to take off.
- This distance measuring happens by measuring round trip times.
Little off topic but let us not get carried away with the capabilities of HMS Echo....
I spent 3 years on board and her sister ship as a civilian contractor providing support for the survey equipment and teaching Navy operators how to use it - (yes as a civilian - really!).
The vessel is fitted with survey equipment for up to 1000m depth. It is great at finding wrecks. A sidescan sonar can only see a 200m wide swathe and you can only survey at 4.5knots. Her hull mounted multibeam will see a much larger swathe, but it is not designed for detecting objects - just changes in seabed. The 'hit' rate per metre squared is too low.
While Echo is a valuable asset, but it is not magic and is limited by the equipment. What may be of more use is her ability to act as a command platform.
I now work as a Survey Party Chief running geophysical surveys (as well as a flight instructor) - so I do know this industry as well as flight instruction.
I spent 3 years on board and her sister ship as a civilian contractor providing support for the survey equipment and teaching Navy operators how to use it - (yes as a civilian - really!).
The vessel is fitted with survey equipment for up to 1000m depth. It is great at finding wrecks. A sidescan sonar can only see a 200m wide swathe and you can only survey at 4.5knots. Her hull mounted multibeam will see a much larger swathe, but it is not designed for detecting objects - just changes in seabed. The 'hit' rate per metre squared is too low.
While Echo is a valuable asset, but it is not magic and is limited by the equipment. What may be of more use is her ability to act as a command platform.
I now work as a Survey Party Chief running geophysical surveys (as well as a flight instructor) - so I do know this industry as well as flight instruction.
On a side note, I find it rather tedious now watching the day after day updates (or non updates) in the press conferences. It is doing nothing more than fueling speculation and adding to the tension of the families. I know they want answers, but if there isn't any, then there isn't any.
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Navigator wanted
Pontius Navigator. Thanks for the excellent explanation, I did not consider the ground speed changing the track. You did remind me to consult my 1975 Ground studies for pilots, and perhaps navigators used to 50s and 60s radio and star navigation could solve the problem.
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and another poster (either RAAF or AMSA) stated categorically they can't only the americam P8 has that ability
Thanks for clearing that up, I knew about the Poseidon capability and saw the first post about AMSA Orions, I missed the second
For example, most P-3's don't have inflight refueling capability, the P-3F's sold to Iran do (or did, its been a long time since they were delivered).
Last edited by Airbubba; 21st Mar 2014 at 21:32.
I don't own this space under my name. I should have leased it while I still could
Pontius Navigator. Thanks for the excellent explanation, I did not consider the ground speed changing the track. You did remind me to consult my 1975 Ground studies for pilots, and perhaps navigators used to 50s and 60s radio and star navigation could solve the problem.
vector by applying wind to assumed airspeed.
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Aerials
Rather than some catastrophic loss of transmitting devices (VHF/HF radios, transponder/ADS-B, ACARS etc, is there any event that could cause all the relevant aerials to become inop, for eg does their wiring converge on some point, but would still enable the aircraft to be flown (albeit erratically) by a hypoxia affected pilot ? #clutchingatstraws
Last edited by Golf-Mike-Mike; 21st Mar 2014 at 22:20.
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sorry if this had been answered here before before . . . . . . the alleged nine witnesses on the Maldives . . . .. . .. have they been interviewed?. . .. .has any official credence come out about these 'sightings'?
Malaysian woman 'saw missing MH370 in water near Andaman Islands' | Mail Online
The Andaman Island question:
Trying to figure out why the Malaysian lady and her "sighting" from an aircraft (up high) near the Andaman Islands, as reported in a link further up, is being discounted. (There may be a lot of good reasons to do so).
Is the estimated position of her reported sighting too far from the north arc?
Her reported time of seing something is six to seven hours form the last "ping" that the Inmarsat folks have reported as registering on their satellite.
If the assumptions of last speed, or last altitude, or both are wrong ... is the locale where she thinks she saw it close enough to that arc/estimation to be worthy of investigating?
I am looking at maps, thinking about times, and that if the aircraft descended, and/or slowed down, for some reason, the furthest on circle shrinks a bit, and the fuel would run out sooner.
Trying to figure out why the Malaysian lady and her "sighting" from an aircraft (up high) near the Andaman Islands, as reported in a link further up, is being discounted. (There may be a lot of good reasons to do so).
Is the estimated position of her reported sighting too far from the north arc?
Her reported time of seing something is six to seven hours form the last "ping" that the Inmarsat folks have reported as registering on their satellite.
If the assumptions of last speed, or last altitude, or both are wrong ... is the locale where she thinks she saw it close enough to that arc/estimation to be worthy of investigating?
I am looking at maps, thinking about times, and that if the aircraft descended, and/or slowed down, for some reason, the furthest on circle shrinks a bit, and the fuel would run out sooner.
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Some (Inconclusive) INMARSAT Info
A few definitions:
In the following the aircraft can be referred to as the UT (user terminal) or the AES (Aircraft Earth Station).
In the FCC documents, "downlink" is from the satellite, "uplink" is to the satellite. Don't guarantee that other documents follow that, have seen the terms reversed elsewhere, so one needs to skim any given document to get the sense of how those terms are used.
A few caveats:
The satellite antennas are not angle sensing, per se (e.g., no 4-horn feed or whatever). Spot beams and regional beams would have nominal angles relative to a satellite-fixed frame that would be known to the satellite operator. The documents linked do not contain a detailed frequency plan, but it seems reasonable that any pair of adjacent beams would employ some frequency separation.
A 4 MB "INMARSAT 101" briefing from 2009:
http://www.satcomdirect.com/connect/...rsat%20101.pdf
Slides 32-33 show coverage for IOR and POR. Slide 17 says that Generation 3 satellites have 7 spot beams, so the numbers in the plots on Slides 32-33 appear to be the spot beams.
Slide 33 is actually moot, since the current POR satellite is Generation 4, located nearly 40 degrees further West in longitude:
LIVE REAL TIME SATELLITE TRACKING AND PREDICTIONS: INMARSAT 4-F1
MH370 should have been closer to the POR satellite at takeoff, and possibly within its field of view throughout much of its flight.
Haven't seen any "credible" statements of which INMARSAT satellite was providing the "ping" data. It could make a big difference, since the Generation 4 satellites (e.g., POR) have many more spot beams, which could help in the aircraft location.
FCC document that describes INMARSAT Block 3 communications (the Indian Ocean Region satellite is a Block 3):
https://licensing.fcc.gov/myibfs/dow...nt_key=-136047
FCC document that describes INMARSAT Block 4 communications (the Pacific Ocean Region satellite is a Block 4):
https://licensing.fcc.gov/myibfs/dow...ent_key=-94644
"The Inmarsat 4F2 satellite, licensed in the United Kingdom, will provide Mobile-Satellite Services to small User Terminals (“UTs”) . . .
The BGAN UT’s start by searching for the global beam signaling carrier. When acquired, the global beam holds information on any underlying regional beam channel the UT can use for registering on the network. No return communication is carried out in the global beam. The selection of regional beam channel is based upon UT GPS position and spot-beam maps or carrier C/No scanning. Once the correct regional beam has been acquired, the UT will attempt to register using either slotted aloha random access or un-slotted (in case the UT does not have its GPS position available) aloha random access on dedicated logical channels.
After registration the UT is handed over to a spot beam whenever a communications session is started. After the communications session has ended the UT is moved back to the regional beam to preserve resources in the spot beams."
"Regional Beam Signaling:
In the regional beam, two 50 kHz signaling carrier types are used for the BGAN. The modulation
is either 16QAM or QPSK.
The Return direction is used for the UT’s to register onto the network. Depending on the UT Class (1, 2 or 3), the UT will register using any combination of burst characteristics that closes the link. The return signaling carriers are either 25 kHz or 50 kHz and the modulation can either be QPSK or 16QAM."
It's not all that relevant, but if anyone gets hung up on the aloha protocol:
ALOHAnet - Wikipedia, the free encyclopedia
A draft RTCA spec with some system description for the latest version of ACARS (SBB, the broadband service with lots of spot beams):
http://www.icao.int/safety/acp/ACPWG...20Material.pdf
On pg. 35, it mentions "performing link tests (keep alives)". Using those keywords in web searches doesn't seem to turn up much more than using "pings".
The document also mentions an "ICAO 24-bit aircraft address". That allows over 4 million unique addresses, though the bits may be allocated less efficiently (e.g., using BCD). Whatever, that identifier is likely part of the aircraft response to a "ping", hence uniquely identifying MH370.
In the following the aircraft can be referred to as the UT (user terminal) or the AES (Aircraft Earth Station).
In the FCC documents, "downlink" is from the satellite, "uplink" is to the satellite. Don't guarantee that other documents follow that, have seen the terms reversed elsewhere, so one needs to skim any given document to get the sense of how those terms are used.
A few caveats:
The satellite antennas are not angle sensing, per se (e.g., no 4-horn feed or whatever). Spot beams and regional beams would have nominal angles relative to a satellite-fixed frame that would be known to the satellite operator. The documents linked do not contain a detailed frequency plan, but it seems reasonable that any pair of adjacent beams would employ some frequency separation.
A 4 MB "INMARSAT 101" briefing from 2009:
http://www.satcomdirect.com/connect/...rsat%20101.pdf
Slides 32-33 show coverage for IOR and POR. Slide 17 says that Generation 3 satellites have 7 spot beams, so the numbers in the plots on Slides 32-33 appear to be the spot beams.
Slide 33 is actually moot, since the current POR satellite is Generation 4, located nearly 40 degrees further West in longitude:
LIVE REAL TIME SATELLITE TRACKING AND PREDICTIONS: INMARSAT 4-F1
MH370 should have been closer to the POR satellite at takeoff, and possibly within its field of view throughout much of its flight.
Haven't seen any "credible" statements of which INMARSAT satellite was providing the "ping" data. It could make a big difference, since the Generation 4 satellites (e.g., POR) have many more spot beams, which could help in the aircraft location.
FCC document that describes INMARSAT Block 3 communications (the Indian Ocean Region satellite is a Block 3):
https://licensing.fcc.gov/myibfs/dow...nt_key=-136047
FCC document that describes INMARSAT Block 4 communications (the Pacific Ocean Region satellite is a Block 4):
https://licensing.fcc.gov/myibfs/dow...ent_key=-94644
"The Inmarsat 4F2 satellite, licensed in the United Kingdom, will provide Mobile-Satellite Services to small User Terminals (“UTs”) . . .
The BGAN UT’s start by searching for the global beam signaling carrier. When acquired, the global beam holds information on any underlying regional beam channel the UT can use for registering on the network. No return communication is carried out in the global beam. The selection of regional beam channel is based upon UT GPS position and spot-beam maps or carrier C/No scanning. Once the correct regional beam has been acquired, the UT will attempt to register using either slotted aloha random access or un-slotted (in case the UT does not have its GPS position available) aloha random access on dedicated logical channels.
After registration the UT is handed over to a spot beam whenever a communications session is started. After the communications session has ended the UT is moved back to the regional beam to preserve resources in the spot beams."
"Regional Beam Signaling:
In the regional beam, two 50 kHz signaling carrier types are used for the BGAN. The modulation
is either 16QAM or QPSK.
The Return direction is used for the UT’s to register onto the network. Depending on the UT Class (1, 2 or 3), the UT will register using any combination of burst characteristics that closes the link. The return signaling carriers are either 25 kHz or 50 kHz and the modulation can either be QPSK or 16QAM."
It's not all that relevant, but if anyone gets hung up on the aloha protocol:
ALOHAnet - Wikipedia, the free encyclopedia
A draft RTCA spec with some system description for the latest version of ACARS (SBB, the broadband service with lots of spot beams):
http://www.icao.int/safety/acp/ACPWG...20Material.pdf
On pg. 35, it mentions "performing link tests (keep alives)". Using those keywords in web searches doesn't seem to turn up much more than using "pings".
The document also mentions an "ICAO 24-bit aircraft address". That allows over 4 million unique addresses, though the bits may be allocated less efficiently (e.g., using BCD). Whatever, that identifier is likely part of the aircraft response to a "ping", hence uniquely identifying MH370.
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Sure they will: it is called a transponder, Mode 3/C.
"IFF" is a term used for transponder. Most mil transponders I worked with had modes I, II, III/C, and IV. The kit someone was painting your with would determine what part of the system responded to you.
Mode III/C interacted with standard air traffic control radar systems. A mil operator can refer to a standard civil transponder's response as an IFF (Mode III/C) reply to his interrogation. The advantage of this is that you only need one piece of kit to send out replies to interrogations via the antenna.
"IFF" is a term used for transponder. Most mil transponders I worked with had modes I, II, III/C, and IV. The kit someone was painting your with would determine what part of the system responded to you.
Mode III/C interacted with standard air traffic control radar systems. A mil operator can refer to a standard civil transponder's response as an IFF (Mode III/C) reply to his interrogation. The advantage of this is that you only need one piece of kit to send out replies to interrogations via the antenna.