AF 447 Search to resume
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Hi,
Here they are ......
Distress radiobeacon - Wikipedia, the free encyclopedia
ELT Requirements
EMERGENCY BEACONS
Balises de détresse aviation - ELT
Some food ....
So .. what happened with the "EPIRB thingy" of the AF447 ??
EPIRB thingy
Distress radiobeacon - Wikipedia, the free encyclopedia
ELT Requirements
EMERGENCY BEACONS
Balises de détresse aviation - ELT
Some food ....
Digital mode – 406 MHz beacons
406 MHz beacons transmit bursts of digital distress information to orbiting satellites, and may also contain a small integrated analog (121.5 MHz) homing beacon. Advanced 406 MHz beacons are capable of transmitting a highly-accurate GPS location within their distress message, thus, the process of distress relief is reduced from "search and rescue" to "get to and rescue". Getting to the location nonetheless may be very difficult.
The distress message transmitted by a 406 beacon contains the information such as:
which country the beacon originates from
a unique 15-digit hexadecimal beacon identification code (a "15-hex ID")
The encoded identification of the vessel or aircraft in distress, either as an MMSI value, or as, in the case of an ELT, either the aircraft's registration or its ICAO 24-bit address (from its Mode-S transponder)
When equipped, a GPS position
Whether or not the beacon contains a 121.5 MHz "homer"
The digital distress message generated by the beacon varies according to the above factors and is encoded in 30 hexadecimal characters. The unique 15-character digital identity (the 15-hex ID) is hard-coded in the firmware of the beacon.
[edit]406 MHz beacon facts
406 MHz beacons transmit for a quarter of a second immediately when turned on, and then transmit a digital burst once every 50 seconds thereafter. Both GEOSAR and LEOSAR satellites monitor these signals.
[edit]Hex codes
Example hex codes look like the following: 90127B92922BC022FF103504422535 [8]
A bit telling whether the message is short (15 hex digits) or long (30 hex digits) format.
A country code, which lets the worldwide COSPAS/SARSAT central authority identify the national authority responsible for the beacon.
Embedded 15-Hex ID or 15-hex transmitted distress message, for example, 2024F72524FFBFF The hex ID is printed or stamped on the outside of the beacon and is hard-coded into its firmware. The 15-hex ID can only be reprogrammed by certified distress radiobeacon technicians. The national authority uses this number to look up phone numbers and other contact information for the beacon. This is crucial to handle the large number of false alarms generated by beacons.
A location protocol number, and type of location protocol: EPIRB or MMSI, as well as all the data fields of that location protocol. If the beacon is equipped with GPS or GLONASS, a rough (rounded) latitude and longitude giving the beacon's current position. In some aircraft beacons, this data is taken from the aircraft's navigation system.
When a beacon is sold to another country, the purchaser is responsible to have the beacon reprogrammed with a new country code and to register it with his/her nation's beacon registry, and the seller is responsible to de-register the deprecated beacon ID with his/her national beacon registry.
One can use the beacon decoder web page[9] at Cospas-Sarsat to decrypt/extract the 15-hex ID from the 30-hex distress message.
406 MHz beacons transmit bursts of digital distress information to orbiting satellites, and may also contain a small integrated analog (121.5 MHz) homing beacon. Advanced 406 MHz beacons are capable of transmitting a highly-accurate GPS location within their distress message, thus, the process of distress relief is reduced from "search and rescue" to "get to and rescue". Getting to the location nonetheless may be very difficult.
The distress message transmitted by a 406 beacon contains the information such as:
which country the beacon originates from
a unique 15-digit hexadecimal beacon identification code (a "15-hex ID")
The encoded identification of the vessel or aircraft in distress, either as an MMSI value, or as, in the case of an ELT, either the aircraft's registration or its ICAO 24-bit address (from its Mode-S transponder)
When equipped, a GPS position
Whether or not the beacon contains a 121.5 MHz "homer"
The digital distress message generated by the beacon varies according to the above factors and is encoded in 30 hexadecimal characters. The unique 15-character digital identity (the 15-hex ID) is hard-coded in the firmware of the beacon.
[edit]406 MHz beacon facts
406 MHz beacons transmit for a quarter of a second immediately when turned on, and then transmit a digital burst once every 50 seconds thereafter. Both GEOSAR and LEOSAR satellites monitor these signals.
[edit]Hex codes
Example hex codes look like the following: 90127B92922BC022FF103504422535 [8]
A bit telling whether the message is short (15 hex digits) or long (30 hex digits) format.
A country code, which lets the worldwide COSPAS/SARSAT central authority identify the national authority responsible for the beacon.
Embedded 15-Hex ID or 15-hex transmitted distress message, for example, 2024F72524FFBFF The hex ID is printed or stamped on the outside of the beacon and is hard-coded into its firmware. The 15-hex ID can only be reprogrammed by certified distress radiobeacon technicians. The national authority uses this number to look up phone numbers and other contact information for the beacon. This is crucial to handle the large number of false alarms generated by beacons.
A location protocol number, and type of location protocol: EPIRB or MMSI, as well as all the data fields of that location protocol. If the beacon is equipped with GPS or GLONASS, a rough (rounded) latitude and longitude giving the beacon's current position. In some aircraft beacons, this data is taken from the aircraft's navigation system.
When a beacon is sold to another country, the purchaser is responsible to have the beacon reprogrammed with a new country code and to register it with his/her nation's beacon registry, and the seller is responsible to de-register the deprecated beacon ID with his/her national beacon registry.
One can use the beacon decoder web page[9] at Cospas-Sarsat to decrypt/extract the 15-hex ID from the 30-hex distress message.
Information transmitted by the beacon
A unique 15, 22, or 30 digit serial number called a Hex Code is transmitted
The Hex Code can contain a plethora of information, such as:[17]
the Country of beacon registration
the identification of the vessel or aircraft in distress, and
Identification for aircraft ELTs can be in the form of the aircraft's callsign or its ICAO 24-bit address (from its Mode-S transponder)
optionally, position data from onboard navigation equipment (GPS)
Potential to be seen by a satellite
To hear and process an analogue signal, both a LEOSAR and a LEOLUT must be within sight of each other continuously for a sufficient duration (several minutes). The LEOLUT does signal analysis via a dotplot of the signals heard, and the computer looks for a Doppler shift in the signal to triangulate a position.
Second detection is necessary due to false alerts and to resolve position—takes an additional 45–100 minutes before SAR assets can be called
GEOSAR provides nearly-instantaneous coverage 70 degrees north and south of the equator
Worldwide coverage via LEOSAR — 6 satellites
For 406 signals, LEOSARs do not have to be in sight of a LUT to relay a distress message to Cospas-Sarsat. Once a 406 signal is detected by a satellite, the satellite will "dump" this data towards Earth (thus to all LUTs) for 24 hours.
Future use of GNSS satellites will allow worldwide real-time coverage (MEOSAR)
Location detection Location detection
Two (roughly) "50% chance" mirror-positions (called the "A-side" for the most likely and the "B-side" for the least likely to be accurate) are generated by Doppler triangulation after the first pass of a LEOSAR
Due to false alerts, no reaction can occur based on first pass alert
A second pass resolves the ambiguity and resolves the search location to a radius of 20 km[18]
Moving targets (usually false alerts) produce interfering anomalies; calculated positions are inaccurate[citation needed]
LEOSAR uses same technique as for analog beacons, but, since beacons are uniquely identified as beacons and have improved frequency stability, response can occur based on first-pass information[18]
Doppler-only accuracy is within 5 km (3 mi) (3.1 statute miles or 2.6 nautical miles)— that is, the position is sufficiently accurate for SAR purposes even after only one pass. What's more, the "A-position" (the most likely of the two 'mirror' positions) can be determined valid with 98.5% accuracy after only one satellite pass.
A unique 15, 22, or 30 digit serial number called a Hex Code is transmitted
The Hex Code can contain a plethora of information, such as:[17]
the Country of beacon registration
the identification of the vessel or aircraft in distress, and
Identification for aircraft ELTs can be in the form of the aircraft's callsign or its ICAO 24-bit address (from its Mode-S transponder)
optionally, position data from onboard navigation equipment (GPS)
Potential to be seen by a satellite
To hear and process an analogue signal, both a LEOSAR and a LEOLUT must be within sight of each other continuously for a sufficient duration (several minutes). The LEOLUT does signal analysis via a dotplot of the signals heard, and the computer looks for a Doppler shift in the signal to triangulate a position.
Second detection is necessary due to false alerts and to resolve position—takes an additional 45–100 minutes before SAR assets can be called
GEOSAR provides nearly-instantaneous coverage 70 degrees north and south of the equator
Worldwide coverage via LEOSAR — 6 satellites
For 406 signals, LEOSARs do not have to be in sight of a LUT to relay a distress message to Cospas-Sarsat. Once a 406 signal is detected by a satellite, the satellite will "dump" this data towards Earth (thus to all LUTs) for 24 hours.
Future use of GNSS satellites will allow worldwide real-time coverage (MEOSAR)
Location detection Location detection
Two (roughly) "50% chance" mirror-positions (called the "A-side" for the most likely and the "B-side" for the least likely to be accurate) are generated by Doppler triangulation after the first pass of a LEOSAR
Due to false alerts, no reaction can occur based on first pass alert
A second pass resolves the ambiguity and resolves the search location to a radius of 20 km[18]
Moving targets (usually false alerts) produce interfering anomalies; calculated positions are inaccurate[citation needed]
LEOSAR uses same technique as for analog beacons, but, since beacons are uniquely identified as beacons and have improved frequency stability, response can occur based on first-pass information[18]
Doppler-only accuracy is within 5 km (3 mi) (3.1 statute miles or 2.6 nautical miles)— that is, the position is sufficiently accurate for SAR purposes even after only one pass. What's more, the "A-position" (the most likely of the two 'mirror' positions) can be determined valid with 98.5% accuracy after only one satellite pass.
GPS Position can be encoded into the Hex Code and can be updated real-time via GEOSAR
Encoded GPS position accuracy is about 15 m (45 ft), however, the space in the hex message protocol for position information is limited, so transmitted accuracy is approximately +/- 125 metres
Encoded GPS position accuracy is about 15 m (45 ft), however, the space in the hex message protocol for position information is limited, so transmitted accuracy is approximately +/- 125 metres
GEOSAR
The GEOSAR satellites are monitored by 16 GEOLUTs (Geostationary Earth Orbit Local User Terminals.) [5] The GEOSAR satellites provide continuous coverage of the entire earth below 70 degrees latitude with a view toward the equatorial sky. Some locations have poor radio reception toward the GEOSAR satellites and polar regions are not well covered.
SARP are installed on the following geostationary satellites: [6]
The GOES geostationary satellites GOES-East at 75° W and GOES-West at 135° W
The INSAT-3A geostationary satellite at 93.5° E
The Meteosat Second Generation (MSG) geostationary satellites MSG-1 at 9.5° E and MSG-2 fixed over the Prime Meridian
The GEOSAR satellites are monitored by 16 GEOLUTs (Geostationary Earth Orbit Local User Terminals.) [5] The GEOSAR satellites provide continuous coverage of the entire earth below 70 degrees latitude with a view toward the equatorial sky. Some locations have poor radio reception toward the GEOSAR satellites and polar regions are not well covered.
SARP are installed on the following geostationary satellites: [6]
The GOES geostationary satellites GOES-East at 75° W and GOES-West at 135° W
The INSAT-3A geostationary satellite at 93.5° E
The Meteosat Second Generation (MSG) geostationary satellites MSG-1 at 9.5° E and MSG-2 fixed over the Prime Meridian
Last edited by jcjeant; 22nd Jul 2010 at 05:19.
Very well said.
@mm43: thanks for the link back to your concise and very well reasoned summary of the issues. 
Originally Posted by jcjeant
AF447 Search ... that's the header and it's the point of this theatre..
The improvement must be on the device(s) who permit to detect where a plane (or the black boxes) are located after a crash .. and in particular when the crash occur in remote aera or at sea.
The actual black boxes record already enough parameters for understand the events at work in a crash.
Sending myriad of parameters by sattelite is not realistic or economically feasable.
The improvement must be on the device(s) who permit to detect where a plane (or the black boxes) are located after a crash .. and in particular when the crash occur in remote aera or at sea.
The actual black boxes record already enough parameters for understand the events at work in a crash.
Sending myriad of parameters by sattelite is not realistic or economically feasable.
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Another Solution based upon a very common and proven IT Technology
The other solution for inflight recorders data loss tinyurl.com/269cucb
.
This proposal suggests that "ships that pass in the night" merely exchange data via P2P handshake broadcast whilst enroute and within range of each other. This proposition is vaguely similar (or not dissimilar) to the common internet file-sharing techniques represented by Bittorrent, UTorrent, EMule etc. The idea is that the aircraft broadcasts the DFDR/CVR data on VHF/FM and that it should be picked up by any/all aircraft within radio range. Obviously when there is such an event as AF447, the "taped" (i.e. HardDisk recorded) data would be collected and amalgamated in the same cohesive manner as P2P files are. Error-checking and checksums normally ensure that files downloaded via P2P are intact in the collation. Stale Data would be overwritten at intervals so that unwanted data is deleted.
.
On another variant front, it may indeed be possible to burst transmit the same data via HF in addition. Alternatively the cost of using satellites to receive and retransmit data may be reduced by simply having a non-LEO constellation of two or three high orbiting satellites record daily data and simply over-write it as each flight transmits an "on-blocks" message indicating successful/safe flight completion. In the event of a crash the day's data would be retrieved for compilation of the missing aircraft's data.
.
The article addresses routes such as South America to NZ where there are very few aircraft plying the route. Suggestions vary from moored blimps to ground stations on enroute islands to ocean buoys receiving the transmissions made whilst in the oceanic gap.
.
Yet another variation could have aircraft only transmit data to a satellite when there is a loss of control (g switch) or a squawk of 7700/7500 is selected. With a little imagination, and utilizing available technology, there are rational and inexpensive solutions to prevent the loss of DFDR/CVR data due to overwater long-haul aircraft just disappearing enroute. When you think about it, the ex-military among us would be very aware of the very reliable Link 11/Link 4 capabilities we had introduced back in the mid 1970's. Technology has come a long way since then.
.
tinyurl.com/269cucb
.
This proposal suggests that "ships that pass in the night" merely exchange data via P2P handshake broadcast whilst enroute and within range of each other. This proposition is vaguely similar (or not dissimilar) to the common internet file-sharing techniques represented by Bittorrent, UTorrent, EMule etc. The idea is that the aircraft broadcasts the DFDR/CVR data on VHF/FM and that it should be picked up by any/all aircraft within radio range. Obviously when there is such an event as AF447, the "taped" (i.e. HardDisk recorded) data would be collected and amalgamated in the same cohesive manner as P2P files are. Error-checking and checksums normally ensure that files downloaded via P2P are intact in the collation. Stale Data would be overwritten at intervals so that unwanted data is deleted.
.
On another variant front, it may indeed be possible to burst transmit the same data via HF in addition. Alternatively the cost of using satellites to receive and retransmit data may be reduced by simply having a non-LEO constellation of two or three high orbiting satellites record daily data and simply over-write it as each flight transmits an "on-blocks" message indicating successful/safe flight completion. In the event of a crash the day's data would be retrieved for compilation of the missing aircraft's data.
.
The article addresses routes such as South America to NZ where there are very few aircraft plying the route. Suggestions vary from moored blimps to ground stations on enroute islands to ocean buoys receiving the transmissions made whilst in the oceanic gap.
.
Yet another variation could have aircraft only transmit data to a satellite when there is a loss of control (g switch) or a squawk of 7700/7500 is selected. With a little imagination, and utilizing available technology, there are rational and inexpensive solutions to prevent the loss of DFDR/CVR data due to overwater long-haul aircraft just disappearing enroute. When you think about it, the ex-military among us would be very aware of the very reliable Link 11/Link 4 capabilities we had introduced back in the mid 1970's. Technology has come a long way since then.
.
tinyurl.com/269cucb
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The discussion is engaging, but won't help find 447. So, I'll join in and suggest that information can be sent to satellite as a stream of hundreds of parameters that would moot the discovery of any boxes. Setting the transponder, or an automatic signalling when the Bus changes flight Law could break the dam and immerse a receiver with all pertinent trails. There is very near enough in ACARS to speculate within a narrow band.
Is there will in the industry? With all respect, AF and its cousins are not working their hands to the bone, and it would be a most naive partisan to say the will is powerful to locate. That 447 was out of touch is indicative of a "don't ask, don't send" attitude; Some sleeping dogs are encouraged to remain sleeping.
I am sending this message on a private system that sends enormous bags of data to a satellite, to another satellite, thence to Georgia, (US), then to Santa Clara, then back to me, in nanoseconds. Let's stop challenging windmills and ask some pertinent questions instead.
There is a system that can ionize air (airflow) intermittently, release it, to be captured, tagged, and computed as airspeed down the fuselage and sent to the Cockpit in the same micro seconds. Pitot smeet-o.
The Dark ages have never been beaten back whilst profit can be managed as a result of Risk/Benefit analysis.
bearfoil
Is there will in the industry? With all respect, AF and its cousins are not working their hands to the bone, and it would be a most naive partisan to say the will is powerful to locate. That 447 was out of touch is indicative of a "don't ask, don't send" attitude; Some sleeping dogs are encouraged to remain sleeping.
I am sending this message on a private system that sends enormous bags of data to a satellite, to another satellite, thence to Georgia, (US), then to Santa Clara, then back to me, in nanoseconds. Let's stop challenging windmills and ask some pertinent questions instead.
There is a system that can ionize air (airflow) intermittently, release it, to be captured, tagged, and computed as airspeed down the fuselage and sent to the Cockpit in the same micro seconds. Pitot smeet-o.
The Dark ages have never been beaten back whilst profit can be managed as a result of Risk/Benefit analysis.
bearfoil
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Oh dear... backs of envelopes have gone out of fashion, I see.
EM radiation in a vacuum: 300 000 km/sec =
300 km /msec =
300 m/µsec =
300 mm/nanosec =
30 cm = abt 1 foot.
Bearfoil, don't cheat. You did write nanosecond(s), implying tens or hundreds of nanoseconds at the most, not millions. In reality you're talking about something that takes at least milliseconds.
CJ
EM radiation in a vacuum: 300 000 km/sec =
300 km /msec =
300 m/µsec =
300 mm/nanosec =
30 cm = abt 1 foot.
Bearfoil, don't cheat. You did write nanosecond(s), implying tens or hundreds of nanoseconds at the most, not millions. In reality you're talking about something that takes at least milliseconds.
CJ
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Why satellites? As mentioned by others, they are expensive and low-bandwidth. The airliners already broadcast their location and speed to other planes around via ADS-B. Now improve the system slightly - have the airplanes record all received ADS-B messages. Once a plane goes missing, investigators can collect the recordings from planes that were nearby, and review the last ADS-B messages from the missing plane. This is both relatively cheap to implement and should pinpoint the last location with much better accuracy. The airplane should also have better chances at transmitting ADS-B broadcast than a directed signal to a satellite while under heavy turbulence or being upset.
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The Shadow wrote:-
The other solution for inflight recorders data loss tinyurl.com/269cucb
..... which included in part -
The Buenos Aries (EZE) to Auckland (AKL) route is one that comes to mind - 5,600NM, and for 5,000NM of the track, the chances of having reciprocal or same direction traffic in range is basically zip/zero, i.e. the sole westbound aircraft becomes the sole eastbound service on the return leg.
The other solution for inflight recorders data loss tinyurl.com/269cucb
..... which included in part -
The Buenos Aries (EZE) to Auckland (AKL) route is one that comes to mind - 5,600NM, and for 5,000NM of the track, the chances of having reciprocal or same direction traffic in range is basically zip/zero, i.e. the sole westbound aircraft becomes the sole eastbound service on the return leg.
Back to the discussion. The suggestions are all good, their chances of implementation in the next 10 years are not so good, and in this case we are not splitting hairs over the number of nanoseconds, 'cos there will be super tankers full of them before anything meaningful happens.
Lets go back to the BEA's suggestion that the ULB frequency be lowered to ~9kHz. The suggestion has already been aired at an ICAO meeting in Montreal, but the likelihood of it gaining traction will only come after the ULBs from AF447 have been located and determinations made as to why their pingers were not detected.
Changing the tried and proven is going to take time.
mm43
Last edited by mm43; 23rd Jul 2010 at 00:35. Reason: added link to post #203
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By referencing ULB, I'm assuming you mean underwater locator beacon. I think the US Navy decided many years ago that any frequency below about 500kHz belonged to them for LORAN and I don't think they've given them up (military brass are extremely reluctant to revisit the reasons for their rules - it could be embarrassing to the officer corps). Very low frequency acoustic signals travel long distances in seawater (which is why the USN snaffled them) but changing protocols for the non-revenue generating costs of FDR's and CVR's would not contribute to shareholder value for the airlines, to which their boards are legally required to adhere. The financial advisors that manage your retirement plan would be horrified to recommend that airlines spend money on safety efforts which are non-revenue generating investments which would decrease their fees (the ones they never told you about). It's unlikely that ultra low frequency beacons will appear in my lifetime.
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kilomikedelta wrote:-
It's unlikely that ultra low frequency beacons will appear in my lifetime.
It's unlikely that ultra low frequency beacons will appear in my lifetime.
Frequency Allocation Table
So even though the propagation in water of VLF electromagnetic energy is possible for limited distances, the propagation of acoustic Ultra Sound energy at similar frequencies is not covered, both in air and water. There is no real conflict, whether the US Navy thinks so or not.
mm43
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Wow, an FCC directive from July 15, 2010. Industry Canada usually takes a couple of years to get around to the lobbyists barf to make a decision. I'll have to check what Industry Canada has sucked up to the USN as far as frequency allocations. Our current government is good at sucking up to whatever the Americans want. We really don't need 65 F-22's.
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Frequency Chart
Canada has a similar chart at:
http://www.ic.gc.ca/eic/site/smt-gst.nsf/vwapj/spectallocation-08.pdf/$FILE/spectallocation-08.pdf
The Canadian chart is more colorful and seems to have been updated in 2008. Perhaps there is a later version.
The F-22 has been canceled. I think you mean the F-35.
http://www.ic.gc.ca/eic/site/smt-gst.nsf/vwapj/spectallocation-08.pdf/$FILE/spectallocation-08.pdf
The Canadian chart is more colorful and seems to have been updated in 2008. Perhaps there is a later version.
The F-22 has been canceled. I think you mean the F-35.
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There seems to be some confusion here......
An ELT is an Emergency Location Transmitter.
It's a small package, used both on ships and aircraft.
It floats, and transmits radio waves. The frequencies used are 121.5 MHz and/or 406 MHz.
Nothing to do with VLF or ELF.
A ULB is an Underwater Location Beacon.
Its is attached to an FDR or CVR, and remains attached when the FDR or CVR sinks.
It transmits sound waves (pings), so the remarks about radio spectrum allocation are irrelevant.
Currently the sound frequency of the pings is about 30 kHz, but it has been suggested to lower this to about 9 kHz, to improve the detection.
CJ
An ELT is an Emergency Location Transmitter.
It's a small package, used both on ships and aircraft.
It floats, and transmits radio waves. The frequencies used are 121.5 MHz and/or 406 MHz.
Nothing to do with VLF or ELF.
A ULB is an Underwater Location Beacon.
Its is attached to an FDR or CVR, and remains attached when the FDR or CVR sinks.
It transmits sound waves (pings), so the remarks about radio spectrum allocation are irrelevant.
Currently the sound frequency of the pings is about 30 kHz, but it has been suggested to lower this to about 9 kHz, to improve the detection.
CJ
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ADS-B squitter
keitaidenwa
ADS-B input into own airplane's TCAS system has in fact been developed, nothing new today. Many airplanes are already squittering out GPS based own ship position by their Mode S transponder. In stead of continuous recording by surrounding traffic, satelite based monitoring on 1090Mhz seems a logical alternate option. This would also contribute to manage airspace, yet not covered by SSR's
ADS-B input into own airplane's TCAS system has in fact been developed, nothing new today. Many airplanes are already squittering out GPS based own ship position by their Mode S transponder. In stead of continuous recording by surrounding traffic, satelite based monitoring on 1090Mhz seems a logical alternate option. This would also contribute to manage airspace, yet not covered by SSR's
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Hi,
So the question is:
What happened with the ELT(s) of the AF447 ?
An ELT is an Emergency Location Transmitter.
It's a small package, used both on ships and aircraft.
It floats, and transmits radio waves. The frequencies used are 121.5 MHz and/or 406 MHz.
Nothing to do with VLF or ELF.
It's a small package, used both on ships and aircraft.
It floats, and transmits radio waves. The frequencies used are 121.5 MHz and/or 406 MHz.
Nothing to do with VLF or ELF.
What happened with the ELT(s) of the AF447 ?
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jcjant, Christiaan --
The ELT(s) would be of the mounted type, and sink along with the ship no matter how much buoyancy capability the small ELT box has. And many of these have NO buoyancy at all.
You're perhaps confusing ELTs with PLBs and EPIRBs, some of which do float and are meant to be carried out of the aircraft and into the liferaft with the evacuating crew. Liferafts may have their own locator beacons as well. But if nobody had a chance to evacuate, no ELTs or PLBs will have made it to a point when they could have started to float and transmit. The regular ELTs would have transmitted after being triggered, as long as their antennas remain above water.
Also, they are guaranteed to transmit their signals only as long as their batteries permit, the unit remains upright with the antenna out of the water, etc.
The ELT(s) would be of the mounted type, and sink along with the ship no matter how much buoyancy capability the small ELT box has. And many of these have NO buoyancy at all.
You're perhaps confusing ELTs with PLBs and EPIRBs, some of which do float and are meant to be carried out of the aircraft and into the liferaft with the evacuating crew. Liferafts may have their own locator beacons as well. But if nobody had a chance to evacuate, no ELTs or PLBs will have made it to a point when they could have started to float and transmit. The regular ELTs would have transmitted after being triggered, as long as their antennas remain above water.
Also, they are guaranteed to transmit their signals only as long as their batteries permit, the unit remains upright with the antenna out of the water, etc.
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An ELT distress beacon with manual tripping was also recovered. This had not been actuated. Its switch was found in the “OFF” position.
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Automatic ELT
Gentlemen,
per JAR, an automatic ELT was mandatorily mounted on the aircraft.
It activates automatically on crash-like G-forces and sends a short message on 406 MHZ.
This message gets through COSPAS/SARSAT.
So...
What happened to it ?
per JAR, an automatic ELT was mandatorily mounted on the aircraft.
It activates automatically on crash-like G-forces and sends a short message on 406 MHZ.
This message gets through COSPAS/SARSAT.
So...
What happened to it ?
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ChristiaanJ wrote:-
There seems to be some confusion here......
There seems to be some confusion here......
As for AF447's ELTs, one was found unactivated, and no 121.5/406MHz transmissions were ever detected.
mm43