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Locate crashed aircraft

  1. Sep 2, 2009 #1
    doesn't the aircraft leave its track through satellite?
    i mean why they are unable to locate aircraft lost in sea like airfrace flight 447

    if the whole track of an aircraft is known, wouldn't the exact position where it lost contact with the satellite be known then and no need of an ELT, would have been just an additional item.
  2. jcsd
  3. Sep 2, 2009 #2


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    No, it occasionally sends text messages home which also include it's position but not continuously.

    Even if it did send a message continuosuly you would know the last position when the system still worked - with the aircraft at 30-40,000 ft. A plane can move a long way falling from that height, then once it hits the water the debris can be spread over a large area as it falls another 10,000ft to the bottom of the ocean.
  4. Sep 2, 2009 #3
    Hi there,

    From what I know, the satellite lost connection to the aircraft, before the crash. Therefore, the aircraft continued a trajectory before hitting the water surface.

    The problem comes from the fact that the trajectory of the aircraft between the two moments is unknown. Did the pilot tried to manoeuvre to come back to its starting point??? Was the aircraft deviated from its original trajectory due to wind or other reasons??? There are many more parameters that might have happened before the crash. Therefore, leaving alot of uncertainties on the exact location.

  5. Sep 2, 2009 #4
    why would the satellite device fail in the air unless its an air collision as it would be sending signal irrespective of aircraft still working. It is understandable device failing on impact with water surface. So in that case it wouldn't be 30-40,000 ft, it would loose contact may be on impact with the water surface.
  6. Sep 2, 2009 #5
    and also couldn't the ELT instead of searching its signal , be able to communicate with the satellite
  7. Sep 2, 2009 #6


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    Note that they DID find the crash site so the existing tracking systems are perfectly adequate. The problem is locating the pieces of the debris that sank.
  8. Sep 2, 2009 #7
    i want to know does the ELT send signal to satellite, as far as i know the signal are only able to be traced by search and rescue having a receiver for that frequency and if yes why doesn't the ELT couldn't be designed to send signal to satellite
  9. Sep 2, 2009 #8


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    There are several things here that you might be confusing.

    ACARS is a data link between the aircraft and the airline's HQ - it sends simple text messages , these include the current position (from the aircraft's GPS) and are sent over a commercial communications satelite network (eg. orbcom).
    These messages are mostly to alert the airline of any delays and technical faults they aren't intended for crashes - They are powered from the aircraft so don't work once the aircraft has failed. These are the messages the news media mentioned in the recent Air France crash.

    The emergency location tranceiver (ELT) sends a signal to a special cluster of satelites used just for land and sea emergencies - it includes the location from it's own built in GPS and has built in batteries. It is triggered on impact or manually in an emergency. In practice many of these don't survive the impact of a crash.

    Neither of these systems work when the wreckage is under 3000m of water. So on the black box is a speaker which sends out pings that a microphone on a boat or submarine can use to zero in it's location. This is a bit hit or miss because the wreckage has no way of knowing it's location so can't send a message to anyone.
    Last edited: Sep 2, 2009
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