Disapearing Aircraft

Discussion in 'Off-Topic' started by Shagas, Dec 30, 2014.

  1. Shagas

    Thread Starter Active Member

    May 13, 2013
    Could someone explain to me how it is possible that something like a Boeing-777 just goes off radar?
    How can it just ... poof ... and dissapear? Aren't there independent trackers (position transmitters) with independent power sources that cannot be at all reprogrammed/switched on/off and meddled with from the cabin control?
  2. killivolt

    Active Member

    Jan 10, 2010
    My brother in-law works for Boeing; on a Black Box project. The box transmits data Pre-Mid-Post flight. If the plane was equipped with the newer version "Black Box" maybe something was picked up at that moment but all data seemed normal at that time.

    Or if it wasn't at the point of transmission.

    The incident is to reminiscent of the first one. Very odd indeed.

    My condolences go out for anyone related.


    Edit: I just learned; the morning news reports the plane is found in shallow waters. No one was wearing a life vest. It has now turned into a recovery mission; they report they will have good chances of obtaining the Black Boxes to learn what went wrong.

    I am saddened for the people in the air port waiting for news.

    Last edited: Dec 30, 2014
    Sinus23 and PackratKing like this.
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
    40yr pilot and plane owner here...

    I would say that less than 1% of the earth has radar coverage to near ground level. Probably less than 5% of the earth has coverage above 25,000 ft msl, where most commercial jet transports fly at cruise altitudes.

    Radar coverage is based on terrestrial radar sites. Radar interrogation of an aircraft transponder depends on line-of-sight. Because of earth curvature, depending on the elevation of the radar site, the radio horizon for its signals maybe only a few miles from the site; hence very little of the earth is covered to ground/sea level.

    The aircraft's transponder transmits with a crappy omni-directional antenna at a peak-pulse-power output level of ~400W at about 1.4GHz, so its range is limited to a few hundred miles, so even when the aircraft is flying high, there are huge coverage gaps. For example, on the flight from California to Hawaii, any aircraft is effectively out of radar coverage for most of that flight. Voice communication by VHF radio is also line-of-sight, so transoceanic flights use HF ssb communications, and just do periodic position reports when out of radar coverage.

    Sweep rates of long range radars are about 60 sec, so the position of an aircraft is updated at that rate on the display. In a mid-flight breakup, the pieces can fall below radar coverage between sweeps...

    Last edited: Dec 30, 2014
    Shagas, Brownout and shortbus like this.
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
    Appears to have been located early this morning.

    Also, are you aware of the phrase, "flying below the radar". So, no, little chance of tracking at low altitudes.
  5. alfacliff

    Well-Known Member

    Dec 13, 2013
    also, the beacons use weather satelites with their reicievers on them. there can be as much as 2 hours when no satellite is above the horizon to receive them.
    Shagas likes this.
  6. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    From the LEOSAR and GEOSAR satellites it looks like the area in question is covered. I'm wondering if the EPIRB ever deployed or even had their requisite tests.

    The LEOSAR runs perpendicular to the equator, in a 100 minute orbit. Low Earth Orbit Search And Rescue. GEOsynchronous Search And Rescue.
  7. Shagas

    Thread Starter Active Member

    May 13, 2013
    Thanks for the answers, especially from the people who have dealt with aircraft one way or another .
    I might have spoken very vaguely when I said "off radar" . I didn't mean the Radar per se, what I meant is being able to track the aircraft by whatever means.
    This comes to me as a surprise ... I thought that every such commercial aircraft would be outfitted with multiple independent "tracking systems" so that it could be tracked in case of hijacking
    or other unfortunate events.
  8. shteii01

    AAC Fanatic!

    Feb 19, 2010
    "Life is stranger than fiction."
  9. kyle7119


    Feb 11, 2011
    A lot of things can disappear in a really bad storm. All it takes is a few seconds in a nose dive for the aircraft to hit the water and rip itself into shreds.