Whay does "heavy" mean?

Discussion in 'General Discussion | Travel' started by Photonerd71, Jun 3, 2014.  |  Print Topic

  1. Photonerd71

    Photonerd71 Silver Member

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    Was listening to my ATC iPhone app earlier, ( I'm always amazed how the tower keeps everything in order and it is always fun listening to thr JFK folks get mad at some of the planes when they don't do as they are told), anyway I am curious when the say, for example, "united 123 heavy". Does anybody know what the "heavy" part means?

    Sent using a small piece of fruit.
     
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  2. HaveMilesWillTravel
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    HaveMilesWillTravel Gold Member

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  3. daninstl

    daninstl Gold Member

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    It's a term used to warn ATC about the size of the jetwash or potential turbulence caused by larger jets that have over a 300,000 pound takeoff weight. The ATC apparently adjusts for spacing behind such aircraft to avoid other planes being effected negatively by this. Plus it sounds cool and it gives Hollywood movies something to add like fake doctors or nurses on TV yelling "Stat" every 2 minutes.

    "Boston tower this is TWA flight 103 Heavy requesting immediate clearance on runway 3-2"
     
  4. Wandering Aramean
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    Wandering Aramean Gold Member

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    For a while some 757s were also considered "heavies" but they no longer are. Winglets helped reduce vortices to make the designation no longer necessary, though ATC will still give wake turbulence warnings for the type sometimes.

    http://www.faa.gov/documentLibrary/media/Notice/N7110.504.pdf

    Also, of random historic value:
     
    Last edited: Jun 4, 2014
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  5. Photonerd71

    Photonerd71 Silver Member

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    Thank you. I figured it was something like that. (Not the turbulence part but the wide body part.) Makes my guilty pleasure of listening to the ATC a little more interesting now. (I sometimes even get really nerdy and look up the flight numbers to see where the planes are going to and from......Yes my life is pretty boring sometimes)
     
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  6. jbcarioca
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    jbcarioca Gold Member

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    Here are the official designations as shown in Wikipedia:
    Preceding aircraftFollowing aircraftMinimum radar separation
    SuperSuper4 NM
    Heavy6 NM
    Medium7 NM
    Small8 NM
    HeavyHeavy4 NM
    Medium5 NM
    Small6 NM
    MediumSmall5 NM

    Boeing has had extensive campaigns to reduce wake turbulence designations by the ICAO, the body that does those things. Not only the B757 managed to get downgraded, but the B747-8, which was initially to be designated Super, managed to retain the Heavy designation of smaller B747 brethren. Rumor has it that if Airbus proceeds with A380 reengining they'll make aerodynamic changes to obtain ICAO approval to be downgraded to Heavy. regardless both of those giants still will require special airport preparations to accommodate their bulk. length (B747-8) and width (A380) being the biggest factors IIRC. Widebody per se is not why the designations happen, but turbulence (i.e. wake vortex) is. Upcoming smaller wide bodies might well avoid the designations as their aerodynamics improve and they generate less wake turbulence.
     
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