ATC(6)                                                     ATC(6)

     NAME
          atc - air traffic controller

     SYNOPSIS
          /usr/games/atc

     DESCRIPTION
          Atc presents air traffic on a cursor-controlled screen.  As
          the controller, you must shepherd it safely through the air
          space.  At the beginning of the game atc displays the
          takeoff/landing direction for each airport and prompts for
          the game duration with:

          < >  enter a number from 16 simulated minutes (hard) to 99
               (easier)

          Options are

          -u=file  take airspace description from file

          -a=name  use the named airspace; default is `Apple1'

          -s=seed  a number for seeding a 32-bit random number genera-
                   tor

          -t=time  preset the game duration

          -p=file  save the play of the game in the named file

          -m=file  play a `movie' of the saved game

     ATC(6)                                                     ATC(6)

          The initial display of a typical airspace looks like this:

               .0 . . . . . . 1 . . . . . . . . . . . . . .
               .. , . . . . . , . . . . . . . . . . . . . .
               .. . , . . . . , . . . . . . . . . . . . . 2
               .. . . , . . . , . . . . . . . . . . . . , .
               .. . . . , . . , . . . . . . . . . . . , . .
               .. . . . . , . , . . . . . . . . . . , . . .
               .. . . . . . , , . . . . . . . . . , . . . .
               6, , , , , , , * , , , , , , , , , , , , , 3
               .. . . . . . . , , . . . . . . , . . . . . .
               .. . . . . . . , . , . . . . , . . . . . . .
               .. . . . . . . , . . , . . % . . . . . . . .
               .. . . . . . . , . . . , , . . . . . . . . .
               .. . . . . . . , . . . , , . . . . . . . . .
               .. . . . . . . , . . , . . , . . . . . . . .
               .. . . . . . . , . , . . . . , . . . . . . .
               .. . . . . . . , , . . . . . . , . . . . . .
               4, , , , , , , * , , , , , # , , , , , , , 5
               .. . . . . . , , . . . . . . . . . , . . . .
               .. . . . . , . , . . . . . . . . . . , . . .
               .. . . . , . . , . . . . . . . . . . . , . .
               .. . . , . . . , . . . . . . . . . . . . , .
               .. . , . . . . , . . . . . . . . . . . . . 9
               .. 7 . . . . . 8 . . . . . . . . . . . . . .

          % and # denote airports, * and ! denote navigational aids
          (navaids), and commas denote airways that link entry/exit
          `fixes', airports, and navaids.  Dots are separated by one
          mile, horizontally, vertically, and diagonally.  An airplane
          appears as a letter followed by its height in thousands of
          feet.

          There are two kinds of planes: jets flying 1 mile per tick
          (15 seconds) and props flying 1/2 mile per tick.

          You must prevent various misfortunes.  Running out of fuel
          is serious.  So is a close encounter - less than 3 miles
          horizontal separation at a given altitude.  A plane changing
          altitude is considered to be at both its old and new alti-
          tudes.  A `boundary error', leaving the airspace at the
          wrong place, not on an airway, or at the wrong height, is
          also serious, but not as likely to be fatal.

          The right side of the screen shows flight plans.  A typical
          flight strip looks like:
                  Fj 7->3  4  NE     +
          The first letter is the aircraft ID, the next letter is `j'
          for jet or `p' for prop.  The next field gives the plane's
          intentions: this one is entering at (or is now at) fix 7 and
          leaving at fix 3.  The origin character tells where the
          plane is (or will be when it enters), the destination is a

     ATC(6)                                                     ATC(6)

          fix it wishes to go to.  (It will, however, continue on a
          straight path unless instructed otherwise.)  Next is the
          altitude, in this case 4000 feet.  The bearing is a compass
          direction: N, NE, E, etc.  The final character is the amount
          of fuel left, `+' for more than 10 minutes, otherwise the
          number of minutes of fuel remaining.  Jets begin with 15
          minutes of fuel, props 21.

          At the top of the flight plans are listed planes that will
          appear in the next minute, preceded by how many ticks (0-4)
          they are away.  Planes may be cleared for takeoff as soon as
          they are listed.

          Commands are terminated by <RETURN>.  <BACK SPACE> may be
          used to correct errors.  The following kinds of commands can
          be issued.

          $    End the game (game normally ends after 26 planes)
          W    Print flight plan for airplane W
          XA3  X will change altitude to 3000 feet
          QA0  Q will land (go to 0 feet altitude)
          HRE  H will turn right until it is heading east
          ALNW A will turn left until it is heading northwest
          CTS  C will turn south through the smallest angle
          T*7  T will take exit bearing for fix 7 at next navaid
          P*%  P will take landing bearing for % at next navaid
          DH   D will circle (hold) at next navaid
          MR0  Abort pending hold, clearance, or turn for plane M
          J?   Cancel delayed commands for J
          <SPACE>
               Speed up the game by advancing 15 seconds

          Climbing/descending. Planes climb or descend 1000 feet per
          mile.  Climbing from 0 is a takeoff; descending to 0 is a
          landing.  The takeoff/landing direction for each airport is
          given.  A landing airplane must reach altitude 0 headed in
          the right direction 1 mile before the runway.  No further
          commands may be given after a descent to 0, as control then
          rests with the tower.  If a plane lands from the wrong
          direction, it will climb to 1000 feet and issue a `go
          around' error.  While changing altitude, a flight strip
          reads like
                  Dp :->2  7v3  S     9
          which means at 7000 feet descending to 3000.

          Turning. Planes turn 45 degrees per mile.  Turns may be left
          (L) right (R) or to a specified direction (T).  Thus `ULNE'
          tells the pilot of plane U to turn to his left until he is
          heading northeast.  Changes of direction are indicated in
          the flight strip:
                  Nj :->5  5  S r W   +
          indicates that jet N is heading south, and will turn 90

     ATC(6)                                                     ATC(6)

          degrees to the right.  To cancel the remaining part of a
          turn, give the command (for plane N) `NR0'.

          Navaids. A plane may be directed to turn at a navaid or hold
          (circle) there, Thus command `AH' holds plane A at the next
          navaid.  The flight strip for a plane that is to hold looks
          like
                  Ap :->2  5  S *    7
          During the hold, the `*' will become `h'.  Every incoming
          plane that will be landing holds at a navaid unless the con-
          troller gives it other instructions.

          The command `*' clears a plane to turn sharply to any known
          fix at the next navaid.  The flight strip for a plane
          cleared through a navaid (to fix 5, for example) looks like:
               Hj .->2  5  S *5    +
          A holding aircraft given a clearance will continue around to
          the navaid, then immediately assume the specified bearing.
          Turns cancel clearances.

          Delayed commands. Commands of the form
               @<location>,<command>[,<command> ...]
          stack up activities.  A location may be any fix or a point
          offset from a fix, e.g.
               @#sw3s2,ARE
          which means at the point which can be reached by going three
          miles SW from airport #, then two miles S, plane A should
          begin a right turn until heading E.  The information command
          shows all delayed commands pending for that plane.  Note
          that delayed commands allow one to specify actions more than
          one navaid ahead.