Re: Air traffic control questions

From:         rem@world.std.com (Ross E Mitchell)
Organization: The World Public Access UNIX, Brookline, MA
Date:         22 Jun 94 16:57:50 
References:   1 2
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The squawk code is assigned on the ground, prior to taxi for IFR 
flights.  This code is kept throughout the flight.  The first 
departure controller will reference the transponder code indirectly by 
stating "radar contact" shortly after the plane takes off.  No further 
mention is made of radar status unless contact is lost, at which time the 
controller states "radar contact lost."  This tells the pilot that he or 
she must then make position reports until radar contact is re-established.
(Sometimes the pilot is given a new squawk code prior to arrival if the 
destination approach control uses a local numbering system to distinguish 
between aircraft proceeding to the various airports in the area.)

The controller hands-off an IFR flight to the next controller via landline 
BEFORE the pilot is instructed to call the next controller.  When the 
pilot calls, that controller is already waiting for the call.

For VFR flights, transponder codes are assigned and radar contact is 
established as the pilot transfers from one controller's area to 
another.  There is no controller hand-off.  Except in certain controlled 
areas, pilots flying under VFR are not required to be in contact with a 
controller at all, and controllers are not required to accept VFR 
traffic, except as their workload permits.  When not under the control 
(or guidance) of a controller, a VFR flight squawks code 1200.

Interestingly, if the pilot squawks the hijack code, the controller will 
ask the pilot to confirm that that code is being squawked without making any 
reference to what it means.  If the pilot confirms the hijack code by 
repeating its number, or does not respond to the controller's query, the 
controller assumes that a hijacking is in progress and proceeds accordingly. 

-- 
Regards,

Ross Mitchell  - rem@world.std.com - Phone: 617-965-7010  - Fax: 617-630-0140