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4 Answers

Key mike 4 times

Asked by: 851 views General Aviation

I'm flying to Myrtle Beach tomorrow. The AFD says to key mike 4 times to activate clearance delivery. Can someone tell me what this means and how it works? Does it activate a remote connection to another facility???

4 Answers



  1. John D. Collins on Jan 27, 2013

    My guess is that it is a remote clearance delivery using a land line (telephone). Keying the mike makes the phone call.

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  2. Bill Trussell on Jan 27, 2013

    Great guess John,

    The system is called Ground Communications Outlet (GCO). It utilizes the same sort of technology that is used for Pilot controlled Lighting but places a phone connection between the air ground radio and the controlling facility. When answered you let them know who you are and where you are and what you need, just like calling up on a regular clearance delivery frequency. The CD controller will pick up and read your clearance to you.

    The nice part is there is no need to lookup the number, depend on spotty cell coverage in a lot of places on airports, or wait to get your clearance airborne.

    Some of the systems are programmed to call flight service when you use 6 key clicks. Remember it is one second on and one second off to make it work.

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  3. Dan on Jan 27, 2013

    Thanks, when I got there, ATIS said to contact ground for clearance delivery anyway. Maybe because it was a Sunday.

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  4. Timothy Broadwater on Jan 27, 2013

    One other thing about GCOs the “clicks” need to be slow, second on – one second off. And if they put you on hold make sure you routinely transmit or it will disconnect the call.

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