ATSIN 171

Mike Fawdrey · Post by **Mike Fawdrey** » Fri Dec 11, 2009 10:16 pm

I've just received email from CAA saying Mode A/C will be switched off at end of 2011. I thought we would be able to continue using mode A/C if already fitted or did I miss something. Perhaps CAA did not hear of the difficulties at Schipol

JohnMead · Post by **JohnMead** » Sat Dec 12, 2009 7:37 pm

Mike Fawdrey wrote:I've just received email from CAA saying Mode A/C will be switched off at end of 2011. I thought we would be able to continue using mode A/C if already fitted or did I miss something. Perhaps CAA did not hear of the difficulties at Schipol

I think that this was only intended for Mode S ground stations.

EDIT
Dis-regard, I've just re-read the ATSIN

Brian Hope · Post by **Brian Hope** » Sun Dec 13, 2009 8:00 am

I'm sure LAA will be taking this up with CAA on safety grounds. To effectively slash the number of aircraft transponding by probably well over 75% would be a pretty silly thing to do; it makes far more sense to allow Mode S to become the predominent system over a period of years due to new fitments and replacement of A/C sets as they become u/s.

steveneale · Post by **steveneale** » Sun Dec 13, 2009 10:19 am

I had a liittle investigate as this didn't make sense after everything CAA had promised. It appears that mode S ground stations still send out a "All Call interogation" now and again to see who is about. This is seen by A/C stuff normaly and it reponds just as before and the world goes on. So "classical Mode A/C transmissions" have to continue to meet the mode S specification.

I think this is just poor wording by CAA. I think what they meant to say was ground stations must be using mode S by that date.

There is a thread running on Flyer about this.

http://forums.flyer.co.uk/viewtopic.php?f=1&t=59961

Steve

Dave Hall · Post by **Dave Hall** » Sun Dec 13, 2009 4:56 pm

This was in the CAA circulation a week or so ago, and was indeed about Ground Stations switching off Mode A/C after Dec 31 2011. Obviously not much point requiring the aircraft traffic to switch to Mode S if the ground stations aren't talking the same language!

ATSIN no 171 is available from http://www.caa.co.uk/docs/33/ATSIN0171.pdf
but it doesn't really give any further interesting info that I could see - just a sort of "You were warned!".

John Brady · Post by **John Brady** » Sun Dec 13, 2009 8:10 pm

Having spoken to people at the CAA recently, I think this is a prompt to try to get ground stations to install Mode S interrogators or to purchase a Mode S feed from elsewhere. Given the current financial situation it is no surprise that airports are not rushing to spend money!

John

Light Aircraft Association

ATSIN 171

ATSIN 171

Re: ATSIN 171