Re: Mode C / Mode S Help !!!

Aviation General

Mode C / Mode S Help !!!

sandybeech 21/12/2009, 8:40 PM

Hi to everyone!!!

New to here passed my ppl end november at full sutton, and really pleased... Yeah yeah yeah yeah.... Ideal goal is to fly to Lands end to see my mum!! (better get saving!!)... ANY way can somone simplify MODE C / MODE S......

Let me have a go????? (or i should know?) Mode C= Just turn the transponder to the alt setting on the transponder???? But In one of the aircraft I fly at full sutton has NO ALT DATA.... ??

So therefore MODE S.... Does this give atc, tcas info????

Sorry if I should know the answer to this.... Many thanks....

Re: Mode C / Mode S Help !!!

A and C 22/12/2009, 9:35 AM

All the transponder you have fitted will do is give a Mode A radar return.

That is it will paint the selected code on a radar screen.

If you have an altitude encoder then it will paint your altitude on the radar screen as well.

From a TCAS pint of veiw your mode a signal is of limmited use as without alitude data it wont give a TCAS equiped aircraft the RA warning to enable it to avoid you.

It sounds like you are having some conffusion between modes A, C & S. I tink that a chat with your instructor would be a good idea.

Re: Mode C / Mode S Help !!!

Aviator|Chris 22/12/2009, 10:30 AM

Time to brush up and re-cap on Transponders!

Re: Mode C / Mode S Help !!!

Nicky 22/12/2009, 6:26 PM

Transponder on (without alt. selected) = in mode A which will only give the code you have selected

Transponder on (with alt. selected) = in mode C which will give the code you have selected and your altitude, although it gives your pressure altitude (your altitude with 1013 set).

Mode S is a new transponder technology allowing more data to be passed from your transponder to air traffic, while reducing transponder workload. It isn't mandatory to have mode S fitted at the minute but could be in the future. To be honest I don't profess to know the ins and outs of mode S, I only know what i've read and heard about it but it could be something that becomes more widely used in the future.....

There's also an ident setting on your transponder that when selected lights up your return on the radar screen so that the controller can identify you..

Hope that helps a bit :)

Nick

Re: Mode C / Mode S Help !!!

sandybeech 22/12/2009, 6:34 PM
Brill many thanks yes this does... Kind thanks...

Re: Mode C / Mode S Help !!!

PilotMo 12/01/2010, 9:15 PM
Mode S basically allows more information to be added to your aircaft.

Aircraft fitted with TCAS (Traffic Collision Avoidance System) will need mode S to be fitted to other aircraft for the TCAS to work out a resolution advisory to avoid conflict. If the aircraft only has a mode C transponder the TCAS will only give a traffic advisory which does not instruct the pilot what to do to avoid a collison.

Most light aircraft will have Mode C which as said before is just used to give your aircraft an altitude read out for the controllers. Mode A is the bare basics- showing the squark code to the controllers and nothing else.

Morbz

Re: Mode C / Mode S Help !!!

A and C 13/01/2010, 9:24 AM
Morbz I think that you might need to check the books TCAS will give an RA from Mode C. It is Mode A that will only give a TA.

Re: Mode C / Mode S Help !!!

PilotMo 15/01/2010, 10:28 AM
Thinking about it yes you are correct my mistake! (Getting rusty since my Instrument ATPL exam!).

The point that I have muddled up is that a mode S transponder is the bit that is needed to coordinate the resolution, the data from both aircraft is thrown about and a coordinated instruction is given to each plane, eg 1 will climb and 1 will descend. Mode C equipped aircraft with no mode S will still give resolution advisories but without the coordination, so the 2 alerts inside each flight deck could both instruct a climb or a descent, which if your unlucky could make things a bit worse!

Morbz