Do I still need Mode S with ADS-B

AaronG · #1 06-05-2014, 11:05 AM

I am upgrading to ADS-B, and would like to get rid of a box in place to display Mode S from the 330 to my Chelton screens. I'd like to get some feedback on the value of keeping Mode S now that I have ADS-B. I fly mostly in New England, with trips as far as Florida and Oshkosh. Are there coverage dead zones or other benefits to keeping the Mode S?

Aaron

Bavafa · #2 06-05-2014, 11:13 AM

I believe it only gives a level of redundancy for traffic but based on my experince, ADS-B has been so accurate that I do not need the mode S. Mine is being displayed on the 430 so there has been no issue keeping it or checking them against one another.

BobTurner · #3 06-05-2014, 04:15 PM

I do not understand what you are asking. There are two ways to go with ADSB-out. 1. Send the gps/altimeter info out on a mode S-ES transponder. In this case you do still have mode S. 2. Send the ADSB info out over a UAT device. In this case you must still have either a mode C or a mode S transponder. If you have an S now you could downgrade to a C with option two, but I don't think that's very cost effective.

Edit: did you mean traffic information service from the mode S, vs ADSB?

AaronG · #4 06-05-2014, 05:51 PM

Yes, I'm speaking about traffic. Is there any benefit to display the Mode S traffic, now that I get it through ADS-B?

flightlogic · #5 06-05-2014, 07:37 PM

Mode C will be legal. Check the press releases from Free Flight Systems in Waco TX. They clarify the requirements... and will admit mode C is fine with ADSB.
Mode S is pushed by the manufacturers... but is costly.
Sandia is cheaper and smaller....or Trig... etc.

Brantel · #6 06-05-2014, 08:16 PM

Quote:

Originally Posted by AaronG

Yes, I'm speaking about traffic. Is there any benefit to display the Mode S traffic, now that I get it through ADS-B?

If I am not mistaken, the confusion is in what you are calling it....

I think you are talking about TIS-A traffic received by a Mode S xponder.

I have mine turned off because TIS-A overrides TIS-B in a Garmin G3X system and I have found TIS-B to be superior to TIS-A.

zaitcev · #7 06-24-2014, 11:09 AM

There's a constant talk how an aircraft has to trigger broadcasts by ground stations, so having an TIS-B receiver is not enough. You need either UAT ADS-B OUT transciever or Mode S transponder. I still cannot figure how true that is, but that's what they say. Perhaps hearing that made the OP to ask the question.

greghughespdx · #8 06-24-2014, 11:21 AM

Quote:

Originally Posted by zaitcev

There's a constant talk how an aircraft has to trigger broadcasts by ground stations, so having an TIS-B receiver is not enough. You need either UAT ADS-B OUT transciever or Mode S transponder. I still cannot figure how true that is, but that's what they say. Perhaps hearing that made the OP to ask the question.

You need an ADS-B transmitter of one form or another to be compliant and for traffic to display properly and completely on your -in display device. Either a UAT transceiver device as described, or a Mode S transponder (1090-out) with "Extended Squitter" capability. Note that not all Mode-S transponders (in fact at this time only a relatively small portion of the installed base) will meet the ADS-B out requirement. The ES capability is an extension of the transponder's Mode S functionality.

Brantel · #9 06-24-2014, 11:22 AM

Quote:

Originally Posted by zaitcev

There's a constant talk how an aircraft has to trigger broadcasts by ground stations, so having an TIS-B receiver is not enough. You need either UAT ADS-B OUT transciever or Mode S transponder. I still cannot figure how true that is, but that's what they say. Perhaps hearing that made the OP to ask the question.

To take full advantage of TIS-B, you need to have ADS-B out either with a UAT or a Mode-S ES xponder and they need to be properly configured. At this time the FAA is allowing non certified VFR position sources to be used with these units to wake up the ground stations. Who knows how long this will last...

It is very true that you must have ADS-B out to "wake up" the ground stations. Occasionally if you are close enough to an aircraft that has ADS-B out, you may be able to receive TIS-B without having ADS-B out yourself but this will be unreliable at best.

BobTurner · #10 06-24-2014, 11:25 AM

Quote:

Originally Posted by zaitcev

There's a constant talk how an aircraft has to trigger broadcasts by ground stations, so having an TIS-B receiver is not enough. You need either UAT ADS-B OUT transciever or Mode S transponder. I still cannot figure how true that is, but that's what they say. Perhaps hearing that made the OP to ask the question.

To be assurred of having all the traffic ATC sees sent up to you (notice all the qualifiers) you need ADSB out (UAT or S-ES). That is true.
As to the OP, now that I understand it: here in northern CA I have always found TIS-A coverage spotty. TIS-B (ADSB) coverage seems much better.