I've taken some people flying recently for fun, and they noticed some hot-air balloons and asked me if they had transponders. In San Diego (Southern California) I often see hot air balloons well within the Mode C Veil (a 30 NM radius circle surrounding from a Class B airport). Do hot-air balloons need transponders when they are within the Mode C Veil?

  • 2
    $\begingroup$ I wondered if it would even be possible for a balloon to have a transponder. And they do in fact make portable transponders for balloons. $\endgroup$
    – JScarry
    Commented Apr 12, 2017 at 0:53
  • 1
    $\begingroup$ @JScarry I don't think so... 14 CFR 91.215 requires an installed system, and Part 43 outlines what is required for installation, maintenance and testing. That, alongside 14 CFR 91.131, says that the system must be installed to the pitot static system of a specific aircraft (makes sense for altitude encoding), it must be tested every 24 calendar months, and entries must be made in the aircraft maintenance record. I think the key phrase in 14 CFR 91.215 is engine-driven electrical system. $\endgroup$
    – Canuk
    Commented Apr 12, 2017 at 3:15
  • $\begingroup$ Keep in mind how a transponder works. Would the balloon even show on radar for the interrogator? Remember it takes both parts (the radar echo and the interrogator response) for a transponder to have any real meaning. $\endgroup$
    – coteyr
    Commented Apr 12, 2017 at 4:14
  • $\begingroup$ @coteyr: Couldn't SSR work without PSR echo? I think SSR angular accuracy is better than PSR. $\endgroup$
    – mins
    Commented Apr 12, 2017 at 6:36
  • 2
    $\begingroup$ @JScarry A few jobs back we built a transponder package for a hot-air balloon. The owner was planning some high altitude flights where he needed the capability. We packaged a GA transponder, altitude encoder, and a battery so the whole thing could be hung in the basket. The antenna (with a ground plane) hung over the side. It had it's own static system port. It was installed as a minor modification with a logbook entry and then the regulatory checks were performed and logged. They used a handheld radio to communicate with ATC. It worked just fine. $\endgroup$
    – Gerry
    Commented Apr 12, 2017 at 17:24

2 Answers 2


I've gotten this question enough times to look up the regulations and answer my own question :)

14 CFR 91.215 lays it out quite nicely. Particularly section B(3):

(3) Notwithstanding paragraph (b)(2) of this section, any aircraft which was not originally certificated with an engine-driven electrical system or which has not subsequently been certified with such a system installed, balloon or glider may conduct operations in the airspace within 30 nautical miles of an airport listed in appendix D, section 1 of this part provided such operations are conducted -

(i) Outside any Class A, Class B, or Class C airspace area; and

(ii) Below the altitude of the ceiling of a Class B or Class C airspace area designated for an airport or 10,000 feet MSL, whichever is lower; and

Where I see the balloons is definitely outside of the Class B airspace and below 10,000 feet MSL, so the answer is, no, they don't need a transponder.


When do I need to get a transponder?

Within the UK FIR, Mode S Enhanced (EHS) has been mandatory for all aircraft flying IFR as GAT within notified Mode S airspace since 31 Mar 05 (with a 2-year transition period until 31 March 2007), as per AIC 49/2005 (YLO 171).

The carriage of a Mode S Elementary (ELS) transponder within remaining UK airspace has been mandated by 31 Mar 2008. It is likely that there will be a 2-year transition period until 31 March 2010, to allow for any implementation difficulties.

Within other European Mode S implementing states, the target for Mode S (EHS and ELS) implementation is 31 March 2008, with no exemption period!

What is Eurocae ED115?

ED115 is the agreed technical standard for LAST Mode S transponders.

  • 5
    $\begingroup$ Quoting something that refers to the year 2010 as being in the future, with no further explanation, is not super useful. Especially when it doesn't seem to be applicable in the first place. $\endgroup$
    – hobbs
    Commented Apr 12, 2017 at 5:52
  • 2
    $\begingroup$ IFR??? In a balloon? WTF $\endgroup$ Commented Apr 12, 2017 at 8:06
  • $\begingroup$ @VladimirF - I suppose maybe. I mean you could use instruments to see height and wind direction. I suppose you could use them to see how far off course you are. You could tune to a VOR and use a CDI to see how screwed you are. I guess it would work. I"m not really sure how you would make a 1 min turn, or adjust headings, or why you would be in a balloon when you can't see anything but en.wikipedia.org/wiki/Breitling_Orbiter So maybe? $\endgroup$
    – coteyr
    Commented Apr 12, 2017 at 14:46
  • $\begingroup$ @coteyr I doubt that would work. Do you have any indication Breitling Orbiter was an IFR GAT flight? $\endgroup$ Commented Apr 12, 2017 at 15:21
  • $\begingroup$ no not at all, I'm just stating there are many kinds of hot air balloons and the really high altitude ones, or the ones that are designed for "rough" weather have to have some kind of "instruments". $\endgroup$
    – coteyr
    Commented Apr 12, 2017 at 17:26

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .