The web site suggest that aircraft entering combat will switch off the transponder. If they did that the IFF would not work with risk of attack from friendly forces. They may well switch off the Mode S.
Hi, I´d like to recycle this thread for some questions I didn´t manage to answer for myself by looking through the internets. If somebody has some ideas, would be great to read from you. I can see mil aircraft (fighter jets) in readsb and dump1090 flying in Mode A/C. Sometimes I get the impression that there are more jets in the sky above my location than are visible in MODE A/C or MODE S MLAT. When they take off and land they will briefly switch into MODE S and be visible on the map, which is kind of an indicator as to how many are really in the air. Some will fly training patterns with intermittent MODE S on, most will disappear from MODE S MLAT briefly after take off. Some will show up very briefly in MODE S while doing some training rounds. It doesn´t seem to depend on altitude and MLAT coverage. Has anybody here ever heard of an explanation for this erratic MODE S transponder on&off? They seem to do it in all altitudes, doesn´t seem to correspond to whether other aircraft are close by or not. You can see low lever flights here, zipping past light planes in close proximity, that do not show as MODE S. There is the occasional jet that flies with active MODE S all the way. Mil service planes, like tankers, target planes are always MODE S on in these training missions. Why would they do this if they want to disguise their training patterns? The lead aircraft of a pack of fighter jets that take off together sometimes remains in MODE S for a long time, while the rest never shows up in MODE S. In historical data research you can only guess what the rest of the pack did, based on the rudimentary flight paths of the lead plane. On refueling missions, only one aircraft of a pack shows up, the rest stays MODE S off but seems to be visible in MODE A/C, in many cases. NATO has apparently adopted MODE 5 as a required standard as of mid 2020. That would correspond to roughly the time when most mil aircraft (fighter jets) went silent while on training missions above Germany (and probably elsewhere in Europe?). Before, there was plenty mil traffic visible in MODE S, though with a declining tendency for the last few years. Does anybody know: Are NATO fighter jets, supposedly and in general, in Germany or elsewhere, in MODE 5 when in training missions? Or would they rather just turn off MODE A/C/S completely? Given that MODE 5 seems integrated with civil ATC (as far as I understand), I would think that these fighter jets must be also in MODE 5 then in a dense air space like Europe. But maybe not. In that case they would be showing as MODE A/C and MODE 5 to ATC? Probably not, right? Is there a security issue for civil airliners or light planes when mil aircraft are in MODE 5 only? I am thinking of ACAS and the likes. Would these systems be able to detect nearby MODE 5 aircraft? My guess is that especially light aircraft will not be equipped with systems that can detect MODE 5 in the vicinity. Is this the reason why mil planes are in some instances or at some locations still in MODE S?
@dudbaker Mode 4 and 5 are ENCRYPTED and only authorized receivers can detect Mode 5. as far as US FAA FAR/AIM Rules go, if an aircraft is in Mode 5, the FAA and the DoD have unrestricted access to Mode 5. The other federal offices, NSA, CIA, FBI, DHS, FIS, NTSB etc etc, can request the Mode 5 data if an incident occurs. so just because you as a civilian cannot see them, does not mean the proper people and systems can still see them @freqhopping The reasons the new rules went into play is because of ease of access and security concerns of people tracking military assets against a countries wishes. in the US, even certain law enforcement aircraft have now been authorized to use Mode 5 as well when dealing with sensitive ops pertaining to drug interdiction and gangs below the federal level. technology is proving relentlessly to be a double edged sword for both sides. I live in an area of Georgia, United States, that UH-60's fly over me nearly every 3 months transferring Army recruits who have qualified to become Rangers are en-route to the Ranger School which is about 2 hours NE of me. because of the nature of Rangers, they fly in Mode 5 the entire time. i physically see the Blackhawks, but they are never on ADSB for me or my receiver. this also applies to anyone of the SOCOM forces in the US. SEAL's, Rangers, Green Berets, RECON and Delta. interestingly enough, once those Ranger recruits are dropped off, after leaving the area and flying around, every time, the Blackhawks switch back to Mode C because now they are just command crew and no rules in play for when and where the recruits got dropped off.
