nobbi wrote:
No SOP at all – must be the private whim of a 300h+ flight instructor … out of misunderstood system knowledge or to impress students and nobody dares to say it’s nonsense
No private whim. When I took my PPL in 1984, this recommendation was in every textbook.
If it is really and issue, why can’t design it with active sqwk and STBY sqwk capability like frequencies in COMs/NAVs ?
Vintage transponders required 20Ah to run, warm ups, stbys where a 4 digits number has to be manually set, none of this is relevant to slick small mode-s you are expected to buy today
I also don’t see the point of playing with GND/STBY/ALT, you just switch the thing on on the ground on STBY and enable/disable ALT while entering exiting the runway? or best just have it auto-ALT from airspeed/altimeter…unless there anyone who is really interested in surveillance/ident of ground traffic using secondary radars (??)
Personally, I hate when I get FlightAware/Flarm notidfications while on circuit/final due to traffic sitting on the ground, so I can’t imagine how much people complains about false TCAS instructions or busting airspace that you are already in 
Ibra wrote:
I also don’t see the point of playing with GND/STBY/ALT, you just switch the thing on on the ground on STBY and enable/disable ALT while entering exiting the runway? or best just have it auto-ALT from airspeed/altimeter…unless there anyone who is really interested in surveillance/ident of ground traffic using secondary radars (??)
Like ground control at most major airports?
Having a GND mode means life is easy for the pilot and you can’t forget to turn the transponder on. It also indicates correctly to TCAS aircraft that you are on the ground.
There is no downside. Why not use it if you have it?
And for TCAS equipped aircraft the only real problem is aircraft not squawking altitude.
Ibra wrote:
Personally, I hate when I get FlightAware/Flarm notidfications while on circuit/final due to traffic sitting on the ground
You shouldn’t get any warnings when the transponder is in GND mode. That’s the point!
JasonC wrote:
Like ground control at most major airports?…..There is no downside. Why not use it if you have it?
Got it, so mainly a limitation of Flarm/FlightAware not being able to filter out ground traffic (unlike TCAS as you mentioned)
In big airports, GND ATC already have movement sensors detectors/magnetic sensors (like GATS) or surface radar grids (ASDE-X in USA) to use for ground surveillance but I am not sure if TWR ATC will be interested in seeing that much of traffic on their primary/secondary radars unless it crosses their runways?
Ibra wrote:
In big airports, GND ATC already have movement sensors detectors/magnetic sensors (like GATS) or surface radar grids (ASDE-X in USA) to use for ground surveillance but I am not sure if TWR ATC will be interested in seeing that much of traffic on their primary/secondary radars unless it crosses their runways?
All airports I’ve seen that have mode S ground radar requests that on departure it is turned on in GND mode at block off and on arrival kept in GND mode until the aircraft is parked.
I think this could be an old tale. Why would you squawk SBY when changing the codes? The only reason as mentioned above is to avoid keying 7×00 by accident.
In a commercial aircraft you often get different squawk when changing the boundaries or entering an oceanic route, and by putting the xponder to standby you’d be momentarily turning off the TA/RA Tcas mode, which is of no benefit
The reason is probably lost in the mists of time. Like the reason for not using radios in the vicinity of refuelling, which dates back to the time of spark-gap transmitters, which went out of fashion in the early 1920s.
On a similar line, good luck explaining to the FAA that you can use today mobile phones inside CAT cabins on takeoff/landings (if you think a 100$ smartphone will interfere with a 50m$ aircraft equipment then you are in the wrong forum)
Ibra wrote
if you think a 100$ smartphone will interfere with a 50m$ aircraft equipment then you are in the wrong forum
We had a (nontechnical) discussion about this… I think the only instrument that might be affected is the ADF, which no one uses, and even then not sure
