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Comment by SnowHill9902 | Hacker News Reader

Can’t you trivially turn off a transponder?

Technically yes, legally no, with a few exceptions for military and special operations. Most airspaces are TMZ (transponder mandatory zone).

I’m guessing it’s a great way to get fined or even banned from landing at the airports worth landing at.

Yes. But that will trivially attract the attention of the FAA and, most likely, civil air defense.

Sure, but you still have to file a flight plan before you can get on a runway. Flight plans are quite detailed. I suppose you could file a fake flight plan though.

Small aircraft flying visual rules (VFR) in lightly used airspaces like class A don't need to file plans. Look around any small airport and you'll see Cessnas doing training loops all day long. No flight plans. But their ADS-B transponders are always on.

https://globe.adsbexchange.com/

You can't turn off an ultra-hi-res NRO satellite which is viewing/recording this plane's flight in real time.

Wouldn't that be very illegal and noticed by every airport you ever land in?

Inside the continental US, if you fly a small not-turbine-engine-powered airplane yourself and only go to rural airports with no tower, it is actually legal to have no transponder (see below, 91.215(b), 91.225(b)).

But, if the transponder is installed, you are legally required to turn it on at all times no matter where you are (see 91.215(b)(3), "all controlled airspace" means everything above 700-1200ft AGL (depending on exactly where)).

So for this to be legal, you can't just turn if off: you have to actually remove it from the airplane. Whether that is legal additionally depends on the airplane.

https://www.law.cornell.edu/cfr/text/14/91.215 https://www.law.cornell.edu/cfr/text/14/91.225

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