The tragic midair collision at Reagan Washington National Airport in January this year brought the focus on the congested airspace over the airport. The Federal Aviation Administration has implemented some restrictions around its airspace as the investigation into the crash continues.
This is really interesting, and the article comments are total crap. TCAS alerts are based on peer to peer digital transponder signals. It seems like it would take some deliberate effort to spoof them
That and from what I’ve read, in cities such as DC, you disable the TCAS warnings on approach as you’ll get way too many false positives.
TCAS is programmed not to give alerts below 500 feet above ground.
One reason is that, to keep the system simple, TCAS resolution advisories only ever say to go up or down. That close to the ground a regular resolution advisory would tell one aircraft to dive into the ground–so the advisories are suppressed.