{"id":21198,"date":"2018-11-04T12:29:17","date_gmt":"2018-11-04T17:29:17","guid":{"rendered":"https:\/\/philip.greenspun.com\/blog\/?p=21198"},"modified":"2018-11-04T17:02:51","modified_gmt":"2018-11-04T22:02:51","slug":"ads-b-should-sequence-airplanes-at-nontowered-airports","status":"publish","type":"post","link":"https:\/\/philip.greenspun.com\/blog\/2018\/11\/04\/ads-b-should-sequence-airplanes-at-nontowered-airports\/","title":{"rendered":"ADS-B should sequence airplanes at nontowered airports?"},"content":{"rendered":"\n

I flew the Cirrus<\/a> recently to Gaithersburg, an airport that supposedly sees only 131 operations per day (airnav<\/a>). On the flight from Allentown, Pennsylvania to KGAI, the controllers did not even once tell me to look for a nearby plane. I was pretty much alone in the sky at 6,000′.<\/p>\n\n\n\n

Things were different within 5 miles of the destination airport. I arrived on a gusty bumpy Tuesday at 1 pm and became the fourth airplane in the pattern as this non-towered airport. I departed behind a Pilatus PC-12<\/a>. The Pilatus crew waited for a small plane to land before they could depart. I asked a plane on downwind to extend slightly so that I could get out with my IFR clearance (i.e., there were at least four airplanes operating at 5 pm when I departed). Given the active flight school at KGAI and the fact that I have nearly always found myself with company in the traffic pattern there, I question the 131\/day number (since there is no control tower, the statistic may not be authoritative).<\/p>\n\n\n\n

There is some structure to the traffic pattern at an airport that makes it a bit easier for pilots to identify each other, but self-sequencing is not always successful. AOPA’s Air Safety Institute:\u00a0 “Eighty percent of the midair collisions that occurred during ‘normal’ [not formation or aerobatics] flight activities happened within ten miles of an airport, and 78 percent of the midair collisions that occurred around the traffic pattern happened at nontowered airports.”<\/p>\n\n\n\n

Americans have spent billions of dollars over the last twenty years on ADS-B<\/a>, partly sold as a way to avoid midair collisions. I’m wondering now, though, if ADS-B solves the wrong problem and\/or the non-problem of enroute traffic conflicts.<\/p>\n\n\n\n

Maybe it was too advanced an idea in the 1990s when ADS-B was conceived (with an implementation date of Jan 1, 2020!), but I wonder if it would make sense for ADS-B gear to sequence airplanes at nontowered airports. Why couldn’t the pilot press a button on the transponder and have the ADS-B software say “You are Number 3 for Runway 32. Number 2 is turning right base. Number 1 is on final”?<\/p>\n","protected":false},"excerpt":{"rendered":"

I flew the Cirrus recently to Gaithersburg, an airport that supposedly sees only 131 operations per day (airnav). 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