ADS-B should sequence airplanes at nontowered airports?

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

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. 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).

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: “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.”

Americans have spent billions of dollars over the last twenty years on ADS-B, 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.

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”?

3 thoughts on “ADS-B should sequence airplanes at nontowered airports?

  1. ADS-B out provides information about the position and movement of the aircraft transmitting it. Other aircraft can display this information if they have a receiver and a system to process the data. There would have to be some system at the airport to do some AI on the collection of the nearby aircraft and have some way to know their intentions. I believe there are too many problems with this.

    They are working on remote and virtual control towers where the controllers are located away from the airport with video information. It has the same rules as if it were located at the airport.

  2. Tom: Why can’t the ADS-B boxes run software that cooperates in a similar way to (1989)? TCAS II provides complementary resolution advisories without any central ground-based processing. One airplane tells the pilots “climb” and the other “descend”.

    This needs AI? Given that a traffic pattern is essentially one-dimensional (a series of line segments), how can this require “AI”?

  3. It’s more complex then accident avoidance. There are issues with intentions, flight characteristics, aircraft performance, pilot skills, priorities or emergencies, airspace, CFIT, weather, etc..

    Can you imagine departing at 200 feet and hearing, sierra delta you are number 1 for landing, 3 aircraft in the pattern, left traffic? Lots of factors in sequencing. And there is a difference when a tower asks you to do something and you verify and confirm you will take those actions.

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