Comment by korethr | Hacker News Reader

Comment by korethr | Hacker News Reader

I recall reading a proposal about this before, and I'll echo it here. There's already a solution to avoid aircraft collisions, mentioned in the article: ADS-B. Why not equip drones with ADS-B transceivers, enabling both drones and planes to be aware of each other's presence and avoid one another?

A counter argument I can anticipate is that with all those drones in the air, broadcasting ADS-B, they will clog up the system with too many signals. Those who make the argument aren't wrong. I propose a solution for that as well: reduced transmission power on drone ADS-B transceivers. Small craft have a minimum transmission power of 75W, and craft that can fly over 15000 ft or faster than 175 kt have to transmit at at least 125W. Few drones are going to be moving that fast or that high. So why not make them have say, a transmission power of 1W? I'd think that would be enough power to warn planes on approach to an airport to watch out for nearby drones, without clogging up the system with useless noise about drones the next city over.

ADS-B alone is insufficient for collision avoidance. In order to operate safely outside of special restricted airspace, drones would need to be able to visually see and avoid other aircraft.

(agreeing and amplifying)

ADS-B out is only mandated in an extremely limited subset of the airspace where drones will be likely flying (and then only after Jan 1, 2020).

ADS-B out is only mandated[1] in cylinders around class C and the 30nm ring around class B airports, in class A airspace (at/above 18000' MSL), and in class E airspace that is both above 10000' MSL and 2500' AGL.

In practice, that means that most of the volume of drone-navigable airspace does not require other aircraft to have ADS-B out transmitters.

In none of the airspace are other aircraft required to have ADS-B in receivers.

"See and avoid" is therefore both practically and legally[2] required.

[1] - 14 CFR § 91.225 - https://www.law.cornell.edu/cfr/text/14/91.225

[2] - 14 CFR § 91.113 - https://www.law.cornell.edu/cfr/text/14/91.113

Not to mention even in all those areas (except A and B airspace), there are still aircraft exempt from the ADS-B requirement. The mandate only applies to aircraft certificated with an engine driven electrical system, so gliders and piper cubs and those sorts of aircraft will still need see and avoid.

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