If we want piloted airplanes and drones to share the skies, we need to figure out how to keep them apart. One of the biggest barriers to bringing drones into common use is the threat of collision. Small ones are especially hard to see from a distance, and are sometimes operated by well-meaning but clueless amateurs. A company called uAvionix thinks it has the answer: a tiny Automatic Dependent Surveillance-Broadcast, or ADS-B, small enough to fit even on small, personal drones.
ADS-B is the emerging backbone of global air traffic control. The national airspace system will depend on each aircraft broadcasting its identification, altitude, position, and speed once every second, to provide a radar-like picture where no radar exists. Because the system allows aircraft to electronically “see” each other clearly, instead of relying on (very limited) vision or on human air traffic controllers, it reduces the potential for mid-air collisions.
When ADS-B was conceived, however, almost no one was thinking about drones and airliners sharing the skies. Few imagined that by 2016 the FAA would register over 600,000 drones, which now outnumber piloted aircraft. And that’s not even counting all the 1.9 million drones sold in this country last year. With those kinds of numbers, the problem won’t go away.
Some larger drones, particularly fixed-wing aircraft used by scientists and industry, already incorporate ADS-B. These aircraft are big enough and have enough electrical power to use ADS-B systems designed for piloted aircraft. The problem is installing ADS-B in something like a DJI Phantom 4 quadcopter. Aside from being small, these drones have very limited power. Conventional ADS-B systems designed for piloted aircraft would add too much weight, draw too much power, and cost too much to be practical for small quadcopters.
So uAvionix has just introduced a prototype ADS-B transceiver they call The Tiny UAT (Universal Access Transceiver). Smaller than a dime and weighing only 1 gram, or ¼ the weight of a typical piece of 8.5 x 11 paper, the device is designed to be built into small drones, just as car manufacturers include radios in cars.
The Tiny UAT transmits only .01 to .25 watts. According to Ryan Reed of uAvionix, those power levels have a negligible impact on quadcopter battery life but are strong enough to alert ADS-B-capable airplanes up to 10 miles away. And they can easily transmit using cellphone batteries.
There are still problems, however. The Tiny UAT, at least in its current incarnation, doesn’t transmit enough power to meet FAA regulations. (The minimum transmitting power for ADS-B is seven watts, a legacy of the standards for piloted aircraft.) Nor is the ADS-B system designed to handle large numbers of small drones. The sheer volume of UAVs transmitting at seven watts would overwhelm Air Traffic Control computers and cause the system to crash, leading to chaos in the skies and crippling air traffic across the country. Complicating matters further, large numbers of drones can be active in a relatively tiny airspace. In close proximity, even at seven watts, drones would essentially jam each other’s transmissions. Consequently, the FAA is evaluating research suggesting that small drones using ADS-B should use a lot less power. That would mean fewer signals reaching Air Traffic Control, which would reduce computer workloads.