ADS-B Transponders

The skies of the future are going to be busy – with a mixture of manned and unmanned vehicles sharing increasingly crowded skies. Whether it’s Amazon Prime Air, ZipLine, or a professional cinematographer with a DJI drone high in the sky, there are going to be more things flying in this “integrated” airspace than ever before.

There’s no shortage of startups with some bold ideas about how this integration might occur, using a sophisticated blend of hardware and software that can handshake with the existing air traffic control network.

It’s such a big deal that NASA is in charge of looking at how things might unfold. In fact, the agency has been examining this issue since at least 2011. Take a look at this graphic from 2014, which gives you a hint of the complexities involved:

unmanned aircraft systems NAS project

As the graphic says, this ambitious project is known as Unmanned Aircraft Systems (UAS) Integration in the National Airspace System (NAS) Project. And the good news is that in NASA’s mind there is absolutely no question this system will happen.

“The UAS in the NAS project envisions performance-based routine access to all segments of the national airspace for all unmanned aircraft system classes, once all safety-related and technical barriers are overcome,” reads the 2014 document.

Back in 2012, the FAA Modernization and Reform Act was signed into law. It provided some pretty specific guidelines for integrating small aircraft (less than four pounds) quickly, with a goal of integrating larger UAS weighing up to 55 pounds by 2015.


As often happens, things take a little longer than planned. And it’s easy to see why: Putting unmanned vehicles into the skies – or at least into the skies where manned aircraft fly – must be handled very carefully. Though there have been no verified serious collisions between manned aircraft and UAS, it’s obviously something regulators, pilots, passengers – everyone – wants to avoid.

uAvionix image of how its ADS-B system provides situational awareness of airspace
uAvionix image of how its ADS-B system provides situational awareness of airspace

The recent Part 107 rule in the US opened up the skies to commercial operators who can pass a test and are willing to follow some basic common-sense rules: Stay away from airports and flight paths, don’t fly over people or traffic, don’t fly at night unless you’ve obtained special permission to do so, etc. In other words, use common sense and have the requisite skills and knowledge to fly.

So far, so good.

But that’s not really airspace integration; it’s actually more like airspace segregation, where regulations are set in place to ensure UAS will not be near manned aircraft except with special permission, for special reasons, and with additional precautions. And, for the moment, that also makes sense.


Really, when you think of it (and certainly when NASA and the FAA think of it), a lot of separate cogs have to operate seamlessly on the new machine. A few of the many items on the agenda include:

  • Ensuring that UAS frequencies don’t interfere with manned aircraft
  • Ensuring that UAS vehicles and their avionics meet stringent airworthiness criteria
  • Having redundant systems to reduce the possibility of in-flight failures
  • Integrating the tracking of UAS into the regular air traffic control system
  • Perfecting a highly accurate, likely autonomous, sense-and-avoid system to avert potential collision
  • Test, evaluate, tweak, improve
  • Implement

That’s a lot of stuff – and NASA is now very involved (with a lot of partners) on a project called UAS Traffic Management System (UTM) for drones flying at lower altitudes. Between that and other technical developments, things are accelerating. And there’s a growing sense that true integration is coming before very long.

ADS-B Transponder – SIZE MATTERS!

Part of the reason behind that is due to great (and tiny) leaps and bounds in the miniaturization of a specific piece of technology. It’s something called the ADS-B transponder, meaning Automatic Dependent Surveillance – Broadcast.

It’s a piece of gear required on manned aircraft flying in specific airspace categories – and which will become mandatory on all aircraft by 2020. We won’t go into all the details of this FAA graphic, but it gives you a good sense of how the skies are broken up into specific airspace groups, each with their own specific rules.

Transponders are already required in many categories of airspace. They will be mandatory on all aircraft by 2020. FAA Image
Transponders are already required in many categories of airspace. They will be mandatory on all aircraft by 2020. FAA Image

The technology determines an aircraft’s position in the sky and broadcasts that location at regular intervals. It also can carry a unique identifier for that particular aircraft, so people manning ground stations or air traffic control (or other pilots) can see who’s who – and where they’re heading.

For smaller UAS, the issue in the past has been size and weight. ADS-B transponders had been built for manned aircraft, too large and heavy for small drones.

Now, several companies are manufacturing ADS-B units that can be placed (and are being placed or tested) on small unmanned aircraft. One of those companies is uAvionix, at the forefront of shrinking critical avionics components.

The demand is great. The uAvionix website points out more than 600,000 UAS were registered in 2016 – double the number of manned aircraft.

“Current radio solutions are bulky and expensive to build,” says its site. “Modern processes and silicon can reduce the size, weight and complexity of aviation safety systems.”

uAvionix builds a series of devices under the brand name “ping.” They include transponders, transceivers and navigation sources. One model, the ping 200s, is billed as “the world’s smallest, lightest, most affordable and FCC approved full range Mode C and Mode S ADS-B transponder. At just 50 grams, it implements ‘Sense and Avoid’ for Drone operations in the national airspace,” says the website.

A uAvionix ADS-B transponder that weighs but 50 grams.
A uAvionix ADS-B transponder that weighs but 50 grams. uAvionix Image

“Autopilots can use Ping data to plot the current course of an inbound aircraft and avoid it miles in advance of a near-miss,” it says. “Manned aircraft and air traffic control can ‘see’ ping equipped drones on screen in the cockpit and the tower.”

In fact, a video on the site shows some of the ping gear mounted on a DJI Matrice. DJI is one of several partners working in collaboration with uAvionix, including NASA, NavCanada, the FAA, Draganfly Innovations, and more.

The ping series does not require a 3G or 4G connection. But it has dawned on TDC that the new Inspire 2 is equipped for a 4G dongle, which might well be put to use for some sort of tracking or ADS-B-type use in the future – especially with the SDK open developer’s kit.

Inspire Pro
The I2 is pictured here with a Zenmuse X5S. You can also see the small FPV camera above it, in this pre-production model. Photo by Chris So, The Digital Circuit

We have no idea whether this will ever come to fruition on the I2 or not. But TDC is certainly confident the next generation of high-end drones (and certainly some of the current models) will be ADS-B capable – with a simple retrofit of currently available uAvionix devices.

The new smaller avionix gear can be easily integrated into existing flight controllers, such as the popular pixhawk.
The new smaller avionix gear can be easily integrated into existing flight controllers, such as the popular pixhawk. uAvionix Image

That’s one small step for miniaturization – one giant leap for safe skies.


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