Brief Survey on ADS-B and Small Drones

I've got a brief 10-question survey which seeks to get your opinions about ADS-B solutions for small drones.

The technology for tracking small unmanned aircraft systems (UAS) has advanced rapidly in the past few years.  New and disparate solutions all claim great promise.  Many of these solutions are based on automatic dependent surveillance-broadcast (ADS–B), a cooperative surveillance technology in which an aircraft determines its position via satellite navigation and periodically broadcasts it, enabling it to be tracked by ground control station. ADS-B signals can also be received by other aircraft to provide situational awareness and allow self-separation.

But is it the right solution for small UAS (under 55 lbs.) operating in low-altitude class G airspace?

When its done I'll post the results back here in a new post.  Thanks much! - Colin

Take survey here:

Views: 1741

Comment by Clay Cranor on August 12, 2015 at 7:56pm

I do take issue with the assumption that at least some drones should have ADS-B out for flying in Class G airspace.  I see no reason to require UAVs to have ADS-B out when manned aircraft do not.  Most full sized aircraft operating in class G (less than 1200' AGL) will not have ADS-B out, or -in, and will not benefit from UAVs in the airspace from having it.  There is no requirement for communication with ATC in this airspace either.  G airspace is uncontrolled airspace, ATC has no control authority.  Having said that, long range UAVs, operating out of line of sight, and in airspace other than G, should have this technology.  Perhaps UAVs that fly these types of missions could have unique transponder codes (without the ADS-B complexity) for ATC recognition.  I do have a problem requiring an extremely expensive package like ADS-B being required on UAVs for operation in airspace where full sized manned aircraft do not.  Certainly not for hobby machines operating within LOS, below 400'.

Comment by Colin Snow on August 12, 2015 at 8:40pm

Clay, I agree.  I'll wait to comment further until after the survey is closed. 

Comment by Gary Mortimer on August 12, 2015 at 9:01pm

Manned aircraft will have to comply by 2020, just one year before you get proper RPAS rules ;-) Don't forget with a $20 USB dongle you can already see ADSB traffic on Mission Planner. It need not be a large or expensive tech. Personally I think the sUAS world should leap forward and shame the manned community with this tech.

Comment by JB on August 12, 2015 at 9:12pm

I think "ADS-B in" should be introduced first as this is the lowest cost solution and will likely result in the most significant safety benefits to UAS/UAV operations. Some TIS-B functionality to enforce TFRs etc would be good to see around high air traffic areas like airports.

A SBC (single board computer) similar to the Raspi/BBB running an RTL2832 USB dongle could provide an entry level ADS-B receiver for around $50 and could be utilized as a rudimentary "sense and avoid" system. A more customized system could be developed around that and could use a variation of "ADS-B out" via 3G/4G GSM to update an online ADS-B database, that in turn could be filtered and verified before being pushed out through the relevant areas of the ADS-B network. That would only add another $30 for a USB 3G modem (total system weight around 80g) and would keep the system cost under $100, plus it can double as a onboard computer for imaging, navigation or autopilot, even passive radar is possible using a supplemental ground unit using the same hardware etc.

The problem arises that every system can be bypassed, including ADS-B used for traffic management, so the safety risk remains with the experience and intent of the user. "Stupid people" will continue to do stupid things and as a consequence I see ADS-B technology on UAS/UAV platforms as more of an aid to keep them out of the trouble they would get themselves into without it, under normal operations. In fact, if there's malice intent, ADS-B systems can be used to target aircraft instead of avoiding them, so there's also a potential risk in painting the sky with potential targets using ADS-B technology as well. Even though UAV's are typically low value targets, full size aircraft are, provided you can disrupt their operations or possibly catch them.

Like with most modern systems there is always a safety and security risk aspect to "universal surveillance", and sharing that information in real time and "unfiltered" with all third parties can leave the whole system vulnerable to manipulation by people with ill intent. I think the ADS-B out needs to be filtered and verified before use to avoid "phantom" traffic disrupting high value air traffic, which is possible via the 3G/database system proposed above. Especially so if that system is heavily relied on for safe operation of all forms of aircraft, and significantly displaces other, sometimes common sense based systems that have worked so far. There also needs to be some segregation between manned and unmanned systems, especially in their management and regulation.

The biggest issue with UAV safety (being an UN-manned Aerial Vehicle) is simply the fact that there is no pilot onboard the aircraft so that all "pilot self preservation instincts" are circumvented. Typically, and especially for the novice, the only perceived risk of the UAV operator is that the consequence of a failed UAV flight amounts to "only" the cost of a replacement UAV. This fallacy needs to be addressed in the consciousness of the that the fear that promotes self-preservation also promotes safe UAV operation, as it does (mostly) in manned aviation. Put simply: the user needs to be vigilant and remain response-able for their actions, especially so when the technology aids they use fail.



BTW your questionnaire is very USA focused. I think the world needs a solution and standard for this one! :-)

Comment by Gary Mortimer on August 12, 2015 at 9:24pm

Yes education will be a big thing. I remember a chap switching on a portable transponder whilst driving around the M25 in London, just to fiddle with it. But the ensuing squawk caused chaos at heathrow until they realised where it was. There is no doubt more training would be required for RPAS users. I guess having to have at least a sports pilots licence is no bad thing in the USA as at least you will have heard of this tech. 

Comment by Andrew Rabbitt on August 12, 2015 at 9:44pm

Is it possible/legal to broadcast ADS-B from the ground station?  Presumably the ground station already knows where the UAV is and it could broadcast at a much higher power level than might be available onboard.

Comment by Patrick Egan on August 12, 2015 at 10:00pm

Did you listen to the podcast? ;-) I plan to have another fellow on the broadcast who is very well versed in airspace integration issues.


I am very interested in your findings and I wasn't to compare them to insider feedback. 

Comment by JB on August 12, 2015 at 10:15pm

I agree Gary.

"Intended" use of technology does not exclude "unintended" use and possible negative outcomes!

You can use a hammer as a building implement to hit nails in a wall or as a weapon...only the user can give it a "good or evil" purpose. The more complex tools and technology become, the more sophisticated the user needs to be to use it "properly", which in turn increases the risk resulting from poor training, especially when such a system fails. Also the more complex the system the harder it gets to identify potential risks or undesired outcomes. Even the best system only works as desired/designed if all the users operate said system as intended by the designer. Take the "financial system" as an example. Or the fact that the most relevant danger presented to manned aircraft by UAVs is to small manned aircraft (and not airliners!), that typically don't have ADS-B and can't participate in the "system" anyway!

Also if the system is large and affects many others, the added complexity of the system reduces the ability of any user, especially in an emergency situation, to act appropriately. Adding "technological solutions" typically also adds other risks higher in the hierarchy of the overall purpose of the system, especially so if the system is ill conceived and cannot forecast, at a minimum, major conflicts in user "interests". The term avoidance, inherently involves a state of perpetual foresight. It is after all the user, us the people, that drive the the intention and purpose of any idea we conceive, build and operate.

This begs the question, what, if at all, we should develop. If our purposes are flawed by our warped perception of reality, which is culturally ingrained in our persona from birth, then isn't every solution we unwittingly produce in our infirmity potentially the source of another persons problem?

How well do you know that "chap" driving around on the M25 BTW? ;-)



Comment by Gary Mortimer on August 12, 2015 at 10:40pm

I did'nt know that particular chap, just some of the shift workers at Heathrow that dealt with it. I do know some other stories that may or may not have involved me and as such best heard over a beer ;-) Perhaps going out of fashion, primary radio contacts as well. When I worked in North Devon we had a spot in the hills where vans would appear painted on the radar, that is to say the radar picked up vehicles driving on high ground. RAF Lyneham had the railway line between Bristol and London marked as east west primary traffic would pop up on that. So having ADSB could well help remove the clutter. I see no sense in rushing to integrate last years tech with old fashioned transponders. All the N numbers being generated in the USA have suitable ICAO identifiers.

With the 333 system the FAA now have more than 1000 operators they can turn to for trials.

@Andrew, something like that is already in hand.

Comment by JB on August 12, 2015 at 11:34pm

Lol Gary.

I'm sure we all have some stories to share over a drink! ;-)

I agree on the problem with trying to integrate legacy systems.

I've proposed this elsewhere here on the forum as well, and that is the other "contentious" issue with airspace is the "airwaves" that is locked up in "analog mentality" and regulation that is outdated in the digital age of data packets n Co. This would remove the "clutter" as you say from a lot more industries that exhibit monopoly traits and stifle development.

I think a much better solution would be to have a non-centralized mesh network to relay relevant information between users that are in proximity. That way all participants also help maintain coverage and infrastructure, with mesh routing this also increases system capacity as more users come in range, which in turn reduces cost, provides resilience to outages and disruptions, security against localized and systemic manipulation, and allows for both incremental and substantial improvements to be made over time without significant hardware updates etc. With packet routing done this way there's even the possibly to expand ADS-B with telemetry, comms channels, data relay and even aircraft inter-net-connectivity with the ground. A type of swarming hive of inter-dependent nodes. For lack of a better term: A "smart sky".

But maybe I've just been watching too many Star Trek episodes about the Borg? ;-)



I think that the ADS-B system will need to be implemented on the UAV itself so that it can operate even on loss of comms with the ground station. The ADS-B "out" system could be potentially integrated on the base station (e.g. via 3G), but I can see issues arising through the mis-use of low cot ADS-B transponders to disrupt traffic without some sort or verification.

I'd also expect that an air based system won't experience as much signal loss through ground proximity and obstacles, and having the transmitter in the air at altitude would more than compensate for the reduction in signal strength due to the UAV size, weight and power constraints. The objective of ADS-B out is to inform other airspace users, preferably at range, which typically means line of sight to the receiver from the transmitter (at around 1GHz), so I'd imagine an airborne solution will always be favorable to a ground one. ADS-B output ranges from 7-40W, but have fairly short transmission cycles around 0.03%, so power use isn't that bad anyway and can be achieved on the UAV, provided the TX equipment is compact. I'd say about 1Wh of battery per 30 minutes of flight should cover it.

The other thing is that UAV ADS-B out would only be required to manage airspace safety, so even a few kilometers of range should suffice for avoidance. The UAV is both low speed and low altitude and therefore out of "range" of manned airspace users that also use the ADS-B for inflight course corrections, should other aircraft, that could be approaching at super sonic speeds not adhere to their flight plan or airspace control. For example: two commercial aircraft flying head on is an approach at 500m/s(!) So you'd want at least 30sec or 15km RF range up there with the big boys! Airline with UAV interaction on approach or departure at low altitude will be nearly one order of magnitude slower by comparison, so the range can safely be less to maintain enough reaction time, which means a low powered UAV mounted system will suffice.


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