3D Robotics

Glider pilot surprised by drone in thermal

3689577497?profile=originalA disquieting report from our friends in the manned soaring world. Yet another reminder to STAY BELOW 400 FEET!


From Soaring Cafe:

One of the pilots in our local soaring club was surprised to discover that he was sharing a thermal with a model aircraft [commonly referred to nowadays as 'Unmanned Aerial Vehicles' (UAVs)] at ~2,500′ MSL (~1,800′ AGL). With the proliferation of such aircraft, glider pilots may need to be especially vigilant for unmanned aircraft. As one of our club instructors informed us, in the United States, UAVs are required by the FAA to remain below 400′ AGL or have a Certificate of Authorization (CoA) to operate at higher altitudes (but see the link in the quote below for clarification on the FAA’s stance regarding UAV operating altitudes). CoAs are currently only issued for restricted areas in the Continental U.S.mIn any case, we need to be on the lookout for unmanned aerial companions while soaring.

Here’s the pilot report:

Today I had what looked like a fast quadcopter join me in a thermal above Cecil Ashburn Drive.

I think I was at about 3,100 feet MSL. The copter was about 500 feet below and gaining.
At first I though it was a bird, then a mylar balloon, then a manuevering craft with a red blinking light.
He was turning the same direction I was, but turning at a different rate so I couldn’t continuously see him.
I bugged out.

The thing that bugs me is that if there was a midair, he’d be out a copter, I’d just be out.

Anybody know what the rules are in this situation?
Prior arrangement for formation flying.
Glider versus powered right of way.
Anything goes if you can get away with it.

Here’s a link to the quadcopter community’s thoughts on the rules.


The quadcopter folks agree that AC-9157 does specify a limit of 400 feet and line of sight, But they say that the process that makes an AC is not a rule- making process with a public comment period and so is not binding on the general public. They claim that the FAA has admitted that this is correct in court. They say this leaves 14 CFR part 91. Does a particular section come to mind in there that might apply?

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  • But know-nothing newbies should not have free reign to use our system to fly like this.

    Ever hear of Trappy?  The worst offenders have turned out to be seasoned veterans.

  • Developer

    @Muhammad: Just sent the Geo Fence altitude to 120m

    @Rob: I think Skookum set a limit as part of there reduction in liability. 3DR RTF models come with the fence alt limit set to 100m. 3DR autopilot boards are shipped with no software on them, it up to the users. If you put a hard limit in the FW, people can still go download a version with it compiled out. (even if it's in an obscure piece of code). If somebody whats to be an idiot, you can't stop them ( and that includes cars, boats, bicycles you name it !)

  • Moderator

    I'm a little puzzled at all this altitude discussion that ignores the plain fact that for many years F3 Soaring rules have stated that competitions start at an altitude of 200 meters.


    So the 400 foot thing is not as set in stone as people make out.

  • It'd be very nice to have, at the very least, a warning in Mission Planner when altitude exceeds 400ft. 

  • IMO, this project should be hard coding in a 400 foot altitude limit.  We have to do SOMETHING to be part of the solution rather than part of the problem.  Make it a #define.  Advanced users who know exactly what they're doing can change it and compile.  But 99.9% of our users do not need to be flying over 400 feet from take-off.

    Even if it's just a parameter that's somewhat hard to find, I dunno...  But know-nothing newbies should not have free reign to use our system to fly like this.  Especially since some of them will do it in true ignorant innocence of what they're doing.

    The Skookum 720 GPS unit for flybarless helis also has a hard 500m limit for GPS usage.  I think that's a little short, but 1000m would be fairly reasonable.  Again, either a hard-coded limit, or hard to find parameter, I guess we can talk about that.

    But we have to do something.

  • Thanks for posting the incident report here on DIY Drones. Accordingly, this page has been updated in two places: Question 5 near the top, and at the bottom of the page. The page is intended for potential buyers of any kind of UAV or UAS product. Reports like the one in this blog post help to raise awareness of the risk of launching even a small aircraft.  

  • I still can't figure out what fun it is flying a multi-rotor to high altitudes. Just hovering in empty space. Can't glide, can't fly for long... 

  • One of the real problems here and one which the FAA has really done nothing to address is the confusion between Legal (Law) and advisory.

    AC-9157 is not law and is not legally binding - it is advisory in nature, not a legal obligation.

    I actually think it should be law and something like it probably will be law eventually, but for the time being it is an FAA "rule" perhaps, advisory definitely, but it is not a law.

    Until this kind of thing is explicitly legally clarified, these kind of events will continue to occur because of the extremely "Gray" status of them that the FAA and our legislators have allowed to continue to exist.

    I do know that the FAA is scrambling with all the speed of a substandard banana slug to establish appropriate rules and laws for all aspects of hobby and commercial UAS, but they really need to get on the stick or the go to the store and buy it newbe is going to stick a Phantom in the intake of a 777.

    And if that happens first you can be sure that whatever rules and laws follow will be Draconian and completely counter productive.

  • Moderator

    If the glider pilot has filed an airprox report the FAA will have to investigate.

  • imagine the impact if this thermal pilot was with a paraglider....

    i agree... STAY BELOW 400 FEET!

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