[KaiMartin]

The current issue of the DHV-Info contains an incredibly detailed article on the possibility of HG/PG tow by a dedicated multicopter.
The article is available online: https://www.dhv.de/medien/archiv/artikel-archiv/geraetetechnik/drachen/multicopterschlepp/ (German language only.)

German regulations are fairly relaxed for drones and model planes below 25 kg weight. According to the authors calculations, a multicopter at this weight built with readily available components should be able tow 125 kg of HG + Pilot to 700 m. Alternatively, it might be desirable to do an interactive search for thermals at low height. This may drastically relax legal issues since airspace below 150 m is essentially unregulated in Germany.

The authors propose to use the hang glider to carry not only the pilot but also the multicopter. That is, the copter will tilt to vertical and use use all of its thrust to pull horizontally. The glider will fly about 100 m above and behind the multicopter. This reminded me of the alternative ways to get into the air proposed by Joe Faust on the US-Hawks forum.

In many ways, the proposed copter tow is kind of an intermediate between UL tow and static tow. The authors see some unique advantages, too: It requires less requirements for the terrain compared to traditional tow. Tow speed can be arbitrarily low. Due to the low mass the multicopter is physically unable to pull the glider into fully developed lock-out.

Moderators note: Fixed typo regarding weight of the multicopter at request of original poster.

[Bob Kuczewski]

Those are all excellent points. In addition to everything you've listed, the drone could be 100% vigilant on the status of the tow and actively respond for the best outcome for the pilot regardless of the consequences for itself.

I am, however, curious as to how the FAA would view a bunch of drones cooperating on a task. At what point do they become one aircraft?

Lots of good food for thought. Thanks for posting.

[JoeF]

In 1979:
Remote control hang glider towing aircraft
US4248394A
Marlin K. Klumpp

[Bob Kuczewski]

Thanks Joe! Happy Independence day to you!!

The engine used to motorize the towing aircraft 12 of FIGS. 1-3 is preferably a small, light two-cycle air-cooled gasoline engine of about 25-35 hp. A plurality of engines suitable for the purpose of the invention are available on the market, such as engines used to propel snowmobiles. The power unit including the engine, fuel, the housing 48, and the tricycle landing gear 42 can be supplied in the form of a module, which may also include the radio receiver and the control servos, which is bolted on and disconnected from the wings relatively rapidly and without any special skills. The module unit has a total weight, of about 150-170 lbs., that is not more than the weight of a pilot of normal weight, and much less than the combined weight of a pilot and of the power unit used to motorize hang gliders, with the result that the speed envelope of the tractor aircraft matches the speed envelope of the towed piloted hang glider, and that the rates of climb of the two flying machines are perfectly matched. The total weight of the tractor aircraft is about 210 lbs.

That was 1979. With today's technology, this becomes much more realistic. The 3D agility of a drone could react to almost any situation. With computerized control and multiple sensors (towline tension, GPS, airspeed, camera view of the hang glider, etc) it could be fixing problems before the pilot even knows they exist. It could easily become the safest way to get a hang glider into the air.

[wingspan33]

Thought that I would provide a translated version of the German language article -

https://translate.google.com/translate? ... schlepp%2F

This is an interesting topic. I own a four (non toy) quadcopters but I don't think that, even combined, they could help me get off the ground. They must be talking about a fairly large quadcopter/multi rotor.

[KaiMartin]

This is an interesting topic. I own a four (non toy) quadcopters but I don't think that, even combined, they could help me get off the ground. They must be talking about a fairly large quadcopter/multi rotor.

Yes, they do. The calculations were done for a multicopter with 25 kg total lift-off weight.

(Doh, I messed up the decimal point in my post above. I will go ahead and edit the value..)
→ Apparently, I don't get edit buttons on the original post.

---<)kaimartin(>---

[wingspan33]

Okay. 25 kilograms is about 55 lbs so that is a fairly BIG multi rotor! One that size could probably generate a good bit of thrust.

[Bob Kuczewski]

(Doh, I messed up the decimal point in my post above. I will go ahead and edit the value..)
→ Apparently, I don't get edit buttons on the original post.

We currently have a 4 hour window to edit posts. We do that for a number of reasons. It was originally 1 hour, but the Board voted to extend it to 4 hours in response to a member's request.

If you want something corrected, you can post a correction request or send a "PM" to myself or another Board member (who can relay it to me).

The primary purpose of the edit limit is to keep people from rewriting their own history after others have posted a response. We like the forum to reflect what was actually said so people can trust what they read. If significant changes are made after the 4 hour limit, they'll generally be noted as such in the post.

In this case, please feel free to send me the specifics of what you'd like changed.

Thanks.