Just wondering if anyone has tethered their aircraft e.g tying a 20 foot lanyard to one of the legs, just to enable basic testing of functions where the proposed flight may be within the 50m rule in the UK.
I heard of a local dealer who was tethering aircraft when testing close to a main highway to comply with CAA requirements.

Has anyone any experience of this in the UK.  

Very stupid idea and whoever that dealer was has no concept of how a flight controller works! In tethering or fixing a dynamically controlled multirotor you will encounter what is know as integral wind up due to the closed loop feedback system. The craft will fight the tether to attempt to stay airborne and the more it applies corrective thrust the less it will move, therefore it will try harder until full power is attained. Avoid doing this at all costs.

Tharg beat me to it, and explained it better than I could have too... lol...  I agree completely...  well said.

Jim

igor sikorsky didn't have much luck in the early days with a tethered helicopter. The tether would pull inputs into the helicopter and cause it to crash on its side. He finally removed the tether completely during his early testing.

This is not a good idea.

http://tse1.mm.bing.net/th?& ... s=0&p=0&r=0


Rich

Yes, I don't disagree with all the comments above.  
However if the tether remains slack at all times and never taught or under strain, it will never apply any undue torque or affect the thrust of the engines as no force being applied to restrain the aircraft.

I have heard of others using 550lb Para cord as a tether and it has been successful.  The dealer who I shall keep anonymous as it would be unfair to disclose, is a well respected dealership with experienced Pilots.  The use of a tether was I am informed a suggestion from the UK CAA as an alternative or method of reducing risk when used near to populated areas or motorways/freeways.  As said, the tether never becomes taught and the line simply hangs down from the aircraft.  In this way the aircraft can be fully tested, obviously the return to home function could not be tested, but all the other main functions could be tested with the safe knowledge that the aircraft could not endanger anyone nearby thus reducing the risk to an acceptable level for compliance with the UK CAA.  The idea being if the proposed test was to fly to say 15m altitude, the tether would be around 20m to ensure the tether was slack at all times and the only time it would become taught would be in an uncontrolled event.  

I think the key thing here is that as highlighted correctly above, if the tether was put under any strain or tension, this would cause subsequent problems for the motors and certainly is not to be undertaken by any novice.  However, with an experienced Pilot, could this be a safe test in a controlled environment, although I am certainly not endorsing its use myself.  I simply wanted to throw this into the forum for discussion and education.
All comments welcomed, positive or negative.  Thats how we all learn.


  

GB44 Posted at 2016-5-1 10:39
Yes, I don't disagree with all the comments above.  
However if the tether remains slack at all time ...

I believe your theory is sound, if the tether is slack enough it should not effect the flight. However if something goes wrong it could turn ugly pretty fast. If the tether is too slack it could end up tangled in a prop.
I'd be inclined to take it to a safe place where a tether isn't needed.

You want to tie a string to your drone?  Hahahaha!!!! This is the dumbest idea ever! I hope they don't ever put in a such a silly regulation like that

On first consideration, tethering a quadcopter as a means of risk mitigation sounds like a great idea.
Keep a physical limit to the extent to which the craft can navigate, either in a controlled or uncontrolled manner to ensure that persons are kept from harm.

The practical issues however make the approach risky as the craft's systems have no way to deal with the physical limit once it is encountered.
The issue of snagging lines in the props on takeoff is real - I have been working with a 'Stork' payload release system on the inspire and while it works exceptionally well, the cordage attaching a payload to the release is a real safety issue. Still haven't cracked that one yet!

From a commercial risk management perspective, I'd suggest that if the proposed flight is inherently risky to the degree that a physical restraint is called for, then a UAV is NOT the tool for the job.   

I have been carrying out test for the larst 6 mouths for a company in Cheshire and the CAA, with a S900 on a 30 meter tether, it has caused numerous problems to the flying characteristics to such a point the CAA have insisted on a relasase mechanism.,The project is now 3 months behind schedule because of the tether.

Unless you are a very experienced pilot don't do it.
I have over 40 years RC flying and full size helicopter experience and find it very challenging.

Arrow1969 Posted at 2016-5-2 03:44
I have been carrying out test for the larst 6 mouths for a company in Cheshire and the CAA, with a S ...

Thanks for your input guys.

Obviously not a process that most experienced Pilots would recommend.

Interesting that the CAA requested a release system.  Sort of defeats the point of the CAA requiring a tether in the first place for some operations.

I think we can all agree here, tethering should not be undertaken unless by an experienced Pilot and even then probably under duress by others such as the CAA to mitigate risk issues which can't otherwise be removed or reduced.

Some good feed back though.

What about all the powered tether systems in use with DJI Inspire and other drones? If the tether is slack, and will not connect with the props, what is the impact on flight performance?

There's numerous methods of tethering an Inspire 2 out there if you look for "Tether Inspire 2."  Most were designed for additional air/run time.

Videos:



Systems:
https://www.riseabove.com.au/pow ... r-system-for-drones
https://www.droneaviationcorp.com/solutions/fuse-tether-system
https://www.ntpdrone.com/product/

If properly implemented a tether will work Law enforcement has been using Powered Tethers for long duration flight! There lot of variables here but it's definitely possible! When the wright brothers were trying to invent the plane everyone said they were crazy and it couldn't be done! Look at what we have now!!! I am actually working on a Non Powered Tether for recovy and it's been working great I have over 10 hours of flight time and no crashes yet! It's not for every situation I am focusing on recovery over water! Sure a bird or something  could come in contact with the tether (that's something I'm working on because the line I'm using is almost invisible to the naked eye) the material I'm using is extremely light and has almost no drag on my Drones it had a over a 100 lb breaking strength and I have already figured out how to keep it from getting Tangled in the rotors! That was the easy part ! I'm working on a automatic winch that leaves enough slack in the line now I need 2 people