Replies to This Discussion

Permalink Reply by Veikko Vierola on March 26, 2012 at 2:14pm

There is something that I don't understand; I have never heard about 2,5kg rc (uav) having a collision with any full size aircraft. But I have heard many stories about 7kg geese hitting airplane at 4000ft! What is the real threat in the airspace for the full sized aircrafts -> BIRDS! And birds have no intention to go away when aircraft approaches. RC hobbyist knows when aircraft approaches and are able to fly the RC model to low altitudes. I think FAA should think more about the reality and the probability of the collision with rc uav. Propability of collision with a bird is perhaps something like 1:1000, probability of collision with uav is perhaps something like 1:10 000 000.

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Permalink Reply by Jonathan T. Watters on July 13, 2012 at 11:21pm

Someone needs to develop a cheap radar or transponder system for sUAS.

The MIT DIY Radar was interesting but probably too big for most small drones.  

I think a transponder system would be best.  Anyone know of something like that in development?  

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Permalink Reply by Jake Stew on July 15, 2012 at 2:27pm

It's called ADSB.  Most commercial planes will be required to carry it by 2020, but that deadline has already been pushed back a couple times.  That's a shame because it's a simple, fairly low-cost system and planes are already required to carry transponders anyways.

ADSB is essentially a regular transponder interfaced to a GPS.  Instead of just supplying your FCC identifier it also puts out your location, altitude, speed, and heading.  It essentially creates a virtual radar network where the locations, heading, speed, etc. of all planes are known.

Right now you can order an ADSB receiver for under $100.  You could feed the data from that unit into your GCS and use it manually to avoid collisions.  With a little software development it would be easy to do this automatically.

I've been saying for awhile now that someone should be working on this to get a working system going.  Then when the rules are made they would be written around a working system.  If the rules get written first based on the existing expensive and impracticable systems it will be very hard to get them changed later.

Right now planes are required to use an approved system designed for planes.  These systems are too large and heavy for a UAV, and they consume way too much power.  They're also very expensive.

I propose a system using a simple receiver at the ground station or mounted in the plane.  This would provide the ADSB-IN.  The ADSB-OUT could be provided by a ground transponder or input through the internet via cell phone or other internet access.   This would allow for a ground transponder to replace the onboard gear or eliminate it altogether.

ADSB works by sending out the data on the transponder signal.  ATC and ground stations receive this and rebroadcast the data.  So you can detect the signals directly from the other planes and/or the ATC/ground station.  They are already linked by the internet.

Since we already have the GPS data we should be able to inject this into the internet system already without needing to broadcast it through an expensive transmitter that will eat into the already crowded ADSB bandwidth.

Check out:

http://microadsb.com

http://www.coaa.co.uk/planeplotter.htm

http://www.youtube.com/watch?v=qPeAPD3dG_U

The technology is already out there.  All that's needed is the desire to create a modern system.  I wish people would just see the inevitable and try to get there ASAP.  It would solve so many problems in the world.

The future is a distributed system that tracks everything in the air and automatically avoids collisions.  Radar won't be needed, and air traffic controllers will be reduced by a huge factor.  You won't have to file flight plans because everything will be done real-time.

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Permalink Reply by Stephen R Mann on November 2, 2012 at 11:27am

I propose a system using a simple receiver at the ground station or mounted in the plane.  This would provide the ADSB-IN.  The ADSB-OUT could be provided by a ground transponder or input through the internet via cell phone or other internet access.   This would allow for a ground transponder to replace the onboard gear or eliminate it altogether.

Jake - are you still following this?  I can see where a ground-based ADSB-OUT may satisfy the FAA for "see and avoid" in the near future.  This would be a good answer if the receiving ADSB system were alerted to model aircraft within 3-miles and below 3000 ft".  No need for an exact position from the UAV's GPS.  As I private pilot I rarely fly below 3000 ft anyway (well, at least twice on each flight) and our UAV's are not likely to be more than 3-miles from our base station.

If someone wanted to build and fly a UAV beyond the 3000-ft x 3-mile core around the base station, then they can include an on-board ADSB and be in contact with ATC.  (Maybe a repeater on the aircraft??).

 

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Permalink Reply by Andres Pineda on January 8, 2013 at 1:00am

Hi Jake,

I am new to this but very interested in how this might work. I get the part about the ADS-B receiver being used to be aware of nearby aircraft. A Ground Station could have the receiver and be aware of air traffic and somehow be used to avoid straying into that airspace by the UAV.

However, I am still a little fuzzy on your proposal to transmit the UAV location in ADS-B format so that other aircraft could be aware of the UAV flight location. I believe you are saying that the ADS-B transmitter would be too costly/heavy for a UAV, but if the Ground Station - which is aware of the UAV and its GPS position could send the live data via the Internet, it would somehow get integrated/repeated by more powerful transmitters. Is that correct? 

Is there already a means of providing flight data via the Internet to Air Traffic Control or would this be a new type of communication that is yet to be developed? Any links to others that are doing/trying to send position data to repeaters via the Internet that would be appreciated.

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Permalink Reply by Andres Pineda on January 8, 2013 at 1:36am

More questions that came up as I got to thinking about this:

1. I  presume that the UAV/Pilot would have to get some sort of registration/identification (FCC ID) would it not? That would be required to uniquely identify the UAV with contact information.

2. How could you prevent a malicious person from "flooding" bogus flight data to cause confusion in the air space? I imagine that could be done with a fake transmitter already, but just a thought as a barrier to getting this idea playable. Maybe requiring secure authentication of some sort. Is there an FAA document that specifies what is required to legally transmit ADS-B data somewhere?

3. If the UAV stays below 3,000ft or so, would this really be necessary to coordinate with commercial flights? I can see it being more of an issue in a park or common fly area to coordinate amongst the UAV pilots. 

Just some thoughts.

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Permalink Reply by Stephen R Mann on January 8, 2013 at 11:12am

ADS-B Out adds the aircraft position to the data stream from the transponder that the ATC radar picks up.  I think we're not going to see any lightweight transponders any time soon, and the FAA is very unlikely to adopt any ATC function through the internet.  The risks of introducing bogus data into the system is simply too great.

The only way you will get FAA ID (AKA the N number) is with a certified or experimental aircraft certificate, and the FAA simply has no rules for either regarding light UAV's.  And getting any aircraft certified is a very expensive proposition.

The only way you could possibly get the FAA to cooperate is to ask for a "block" clearance, like what is used for parachuting, unmanned balloon or rocket flights.  Basically, you communicate with ATC, usually by phone, and request a block clearance for a specific location and altitude and time window.  If approved, the FAA keeps controlled aircraft out of that block for the specified time.  But since this is for specific purposes at a specific time, you aren't likely to get it for an ad-hoc UAV flight.

Further, flight between 500 ft and 3000 ft would likely not be allowed because this is the area (particularly 2000- to 3000 ft) that General Aviation aircraft frequent.  Realize also that GA aircraft outnumber commercial aircraft by ten to one.  For the most part, GA aircraft are not being controlled by ATC, (ATC only controls aircraft flying on IFR flight plans) thus invisible to them, unless they are specifically looking for skin reflections, which they don't normally do because of a lot of ground clutter.  GA aircraft cannot go below 500 ft except for takeoff and landings, which is why the seemingly arbitrary ceiling of 400 ft was stated in Advisory Circular 91-57.  (Certified aircraft altimeters are only accurate within 50 ft, so if my Cessna's altimeter says 500 ft, I could actually be at 450 ft and still legal).

Our best shot of getting permission, or a general waiver from the prohibition of commercial use of light UAV's will be to push for an update to AC91-57 that would permit flight for compensation for aerial photography that would otherwise comply with AC91-57.

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