See and Avoid

[Bartman]

I thought I'd start this conversation with you guys because it's a very common term in full scale aviation and as the FAA (and other world aviation regulatory authorities) continue to integrate UAS and sUAS operations into their nations' airspace systems, you will increasingly hear the term "See and Avoid" mentioned.

"See and Avoid" refers to a pilot's responsibility/ability to maintain a visual scan of the area around his/her aircraft in order to see and avoid other aircraft. If every pilot is doing his/her job to "see and avoid" other aircraft then, in a perfect world, there wouldn't be any midair collisions between aircraft flying under "Visual Flight Rules". Visual Flight Rules, or VFR, refers to day or night flight operations where cloud conditions and inflight visibilities are good enough where pilots are responsible for their own navigation and collision avoidance. Even when pilots are on more formal "Instrument Flight Plans" where air traffic control largely manages their route and traffic avoidance, when clear of clouds pilots are still responsible for maintaining a constant watch for other aircraft with "See and Avoid" regarded as the last defense against midair accidents.

"See and Avoid" also makes an assumption about the other aircraft that you'll be looking for, it assumes that they are out there and available to be seen. As @SleepyC; mentioned in another thread, Ultralight aircraft in the US have some pretty liberal operating rules in that the pilots are barely trained and aren't officially licensed as Ultralight Pilots. Yet they don't have any of the restrictions that we are seeing being discussed for sUAS (should I just capitulate and start calling them drones? It would probably get us more traffic via Google!).

There are a variety of reasons why Ultralights aren't in a fight for their life as sUAS are but I'll mention three;

• they aren't being delivered to virgin users by the thousands
• they are large enough (and often colorful enough) for other full-scale pilots to "see and avoid" them
• most importantly, pilots of ultralight aircraft can move their heads around to scan their surrounding area in order to avoid other aircraft.

"See and Avoid" is our biggest weakness at the moment because a pilot flying beyond line-of-sight can't look around to "see and avoid" other aircraft and sUAS, by their definition, are small and nearly impossible for other pilots to see from any distance which would allow them time to avoid an inflight collision.

Another topic related to this is call TCAS, which you will also begin to hear a lot more about as regulations get closer. TCAS stands for Traffic Collision Avoidance System and it was mentioned in the House hearing on Dec. 10 regarding sUAS integration in the US. TCAS systems enable pilots to see other aircraft (provided they have a compatible transponder blipping away their position information) as a blip on a small cockpit display. More advanced versions also display altitude information and can provide collision avoidance directions when a collision is imminent ("Descend!"...."Turn right!"... followed (hopefully!) by "Clear of Conflict").

TCAS systems used to be big and heavy and their antennae large. In the last fifteen years or so we've seen units that can provide basic information and take up no more room than a pack of cigarettes on the panel brow. Technology is rapidly advancing and we may soon see a TCAS unit that can reside on our sUAS vehicles without killing endurance or useful load (an aircraft term referring to weight (fuel, pax, baggage, etc.) that can be carried in addition to the weight of the aircraft itself). This would be a huge step towards helping regulators to chill out as it would help resolve the inherent inability of sUAS pilots that operate beyond Line-Of-Sight to see and avoid aircraft operating in their area.

More advanced TCAS systems for sUAS that can integrate with air traffic control and that can communicate with their users back on the ground via telemetry will likely remove a major bottleneck in the process of integration. Until then, we need to understand and respect the concept of "See and Avoid" as it relates to full-scale aircraft operations and how it works against us as we fight for the right to operate sUAS within line-of-sight and beyond.

Hope that helps.
Bart

 

[Old Man]

I don't know if you are aware of this, but UAV's of many different sizes have been integrated with full scale aviation at overseas military air fields for some time now. So far only the full scale have been equipped with TCAS while the UAV's, all the way down to the Scan Eagle, have been equipped with Mode C altitude encoding transponders. There are some new transponders I can't discuss but the principle of mixing UAV's with manned in air traffic densities greater than Atlanta, LAX, or O'Hare has been working well. There have been some conflicts but in every case the fault has been with the human piloted machine.

Our real problem comes in 2020 with ADS-b and ADA-a, which are mandatory for all of aviation and augment/replace the collision avoidance system. The cost at this time doesn't get much lower than $5,000 for only the transmitting side. If you want both just add money. Then we have size and power issues. ADS-b is power hungry. DS equipment at relatively small scales, and those are still larger than what we can fit or carry. There is talk that some small scale technology may be handled through some off shore makers but that has not been finalized yet.

Oh, some years ago I darn near flew through some moron flying an ultralight at 9500' over the mountains east of Santa Barbara. Didn't see that thing until I was only about a mile away. It was up sun at 12:00.

 

[scotth]

Please explain 'see and avoid' to the multitudes of Cirrus drivers out there. They are a far greater hazard than anything else in the air. Heads down, pushing buttons...

 

[Bartman]

that problem goes all the way up to the major airlines.....two pilots, heads down, pushing buttons.....just did a sim session for my day job and we discussed it in our pre-briefing

@Old Man; TCAS systems are getting smaller and more competent but like I said, sUAS won't see much of a benefit until they can decrease size/weight and power consumption while also creating a user interface that let's us be in the loop from where we stand on the ground while the FC is autonomously obeying conflict-resolution commands.

passive TCAS will likely happen sooner where sUAS will just blip away giving position and altitude so others can avoid us...i'd guess that that will be the first threshold we will be able to meet.

 

[Old Man]

passive TCAS will likely happen sooner where sUAS will just blip away giving position and altitude so others can avoid us...i'd guess that that will be the first threshold we will be able to meet.

Passive TCAS has already happened through the use of Mode C transponders used for small UAV's mixing it up with TCAS equipped full scale military or civilian aircraft operating in the same environment. The "bus drivers" get all excited whenever their systems lite off because of sUAS proximity. Most of them are too dense to understand how a pre-programmed, GPS guided sUAS can operate the same way they do after they set their auto pilots. A few have refused to proceed until the UAV is clear of the airspace, like the entire ATA, yet they continue on with a dearth of attack and transport helis violating just about all the height and location restrictions they were given. Go figure.

 

[Bartman]

well, regardless of the current status of TCAS and its derivatives, See and Avoid is the concept that will be mentioned more and more as the regulatory climate heats up in the coming months.

See and Avoid, as a community we've got to come to terms with just how important the concept is to manned aircraft and the FAA's oversight of those operations. From there we can try to figure out a way to coexist so as to not be seen as a threat.

 

[Old Man]

I agree. That is the one aspect of how we fly that has been a sticking point for our aircraft in the NAS. Manned aviation has the right of way no matter what (rightly so) and to have an event because we did not have the ability to see.detect them will be both criminal and a tragedy. There will always be that Pacer or Cub with no electrical system to drive fancy electronics running low somewhere. I can say for a fact that manned aviation is scared to death of the thought of unmanned aircraft be-boppin' around their airspace.

 

[eskil23]

Regarding the problem that sUAS are too small to be "seen and avoided" in proper time by commercial air traffic; are there any aviation transponders available for sUAS?

 

[mlebret]

There is a system used by gliders (mandatory in France), low cost, named FLARM http://www.flarm.com/index_en.html

Last month they did an experiment with a small UAV (less than 1kg) with a Tx only version.http://www.aerobuzz.fr/spip.php?article5486

Marc

 

[Bartman]

Last month they did an experiment with a small UAV (less than 1kg) with a Tx only version.http://www.aerobuzz.fr/spip.php?article5486

Thanks for posting that! Here's the text of the original French article in English via Google translate;


https://translate.google.com.sg/tra...zz.fr/spip.php?article5486&edit-text=&act=url

 

[Bartman]

by sheer coincidence, "See and Avoid" was mentioned in a Washington Post article at about the same time last night that I was typing and posting this thread.

http://www.washingtonpost.com/world...d8a07a-86c2-11e4-a702-fa31ff4ae98e_story.html

A fundamental principle of aviation safety is that pilots must be able to see and avoid other planes and objects in the sky — something that drones cannot do. Drones are equipped with cameras that have a limited field of vision. Researchers are working on substitute technologies, but solutions are years away.

 

[econfly]

Good stuff here.

I don't want to throw anybody under the bus, but there is a big difference between FPV flying above a few hundred feet and in public space and line-of-sight flying over private land under 400'. I can't see why some guy flying his phantom over his own property under 400' needs to be regulated at all. There is zero need for any manned aircraft to be in that space, and any exceptions are going to be well known to the land owner anyway (e.g., agricultural land being sprayed from the air). Simply put, private land and line of sight flying under 400' (which would capture a huge amount of hobby and even commercial use) is a category that could be both regulatory-free and extremely safe. Where the conflict arrives is in flying over public space or at altitudes in legitimate use by manned aircraft. That is a real issue that deserves attention. My frustration in all of this is having these very different types of flying conflated into one regulatory framework.

 

[eskil23]

I think that it is quite common with power-line inspection by helicopter below 400 feet. I don't know if the power companies care to notify landowners about such inspections.

 

[econfly]

I think that it is quite common with power-line inspection by helicopter below 400 feet without notification to landowners.

I can understand inspection of lines where an easement exists, in which case the easement holder and land owner must cooperate. Simple enough.

My point is that we have have a huge amount of flying -- both hobby and commercial (real estate photos, etc.) -- taking place under a very low ceiling and over private land. Why does that need any regulation at all?

Urban flying is, almost by definition, taking place over public space or over land owned by someone else. Flying at higher altitudes has clear potential for conflict with manned aircraft. Flying near airports obviously needs to be regulated. But for the vast majority of hobby and commercial use (of multirotors in particular) we just don't have the potential for conflict. I'm on 240 acres of farm land in the middle of America. Regulating me over my own land under a few hundred feet is just silly.

 

[Bartman]

i don't disagree Rob but knowing the rules of the road that manned aircraft are abiding by will help us to find ways to frame our concerns so that we can maybe keep doing what we're doing.

there has to be a way for everyone to be able to coexist safely.

 

[econfly]

i don't disagree Rob but knowing the rules of the road that manned aircraft are abiding by will help us to find ways to frame our concerns so that we can maybe keep doing what we're doing.

there has to be a way for everyone to be able to coexist safely.

Sure, we need to understand this stuff -- absolutely.

From my (perhaps extreme) view, part of the problem seems to be the assumption that every inch of airspace is necessarily in use (or potentially in use) by manned aircraft. Something has to give here or we are going to lose. I don't have any expertise in this area, but if there isn't a floor for manned aircraft flight over private land then that needs to change. It shouldn't be my problem to see and avoid some guy in a little airplane flying 250 feet over my farm. He shouldn't be there in the first place.

 

[Bartman]

a guy in a little airplane shouldn't be flying over at 250 ft unless he's in trouble and trying to land there. over unpopulated areas airplanes have a 500' minimum altitude to maintain.

helicopters, on the other hand, have all sorts of low altitude airways they can use and I don't think that there is an altitude minimum for them. medivac flights especially are the big hazard at really low altitudes as are other heli flights that might be transiting the area when the clouds are too low for them to be flying any higher.

maybe heli's should have to fly above 500 ft also when the clouds are at least 800 or 1000 ft above ground level and when the clouds are lower than that manned heli's can fly lower but sUAVs will be appropriately restricted??

 

[econfly]

Interesting. Having your expertise here is a huge help. I know for sure that I've seen small planes under 500' -- which just goes to show that rules get broken. The helicopter issue is interesting. My preference would be to tell them to get up over 500' or stay on the ground. I can see medivac as a source of unavoidable conflict, however I wonder if there exists any set of rules that can address that apart from grounding RC flight completely.

 

[Av8Chuck]

This is a non issue. For most the floor of the NAS is 500' if sUAS is restricted below 400' where's the conflict? The odds of a helicopter and multi rotor running into each other is very low. Just because some buroecrate throws around buzz words like "see and avoid" doesn't mean that sUAS should be required to comply with it.

 

[Bartman]

Interesting. Having your expertise here is a huge help. I know for sure that I've seen small planes under 500' -- which just goes to show that rules get broken. The helicopter issue is interesting. My preference would be to tell them to get up over 500' or stay on the ground. I can see medivac as a source of unavoidable conflict, however I wonder if there exists any set of rules that can address that apart from grounding RC flight completely.

@econfly;

In the House hearing on Dec 10 House members also kept stressing a "risk based" approach for the FAA where areas with the least risk also be given the most leeway to proceed forward. A farm like yours, located where it is, would be on the low side of the risk spectrum giving you more freedom to do your thing. When you're back in CT though, it's an entirely different story both in terms of how busy the airspace is and how many sUAS may be employed for different things as activity continues to increase into the future.