# Do Passenger Planes Have Radar?



## caravanman (May 22, 2019)

Just wondering if aircraft have any radar that allows them to be aware of other planes nearby, or do they all rely on visuals and information and instructions to be sent from the ground station ATC?

Ed.


----------



## Trogdor (May 22, 2019)

They have something called TCAS - Traffic Collision Avoidance System.

https://en.m.wikipedia.org/wiki/Traffic_collision_avoidance_system


----------



## PVD (May 22, 2019)

They have radar for weather, tcas for collision avoidance.


----------



## Devil's Advocate (May 22, 2019)

caravanman said:


> Just wondering if aircraft have any radar that allows them to be aware of other planes nearby, or do they all rely on visuals and information and instructions to be sent from the ground station ATC? Ed.



Visual monitoring and avoidance methods are woefully insufficient for modern commercial operations. There are simply too many flights for the old see and be seen rules. Modern aircraft can monitor each other's speed, altitude, and location by way of radio transponders. TCAS uses this information to provide first action emergency avoidance instructions when a series of errors or oversights (instructional, operational, or mechanical) create a predictable risk of collision.


----------



## B757Guy (May 22, 2019)

Yes, they do. The Boeing 777 I fly has both radar to alert us to nearby traffic, along with weather and terrain. As someone else pointed out the traffic piece is called TCAS. I also have a very similar system for weather and traffic in my personal airplane that I own. Both systems work very well.

Happy to answer any technical questions if you have them.


----------



## saxman (May 22, 2019)

TCAS allows the aircraft transponders to talk to each other. While you can see other aircraft on the map display as small diamonds, squares, and circles, you can't really use that to avoid them. It's just to have a mental picture of what's going on around you. ATC can see them all too, so it's not too much of a concern. If there is a conflict the TCAS system will tell us to "climb," "descend," or "monitor vertical speed" It will paint a green and red arc on the attitude indicator or vertical speed indicator and we pretty much kick off the autopilot and climb or descend to the green area. It gives plenty of notice so the maneuver is actually pretty smooth and no one would think anything of it.


----------



## Bob Dylan (May 22, 2019)

Good info from Professional Pilots!


----------



## chakk (May 23, 2019)

However, small airlanes, such as the floatplanes that collided in Alaska, probably do not have TCAS. For them, it's see and be seen or hope that an observent air traffic controller on the groind paints you on his radar scope and provides verbal alerts of conflicting traffic.


----------



## AutoTrDvr (May 23, 2019)

chakk said:


> However, small airlanes, such as the floatplanes that collided in Alaska, probably do not have TCAS. For them, it's see and be seen or hope that an observent air traffic controller on the groind paints you on his radar scope and provides verbal alerts of conflicting traffic.



The Alaskan private pilots also do "broadcasts" on the standard Unicom frequencies so that those local to each other know where they are, both in relation to each other and to geographic landmarks. Or, they used to.... maybe they have newer technology now but, that's what they were doing in 1999 when I last visited there and took some "tour" rides around Denali etc.


----------



## Devil's Advocate (May 23, 2019)

chakk said:


> However, small airlanes, such as the floatplanes that collided in Alaska, probably do not have TCAS. For them, it's see and be seen or hope that an observent air traffic controller on the groind paints you on his radar scope and provides verbal alerts of conflicting traffic.



Unless I'm mistaken ADS-B (out) should be required for most traffic operating in and around US airspace by 2020. This is not the same as TCAS, but it should be enough to alert other TCAS equipped aircraft of potentially disruptive traffic around them. Unfortunately this mandate alone would not be enough to prevent a collision between two small aircraft operating with minimum required equipment. There is a form of TCAS "lite" that is designed to operate in conjunction with ADS-B for small aircraft but there is no mandate for such equipment and I have no idea how common or practical it is for something like a small sea plane.


----------



## jis (May 23, 2019)

I would recommend the Wikipedia article on TCAS that Trogdor provided a reference to earlier in this thread (I provide a reference again - it is that good [emoji4] ). It is quite informative, and even discusses the relationship between TCAS and ADS-B and how those two are used together and how they may be integrated in the future.

https://en.wikipedia.org/wiki/Traffic_collision_avoidance_system



AutoTrDvr said:


> The Alaskan private pilots also do "broadcasts" on the standard Unicom frequencies so that those local to each other know where they are, both in relation to each other and to geographic landmarks. Or, they used to.... maybe they have newer technology now but, that's what they were doing in 1999 when I last visited there and took some "tour" rides around Denali etc.



I suspect that the floatplanes do not fly these missions in controlled air space, so I suspect no ATC is involved. I also suspect that they probably do not have TCAS since they are probably not "commercial turbine-powered transport aircraft with more than 30 passenger seats (or MTOM above 33,000 lb or 15,000 kg)", so they are not required to. But they could choose to have them regardless, since they are not prohibited from having them either.


----------



## AutoTrDvr (May 23, 2019)

jis said:


> I suspect that the floatplans do not fly these missions in controlled air space, so I suspect no ATC is involved. I also suspect that they probably do not have TCAS since they are probably not "commercial turbine-powered transport aircraft with more than 30 passenger seats (or MTOM above 33,000 lb or 15,000 kg)", so they are not required to. But they could choose to have them regardless, since they are not prohibited from having them either.



Not all were "float planes." The two I took on "tourist" flights were land based and out of small airports, probably on Unicom frequencies. Again, they were small Cessna type aircraft (6 seaters), so I would agree that they probably did not have TCAS. And, neither flew above 10,000 ft, although one came close to it, flying to within 1000 yards of Denali's south peak, about half way up. But, every 5 minutes or so, the pilot would make a broadcast announcement on the frequency he was on, indicating where he was and what he was doing. I also heard similar broadcast transmissions from other pilots, doing the same.


----------



## Asher (May 24, 2019)

I don't know what the issue is. One of the outfits that lost one of the floatplanes at Ketchikan last week, lost another one on Wednesday, I believe. Don't know what the problem was, it was upside down attached to a rescue vessel. Fatalities. I don't want to throw stones and these guys may be the best of the best, The airlines are sucking up a lot of low time pilots, I don't know how qualified some of these charter pilots are.


----------



## caravanman (May 25, 2019)

Thanks for all the replies, good to know that the TCAS system exists.
I was wondering how "it decides" to advise one plane to climb, and the other to descend, or one to turn right or left in a potential collision situation. Hope there is no electronic roulette wheel in the decision making process? 

Ed.


----------



## saxman (Jun 1, 2019)

caravanman said:


> Thanks for all the replies, good to know that the TCAS system exists.
> I was wondering how "it decides" to advise one plane to climb, and the other to descend, or one to turn right or left in a potential collision situation. Hope there is no electronic roulette wheel in the decision making process?
> 
> Ed.



The TCAS does indeed talk to each other so they don't give conflicting commands. They only give vertical commands too, no turning.


----------

