Max777geek
Topic Author
Posts: 159
Joined: Wed Mar 07, 2007 6:20 pm

ASD Vs Tcas

Mon Nov 09, 2009 9:03 am

hello chaps

I saw on NatGeo the episode of "AirCrash Investigations" (Funny : in italian the title becomes : "high altitude investigations" without crashes) the introducing of the ASD which at a first sight does not less not more than what is commonly known as TCAS : it gives altitude variations and directions on pfd, as long as I noticed. I didn't see it all tough.

Is there any deeper difference ? Is that already installed and working ?

Thanks in advance.
 
mandala499
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Joined: Wed Aug 29, 2001 8:47 pm

RE: ASD Vs Tcas

Mon Nov 09, 2009 5:11 pm

ASD or ADS???

Sorry, my guessing brain isn't working well today...

If it's ADS, go and have look at ADS-B...
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
Fly2HMO
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RE: ASD Vs Tcas

Mon Nov 09, 2009 5:34 pm

I'm assuming the OP is talking about ADS-B.

http://en.wikipedia.org/wiki/Automat...c_dependent_surveillance-broadcast

I was one of the first people worldwide to use this system. It's an amazing system, but yes at the moment it is does not have the same capabilities as TCAS, but it will in the near future.
 
bri2k1
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Joined: Sun Dec 19, 2004 4:13 am

RE: ASD Vs Tcas

Mon Nov 09, 2009 9:34 pm

The Wikipedia article, like so many others, lacks some fundamentals. It lists a host of "benefits," but does not explicitly describe to what the benefits are in comparison. The reader can probably infer the benefits of ADS-B are being described as versus SSR.

Many airliners can interrogate transponders of other aircraft to generate TCAS data, but most small airplanes can't. This means a lot of airplanes can be flying close to each other and still won't appear on TCAS unless they happen to pick up a reply to someone else interrogating their transponder. This can create a significant "blind spot" for TCAS systems in both aircraft sizes, especially in congested airspace like the vicinity of airports. There's a huge gap in the accuracy of the responses, too -- the encoding altimeter being calibrated to standard pressure at sea level, for example, and the sensitivity of the receiving antenna to SSR replies. ADS-B transmits absolute GPS location data, in three dimensions, not the relative "bearing-and-range" combined with only moderately accurate altitude information given in SSR.

Living in Colorado, I routinely fly in mountainous areas that will never be covered very well by radar. ADS-B is already in operation at several Colorado mountain airports like EGE, and although I haven't flown an aircraft with an ADS-B installation yet, I am hearing positive reviews from both pilots and controllers in the area.
Position and hold
 
Fly2HMO
Posts: 7207
Joined: Sat Jan 24, 2004 12:14 pm

RE: ASD Vs Tcas

Tue Nov 10, 2009 12:32 am



Quoting Bri2k1 (Reply 3):
Many airliners can interrogate transponders of other aircraft to generate TCAS data

To further expand on this, mode A , C and S aircraft are visible to TCAS equipped planes. But resolution advisories can only be provided for mode C and S targets. GA planes, in lieu of ADS-B, may have TIS-B, which is an uplink from the radar for a given area (ie PHX approach) so you're basically seeing what a controller sees, with the same drawbacks (slow update rates, greater inaccuracy than ADS-B, etc)

Having flown aircraft equipped with both ADS-B and TIS-B I can attest to the enormously increased traffic situational awareness this system provides.
 
Max777geek
Topic Author
Posts: 159
Joined: Wed Mar 07, 2007 6:20 pm

RE: ASD Vs Tcas

Tue Nov 10, 2009 9:36 am

Thanks for all of your answers.

Fly2hmo : what do you mean ?

Tcas offers traffic patterns, what's ads supposed to give more ?

I.e. : graphic flight plans of traffic in sight ? that would be more,
but I don't see any factor that can't be retrieved from tcas, as
a matter of facts.

The only way to retrieve more informations such as more detail
in the prediction of traffic navigation is if the new system will
comunicate more data, like portions of the incoming flightplan,
next waypoints, crossing altitudes, speeds, which I guess
will need a bit of automation to be handled, like you know
in a cockpit you read somewhere that your traffic in sight
what will do next so you can take appropriate actions,
and / or the autopilot will suggest himself alternative
routes in order to avoid proximity etc.
 
bri2k1
Posts: 952
Joined: Sun Dec 19, 2004 4:13 am

RE: ASD Vs Tcas

Tue Nov 10, 2009 10:23 pm



Quoting Max777geek (Reply 5):
Tcas offers traffic patterns, what's ads supposed to give more ?

Let me try to describe more generally what kind of information is offered on these displays. Both TCAS and ADS-B offer, to the pilots of other aircraft in the vicinity, the approximate location of and distance to traffic that might pose a hazard. TCAS is better than nothing, but has significant drawbacks. ADS-B provides much more accurate position information about nearby traffic, provided that traffic is using ADS-B.

Flight plans have nothing to do with traffic avoidance. A flight plan is a suggestion, and the actual route flown may have little or nothing to do with the flight plan, save the origin airport. In Class A airspace, that is above 18,000ft MSL in the USA, all traffic is in contact with ATC and being provided separation services, so it becomes less of a concern. The primary collision hazards occur when climbing or descending (due to reduced visibility) and around airports and common navigation points like VORs (due to the increased density of traffic). There may be a mix of IFR and VFR traffic, some which will not be in contact with ATC, and many which may not have filed a flight plan at all.

Every pilot is responsible to see and avoid other aircraft, whether flying IFR or VFR. TCAS, ADS-B, and radar advisories from ATC are all just useful tools to assist pilots in avoiding each other. Again, the big improvement with ADS-B will be more accurate position information about other aircraft, but it's not even close to being used widely at this time.

There is a feature in ADS-B whereby some aircraft will be able to provide both a present position and a position vector, that is, the direction in which they are flying. But for me, the truth is that when I get within a certain distance of another aircraft, it doesn't matter which direction it was going at a certain time. I should maneuver to avoid the other aircraft irrespective of which direction it might go.
Position and hold

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