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#1
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TCAS and slow moving/stationary targets?
Hi,
Quick google search on "TCAS filter slow" and similar didn't get me what I wanted, so here goes... Do TCAS systems filter out targets which have slow/no ground speed? Reason for asking... I got into wave yesterday, and while climbing through 11,000 MSL NW of Allentown PA had an American Airlines CRJ pass nearby. I would guesstimate that he was about 500 above and a half mile horizontal. It wasn't really close - I had him in sight for over a minute and was edging away laterally to gain separation. But, it was a little closer than the published TA/RA numbers I've seen in manuals. I was essentially stationary for 20 minutes. By comparison, later in the flight I watch an A300 make a sweeping turn around me at 9,000 as I crossed a well-published STAR. I also checked in with Allentown approach, and they painted me just fine on their ground radar. Curious... P3 |
#2
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TCAS and slow moving/stationary targets?
On Apr 4, 4:47*pm, Papa3 wrote:
Hi, Quick google search on "TCAS filter slow" and similar didn't get me what I wanted, so here goes... *Do TCAS systems filter out targets which have slow/no ground speed? Reason for asking... *I got into wave yesterday, and while climbing through 11,000 MSL NW of Allentown PA had an American Airlines CRJ pass nearby. * I would guesstimate that he was about 500 above and a half mile horizontal. * It wasn't really close - I had him in sight for over a minute and was edging away laterally to gain separation. But, it was a little closer than the published TA/RA numbers I've seen in manuals. * * I was essentially stationary for 20 minutes. By comparison, later in the flight I watch an A300 make a sweeping turn around me at 9,000 as I crossed a well-published STAR. * I also checked in with Allentown approach, and they painted me just fine on their ground radar. Curious... P3 Approach painted you well? As in they could see your transponder return? TCAS needs you to have a transponder for it to work. If approach could only see your skin paint raw radar return, TCAS would not work, and if you had near zero GS in wave, then the approach radar would have filtered you out during that time frame. T |
#3
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TCAS and slow moving/stationary targets?
On Apr 4, 4:47*pm, Papa3 wrote:
Hi, Quick google search on "TCAS filter slow" and similar didn't get me what I wanted, so here goes... *Do TCAS systems filter out targets which have slow/no ground speed? Reason for asking... *I got into wave yesterday, and while climbing through 11,000 MSL NW of Allentown PA had an American Airlines CRJ pass nearby. * I would guesstimate that he was about 500 above and a half mile horizontal. * It wasn't really close - I had him in sight for over a minute and was edging away laterally to gain separation. But, it was a little closer than the published TA/RA numbers I've seen in manuals. * * I was essentially stationary for 20 minutes. By comparison, later in the flight I watch an A300 make a sweeping turn around me at 9,000 as I crossed a well-published STAR. * I also checked in with Allentown approach, and they painted me just fine on their ground radar. Curious... P3 No TCAS I or II do not velocity filter on ground speed. This would be bad as its foreseeable light aircraft might well have near zero ground speed. And one reason TCAS got mandated is because light aircraft have taken down airliners. This is an old wives tale that I've heard before. The relative speed (not ground speed) between the threat aircraft and TCAS equipped aircraft is used to calculate time to collision/proximity parameters that drive the systems overall TA and RA behavior. At least one reason this old-wives tale exists seems to be a belief that aircraft on the ground do not trigger a TA/RA from nearby airborne aircraft and this must be because there us ground speed filtering. That's just wrong. TCAS II (the CRJ will have TCAS II) will have very good altitude data on you and slightly fuzzy direction data. But its still using that to projected paths to calculate collision risks if he is not actually pointed your way with a chance of a collision it should have very low chance of generating an RA. If your transponder was on and working and squawking an accurate altitude they may have seen you on their panel (and hopefully got you visual) or even have had a TA and not needed to take any action. Darryl |
#4
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TCAS and slow moving/stationary targets?
Darryl, are you calling Erik an old wife?
Jim :-) :-) :-) not three trailers, but I still own the little one |
#5
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TCAS and slow moving/stationary targets?
On Apr 4, 9:02*pm, T wrote:
On Apr 4, 4:47*pm, Papa3 wrote: Hi, Quick google search on "TCAS filter slow" and similar didn't get me what I wanted, so here goes... *Do TCAS systems filter out targets which have slow/no ground speed? Reason for asking... *I got into wave yesterday, and while climbing through 11,000 MSL NW of Allentown PA had an American Airlines CRJ pass nearby. * I would guesstimate that he was about 500 above and a half mile horizontal. * It wasn't really close - I had him in sight for over a minute and was edging away laterally to gain separation. But, it was a little closer than the published TA/RA numbers I've seen in manuals. * * I was essentially stationary for 20 minutes. By comparison, later in the flight I watch an A300 make a sweeping turn around me at 9,000 as I crossed a well-published STAR. * I also checked in with Allentown approach, and they painted me just fine on their ground radar. Curious... P3 Approach painted you well? As in they could see your transponder return? TCAS needs you to have a transponder for it to work. If approach could only see your skin paint raw radar return, TCAS would not work, and if you had near zero GS in wave, then the approach radar would have filtered you out during that time frame. T- Hide quoted text - - Show quoted text - Transponder squawking 1201. Earlier in the flight checked in with Allentown who were able to verify my location after asking me to ident. This was when I was buzzing along quite nicely at about 100 kts. Per Darryl's subsequent post, it's very possible that the geometry worked out and there was no need for maneuvering. It wasn't uncomfortably close in the sense I wasn't concerned that paths were converging. P3 |
#6
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TCAS and slow moving/stationary targets?
On Apr 4, 10:02*pm, Papa3 wrote:
On Apr 4, 9:02*pm, T wrote: On Apr 4, 4:47*pm, Papa3 wrote: Hi, Quick google search on "TCAS filter slow" and similar didn't get me what I wanted, so here goes... *Do TCAS systems filter out targets which have slow/no ground speed? Reason for asking... *I got into wave yesterday, and while climbing through 11,000 MSL NW of Allentown PA had an American Airlines CRJ pass nearby. * I would guesstimate that he was about 500 above and a half mile horizontal. * It wasn't really close - I had him in sight for over a minute and was edging away laterally to gain separation. But, it was a little closer than the published TA/RA numbers I've seen in manuals. * * I was essentially stationary for 20 minutes. By comparison, later in the flight I watch an A300 make a sweeping turn around me at 9,000 as I crossed a well-published STAR. * I also checked in with Allentown approach, and they painted me just fine on their ground radar. Curious... P3 Approach painted you well? As in they could see your transponder return? TCAS needs you to have a transponder for it to work. If approach could only see your skin paint raw radar return, TCAS would not work, and if you had near zero GS in wave, then the approach radar would have filtered you out during that time frame. T- Hide quoted text - - Show quoted text - Transponder squawking 1201. * Earlier in the flight checked in with Allentown who were able to verify my location after asking me to ident. * This was when I was buzzing along quite nicely at about 100 kts. Per Darryl's subsequent post, it's very possible that the geometry worked out and there was no need for maneuvering. * It wasn't uncomfortably close in the sense I wasn't concerned that paths were converging. P3 Any maneuvering could always be at ATCs request. However if things go bad and it gets to an RA (resolution advisory) - the RA are only climb or descent (or vary rate) instructions so you expect to see things happen vertically but of course it can be hard to see/tell what is going on. It is nice if you can monitor the ATC frequency(s) in use so you can hear ATC directing traffic around you. Thank you to Erik for using a transponder near traffic areas like this. And working to understand what might be going on. Darryl |
#7
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TCAS and slow moving/stationary targets?
On Apr 4, 9:17*pm, JS wrote:
Darryl, are you calling Erik an old wife? Jim :-) *:-) *:-) not three trailers, but I still own the little one Jim Jeez I've lost track of how many trailers and gliders you own and on what continents. "the little one" does not help, you had an ASH-25 -- most other gliders are "little"... Darryl |
#8
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TCAS and slow moving/stationary targets?
On Apr 4, 11:35*pm, Darryl Ramm wrote:
On Apr 4, 9:17*pm, JS wrote: Darryl, are you calling Erik an old wife? Jim :-) *:-) *:-) not three trailers, but I still own the little one Jim Jeez I've lost track of how many trailers and gliders you own and on what continents. "the little one" does not help, you had an ASH-25 -- most other gliders are "little"... Darryl I he means his '27. |
#9
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TCAS and slow moving/stationary targets?
On Apr 5, 9:17*am, Grider Pirate wrote:
On Apr 4, 11:35*pm, Darryl Ramm wrote: On Apr 4, 9:17*pm, JS wrote: Darryl, are you calling Erik an old wife? Jim :-) *:-) *:-) not three trailers, but I still own the little one Jim Jeez I've lost track of how many trailers and gliders you own and on what continents. "the little one" does not help, you had an ASH-25 -- most other gliders are "little"... Darryl I he means his '27. Ah and I just happen to be visiting Williams Soaring today and saw Jim's '27 in the paint shop. Fancy new Nixon air exhaust and solar panel and new fuselage paint job being applied. Very pretty. Darryl |
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