Originally posted by NJA Capt
Hard to see in a jet (at an unfamiliar airport) at 600' 2 miles from the airport. Some aircraft like the C750 are very restricted in crosswinds (less than 4 degrees bank at times), that's why we ask on short final. Some airports don't locate windsocks anywhere near the landing threshold.
I understand. If you need to ask, do so. I just want you to understand what you're getting. What I give you may be 30 deg and 10 kts different than what the wind actually is at the threshold at the moment.
Why is it when we are vectored "for traffic" it is always toward the ONLY TCAS targets? Or even better.....We are told of passing traffic 15nm away (don't care), and are given no warning of the 767 that passes 2000' over my window (DO care!!)?
Two part answer. First, one of the first techniques we learn in radar is that's it's almost
always easier to vector you to miss
behind the other target. Trying to zoom you in front of another target is very difficult, unless the speed differences are really great. So, what do they teach everyone in the acadamy? If two aircraft are on crossing courses, and speeds are similar, turn one right at the second, and they miss with minimum safe distance. I know, sounds nuts, but works.
Second part of answer lies in Controller's Handbook, Chap 5, merging target procedures:
5-1-8. MERGING TARGET PROCEDURES
a. Except while they are established in a holding pattern, apply merging target procedures to all radar identified:
1. Aircraft at 10,000 feet and above.
2. Turbojet aircraft regardless of altitude.
3. Presidential aircraft regardless of altitude.
b. Issue traffic information to those aircraft listed in subpara a whose targets appear likely to merge unless the aircraft are separated by more than the appropriate vertical separation minima.
EXAMPLE-
"Traffic twelve o'clock, seven miles, eastbound, MD-80, at one seven thousand."
"United Sixteen and American Twenty-five, traffic twelve o'clock, one zero miles, opposite direction, eastbound seven twenty seven at flight level three three zero, westbound MD-Eighty at flight level three one zero."
c. If the pilot requests, vector his/her aircraft to avoid merging with the target of previously issued traffic.
NOTE-
Aircraft closure rates are so rapid that when applying merging target procedures, controller issuance of traffic must be commenced in ample time for the pilot to decide if a vector is necessary.
d. If unable to provide vector service, inform the pilot.
So in the case you mentioned. If it's a VFR target say twelve miles away, with an
un-verified Mode C altitude, I cannot assume you are separated by "more than the appropriate vertical separation minima. " So you're at 140, descending to 100, and I call traffic "Eleven O'Clock, twelve miles, altitude
indicates three thousand five hundred." Seems silly, but God only knows what the target's actuall alttude is. And I'm supposed to issue it it time for you to decide if you'd like a vector around it. In the second case, I
know the B767 is separated by more than the appropriate minima, (1000') so I need not issue it.
I think it actually gets pretty silly and confusing to pilots at times. Controllers too. We got guys saying "TCAS Traffic, eleven o'clock, four miles....." I'm not sure what "TCAS Traffic" is supposed to be, except we're differentiating between "Sit up and pay attention" traffic, and Gee Whiz info...
TCAS RAs are inhibited at approx 1200' AGL and shouldn't give RAs. 95% of GA traffic and half of the corporate world have no idea what we are talking about (TCAS). There is no FAA guidance to maintain "TCAS" separation.
I know, I was just trying to remind the folks that don't know, that they should give the TCAS equipped traffic a little extra room. We have a dozen TCAS RAs a year between aircraft that were legally visually separated. I've told folks to maintain visual separation, and then had the targets completely
merge at nearly the same altitude. Some folks figure 200' is as good as two miles; and it often was before TCAS...
Hope that helped!
