reply to post by Sandbar
Glad you came back......
Regarding the photo, in this post ---- clearly, those two airplanes are NOT at the same altitude! A matter of only 1,000 feet can mean the difference
in whether or not the contrails will form.
AS TO looking at the H8 charts....remember that the Jet Airways are (mostly) referenced to VORs. That will change, soon, as the "21st Century ATC"
(as it's sometimes called) concept is fully integrated and developed. GPS routes will be the norm. It may still be called "Free Flight" in some
corners of discussion....
Back to the J Airways....firstly, even IF on the Airway, each airplane's onboard IRS/INS will have slight discrepancy in accuracy to center-line...as
you know, even on Victor Airways, the route is so wide, for a reason. Individual tolerances for each airplane. Jet Airways, same thing....anywhere
within the total width is considered "on course".
ALSO...naturally, 'direct' routings are requested, approved and provided quite frequently. Looking at most Airways, with all the bends and doglegs
that occur, you can see why. In the days before nearly everyone had Inertial Reference Systems, Flight Management Computers, and the gee whiz-bang
stuff...(like, the Boeing 707/727/DC-9 days) when we wanted a "direct to" somewhere, the controllers just gave us a heading...one that He/She
determined from their radar....and flew that heading until the VOR was within reception range. Heading would be amended, sometimes, if the winds were
different than the controller had "guessed" initially.
Also, there are "standing agreements" between different ATC facilities. Gentleman’s agreements, so that one can offer and approve a "direct"
routing, even if the next waypoint is in someone else's airspace jurisdiction, without asking them first. AFTER the clearance, he phones or sends a
message to the next "guy" to let him know. On the occasions when no such agreement exists, AND you request something like a "direct", then the
controller you're on frequency with has to phone the next guy
first, to get their approval.
It is much more simple, in practice, than it is trying to write it up to describe it....POINT is, you cannot assume every airplane you see is
exactly on any particular Airway, just because its charted that way.
BUT, the High charts DO show the routing to expect, and verify that the airplanes ARE making their way along those routes. The "FlightAware" site is
useful there, too.....
_________________
BTW, about going 'direct'....many, many times on "red-eyes" Eastbound from the west coast, because it's late, and very little other traffic...say,
going LAX - EWR...shortly out of FL230, when with the High Sector controller of the center, have been given "direct to Slate Run"....the "Slate Run"
VOR (SLT) is
all the way across the country, and is the start of one of the Instrument Arrival procedures for Newark. (The
"Williamsport One Arrival"). With the FMC of today, simple
matter to to just pull up that waypoint (SLT), and make it "next", skipping all the ones in between. Of course, we like to keep track of the fuel
burn, checking it as we go along....so, the FMC has an option of "abeam" points, for all the ones we "skipped"....it makes little extra waypoints and
"draws" them in, along the new course line we just defined, on the "direct to" Slate Run clearance.
Makes quite a mess, sometimes though....you get waypoints that clutter it up, some only a few miles apart, due to the geometry as they get "pulled"
sideways....so, you spend a few minutes deleting the messy ones. Hey, gots lots of time to kill....need something to do, to stay awake!!
edit on 30 January 2011 by weedwhacker because: (no reason given)
