[jhb_airlines] Re: A beautiful evening

  • From: "Bones" <bones@xxxxxxx>
  • To: <jhb_airlines@xxxxxxxxxxxxx>
  • Date: Wed, 21 Sep 2005 12:05:48 +0100

I've used this in FPI a few times.

On a radar screen what we actually see is your ground track, not your
heading. We don't really know what your heading is and, if the wind is
strong, it could be quite different from your track (Mike had about 15
degrees of drift on a recent session). Normally this isn't a problem because
most of the time when we start vectoring the first turn is quite a
significant one.

Say you are tracking up towards DAYNE from Trent - approx track is 310. The
next track is going to be about 020 to position you round for the ILS onto
24. No problem here, the controller will simply say "JHB130 turn right
heading 020." You automatically know this is a radar heading and ATC have
now assumed control of your navigation.

It gets trickier when the heading change is smaller. Say you are coming down
L10 from IOM to WAL (track is 132) and I want to start vectoring you round
for the ILS at Liverpool. The initial track I want you to steer is going to
be about 120 - just a 12 degree nudge left. In this case I can't say
"JHB130, turn left heading 120." because you could come back with "JHB130,
is already heading 120." - wind giving you a 12 degree drift angle.. So, for
more finite changes we have to know your real heading before we can go any
further.

There are a few ways round this. First is the most obvious -

"JHB130, report your heading."
"JHB130 is heading 125."
"Roger, JHB130, turn left heading 115."

Nice and simple here as I now have the heading info I need and can apply the
10 degree nudge to this.

I could also have said, "JHB130, turn left 10 degrees." The result would
have been the same but it still leaves me without any idea what your actual
heading is.. Again, as soon as ATC give you a "turn left/right" command it
also infers ATC has taken charge of your navigation and that these are now
radar headings.

Finally we get to the example you mention <g>.. It could be that your
current track is good for ATC and to make sure you stay on it rather than
turn towards a navaid we effectively "lock" you on that heading. Again there
are two ways of doing this. The quicker is:

"JHB130, make your current heading a radar heading."

This is neat as it infers that ATC is now in charge of your navigation and
you should not deviate from this heading until we advise the next course. In
reality it means you switch from FMS or NAV mode to HDG mode.

A slightly longer version of the same is:

"JHB130, report your heading."
"JHB130 is heading 125."
"JHB130 roger, maintain heading 125" or "JHB130, maintain 125 as a radar
heading"

Again this extra R/T just gives ATC one more bit of information as we now
know your actual heading..

bones

-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Peter Dodds
Sent: 20 September 2005 23:31
To: jhb_airlines@xxxxxxxxxxxxx
Cc: pdodds@xxxxxxxxxxxx
Subject: [jhb_airlines] A beautiful evening


What is a "radar heading"? I heard Liverpool Tower say this
evening to an inbound Dash 8, (and have done before) - "Make your
present heading a radar heading", and always meant to ask.

Peter



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