Procedures and Phraseology Examples
There are many procedures to which a GCA/PAR controller must adhere to ensure the safety of the aircraft on a Ground Controlled Approach. Some of these steps are very basic, like performing a radio check with the pilot, to ensuring the pilot knows what to do to complete the approach or fly a missed approach.
The controller and pilot must each find out a few things from each other. The controller must know what the pilot intends to do upon completion of the approach. Does he intend to land? Does he intend to do a touch and go and continue VFR? Maybe he wants to do a touch and go and then get vectored for another approach. This would be called a "radar square", where the final controller also vectors the aircraft around in what amounts to a traditional circuit pattern.
The pilot needs to know some basic information about the approach, among other things. What is the glidepath angle? This information, along with his indicated speed on final approach, helps the pilot figure out how fast to descend. For example, if he's going to fly final at about 140 knots, the wind might slow him down a little, and a 3° glideslope would require approximately 600-700 feet per minute in descent. The pilot also has to know the published Decision Height for the approach. If the runway environment is not in sight by the time the pilot reaches this altitude, a missed approach must be executed. What is he do in the event of a missed approach, planned or not? As a pilot, remember to keep corrections small under normal circumstances, just like hand-flying an ILS. Experience with autopilots in Flight Sim has left some pilots drastically out of the loop while on final. Quite often it seems to lead to aircraft falling disasterously below the glidepath. I would recommend that you disengage the AP and fly the aircraft by hand. It's more of a challenge that way, anyway.
All of this has to be communicated between the two parties prior to commencement of the approach. Below is an example of the radio transmissions on a GCA/PAR approach.
"CanForce 01, this is your final controller, radar #42. How do you read
this transmission?"
"CanForce 01, loud and clear, sir"
"CFC01, this will be vectors for a left hand precision radar approach
to runway26, glidepath angle on final set at 3°, published decision height
288 feet"
"CFC01, roger. After this approach, requesting radar square for
another GCA"
"CFC01, if no transmissions received for a period of 30 seconds while
on traffic or 5 seconds while on final..."
[Your missed approach instructions go here. Example of options are
things like:]
"fly runway heading for
radar vectors, climb to 3000", or
"carry out the published
missed approach", or
"maintain last assigned
heading and climb to 3000", or
"proceed direct to the
Greenwood NDB and climb to 4000",
[followed by:]
"...and attempt to contact
Greenwood Terminal on 120.6"
When the aircraft is nearing the final approach course and you have transitioned
to the PAR display ...
"CFC01, fly heading 280. Now on final approach - do not acknowledge
further transmissions unless requested by radar."
Issue instructions and position information while the aircraft is on final approach at least every 5 seconds, preferably more often, to make sure the pilot is kept abreast of where he is and that he is still in communication with you. These transmissions should sound like the following:
"well right of the on course correcting rapidly - fly heading 285"
"9 miles from touchdown - fly heading 270"
"intercepting the on course, fly heading 260"
"on course - 8 miles from touchdown"
"left of the on course - correcting slowly" (or "nicely", or "rapidly")
"left of course and paralleling"
"drifting left of course, turn right heading 262"
"well left of the oncourse - turn right heading 265"
"on course fly heading 262 - 7 miles from touchdown - 2 miles to
glidepath interception"
"slightly left of the on course - standby for glidepath interception
- wheels should be down"
"intercepting glidepath - commence descent for a 3° glidepath
NOW - published decision height 327 feet"
"initial rate of descent has you slightly below glidepath, adjust
rate of descent"
"on course"
"above glidepath - adjust rate of descent"
"left of the on course, fly heading 264 - 4 miles from touch down"
"back on glidepath - resume normal rate of descent - on course"
"below glidepath adjust rate of descent - 3 and one half miles from
touch down - on course"
"3 miles from touchdown - dangerously below the glidepath - level
off your aircraft - acknowledge"
[To which a pilot should level off and report doing so]
"back on glidepath - resume normal rate of descent - two and one
half miles from touchdown"
"on course"
"on glidepath"
"2 miles from touchdown - tower clears CFC01 land runway 26 - winds
330 at 10 - check gear down - acknowledge"
[and so on to ensure the pilot stays on or near the approach path]
"one half mile from touchdown"
"passing through radar control limits"
"on course - slightly above the glidepath"
"approaching threshold - look ahead your touch and go - radar standing
by"
You can see why I recommend using a voice interface for communications. While the pilot doesn't have to say much, the controller sure does and the response would be much more immediate rather than the pilot having to read the instructions before he can comply with them. This also allows the controller to keep his eyes on the radar display and the pilot to keep his eyes on the instruments. Control of the aircraft is essential, as with any precision approach.
One final note: If a controller sets up an approach using one scenery file, and the pilot is flying with a different one, the runways may not line up quite right. This would have the effect of the controller directing the pilot to a runway where the pilot doesn't see it. A pilot may break off the approach, according to the radar display, to line himself up with the runway when he has it in sight. I would suggest advising the controller, "Field in sight, taking over visually". Also, depending on how accurately the approach information is setup, the final approach course on radar may not quite line up with what the pilot sees. There are potential errors, so keep alert and remain understanding at all times.
Screen Shots
First, we'll take an overall look at the new program and how it starts
up by default. Then, I've set up an aircraft on final, not necessarily in
a good position, and have taken some screen shots to go with that, from Traffic
to PAR to cockpit views for comparison. Have a look at the overall image:
Below is a screen shot of the Traffic Display with some test targets,
along with an aircraft, VPAR42, on final. Have a look at the Traffic display,
then the following PAR screens to compare, and finally the cocpit view from
the position as seen on the radar screen shots.
VPAR42 is out of 900 feet, descending at about 700 fpm, doing a groundspeed
of 100 knots. Note the shape of the "PAR Block" in the Traffic display.
A sample shot of an aircraft on final taken with the PAR display
in Linear mode. VPAR42 is about 3 NM back, left of the centerline and
well above the glidepath. The next image is an overview of the PAR display
in Logarithmic mode.
The PAR display in Logarithmic mode. The displacement from the Final
Approach Course and the glidepath are both more evident with the better
resolution given by the logarithmic mode close in on final, as in image above.
Note also the shape of the "PAR Block" in the Traffic window in this mode.
And this is what the aircraft on final sees as he descends in good
VMC on final from the position shown on the PAR screen above. Take notice
of the ILS needle positions. You may have noticed that the aircraft in
this picture is actually climbing at 400 fpm while the radar capture above
indicates a descent. That's because there was a lag of a few seconds while
I task-switched to get the images, and this allowed the aircraft to nose-up
on me a bit as I was hand-flying at the time.