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J. Ross Russo |
This originally appeared in IFR MAGAZINE and is reproduced here by permission of Belvoir Publications.
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If you're like most instrument pilots, you spent a lot of training
time flying full approaches, muddling through procedure turns
while you tried to figure out just exactly where the final approach
course really was. Unfortunately, all that training wasn't good
practice for the real world; the full approach just isn't the
usual way of doin' business.
Vectors to final is the way it's really done.
There's no doubt that full approaches are more difficult than
simply following a controller's headings. But just because vectoring
relieves you of getting yourself onto final, doesn't mean there
aren't a few things you ought to be doing while the controller
lines you up. There are some subtleties to being vectored and
they change with the weather or a pilot's requests. Knowing a
bit about the finer points can save you time and result in a cleaner
approach.
First, let's look at the approach architecture from the controller's
point of view, since he or she is doing most of the headwork on
a vectored approach. A controller must consider a point in the
approach that you won't find published on either Jeppesen or NOS
plates. It's called the "approach gate" and it's defined
in the pilot/controller glossary of the AIM as "an imaginary
point used within ATC as a basis for vectoring aircraft to the
final approach course."
On precision approaches, approach gates are generally established
along the final approach course one mile from the outer marker
(or another fix, in lieu of a marker) on the side away from the
airport. For non-precision approaches, they're a mile outside
the FAF. In either case, when measured along the final approach
course, the gate will be no closer than five miles from the landing
threshold. In some cases, they may be farther from the threshold.
Just how your vector relates to the gate depends on the weather.
If the weather's good, the controller can vector you directly
to the gate, but not inside it. For vectoring purposes, the FAA
defines "good weather" as a reported ceiling and visibility
of at least 500 feet above the minimum vectoring altitude (MVA)
in the area you happen to be in plus a visibility of three statute
miles. If no weather reporting is available, Pireps on ceiling
and vis will do.
A "good-weather" vector to final should produce a groundtrack
that will intercept the final approach course at an angle not
greater than 20 degrees. Note the emphasis on groundtrack. To
compensate for wind, the controller might assign a heading that
will appear to result in an intercept of more (or less) than
20 degrees.
When the weather is less less than 500 feet above the MVA with
less than three statute miles of vis, expect a vector to a point
no closer than two miles outside the approach gate. In this case,
the controller should provide a vector that will result in an
intercept groundtrack that's no greater than 30 degrees. If it
all works out, this should put you on final at least seven miles
from the landing threshold. If you're a helicopter driver, the
intercept angle can be up to 45 degrees.
Just ask
Even though controllers try to correct their vectors for winds,
it's been my experience that they don't always succeed. Remember,
the controller is looking at a radar-enhanced depiction of your
aircraft, not a real-time representation of where you are. This
lag, and the fact that you're not the controller's only customer,
sometimes results in a bad vector.
One case in particular comes to mind. I was flying from Tampa
to Jacksonville's Craig airport (CRG) one rainy, windy night.
The approach controller was vectoring me to final for the ILS
32 approach. I'd been battling 60-knot winds out of the northeast
for the entire trip, so I knew that the wind correction angle
on final would be truly impressive, perhaps in the neighborhood
of 30 degrees.
I was on a heading of 050 degrees, 90 degrees off the final approach
course. This heading, along with VOR, DME, and LORAN readouts,
confirmed that I was on a base leg southwest of the airport and
that I had a direct headwind. The mental warning flags were already
popping up. I knew this monster headwind would quickly turn into
a monster crosswind on final. All the ingredients were present
for an undershooting vector to final. All it would take was a
slight oversight on the controller's part.
Since the weather was lousy, I knew that I'd be vectored to a
point two miles outside the gate and that the stiff winds would
mean I'd need a heading of about 020 degrees to get the required
groundtrack for a 30 degree intercept. Would the controller be
sharp and give me a heading that would correct for the wind?
"N1161X, three miles from ADERR, turn left heading 350,
maintain 2,000 feet until establised, cleared for the ILS runway
32 approach."
I knew right way that this heading would never intercept final;
it would only parallel it. (See Paul Bertorelli's "Double-Checking
the Vector.") So, acting as the final authority, I let the controller
know that because of the wind, I'd need 020 degrees to intercept.
The heading was approved as requested and the approach was completed.
Say the magic words
Okay, so we know that if the weather is a certain ceiling relative
to the MVA, we'll get a longer trip down final. But how do we
to tell what the MVA is? Unfortunately, only the controller knows
for sure since he has above his radar screen a chart depicting
all the MVAs in his area. Absent the chart, use the procedure
turn or glideslope intercept altitude as a guide to the MVA. It
should be relatively close. If you're really hard-over on the
MVA issue, contact the plans and procedures specialist at your
local ATC facility and request a copy of that facility's MVA chart.
About the only sure fire way to know where you're being vectored
is to be cognizant of the visibility. If it's reported as less
than three miles, you'll be going the long way around, two miles
outside the gate.
There are some some things that we pilots can do to speed up or
slow down the vectoring process. But as with other aspects of
the ATC-pilot relationship, we have to ask. Controllers can't
offer.
Let's say you're flying into your home drome and the visibility
is reported as two-and-a-half miles. Bingo. Plan on a seven mile
final. But you've flown the approach hundreds of times before,
and you're familiar with the local terrain and obstructions.
To shorten up the final, simply tell the controller that you'll
accept vectors inside the approach gate.
This allows the controller to vector you to a point not closer
than the final approach fix, with an intercept angle of not greater
than 20 degrees. Depending upon your direction of flight, this
trick could easily save you seven or eight miles of vectoring.
Of course, your request has to fit in with the controller's overall
sequencing plan. He won't be able to give you close-in vectors
if they'll violate minimum separation standards with another aircraft.
On the other hand, even if the weather is good but you've dropped
your timer, misplaced the plate or are otherwise trailing on static
wicks, you'll want to slow things down. Just tell the controller
that the approach will be "coupled" or "evaluated,"
or words to that effect. You'll then get vectored to a point
at least two miles outside the approach gate.
It may take a couple of requests to get the message across, however.
As an F-16 flight examiner for the Air Force, I frequently fly
evaluated approaches. Earlier this year, I was giving an instrument
checkride to a pilot in Great Falls, Montana. The weather was
good and the vectors were resulting in tight turns to final.
I wanted to see an approach that would approximate actual instrument
conditions, so I had the examinee inform the controller that all
subsequent approaches would be "evaluated approaches."
Approach rogered our call but the next vector was as tight as
the first.
Obviously, we weren't communicating. During climbout I informed
the controller that the next approach would be an "evaluated,
coupled approach," and I'd like vectors two miles outside
the gate. It didn't matter that the F-16 can't fly a coupled
approach. All that mattered was that I used the magic words,
all of them. It worked.
There's one instance when a request for a tight vector will not
be honored. An aircraft is supposed to be vectored so that it
will not intercept the localizer above the glideslope. In designated
mountainous terrain, that restriction, coupled with the high
MVAs in mountainous areas can mean that the approach gate is quite
a few miles from the FAF. In these circumstances, the controller
just won't be able to get you any closer to the gate.
Heed the clue bird
When it comes to the radio, pilots are lucky; we can use just
about any phraseology we want. Controllers, technically speaking,
aren't as fortunate. Their words are very strictly prescribed
by the Air Traffic Control Manual (7110.65). And every so often,
an FAA boss listens in to evaluate how a controller is speaking.
If a controller, for example, sees that an aircraft is well off
course while inside the approach gate, he has no option other
than to say: "N12345, X miles from the airport, X miles right/left
of course, say intentions." These words are spelled out
for him, crystal clear.
They should be just as clear to you should you ever hear them
while on final approach. The clue bird is hammering desperately
on your windscreen. The controller is saying everything within
his legal limits to let you know that this particular approach
is not going well for you. When the controller asks for your intentions,
request vectors around for another approach. When things have
gone that far awry, they seldom get any better. Take the hint.
This is one birdstrike you'll be thankful for.
Vectors across final
What should you do if the controller forgets about you and drives
you across the final approach course without clearing you for
the approach? The controller's manual is very clear on this point,
too. The controller is required to inform a pilot if a vector
will take him across final, along with the reason. Something like
this; "N12345, expect vectors across final for spacing."
But, if for some reason the controller is unable to inform the
pilot, the pilot is not expected to turn inbound on the final
approach course.
While receiving vectors, the headings that you're given, in conjunction
with what your avionics tell you, will give you the position awareness
you need to anticipate the controller's next action. If that 30
degree intercept heading
isn't accompanied by the approach clearance or a reason to expect
vectors across final, it's time to launch your own clue bird.
Speak up early and often. Ask the controller if you're to expect
vectors across final or if you're cleared for the approach. Make
your communication clear, timely, and definite. Clue birds fly
equally well in both directions.
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