曝光台 注意防骗
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established visual reference), but this
should be at normal touchdown speed, as
it is tempting to make a dirty dart for
the runway without really being in a
position to cope with a problem—
you are in a high drag landing
configuration, and have been for
some time, and there are no
performance figures for go-arounds
under those conditions. It is a good
idea to get down quickly enough to
allow yourself at least a short time in
level flight. Ideally, you want to be
level at the circling radius.
Remember the difference in
indications from an ADF needle –
going to a beacon, the needle will be
on the opposite side of your heading
against the lubber line. Afterwards, it
will be on the same side. With a
VOR, of course, you will need to
turn the OBS to the reciprocal when
inbound to get a TO flag so you
don't get confused.
If you can't see anything by your
estimated time of reaching the
threshold, you must go around
(more technically, if you don't have
visual reference at the MAP, you
must go around and start the Missed
Approach Procedure).
On an ILS, follow the cross formed
by the two needles – the further
down the slope you are, the more
you use attitude and not power to keep
them in the middle, as long as it
doesn't get ridiculous. Watch for 100
feet above the DH and make a call
to yourself. If you get visual
reference, you can ask for a contact
approach, or you may be cleared for
a visual approach. When you break
out of cloud, keep your drift angle;
don't be tempted to point the nose
at the runway.
The decision bar across the runway
lights 1000 feet back from the
threshold is quite useful for
estimating your visibility (if there is a
moving strobe, or "rabbit", it is at
the point where the strobe stops).
So, if you can't see the threshold,
you can at least try to see the bar,
which is a series of white lights
across the ones in line with your
approach. Then use the distance
from the markers to gauge how far
ahead you can see.
DME Arc
Viewed from above, the end result
looks more like a polygon than an
arc, and the bigger the "arc" is, the
easier it is to fly, since it will be
flatter. It also helps to stay slightly
inside, and to use an RMI, but it isn't
impossible without one. below about
150 kts, leave yourself ½ nm or so
for interception purposes.
Start with an RB of 90° (left or right,
as convenient), then allow the RMI
needle to stray 5-10° behind. Your
DME distance will increase slightly.
Then turn enough to bring the
Instruments 263
needle the same number of degrees
ahead of the abeam point, carrying on
this way to keep the arc. In theory,
with nil wind, you could describe a
perfect circle by keeping the RB at
90°, but it almost never happens.
When coming off the arc for an
interception, anticipate the
movement by about 5°. If
intercepting a localiser, try to have it
tuned on the No 1 box, and use the
VOR for the lead radials on No 2.
Circling
This is designed to give you some
elbow room when approaching for
one runway, but actually landing at
another, or going to an airfield that
is very close to high ground, and to
keep the required clearance you
arrive at the threshold too high for a
proper approach. The figures will
therefore be higher - in fact, circling
MDA gives you at least 300 feet
above all obstructions in the visual
manoeuvring area, which is based on
radii from each runway threshold
(exam question), as per the aircraft
category. A=1.3 nm, B=1.5 nm,
C=1.7 nm, D=2.3 nm.
Although it sounds different, circling
is just another word for joining the
circuit in whatever way is handy at
the time, which implies that you
must be visual. In areas excluded
from circling, obstruction clearance
is not provided, so keep away.
If you have to bank more than 30°,
consider setting yourself up again. It
also helps to keep a little above the
MDA, say 50 feet, but remember
you are also below normal circuit
height. Since, by definition, the
weather is bad (or you wouldn't be
using it), set your radios and
machine up for the missed approach
before you reach MDA, just in case
you meet some clag on the
downwind leg.
Finals
When the weather is bad, and the
lighting fairly flat, the runway could
subject to certain optical illusions
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Canadian Professional Pilot Studies2(38)
