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(exam question):
Problem Illusion Risk
Downslope Too low High approach
Upslope Too high Low approach
Rain Closer Low approach
Narrow Too high Low approach
Wide Too low High app & flare
Bright lights Too low High approach
In rain, a hilltop half a mile away can
look 250 feet lower when viewed
through water drops on the
windscreen which, if you will
remember the discussion on airflow
in the Principles of Flight chapter, will
not blow away because of the
boundary layer. Using a water
repellent is best.
It's bad enough coming up to an
airfield VFR in such conditions
when your eyes are used to the
gloom, but there's a short time
between breaking out and adjusting
your vision for the clues you need.
The danger lies in fitting the aircraft
attitude to what you expect to see,
and end up in an unusual attitude
very close to the ground – one
reason why airlines use the autopilot
for as long as possible.
Missed Approach
A missed approach is quite an urgent
procedure – you have just tried to
get as close to the ground as the
height of a small apartment block,
264 Canadian Professional Pilot Studies
which is a pretty fine tolerance, given
the velocities involved, and you
don't want to be there if you can't
see where you're going, so the
routine is to add full power, then get
the gear (and flaps) up. Actually, you
won't gain much by pulling the gear
up first at that speed, because it is
producing minimal drag and will do
until it's much higher.
Why?
Drag varies as the square of the
velocity, meaning that if you double
the airspeed, you get four times as
much. Conversely, reduce it by half
and you get a quarter of the drag.
Thus, at low speeds (as when
landing), the drag caused by the gear
has more or less the same effect
within a small range or, at least, the
incremental effect is less. Put
another way, the drag doesn't start to
vary much till about 20 kts above
your landing speed. For example,
pulling the gear up at 60 kts may
mean you won't climb at all. Doing it
at 70 (+10 kts) could mean 50 feet
per minute, 80 (+ 20 kts) could give
you 100 feet per minute. So far so
good, but 90 kts will mean 200 fpm,
and so on.
The point is that, only from about
30 kts or so above your landing
speed will you get any real benefit
from raising your gear and expecting
the decrease in drag to be the same
as an increase in thrust. Also, it
shouldn't really matter if you pull the
gear or flaps up first (remembering,
however, that stall speed increases if
you bank, as you might want to do
to avoid a mountain or two).
Check it out with your own machine
at a few thousand feet. Trim out in
the landing configuration straight
and level, apply full power and note
the vertical speed (it should be a
climb at this point). Then check the
figures for every 10 kts above the
original speed. You will find that,
after about 30 kts, the rate of climb
will reduce (after a modest increase),
and your machine will even start to
descend after about 60 kts! Airspeed
isn't always the answer when you've
got a lot to do in a hurry and you
need to establish some priorities. Of
course, you should not stay at such a
low speed for long, as you need to
get to normal climb speed, but at
least you're getting further away
from the ground. The point is, you
can fly first and clean up later (flaps
first, in small increments).
Remember the attitude, add the power
and the performance will be there.
If no instructions have been received
from ATC, follow the published
ones. If you still don't get any by the
time you reach the Missed Approach
Holding Fix, hold there in a standard
pattern on the inbound track.
If you have to leave the circling
procedure, one suggestion is to go to
the centre of the airport, and follow
the procedure for the approach you
just did as closely as possible.
Multi Crew
Essentially, the PF (Pilot Flying) stays
on instruments down to minima, and
shouts DECIDE when appropriate.
If the PNF (Pilot Non-Flying) says
GO AROUND, the PF stays on
instruments and does the go around.
If not (that is, the response is
"Visual, I have control"), the PF
hands over to let the PNF do the
landing (although the PNF can take
Instruments 265
control at any time if he gets the
necessary visual reference).
　
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