we must lose 5,000 feet of altitude in
our descent. To do that comfortably,
we should start our descent at least
20 miles out. (That’s 4 [nm covered
for each 1,000 feet] x 5 [thousand feet
we need to lose] = 20 nm.) To make it
even easier, most GPS navigators have
a “vertical speed to target” option
that you can set up in one of the data
fields. When that window reaches
“500 fpm,” it’s time to consider
starting down. Obviously, adjustments
may be needed depending on the
particular situation.
considerably with altitude, we may wish
to alter our basic approach plan to get
the smoothest ride possible.
The best advice is to begin checking
weather well before we start our descent.
That includes checking local automated
surface observing system (ASOS), auto-
mated weather observing system (AWOS),
and automated terminal information ser-
vice (ATIS) broadcasts or getting the latest
weather from flight watch, flight services,
or air traffic control. We’ll want to know
what the visibility and winds are, and what
approach/runway to expect. As part of our
procedure, we should also check with
other pilots—or just monitor the local
Distance Required Formula
Groundspeed
(in knots)
60
90
120
160
210
Multiplier
Multiply this
number by the
thousands of
feet you need
to descend.
2
3
4
5
6
As helpful as the simple math problem may be, many competing factors
can influence our descent plan. These
include weather, traffic, fuel considerations, terrain, and navigation—to
name a few. Let’s take a look at these
factors as they apply to our planning.
CHECK THE WEATHER
Before we even start a descent, it
pays to have a good idea of the conditions ahead. In fact, where and how
we plan our descent hinges to some
degree on the weather conditions
both along the route and at the destination airport. Cloud conditions
might dictate when and where we
initiate our descent to maintain
visual flight rules (VFR) conditions.
Visibility can also be a key concern.
We might do better to remain at a
higher altitude if the conditions are
hazy below. And let’s not forget
about turbulence, especially if we
have passengers aboard and want to
provide a comfortable flying experience. Since turbulence can vary
