AOPA Turbine Pilot Magazine - May 2018 - 99

P&E

ON INSTRUMENTS

Prepping
for Plan B
Your alternate is below minimums. Now what?
BY THOMAS A. HORNE

SARAH HANSON

EVERY INSTRUMENT-RATED PILOT KNOWS

that an alternate must be named if the destination airport meets certain weather
limits. You need to name an alternate airport on your IFR flight plan if, for the period
of time one hour before and one hour after
your estimated time of arrival, the weather
is forecast to include a ceiling of 2,000 feet
agl and/or visibilities less than three statute
miles (the 1-2-3 rule).
Assuming you take off for a destination requiring an alternate, you must be
able to shoot an approach at the destination, miss that approach, and then fly
to your alternate-and land with 45 minutes' worth of fuel reserves. This is the
letter of the law for operations under
FAR Part 91, but most corporate flight
departments use more conservative
rules. Ones that require enough fuel to
hold for five minutes at 5,000 feet after

missing an approach, then fly to an alternate 100 or 200 nautical miles away at
long-range cruise power, and landing
at that alternate in visual meteorological conditions with 45 minutes of fuel
remaining in the tanks. These are the
rules recommended by the National
Business Aviation Association, so they're
known as NBAA IFR reserves.
Most of us fly using the basic 1-2-3 rule,
and plan for a landing at the alternate with
45-minute reserves. But there's a whole lot
more to it than memorizing these minimal rules. That's because the weather plays
a huge factor. And dealing with weather
means carrying fuel reserves more generous than a mere 45 minutes.
Let's say you miss the approach and fly
to your alternate. This alternate must be
forecasting weather with ceilings at or above
600 feet and two-mile visibility (600-2) if

it's served by a precision approach. If it only
has nonprecision approaches, then 800-foot
ceilings and two-mile visibilities (800-2) are
required. Once committed to flying to your
alternate, the published minimums apply.
None of this may matter if low IFR
(ceilings below 500 feet, visibilities below
one statute mile) conditions prevail over
a wide area. Warm fronts are notorious
for generating widespread low ceilings
and visibilities, and they tend to move
slowly. Same thing with overnight cooling of rain-soaked terrain. Will you have
enough fuel to make it to your alternate
and complete an approach successfully?
Is there a chance you'll miss the approach
at the alternate? Then what? Hint: You
can always call ATC and ask for a different alternate in flight; use ATC to provide
weather updates as well.
What if the weather involves thunderstorms or fast-moving cold fronts?
Will you have enough fuel to divert
around adverse conditions and meet the
regulations? And what if the weather is
low and you make multiple approaches
at your destination, hoping that the next
approach will let you see the airport environment? With every approach you're
eating into your fuel reserves-enough
that you may not be able to reach your
named alternate.
You need to think about all this during your preflight planning. A check for
nonstandard alternate minimums is
also in order. Are they above 600-2 or
800-2? They could be if obstacles are
nearby, or if a tower is closed. Are certain runways closed? Are all navaids fully
operational? Is the airport itself closed?
Does your alternate have any instrument
approaches? If not, then you must be able
to descend from the minimum en route
altitude and land in VMC. Oh, and don't
forget to do a receiver autonomous integrity monitoring (RAIM) check of your
GPS navigator before takeoff.
Ideally, your destination and alternate
airports will provide terminal forecasts
to help your preflight planning. METARs
can help you understand initial weather
conditions, and in flight they can provide
forecast confirmation or blown forecasts.
No TAFs? Then you'll have to rely on more
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AOPA Turbine Pilot Magazine - May 2018

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