Alternates for IFR Keep in mind!

As
VFR pilots we are dealt engine failures, communication failures, and
other "emergencies" to test our ability to make safe piloting
decisions. As instrument pilots we're taught to fly by the books and
stick to the plan. But, as we all know, even the best-laid plans get
changed by unforeseen circumstances. Often the unforeseen circumstances
involve weather.
Federal aviation regulations (FARs) require pilots to prepare
for some of these unplanned weather changes by carrying extra fuel and
filing an alternate destination on an IFR flight plan. It's the FAA's
way of making sure that pilots have an out. This helps to make what
might be a tense situation a simple matter of flying to the alternate
and landing there.
However, when the ceilings and visibility really come down
significantly over a widespread area, finding an acceptable alternate
can become a difficult task. When things get that bad, even the most
proficient instrument pilots ought to reconsider the importance of
launching such a trip in the first place.

Alternates as easy as 1-2-3

The regulations regarding
alternates are rather simple if you can remember 1-2-3. If the forecast
weather at your destination, from one hour before to one hour after
your estimated time of arrival, is at least a 2,000-foot ceiling and
three statute miles' visibility, then no alternate is required to be
filed. Beyond the 1-2-3 rule, things get a little more complicated. Standard IFR alternate minimums state that if the alternate
airport has a precision approach (ILS or PAR), it can be filed as an
alternate if, at the time of arrival, the forecast is no worse than 600
feet agl and two miles. If the airport is served by a nonprecision
approach (NDB, VOR, LOC, GPS, etc.), the ceiling rises to 800 feet agl
and visibility remains at two miles.
But the planning doesn't end there; the 600-2 and 800-2 rules
are basic minimums that apply when there are no specific alternate
minimums listed in the beginning of the National Ocean Service's
Terminal Procedures Publication (TPP) or on Jeppesen Airway Manuals'
airport layout pages. If alternate minimums for a specific airport are
not published, they are assumed to be standard minimums. Jeppesen
publishes the minimums regardless of whether they're standard or not,
to avoid any possible confusion. You'll find that airports in
mountainous areas or those that have obstructions near them generally
have higher-than-standard alternate minimums. It is imperative to check
these before filing an airport as the alternate, especially in
mountainous areas. It is also worth noting here that alternate minimums
apply for planning purposes alone. If you're airborne and heading to
the alternate, published minimums will now apply.
If the destination has no instrument approach, then weather
must be good enough to make a VFR approach from the IFR minimum en
route altitude (MEA). If you're under radar surveillance, however, you
may be able to descend to the minimum vectoring altitude (MVA), which
will sometimes be lower than the MEA. MVAs aren't printed on any chart;
they're known only by the controller and vary from sector to sector,
based on radar coverage. If you are flying near a large airport in flat
country, the controllers could probably get you down pretty low, given
the close proximity of the radar array. Airports located far from the
radar transmitter and controlled by a center controller probably
wouldn't have a vectoring altitude any lower than the MEA.

Wherefore art thou, alternates?

Flight service briefers
are generally the best source when fishing for an alternate, since they
have all of the terminal forecasts in front of them. If you receive a
DUATS weather briefing, you can manually find airports with acceptable
weather minimums in those reports as well. In general, large airports are your best bet for an alternate
without requiring you to dig through several charts to see what
airports meet the criteria for an alternate. Large airports have
weather reporting facilities right on the field, so they issue the
necessary terminal forecasts. These airports also have towers that are
open all or most of the day, superior approach lighting systems, and
multiple ILSs (or possibly even precision approach radar) to cover the
precision approach criteria. If the weather is marginal for one, pick a
second large airport, just in case, and plan your fuel accordingly.
Remember, though, that as convenient as large airports are for filing
purposes, should you head to one as an alternate, you may be faced with
long delays (holding patterns, vectors, etc.), which may require more
fuel.
Some computer flight planning programs, when interfaced with a
DUATS provider, make finding an alternate easier, but they may not know
whether an airport has a precision or nonprecision approach. Again,
this leaves the flight service briefer or a DUATS printout as the best
sources for finding alternates.

Plan B

Flexibility is key when flying in poor weather.
Hours and hours of flight planning are worthless if, after you get
going, the winds and destination weather aren't as forecast. In these
situations plan B should be in your mind before you even leave for the
airport. In fact, it's best to have several alternatives in mind. Your first clue that alternate plans will play an active role in
your flight will come during the preflight briefing. Is there a
widespread area of low ceilings and poor visibility in the destination
area? Were several reporting stations issuing "specials" to their
METARs? This could be the clue that the weather isn't behaving as
forecast and that weather predictions are likely to be off all day.
If preflight conditions are acceptable and the flight has
commenced, check in periodically with flight watch for updates. Note if
the forecasts are holding true. Is the weather trending better or
worse? Are other airplanes making it in? Have the TAFs been amended?
Again, if the forecasts have been blown for the worse and your
alternates are no longer acceptable, it's time to start looking for
more options or turning around. In this situation, fuel could be your
savior.

Don't fuel around

A friend of mine has a motto: "You can
never have too much fuel unless you're on fire." This holds true for
IFR flights as long as you stay within the weight and balance and
performance limits of the airplane. Fuel is cheap when you're heading
to your second alternate after missing a few approaches. Under IFR, the FARs require that you carry enough fuel to fly to
your intended destination and fly for another 45 minutes at normal
cruise power. It's up to the pilot to calculate the actual time en
route, given the winds, weather deviations, and other conditions that
may prolong or speed up the flight.
If the weather doesn't meet the 1-2-3 rule, you must carry
enough fuel to fly to your destination, fly from there to the
alternate, and fly after that for another 45 minutes at normal cruise
power. If your alternates are few and distances between them are far,
you may find that the 45-minute rule won't cut it. In densely populated
areas, 45 minutes may be adequate; however, on the rare day when the
weather is crummy in the desert Southwest, safe minimums may be a few
hours away. Pilots who ferry airplanes across oceans carry at least
three to four hours of extra fuel since alternates can be several
hundred miles away from the intended destination.