by Jonathan M. Stern
Now that you have selected your route of flight on the basis of an outlook briefing, it is time to get a standard weather briefing. The weather briefing can be obtained by telephoning to, or visiting, an FAA Flight Service Station, or by use of DUATS. DUATS stands for Direct User Access Terminal Service and provides a real-time weather briefing over the telephone lines by using a computer and specialized communications software.
The briefing may be such that you will decide that the trip cannot be made. Such is not the case today, however. The weather, as is necessary for the completion of your flight planning, is as follows:
The winds aloft at 3,000 feet MSL are from 100 degrees at 27 knots. At 6,000 feet MSL, the winds are from 100 degrees at 31 knots. The altimeter setting at both Boston Logan and Bradley is 29.92" Hg. Surface temperature at both airports is 59°F/15°C. On this beautiful day, clouds are not even a factor. Visibility is 12 miles.
If you wanted to, you could fly this trip under visual flight rules, or VFR. Nonetheless, many instrument rated pilots choose to fly under IFR even when the weather is VMC (visual meteorological conditions). Moreover, because of the good weather both existing and forecasted to exist at your destination, you do not need to select an alternate airport.
An alternate airport is required unless the following criteria are met:
- The destination airport has a standard instrument approach procedure.
- The weather reports, forecasts, or any combination of them indicate that the weather will be at least a 2,000-foot ceiling and three statute miles visibility from at least one hour before to one hour after the estimated time of arrival at the destination airport.
If an alternate airport is required because the previous criteria are not met, the alternate must have forecast weather at the estimated time of arrival at the alternate of 600-foot ceiling and two miles visibility if the airport has a published precision approach procedure (one with electronic glidepath information) or 800-foot ceiling and two miles visibility if the alternate airport is equipped with only a nonprecision approach procedure (e.g., VOR or NDB).
If the proposed alternate airport has no published instrument approach procedure, the weather must be forecast to allow descent from the MEA and landing in VMC.
Despite the minima associated with selection of an alternate airport, should the flight actually be taken all the way to the alternate, the published minima for each individual IAP, not the alternate selection minima, are in force.