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will allow it the necessary performance for the approach
and landing or go around/missed approach? Is the aircraft properly equipped for the approach? Is the flight
crew qualified and current for the approach? Many of
these types of issues must be considered during preflight
planning and within the framework of each specific air
carrier’s OpsSpecs, or Part 91.
WEATHER CONSIDERATIONS
Weather conditions at the field of intended landing
dictate whether flight crews need to plan for an instrument approach and, in many cases, determine which
approaches can be used, or if an approach can even be
attempted. The gathering of weather information
should be one of the first steps taken during the
approach-planning phase. Although there are many
possible types of weather information, the primary
concerns for approach decision-making are wind
speed, wind direction, ceiling, visibility, altimeter
setting, temperature, and field conditions. It is also a
good idea to check NOTAMs at this time in case
there were any changes since preflight planning.
Wind speed and direction are factors because they
often limit the type of approach that can be flown at
5-2
a specific location. This typically is not a factor at
airports with multiple precision approaches, but at
airports with only a few or one approach procedure
the wrong combination of wind and visibility can
make all instrument approaches at an airport
unavailable. As an example, consider the available
approaches at the Chippewa Valley Regional
Airport (KEAU) in Eau Claire, Wisconsin, shown
in Figure 5-1. In the event that the visibility is
reported as less than one mile, the only useable
approach for Category C airplanes is the Instrument
Landing System (ILS) to Runway 22. This leaves
very few options for flight crews if the wind does
not favor Runway 22; and, in cases where the wind
restricts a landing on that runway altogether, even a
circling approach cannot be flown because of the
visibility.
WEATHER SOURCES
Most of the weather information that flight crews
receive is issued to them prior to the start of each flight
segment, but the weather used for inflight planning and
execution of an instrument approach is normally
obtained en route via government sources, company
frequency, or Aircraft Communications Addressing and
Reporting System (ACARS).
Air carriers and operators certificated under the
provisions of Part 119 (Certification: Air Carriers
and Commercial Operators) are required to use the
aeronautical weather information systems defined
in the OpsSpecs issued to that certificate holder by
the FAA. These systems may use basic FAA/National
Weather Service (NWS) weather services, contractor
or operator-proprietary weather services and/or
Enhanced Weather Information System (EWINS)
when approved in the OpsSpecs. As an integral part
of EWINS approval, the procedures for collecting,
producing, and disseminating aeronautical weather
information, as well as the crewmember and dispatcher training to support the use of system
weather products, must be accepted or approved.
Operators not certificated under the provisions of Part
119 are encouraged to use FAA/NWS products through
Automated Flight Service Stations (AFSSs), Direct
User Access Terminal System (DUATS), and/or Flight
Information Services Data Link (FISDL). Refer to the
Aeronautical Information Manual (AIM) for more
information regarding AFSSs, DUATS, and FISDL.
The suite of available aviation weather product types is
expanding with the development of new sensor systems, algorithms, and forecast models. The FAA and
NWS, supported by the National Center for
Atmospheric Research and the Forecast Systems
Laboratory, develop and implement new aviation
weather product types through a comprehensive process
known as the Aviation Weather Technology Transfer
process. This process ensures that user needs and
technical and operational readiness requirements are
met as experimental product types mature to operational application.
The development of enhanced communications capabilities, most notably the Internet, has allowed pilots
access to an ever-increasing range of weather service
providers and proprietary products. It is not the intent
of the FAA to limit operator use of this weather information. However, pilots and operators should be aware
that weather services provided by entities other than
the FAA, NWS, or their contractors (such as the
DUATS and FISDL providers) may not meet
FAA/NWS quality control standards. Therefore, operators and pilots contemplating use of such services
　
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