Aeronautical Information Manual (AIM), page 449

Index   448 -- Page 449 -- 450


information. The FAA has determined that operators
and pilots may utilize the following approved sources

of aviation weather information:

1. Federal Government. The FAA and NWS
collect raw weather data, analyze the observations,
and produce forecasts. The FAA and NWS
disseminate meteorological observations, analyses,
and forecasts through a variety of systems. In
addition, the Federal Government is the only
approval authority for sources of weather observa-
tions; for example, contract towers and airport

operators may be approved by the Feder al

Government to provide weather observations.

2. Enhanced Weather Information System

(EWINS). An EWINS is an FAA authorized,

proprietary system for tracking, evaluating, report-

ing, and forecasting the presence or lack of adverse

weather phenomena. The FAA authorizes a certific-

ate holder to use an EWINS to produce flight

movement forecasts, adverse weather phenomena

forecasts, and other meteorological advisories. For

more detailed information regarding EWINS, see the

Aviation Weather Services Advisory Circular 00-45

and the Flight Standards Information Management
System 8900.1.

3. Commercial Weather Information
Providers. In general, commercial providers
produce proprietary weather products based on
NWS/FAA products with formatting and layout
modifications but no material changes to the weather
information itself. This is also referred to as
"repackaging." In addition, commercial providers
may produce analyses, forecasts, and other
proprietary weather products that substantially alter
the information contained in government-produced
products. However, those proprietary weather
products that substantially alter government-
produced weather products or information, may only
be approved for use by 14 CFR Part 121 and Part 135
certificate holders if the commercial provider is
EWINS qualified.


Commercial weather information providers contracted by
FAA to provide weather observations, analyses, and
forecasts (e.g., contract towers) are included in the Federal
Government category of approved sources by virtue of
maintaining required technical and quality assurance
standards under Federal Government oversight.

7-1-4. Preflight Briefing

a. Flight Service Stations (FSSs) are the primary

source for obtaining preflight briefings and inflight
weather information. Flight Service Specialists are
qualified and certificated by the NWS as Pilot
Weather Briefers. They are not authorized to make
original forecasts, but are authorized to translate and
interpret available forecasts and reports directly into
terms describing the weather conditions which you
can expect along your flight route and at your
destination. Available aviation weather reports,
forecasts and aviation weather charts are displayed at

each FSS, for pilot use. Pilots should feel free to use

these self briefing displays where available, or to ask
for a briefing or assistance from the specialist on duty.

Three basic types of preflight briefings are available

to serve your specific needs. These are: Standard

Briefing, Abbreviated Briefing, and Outlook Brief-

ing. You should specify to the briefer the type of

briefing you want, along with your appropriate

background information. This will enable the briefer

to tailor the information to your intended flight. The

following paragraphs describe the types of briefings

available and the information provided in each


AIM, Paragraph 5-1-1 , Preflight Preparation, for items that are

b. Standard Briefing. You should request a
Standard Briefing any time you are planning a flight
and you have not received a previous briefing or have
not received preliminary information through mass
dissemination media; e.g., TIBS, TWEB (Alaska
only), etc. International data may be inaccurate or
incomplete. If you are planning a flight outside of
U.S. controlled airspace, the briefer will advise you
to check data as soon as practical after entering
foreign airspace, unless you advise that you have the
international cautionary advisory. The briefer will
automatically provide the following information in
the sequence listed, except as noted, when it is
applicable to your proposed flight.
1. Adverse Conditions. Significant meteoro-
logical and/or aeronautical information that might

influence the pilot to alter or cancel the proposed

flight; for example, hazardous weather conditions,
airport closures, air traffic delays, etc. Pilots should
be especially alert for current or forecast weather
that could reduce flight minimums below VFR or
IFR conditions. Pilots should also be alert for any

Meteorology 7-1-5

Page 449 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   448 -- Page 449 -- 450