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Pilot's Handbook of Aeronautical Knowledge
Aviation Weather Services

Weather Briefings

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Pilot's Handbook of Aeronautical Knowledge

Preface

Acknowledgements

Table of Contents

Chapter 1, Introduction To Flying
Chapter 2, Aircraft Structure
Chapter 3, Principles of Flight
Chapter 4, Aerodynamics of Flight
Chapter 5, Flight Controls
Chapter 6, Aircraft Systems
Chapter 7, Flight Instruments
Chapter 8, Flight Manuals and Other Documents
Chapter 9, Weight and Balance
Chapter 10, Aircraft Performance
Chapter 11, Weather Theory
Chapter 12, Aviation Weather Services
Chapter 13, Airport Operation
Chapter 14, Airspace
Chapter 15, Navigation
Chapter 16, Aeromedical Factors
Chapter 17, Aeronautical Decision Making

Appendix

Glossary

Index

En Route Flight Advisory Service (EFAS)
A service specifically designed to provide timely en route
weather information upon pilot request is known as the en
route flight advisory service (EFAS), or Flight Watch. EFAS
provides a pilot with weather advisories tailored to the type
of flight, route, and cruising altitude. EFAS can be one of
the best sources for current weather information along the
route of flight.

A pilot can usually contact an EFAS specialist from 6 a.m. to 10
p.m. anywhere in the conterminous United States and Puerto
Rico. The common EFAS frequency, 122.0 MHz, is established
for pilots of aircraft flying between 5,000 feet above ground
level (AGL) and 17,500 feet mean sea level (MSL).

Hazardous Inflight Weather Advisory (HIWAS)
Hazardous Inflight Weather Advisory (HIWAS) is a national
program for broadcasting hazardous weather information
continuously over selected navigation aids (NAVAIDs). The
broadcasts include advisories such as AIRMETS, SIGMETS,
convective SIGMETS, and urgent PIREPs. These broadcasts
are only a summary of the information, and pilots should
contact a FSS or EFAS for detailed information. NAVAIDs
that have HIWAS capability are depicted on sectional charts
with an "H" in the upper right corner of the identification
box. [Figure 12-6]

HIWAS availability is shown on sectional chart
Figure 12-6. HIWAS availability is shown on sectional chart.

Transcribed Weather Broadcast (TWEB) (Alaska Only)
Equipment is provided in Alaska by which meteorological
and aeronautical data are recorded on tapes and broadcast
continuously over selected low or medium frequency (L/MF)
and very high frequency (VHF) omnidirectional radio range
navigation system (VOR) facilities. Broadcasts are made
from a series of individual tape recordings, and changes, as
they occur, are transcribed onto the tapes. The information
provided varies depending on the type equipment available.

Generally, the broadcast contains a summary of adverse
conditions, surface weather observations, PIREPS, and a
density altitude statement (if applicable). At the discretion of
the broadcast facility, recordings may also include a synopsis,
winds aloft forecast, en route and terminal forecast data, and
radar reports. At selected locations, telephone access to the
TWEB has been provided (TEL-TWEB). Telephone numbers
for this service are found in the Supplement Alaska A/FD.

These broadcasts are made available primarily for preflight
and inflight planning, and as such, should not be considered
as a substitute for specialist-provided preflight briefings.

Weather Briefings

Prior to every flight, pilots should gather all information vital
to the nature of the flight This includes an appropriate weather
briefing obtained from a specialist at a FSS, AFSS, or NWS.
For weather specialists to provide an appropriate weather
briefing, they need to know which of the three types of
briefings is needed—standard, abbreviated, or outlook. Other
helpful information is whether the flight is visual flight rules
(VFR) or IFR, aircraft identification and type, departure
point, estimated time of departure (ETD), flight altitude, route
of flight, destination, and estimated time en route (ETE).

This information is recorded in the flight plan system and a
note is made regarding the type of weather briefing provided.
If necessary, it can be referenced later to .le or amend a
flight plan. It is also used when an aircraft is overdue or is
reported missing.

Standard Briefing
A standard briefing is the most complete report and provides
the overall weather picture. This type of briefing should be
obtained prior to the departure of any flight and should be
used during flight planning. A standard briefing provides the
following information in sequential order if it is applicable
to the route of flight

1. Adverse conditions—this includes information about
adverse conditions that may influence a decision to
cancel or alter the route of flight Adverse conditions
include significant weather, such as thunderstorms or
aircraft icing, or other important items such as airport
closings.

2. VFR flight not recommended—if the weather for
the route of flight is below VFR minimums, or if
it is doubtful the flight could be made under VFR
conditions due to the forecast weather, the briefer may
state that VFR is not recommended. It is the pilot's
decision whether or not to continue the flight under
VFR, but this advisory should be weighed carefully.

 

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