.
The FMS wind is averaged over a 30-second period.
Because of this 30-second smoothing, the FMS wind is less accurate under the following conditions:
.
Shifting wind;
.
Sideslip; or,
.
Climbing or descending turn.
The FMS wind cannot be considered as an instantaneous wind but, nevertheless, the FMS wind is:
.
A more recent wind information than the ATIS or tower average wind; and,
.
The wind prevailing along the aircraft flight path (aft of the aircraft).
Summary of Key Points
The METAR wind is a 10-minute-average wind.
The ATIS or tower average wind is a 2-minute-average wind.
The ATIS or tower gust is the wind peak value during the last 10-minute period.
The ATIS message is updated only if the wind direction changes by more than 30-degree or if the wind velocity changes by more than 5-kt over a 5-minute time period.
What’s Your Current Wind ?
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If an instantaneous wind reading is desired and requested from the ATC, the phraseology “ instant-wind “ should be used in the request (some controllers may provide such instant-wind without request under shifting and/or gusting wind conditions).
The IRS wind is a near-real-time wind.
The FMS wind is a 30-second-average wind.
The maximum demonstrated crosswind generally applies to a steady wind and is not a limitation (unless otherwise stated).
Depending on the flight phase and on the intended use, flight crews should select the most appropriate source of wind information.
Associated Briefing Notes
The following Briefing Notes provide expanded information for a complete awareness of wind-related factors:
.
8.5 - Landing on Wet or Contaminated Runway.
.
8.7 - Crosswind Landing,
Regulatory References
.
ICAO - Annex 3 – Meteorological Service for International Air navigation, Chapter 4.
.
ICAO - Annex 11 – Air Traffic Services.
.
World Meteorological Organization (WMO) Guide to Meteorological Instruments and Methods of Observation (WMO – No 8).
What’s Your Current Wind ?
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AIRBUS INDUSTRIE Getting to Grips with
Flight Operations Support Approach-and-Landing Accidents Reduction
Introduction
Operations in crosswind conditions require strict adherence to applicable crosswind limitations or maximum recommended crosswind values, operational recommendations and handling techniques, particularly when operating on wet or contaminated runways.
This Briefing Note provides an overview and discussion of operational factors involved in planning and conducting the approach and flare under crosswind conditions, particularly on a contaminated runway.
Briefing Note 8.5 – Landing on Wet or Contaminated Runway provides expanded information on operations on wet or contaminated runways.
Statistical Data
Adverse wind conditions (i.e., strong crosswinds, tail winds and wind shear) are involved in 33 % of approach-and-landing accidents.
Crosswind in association with runway condition is a circumstantial factor in nearly 70 % of runway excursion events.
85 % of crosswind incidents and accidents occur at landing.
Runway Condition and Maximum Recommended Crosswind
The maximum demonstrated crosswind and maximum computed crosswind, discussed in Briefing Note 8.6 – What’s your Current
Wind ?, are applicable only on dry, damp or wet runway.
On a runway contaminated with standing water, slush, snow or ice, a maximum recommended crosswind is defined (Table 1), depending on:
.
Reported braking action (if available); or,
.
Reported runway friction coefficient (if available); or,
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