This is a mini-lesson. AC 00-45 has a very good explanation of how to use and interpret an FD. Page numbers cited here use AC 00-45E (although AC 00-45G is now available and can be downloaded for free from the FAA).
The Winds Aloft Forecast (FD) provides a forecast of the wind direction, wind speed, and temperature.
Understand how the FD applies to helicopter operations (and use AC 00-45 to understand and interpret the information provided on the FD).
- AC 00-45E reference
- FD highlights
- What an FD can tell you about turbulence (see Real-life Experience section)
- AC 00-45E or AC 00-45F are recommended
- The student should be provided with several sample FDs to interpret in preparation for the FAA written exam.
Winds and Temperatures Aloft (FD) Highlights
- Issued every 6 hours
- Format: DDSSTT where wind direction (DD), wind speed (SS), and temperature (TT)
- Wind direction is TRUE, wind speed is in knots, and temperature
- No winds are reported within 1500′ of the station, and no temps are given within 2500′ of station
- 9900 = wind light (<5 knots) and variable
- Wind direction codes above 51 and 86 indicate winds over 100 knots. Subtract 50 to get the wind direction, and add 100 to the wind speed
Real-life advice and experience
- Winds aloft forecasts and predicting turbulence: expect vertical wind shear when winds on the FD increase >6 knots per 1000 ft.