FAA Sport Pilot Airplane (SPA)WeatherHard
A pilot is briefed that the winds and temperatures aloft forecast for 9,000 feet at a station reads '731749.' What are the forecast wind direction and speed at that altitude?
- A073° at 17 knots
- B731° at 49 knots
- C230° at 117 knots
- D180° at 73 knots
Show answer & explanationAnswer & explanation
Correct answer: C. 230° at 117 knots
The forecast group is coded as DDFF+TT. When the first two digits (DD) are 51 or greater, 50 is subtracted from DD and 100 is added to FF, indicating a wind of 100 knots or more. Here, DD=73 minus 50 = 23 (230°), and FF=17 plus 100 = 117 knots; TT=49 is the temperature (-49°C).
Why the other options are wrong
- A. This misreads the code without applying the +/-50/100 adjustment for high-speed winds.
- B. This incorrectly treats the whole 6-digit string as direction and speed without decoding.
- D. This does not correctly apply the FD decode rules for winds 100 knots or greater.
Winds and Temperatures Aloft Forecast (FB/FD) Decode
A 6-digit group (DDFFTT) reports forecast wind direction, speed, and temperature aloft; when DD is 51-99, subtract 50 from DD and add 100 to FF to decode winds of 100 knots or greater.
- Format: first 2 digits = direction (tens), next 2 = speed in knots, last 2 = temperature °C
- If DD ≥ 51, subtract 50 from DD and add 100 to FF
- Temperature is omitted for the 3,000-ft level and negative sign omitted below 24,000 ft
- Light and variable winds under 5 knots are coded as 9900
Memory trick: Above 50, Subtract 50, Add 100 — the hidden hundred trick.