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Weather

METARs and TAFs, density altitude, wind, fog and thunderstorms.
29 practice questions

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Weather questions cover where to find aviation weather and how it affects a small drone. Start with the two rules: you need at least 3 statute miles of visibility from the control station, and you must stay at least 500 feet below and 2,000 feet horizontally from clouds (14 CFR 107.51).

Reports and forecasts

A METAR is a report of current surface weather at an airport in a standard international format; a SPECI is a special report issued between routine ones when conditions change (FAA Remote Pilot Study Guide, p. 15). Times are in UTC, shown with a "Z" (FAA Remote Pilot Study Guide, p. 16-18). A TAF is a forecast for the area within 5 statute miles of an airport, valid for 24 or 30 hours and written with the same codes as a METAR (FAA Remote Pilot Study Guide, p. 18).

Density altitude

Thinner air means worse performance. High elevation, low pressure, high temperature and high humidity all raise density altitude and reduce how well an aircraft performs (FAA Remote Pilot Study Guide, p. 21).

Wind

Buildings and terrain break up the wind and create gusts that change quickly in speed and direction (FAA Remote Pilot Study Guide, p. 23). Wind shear is a sudden change in wind speed or direction over a small area, and a microburst, its most severe low-level form, can produce downdrafts of up to 6,000 feet per minute (FAA Remote Pilot Study Guide, p. 23-24).

Stability, fog and frost

Stable air tends to bring stratiform clouds, fog, smooth air and poor visibility in haze; unstable air brings cumuliform clouds, showers, turbulence and good visibility (FAA Remote Pilot Study Guide, p. 26). When temperature and dew point are close together, fog and low clouds are likely (FAA Remote Pilot Study Guide, p. 25). Frost reduces lift and increases drag, so clean it off before flying (FAA Remote Pilot Study Guide, p. 25).

Thunderstorms

A thunderstorm cell goes through three stages: cumulus, mature and dissipating. Every hazard is at its worst in the mature stage (FAA Remote Pilot Study Guide, p. 26-27). Don't fly near rapidly building cumulus clouds (FAA Remote Pilot Study Guide, p. 27).

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Practice questions

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Questions 1-10 of 29

  1. Question 1 of 29

    During preflight planning you find a convective SIGMET in effect for your area. What kind of weather does this advisory warn about?

  2. Question 2 of 29

    You fly the same small unmanned aircraft at different sites. Which conditions would give the highest density altitude and the weakest performance?

  3. Question 3 of 29

    On a calm, clear evening, a nearby METAR shows the temperature/dew point group 09/08, and the air is still cooling. What should you be alert for?

  4. Question 4 of 29

    On a warm day the air becomes very humid. Compared with dry air at the same temperature and pressure, how does this affect your small UA?

  5. Question 5 of 29

    A METAR reports the sky condition as SCT015 BKN040 OVC080. For aviation purposes, what is the ceiling?

  6. Question 6 of 29

    A METAR from an airport in the 48 contiguous states contains the group 140855Z. What does this group tell you?

  7. Question 7 of 29

    Between two routine METARs, an airport weather station sends out a report labeled SPECI. What is a SPECI?

  8. Question 8 of 29

    The weather briefing describes a stable air mass over your flying area. Which set of conditions is typical of stable air?

  9. Question 9 of 29

    The forecast visibility in a TAF is written as P6SM. What visibility does the forecaster expect?

  10. Question 10 of 29

    Rain from a growing thunderstorm cell begins reaching the ground, showing that a downdraft has formed. Which stage of its life cycle has the cell entered?

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