Part 107 Study Guide
Weather & METARs
Decode METARs and TAFs, understand density altitude, wind shear, fog formation, and how weather affects sUAS operations. Know Part 107 visibility and cloud clearance minimums.
38 questions in this topic
Sample Questions
In the METAR observation 'METAR KJFK 121856Z 21015G25KT 3SM BR OVC007 04/02 A2990', what does 'BR' indicate?
BR is the abbreviation for mist (from French 'brume'), indicating visibility between 5/8 and 6 statute miles. FG (fog) is used when visibility drops below 5/8 SM. AIM 7-1-30.
💡 Memory tip
BR = 'brume' (French for mist). Still flyable but marginal — like driving in light drizzle. FG (fog) kicks in below 5/8 SM when visibility gets dangerous.
A temperature/dewpoint spread of 3°F and decreasing suggests:
When the temp/dewpoint spread narrows toward zero, the air is nearing saturation. Fog, mist, or low clouds are likely, especially during cooling evening hours. FAA-G-8082-22 Ch. 9.
💡 Memory tip
Think of dew point as the temperature at which air 'gives up' holding water. When temperature drops to meet it, the air saturates and you get fog or low clouds.
What weather phenomenon poses the greatest risk to a small UAS operating below 400 ft AGL?
At low altitudes, mechanical turbulence from buildings, terrain, and tree lines creates unpredictable gusts that can overwhelm sUAS flight controllers. Jet stream and CAT occur well above Part 107 operating altitudes. FAA-G-8082-22 Ch. 9.
💡 Memory tip
Below 400 ft, you're flying in the turbulence shadows of buildings, trees, and terrain. Jet streams and CAT are irrelevant — the local eddies are what will flip your drone.
In a METAR, the altimeter setting 'A2992' means the barometric pressure is:
The 'A' prefix indicates inches of mercury (inHg). A2992 = 29.92 inHg, which is standard sea-level pressure. International METARs use Q prefix with hectopascals (Q1013 = standard). AIM 7-1-30.
Density altitude increases with:
Density altitude rises when it's hot, humid, and at high elevation — the 3 H's: High, Hot, Humid. This means thinner air and degraded performance for both manned and unmanned aircraft. FAA-G-8082-22 Ch. 9.
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Start Full Practice ExamWeather & METARs FAQ
What are the Part 107 weather minimums? ▾
Under 14 CFR 107.51, the remote PIC must ensure: visibility at least 3 statute miles from the control station, and at least 500 ft below, 2,000 ft horizontally from, and 300 ft above any cloud. These are minimum conditions — exercise greater caution as appropriate.
What does OVC007 mean in a METAR? ▾
OVC007 means overcast cloud layer at 700 feet AGL (the number represents hundreds of feet). An overcast layer is sky coverage of 8/8. For sUAS operations with a 400 ft AGL ceiling, a 700 ft overcast would require the pilot to stay 300 ft below it (max 400 ft AGL).
How does high density altitude affect drone performance? ▾
High density altitude (hot, humid, or high-elevation conditions) reduces air density, decreasing rotor/propeller efficiency and battery discharge rate. The drone's actual performance (hover time, maximum thrust) is lower than in standard conditions. 14 CFR 107.49 requires evaluating operating environment.