NCAA PPL Meteorology flashcards
NCAA PPL Meteorology · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Standard sea-level pressure
- 29.92 inHg or 1013.2 hPa, the reference pressure for the standard atmosphere and the value set in the altimeter window when flying at or above the transition altitude.
- Standard temperature lapse rate
- Temperature decreases 2 °C per 1,000 ft in the standard atmosphere up to the tropopause, used to estimate freezing levels and ISA deviations.
- Pressure altitude
- Indicated altitude corrected for the difference between the current altimeter setting and 29.92 inHg; it is the altitude used for density altitude and performance charts.
- Density altitude
- Pressure altitude corrected for nonstandard temperature; high density altitude reduces engine power, propeller thrust, and wing lift, increasing takeoff and landing distances.
- Altimeter high-to-low error
- Flying from high pressure toward low pressure without resetting the altimeter causes the aircraft to fly lower than the altimeter indicates, roughly 1,000 ft per 1 inHg.
- Cold temperature altimeter error
- Cold air shrinks pressure levels, so the true altitude is lower than indicated; apply cold-temperature corrections when operating near terrain in winter.
- Ceiling definition
- The height of the lowest broken or overcast layer, or the vertical visibility into an obscuration; a ceiling below 1,000 ft AGL generally means IFR conditions.
- Sky cover abbreviations
- FEW means 1-2 oktas, SCT 3-4, BKN 5-7, and OVC 8 oktas; VV indicates an obscured sky with indefinite ceiling.
- Cloud base estimate
- Estimate convective cloud bases in feet AGL by multiplying the surface temperature-dew point spread in °C by 400; a 10 °C spread gives about 4,000 ft.
- Freezing level estimate
- Divide the surface temperature in °C by 2 and multiply by 1,000 ft to estimate the freezing level, assuming the standard lapse rate.
- METAR wind format
- Wind is reported in degrees true and knots, with gusts shown as G; VRB means variable direction and 00000KT means calm.
- METAR visibility units
- United States METARs report visibility in statute miles (for example 10SM); many international reports use meters, so convert before comparing to VFR minimums.
- TAF change groups
- FM indicates a rapid change at a specific time; TEMPO indicates temporary fluctuations; BECMG indicates a gradual change over a period.
- AIRMET coverage
- AIRMETs cover moderate hazards: moderate turbulence, moderate icing, IFR conditions, mountain obscuration, and sustained surface winds of 30 kt or more.
- SIGMET coverage
- SIGMETs cover severe or extreme hazards such as severe turbulence, severe icing, and volcanic ash; convective SIGMETs address thunderstorms and large hail.
- PIREP purpose
- A pilot report provides direct in-flight observation of turbulence, icing, cloud tops, and visibility; it is the only real-time confirmation of these conditions.
- Stable air characteristics
- Stable air produces stratiform clouds, steady precipitation, smooth air, and haze, because vertical motion is suppressed and moisture spreads horizontally.
- Unstable air characteristics
- Unstable air produces cumuliform clouds, showery precipitation, turbulence, and good visibility between showers, because vertical motion is strong.
- Temperature inversion effects
- An inversion traps haze and moisture below it, gives smooth air, and can create wind shear at its top; fog often forms under a nocturnal inversion.
- Structural icing conditions
- Structural icing requires visible moisture and temperatures between 0 °C and about −20 °C; freezing rain is the most dangerous because supercooled drops freeze rapidly on impact.
- Carburetor icing range
- Carburetor icing can occur at outside air temperatures between roughly −7 °C and +21 °C with high humidity; carburetor heat raises the mixture temperature.
- Thunderstorm life cycle
- The cumulus stage has updrafts, the mature stage has both updrafts and downdrafts with hail and lightning, and the dissipating stage is downdraft-dominated.
- Microburst hazard
- A microburst downdraft spreading along the surface produces a headwind then tailwind shear on approach, causing sudden airspeed loss and sink.
- Radiation fog formation
- Radiation fog forms on clear, calm nights over land as the surface cools and the air reaches saturation; it usually dissipates a few hours after sunrise.
- Advection fog formation
- Advection fog forms when warm, moist air moves over a colder surface, cooling to saturation; it can persist as long as the wind and temperature contrast continue.
- Mountain wave indicators
- Lenticular clouds, rotor clouds, and standing waves indicate mountain wave activity; expect severe turbulence and strong downdrafts on the lee side of ridges.
- Cold front passage
- A cold front brings a rapid wind shift, temperature drop, pressure rise, narrow bands of heavy showers, and improving visibility behind the front.
- Warm front passage
- A warm front brings gradual temperature rise, falling pressure, lowering ceilings, and steady precipitation with reduced visibility ahead of the surface front.
- Wind shear definition
- Wind shear is a change in wind speed or direction over a short distance, commonly found near fronts, thunderstorms, inversions, and surface obstructions.
- Coriolis and surface friction
- Surface friction causes wind to cross isobars toward low pressure; aloft, away from friction, wind blows nearly parallel to the isobars.
- Buys Ballot's law
- In the Northern Hemisphere, standing with your back to the wind puts lower pressure on your left, helping orient the aircraft relative to pressure systems.
- Class E VFR cloud clearance
- Below 10,000 ft MSL in Class E, VFR requires 3 statute miles visibility and 1,000 ft above, 500 ft below, and 2,000 ft horizontal from clouds.