FAA Private Pilot Test Prep - Chapter 6: Weather
At approximately what altitude above the surface would the pilot expect the base of cumuliform clouds if the surface air temperature is 82 degrees F and the dewpoint is 38 degrees F?
10,000 feet AGL.
(Refer to Figure 20.) Over which area should a glider pilot expect to find the best lift under normal conditions.
2.
A pilot can expect a wind shear zone in a temperature inversion whenever the windspeed at 2,000 4,000 feet above the surface is at least
25 knots.
What is the approximate base of the cumulus clouds if the surface air temperature at 1,000 feet MSL is 70 degrees F and the dewpoint is 48 degrees F?
6,000 feet MSL.
Which is true with respect to a high- or low- pressure system?
A high-pressure area or ridge is an area of descending air.
What feature is associated with a temperature inversion?
A stable layer of air.
What measurement can be used to determine the stability of the atmosphere?
Actual lapse rate.
What types of fog depend upon wind in order to exist?
Advection fog and upslope fog.
In which situation is advection fog most likely to form?
An air mass moving inland from the coast in winter.
Where does wind shear occur?
At all altitudes, in all directions.
If an unstable air mass is forced upward, what type clouds can be expected?
Clouds with considerable vertical development and associated turbulence.
What feature is normally associated with the cumulus stage of a thunderstorm?
Continuous updraft.
What are the characteristics of a moist, unstable air mass?
Cumuliform clouds and showery precipitation.
What clouds have the greatest turbulence?
Cumulonimbus.
During the life cycle of a thunderstorm, which stage is characterized predominately by downdrafts?
Dissipating.
During which period is a sea breeze front most suitable for soaring flight?
During the afternoon.
What are the processes by which moisture is added to unsaturated air?
Evaporation and sublimation.
If the temperature/dewpoint spread is small and decreasing, and the temperature is 62 degrees F, what type of weather is most likely to develop?
Fog or low clouds.
In which environment is aircraft structural ice most likely to have the highest accumulation rate?
Freezing rain.
How does frost affect the lifting surfaces of an airplane on takeoff?
Frost may prevent the airplane from becoming airborne at normal takeoff speed.
Why is frost considered hazardous to flight?
Frost spoils the smooth flow over the air over the wings, thereby decreasing lifting capability.
How will frost on the wings of an airplane affect takeoff performance?
Frost will disrupt the smooth flow if air over the wing, adversely affecting its lifting capability.
What conditions are necessary for the formation of thunderstorms?
High humidity, lifting force and unstable conditions.
When may hazardous wind shear be expected?
In areas of low level temperature inversion, frontal zones, and clear air turbulence.
Upon encountering severe turbulence, which flight condition should the pilot attempt to maintain?
Level flight attitude.
Which weather phenomenon is always associated with a thunderstorm?
Lightning.
A stable air mass is most likely to have which characteristic?
Poor surface visibility.
Which weather phenomenon signals the beginning of the mature stage of a thunderstorm?
Precipitation beginning to fall.
Which weather conditions should be expected beneath a low-level temperature inversion layer when the relative humidity is high?
Smooth air, poor visibility, fog, haze, or low clouds.
Low-leel turblence can occur and icing can become hazardous in which type of fog?
Steam fog.
What is a characteristic of stable air?
Stratiform clouds.
What is the proper airspeed to use when flying between thermals on a cross-country flight against a headwind?
The best lift/drag speed increased by one-half the estimated wind velocity.
Which conditions result in the formation of frost?
The temperature of the collecting surface is at or below the dewpoint of the adjacent air and the dewpoint is below freezing.
What is meant by the term "dewpoint"?
The temperature to which air must be cooled to become saturated.
What cloud types would indicate convective turbulence?
Towering cumulus clouds.
What are characterictis of unstable air?
Turbulence and good surface visibility.
What causes variations in altimeter settings between weather reporting points?
Unequal heating of the Earth's surface.
What situation is most conductive to the formation of radiation fog?
Warm, moist air over low, flatland areas on clear, calm rights.
What would decrease the stability of an air mass?
Warming from below.
Which is considered to be the most hazardous condition when soaring in the vicinity of thunderstorms?
Wind shear and turbulence.
If there is thunderstorm activity in the vicinity of an airport at which you plan to land, which hazardous atmospheric phenomenon might be expected on the landing precipitation?
Wind-shear turbulence.
One of the most easily recognized discontinuities across a front is
a change in temperature.
An almond or lens-shaped cloud which appears stationary, but which may contain winds of 50 knots or more, is referred to as
a lenticular cloud.
The suffix "nimbus," used in naming clouds, means
a rain cloud.
The amount of water vapor which air can hold depends on the
air temperature.
When there is a temperature inversion, you would expect to experience
an increase in temperature as altitude increases.
One of the most dangerous features of mountain waves is the turbulent areas in and
below rotor clouds.
Convective circulation patterns associated with sea breezes are caused by
cool, dense air moving inland from over the water.
Moisture is added to air by
evaporation and sublimation.
The wind at 5,000 feet is southwesterly while the surface wind is southerly. The difference in direction is primarily due to
friction between the wind and the surface.
Every physical process of weather is accompanied by, or is the result of, a
heat exchange.
Clouds are divided into four families according to their
height range.
The presence of ice pellets at the surface is evidence that there
is a temperature inversion with freezing rain at a higher altitude.
Thunderstorms reach their greatest intensity during the
mature stage.
When warm, moist, stable air upslope, it
produces stratus type clouds.
The development of thermals depends upon
solar heating.
Thunderstorms which generally produce the most intense hazard to aircraft are
squall line thunderstorms.
A nonfrontal, narrow band of active thunderstorms that often develop ahead of a cold front is known as a
squall line.
Crests of standing mountain waves may be marked by stationary, lens-shaped clouds known as
standing lenticular clouds.
Steady precipitation preceding a front is an indication of
stratiform clouds with little or no turbulence.
The most frequent type of ground or surface-based temperature inversion is that which is produced by
terrestial radiation on a clear, relatively still night.
The mature stage of a thunderstorm begins with
the start of precipitaion.
The conditions necessary for the formation of cumulonimbus clouds are a lifting action and
unstable, moist air.
During a cross-country flight you picked up rime icing which you estimate is 1/2'' thick on the leading edge of the wings You are now below the clouds at 2,000 feet AGL and are approaching your destination airport under VFR. Visibility under the clouds is more important than 10 miles, winds at the destination airport are 8 knots right down the runway, and the surface temperature is 3 degrees C. You decide to:
use a faster than normal approach and landing speed.
One in-flight condition necessary for structural icing to form is
visible moisture.
Clouds, fog, or dew will always form when
water vapor condenses.
One weather phenomenon which will always occur when flying across a front is a change in the
wind direction.
If a temperature inversion is encounreted immediately after takeoff or during an approach to a landing, a potential hazard exists due to
wind shear.
