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[start]
[q]What percentage of the atmosphere is oxygen?
[a]Answer:
When dry, 21%
[q]The troposphere is the layer that goes from the surface to approximately what average altitude?
[a]Answer:
About 7 miles; it varies with latitude and season. It slopes from 20,000 feet over the poles to 65,000 feet over the equator and is higher in summer than winter.
[q]How is the standard atmosphere determined?
[a]Answer:
average conditions throughout the atmosphere for all latitudes, seasons, and altitudes.
[q]Standard atmosphere at sea level is 15° and 29.92” Hg, by definition however, how would you describe what the standard atmosphere is?
[a]Answer:
The standard atmosphere is specified sea pressure level, temperature, and specific rates of change in temperature and pressure with height.
[q]The tropopause is of great interest to pilots of jet aircraft, the two reasons are?
[a]Answer:
there is an abrupt change in temperature lapse rate which affects the performance of a jet engine, and maximum winds (e.g. the jet stream) as well as narrow zones of wind shear are found at the tropopause.
[q]What is atmospheric pressure?
[a]Answer:
It is the force per unit-area exerted by the weight of the atmosphere.
[q]What is terrestrial radiation?
[a]Answer:
The Earth radiates energy, and this outgoing energy is terrestrial radiation.
[q]What percentage of the Sun’s energy is absorbed by Earth?
[a]Answer:
About 45%, the other 55% is reflected by the Earth and its atmosphere.
[q]Name the five temperature variations which create forces that drive the atmosphere in its endless motions:
[a]Answer:
Diurnal, seasonal, latitudinal, topographical and altitudinal
[q]What is diurnal variation?
[a]Answer:
It is the change in temperature from day to night brought about by the rotation of the Earth.
[q]What is a thermal low?
[a]Answer:
A dry, sunny region that becomes warm from intense surface heating, thus generating a surface low.
[q]What is the difference between pressure altitude and density altitude?
[a]Answer:
Pressure altitude is the height above the standard datum pressure (29.92” Hg, which is sea level under ISA). Density altitude is pressure altitude corrected for nonstandard temperatures. Density altitude is used for determining aerodynamic performance in the nonstandard atmosphere.
[q]When flying from high pressure to low pressure at constant indicator altitude and without adjusting the altimeter, do you gain or lose true altitude?
[a]Answer:
You lose true altitude.
[q]When flying into colder-than-standard temperatures are you at a higher or lower true altitude than what your altimeter indicates?
[a]Answer:
You are at a lower true altitude.
[q]What does 1013.2mb equate to in inches of mercury?
[a]Answer:
Standard atmospheric pressure at sea level is 1013.2 millibars, which is the equivalent of 29.92 inches of mercury.
[q]Does warmer air expand or contract?
[a]Answer:
Warmer air expands, becoming lighter and less dense than colder air.
[q]Is cooler air more or less dense than warmer air?
[a]Answer:
Cooler air is heavier and sinks, becoming denser than warmer air.
[q]Do closely spaced isobars indicate stronger or lighter winds?
[a]Answer:
The stronger the pressure-gradient force, the stronger the wind. Closely spaced isobars mean strong winds.
[q]What is a pressure-gradient force?
[a]Answer:
Pressure differences must create a force in order to drive the wind. The force is from higher pressure to lower pressure and is perpendicular to isobars or contours. This force is the pressure-gradient force.
[q]What is the jet stream and where is it found?
[a]Answer:
The jet stream is a narrow band of strong wind (by arbitrary definition, it has wind speeds of 50knts or greater) meandering through the atmosphere at a level near the tropopause. The jet stream is always found at a vertical break in the tropopause where the tropical and polar tropopauses meet.
[q]In the northern hemisphere, high pressure air circulates:
[a]Answer:
Outward, downward, and clockwise.
[q]Describe how the general circulation of air in the northern hemisphere from the equator to the poles is formed.
[a]Answer:
Warm air, forced aloft at the equator, moves north toward the pole and turns to the right (due to the Coriolis effect), becoming a westerly wind at about 30 lat. Cool polar air descends and makes its way towards the equator, it too shifts to the right and by the 60th degree latitude forms the polar easterlies. Air piles up at the 30t and 60th degrees latitude in both hemispheres. This creates a high-pressure belt that is the basis for a mid-latitude band of storms and weather.
[q]What are the 3 belts of prevailing winds in the northern hemisphere?
[a]Answer:
Polar easterlies (north of 60 degrees latitude), prevailing westerlies (between 30- and 60-degrees latitude) and trade winds (between the equator and the 30th degree latitude).
[q]What effect does surface friction have on wind?
[a]Answer:
Friction between the wind and the terrain surface slows the wind. The rougher the terrain, the greater the frictional force. Friction is an effective force and always acts to oppose wind direction.
[q]All else being equal, why is a wind blowing across isobars slower at the surface than aloft?
[a]Answer:
Friction between the wind and the terrain surface slows the wind.
[q]Does warm air hold more or less water vapor than cold air?
[a]Answer:
Warmer air holds more water vapor.
[q]The temperature is 58, and the dew point is 55. What could happen if the temperature drops?
[a]Answer:
When the temperature of the air is reduced to the dew point, the air is completely saturated and moisture begins to condense out of the air in the form of fog, dew, frost, clouds, rain, hail, or snow.
[q]What percentage of cloud cover is scattered?
[a]Answer:
Scattered cloud (SCT) is defined as 3/8 to 1/2 coverage. FEW is 1/8 to 1/4 coverage. BKN is 5/8 to 7/8 coverage, and OVC is full coverage.
[q]Describe the conditions for radiation fog.
[a]Answer:
Radiation fog usually occurs in high humidity, during the early evening, or on cool, cloudless nights with light winds, but it requires favorable topography.
[q]Describe advection fog.
[a]Answer:
Advection fog forms day or night as a result of moist air moving over a cold surface.
[q]Define a mountain wave.
[a]Answer:
A mountain wave occurs when air is blown over a mountain range or the ridge of a sharp bluff. Generally, it requires winds of 30 knots or greater but may occur with winds as slow as 15 knots. It creates strong updrafts or downdrafts on the lee side, which can cause turbulence up to 700 miles downrange. It may form lenticular clouds over peaks.
[q]CAT is best predicted where horizontal wind shear exceeds what values?
[a]Answer:
Expect and avoid areas of CAT where horizontal wind shear exceeds 40 knots per 150 NM.
[q]The winds aloft are 270/20. They shift to 210/15. Have you experienced frontal passage?
[a]Answer:
Yes, even though shifts are usually to the right after a passage. The question I got had to do with ground weather and frontal passage, low ceilings and heavy rain proceeding a cold front.
[q]What is a characteristic of a low-pressure system?
[a]Answer:
A low-pressure system is unstable and usually brings increasing cloudiness and precipitation.
[q]What kind of winds are associated with a warm front?
[a]Answer:
Warm fronts move slowly. Generally, the winds in a warm front are from 10–25 mph as opposed to cold fronts, which move much more quickly and experience wind gusts from 25–35 mph.
[q]What are the dynamics of a low-pressure system?
[a]Answer:
Air flows from areas of high pressure into areas of low pressure because air always seeks out lower pressure. In the northern hemisphere, the air flows toward a low and is deflected to create a counterclockwise or cyclonic circulation. The air flows into a low-pressure area to replace rising air. This air, therefore, tends to be unstable and usually brings increasing cloudiness and precipitation.
[q]What conditions are conducive to the formation of frost on an airplane?
[a]Answer:
Frost will tend to form on an airplane on a clear night with 30°F, light winds, and no precipitation. The temperature of the surface is at or below the dew point of the adjacent air and the dew point is below freezing.
[q]In level flight, you encounter icing conditions and you know your pitot heat is not working. What do you do?
[a]Answer:
Either descend or climb, but get out of icing conditions immediately. A completely blocked pitot tube due to an inoperative heater will cause the airspeed indicator to function like an altimeter.
[q]What is the worst icing condition?
[a]Answer:
Freezing rain (FZRA) and freezing drizzle (FZDZ) are the worst icing conditions.
[q]What type of icing will cause ice formation more quickly?
[a]Answer:
Clear ice forms more quickly. A condition favorable for rapid accumulation of clear ice is freezing rain below a frontal surface.
[q]What is the definition of severe icing?
[a]Answer:
When the rate of ice accumulation on an aircraft is such that de-icing/anti-icing equipment fails to reduce or control the hazard.
[q]Which precipitation type usually indicates freezing rain at higher altitude?
[a]Answer:
Ice pellets always indicate freezing rain at higher altitude.
[q]What type of weather report would you find CAT on?
[a]Answer:
Clear air turbulence forecast 3 and 6 hrs. US Forecast
[q]How can the stability of the atmosphere be determined?
[a]Answer:
The best indication of the stability or instability of an air mass is the ambient-temperature lapse rate.
[q]What are ATIS and METAR winds listed in: magnetic or true north?
[a]Answer:
METAR winds are given in tens of degrees from true north. ATIS information includes the time of the latest weather sequence including wind direction relative to magnetic north. All charts and textual sources use true north as the reference.
[q]Are METAR winds reported in relation to magnetic or true north?
[a]Answer:
True north. Remember, “If it’s written, it’s true” (except for the paint on the runway).
[q]You are at 25,000 ft, and there is Level 5 thunderstorm 80 miles in front of you. You tilt your radar up 1.5° and the cell disappears. How high is the thunderstorm cell?
[a]Answer:
1° of tilt raises or lowers the beam 1000 feet at a distance of 10 miles. Thus, at 80 miles, 1.5° of tilt equals 12,000 ft. Add that to the 25,000 ft you are flying at, and the thunderstorm cell is 37,000 ft high, approximately.
[q]What shows up best on radar? Rain, Hail, Sleet, Snow.
[a]Answer:
Technically, wet hail has the highest reflectivity of any precipitation. For the given choices, however, rain is the most reflective.
[q]Are squall lines typically found ahead of cold or warm fronts?
[a]Answer:
Squall lines are typically associated with cold fronts. However, squall lines can form during the summer months as far as 200 miles in advance of a severe cold front.
[q]Adiabatic changes to air imply:
[a]Answer:
No heat is removed from or added to the air as it expands or contracts.
[q]A process of cooling the air through expansion is better known as:
[a]Answer:
Adiabatic cooling
[q]CAT associated with mountain waves can extend how high?
[a]Answer:
Mountain-wave CAT can extend 5,000 feet above the tropopause and can travel 100 or more miles downwind from the mountains.
[q]Mountain waves can produce a stationary cloud group of rotor clouds and standing lenticular clouds. Of the two, which are usually found at lower altitudes?
[a]Answer:
Rotor clouds are likely to be the lowest.
[q]The most hazardous area or zone caused by wind shear is typically found in this area around a thunderstorm:
[a]Answer:
On all sides and directly underneath the cell
[q]After passing into a cold front, will atmospheric pressure typically increase or decrease?
[a]Answer:
When crossing a front directly into colder air, the pressure will usually rise.
[q]Freezing rain encountered during a climb is usually indicative of what?
[a]Answer:
A layer of warmer air above; rain or drizzle always forms in temperatures above freezing. Rain or drizzle falling through colder air may become super-cooled, freezing on impact as freezing rain.
[q]In what condition will snowflakes form?
[a]Answer:
Snowflakes are formed by sublimation in below-freezing temperatures.
[q]What is the definition of wind shear?
[a]Answer:
Any rapid change in wind direction or velocity which causes airspeed changes greater than 15 knots or vertical-speed changes greater than 500 feet per minute.
[q]How far should you fly around a thunderstorm?
[a]Answer:
avoid any thunderstorms identified as severe or giving an intense radar echo by at least 20 miles if circumnavigating or, if flying over the top, clear the top of the storm by 1000 feet for every 10 knots of wind speed at the top of the storm.
[q]What is a microburst? What is a dry microburst?
[a]Answer:
Microbursts are small-scale intense downdrafts which, on reaching the surface, spread outward in all directions from the downdraft center. A dry microburst often generates a ring of dust on the surface. A microburst is defined as damaging winds extending to 2.2 miles or less horizontally.
[q]What are the parameters that define wind shear?
[a]Answer:
Wind shear is defined as “any rapid change in wind direction or velocity.” Severe wind shear is defined as a rapid change in wind direction or velocity, causing airspeed changes greater than 15 knots or vertical-speed changes greater than 500 feet per minute.
[q]You experience wind shear on final descent, what is the best course of action?
[a]Answer:
While aircraft procedures may vary, the pilot on experiencing severe wind shear should maintain or increase pitch attitude, increase power to the maximum available and accept lower-than-normal airspeed indications. If this does not arrest the descent, the pilot should continue to pitch up until the descent does stop or until the “stick shaker” is encountered.
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