PPL Checkride

flow of air around low pressure systems NHem

inward, upward, CCW

flow of air around high pressure systems NHem

outward, downward, CW

low-pressure system weather

rising air = cloudiness, precipitation, bad weather

high-pressure system weather

descending air = dissipation of clouds, good weather

cold front

occurs when a mass of cold, dense, and stable air advances and replaces a body of warm air

frontal occlusion

when a fast-moving cold front catches up with a slow-moving warm front

warm front

boundary area formed when a warm air mass contacts and flows over a colder air masss

stationary front

when the forces of two air masses are relatively equal, the boundary that separates them is stationary and influences the weather for days

cold front weather

towering cumulus, heavy rain/thunderstorms, hail, tornadoes, poor visibility, variable & gusting winds, temperature/dew point/pressure drop rapidly

warm front weather

stratiform clouds, drizzle, low ceilings, poor visibility, variable winds, rise in temperature

trough

low pressure area, rising air = cloudiness & precipitation

ridge

high pressure area; descending air = dissipation of clouds

standard temperature and pressure

15°C and 29.92 inHg

isobar

a line on a weather chart which connects area of equal or constant pressure

isobars are close together means

steep pressure gradient = higher wind speeds

what causes the winds aloft to flow parallel to the isobars?

Coriolis force

why do surface winds generally flow across the isobars at an angle?

surface friction

rate of atmospheric pressure change with altitude

1inHg lower per 1000 ft higher

dew point

the temperature to which a sample of air must be cooled to attain the state of saturation

when temperature and dew point are within 5°C, what is the weather?

moisture (clouds, dew, fog) & potential for carburetor icing

what determines the type and vertical extent of clouds?

stability of the atmosphere

stable atmosphere makes vertical movement

difficult; tamps out disturbances

unstable atmosphere makes vertical movement

easy and multiplying; small vertical movements become larger = turbulence and severe weather

stable clouds

stratiform

stable turbulence

smooth

stable precipitation

steady

stable visibility

fair to poor

unstable clouds

cumuliform

unstable turbulence

rough

unstable precipitation

showery

unstable visibility

good

heavier precipitation means

thicker clouds (at least 4000ft to have significant precipitation)

what meteorological information should you be aware of in regard to icing?

location of fronts, cloud layers, freezing levels, air temperature and pressure

freezing level

the lowest altitude in the atmosphere over a given location at which the air temp reaches 0°C

how to determine freezing level

current icing products (CIP) and forecast icing products (FIP) + all other weather info

when does structural icing occur

visible moisture and below freezing temp at point moisture strikes aircraft

main types of icing in flight

structural, induction system, instrument

types of structural icing

clear ice (smooth sheet of ice), rime ice (drops freeze on impact), mixed ice (rough accumulation)

factors required to form a thunderstorm

unstable air, sufficient water vapor, a lifting force

cumulus stage of a thunderstorm

updrafts = raindrops get bigger

mature stage of a thunderstorm

rain, downdrafts & updrafts, lightning

dissipating stage

downdrafts and rain dissipation

temperature inversion

increase in temperature with altitude; poor visibility, stable air; warm rain falls through cold air (icing potential)

radiation fog

ground cools the calm air

advection fog

warm air over a cold surface (warm coastal air blowing over cold winter surface)

upslope fog

moist, stable air cools as it moves up terrain (dense)

wind shear

rate of wind velocity per unit distance

wind shear occurs

low-level temperature inversion, frontal zone or thunderstorm, clear air turbulence (CAT) caused by jet stream

primary way to obtain weather brief

FSS

HIWAS

Hazardous In-flight Weather Advisory Service = summarized flight conditions (indicated with “H” on sectional)

flight information service - broadcast (FIS-B)

ground broadcast service that goes to avionics; should not be relief on to avoid hazard areas (up to 15 min delay)

en route sources of weather

FSS on 122.2, ATIS, HIWAS, FIS, ATC (workload permitting)

METAR

hourly surface observation of conditions at an airport

SPECI

special METAR report to update for rapidly changing weather conditions, aircraft mishaps, or other info

AWOS

Automated Weather Observing System

ASOS/AWSS

Automated Surface Observing System/Automated Weather Sensor System

terminal aerodrome forecast

expected meteorological conditions for a specified time period within 5 SM

aviation area forecast (FA)

forecast of a specified weather phenomena covering a flight information region (3 times a day)

graphical forecast for aviation (GFA)

complete picture of weather over CONUS

convective SIGMET (WST)

severe or greater turbulence, severe icing, low-level wind shear; issued hourly

SIGMET (WS)

advises weather that is potentially hazardous to all aircraft (normal = 4 hours validity, ash or cyclones = 6 hr)

AIRMET (WA)

describe conditions at intensities lower than SIGMET for all pilots; issued every 6 hr

AIRMET Sierra

describes IFR conditions and/or extensive mountain obscurations

AIRMET Tango

describes moderate turbulence, sustained surface winds >= 30kts, and/or nonconvective low-level wind shear

AIRMET Zulu

describes moderate icing and provides freezing level heights

winds and temperatures aloft forecasts (FB)

wind direction, speed, temp at specified times, altitudes, locations; 4 times daily

wind speeds of 100-199kts can be read by

subtract 50 from coded direction and add 100 to coded speed (7545 = 250 deg at 145 kts)

Center Weather Advisory (CWA)

used to anticipate and avoid adverse weather conditions; reflects current conditions or is short-term (2hr) forecast

surface analysis chart

surface weather observations: sea level pressures, positions of highs/lows/ridges/troughs/fronts; 8 times daily

weather depiction chart

plot of weather conditions at selected METAR stations and analysis of weather flying category; designed to alert pilots of critical operational minimums at terminals; 8 times daily

LIFR (Low)

ceiling < 500ft and/or viz < 1 SM

IFR

ceiling < 1000ft and/or viz 1-3 SM

MVFR (Marginal)

ceiling 1000-3000 ft and/or vis 3-5 SM

VFR

ceiling > 3000 ft and viz > 5 SM

short-range prognostic charts

forecast of surface pressure systems, fronts, and precipitation for a 2.5 day period; 4 times a day

low-level significant weather chart (SIGWX)

forecast of aviation weather hazards for pre-flight guidance; 4 times a day at 12hr and 24hr prog; below Flight Level 250

mid-level significant weather chart (SIGWX)

forecast of en route weather phenomena from 10000ft MSL to FL450; 4 times a day at 24hr prog

convective outlook chart

areas forecast for severe (tornado, wind gusts >= 50kts, hail >= 3/4in diameter) and non-severe convection and specific severe weather for the following 3 days

constant pressure analysis charts

upper air weather map where info is given in terms of pressure; 850 mb = 5000 ft, 700 mb = 10000ft…

4 aerodynamic forces

lift, gravity, drag, thrust

opposing aerodynamic forces are equal when

in steady-state, straight and level, unaccelerated flight

angle of incidence

formed by longitudinal axis and chord of wing; measured by the angle at which the wing is attached to fuselage

relative wind

direction of the airflow with respect to the wing

angle of attack

angle between the wind chord line and the direction of the relative wind

Bernoulli’s Principle

pressure of a fluid decreases when its speed increases

factors that affect lift and drag

wing area, shape of airfoil, angle of attack, velocity of air, air density

torque effect

engine and prop are revolving in one direction and equal force is trying to rotate plane in opposite direction

when is torque effect greatest

low airspeeds with high power settings and a high angle of attack

torque reaction of the engine and propeller

rotation of the propeller to the right tends to roll or bank the airplane to the left (N3L)

gyroscopic effect of the propeller

gyroscopic precession

corkscrewing effect of the propeller slipstream

corkscrewing rotation to the slipstream that impacts the tail surface on the left and yaws the airplane to the left

asymmetrical loading of the propeller (P-factor)

more thrust produced on downward moving blade so airplane yaws left

load factor

ratio of total load supported by airplane’s wings to actual weight of airplane and content (expressed in Gs)

increased load factor increases

stalling speed

things that increase load factor

level turns, turbulence, speed

maximum safe load factors for normal airplanes

+3.8 to -1.52

maximum safe load factors for utility airplanes

+4.4 to -1.76

maximum safe load factors for aerobatic airplanes

+6.0 to -3.0

maneuvering speed

maximum speed at which the limit load can be imposed without causing structural damage; move single flight control to full deflection

maneuvering speed increases with

an increase in weight