1
Q
How can thunderstorms affect an aircraft?
A
Severe turbulence.
Strong vertical wind.
Hail/ice/heavy rain.
Lightning.
Rapid pressure variation.
Instrument malfunction.
Structural damage.
2
Q
What distance are pilots recommended to avoid weather returns on a weather radar by?
A
At least 20nm laterally or at least 5000ft vertically above the cloud top.
3
Q
In adverse weather conditions, what should the controller do?
A
Advise when CB clouds are ahead.
Advise location, intensity, and direction.
Give alternate route where possible (inform if leaving CAS and provide appropriate service.
Issue clearance to re-join CAS if necessary.
Ask when pilot can accept vectors after weather avoidance.
4
Q
Where might severe turbulence be encountered?
A
In or adjacent to cloud (especially cumulus and CB).
Over and adjacent to frontal systems.
In jet streams.
Over high terrain (mountain waves).
5
Q
How can severe turbulence affect an aircraft?
A
Possible structural damage.
Injury to occupants.
Controlling difficulties.
6
Q
What are some of the sources of meteorological information?
A
Met authority e.g. Met office.
Designated forecast offices.
Radar.
Pilot reports.
Official/unofficial observations.
7
Q
What is AFTN and what does it do?
A
Aeronautical Fixed Telecoms Network.
Worldwide system of aeronautical fixed circuits that exchange messages and/or digital data between aeronautical fixed stations.
8
Q
What is OPMET?
A
Operational Meteorological Information.
For use in preparatory or in-flight planning of flight operations.
9
Q
What sort of information does the MWO provide?
A
TAFs, aerodrome warnings, Speci’s, SIGMETs, forecast regional pressure settings, temperature inversion warnings and windshear alerts.
10
Q
What sort of information does the UK Met Office provide?
A
UK and NW Europe low level weather and spot wind forecast charts.
Main forecast weather chart and text.
Temp forecast charts.
European medium/high level spot winds.
11
Q
What sort of information does WAFCs provide?
A
Real time met info.
UK met office uses SADIS.
AFTN.
OPMET.
12
Q
What conditions could trigger an aerodrome warning?
A
Strong winds/gales/gusts.
Snow.
Fog.
Thunderstorms.
Hail.
Freezing precipitation.
Temperature inversion.
13
Q
What is temperature inversion?
A
An increase in temperature of 10 degrees or more in lowest 10000ft.
14
Q
What is a SPECI?
A
Special report that is issued between routine reports.
15
Q
What’s included in a SPECI?
A
Surface wind, surface visibility, weather, cloud, pressure, temperature and severe icing and/or turbulence.
16
Q
What is CAVOK and it’s conditions to be met?
A
Cloud and visibility OK.
- Prevailing visibility more than 10km.
- No min. vis. reported.
- No cloud reported under 5000ft or below MSA, whichever is greatest.
- No towering cumulus or CB clouds.
- No significant weather phenomena at or in the vicinity of an aerodrome.
17
Q
What is prevailing visibility?
A
Visibility value that is reached or exceeded within at least half of the horizon.
18
Q
What is RPS?
A
Regional Pressure Setting.
Conservative forecast of the lowest QNH value within an altimeter setting region (ASR).
19
Q
How often are RPS values made?
A
Hourly for the period H+1 to H+2.
Given in hPa.
20
Q
What is a SIGMET?
A
Significant Meteorological report.
Weather advisory for hazardous weather that may affect safety of aircraft in flight.
21
Q
List the SIGMETS.
A
Thunderstorms.
Heavy hail.
Freezing rain.
Severe icing.
Severe turbulence.
Severe mountain waves.
Tropical cyclone.
Heavy dust/sandstorm.
Volcanic ash cloud.
22
Q
When should aircraft in flight be warned of any SIGMET phenomena?
A
Up to 500nm or 2 hours flying time for the route ahead.
23
Q
How long are SIGMETs valid for?
A
Typically 4 hours (can be 6 for volcanic ash and cyclones).
24
Q
What is GAMET?
A
General Aviation Meteorological Forecast.
Abbreviated plain text forecast designed for low level general aviation users who operate over the UK.
(GAMETs have been replaced by AIRMETs)
25
How strong would the wind or a gust be to warrant a strong wind warning?
Wind with a mean speed of at least 15kts or gusts of at least 28kts in an area covered by the forecast.
26
At what 1000's of ft are spot values given for select locations regarding wind and temperatures?
1000, 3000 and 6000ft.
27
How long do Regional Outlooks forecasts last for?
6 hours following the end of the validity period.
28
How long do UK Extended Outlooks forecasts last for?
24 hours following the end of the regional outlook forecast.
29
What is a NOTAM?
Notice to Aviation.
Changes of a temporary nature and of a short duration, or operationally significant permanent changes or temporary changes of a long duration made at short notice, are published via NOTAM.
(N=New, R=Replaces previous, C=Cancels previous).
30
What is a SNOWTAM?
Notifications of runway/taxiway/apron status and issued by the airport authority.
Issued when operationally significant and 24 hours maximum validity.
31
What is an ASHTAM?
Notification of an operationally significant change in volcanic ash or other dust contamination.
32
What is a BIRDTAM?
Information regarding bird strike risk, particularly for low level airspace.
33
What is a VAAC?
Volcanic Ash Advisory Centre.
An ICAO designated centre, responsible for issuing advisories for volcanic eruptions originating in the areas that centre specifically covers.
34
What impact can volcanic ash have on an aircraft?
Extremely abrasive - cause significant wear to engines.
Cockpit windows scratched - impair visibility.
May contaminate fuel/water systems, jam gears and cause engine flameout.
Can contaminate cabin and damage avionics.
35
Which CAP document provides guidance for flight operations in the vicinity of volcanic ash?
CAP 1236.
36
What type of report will Special Aircraft Observations be passed to ATC in?
Special Air-Reports.
37
What conditions would be reported in a Special Air-Report?
MOD ICE/SEV ICE.
MOD TURB/SEV TURB.
SEV MTW.
TSGR/TS (With/without hail).
VA CLD/VA.
Any volcanic activity.
38
What is Temperature Inversion?
Condition where the atmospheric temperature increases with altitude in contrast to the normal decrease in altitude.
39
Where might temperature inversion occur?
During clear nights, passage of a front or anticyclones giving rise to warm sinking air.
40
When is a marked temperature inversion warning issued?
When a temperature differential of 10 degrees or more is present in the lowest levels of the atmosphere up to 1000ft above ground level.
41
Does a headwind impact and aircraft's rate of climb?
No. It appears to have a higher rate of climb but it doesn't actually change.
They achieve the same altitude gain over a shorter horizontal distance.
42
What is a stationary front?
Forms when a cold or warm front stops moving.
Occurs when both air masses push against one another, but neither is powerful enough to move the other.
43
What direction of wind helps a stationary front stay in place?
Wind blowing parallel to the front instead of perpendicular.
44
What is the effect of solar radiation?
Severe space weather events can generate a degradation or loss of satellite-based and/or ground-based navigation and/or communications systems.
45
What might a pilot do if they experience solar radiation?
Pilots encountering severe space weather may request to descend lower.
They can also initiate emergency descent without a clearance.
46
What does BR stand for?
(Weather reports)
Mist.
47
What does GR stand for?
(Weather reports)
Hail.
48
What does GS stand for?
(Weather reports)
Small Hail.
49
What does SQ stand for?
(Weather reports)
Squalls.
50
What does DS stand for?
(Weather reports)
Dust storm.
51
What does DU stand for?
(Weather reports)
Dust.
52
What does FC stand for?
(Weather reports)
Funnel cloud.
53
What does FR stand for?
(Weather reports)
Freezing.
54
What does FU stand for?
(Weather reports)
Smoke.
55
What does IC stand for?
(Weather reports)
Ice crystals.
56
What does PL stand for?
(Weather reports)
Ice pellets.
57
What does PO stand for?
(Weather reports)
Dust devils.
58
What does SA stand for?
(Weather reports)
Sand.
59
What does SG stand for?
(Weather reports)
Snow grains.
60
What does SS stand for?
(Weather reports)
Sandstorm.
61
What does VA stand for?
(Weather reports)
Volcanic ash.
62
What does BC stand for?
(Weather reports)
Patches.
63
What does COR stand for?
(Weather reports)
Correction.
64
What does DR stand for?
(Weather reports)
Drifting.
65
What does MI stand for?
(Weather reports)
Shallow.
66
What does NCD stand for?
(Weather reports)
No cloud detected.
67
What does NSC stand for?
(Weather reports)
No significant cloud.
68
What does NSW stand for?
(Weather reports)
No significant weather.
69
What does PR stand for?
(Weather reports)
Partial.
70
What does RE stand for?
(Weather reports)
Recent.
71
What does SKC stand for?
(Weather reports)
Sky clear.
72
What does TL stand for?
(Weather reports)
Until.
73
What is a micro/macroburst and their dimensions?
Micro (less than 4km, less than 2.5m) & Macro (more than 4km, bigger than 2.5m).
Downward and outward burst of wind, usually under a thunderstorm.
74
What is a squall?
Strong wind of at least 1 minute, usually from storm, rain, heavy snow.
Danger mostly when operating near the surface.
75
What annex covers met?
3.
76
What does Annex 11 (ATS) state about the requirement for provision of meteorological information?
ATSUs shall be provided with up-to-date information on existing & forecast weather.
77
Who makes surface observations?
ATSUs, met bases, ships and automatic buoys.
78
How are upper air observations taken?
Radiosondes attached to balloons up to 30km on pressure, wind velocity, temperature and humidity.
79
What are the different type of observations?
Surface, Upper Air, Aircraft and Satellite.
80
Which ICAO doc details the coordination required between ATS and met services?
ICAO Doc 9377.
81
What are the layers of the atmosphere from highest to lowest?
Exosphere
Thermosphere
Mesosphere
Stratosphere
Troposphere
82
What are the dimensions and features of the Troposphere?
0km to 6-20km.
75% of the Earth's atmosphere in this level.
83
What are the dimensions and features of the Stratosphere?
6-20km to 50km.
Temp rises to -15oC at the top due to Ozone layer absorbing heat.
84
What are the dimensions and features of the Mesosphere?
50km to 80km.
Air pressure & density continue to decrease.
No weather.
Temp decreases with height.
85
What are the dimensions and features of the Thermosphere?
80km to 600km.
Temp increases with height but still cold to touch.
Where satellites are located.
86
What are the dimensions and features of the Exosphere?
500km-690km to 10000km.
Outer space above this level.
87
What are the components of the atmosphere?
0.3% Carbon Dioxide
1% Argon
1%-4% Water vapour
21% Oxygen
78% Nitrogen
88
What is the basic relationship between the atmosphere and altitude?
Fewer gas molecules higher up so density decreases with height.
89
What is the basic relationship between the atmosphere and temperature?
Cool air is denser and thus has a higher pressure.
90
What is the basic relationship between the atmosphere and humidity?
Humid air is less dense than dry air, therefore water molecules rise in the atmosphere leading to lower air pressure.
When air can't hold any more water, it's saturated.
High humidity means greater chance of rain, fog, dew.
91
How is wind created?
Differences in air pressure.
92
What is associated with lower pressure?
Warm air, high altitude and humid air.
93
What is associated with higher pressure?
Cold air, low altitude and dry air.
94
How is wind speed measured?
Anemometer.
95
How is wind direction measured?
Wind vane.
96
How is cloud base and coverage measured?
Ceilometer.
97
How is dew point and relative humidity measured?
Hygrometer.
98
How is RVR measured?
Transmissometer.
99
What is the ISA temperature?
15oC.
100
What is the ISA pressure?
1013.25hpa.
101
What is ISA density?
1.225kg/m3.
102
Does air temperature increase or decrease with height in the troposphere?
Air temperature is assumed to decrease with height at a constant rate throughout the troposphere.
103
What is the lapse rate up to 11km?
2oC per 1000ft.
104
What is the lapse rate above 11km?
0oC per 1000ft up to 20km.
105
What are the two reasons the ISA has been defined?
Used in calculations when designing aircraft, testing and standardisation in the development and calibration of instruments.
Aircraft flying in similar regions will operate as close as possible to the same levels.
106
What are the four ways that heat is transferred?
Radiation - Heat transfer through EM waves.
Conduction - Heat transfer through direct contact.
Convection - Heat transfer due to upward moving air currents.
Advection - Heat transfer due to horizontal moving air currents.
107
What is an adiabatic process?
It occurs when there is no heat transfer in a system?
108
What is the DALR? (Dry)
3oC per 1000ft.
109
What is the SALR? (Saturated)
1.5oC per 1000ft.
110
What is ELR?
Environmental lapse rate - decrease in temperature as altitude increases.
111
What is air cooled from below?
Stable.
112
What is air warmed from below?
Unstable.
113
How is surface temperature determined?
By incoming solar radiation and outgoing terrestrial radiation.
114
What is surface temperature influenced by?
Daily/seasonal variations and by location.
115
What is diurnal temperature variation?
During the day, incoming solar radiation is greater than outgoing terrestrial radiation, leading to heating.
During the night, no solar radiation and heat is continuously lost due to terrestrial radiation.
116
What is seasonal temperature variation?
Suring summer, days are longer, and sun rises higher leading to intense heating.
Shorter nights lead to less cooling, opposite effect in winter.
Seasonal changes less significant around the equator.
117
What is dew point?
Temperature to which air would have to be cooled for it to become saturated.
118
What is super cooling?
Water droplets below 0oC but do not freeze due to curvature of droplets.
119
How is saturation achieved?
Air is cooled where it can hold no more water vapour (fog or dew).
Water vapour is added to the air by evaporation until it is saturated.
120
What is relative humidity?
Degree of saturation.
Warmer air can hold more water so % of humidity will decrease.
121
What is latent heat?
Heat released or absorbed when water changes state.
122
What is the relationship between pressure, temperature, density and height?
Temp decreases with height (2oC per 1000ft), 1kg3 of air is approximately 1kg at sea level (pressure) and density decreases with height.
123
What is elevation?
Vertical distance of a point on Earth's surface measured from mean sea level.
124
What is height?
Vertical distance of point measured from specified datum.
125
What is altitude?
Vertical distance of a point measured from mean sea level.
126
What is a Flight Level (FL)?
Surface of constant air pressure which is related to a specific pressure datum (1013.25hpa) and is separated from such other surfaces by specific pressure intervals i.e. the vertical distance of an aircraft above a standard air pressure.
127
How is atmospheric pressure measured?
Mercury barometer, Aneroid barometer and Digital barometer.
128
How does a mercury barometer work?
Vacuum-filled tube.
As pressure increases in reservoir, it pushes mercury up the tube.
129
How does an aneroid barometer work?
Airtight capsule expands when pressure is low, or contracts when pressure is high, turning dial.
130
How does a digital barometer work?
Microchip sensitive to change.
131
What are the three types of cells relating to atmospheric circulation?
Hadley, Ferrel and Polar.
132
What is a Hadley cell?
Intense heating at the equator.
Air rises, creating a low pressure zone.
Warm air rises at the equator, moves poleward at high altitudes, sinks around 30° latitude, and returns equatorward near the surface.
133
What is a Ferrel cell?
Mid-latitude atmospheric circulation pattern that moves air poleward at the surface and equatorward aloft, driving the westerly winds between 30° and 60° latitude.
134
What is a Polar cell?
A polar cell is a large-scale atmospheric circulation pattern that occurs in the polar regions, characterized by cold air descending and spreading outward towards lower latitudes.
It operates roughly between 60° latitude and the poles.
135
What is a jetstream?
Fast moving westerly currents of air that occur at altitudes 9-16km between each of the cells.
136
What cells do the strongest winds occur between?
Polar and Hadley cells.
137
What are the different typical air masses?
Polar maritime/returning polar maritime, Artic maritime, Polar continental air mass, Tropical maritime air mass and Tropical continental air mass.
138
Where does the Artic maritime air mass originate from and what weather is associated?
Artic.
Wet, cold air brings snow in winter.
139
Where does the Polar continental air mass originate from and what weather is associated?
Central Europe.
Hot air brings dry summers.
Cold air brings snow in winter.
140
Where does the Tropical continental air mass originate from and what weather is associated?
North Africa.
Hot, dry air brings hot weather in summer.
141
Where does the Tropical maritime air mass originate from and what weather is associated?
Atlantic.
Warm, moist air brings cloud, rain and mild weather.
142
Where does the Returning/Polar maritime air mass originate from and what weather is associated?
Greenland.
Wet, cold air brings cold, showery weather.
143
How would you describe a tropical air mass?
Unstable as heated from below.
As it moves to cooler environments, it becomes cooled form below and becomes more stable.
144
What weather conditions arise from stable air?
Leads to calmer weather conditions.
145
What weather conditions arise from stable air?
Produces volatile or rapidly changing weather conditions.
146
What is an isobar?
Line on a map which joins places of equal atmospheric pressure at sea level.
147
What is an anticyclone?
High pressure area, 'H'.
Winds tend to be light and blow clockwise.
Air is descending, inhibits cloud formation.
148
What is a depression?
Low pressure area, 'L'.
Rising air which cools- water vapour condenses to form clouds/precipitation.
Cloudy, wet and windy (anticlockwise direction).
149
What is a ridge?
Elongated area of high pressure extending from the centre of the high pressure region bringing fine and stable weather conditions.
150
What is a trough?
Elongated area of low pressure extending from the centre of the low pressure region resulting in low cloud, rain and windy conditions.
151
What is Buys Ballot's Law?
In the northern hemisphere, if someone stands with their back to the wind, pressure is lower on the left hand side of that person.
152
What are squall lines?
Storms ahead of a cold front.
153
What si the space between a warm and cold front called?
The warm sector.
154
How is a cold front formed?
When a steep leading edge of a cold air mass undercuts a warm air mass, forcing the warm air to rise rapidly.
155
How is a warm front formed?
When a warm air mass slides up over a retreating cold air mass.
156
How is an occluded front formed?
When a faster cold front overtakes a warm front, lifting the warm air completely off the ground.
157
What is a mountain wave?
Gradient of mountain forces air upwards, cools and sucks on the other side.
If air's stable, it tries to return to original level and oscillation is stablished.
158
What is a fohn wind?
Winds flowing over a mountain lead to cold, wet weather on one side of the mountain and warmer, drier conditions on the other.
159
What causes a fohn wind?
It's a consequence of humid/unstable air hitting the side of the mountain.
160
What are the two types of slope winds?
Anabatic and katabatic.
161
What is a katabatic wind?
Slopes cool more quickly than the valley floor, dense air descends into valley. (Mountain).
162
What is an anabatic wind?
Sun warms mountains, air rises, cool air of valley drawn to replace lost rising air. (Valley).
163
What is a sea breeze?
Land warmed by afternoon, warm air rises (convection), cooler air over sea blows in to replace lost air.
164
What is land breeze?
At night, land cools quicker meaning the air becomes more dense meaning it naturally moves from high pressure to low pressure of the warmer sea.
165
What is a squall line?
Elongated line of severe thunderstorms, wind and rain.
166
What weather conditions are associated with thunderstorms?
Heavy rain.
Heavy hail.
Strong, gusting winds.
Lightning.
Turbulence.
167
What dimensions can a single-cell thunderstorm extend to?
10-20 miles and as high as 70000ft.
168
What three components are required for thunderstorms to form?
Unstable air, lift and moisture.
169
How does unstable air exist?
Warm air sits beneath cold air, cold air sinks and warm air rises.
170
What causes an air mass to rise?
Warm air naturally rises.
Two fronts meet and force the air up.
Air forced up by terrain.
171
What mesoscale systems are commonly related to aviation?
CB clouds, turbulence, icing, heavy precipitation and winds.
172
What impacts on ATC do mesoscale systems cause?
Irregular flow of traffic.
Reduced airspace capacity.
Increased coordination.
Other traffic in sector.
Increased use of frequency.
173
What impacts on pilots and airlines do mesoscale systems cause?
Weather avoidance.
Communication.
Delays.
Aerodrome closure/diversion.
Fatigue.
Commercial.
174
What is a gust?
Short burst of high speed wind.
175
What is a squall?
Winds that last approximately 1 minute.
176
What direction is veering?
Clockwise movement.
177
What direction is backing?
Anticlockwise movement.
178
What is a thermal wind?
Caused by two air masses meeting that have different temperatures.
179
What's the result of the Coriolis effect in the northern hemisphere?
Wind deflects to the right.
180
Where are jet streams located?
Just below the tropopause (upper troposphere).
181
What speeds can jet streams reach up to?
200mph.
182
What is turbulence?
Disrupted airflow.
183
What can cause turbulence?
Convective clouds (cumulus, cumulonimbus).
Geographical features (mountains).
Temperature inversions.
184
What is the result of turbulence?
Causes random and often rapid fluctuations in speed and direction over a short distance.
185
What is surface wind?
The wind velocity (speed and direction) indicated by instruments situated close to the runway in use.
186
What is an upper wind?
Predicted wind velocity at various altitudes.
Used to identify headwinds and tailwinds.
187
What unit of measurement is wind speed presented in?
Nautical miles per hour (knots).
188
What unit of measurement is wind direction presented in?
Degrees.
189
What is solar heating?
Ground is heated by the sun, leading to low pressure air which rises creating pressure gradients.
190
What is PGF?
Pressure Gradient Force.
Strength determined by pressure difference and distance.
Greater PGF = stronger winds (closer area and larger pressure difference).
191
What are geostrophic winds?
Winds travelling from high-pressure to low-pressure are turned 90°, flowing parallel to isobars. Close isobars indicate strong wind.
192
What is orographic lift?
Cooling when already fairly saturated.
193
What speed do cold fronts travel?
40-50mph.
194
What speed do warm fronts travel?
20-30mph.
195
What clouds are associated with cold fronts?
Cumulonimbus.
196
What clouds are associated with warm fronts?
Nimbo/stratus clouds.
197
What weather is associated with a cold front before and after it passes?
Short, intense rainfall or thunderstorms.
Followed by drop in temp/humidity and clearer, cooler weather follows.
198
What weather is associated with a warm front before and after it passes?
Steady, prolonged rain or drizzle.
Followed by a gradual increase in temp/humidity and clearer, warmer weather when its passed.
199
What is turbulent mixing?
Chaotic movement of air that redistributes heat, moisture and momentum through the atmosphere.
200
What is an eddy and how does that apply to turbulent mixing?
Eddies are how turbulent mixing happens.
When air becomes turbulent, it doesn't flow smoothly.
This forms eddies - small swirling circulations of air.
Eddies move parcels up, down and sideways.
That movement causes turbulent mixing.
201
Describe stratus/strato clouds.
Flat or layered and smooth in appearance.
202
Describe cumulus/cumulo clouds.
Heaped and puffy in appearance.
203
Describe Nimbus/nimbo clouds.
Indicates that the cloud is rain bearing.
204
Describe alto clouds.
Found in a middle level band (6500ft-20000ft).
205
Describe cirrus/cirro clouds.
Found in the high level band (above 20000ft).
Wispy in appearance.
206
What is virga?
Precipitation that falls from clouds but evaporates or sublimates before reaching the ground (visible streaks in the sky).
207
What tech does ceilometers use to give the cloud base?
Light detection and ranging technology.
208
What are the OKTA bands?
0 - Sky Clear (SKC)
1-2 Few (FEW)
3-4 Scattered (SCT)
5-7 Broken (BKN)
8 Overcast (OVC)
209
What is cloud base?
Height of the base of the lowest cloud visible of any amount.
210
What is cloud ceiling?
Height of the base of cloud (below 20000ft) that covers more than half the sky.
211
When are clouds reported in TAFs/METARs?
Only reported when cloud is below 5000ft.
212
What is CAVOK and the conditions?
Cloud and visibility OK.
- Prevailing visibility is 10km or more.
- No min visibility reported.
- No cloud below 5000ft or below MSA (whichever is greater).
- No towering cumulus (TCU) or cumulonimbus clouds (CB).
- No significant weather phenomena at or in the vicinity of the aerodrome.
213
How does rain affect aviation?
Reduced visibility and additional braking distance.
214
How does snow affect aviation?
Reduced visibility, reduced braking performance, icing, clearing a/c before departure.
215
How does hail affect aviation?
Vigorous up and down drafts in sub-zero temperatures.
Can damage windscreens/airframe.
216
What is freezing rain?
Rain that falls and freezes on impact or becomes super-cooled while falling but doesn't solidify.
217
What is the diameter of drizzle?
Light precipitation < 0.5mm.
218
What is the diameter of rain?
Droplets over 0.5mm.
219
How does snow occur?
When ice crystals stick together in cloud and when heavy enough will fall.
220
How is hail formed?
Strong updraft with high moisture content being pushed into freezing cold conditions.
221
What is the diameter of small hail?
Less than 5mm in diameter.
222
When and how does radiation fog form?
Usually form at night or early morning.
Clear skies, moist air, light winds, long nights.
223
When and how does shallow fog form?
low lying form of radiation fog that doesn't obstruct horizontal visibility but only between the surface and a height of not more than 2m above the ground.
224
When and how does advection fog form?
Warm moist air flows over a colder surface (relative humidity increases).
Reaches dew point and saturates.
225
How is radiation fog cleared?
Wind, sun, cloud and drier air.
226
How is advection fog cleared?
Wind - push to drier air mass, or increase in temp.
227
What is mist?
Suspended water droplets when visibility is greater than 1000m.
228
How does mist compare to fog?
Mist is less dense than fog but created in a similar way.
Lasts less than fog.
229
What is haze?
When sunlight hits pollutants or contaminants.
Mostly hot and dry conditions.
230
What is precipitation?
Rain, hail or snow.
231
What is volcanic ash and its effect?
Rock, mineral and volcanic glass particles.
Chokes engines, damage to wind screens and surfaces.
Visibility impaired, thunderstorms likely.
232
What is a sandstrom?
Loose particles blown by wind.
233
What is horizontal visibility?
Max distance of visibility along the ground.
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How is horizontal visibility measured?
Visibility of a black object against a bright background during the day,
or by 1000 candela light against a black background at night.
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What is slant visibility?
Max distance of visibility on the ground as seen from aircraft in flight.
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What is prevailing visibility?
Max distance across at least half the horizon.
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How is prevailing visibility reported?
50m increments up to 800m.
100m increments up to 5000m.
1000m increments up to 9000m.
When vis is 10km or more - 9999.
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What is RVR?
Runway Visual Range.
Distance pilot can expect to see along runway.
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When is RVR reported?
Reported when less than 1500m.
Increments of 25 (400m), 50 (400-800m) and 100 (800m+).
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How is RVR measured?
RVR = human observer.
IRVR = taken by instruments, transmissometers.
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Where are the transmissometers located for RVR?
Touchdown, midpoint and stop end.
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How does visibility affect aerodromes?
During departure and arrival (less).
May have LVPs (Low visibility procedures).
Workload higher.
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How does visibility affect approach?
More holding, more RT, more go-arounds/diversions and increased spacing.
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How does visibility affect area?
Reduced landing rate = higher workload.
Effect of diversions.
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How does visibility affect pilots?
Can't fly VFR.
Increased workload, potential diversions, disorientation.
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What are the different types of turbulence?
Thermal, shear, mechanical and aerodynamic.
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What is thermal turbulence?
Vertical current of air rising.
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What is shear turbulence?
Significant change in direction.
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What is mechanical turbulence?
Objects on the ground interrupt air flow.
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What is aerodynamic turbulence?
Flying in wake of another aircraft.
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How does icing occur?
Moisture hitting very cold aircraft (can affect aerodynamics of aerofoil).
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What are the different types of ice?
Clear, rime, frost and super cooled droplets.
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What is windshear and effect?
Sudden direction change.
Can vertically impact lift of aircraft, especially at landing.
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What are the turbulence categories?
Light, moderate, severe and extreme.
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What is the effect of icing on aircraft?
Changes aerodynamic of wing and accumulates in carburettor (piston a/c) or on propeller blades.
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How do thunderstorms affect aircraft?
Aircraft damage, can impact RT, poor visibility and less control of aircraft.
