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MET Flashcards

(63 cards)

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1
Q

What are the main meteorological parameters used in aviation?

A

(1) wind speed
(2) temperature and humidity (dew point)
(3) air pressure
(4) visibility
(5) cloud height and amount

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2
Q

What is influencing every single meteorological parameter?

A

Solar radiation

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3
Q

Name some meteorological hazards for aviation:

A

(1) poor visibility
(2) low cloud height
(3) precipitation & hail
(4) weather fronts
(5) turbulence, CAT, microbursts
(6) wind shear
(7) thunderstorms, lightening
(8) icing

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4
Q

How is the temperature officially measured?

A

In the shade at a height of 2 meters above ground. It’s the so-called “surface temperature”.

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5
Q

How is the precipitation distribution and intensity measured over a WIDE area?

A

By weather radar

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6
Q

Describe in short words the functionality of a weather radar!

A

(1) technical principle is very similar to a PSR Primary Surveillance Radar
(2) it receives an echo signal
(3) depending on this signal, the intensity and the consistency of the reflective object (water) is being calculated
(4) commercial aircraft do have their own weather radar aboard located in the nose

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7
Q

Unit and instrument used to measure: Temperature

A

°C / Thermometer

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8
Q

Unit and used instrument for: Pressure

A

hPa / Barometer

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9
Q

Unit and instrument used for: Visibility

A

m or km / Transmissiometer

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10
Q

Unit and instrument used for: Cloud height

A

ft / Ceilometer

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11
Q

Unit and instrument used for: Cloud amount

A

Oktas (z.B. 5/8) / Visual or Ceilometer
—> detects the amount and ceiling of clouds. (Laser measure)

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12
Q

Unit and used instrument for: wind speed

A

kt / rotation anemometer

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13
Q

Unit and used instrument for: wind direction

A

° (true north) / wind vane (wind sock)

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14
Q

Unit and used instrument for: relative humidity

A

% / Hygrometer

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15
Q

What’s the relation between inch and hPa in a Barometer?

A

In early times: temperature measurement with mercury fluid. Measured in inches.

“standard pressure” is defined as: 1013,25 hPa or 29,92 inch Hg

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16
Q

Altitude error due to air temperature: What’s the cause?

A

WHEN:
(1) flying with a constant altimeter indication
(2) flying with a constant subscale setting
(3) flying from a warmer to a colder air mass
RESULT:
constantly losing height
REMEMBER:
“during the winter the mountains are higher”

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17
Q

Name the different altimeter settings (“Q-groups”)

A

QFE (field elevation), QNH (nautical hight), QFF (field foot)

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18
Q

Define: QFE

A

Air pressure at field elevation

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19
Q

Define: QNH

A

Theoretical air pressure at MSL by using actual QFE and reducing it to MSL via ISA conditions

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20
Q

Define: QFF

A

Theoretical air pressure at MSL by using actual QFE and reducing it to MSL considering the actual current atmospheric situation

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21
Q

When and how is the QNH used in aviation?

A

QNH is used below 5000ft, usually for Take Off and Approach. The altimeter will be set to QNH on its subscale. Then the altimeter will show the ALTITUDE in flight. After landing it shows the FIELD ELEVATION of the aerodrome,

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22
Q

When calculating the QNH with the QFE, what standardised formula is being used?

A

ISA-conditions define: every 30ft the air pressure drops/rises exactly 1hPa.
example: QFE of 1007hPa at an airfield with elevation of 120ft.
120 / 30 = 4
QNH would be 1007 + 4 =1.011 hPa

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23
Q

What does the altimeter indicate on the runway and what is the name of the indicated value? Altimeter setting = QFE

A

Indication on runway = 0 ft
value = “height” (HGT)

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24
Q

What does the altimeter indicate on the runway and what is the name of the indicated value? Altimeter setting = QNH

A

Indication on runway = the elevation of the aerodrome
value = “altitude” (ALT)

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25
What does the altimeter indicate on the runway and what is the name of the indicated value? Altimeter setting = 1013 (standard atmosphere)
Indication on runway = QNE value = "FL" (flight level) or "PL" (pressure level) or "Pressure Altitude"
26
What is a cup anemometer?
Wind is measured by the cup system and wind direction by the wind vane in 10m AGL
27
What is the more modern version of measuring the wind?
Using sound waves to measure wind speed and direction. Advantages: no moving parts, better self-diagnostic capabilities, reduced maintenance How it works: three or more heads measure the time of ultrasonic pulses travelling between the heads
28
What is the classical way of measuring wind at an aerodrome?
Wind sock —> quick and good visual reference for the pilots —> it's more an estimation than a measurement
29
How is the wind direction measured?
Unit of measurement = wind direction as a degree of 360° In meteorology the wind direction referred to the direction the wind comes from.
30
Imagine: RWY in use = 24. You have direct crosswind from the right. What's the wind direction?
330°
31
Imagine: RWY in use = 17. Wind direction = 320°. Where does the wind hit your aircraft (left, right, head, tail)?
Right tail
32
What is the so called "gradient wind"?
The resulting assumption of the real wind direction and intensity after considering the coriolis and centrifugal forces between high and low pressure air masses. (Wind usually follows the line of an Isobar)
33
What is the "Jet Stream"?
A strong and narrow windward in the upper atmosphere along the frontline between a cold and a warm airmass. The windspeed is usually greater than 60kts.
34
Where do you have to expect "Clear Air Turbulence" (CAT)?
Especially at the outer part of the Jetstream (not in the inside at the axis —> there it's mostly constant wind speed) The area of the strongest CAT is usually found closer to the low pressure areas (over the Atlantic: the colder, North side)
35
What is the dewpoint?
Dewpoint describes the temperature to which air must be cooled to become fully saturated with water Vapor, assuming that air pressure remains constant. The temperature is always greater or equal the dewpoint.
36
What is "flight visibility"?
The visibility looking straight out of the cockpit during flight (horizontal)
37
What is "slant visibility"?
The visibility in flight looking towards the ground in 45°.
38
What is "ground sight"?
The visibility in flight looking straight down to the ground.
39
What is the "Runway visual range (RVR)"?
Distance at which a pilot on board of an aircraft located on the runway axis may see marks or lights bordering the runway or marking the axis. It's measured by Scatterometers or Transmissiometers. If there is a planned maintenance on this system, pilots should be made aware via NOTAM. It's available via ATIS or by Tower CWP (MET report)
40
What is the "vertical visibility"?
The visibility on the ground straight up (vertical).
41
What is the "ground visibility"?
The visibility 2m above the ground in horizontal direction.
42
What is Fog?
Fog is a cloud lying on the ground with: (1) visibility < 1km (2) humidity = 100% (3) temperature = dew point (—> spread = 0)
43
What kind of cloud do you find in a STABLE atmosphere?
Stratiform clouds (widespread) continuous rain
44
What kind of cloud do you find in an UNSTABLE atmosphere?
Cumuliform clouds with local showers
45
How is the cloud amount measured?
In octas. 1/8 - 2/8 —> "few" 3/8 - 4/8 —> "scattered" 5/8 - 7/8 —> "broken" 8/8 —> "overcast" if not detectable: "VV" —> sky obscured
46
What's an "Inversion"?
A layer in the atmosphere, where the temperature increases with height (stable atmosphere).
47
Why can an inversion be dangerous?
They are hazardous when they are situated near the surface. Especially during winter, when moist air is below the inversion layer there is a high risk of ICING!
48
What's characteristical for the lift and drag formulas?
The Formulas to calculate the lift and the drag of an aircraft are PRODUCTS (only multiplication!). So whenever one of the multipliers gets a smaller value, the resulting value shrinks! If one of the multipliers is ZERO, the resulting value is also ZERO!
49
What are the best meteorological conditions for an aircraft during takeoff?
(1) Low temperature (2) Low humidity (3) High air density
50
Name some meteorological phenomena that can be hazardous and are considered as "significant weather"!
(1) thunderstorm (2) Icing (3) turbulence (4) heavy precipitation (5) lightening
51
When do aircrafts have to expect turbulences most often?
During take off and landing
52
What's a "wind shear"?
It occurs within the first few thousand ft above the ground during take off or landing as a sudden loss of airspeed and altitude can occur. Wind shears often cause severe damages or accidents.
53
What different kinds of ICING are there?
Light, moderate and Severe
54
When and how do Thunderstorms appear?
The appear in an unstable atmosphere. They are formed by cumulonimbus (cb) clouds
55
Why are thunderstorms so dangerous for aviation?
In their mature stage, thunderstorms are flight hazards. In the clouds appear up- and downdrafts of up to +/-8.000 ft/min. Hail, turbulences, lightning, heavy rain may occur.
56
What are microbursts?
Occurs under towered cumulus and cumulonimbus clouds; often together with rain. Downdrafts up to 8.000ft/min. Outburst up to 100kts. MAY CAUSE SEVERE DAMAGE OR ACCIDENTS
57
Why is volcanic ash dangerous for aviation?
Consists of sulphur / sulphuric acid (silicate). Has a melting point of 1.100°C. Inside turbine there is 1.400°C. —> silicates melts, then sticks to colder part in the engine and may end in thrust loss and / or engine flame out.
58
What are typical messages and broadcasts regarding the meteorological conditions?
METAR, TAF, ATIS, VOLMET, SIGMET, AIRMET, SNOWTAM
59
What is a METAR
METeorological Aerodrome Routine Report (valid for an aerodrome) — issued at hourly / half-hourly intervals — describes the present weather situation on an aerodrome
60
What is a SPECI
It's a SPECIal Weather Report (reported like a METAR) (valid for an aerodrome)
61
What is a TAF?
Terminal Aerodrome Forecast (valid for an aerodrome)
62
What is a SIGMET?
Significant Meteorological Information (valid for an area, FIR/UIR) — a SIGMET is a weather warning!! — it's usually valid for 4-6 hours
63
What does "CAVOK" mean?
Clouds and Visibility OK — visibility > 10km — no clouds below 5000ft or below the highest MSA (whichever is greater) — no CB, no TCU — no significant weather

ATSEP Basic (10 decks)

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