Weather Flashcards
Approved wx briefing sources
- These are legal wx briefings because there is a record of a pilot getting these briefings and legally you have to get The wx before any IFR Flight.
- Flight service Station (FSS)
- 1800 wxbrief (phone)
- Wx brief (online)
- Foreflight (is legal but don’t say it for a stage check)
Standard wx briefing
A full briefing includes: adverse conditions, VFR not recommended, synopsis, current conditions, enroute forecast, destination forecast, winds aloft, NOTAMs, and ATC delays
Abbreviated wx briefing
Updates a previously received briefing or previously received Information from mass disseminated sources.
Outlook briefing
For departures 6 or more hours away. Includes forecasts for the time of the flight.
Inflight briefing
FSS also provides any of the above types in flight.
METARs
Routine aviation weather that shows surface weather observations. Scheduled METARs are published every hour. Non-scheduled METARs (SPECI) are issued when there is a significant change in one or more of the reported elements since the last scheduled METAR
Terminal aerodrome forecast (TAF)
- Weather forecast for 5 SM radius from the center of The runway complex.
- issued 4 times a day, every 6 hours and normally covers a 24 or 30 hour forecast period
- if an airport doesn’t have a TAF and you need to determine if you need an alternate use the GFA tool on aviationweather.gov
Airmets
- Valid for 6 hours, are the most generic, least severe, and are hazardous to all, but mostly smaller aircraft.
- three types of airmets: Sierra, tango, Zulu
Sierra airmet
For mountain obstructions (something that is obscuring the mountain so you cannot see them) or IFR conditions 1000 ft ceilings and 3SM visibility will trip off an IFR airmet).
Tango airmet
Turbulence; moderate turbulence and sustained surface winds o knots of or greater.
Zulu airmet
Moderate icing
Sigmets
Non-scheduled, as needed. Valid for 4 hours. And
- three types: sierra, tango, and Zulu
Sierra sigmet
Visibility is less than 3SM
- could be seen with sand dust Storms (in the desert)
Tango sigmet
Severe or extreme turbulence not associated with a thunderstorm. Clear Air turbulence (cat)
Zulu sigmet
Severe icing NOT associated with thunderstorms.
Convective sigmets
- issued hourly (55 minutes past the hour) valid for 2 hours. All imply severe turbulence, wind shear, icing, etc.
- used for: severe thunderstorms, tornadoes, and embedded thunderstorms.
Severe thunderstorm
Due to: surface winds greater than or equal to 50 knots and hail 3/4” inch or greater in diameter.
Embedded thunderstorms
- A line of thunderstorms at least 60 miles long affecting at least 40% of its length.
- thunderstorms producing heavy precipitation effecting 40% of at least 3,000 square miles.
Pirep
A pilot report on conditions
What 2 things are required for icing to form?
- Visible moisture
- Aircraft surface temperature below freezing
3 types of icing
Structural icing, induction icing, and instrument icing
Structural icing
Accumulation of ice on the exterior of The aircraft. Small/narrow objects are The best collectors of droplets and ice. Ice on the temperature probe or pitot tube are the first places a pilot will see indications of ice accumulations.
Induction icing
Reduces the amount of air available for combustion within the cylinders. Most Common type is carburetor ice, but we don’t have a carburetor. Fuel injected systems can still be effected if the engines air source becomes blocked.
Instrument icing
Pitot-static system becomes blocked affecting the Flight instruments.
3 types of structural icing
Clear ice, rime ice, and mixed ice
Clear ice
Formed by The slow freezing of supercooled water. Dan The most serious form because it leaks back and changes the camber for the wing, can freeze control surfaces, and it is very heavy. Happens between +2°C and -10°C. Occurs downflow of the point of initial contact. Clear ice freezes over the center of the airfoil and not just The leading edge because it freezes at higher temperatures, it has that time to move over the airfoil.
Rime Ice
A rough, milky, opaque ice that is formed by The instantaneous or rapid freezing of droplets as they strike the aircraft. Happens at -15°C and lower. Occurs upflow of the point of the initial contact. Rime ice freezes on impact.
Mixed Ice
A combination of clear and rime ice formed on the same surface. Occurs between -15°C and -10°C. Occurs both up flow and down flow of the airframe.
Can we fly into known icing conditions?
Flight into known icing conditions is PROHIBITED (POH 2-23)
Which part of the aircraft accumulates structural ICE first?
Small, narrow parts of the aircraft (I.e pitot-tube, oat probe, etc.)
What to do if you fly into inadvertent icing conditions?
- first go through the checklist, the alternate door is going to come undone, we have pitot heat, defrost, alternate intake door, and alternate static source as our helpful equipment. We can also put alcohol solution on wings and in fuel before flight.
- The alternate door being open will result in a 10% power loss at full throttle because it’s lower air pressure, because the air coming from under the cowling is warmer.
- retract flaps during icing, because if there’s icing on our wings we can expect there is king on the tail plane as it’s much more narrow and Ice accumulates much faster there. Tailplane usually keeps The nose up attitude because the tailplane creates the downward force, causing The aircraft to be balanced. When the tail plane stalls, we will have an uncommanded nose-down upset of the aircraft, less and controllability.
- we retract flaps when this happens, because…
1. Extended flaps move the center of lift aft, causing The angle of attack of the tailplane to become more negative, creating a stall.
2. Extended flaps take away from the necessary flow over the tailplane.
Do we have anti-icing/de-icing equipment?
No, but we have things that may be helpful.
At the first indication of ice accumulation, the pilot must act to circumvent icing conditions. Options for action include the following:
- Move to an altitude with temperature above freezing
- Fly to an area clear of visible moisture
- Change the heading, and fry to an area of known non-icing conditions
- if these options are not available, conside an immediate landing at the nearest suitable airport
Tailplane stall
- The most susceptible surface of the airframe to accumulate icing is the tailplane due to its thin, simple shape. Also, it of the is out visible range of the pilot so it is virtually impossible to detect visually.
- A tailplane stall as the result of ice accumulation is most likely to occur during the approach and landing phase of flight.
Symptoms that may be a warning of a tailplane stall
- sudden, uncommanded nose-down pitch
- elevator control pulsing, oscillations, or vibrations
- unusual or abnormal pitch anomalies
- reduction or loss of elevator effectiveness (mushy controls)
- sudden change in elevator force (control would move nose-down if unrestrained).
Recovery procedures from a tailplane stall.
- To recover from a tailplanestall, you should retract the flaps to the last safe position and increase power only to the extent that you compensate for the loss lift created from retracting the flaps.
- over-increasing the power setting can aggravate and deepen a tail plane stall in some aircraft.
- if coming in to land and there’s suspicion of tailplane icing, do NOT put in any flaps (with flaps there is a slower airspeed at the same airspeed so the wing will stall much quicker), use your checklist, and remember that without flaps you will have a much faster airspeed on final, so landing distance will increase.
Define fog
A cloud that begins within 50ft of the surface.
Fog occurs when:
The air temperature near the ground reaches its dew point OR when the New point is raised to the existing temperature by adding moisture to The air.
Types of fog
Radiation, advection, Ice, upslope, steam
Radiation fog
Occurs on calm, clear nights when The ground coals rapidly due to the release of ground radiation fog.
Advection fog
Warm, moist air moves over a cold surface. Winds are required for advection fog to form.
Ice fog
Forms when The temperature is much below freezing and water vapor turns directly into ICE crystals. Ice fog is common in the artic regions but also occurs at mid-latitudes.
Upslope fog
Moist, stable air is forced up a terrain Slope and cooled down to its dew point by adiabatic cooling.
Steam fog
Cold dry air moves over war water. Moisture is added to the air m ss and Steam fog forms.
Microbursts
- most significant type of low level wind shear
- characteristics:
1. 1-2 miles in diameter
2. Most last about 15 minutes
3. 6000 foot per minute downdrafts
Front
A boundary separating two air masses. When a front passes there will always be a wind shift and a temperature change. in general when a front passes you usually see better weather in its wake.
Cold front
- acts like a snow plow: heavy air shoves up the warm air mass
- fast moving
- moves close to the ground
- brings beautiful clear air behind it
- behind The front is cold dense air and ahead of it is warm air. If the warm air mass is most you’ll likely see: potential thunderstorms, big clouds (towering cumulonimbus), big winds, showery precipitation, and great visibility.
- The teeth point to the direction that the front is moving.
Warm front
- acts like a blanket to force the other front out
- low cloud coverage (not cumulonimbus)
- brings steadier precipitation, steadier winds, lower visibility, and mid-layer clouds (ex-nimbostratus)
- when a warm front passes it leaves: warmer weather, a temperature change, not really but not really any clouds.
Stationary front
- when a cold and warm front meet head on and the weather associated is a mix of the two
- they battle for a couple days and then just dissipate
Occluded front
- when a cold front catches up to a warm front because it moves faster
- two types of occluded fronts: cold front occlusion and warm front occlusion ( you can’t tell from the surface analysis chart if it is CFO or WFO)
Cold front occlusion
Air behind the cold front is colder than the air ahead of the warm front. There a is mix of weather in in both (not ideal)
Warm front occlusion
Air behind the warm front is cold but the air in front is the coldest. Typically is more dangerous because if it’s unstable you’ll have embedded thunderstorms, fog, etc.
Low pressure
- moves up and in, counterclockwise motion. Unstable, lifting air, type of pressure seen with tornadoes and hurricanes
- if it is dry an then it is unstable air
- if it is moist air it is really bad weather and unstable conditions.
High pressure
- descending, clockwise motion, good weather conditions
Trough
A yellow dashed line that represents an elongated area of low pressure
Ridge
A brown zig-zag line that represents an elongated area of high pressure.
Isobars
- Lines of equal pressure
- measured in millibars: standard is 1013 millibars
- when isobars are really close together, you’ll see a steep pressure gradient
- pressure naturally wants to mingle in order to equalize. Because of this Your see really high winds.
- weather shifts east because of the cornolis effect
- from the isobars you can tell the wind direction: at the surface wind flows perpendicular To isobars and at altitude winds flow parallel to the isobars.
Thunderstorms
- 3 things needed: lifting action, moisture, and an unstable lapse rate.
- AS you take the warm, moister and shore it up it cools and comes back down causing an unstable lapse rate. Friction causes lightning. A cold front brings 2 out of the 3 things needed for a thunderstorm to form.
- good visibility means that there is a lot of air movement, so high winds means good visibility and still air means bad visibility
- stay about 20-25 miles from a thunderstorm because it can throw hail.
- if you get caught in a thunderstorm keep going through it because the most dangerous part of a thunderstorm is the turbulence.
What is The warmest you can pick up icing?
+2°C
Temperature lapse rate
2°C per 1000 feet
How should you pick your altitude if freezing level is a concern?
If icing is at 6,000ft and you can pier it up a +2°C, considering the temperature lapse rate, you could pick up the icing at 5,000 feet and you wanna stay 1,000 feet away from that so you should pick 4,000 feet
Why should you stay a healthy amount away from the freezing level?
- It’s not a set level that is guaranteed
- You can pick up ice at 2°C
- Your plane could be cooler than the air
What does a blue Chevron on freezing level chart depict?
Freezing level at The surface
What does a blue line with barbs on a freezing level chart depict?
A regular freezing level somewhere
What does the purple dash dot dot line on a freezing level chart depict?
Blocking, freezing level and be anywhere
Wind shear
A change in the direction or velocity of the wind that can happen At any altitude
- most hazardous: low level wind shear because it can slam any size aircraft into the ground
IFR
Visibility of less than 1sm and a ceiling between 0-500 feet AGL
LIFR
Visibility between one and three Sm and a ceiling of 500 - 1000 feet AGL
MVFR
Visibility between 3 and 5 Sm and a ceiling of 1000 - 3000 feet AGL
VFR
Visibility greater than 5SM and a ceiling greater than 3,000 feet AGL
