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Aviation Weather > IFR Weather > Flashcards

IFR Weather Flashcards

1
Q

How much can frost, ice or snow similar to medium or coarse sandpaper reduce lift and increase drag?

A

It reduces lift by as much as 30% and increases drag as much as 40%

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2
Q

What type of wing is even more susceptible to frost, bugs and dirt?

A

A “supercritical” or “laminar flow” wing

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3
Q

Is the lower surface or upper surface of the horizontal tailplane more critical?

A

The lower surface is as critical as the upper surface of the wing

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4
Q

In what direction, on most airplanes, does the horizontal tailplane generate lift?

A

The horizontal tailplane usually generates lift in the downward direction to counteract the nose-down attitude created by the center of lift being behind the center of gravity

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5
Q

Can loose snow/ice be left on the wing in anticipation of it falling off upon takeoff?

A

No! Ice or snow may be loose due to localized heating (APU Exhaust) and can refreeze once in contact with a colder, unheating, area. The loose pieces may also lodge in the gaps of controls surfaces

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6
Q

When using an alternate static source, should you have vents open from outside?

A

No, all vents should be closed in order to give an accurate reading

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7
Q

What is the difference between hoar and active frost?

A

Hoar frost appears as a thin, uniform deposit of ice with a fine, white, crystalline texture, but will not reform. Active frost is similar, but will continuously reform and de/anti-icing fluids must be used. Both types of frost form in the same conditions.

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8
Q

When should you expect frost?

A

When the aircraft skin is below freezing (this may occur when ambient temp is above freezing due to radiation cooling or cold soak fuel), the air temperature is close to the dew point temperature (within 3 or 5C), and the dew point is below freezing. Most common in or after a cloudless sky with calm winds or a warm front bringing warm/moist air.

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9
Q

What is cold soak fuel frost?

A

It occurs when ambient temperature is above freezing, but due to the cold nature of the fuel which comes in contact with the wing, precipitation or a small temp-dew point spread can cause frost around the areas of the fuel is in contact with the wing.

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10
Q

What temperatures will snow adhere/not adhere to the airplane?

A

Snow fall will likely adhere to your airplane when OAT is from +2C to -2C. When OAT is below -10C, it will most likely not adhere to your airplane.

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11
Q

Freezing rain is most associated with what?

A

A temperature inversion which is most likely caused be a warm or stationary front. The layer of freezing rain is typically 3000 ft. deep.

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12
Q

Should you take off when freezing rain or drizzle is occurring?

A

NOOOOO

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13
Q

Define ice pellets and its hazard:

A

Ice pellets, also known as sleet, grains of ice, and small hail, is extremely hazardous due to its ability to penetrate anti-icing fluid. Do not attempt to depart in ice pellet conditions.

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14
Q

What three major icing conditions should absolutely not takeoff in?

A
  1. Moderate to heavy freezing rain
  2. Heavy snowfall
  3. Ice pellets
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15
Q

What are the most critical areas to check for ice?

A
  • Wing leading edge and upper surface
  • Horizontal tailplane
  • Propeller
  • Engine inlet and fan blades
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16
Q

What is Kilfrost?

A

Kilfrost is a rapid de-icing fluid widely available in the UK at smaller airfields. Don’t heat this product due to its extremely low flash point. It is only a de-icer, and doesn’t offer any anti-icing qualities.

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17
Q

Type I De-icing/anti-icing fluid

A 
Color: red-orange
HOT: 0:06 - 0:11
No minimum rotation speed
Applied: Heated and diluted
Anti-icing property is to the extent the surface remains heated
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18
Q

Type II De-icing/anti-icing fluid

A

Color: clear-straw
HOT: 0:20 - 0:45
Minimum Rotation Speed: 100 knots
Applied: Either heated or cold, diluted or full strength

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19
Q

Type III De-icing/anti-icing fluid

A

Color: yellow-green
HOT: 0:10 - 0:20
Minimum Rotation Speed: 60 knots
Applied: It can be applied in hand-held equipment

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20
Q

Type IV De-icing/anti-icing fluid

A

Color: emerald green
HOT: 0:35 - 1:15
Minimum Rotation Speed: 100 knots
Applied: Either heated or cold, diluted or full strength (In North America it is usually applied cold, and only for anti-icing)

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21
Q

What is the HOT

A

HOT is the holdover time, or the time expected for the anti-de-cining fluid to be effective. The colder it is, the more precipitation, and the less viscous the fluid is, the faster it will fail.

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22
Q

Icing risk can be identified by what three factors?

A
  1. Temperature
  2. Moisture
  3. Droplet Size
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23
Q

At what temperature is icing most common?

A

Icing is most common when the static air temperature is between +2C and -20C.

24
Q

At what temperature is clear ice most likely to form?

A

Clear ice occurs when SAT is closer to freezing. This supports the mechanism whereby the supercooled water droplets impact, then flow aft before freezing. This process usually forms “horns” and disrupts airflow over the wing.

25
Q

At what temperature is rime ice most likely to form?

A

At colder temperatures further from freezing. The supercooled water tends to freeze on impact, and forms wedge shape accretions.

26
Q

For ice to form, what needs to be in the air?

A

A sufficient amount of liquid water. Liquid in the form of vapor, snow, or ice will generally not stick to an airplane’s external surfaces. It will be visible in the form of a cloud or liquid precipitation.

27
Q

What unique concerns do large droplets have with regards to icing?

A

The larger the droplet is, the further aft it is able to strike. It is also more likely to form shapes that can interrupt the flow of air over the wing or tail.

28
Q

Should flight in SLD conditions be continued?

A

No, it is a very high risk operation.

29
Q

When could you expect SLD?

A

Usually at or below 12,000 ft. and less than 3,000 thick. Either a temperature inversion or a collision-coalescense process.

30
Q

Temperature inversions occur most often with which fronts?

A

Stationary and warm fronts

31
Q

Ice pellets are a sign of what?

A

A temperature inversion aloft. The snow melts in a layer that is above freezing then refreezes in a colder layer forming ice pellets.

32
Q

What is collision caolescence and what does it tend to cause?

A

It occurs when supercooled droplets collide and grow larger. It usually forms freezing drizzle. It is more likely to occur with relatively warm. low altitude clouds with cloud tops below 12,000 feet and top temperatures warmer than -12C. Doesn’t necessarily mean there is a warmer layer above.

33
Q

What are some cues of SLD?

A

Ice on cockpit side window panels, aft of ice protected regions, aft of normal on prop spinner, or any other unusual or more extensive ice formations.

34
Q

Is icing more intense in the cloud base or tops?

A

Icing is most intense near the cloud tops, where the amount of liquid water is often greatest. This is the part of the cloud that has achieved the greatest amount of lifting, cooling, and condensation.

35
Q

Where is icing found in stratiform clouds?

A

Usually stratiform clouds have less icing issues than cumiliform. Icing usually doesn’t exceed 3,000 feet and are found in higher temperature mid- to low-level clouds below 15,000 AGL.

36
Q

Where is icing found in cumulus clouds?

A

Icing in cumulus clouds is shorter-lived, and more severe usuaully. The horizontal extent of a single cell averages 2 to 6 miles. Is usually found below 27,000 feet at temperatures between +2C and -20C.

37
Q

Is icing more likely to occur near large bodies of water.

A

Yes

38
Q

How to avoid ice while flying in mountains.

A

Fly on the leeward side of the mountain, but watch out for mountain wave turbulence.

39
Q

How do warm fronts form, and what are there characteristics?

A

They form when warm air slides gradually over a cooler air mass. Stratus clouds hundreds of miles ahead of the front are apparent. During the winter warm fronts can indicate freezing drizzle or rain. If your route is along the warm front, traverse it and fly on the backside.

40
Q

How do cold fronts form, and what are there characteristics?

A

Form when colder air undercuts warmer air. There are two types: “classic” characterized by extensive cumulus cloud development straddling the front, and “Shallow” cold front characterized by widespread stratus clouds behind the front.

41
Q

When are classic cold fronts typical?

A

During the warm season. They can develop into full blow thunderstorms with heavy precipitation, turbulence, hail, and high levels of SLD. Fly on the backside of the front.

42
Q

When are shallow cold fronts most typical?

A

During the cold season. Fly ahead of a shallow cold front, and prepare to change altitude of 3,000 feet if you encounter ice.

43
Q

When do occluded fronts occur.

A

When a warm air mass is trapped between two colder air masses and is forced to higher altitudes. You will get characteristics of both a cold and warm front.

44
Q

What affects does ice have on an aircraft?

A
  • decrease climb rate
  • decrease cruise speeds
  • increase stall speed
  • decrease service ceilings
  • decrease missed approach performance
  • increase fuel consumption and decrease maximum range
45
Q

Which type of ice increase drag the most?

A

Clear

46
Q

How do you increase the angle of attack on the horizontal stabilizer?

A

Increase speed, extend flaps, increase speed (anything that increases downwash of wing)

47
Q

With regard to wing design, what causes more ice to form on the leading edge?

A

the thinner “sharper” the leading edge is, the more efficient it is at collecting ice. If the leading edge radius decreases from root to tip, ice will form closer to the tips.

48
Q

What is runback icing?

A

Occurs when the anti-icing (by heating) system doesn’t evaporate the moisture, and it runs back until it reaches an unheated portion and refreezes.

49
Q

What is ice bridging?

A

It occurs when ice forms around the inflated de-icing boot. It is not a factor with modern boots.

50
Q

What is the primary weather source for cloud type and height?

A

Area Forecasts

51
Q

For an airmet or sigmet on icing to occur, how much area must it encompass?

A

The condition must occur or be forcasted to occur over an area of at least 3,000 square miles.

52
Q

With regards to airmets and sigmets, what does occasional mean?

A

greater than 50%

53
Q

What weather will you find on an Zulu airmet?

A

Moderate icing, freezing levels, and occasionally freezing rain or drizzle aloft.

54
Q

What does ICGIP or icing in precipitation mean?

A

Freezing rain or drizzle

55
Q

How often are airmets issued?

A

They are issued 4 times a day, valid for 6 hours with an additional 6 hour outlook

56
Q

What do sigmets report?

A

tornados, hail greater than or equal to 3/4” in diameter, surface winds greater than or equal to 50 knots, severe thunderstorms, embedded thunderstorms, lines of thunderstorms (squall lines), level 4 thunderstorms affecting 40% of a 3,00 square mile area. They are issued for periods of up to 2 hours.

57
Q

What are Center Weather Advisories (CWA’s)?

A

They are unscheduled in-flight advisories intended to supplement previously issued airmets and sigmets. They may also be issued when the event is too localized to warrant a sigmet and airmet. They are issued by center.

Aviation Weather (1 decks)

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