Weather Basics

Question 1

What affects do surface winds have on an aircraft?

Answer 1

Affect aircraft when

• taxiing
• taking off
• on final approach
• and landing.

Question 2

What are the 2 kinds of winds?

Answer 2

“Surface winds” and “Winds Aloft”.

Question 3

What affects do “Winds Aloft” have on an aircraft?

Answer 3

Affect the aircraft while airborne. They can push the aircraft off-course, slow it down or speed it up. Typical take off and landing is into the wind.

Usually larger airports allow a tailwind to reach 10 knots before they change the active runway to the opposite (180 degrees) direction.

Question 4

Wind direction refers to…

Answer 4

The direction the wind is coming FROM.

A wind of 090 @ 12 knots means that the wind is coming FROM a heading of 090.

If you are flying a heading of 090, you would be flying into a headwind and if flying a heading of 270, the wind would be a direct tailwind.

Question 5

“Sky cover” is measured in what increments?

Answer 5

1/8th increments

Question 6

Clouds

SKC means?

Answer 6

Skies Clear.

0/8 - clear skies - no clouds

Question 7

Clouds

FEW means?

Answer 7

1/8 to 2/8 of the sky is covered with clouds

Question 8

Clouds

SCT means?

Answer 8

SCT= Scattered

3/8 to 4/8 of the sky is covered in clouds

Question 9

Clouds

BKN means?

Answer 9

BKN= Broken

5/8 to 7/8 of the sky is covered with clouds.

This comes with a ceiling.

Question 10

Clouds

OVC means?

Answer 10

OVC = Overcast

8/8 - the entire sky is covered with clouds- this comes with a ceiling.

Question 11

Clouds

Ceiling means?

Answer 11

Ceiling is the altitude at the bottom of the cloud layer. Just like the ceiling in your house.

When you hit this altitude, you are at the bottom of the cloud layer and going any higher will place you in the clouds.

Question 12

Barometric Pressure simply put…

Answer 12

Is how much the atmosphere weighs.

Question 13

What to do with Barometric pressure settings?

Answer 13

You will use this setting to properly adjust your aircraft altimeter to the correct altitude based upon the pressure.

In the United States, you will use a setting of
29.92” (inches) of Mercury for sea level. (Equivalent to 1013.2 millibars in Europe)

When you fly, you will need to know what the Barometric Pressure is to make the proper setting. If not, your aircraft altimeter will indicate the wrong altitude!

Question 14

AGL

Answer 14

Above ground level

Question 15

MSL

Answer 15

Mean Sea Level

Question 16

Detail the difference between and airport (or an object) at

5,000 ft AGL and 5,000 MSL if the airport (or object) is at an elevation of 1,500 feet?

Answer 16

In this case, the airport or object at 5,000 ft AGL
is actually also at 6,500 feet MSL.

Because at 1 ft AGL, we are actually at 1,501 ft MSL.

At 5,000 ft MSL, it would be at 3,500 ft AGL since we are subtracting the 1,500 ft of elevation we started with

Question 17

How does TEMPERATURE affect aircraft performance?

Answer 17

Air is
LESS DENSE when it is HOT.
= less lift.

MORE DENSE when it is COLD.
= increased lift

Question 18

Dew Point

Answer 18

The temperature that dew is formed.

When the temp approaches the dew point, the most likely result will be FOG, not dew or rain.

Question 19

Density altitude

Answer 19

The is the altitude ADJUSTED based upon the Barometric Pressure, Temperature and Humidity.

In higher elevations, DENSITY ALTITUDE has a serious impact on the performance of any aircraft.

*Air is less dense the higher the density altitude is, and as a result, there is less lift created, making your airplane a tremendous amount LESS EFFICIENTLY!

Question 20

The Three major factors to consider for AIR DENSITY…

Answer 20

PRESSURE

TEMPERATURE

HUMIDITY

Question 21

AIR DENSITY

How does BAROMETRIC PRESSURE play into it?

Answer 21

The air is LESS DENSE as you go higher into the sky due to the lower pressure of the air.

The current air pressure could be lower or higher than the standard 29.92 inches of Mercury as well…

Question 22

AIR DENSITY

How does TEMPERATURE play into it?

Answer 22

The temperature of the air can also affect density. Remember that air expands when heated.
Hot air is LESS DENSE than cold air.
Therefore, HOT air will produce LESS left than cold air.

Question 23

AIR DENSITY

How does HUMIDITY play into it?

Answer 23

HUMID AIR is LESS DENSE = LESS LIFT

ARID (dry) conditions = MORE LIFT

Question 24

How does LESS DENSE AIR affect aircraft engine performance?

Answer 24

Less dense = LESS POWER 😬

Engines need air to operate. The LESS dense the air, the LESS POWER the engine can produce.

Compare flying out of telluride to Florida

Question 25

Which is best flying conditions as it relates to Density Altitude?

Answer 25

Cold, dry air is far better

than

hot, humid air…

Question 26

Density altitude is the “Actual”?

Answer 26

It is soo important that you need to determine the DENSITY ALTITUDE, which is the ACTUAL altitude of the air you will be flying in, adjusted for…

PRESSURE
TEMPERATURE
HUMIDITY

Question 27

Convective activity

Answer 27

THUNDERSTORMS!!!

Avoid at all costs. Period

Fly WAY around it, land or delay your trip.

Question 28

Weather Information available to the pilot

Answer 28

METAR Reports

TAF Reports

Weather Charts
A) Winds Aloft
B) Surface Winds

Question 29

METAR REPORTS

Answer 29

METAR = Meteorological Reports

The official USA METAR website is run by NOAA

Http://weather.noaa.gov/weather/Metar.shtml

The website has instructions on how to read metar reports.

METAR reports in the USA are taken every hour within a 10 minute window and reflect current weather conditions.

Question 30

TAF Forecasts

Answer 30

TAF = Terminal Aerodrome Forecasts

In the USA, managed by NOAA along with METAR’s.

Http://weather.noaa.gov/weather/taf.shtml

Website has instructions on reading TAF’s.

These forecasts differ from a METAR in that a

*TAF is a FORECAST, whereas a METAR is actual weather conditions.

TAF’s are updated 4 times a day starting at
0000 GMT, then every 6 hours after that -
0600 GMT
1200 GMT
1800 GMT

Question 31

Jetstream

Answer 31

Really fast wind pattern which snakes its way around the USA.

It’s a great idea to get winds aloft forecasts before planning your flight route. Use the Jetstream to your advance if possible for speed and fuel burn considerations.