Flight Training - September 2011 - 40

WEATHER»

TODAY’S STUDENTS ARE WIRED DIFFERENTLY. TRAIN THEM ACCORDINGLY.
For more information or to purchase our training materials, please visit JeppDirect.com/store21 today.

AIRCRAFT ALTIMETERS SENSE THE AIR PRESSURE AROUND THE AIRPLANE AND CONVERT THESE PRESSURE READINGS INTO FEET ABOVE MEAN SEA LEVEL.
clear—or nearly clear—skies in areas of high pressure.
INTO THE AIR. On average, air pressure decreases as you go up, and by the time you reach 18,000 feet, the pressure is approximately seven pounds per square inch. At this altitude about half of the Earth’s air, by weight, is above you and half is below. Aircraft altimeters sense the air pressure around the airplane and convert these pressure readings into feet above mean sea level. This works because air pressure changes at a regular rate with height. However, weather-related air pressure changes affect the rate of change. This is why pilots need to adjust their altimeters regularly as they fly into changing weather. AIR PRESSURE MEASUREMENTS.

Meteorologists (and pilots) don’t use pounds per square inch to measure air pressure because this value isn’t measured directly. The surface weather data the National Weather Service issues for the public and for altimeter settings is in inches of mercury. However, the NWS uses millibars, a metric measurement, for all upper-air pressures. Inches of mercury refers to how far the air pressure will push mercury up into a tube with the top of the tube closed and the open bottom in a container of mercury exposed to the air pressure.
Jack Williams is a writer specializing in weather and

climate, and is an instrument-rated private pilot. The

800.621.5377 I JeppDirect.com/store21
© 2010 Jeppesen

latest of his six books is The AMS Weather Book: The Ultimate Guide to America’s Weather.

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Flight Training - September 2011

Table of Contents for the Digital Edition of Flight Training - September 2011

Flight Training - September 2011
Contents
President's Perspective
Right Seat
Letters
Getting There in Style
This Weekend
Success Stories
What It Looks Like
AOPA Action
Member Products News
ASI News
Since You Asked
News
Member Products Final Exam
Insights
Flying Carpet
Protective Layers
Wheels Down, Rods Ready
Technique
Weather
Checkride
Flight Lesson
You Heard It Here First
Career Advisor
Tech Talk
Gyroscopic Precession
Flight Instructor Code of Ethics
Your Controls!
Advertiser Index
Debrief
Flight Training - September 2011 - Flight Training - September 2011
Flight Training - September 2011 - Cover2
Flight Training - September 2011 - 1
Flight Training - September 2011 - Contents
Flight Training - September 2011 - 3
Flight Training - September 2011 - President's Perspective
Flight Training - September 2011 - 5
Flight Training - September 2011 - Right Seat
Flight Training - September 2011 - 7
Flight Training - September 2011 - Letters
Flight Training - September 2011 - 9
Flight Training - September 2011 - Getting There in Style
Flight Training - September 2011 - 11
Flight Training - September 2011 - This Weekend
Flight Training - September 2011 - Success Stories
Flight Training - September 2011 - What It Looks Like
Flight Training - September 2011 - AOPA Action
Flight Training - September 2011 - Member Products News
Flight Training - September 2011 - ASI News
Flight Training - September 2011 - Since You Asked
Flight Training - September 2011 - 19
Flight Training - September 2011 - News
Flight Training - September 2011 - Member Products Final Exam
Flight Training - September 2011 - Insights
Flight Training - September 2011 - 23
Flight Training - September 2011 - Flying Carpet
Flight Training - September 2011 - 25
Flight Training - September 2011 - Protective Layers
Flight Training - September 2011 - 27
Flight Training - September 2011 - 28
Flight Training - September 2011 - 29
Flight Training - September 2011 - 30
Flight Training - September 2011 - 31
Flight Training - September 2011 - Wheels Down, Rods Ready
Flight Training - September 2011 - 33
Flight Training - September 2011 - 34
Flight Training - September 2011 - 35
Flight Training - September 2011 - Technique
Flight Training - September 2011 - 37
Flight Training - September 2011 - Weather
Flight Training - September 2011 - 39
Flight Training - September 2011 - 40
Flight Training - September 2011 - Checkride
Flight Training - September 2011 - 42
Flight Training - September 2011 - 43
Flight Training - September 2011 - Flight Lesson
Flight Training - September 2011 - You Heard It Here First
Flight Training - September 2011 - Career Advisor
Flight Training - September 2011 - 47
Flight Training - September 2011 - Tech Talk
Flight Training - September 2011 - Gyroscopic Precession
Flight Training - September 2011 - Flight Instructor Code of Ethics
Flight Training - September 2011 - Your Controls!
Flight Training - September 2011 - Advertiser Index
Flight Training - September 2011 - 53
Flight Training - September 2011 - 54
Flight Training - September 2011 - 55
Flight Training - September 2011 - Debrief
Flight Training - September 2011 - Cover3
Flight Training - September 2011 - Cover4
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