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PHYSICS OF THE ATMOSPHERE
TERMINAL LEARNING OBJECTIVE
At the completion of this lesson, the student will:
ACTION: Demonstrate an understanding of the
atmosphere’s physical properties and their impact
on the operation of the TH-67 pressure instruments.
CONDITION: In a classroom environment given
information on the pressure instruments and the atmosphere.
STANDARD: Answer questions pertaining to the
atmosphere’s physical properties and their impact on the
operation of the TH-67 pressure instruments. Receive a “GO”
by correctly answering the required number of questions on
criterion referenced examination 011-0050.
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A: Enabling Learning Objective
Action: Identify the characteristics of the standard
atmosphere
Condition: Given information about the standard
atmosphere
Standard: IAW FM 3-04.240 and FAA-H-8083-25A,
Pilot’s Handbook of Aeronautical Knowledge.
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The “Standard Atmosphere”
“A hypothetical vertical distribution of atmospheric
temperature, pressure, and density which by
international or national agreement is taken to be
representative of the atmosphere for the purpose
of altimeter calibrations, aircraft design,
performance calculations, etc.”
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53,000
90%
18,000
Sea
SeaLevel
Level
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50%
Standard Pressure Lapse Rate
7500’
22.42”Hg
5000’
24.92”Hg
4000’
25.92”Hg
3000’
26.92”Hg
2000’
27.92”Hg
1000’
28.92”Hg
MSL
29.92”Hg
1” Hg per 1000’
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Standard Temp Lapse Rate
7500’
0°C
5000’
5°C
4000’
7°C
3000’
9°C
2000’
11°C
1000’
13°C
MSL
15°C
2°C per 1000’
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AIR DENSITY
15°C
29.92”Hg 23°C
28.92”Hg 15°C
29.92”Hg
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AIR DENSITY
Good Bad
Press
H
L
Temp
L
H
Hum
L
H
MMMMMMMMOVING
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B: Enabling Learning Objective
Action: Identify the pressures used in the pitot
static system
Condition: Given information about the pitot static
system pressures
MMMMMMMMOVING
Standard: IAW FM 3-04.240
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Static Pressure -- Weight of a column of air
Dynamic Pressure – Additional pressure
caused by air in motion
Impact Pressure -- Static + Dynamic
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Stagnation point
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Static pressure only
Impact pressure = Static + Dynamic
Note: Impact = Ram = Total = Pitot Pressure
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Construction of the Pitot System
LEFT
RIGHT
HEATER
STATIC
VENTS
PITOT TUBE
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Construction of the Pitot System
Notice that the Pitot Tube goes
only to airspeed indicator!
The Static Pressure is vented
to all three instruments.
Construction of the Pitot System
The diaphragm in the Airspeed Indicator
is connected to the Pitot Tube. It
only senses Pitot Pressure. The case
is vented to Static Pressure.
Construction of the Pitot System
The diaphragm in the Vertical Speed Indicator
is vented to Static Pressure.
The case is vented to Static Pressure
through a calibrated leak.
Construction of the Pitot System
The aneroids in the Altimeter are sealed. The
case is vented to Static Pressure.
MMMMMMMMOVING
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C: Enabling Learning Objective
Action: Identify the operational characteristics of
the airspeed indicator
Condition: Given information about the airspeed
indicator
Standard: IAW FM 3-04.240
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AIRSPEED INDICATOR
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LEFT
RIGHT
STATIC
VENTS
PITOT TUBE
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STATIC VENT
PITOT TUBE
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Impact pressure = Static + Dynamic
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?
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D: Enabling Learning Objective
Action: Identify the uses of the airspeed indicator
Condition: Given information on the uses of the
airspeed indicator
Standard: IAW FM 3-04.240
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Uses for the airspeed indicator
1: Keep aircraft within “Never Exceed Speed"
2: Determine best operational speed for best
climb, best endurance, and best range
3: Determine rate of movement for navigation
4: Aircraft attitude
Airspeed fast-Pitch attitude low
Airspeed low-Pitch attitude high
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MMMMMMMMOVING
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E: Enabling Learning Objective
Action: Identify the errors associated with the
airspeed indicator
Condition: Given information about airspeed
indicator errors
Standard: IAW FM 3-04.240
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ERRORS
Instrument Error – Minor, caused by friction
Installation Error – Caused by misalignment of
the pitot tube and/or the static vents with the
relative wind
Density Error – Caused by changes in air
density
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TRUE AIRSPEED (TAS) IS THE SAME,
AIR IS LESS DENSE AT ALTITUDE,
THEREFORE, CALIBRATED
AIRSPEED (CAS) IS LESS THAN TAS.
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CAS IS THE SAME, AIR IS
LESS DENSE AT ALTITUDE, THEREFORE,
TAS IS MORE THAN CAS AT ANY
ALTITUDE ABOVE
ZERO FEET DENSITY ALTITUDE.
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MMMMMMMMOVING
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F: Enabling Learning Objective
Action: Identify the types of airspeed
Condition: Given information about types of
airspeed
Standard: IAW FM 3-04.240
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Types of Airspeed
IAS – Indicated Airspeed – read from the
airspeed indicator
CAS – Calibrated Airspeed – Indicated
Airspeed corrected for installation error
TAS – True Airspeed - Calibrated Airspeed
corrected for density error
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Airspeed Indicator in Review…
Can you identify the
pressures used, the errors
and the types of airspeed?
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MMMMMMMMOVING
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G: Enabling Learning Objective
Action: Identify the operational characteristics
of the vertical speed indicator
Condition: Given information about the operation
of the vertical speed indicator
Standard: IAW FM 3-04.240
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Vertical Speed Indicator
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LEFT
RIGHT
STATIC
VENTS
PITOT TUBE
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STATIC
VENTS
PITOT TUBE
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Calibrated
Leak
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Calibrated
Leak
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Calibrated
Leak
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Calibrated
Leak
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MMMMMMMMOVING
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H: Enabling Learning Objective
Action: Identify the uses of the vertical speed
indicator
Condition: Given information about the uses of
the vertical speed indicator
Standard: IAW FM 3-04.240
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Uses of the vertical speed indicator
1: Determine rate of climb or descent
2: Trend instrument-shows attitude changes
immediately when in level flight
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Vertical Speed Indicator
Preflight Check
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MMMMMMMMOVING
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I: Enabling Learning Objective
Action: Identify the errors associated with use of
the vertical speed indicator
Condition: Given information about vertical
speed indicator errors
Standard: IAW FM 3-04.240
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Errors of the vertical speed indicator
1: Six to nine second lag when leveling off
from a climb or descent caused by the
calibrated leak
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Calibrated
Leak
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Calibrated
Leak
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Errors of the vertical speed indicator
1: Six to nine second lag when leveling off
from a climb or descent caused by the
calibrated leak
2: Erratic in rough air
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Vertical Speed Indicator in Review…
Can you identify the
pressures used, the errors
and preflight procedures?
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MMMMMMMMOVING
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J: Enabling Learning Objective
Action: Identify the operational characteristics of
the altimeter
Condition: Given information about the
operational characteristics of the altimeter
Standard: IAW FM 3-04.240
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ALTIMETER
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LEFT
RIGHT
STATIC
VENTS
PITOT TUBE
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STATIC
VENTS
PITOT TUBE
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Aneroid wafers
sealed at
factory
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Dial – three pointers
10,000’ Indicator
Tick marks in increments of 2000’
1,000’ Indicator
Tick marks in increments of 200’
100’ Indicator
Tick marks in increments of 20’
1,040’
8,000’
18,980’
Kollsman window – corrects for atmospheric
pressure changes
28.10”Hg to 31.00”Hg
Set field elevation
ATIS – “Altimeter setting three zero two
four”
AIMS Counter
Drum Pointer
ATC Radar
Beacon System
Identification Friend
or Foe
MARK 12
SYSTEM
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MMMMMMMMOVING
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K: Enabling Learning Objective
Action: Identify the uses of the altimeter
Condition: Given information about the uses of
the altimeter
Standard: IAW FM 3-04.240
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Uses of the altimeter
Terrain clearance
Vertical separation
Attitude control
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MMMMMMMMOVING
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L: Enabling Learning Objective
Action: Identify the types of altitude
Condition: Given information about the types of
altitude
Standard: IAW FM 3-04.240
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Identify the types of altitude
a. Indicated
b. True
c. Absolute
d. Pressure (PA)
e. Density (DA)
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Indicated Altitude
Read from instrument with correctly set
Kollsman window (sea level pressure).
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True Altitude – Altitude above Mean Sea level
1000’
MSL
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Absolute Altitude– Altitude above the surface
(AGL)
MSL
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Pressure Altitude (PA) – Altitude above the
standard datum plane
1000’
MSL
29.92
Standard datum plane
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Standard Day
Pressure Altitude
True
Altitude
=
1000’
1000’
MSL
Pressure
Altitude
29.92
Standard datum plane
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Density Altitude (DA) : Is the density
corresponding to a given altitude
in a standard atmosphere.
Max torque available, max gross
weight,and performance are all
affected by Density Altitude
MMMMMMMMOVING
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Density Altitude (DA) : Pressure Altitude
corrected for non standard temperature
DA = PA + (120 Tv )
PA = Pressure Altitude
Tv = Temperature Variation
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Mean Sea Level (MSL)
7500’
22.42”Hg
0°C
5000’
24.92”Hg
5°C
4000’
25.92”Hg
7°C
3000’
26.92”Hg
9°C
2000’
27.92”Hg 11°C
1000’
28.92”Hg 13°C
MSL
29.92”Hg 15°C
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2040’
PA
29.92”Hg 15°C
MSL
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29.92”Hg 32°C
2040’
29.92”Hg 15°C
MSL
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29.92”Hg 32°C
PA = 0’
OAT = 36°
DA = 2500’
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OAT = 5°C
PA = 6000’
6000’ 3°C
5000’ 5°C
4000’
7°C
3000’ 9°C
2000’ 11°C
1000’ 13°C
MSL
15°C
OAT is Higher than standard
DA is Higher than PA
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6000’ 3°C
5000’ 5°C
4000’
7°C
PA = 4000’
OAT = 5°C
3000’ 9°C
2000’ 11°C
1000’ 13°C
MSL
15°C
OAT is Lower than standard
DA is Lower than PA
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6000’ 3°C
DA = PA +120’
5000’ 5°C
4000’
PA = 5000’
7°C
OAT
5°C
OAT
==
6°C
3000’ 9°C
One hour later
2000’ 11°C
1000’ 13°C
MSL
15°C
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MMMMMMMMOVING
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M: Enabling Learning Objective
Action: Identify the errors associated with the
use of the altimeter
Condition: Given information about altimeter
errors
Standard: IAW FM 3-04.240
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Altimeter errors
a. Instrument Error
b. Pressure Error
c. Temperature Error
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Instrument Error
Caused by friction
inside instrument
True
Altitude
1000’
1000’
MSL
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Field
Elevation
Instrument Error
30.26
Maximum
Error + / - 70 ft
-30.24
= .02
= 20 foot error
True
Altitude
“Altimeter three zero two four”
1000’
1000’
MSL
30.24 hg”
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Field
Elevation
Pressure Error – caused when flying into
areas that have different altimeter settings
than those set in the Kollsman window.
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Pressure Error
IND ALT
IND ALT
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Temperature Error
28.92
28.92
28.92
Warmer
Colder
MSL
MSL
29.92
1000’
Standard temp
1000’
29.92
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29.92
Pressure Error
28.92
IND ALT
IND ALT
29.92
29.92
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28.92
Colder
Standard temp
Warmer
28.92
29.92
OAT = 20°C
6000’ 3°C
5000’ 5°C
4000’
Indicated Altitude = 6000’
True Alt. is Higher than Indicated
7°C
3000’ 9°C
2000’ 11°C
1000’ 13°C
MSL
15°C
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6000’ 3°C
5000’ 5°C
4000’
7°C
3000’ 9°C
2000’ 11°C
Indicated Altitude = 4000’
OAT = 5°C
True Altitude is lower than Indicated
1000’ 13°C
MSL
15°C
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6000’ 3°C
Indicated Altitude = True altitude
5000’ 5°C
4000’
7°C
Indicated Altitude = 5000’
OAT = 5°C
3000’ 9°C
2000’ 11°C
1000’ 13°C
MSL
15°C
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MMMMMMMMOVING
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N: Enabling Learning Objective
Action: Identify pitot static system malfunctions
Condition: Given information about pitot static
system malfunctions
Standard: IAW FM 3-04.240
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Pitot Static System Malfunctions
STATIC VENT
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PITOT TUBE
Pitot Static System Malfunctions
STATIC VENT Property of Lear Siegler PITOT TUBE
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Pitot Static System Malfunctions
STATIC VENT
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PITOT TUBE
Pitot Static System Malfunctions
STATIC VENT
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PITOT TUBE
Altimeter – No change in indication
VSI – Level off at zero
Airspeed Indicator – opposite of clogged
pitot tube
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MMMMMMMMOVING
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The end
STOP
Abandon hope all ye who enter here
You are entering the hidden slide Zone
CH02
2 48.20
TX
MN
GD
LEFT
RIGHT
HEATER
STATIC
VENTS
PITOT TUBE
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Standard temperatures
OAT = 5°C
PA = 6000’
6000’ 3°C
5000’ 5°C
4000’
7°C
3000’ 9°C
2000’ 11°C
Is the DA higher or lower than PA
1000’ 13°C
MSL
15°C
DA is Higher than PA
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Standard temperatures
6000’ 3°C
5000’ 5°C
4000’
7°C
PA = 4000’
OAT = 5°C
3000’ 9°C
2000’ 11°C
Is the DA higher or lower than PA
1000’ 13°C
MSL
15°C
DA is lower than PA
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Property of Lear Siegler
Temperature Error
28.92
28.92
Warmer
Colder
28.92
MSL
MSL
29.92
1000’
Standard temp
1000’
29.92
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29.92
Standard temperatures
OAT = 20°C
6000’ 3°C
5000’ 5°C
4000’
Indicated Altitude = 6000’
True Alt. is Higher than Indicated
7°C
3000’ 9°C
2000’ 11°C
1000’ 13°C
MSL
15°C
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Standard temperatures
6000’ 3°C
5000’ 5°C
4000’
7°C
3000’ 9°C
2000’ 11°C
Indicated Altitude = 4000’
OAT = 5°C
True Altitude is lower than Indicated
1000’ 13°C
MSL
15°C
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Pressure Error
IND ALT
IND ALT
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