Pitot Static System and Weather Flashcards
What is atmospheric pressure?
The force exerted by the weight of a column of air
What is standard sea level pressure in inches of mercury?
29.92
What is standard sea level temperature in degrees Celsius?
15° C
A change in 1 inch of mercury pressure is equal to approximately ____________________________ feet of altitude.
2°C/1,000’
What is the standard temperature lapse rate with altitude?
1,000
Define impact pressure.
Static pressure plus dynamic pressure
Define static pressure.
Ambient pressure
Which instruments depend on static pressure only?
VSI, altimeter
Which instrument depends on both impact (dynamic) and static pressure?
Airspeed indicator
What pressures affect the pitot static system?
Dynamic and Static
Name and define the three types of airspeed.
a. Indicated—read from the dial on the face of the instrument
b. Calibrated–IAS corrected for instrument and position error
c. True–CAS corrected for density error
Name and explain the three errors in the airspeed indicator.
a. Installation Error - Misalignment of the Pitot tube with the relative wind and position of the static vents
b. Density Error - Caused by pressure and temperature changes, air less dense as altitude increases
c. Instrument Error - Caused by friction in the instrument
Is the vertical speed indicator (VSI) a pressure differential measuring instrument?
Yes
What does the setting knob on the altimeter change when it is turned?
Kollsman setting and position of the needles
A change of .15 inch of mercury pressure is equal to _____ feet.
150
Define each of the following.
Indicated altitude-
True altitude-
Pressure altitude-
Absolute altitude
a. Altimeter indication
b. Altitude above MSL
c. Altitude above the standard datum plane (29.92” Hg)
d. Altitude above the terrain
Define altimeter setting.
Station pressure corrected to MSL
Why is an altimeter setting necessary?
To correct for pressure changes
What is the maximum allowable error in the altimeter?
Plus or minus 75’ (FAA), aviators should check operator or maintenance manual to confirm accurate limit for their aircraft.
When flying into an area of lower pressure without resetting the altimeter, would your true altitude be higher or lower than your indicated altitude?
Lower
When flying into an area of higher pressure without resetting the altimeter, would your true altitude be higher or lower than your indicated altitude?
Higher
If you depart a base with an altimeter setting of 29.82 and an hour later receive a new altimeter setting of 30.22, how much higher or lower than indicate altitude would true altitude be prior to adjusting the altimeter to the new setting?
400’ Higher than indicated altitude
At the last reporting point, you corrected the altimeter by setting the Kollsman scale on 29.92” Hg. Prior to landing, you received a new setting of 29.80. What is your true altitude in relation to indicated altitude (before you reset the altimeter)?
120’ feet lower than indicated altitude
When flying into an area of colder than standard temperature, would the indicated altitude will be more or less than true altitude?
More
In a thru e below, is true altitude higher, lower, or the same as indicated altitude? (NOTE: The standard temperature must be computed for each altitude first.)
Indicated Altitude Standard Temp Free-air Temp True Altitude
6,000 ____________ 3°C ____________
10,000 ____________ -35°C ____________
8,500 ____________ 10°C ____________
2,000 ____________ 0°C ____________
11,000 ____________ -7°C ____________
Standard Temp True Altitude
a. 3°C Same
b. -5°C Lower
c. -2°C Higher
d. 11°C Lower
e. -7°C Same
In a thru e below, is density altitude higher, lower, or the same as pressure altitude? (NOTE: The standard temperature must be computed for each altitude.)
Pressure Altitude Standard Temp Free-air Temp Density Altitude
7,000 ____________ 15°C _____________
9,000 ____________ -18°C _____________
5,500 ____________ 4°C _____________
3,000 ____________ -9°C _____________
12,000 ____________ -9°C _____________
Standard Temp Density Altitude
a. 1°C Higher
b. -3°C Lower
c. 4°C Same
d. 9°C Lower
e. -9°C Same
The _____________________________________________ (instrument) stops functioning properly due to pitot icing.
Airspeed Indicator
What is the recommended corrective action when the static system is clogged?
Switch to an alternate source.
High DA and low air density mean nearly the same thing. (True or False)?
True
What causes density error?
Nonstandard pressure and temperature.
Define true airspeed?
Calibrated Airspeed (CAS) corrected for density error.
Pressure High
Temperature Low
Humidity Low
More favorable for flight
More lift production
Increasing density
Low density altitude
Pressure Low
Temperature High
Humidity High
Less favorable for flight
Less lift produced
Decreases overall density
High density altitude
How many instruments use pressure?
All three
altimeter, vertical speed indicator VSI), and Airspeed
How many instruments use static pressure only?
2
altimeter, VSI
How many instruments use dual pressure?
1
Airspeed
How many instruments fail on a static pressure dump?
all three
How many instruments fail with a pitot tube blockage?
1 airspeed
What are the reportable ceilings for the FAA?
Broken and Overcast
9999
7 SM or greater
NSW
No significant weather
100857Z
RMK TSB18E50
Thunderstorms begin at 0818Z
Thunderstorms end at 0850Z
P6SM
Indicates visibility is 7 SM or greater (civilian TAFs only)
CB
Indicates the sky condition and is the only cloud type shown on TAF. ex: OVC020CB
Light =
Moderate =
Heavy =
Light = -
Moderate = No sign
Heavy = +
Precipitation DZ – RA – SN – SG – IC – PL – GR – GS – UP –
DZ – drizzle RA – rain SN – snow SG – snow grains (< ¼” diameter) IC – ice crystals PL – ice pellets GR – hail (>= ¼” diameter) GS – small hail (< ¼” diameter) UP – unknown precipitation
Proximity On Station (OS) –
Vicinity (VC) –
Distant (DSNT) –
On Station (OS) – within 5 SM of point of observation
Vicinity (VC) – between 5-10 SM of point of observation
Distant (DSNT) – beyond 10 SM of point of observation
Obscurations FG – BR – FU – VA – DU – SA – HZ – PY –
FG – Fog (vis <5/8 SM) BR – Mist (vis >5/8 SM) FU – Smoke VA – Volcanic Ash DU – Dust SA – Sand HZ – Haze PY – Spray
Descriptors MI – PR – BC – DR – BL – SH – TS – FZ –
MI – Shallow PR – Partial BC – Patches DR – Low Drifting BL – Blowing SH – Showers TS – Thunderstorms FZ – Freezing
If the sky is totally obscured, the ____ will be the ceiling.
If the sky is totally obscured, the vertical visibility will be the ceiling.
What are the three components of atmosphere density?
Temperature, pressure, and humidity
Two layers of ceilings?
Few and scattered
Lightning reporting
IC - in cloud
CC- cloud to cloud
CG - cloud to ground
SLP conversion
0-4=
5-9=
0-4= place 10 in front
5-9= place 9 in front
