3C Airplane Systems - Pitot/Static Flight Instruments

Question 0

• DUPLICATE*

1. What instruments operate from the pitot/static system? (FAA-H-8083-15)

Answer 0

The pitot/static system operates the altimeter, vertical speed indicator, and airspeed indicator.

Question 1

2. Does this aircraft have an alternate static air system?

Answer 1

Yes. In the event of external static port blockage, a static pressure alternate source valve is installed. The control is located beneath the throttle, and if used will supply static pressure from inside the cabin, instead of from the external static ports.

Question 2

• DUPLICATE*

3. How does an altimeter work? (FAA-H-8083-15)

Answer 2

Aneroid wafers in the instrument expand and contract as atmospheric pressure changes, and through a shaft and gear linkage, rotate pointers on the dial of the instrument.

Question 3

• DUPLICATE*

4. A pressure altimeter is subject to what limitations? (FAA-H-8083-15)

Answer 3

Non-standard pressure and temperature:
a. Temperature variations expand or contract the atmosphere and raise or lower pressure levels that the altimeter senses.
On a warm day—The pressure level is higher than on a standard day. The altimeter indicates lower than actual altitude.
On a cold day—The pressure level is lower than on a standard day. The altimeter indicates higher than actual altitude.
b. Changes in surface pressure also affect pressure levels at altitude.
Higher than standard pressure—The pressure level is higher than on a standard day. The altimeter indicates lower than actual altitude.
Lower than standard pressure—The pressure level is lower than on a standard day. The altimeter indicates higher than actual altitude.
Remember: High to low or hot to cold, look out below!

Question 4

• DUPLICATE*

5. Define and state how you would determine the following altitudes. (FAA-H-8083-25)

Answer 4

Indicated altitude—the altitude read directly from the altimeter (uncorrected) after it is set to the current altimeter setting.
Pressure altitude—the altitude when the altimeter setting window is adjusted to 29.92. Pressure altitude is used for computer solutions to determine density altitude, true altitude, true airspeed.
True altitude—the true vertical distance of the aircraft above sea level. Airport, terrain, and obstacle elevations found on aeronautical charts are true altitudes.
Density altitude—pressure altitude corrected for nonstandard temperature variations. Directly related to an aircraft’s takeoff, climb, and landing performance.
Absolute altitude—the vertical distance of an aircraft above the terrain.

Question 5

DUPLICATE
6. How does the airspeed indicator operate? (FAA-H-8083-25)
It measures the difference between the impact pressure from the pitot head and atmospheric pressure from the static source.

Answer 5

It measures the difference between the impact pressure from the pitot head and atmospheric pressure from the static source.

Question 6

• DUPLICATE*

7. What are the limitations of the airspeed indicator? (FAA-H-8083-25)

Answer 6

The airspeed indicator is subject to proper flow of air in the pitot/static system.

Question 7

• DUPLICATE*

8. The airspeed indicator is subject to what errors?

Answer 7

Position error—Caused by the static ports sensing erroneous static pressure; slipstream flow causes disturbances at the static port, preventing actual atmospheric pressure measurement. It varies with airspeed, altitude, and configuration, and may be a plus or minus value.
Density error—Changes in altitude and temperature are not compensated for by the instrument.
Compressibility error—Caused by the packing of air into the pitot tube at high airspeeds, resulting in higher than normal indications. It is usually not a factor.

Question 8

• DUPLICATE*

9. What are the different types of aircraft speeds? (FAA-H-8083-25)

Answer 8

Indicated Airspeed (IAS)—the speed of the airplane as observed on the airspeed indicator. It is the airspeed without correction for indicator, position (or installation), or compressibility errors.
Calibrated Airspeed (CAS)—the airspeed indicator reading corrected for position (or installation), and instrument errors. CAS is equal to TAS at sea level in a standard atmosphere. The color-coding for various design speeds marked on airspeed indicators may be IAS or CAS.
Equivalent Airspeed (EAS)—the airspeed indicator reading corrected for position (or installation), or instrument error, and for adiabatic compressible flow for the particular altitude. EAS is equal to CAS at sea level in standard atmosphere.
True Airspeed (TAS)—CAS corrected for altitude and nonstandard temperature; the speed of the airplane in relation to the air mass in which it is flying.

Question 9

• DUPLICATE*

10. What airspeed limitations apply to the color-coded marking system of the airspeed indicator? (FAA-H-8083-25)

Answer 9

white arc - flap operating range
lower A/S limit white arc - VS0 (stalling speed or minimum steady flight speed in landing configuration)
upper A/S limit white arc - VFE (maximum flap extension speed)
Green arc - normal operating range
lower A/S limit green arc - VS1 (stall speed clean or specified configuration)
upper A/S limit green arc - VNO (normal operations speed or maximum structural cruise speed)
yellow arc - caution range (operations in smooth air only)
red line - VNE (never exceed speed; above this speed structural failure may occur)

Question 10

• DUPLICATE*
  11. What are some examples of important airspeed limitations that are not marked on the face of the airspeed indicator, but are found on placards and in the AFM or POH? (FAA-H-8083-25)

Answer 10

a. Design maneuvering speed (VA)
b. Landing gear operating speed (VLO)
c. Landing gear extended speed (VLE)
d. Best angle-of-climb speed (VX)
e. Best rate-of-climb speed (VY)

Question 11

• DUPLICATE*

12. How does the vertical speed indicator work? (FAA-H-8083-15)

Answer 11

The vertical speed indicator is a pressure differential instrument. Inside the instrument case is an aneroid very much like the one in an airspeed indicator. Both the inside of this aneroid and the inside of the instrument case are vented to the static system, but the case is vented through a calibrated orifice that causes the pressure inside the case to change more slowly than the pressure inside the aneroid. As the aircraft ascends, the static pressure becomes lower and the pressure inside the case compresses the aneroid, moving the pointer upward, showing a climb and indicating the number of feet per minute the aircraft is ascending.

Question 12

• DUPLICATE*

13. What are the limitations of the vertical speed indicator? (FAA-H-8083-25)

Answer 12

It is not accurate until the aircraft is stabilized. Sudden or abrupt changes in the aircraft attitude will cause erroneous instrument readings as airflow fluctuates over the static port. Both rough control technique and turbulent air result in unreliable needle indications.