PHAK 8: Flight Instruments Flashcards
Pitot-Static System
Which three instruments rely on the pitot-static system?
Airspeed Indicator (ASI)
Altimeter
Vertical Speed Indicator (VSI)
Pitot-Static System
What does the pitot-static system measure?
Static air pressure and dynamic pressure due to aircraft motion.
Pitot-Static Flight Instruments: Pitot Tube
What does the pitot tube measure?
Total pressure (dynamic + static pressure).
Pitot-Static Flight Instruments: Pitot Tube
What should be checked before flight regarding the pitot tube?
Ensure the openings are not blocked by debris, bugs, or moisture.
Pitot-Static Flight Instruments: Pitot Tube
What happens if the pitot tube’s openings are blocked?
The ASI will not function properly, potentially leading to incorrect airspeed readings
Pitot-Static Flight Instruments: Static Pressure
Where is static pressure vented from?
Through small holes on the side(s) of the aircraft into the static chamber.
Pitot-Static Flight Instruments: Static Pressure
What instruments utilize static pressure?
- Altimeter
- VSI (and as part of the ASI for dynamic pressure calculation)
Pitot-Static Flight Instruments: Alternate Static Source
Why is an alternate static source used?
To provide static pressure if the primary static source is blocked.
Pitot-Static Flight Instruments: Alternate Static Source
Where is the alternate static source located?
Inside the flight deck.
Pitot-Static Flight Instruments: Alternate Static Source
What errors can occur when using the alternate static source?
- Altimeter: Indicates higher altitude than actual.
- ASI: Indicates higher airspeed than actual.
- VSI: Momentary climb, then stabilizes.
Pitot-Static Flight Instruments: Alternate Static Source
What action can be taken if no alternate static source is available, and the primary source is blocked?
Break the glass face of the VSI, as it is the least critical static instrument.
Pitot-Static Flight Instruments: Dynamic Pressure
How is dynamic pressure generated?
By the aircraft’s motion through the air or wind relative to the aircraft.
Pitot-Static Flight Instruments: Dynamic Pressure
What role does dynamic pressure play in the ASI?
It is the remaining pressure after static pressure is canceled out, indicating airspeed.
Pitot-Static Flight Instruments: Maintenance Tip
Why are pitot tube covers used?
To prevent bugs, debris, or moisture from entering when the aircraft is not in use.
Pitot-Static Flight Instruments: Altimeter
What does the altimeter measure?
The height of an aircraft above a given pressure level.
Pitot-Static Flight Instruments: Altimeter
Why is the altimeter considered vital?
It is the only instrument capable of indicating altitude.
Pitot-Static Flight Instruments: Altimeter
What is the primary component of the altimeter?
A stack of sealed aneroid wafers.
Pitot-Static Flight Instruments: Altimeter
What pressure are the aneroid wafers evacuated to?
29.92 “Hg
Pitot-Static Flight Instruments: Altimeter
What happens to the aneroid wafers when static pressure increases?
They compress, indicating a decrease in altitude.
Pitot-Static Flight Instruments: Altimeter
What happens to the aneroid wafers when static pressure decreases?
They expand, indicating an increase in altitude.
Pitot-Static Flight Instruments: Altimeter
How is the movement of the wafers translated into altitude readings?
A mechanical linkage connects the wafers to the needles on the altimeter face.
Pitot-Static Flight Instruments: Altimeter
Where is static pressure introduced in the altimeter?
Into the rear of the sealed altimeter case.
Pitot-Static Flight Instruments: Altimeter
What is the role of the sealed outer chamber of the altimeter?
It allows the static pressure to surround the aneroid wafers for accurate readings.
Pitot-Static Flight Instruments: Altimeter
What happens if static pressure equals the pressure inside the wafers?
The wafers remain stable, and there is no change in altitude reading.