Instruments Flashcards
What are the (3) pitot static instruments?
1) Airspeed Indicator
2) Vertical Speed Indicator
3) Altimeter
How does the pitot static instruments work?
Pitot tube & static port
How does the Airspeed Indicator work?
uses ram air and static pressure.Air rams into the pitot tube and located in the pitot tube is an diapragm, which then expands. The diapragm expands the faster the airplane moves through the air (more air molecules), from there, the ASI calculates the difference from ram air pressure and static pressure to give us our airspeed by moving the linkages to give us indicated airspeed. The Pitot drain’s function is to let moisture or debris out so it does not clog the system.
How does the VSI work?
VSI is directly attached to the static system, which means means they work by sensing outside ambient air temperature. How it works is that, there is a diaphragm connected to the static lines. Diaphragm contracts as you increase altitude due to the pressure decreasing. As you descend altitude, there is more pressure, resulting in the diaphragm to expand and move the linkages to show a trend of descend. There is a slight delay due to the calibrated leak. *Instrument shows trends*
When climbing, air pressure decrease, therefore the diaphragm is contracting, which results in the VSI indicating a climb momentarily b/c of a calibrated leak, assisting in equalizing.
When descending, there is an increase in air pressure, thus causing air molecules going into the wafer, expanding it and as a result moving the linkages to indicate a descent on the VSI.
How does the altimeter work?
aneroid wafer located inside altimeter casing and sealed with standard pressure (29.92). When altitude increases the air molecules decrease, and pressure decreases, therefore the wafer expands (less air molecules in the case to squeeze the aneroird wafer) and the linkages move the needle to indicates a climb; vise versa on descent
What happens when the pitot tube is blocked?
pitot tube blockage means, no ram air is getting through and only the Airspeed uses ram air. Therefore the airspeed will act as an altimeter, increase during climb, decrease during descent
What happens if both pitot tube and static port is blocked?
Altimeter = frozen
VSI = frozen
Airspeed Indicator = frozen
How will flight instruments be affected when using alternate static air?
- The airspeed will indicate a speed greater than actual
- The altimeter will indicate a slightly higher altitude
- The VSI will show a climb until it has adjusted to the lower cabin pressure and then it will stabilize
What are the (3) Gyroscopic Instruments?
1) Attitude Indicator
2) Turn Coordinator
3) Heading Indicator
What happens if the static port gets blocked?
Altimeter = frozen at last reading
VSI = frozen at last reading
How does the Attitude Indicator work?
Attitude Indicator - powered by air, gives reference to the horizon as well as pitch & roll. Air rotates the gyro horizontally. To prevent attitude indicator from tumbling, a pendulus vein door allows air to escape, gravity then closes the door.
Describe the Turn Coordinator?
Turn Coordinator - powered by electricity for redundancy & backup, this is a canted gyro (at an angle), allows instrument to display quality of turn (coordinated or not).
1) quality & coordination of turn
2) rate of turn
How does the Heading Indicator work?
Heading Indicator - powered by air using the vacuum system, there are scoops located in the heading indicator that spin when air makes contact, when it spins, it spins the gyro which is oriented vertically. Functions on gyroscopic precession.
Gives us aircraft’s heading (references the magnetic compass aka magnetic heading)
Its gimbal allows only one axis of freedom (vertical) and connects the mount to the card on the instrument’s face through bevel gears. When the airplane begins to turn, the compass card on the front will begin to turn only when the gyro reacts to the yawing of the airplane during the turn.
How do the gyroscopic instruments work?
1) Rigidity in Space: ability to remain in a fix position in the plane that it’s spinning (table top spinner)
2) Precession: tilting or turning of a gyro in response to a force (force applied at a certain point isn’t felt until a later point)
What are the compass turning errors?
Turning Errors: UNOS
U - Undershoot
N - North
O - Overshoot
S - South
The further North or South the compass goes, the more pronounce the errors are b/c of magnetic dip.
What is magnetic dip?
the tendency of the compass’s magnet trying to align itself with the lines of earth’s magnetic field. Because earth’s magnetic fields are not parallel to the surface, the compass needle will point downward (dip) in the northern hemisphere and upwards in the southern hemisphere.
