CHAPTER 3 How Do Those Instruments Work? Flashcards
What are the Compass Errors?
UNOS and ANDS
Turning Errors: U - Undershoot, N - North, O - Overshoot, S - South; Dip Errors: A - Accelerate, N - North, D - Decelerate, S - South
What is Variation in navigation?
The difference between true and magnetic directions
Isogonic lines identify the number of degrees of variation in that area
What is Deviation in navigation?
Compass error caused by aircraft magnetic fields
A compass card will correct for this error
What is Oscillation in relation to the compass?
Combination of all compass errors resulting in fluctuation of the compass card
Use the average indication between swings to set the aircraft heading indicator
How do you ensure that the altimeter is functioning properly?
Set it to the current altimeter setting
The altimeter must read within 75 feet of field elevation to be used
What is Indicated Altitude?
The value read directly from the altimeter when set to the current altimeter setting
What is Pressure Altitude?
Altitude read if the altimeter is tuned to the standard pressure value of 29.92” Hg
Used for flights at 18,000 feet MSL and above
What is True Altitude?
The height flown by the aircraft above sea level (MSL)
What is Density Altitude?
Pressure altitude corrected for non-standard temperature
High density altitude indicates low air density, affecting aircraft performance
What is Absolute Altitude?
Actual height above ground level (AGL)
True altitude minus the elevation of the terrain below the aircraft
What are some limitations of the heading indicator?
Precession or drift affecting proper heading
Standard practice to compare with the magnetic compass every 15 minutes
What is the difference between skidding and slipping?
Skidding: turning too much for the bank; Slipping: insufficient turn rate for the bank
Skidding indicates too much bank, while slipping indicates too little
How should a pilot prepare the heading indicator for IFR flight?
Set the heading indicator to the aircraft’s magnetic heading five minutes after engine start
How do you check for errors in the attitude indicator?
Check the horizon bar five minutes after engine start
The horizon bar should be up and stable, not tilting more than 5 degrees while taxiing
What errors occur in an attitude indicator?
Precession errors during turns and acceleration/deceleration errors
During acceleration, it shows a climb; during deceleration, it shows a descent
What happens if the pitot tube and drain hole are blocked?
Airspeed indicator acts as an altimeter, showing static pressure only
What happens if only the pitot tube is blocked?
The airspeed indicator shows zero airspeed
What happens if only the static port becomes blocked?
Airspeed indicator continues to operate but is inaccurate
Above blockage altitude shows lower airspeed; below shows higher airspeed
What does the Distance Measuring Equipment (DME) do?
Gives slant range distance in nautical miles from the aircraft to the station
Prone to errors when flying directly over a VOR
When is DME most accurate?
Smallest error at low altitude and/or long ranges
Should be at least a mile from the facility for every 1,000 feet of altitude
Where can pilots find information on VOR receiver ground checkpoints?
From the Chart Supplement
How do you check for VOR error over FAA-designated airborne checkpoints?
Center the CDI needle before flying over the checkpoint
What is the maximum allowable error for VOR receivers on the ground?
+/- 4°
+/- 6° over designated airborne checkpoints
How often must a VOR operational check be performed?
Once every 30 days
Must record checks in the aircraft log
