Instrument Study Flashcards
(143 cards)
How often must the altimeter system be tested and inspected?
Every 24 calendar months
What two fundamental concepts apply to gyroscopes?
- Rigidity in space
- Precession
Explain “rigidity in space” as it pertains to gyroscopes
This is the concept that a spinning wheel resists movement when mounted to gimbals, allowing the gimbals’ base to tilt, twist or otherwise move around the gyro.
Explain precession as it pertains to gyros.
When an outside for tries to tilt a spinning gyro, the gyro responds as if the force had been applied at a point 90deg further/later around in the direction of rotation.
How does precession affect certain flight instruments?
Unwanted precession is caused by friction in the gimbals and bearings of the instruments, causing a slow drifting in the heading indicator and occasional small errors in the attitude indicator
What errors do you find on attitude indicators?
- During coordinated turns, the gyro precesses toward the inside of the turn.
- When rolling out of a steep 180deg turn, the aircraft on the AI will show a slight climb and turn in the opposite direction. (This action is cancelled out after a 360deg turn)
- AI may indicate climb during acceleration and indicate a descent during deceleration
- When rolling out of a 180deg skidding turn, the AI shows a turn in the direction opposite of the skid
Standard Rate Turn Formula
Angle of Bank = (KTAS/10) + 5
i.e.
AoB = (60/10) + 5
9 = 6 + 5
Slipping Turn
Because of insufficient rudder pressure, the aircraft does not turn fast enough for it’s bank angle. The horizontal component of lift exceeds the centrifugal force which opposes the turn. As a result the inclinometer falls to the inside of the turn. (Think of a forward slip).
Skidding Turn
Excessive rudder pressure forces the aircraft to turn faster than normal for the bank angle. The horizontal component of lift is insufficient to overcome the centrifugal force. The inclinometer swings to the outside of the turn. (Think of cars drifting)
Magnetic Variation
The angular difference between true north and magnetic north.
Magnetic Deviation
Error due to magnetic interference with metal components in the aircraft.
Magnetic Dip
Tendency for magnetic compass to tilt downward. Most prominent at north pole.
Magnetic Compass Acceleration Error
ANDS
Magnetic Compass Turning Error
UNOS
CAS
Calibrated Air Speed
IAS corrected for installation and instrument errors.
EAS
Equivalent Airspeed
CAS corrected for adiabatic compressible flow at a particular altitude
TAS
True Airspeed
Actual speed aircraft moves through undisturbed air.
As density altitude increases, TAS increases for a given CAS or for a given amount of power. As the air becomes less dense (aka less effective/less drag) TAS increases
Types of altitude
- Indicated
- Calibrated
- Pressure
- Density
- True
- Absolute
Indicated Altitude
Altitude read from altimeter
Calibrated Altitude
Indicated altitude, corrected for instrument error
Pressure Altitude
Is displayed when altimeter set to 29.92”Hg. Vertical distance above Standard Datum Plane
SDP
Standard Datum Plane
Theoretical plane where atmospheric pressure = 29.92”Hg
Density Altitude
Pressure altitude corrected for nonstandard temperature
True Altitude
Actual height above MSL.