Instruments And Ilusions Flashcards
Gyroscopic instruments
two principles. There has to be a source of power to keep the gyro spinning. With vacuum system the attitude and heading indicator is driven by the vacuum system. The turn coordinator is electrically driven for redundancy. The gyro spins on a horizontal plane. Dual gimbal, gimbal rotation, roll gimbal, pitch gimbal gyro, horizontal reference arm, and bank index
Gyroscopic principle 1: Rigidity in Space
a wheel with a heavily weighted rim tends to remain in the plane in which it is spinning unless acted on by an outside force. No matter where you move the base of the gyro it will remain in the plane
Gyroscopic principle 2: Procession
any force applied to a gyro or a spinning object will be felt 90 degrees ahead in the plane of rotation
Principles and instruments
Attitude indicator- rigidity and space
Heading indicator- rigidity and space
Turn coordinator- procession
Vacuum pump
Relies on vacuum pressure through a vacuum pump to create suction to spin gyroscopes. Pulls through an air filter to the instruments and then to a relief valve then to an overboard vent.
Vacuum pump errors
Indication of low vacuum, suction gauge reading low, 4.8-5.2in hg is normal.
If it completely fails the attitude indicator will fall off.
Heading indicator will freeze and won’t move. Auxiliary driven pump is back up.
Shear drive on the vacuum pump breaks off if the vacuum goes to fats, this is a plastic piece on the vacuum pump
Attitude Indicator
Consist of miniature aircraft
Principle of operation- shows direct indication of pitch and bank. Operates in the principle of rigidity and space.
The gyro spins on a horizontal plane mounted on dual gimbal
Pendulous vane- located at the bottom of the gyro corrects for unwanted procession. It deflects the other way for correction. Depends if the inlets are open or closed. Open due to gravity when the gyro strays away from horizontal
Rigidity and space
Attitude indicator Errors
The forces placed on the gyro
Acceleration/deceleration- Acceleration slight pitch up, deceleration slight pitch down
Instrument tumbling- 60 degrees of pitch or 100 degrees of bank. The instrument will tumble and won’t become reliable. It will keep spinning. Caging stops the gyro from spinning and spinning
Maximum when rolling out of a 180 degree turn- Show a false pitch and bank in the opposite direction. 360 degrees it will cancel.
Attitude indicator preflight check
Attitude Indicator up and erect within 5 minutes
No more then 5 degrees bank or one bar of pitch on taxi turns
Miniature aircraft set to horizon
Heading Indicator
Provides heading information (magnetic compass) Magnetic North
Heading Indicator Principles of operation
Primary source for heading information
Operates on the principle of rigidity in space
Senses aircraft movement about the vertical axis (yaw)
Slaved vs Free gyros. Slave automatically aligns to the magnetic compass. Free gyros manually has to be set to the magnetic compass
Gyro mounted in the vertical plane so it spins vertical plane
Dual gimbals are required because the a/c rolls and yaws
Keeps the gyro fixed in the vertical plane
Doesn’t have a mechanism to correct for precession
Heading Indicator Errors
Procession causes the heading indicator to drift from its set heading. It’s kind of like friction is always messing with it.
Reset with Magnetic compass every 15 minutes. Due to the earth’s rotation
Only in straight and level unaccelerated flight it will be most accurate
Heading Indicator Preflight Check
Heading aligned with magnetic compass
Doesn’t process more than 3 degrees in 15 minutes
Turn Indicator
Both show quality of turn Inclinometer. Works on the principle of procession
Turn and Slip indicator:
Rate of turn information only
Mounted vertically
Turn coordinator:
Rate of turn and rate of roll information
Mounted canted (30 degrees)
Turn Indicator Principle of Operation
Operates on the principle of precession
Allows the pilot to establish and maintain standard rate turn 3 degrees per second/ 2 minutes 360, 1 minute 180, 30 seconds 90 degrees, 15 sec 45 degrees, 10 second 30 degrees.
Equation (TAS/10) + 5 = Angle of Bank
Slip- ball on the inside of the turn. Not enough rate of turn for the amount of Bank
Skid-ball on the outside of the turn. Too much rate of turn for the amount of bank
Turn indicator Preflight check
Inclinometer full of fluid and centered
Wings level while stationary
Skidding turn on the ground
Wings into the turn, ball on the outside
Magnetic Compass
is the most primal and basic instruments used by the pilot to determine or verify aircraft heading. The instrument operations on the principles of magnetism. Can’t freeze because the fluid is kerosene.
Magnetic Compass Errors: Deviation
Due to interference to magnetism in the aircraft. Need a Magnetic deviation card in A/C
Magnetic compass error: Variation
also known as declination errors, stem from the disparity between magnetic north and true north. This difference varies depending on geographical location and must be accounted for during navigation
Magnetic compass errors: Magnetic dip theory
Dip errors are caused by the tilt of the compass needle caused by the Earth’s magnetic field. As one moves closer to the magnetic poles, the compass needle’s dip angle increases, leading to inaccuracies.
Magnetic compass errors Oscillation
Oscillation errors refer to the unwanted swinging or movement of the compass needle, often caused by rough sea conditions or turbulent flight paths.
Magnetic compass error North/South Turning Errors
North lags and south leads. UNOS, undershoot north overshoot south
Magnetic compass error Acceleration/Deceleration
Shows Acceleration to the north, shows decelerate south only on a East or West heading
Airspeed indicator
used in an aircraft to display the craft’s airspeed, typically in knots. Airspeed indication is accomplished with the use of a thin, corrugated phosphor bronze diaphragm (aneroid) which measures the Dynamic Pressure of the air between the Pitot tube (ram air) and static port (static pressure)
Airspeed indicator Preflight
0 Taxi unless strong head wind
Call alive on takeoff
Types of Airspeed: Indicated
Airspeed directly off the airspeed indicator
Types of Airspeed: Calibrated
corrected for position and instrument error. Errors such as AOA, flap configuration, ground proximity, wind direction.
Types of Airspeed: Equivalent
corrected for calibrated airspeed at airspeed above 200 knots and altitudes above 20,000
Types of Airspeed: True airspeed
speed of the a/c relative to the calibrate airspeed corrected.TAS is therefore CAS corrected for non-standard temperature, with the help of an Outside Air Temperature (OAT) gauge, and altitude
Types of Airspeed: Ground speed
is the actual speed of the airplane over the ground
Altimeter
is a type of barometer which measures the vertical distance to the surface, necessary for a pilot to maintain the desired or assigned altitude during flight. Stack of sealed aneroid wafers (29.92)
Static source to the case of the instrument