1、PRINCIPLES OF INSTRUMENT FLIGHTFlight Instrument SystemsGyroscopic InstrumentslAll required for VFR Flight-plus:“GRABCARDD”91.205(d)&(e)G enerator or alternator R adios:Two-way Communication AND navigation equipment appropriate to facilities used A ltimeter(adjustable)B all(slip&skid indicator)C loc
2、k A ttitude Indicator R ate of turn indicator D irectional gyro DME at&above FL 240Equipment tests&inspections required for IFR Airworthiness Directives(recurring/one-time)VOR(preceding 30 days)Inspections(Annual/100 hour if for hire)Altimeter(preceding 24 calendar months Transponder(preceding 24 ca
3、lendar months)ELT(preceding 12 calendar months)Static system(preceding 24 calendar mo.)Gyroscopic Flight InstrumentsAttitude Indicator-Heading Indicator-Turn CoordinatorFlight Instrument Systems Vacuum SystemAttitude Indicator&Heading Indicator Electrical SystemTurn CoordinatorServes as backup in ca
4、se of vacuum system failureVacuum SystemVACUUM SYSTEMGyroscopic PrinciplesRigidity in SpacePrecessionRigidity in Space A wheel spinning rapidly tends to remain fixed in the plane in which it is spinning.Gimbals allows the gyro to rotate freely in any plane Gives us a center of reference that doesnt
5、change with aircraft attitudeGyro stays fixed as aircraft moves around itPrecession Apply a force on a spinning gyro,its effect will be felt at the 90 degree position in the plane of rotation.Caused by friction:-in gimbals-in bearingsResults in:-1)slow drifting in HI and-2)occasional small errors in
6、 AIAttitude Indicator Shows aircraft pitch and bank attitude Does NOT show if the aircraft is turning,climbing or descendingATTITUDE INDICATORHow an AI Works Principle of operation:-RIGIDITY IN SPACE Gyro spins in plane on a vertical axis Mounted on dual gimbals so that aircraft can pitch and roll a
7、round gyro Gyro stays level with natural horizon there is a self-erecting mechanism actuated by the force of gravity on“pendulous vanes”to keep it level*(see next slide)The self-erecting mechanism in the gyroscopic attitude indicator The force of gravity acting on the“pendulous vanes”allows the gyro
8、 to align itself with the natural horizonPendulous Vanes Sole purpose is to keep the gyro ERECT.Air exits the gyro assembly through 4 ports at right angles near the base.Vanes open and close these ports by the swinging effect like a pendulum responding to gravity.Results in differential thrust causi
9、ng precession forces which right the gyro to desired planeTurns and G forces The pendulous vanes operate asymmetrically under:LoadCentrifugal force Results in a variety of typical gyroscopic precession errors Error usually maxes out after 180 turn-cancels after 360 turnAcceleration/Deceleration Erro
10、rs Example-accelerateHorizon bar moves downIncorrectly indicates a climbConfirmed by pilots somatogravic illusionResponse(“get the nose down”)Danger potential at takeoff or missed approach when required obstacle climb angle isnt sufficientTumbling Gyros Older AI indicators can tumble.Gimbals reach t
11、heir limits resulting in gyros precessing rapidly.Tumbles away from desired plane of rotation Exceeding 100 bank or 60 pitch(on older models)Caging devices were necessary for acrobatic flight to prevent tumbling Newer Attitude Indicators do not have the same limits so no cagingHeading Indicator Indi
12、cates heading based on a 360 degree azimuth Must regularly be reset to agree with the magnetic compassHow An HI Works Vacuum powered Gyro spins on plane Senses rotation about the vertical axis Free vs.Slaved gyrosfree,must align with magnetic compassslaved,automatic north-seekingHeading IndicatorHI
13、Errors Precession:Check HI every 15 minutes with mag compass Airplane does more than yaw,so 2 gimbals needed for free rotation.Can also tumbleTURN COORDINATOR Operates on principle of gyroscopic precession-Electrically DrivenStill usable after a vacuum failure-Provides direction of turn,rate of turn
14、,rate of roll,and QUALITY of turn(coordinated use of aileron and rudder)Two Types Turn-and-Slip IndicatorOnly shows rate of turnGyro rotates in vertical plane along a/c longitudinal axis Turn CoordinatorIndicates rate of turn AND rate of roll-Gyro is canted 30 degrees to allow for measuring the roll
15、 and yaw of the airplane Both instruments give indirect indication of bankSlip and SkidSlip rate of turn is too slow for AOB ball inside turn-(HCL is too great)Skid rate of turn is too great for AOB ball outside turn-(too much Centrifugal force)Slip Skid CoordinatedSRT Standard rate turn is 3/sec An
16、gle Of Bank increases with TAS Standard Rate AOB rule of thumb:(TAS/10)+1/2TC Checks Listen for unusual noise before starting engine Look for red,warning,or OFF flags Ammeter after start for positive charging rate Inclinometer ball-outside of turn Turn needle-with turnMagnetic CompassSelf containedD
17、irection seekingSubject to many Compass ErrorsMagnetic Compass ErrorsVariationDeviationMagnetic DipOscillationNortherly Turning ErrorAccelerationThese are both due to Magnetic DipMagnetic VariationDifference between True North&Magnetic NorthIsogonic lines:equal variation Agonic line:0 variationDevia
18、tion Metals and magnetic fields in the airplane interfere with north-seeking ability Compensating magnets eliminate some of the error.Swinging the compass adjusts them.Leftover error is handled through a compass correction card for each individual airplane.Magnetic Dip Exists because compass magnet
19、tries to point 3 dimensionally toward the earths magnetic north pole deep inside the earth.“Northerly Turning”and“Acceleration”errors are due to magnetic dipWhen rolling out to North or South Heading.“UNOS”Undershoot North-Overshoot Southbased on latitude and 1/2 bank angleWhen initiating a turn FRO
20、M North or South HeadingNorth OppositeSouthExaggerateNORTHERLY TURNING ERRORS“North Opposite”Compass initially shows turn in opposite direction“South Exaggerate”Shows turn in proper direction but compass card moves faster than actual rate of turnOscillation Erratic movement of the magnetic compass card Caused by turbulence or rough control movementAcceleration Errors(East or West)“ANDS”AccelerateNorthDecelerateSouthAcceleration Errors on East/West Headings
