GYRO_STEERING.ppt

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GYRO STEERING

INTRODUCTION• MAGNETIC REFERENCE UNRELIABLE

CLOSER TO MAGNETIC POLES• UNCOMPENSATED GYRO USED AS

HEADING REFERENCE• HIGHLY ACCURATE GYRO MAKE

BETTER HEADING REFERENCE THAN BEST OF GYRO-MAGNETIC COMPASS

AIM

THE AIM OF THIS CLASS IS TO LEARN GYRO STEERING TECHNIQUE AND

USE OF UNCOMPENSATED GRYO AS A HEADING REFERENCE

TIE IN AND REVISION

GYRO DRIFT• REAL DRIFT• APPARENT DRIFT EARTH RATE = 15.04 X SIN λ (°/HR) TRANSPORT WANDER

= G/SPD X SIN TRK X TAN λ60

CORRECTION FOR DRIFT• REAL DRIFT –SYSTEMATIC DRIFTS CORRECTED

FOR DURING CALIBRATION.• RANDOM DRIFT CAN ONLY BE CORRECTED AS A

SHORT TERM MEASURE BY OBSERVATION OF DRIFT RATES OVER A SHORT PERIOD

• APPARENT DRIFT – CALCULATED AND APPLIED IN REVERSE SENSE.

• ON PLOTTING CHART, RESIDUAL APPARENT DRIFT DUE TO DIFFERENCE BETWEEN EARTH AND CHART CONVERGENCE REMAINS

= CHLONG [SIN MEAN LAT – n] (°/HR) WHERE N = CONSTANT OF THE CONE FOR THE PROJECTION

PHASE I

ADVANTAGES OF USING GYRO STEERING

• GYRO TRACK WILL BE A GREAT CIRCULAR TRACK

• THE PROBLEM OF USING MAGNETIC COMPASS AT HIGHER LATS

• USE OF GRIDED CHARTS WILL MAKE THE PLOTTING AND HEADING MAINTAINENCE EASIER

UNCOMPENSATED GYRO TECHNIQUE

• GYRO ALIGNMENT• GYRO DRIFT CORRECTION• GYRO STEERING• MAINTAINENCE OF AIRPLOT AND

TRACKPLOT• FIX PROCEDURES

UNCOMPENSATED GYRO TECHNIQUE

GYRO ALIGNMENT • INITIAL ALIGNMENT W.R.T. MAGNETIC

NORTH• INCASE USING A GRIDED CHART THEN

THE GYRO CAN ALSO BE ALIGNED TO THE GRID DATUM

• ALTERNATIVE METHOD IS TO ALIGN THE GYRO W.R.T. ASTRO HEADING CHECK OR BY DATUM POINTS ON GROUND

UNCOMPENSATED GYRO TECHNIQUE

GYRO DRIFT CORRECTION • APPARENT DRIFT RATE BE CALCULATED

AND AIRCRAFT HEADING ADJUSTED TO ALLOW FOR THE EFFECT OVER A PERIOD OF TIME, REAL DRIFT RATE IS OFTEN OF COMPARABLE VALUE, AND MAY BE OF OPPOSITE SIGN

• THEREFORE, DETERMINE TOTAL GYRO DRIFT RATE BEFORE MAKING ANY HEADING CORRECTIONS

GYRO DRIFT CORRECTION

• NUMERICALGYRO COMPENSATED FOR EARTH

RATE AT 30 DEG NHDG 045 ON LAT 60N SPEED 400 KTSREAL DRIFT 12DEG/HR• WHAT IS THE TOTAL GYRO DRIFT?

• 25 DEG DEG/HR

• IF AIRCRAFT FLIES SOLELY BY REFERENCE TO HIGH DRIFT RATE GYRO, IT WILL BE FOLLOWING A CURVED PATH, EVEN THROUGH INDICATED GYRO HEADING REMAINS UNCHANGED

GYRO STEERING

GYRO STEERING

• AIM OF UNCOMPENSATED GYRO STEERING IS TO CALCULATE AVERAGE HEADING THAT HAS BEEN FLOWN AND TO DETERMINE NEXT GYRO HEADING TO BE STEERED IN ORDER TO MAKE GOOD NEXT DR TRACK/HEADING

DEFINITIONS

• INITIAL HEADING TRUE OR GRID HEADING OF AIRCRAFT AT BEGINNING OF GYRO STEERING PERIOD.

• FINAL HEADING TRUE OR GRID HEADING OF AN AIRCRAFT AT THE END OF GYRO STEERING PERIOD. THIS HEADING MAY BE DETERMINED BY ASTRO.

• DIFFERENCE BETWEEN THIS AND INITIAL HEADING IS GYRO DRIFT FOR THE PERIOD

GYRO STEERING

DEFINITIONS

• DESIRED HEADING TRUE OR GRID HEADING DETERMINED BY NORMAL NAVIGATIONAL METHODS WHICH IS DESIRED TO FLY FOR SOME TIME AHEAD

• GYRO STEERING PERIODS PERIOD INTO WHICH A FLIGHT IS DIVIDED TO ASSESS AND ALLOW FOR GYRO DRIFT

GYRO STEERING

DEFINITIONS

• AVERAGE HEADING MEAN OF THE INITIAL AND FINAL HEADINGS FOR ANY REQUIRED PERIOD. IT IS USED TO MAINTAIN AIR PLOT IF REQUIRED. THE AIM OF GYRO STEERING IS TO KEEP AVERAGE HEADING AS CLOSE TO DESIRED HEADING AS POSSIBLE

GYRO STEERING

GYRO DRIFT DURING PERIOD

FINAL HEADING

INITIAL HEADING

AVERAGE HEADING ASSUMED THROUGHOUT

1030 1050

CONSTANT GYRO HEADING

GYRO STEERING

AVERAGE HEADING

GYRO STEERING

• USUALLY TIME INTERVAL BETWEEN TWO HEADING CHECKS IS APPROX 20 MINUTES, ENABLING HEADING TO BE READJUSTED TO COMPENSATE FOR GYRO DRIFT BEFORE AIRCRAFT IS FAR OFF- TRACK

GYRO CORRECTION GRAPH

• TOTAL DRIFT OF A GYRO AT ANY TIME IS EQUAL TO THE DIFFERENCE BETWEEN GRID HEADING AND GYRO READING

• GYRO DR=GRID HDG-GYRO READING• THIS DIFFERENCE IS COMPUTED AT THE TIME

OF HEADING CHECKS AND IS PLOTTED ON A GRAPH AS A GYRO CORRECTION

• THE GRID HEADING FOR ANY TIME CAN BE DETERMINED BY EXTRACTING THE GYRO CORRECTION FOR THAT TIME FROM THE GRAPH AND APPLYING IT TO THE GYRO READING

GYRO STEERING

GYRO CORRECTION GRAPH

• AVERAGE HEADING CAN BE FOUND BY EXTRACTING GYRO CORRECTION FOR MID TIME OF THE PERIOD AND APPLYING TO GYRO HEADING STEERED

• GYRO READING TO STEER IS DETERMINED

BY APPLYING AVERAGE CORRECTION EXPECTED FOR THE NEXT PERIOD TO DESIRED HEADING

GYRO STEERING

GYRO CORRECTION GRAPH

• AVERAGE CORRECTION IS PREDICTED BY EXTENDING THE GYRO DRIFT LINE TO MID TIME OF THE NEXT PERIOD

• HEADING CHECKS AND ALTERATIONS MAY BE ACCOMPLISHED AT ANY TIME, AND AS LONG AS GYRO READINGS STEERED ARE RECORDED, AVERAGE HEADINGS CAN BE COMPUTED

GYRO STEERING

ACTIVITY CYCLEPRE FLIGHT SET UP THE GYRO MODE OF

OPERATION. IT INCLUDES• SETTING LOCAL GRIVATION• SYNCHRONISING AND CHECKING

COMPASSES• SELECTING DG MODE OF OPERATION• ZEROING THE VSC• FINALLY CHECK ALL COMPASS READINGS

GYRO STEERING

ACTIVITY CYCLEIN FLIGHT, REGULAR CYCLE IS MAINTAINED.

IT INCLUDES• CARRY OUT ASTRO HEADING CHECK• CARRY OUT COMPASS COMPARISON• PLOT GYRO CORRECTION• PREDICT AVERAGE GYRO CORRECTION• ALTER HEADING AS REQUIRED TO

MAINTAIN TRACK

GYRO STEERING

ACTIVITY CYCLEIN FLIGHT, FIRST THREE HEADING CHECKS

TAKEN IN QUICK SUCCESSION TO ESTABLISH INITIAL ALIGNMENT ERROR AND ANY LARGE DRIFT TENDENCY. THEREAFTER A CYCLE OF 20 MIN IS FOLLOWED

GYRO STEERING

CALCULATION OF GYRO READING (GR) FOR A DESIRED GRID HEADING (GH) OF SAY 015° AND A PREDICTED AVERAGE GYRO CORRECTION (GC) OF + 7˚ WILL BE

GH – GC = GR 015° – (+ 7˚) = 008˚

GYRO STEERING

FIX PROCEDURES• NDB AND RELATIVE RADAR BEARING:

APPLY SPOT GYRO CORRECTION FOR THE TIME OF BEARING TO GYRO READING TO OBTAIN GRID HEADING. ADD BEARING TO GRID HEADING AND PLOT RECIPROCAL AS GRID BEARING

• GYRO / COMPASS ORIENTED RADAR BEARINGS: THESE WILL BE IN GRID AND WILL REQUIRE CORRECTION FOR GYRO ERROR

FIX PROCEDURES

• VOR AND TACAN: RADIALS CAN BE PLOTTED DIRECTLY FROM MAGNETIC MERIDIAN THROUGH THE STATION. IF DESIRE TO PLOT GRID BEARINGS, THEN MAGNETIC BEARING TO BE CONVERTED TO GRID BEARING BY APPLICATION OF THE VALUE OF GRIVATION AT STATION

FIX PROCEDURES

• PIN-POINTS: PIN-POINTS AND FIXES FROM HYPERBOLIC RADIO AIDS SHOULD BE TRANSFERRED FROM APPROPRIATE CHART TO GRID CHART IN TERMS OF THEIR GEOGRAPHICAL CO-ORDINATES

FULLY COMPENSATED GYROGYRO ALIGNMENT

• ACCURATE INITIAL ALIGNMENT OF GREAT IMPORTANCE

• PROBLEM OCCURS IF GYRO IS ALIGNED TO MAGNETIC DATUM

• SURVEYED SITES AND RELATIVE BEARING METHODS OR RUNWAY CENTRE LINE ADJUSTMENT ARE USED

FULLY COMPENSATED GYROGYRO DRIFT CORRECTION• METHOD OF CORRECTION DEPENDS ON

TYPE OF TORQUE CONTROL IN USE

• COMBINED EARTH RATE AND RESIDUAL TRANSPORT RATE CORRECTION CAN BE CALCULATED AND SET AS FALSE LATITUDE ON EARTH RATE CONTROLLER

FULLY COMPENSATED GYROGYRO STEERING• ONCE GYRO ALIGNED TO HEADING DATUM

AND DRIFT CORRECTION RATES SET, AIRCRAFT NAVIGATED BY MEANS OF NAVIGATION COMPUTER AND NORMAL FIXING AIDS

• AIRCRAFT HEADING SHOULD BE CHECKED APPROXIMATELY EVERY HALF HOUR

• DIFFERENCE BETWEEN GYRO READING AND AIRCRAFT HEADING SHOULD BE RECORDED

FULLY COMPENSATED GYROGYRO STEERING• OVER A SERIES OF CHECKS, AVERAGE

GYRO CORRECTION CAN BE CALCULATED

GYRO CORRECTION = GRID (OR TRUE) HDG – GYRO READING

• SMALL DRIFT RATE BE REMOVED BY SETTING A FALSE LATITUDE

• FOR LARGE DRIFT RATE (3° / HR), FOLLOW UNCOMPENSATED GYRO TECHNIQUE

FULLY COMPENSATED GYROPLOTTING POSITION LINES• GYRO CORRECTION VALUE FOR THE TIME

OF BEARING IS APPLIED TO GYRO READING TO OBTAIN HEADING

FULLY COMPENSATED GYROALTERATION OF HEADING• HEADING MAY BE ALTERED AT ANY TIME

• HEADING CHECK AFTER ALTERATION OF HEADING IS USED TO CALCULATE NEW GYRO DRIFT RATE

• HEADINGS FLOWN BEFORE AND AFTER TURN ARE OBTAINED BY APPLYING GYRO CORRECTION VALUES TO GYRO READING

FIX MONITORED AZIMUTH• FMA USED WHEN ACCURATE FIXES

AVAILABLE AND AIRCRAFT FITTED WITH FULLY COMPENSATED LOW DRIFT GYRO AND NAVIGATION COMPUTER FED FROM DOPPLER

• POSITIONS GIVEN BY COMPUTER ARE COMPARED WITH ACCURATE FIXES; ANY ACROSS TRACK ERROR IS ATTRIBUTED TO MISALIGNMENT OF HEADING REFERENCE

FIX MONITORED AZIMUTH• AMOUNT OF MISALIGNMENT MAY BE

DETERMINED

• GYRO OUTPUT TO NAVIGATION COMPUTER IS RE-ALIGNED AND COMPUTER IS RESET TO THE FIX CO-ORDINATES

• FMA TECHNIQUE REMOVES REQUIREMENT OF ASTRO HEADING CHECKS

FIX MONITORED AZIMUTH

• ACCURATE AIDS MUST BE AVAILABLE AND AIRCRAFT NAVIGATION SYSTEM MUST BE FUNCTIONING CORRECTLY

• OTHERWISE CALCULATED MISALIGNMENT WILL BE INCORRECT, SINCE FIX ERRORS AND DOPPLER ERRORS WILL BE INCLUDED IN THE CALCULATION

SUMMARY

QUESTION BY THE CLASS

QUESTIONS TO THE CLASSQUESTION

ANSWER

SUMMARY AND CONCLUSION