T-45C TS, ADV, & IUT RIFP-01
Introduction to Radio Instruments
VII. Computing ground speed using TACAN/VOR DME
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INTRODUCTION TO RADIO
NOTE: To be able to compute ground speed while
maintaining a course to or from a TACAN/VORTAC
* SID procedures
station, the DME from station must be greater than
* Radial intercept procedures
or equal to the aircraft altitude in thousands of feet.
* Indications of station passage
* TACAN/VOR DME arc
60 = GROUND SPEED
* Voice procedures
* Ground speed computation
* Wind drift correction
EXAMPLE: If the altitude is 30,000 ft (FL 300), DME
should be 30 nm or greater.
* Pt-to-Pt procedures
* Direct to a NAVAID
Start timing with a whole number in DME
* VOR-TACAN/VOR DME
After predetermined time (in minutes), check
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and note DME
------------------------ X 60 = GROUND SPEED
Determine distance flown (every 1/10 nm equals
6 kts) and multiply distance by a number that
RULE: DME must be greater than or equal to the
aircraft altitude in thousands of feet.
corresponds to the amount of time traveled to
GROUND SPEED CALCULATION
get ground speed
EXAMPLE: Your distance flown is 6 on the
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DME indicator. Elapsed time is 1 minute, so 6
times 60 equals 360. Ground speed is 360 kts
(6 nm/min times 60 min/hr equals 360 nm/hr).
NOTE: The ground speed check requires
tracking directly to or from the station.
NOTE: To increase accuracy, check ground
speed for more than 1 minute.
The current calculated ground speed is shown
on the HSI display and the HUD navigation