Navigation System Flashcards
How many laser ring gyros are used in the IN system?
3
Where is the GPS antenna located?
On the upper fuselage behind the rear cockpit.
Where do the INAV (INGPS) and RNAV (TACAN/ VOR/ ILS) feed their information?
To the DMCs (PDMC and SDMC).
What happens to the INGPS system if:
1) The GPS fails.
2) The INU fails.
1) System reverts to IN mode.
2) System reverts to GPS mode.
Name and briefly describe the errors associated with laser ring gyros.
Null shift: a rotation is detected where none exists due to impurities causing a false path difference.
Lock in: at low rotation rates, the frequencies of the beam are so similar that they can influence each other to become identical, causing false zero readings. Solved by dithering the gyro.
At what rate will the positional accuracy of the system degrade when in pure IN mode.
Much time conducting a GC Align is required to achieve this?
0.8nm per hour.
4 minutes.
The laser ring gyros are also connected to the head down heading indicator. If the INU fails it becomes a free gyro.
1) How much can this heading indicator drift by if the INU has failed?
2) How can this be corrected manually?
1) 15 degrees per hour.
2) Using the DG slew switch.
Name the 3 types of INU alignment.
Gyro Compass Align (GC ALIGN)
Stored Heading Align (SH Align)
Air Align (AIR ALIGN)
How long into a GC Align is degraded performance available?
How is this degraded performance accepted/ selected?
2 minutes.
By selecting “NAV” on top RH corner of the SETUP format, or by moving once available, but before full align is completed.
What happens if you taxi the aircraft:
Less than 120 seconds into a GH Align.
Between 120 and 240 seconds into a GH Align.
More than 240 seconds from the start of a GH Align.
INU enters air align mode.
Degraded nav accepted.
INU fully aligned - operate as normal.
What FOM numbers are shown as green?
1 and 2
What does a green FOM mean?
4 or more satellites are being tracked.
What does an amber FOM mean?
3 or fewer satellites are being tracked.
What does CEP stand for in an INGPS context?
Circular Error Probable.
