New Equipment
LRC
CN-1716/A
Fiber Optic Gyro System
(FOGS)
Attitude Heading Reference Unit
(AHRU)
New Equipment
LRC
CN-1716 (FOG)
will replace the three existing gyros
ASN-43(Direction Gyro)
CN-1314 (Vertical Gyro)
and TRU-2A/A (Rate Gyro)
What is AHRU?
LRC
•
The Fiber Optic Gyro System
(FOGS) is a self-contained strapdown Attitude Heading Reference
System (AHRS) that provides
accurate aircraft pitch, roll,
magnetic heading, and turn rate
information for integration within
an avionics subsystem.
How FOGS Work
LRC
Fiber Optics for Axial Reference
replacing the mechanical gimbaled gyros.
Accelerometers
electromechanically compensate & stabilize in flight
AHRU is a self latitude look up system.
Flux Valve provides initial reference in heading
- Post CCAL, flux valve provides updates
FOGS filter fluctuations of flux valve which
smoothes out the pitch, roll, and heading output.
“FOGS”
AHRU CN-1716/UH-60 Gyros Replacement
 New Digital Control
 Improved display and control capability
 Improved maintenance and diagnostics functions
 Spec Mean Time Between Failure: 6000 hrs.
Manufacturer Predicted MTBF: 15,000 hrs)
 Significant Simplification of Compass
Alignment (you don’t do anything!)
 Improved Navigational Accuracy
LRC
Interconnections
LRC
• FLUX VALVE
• NAVIGATION SET, AN/ASN-128
• HSI
• VSI
• AFCS
AHRU and ASN-128
LRC
• AHRU is not a navigator.
• Supplies information to Doppler in the
absence of GPS.
• Improves accuracy of ASN 128
Before
LRC
After
LRC
CN 1716
CN 1716
AHRU (FOGS)
AHRU (FOGS)
LRC
AHRU
AKA: FOG, SUE, MDU,
Lisa....
OUTPUTS
•Digital Arinc-429, RS-422: (Heading, Pitch, Roll,
Body Rates & Accelerations, Vertical Velocity)
•Synchro Arinc-407: (Heading, Pitch, Roll)
•Analog: (Yaw Rate, Validities, 2 Wires Attitude,
Interlock for Autopilot) ACCURACY
•Heading: 0.8 deg. Attitude: 0.5 deg
SENSOR ELECTRONIC UNIT (SEU) GENERAL
VIEW
LRC
“SEU”
aka
“FOG”
AHRU CN-1716/A
LRC
Before
LRC
Compass Controller
After
LRC
DIGITAL CONTROL PANEL (DCP)
LRC
Digital Control Panel
LRC
Display
Window
DG MODE
Indicator
CCAL MODE
Indicator
Alignment Mode
Indicator
SLAVED MODE
Indicator
MODE
Selector
Function
Selector
Display Cursor
Movement
Enter Selection
Button
CCAL = Compass Calibration
Failure
Indicator
AC Power Applied
LRC
Initial power on: All lamps illuminate for 2.5 seconds.
!! LOWER CONSOLE lights have to be ON !!
- DCP performs a lamp self-test / system MOC.
NO DISPLAY?
LRC
Turn Lower Console lighting
rheostat on to illuminate
DCP.
AC Power Applied
LRC
•
Initial power on: DCP is performing lamp self-test for 2.5 seconds, THEN:
• ALN lamp will be on
• ATT fail flag on the VSI will be in view
• AHRU will align and self-test within
45 seconds
AC Power Applied
After 45 seconds:
• the SYSTEM will automatically default to
the SLAVE mode
• and the VSI ATT warning flag disappears
LRC
BIT STATUS:FOG FAIL !
If the FAIL lamp appears –
The Display Window will show two BIT words:
a. LRU/SRU information and b. the failure code.
(Write up “AHRU Failed x amount of times”. It is not
necessary to write up the failure BIT info/code.)
The CDU stores the last 16 faults.
LRC
Starting Procedure
LRC
Step 1. Mode Selector – As desired.
(you always desire SLAVE while you are at FT Rucker)
a. The Lower Console lights have to be on for
the lights on the DCP to be seen.
b. The default mode is SLAVE – Therefore, you
should not have to move, touch or
otherwise fondle anything for it to be in the
SLAVE mode.
Starting Procedure
LRC
Step 1. Mode Selector – As desired.
(Continued)
Do Not select anything other than SLAVE!
Do Not select DG unless you are above 70°
Latitude (Be sure you have CAO approval to be out
of the LFA)
THOU SHALL NOT select CCAL!!
Starting Procedure
LRC
Step 2. HSI – Check to see that HSI heading
agrees with a known magnetic heading
(STANBY COMPASS).
If the HSI does not line up after the 45 second
alignment time + your patience -
Call Maintenance
Failures
LRC
If a failure is detected, the FAIL lamp will
illuminate, and the display window will show
a message indicating which AHRU has failed.
Press Enter to clear the fail light
If the fail light clears – continue mission
If fail light does NOT clear – Call maintenance
ELECTRICAL POWER
CHARACTERISTICS
• A Primary power interruption of less than 200
milliseconds does not cause a system realignment.
• Power interruptions more than 200 Milliseconds
CAUSE SYSTEM IN-AIR RE-ALIGNMENT
• The ATT and NAV warning flags will be in view to
indicate the system is doing a re-alignment.
• DURING THE RE-ALIGNMENT PHASE, MAINTAIN
STRAIGHT and LEVEL UNACCELERATED FLIGHT
(2.5 to 45 seconds)
LRC
“Hold the Controls”
LRC
NOTE
During aircraft shutdown,
• when engine power control levers are moved
from the Fly to Idle position, or
• when the generator switch position is
changed to off, and
• electrical power assignment is changed from
Main Generator to APU Generator,
• an un-commanded right or left
pedal drive of up to ¼ inch may
occur, returning to neutral position within 3
seconds.
CLTV NULL = YAW DRIFT
LRC
If the Collective Position Sensors are out of null
the aircraft will have a
greater tendency to yaw at hover
than with the older system.
YAW DRIFT
LRC
Write it up
especially if you have seen fail light
GYRO ERECT IN SLAVE MODE
LRC
FAST ERECT SYNC
may be activated in air to perform a
fast Heading error resetting in a
magnetic sterile area.
LRC
CCAL
This is a MAINTENANCE FUNCTION
Don’t go there!!
COMPASS CALIBRATION MODE
Lest ye be tempted
LRC
• Once CCAL begins it MUST be
completed!!! (You don’t know how)
• CCAL is ONLY used on ground.
• You CAN NOT get out of CCAL using the
MODE select button!!!
• HOLD THE CONTROLS!!!!!!
• (you don’t why but it can be ugly!)
• FOGS CAN NOT BE ZEROIZED
after initial calibration.
COMPASS CALIBRATION (CCAL)
MODE
LRC
• IN CCAL MODE THESE FUNCTIONS ARE ENABLED:
•
•
•
•
•
•
•
•
COMPASS CAL START
COMPASS CAL STORE
COMPASS CAL COEFFICIENTS READ
COMPASS CAL COEFFICIENTS WRITE
BIT STATUS REQUEST
BIT HISTORY REQUEST
INDEX SET REQUEST (NEVER CHANGE!)
ETI GET REQUEST
If you don’t know what this means –
why are you in CCAL?
CCAL
LRC
• Changing the index WILL degrade YOUR
SYSTEM!
• DO NOT “PLAY” WITH THIS TOOL
• THE ONLY WAY TO RECOVER FROM A
BAD CCAL IS TO PERFORM ANOTHER
CCAL
• LOG Index # AFTER CALIBRATION.
LRC
?? QUESTIONS ??