DOC AIRBUS | AMM A320FELECTRICAL CLOCK - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
Universal Coordinated Time (UTC) is provided by a fully independent electrical clock with built-in time base, located on the R center instrument panel 400VU.
Moreover, the clock provides UTC in the form of an ARINC 429 format bus for the centralized fault display interface unit (CFDIU), the flight data interface unit (FDIU) and the two flight management and guidance computers (FMGC).
The clock is powered by two electrical circuits with one circuit directly connected to the aircraft battery. This enables time to be counted in memory throughout the period that aircraft is parked.
** ON A/C NOT FOR ALL Universal Coordinated Time (UTC) is provided by a fully independent electrical clock with built-in time base, located on the R center instrument panel 400VU.
Moreover, the clock provides UTC in the form of an ARINC 429 format bus for the centralized fault display interface unit (CFDIU), the flight data interface unit (FDIU) and the two flight management and guidance computers (FMGC).
The clock is powered by two electrical circuits with one circuit directly connected to the aircraft battery. This enables time to be counted in memory throughout the period that aircraft is parked.
2. Component Location
** ON A/C NOT FOR ALL | FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C ALL | |||||
| 2FS | CLOCK | 400VU | 212 | 31-21-21 | |
| 33LP | SW-INT LT/ANN LT | 25VU | 210 | 33-14-00 | |
3. System Description
A. General
This self-contained clock with built-in time base is contained in a 3 ATI case. It features the controls and the information related to each of the following functions :
This self-contained clock with built-in time base is contained in a 3 ATI case. It features the controls and the information related to each of the following functions :
- time (UTC) : display in hours and minutes on a digital counter
- elapsed time (ET) : display in hours and minutes on a digital counter
- chronometer (CHR) : display in seconds and minutes by means of a sweep hand and a digital counter respectively
- date : display in lieu and place of UTC display by action on a pushbutton switch.
- time (UTC) : display in hours and minutes on a digital counter
- elapsed time (ET) : display in hours and minutes on a digital counter
- chronometer (CHR) : display in seconds and minutes on a digital counter
- date : display in lieu and place of UTC display by action on a pushbutton switch.
B. UTC
UTC is displayed in digital form in the UTC window :
UTC is displayed in digital form in the UTC window :
- two digits for the hours (item 1)
- the two next digits for the minutes (item 2)
- the next single digit for the tenths of minutes (item 4).
- two digits for the hours (item 1)
- the two next digits for the minutes (item 2)
- the next smaller digits for the seconds (item 3).
(1) UTC switch
A four-position selector switch identified UTC (item 5), located in the R lower corner on the face of the clock, provides the four following functions:
A four-position selector switch identified UTC (item 5), located in the R lower corner on the face of the clock, provides the four following functions:
- RUN position : validation of the function : the counter starts normal operation
- HLDY position : holding the present display/setting of year
- MSM position : setting of minutes/setting of month
- HSD position : setting of hours/setting of day
(2) GPS/INT/SET switch
A three-position selector switch identified GPS/INT/SET, located in the right middle section of the face of the clock, provides the three following functions
(item 5):
Time is indicated up to 23 hours 59 minutes and 59 seconds.
A three-position selector switch identified GPS/INT/SET, located in the right middle section of the face of the clock, provides the three following functions
(item 5):
- GPS position: the time display is controlled by the GPS receiver
- INT position: the time display is controlled by the clock internal time base
- SET position: this position allows to set the clock internal time base
Time is indicated up to 23 hours 59 minutes and 59 seconds.
(3) Clock operation
| Initial position | New position | Clock displays and broadcasts to targets (FDIU, FDIMU, CFDIU, FMGC) |
|---|---|---|
| GPS | - | If GPS valid:
If GPS not valid:
|
| GPS | INT | If GPS valid:
If GPS not valid:
|
| SET | INT | Clock increments the internal time entered via SET mode. |
| SET | INT->GPS | If GPS valid:
If GPS not valid:
|
(4) Setting of time
(a) Setting of time is performed by placing the UTC selector switch successively in the following positions:
- HSD : the hours display (item 1) increments from 00 to 23 at a constant rate of one hour per second, while the minutes display stays the same and the tenths of minutes digit (item 4) changes to zero
- MSM : the minutes display (item 2) increments from 00 to 59 at a constant rate of one minute per second, while the hours display stays the same and the tenths of minutes digit changes to zero
- HLDY : the UTC display stands frozen
- RUN : the clock starts normal operation.
(5) Setting of time and date
NOTE: During setting of time or date, only the digits which are flashing can be set. The other digits are unchanged.
(a) Operating mode
- Increasing Setting: by rotation of the SET pushbutton switch, located in the left middle section of the face of the clock, clockwise.
- Decreasing Setting: by rotating of the SET pushbutton switch, counterclockwise.
C. Elapsed time (ET)
Elapsed time is displayed in digital form :
Operation of the ET counter is controlled by a three-position selector switch: RUN/STP/RST (item 6) and located in the right lower angle of the face of the clock.
Elapsed time is displayed in digital form :
- two digits for the hours (item 7)
- two digits for the minutes (item 6).
The elapsed time counter can totalize up to 99 hours 59 minutes.
Operation of the ET counter is controlled by a three-position selector switch identified ET (item 8) and located in the left lower angle of the face of the clock (two stable positions RUN and HLD, one spring-loaded position RESET with automatic return to HLD): - RUN position : counter runs
- HLD position : counter stops. Display is frozen.
- RESET position : the counter is reset to zero (momentary position) and displays go off.
- two digits for the hours (item 7 marked HR)
- the two next digits for the minutes (marked MIN).
Operation of the ET counter is controlled by a three-position selector switch: RUN/STP/RST (item 6) and located in the right lower angle of the face of the clock.
- RUN position: counter runs
- STP position: counter stops. Display is frozen
- RST position: the counter is reset to zero (momentary position) and displays go off.
D. Chronometer (CHR)
The CHR seconds are displayed in analog form by means of a pointer which completes a turn in 60 seconds, with one increment every second (item 11).
The CHR minutes are totalized in digital form (item 10).
The chronometer is controlled by a three-pressure pushbutton switch (item 9) identified CHR which can select three sequences when pressed (in) :
The CHR seconds are displayed in analog form by means of a pointer which completes a turn in 60 seconds, with one increment every second (item 11).
The CHR minutes are totalized in digital form (item 10).
The chronometer is controlled by a three-pressure pushbutton switch (item 9) identified CHR which can select three sequences when pressed (in) :
- First pressure : the pointer of seconds starts followed by the display of minutes.
- Second pressure : the pointer of seconds stops and the minutes are no longer totalized.
- Third pressure : the pointer of seconds is reset to 60 position. The display of minutes goes off.
- The CHR time is displayed in digital form on the upper window: minutes (item 10) and seconds (the next two digits marked SEC).
- The chronometer is controlled by a pushbutton switch located in the right upper corner of the clock face, identified CHR and which can select two sequences when pressed (in):
. First pressure: the chrono time starts counting followed by the minutes.
. Second pressure: the chrono time stops counting
to restart the CHR time the pushbutton RST (item 9) has to be pressed.
E. Date
- Date display
Date display is obtained by placing the UTC selector switch in the RUN position and pressing the DATE pushbutton switch (item 14).
The date is then displayed in lieu and place of the UTC display according to the following cycle: - Indication of the day (item 12) and the month (item 13) for one second, then blank for half second,
- Indication of the year for one second.
NOTE: The date is displayed only if specifically selected upon crew request or if set for updating purposes.
- Setting of date
The DATE pushbutton switch must be pressed.
Setting of date is performed by placing the UTC selector switch successively in the following positions: - HSD : the day display (item 12) increments at a rate of one day per second
- MSM : the month display (item 13) increments at a rate of one month per second
- HLDY : the two right digits of the year display increment at a rate of one year per second (the two left digits are blank)
- RUN : the clock starts normal operation.
- Display in lieu and place of UTC display:
Indication of the days by the right two digits
Indication of the months by the next two digits on the left
- Displayed in lieu and place of the seconds:
Indication of the year
- Date display
The date is displayed by pressing the DATE pushbutton switch when the time of the day is displayed.
NOTE: The date is displayed only if specifically selected upon crew request or if set for updating purposes.
F. Interface GPS/CLOCK
The clock is displaying the GPS time received from the GPS receiver when the GPS/INT SET switch is in the GPS position. If the signal from the GPS fails, the clock displays dashes, until the internal time base takes over. This internal time base starts counting from the last GPS time displayed. Furthermore if the last displayed time is erroneous, the time base starts counting from the time scheduled by the vendor at the first entry into service of the clock (generally 0h 0mn 0s 1st january). This means that as long as the GPS time is available, the internal time base cannot be set differently from the GPS time.
On the INT position, the clock displays the internal time base, but synchronized on the GPS time, until the GPS time fails.
The clock is displaying the GPS time received from the GPS receiver when the GPS/INT SET switch is in the GPS position. If the signal from the GPS fails, the clock displays dashes, until the internal time base takes over. This internal time base starts counting from the last GPS time displayed. Furthermore if the last displayed time is erroneous, the time base starts counting from the time scheduled by the vendor at the first entry into service of the clock (generally 0h 0mn 0s 1st january). This means that as long as the GPS time is available, the internal time base cannot be set differently from the GPS time.
On the INT position, the clock displays the internal time base, but synchronized on the GPS time, until the GPS time fails.
G. Internal Arrangement
Clock - Internal Block Diagram ** ON A/C NOT FOR ALL
Clock - Internal Block Diagram ** ON A/C NOT FOR ALL
Clock - Internal Block Diagram ** ON A/C NOT FOR ALL Clock - Internal Block Diagram ** ON A/C NOT FOR ALL 4. Interface
The clock provides UTC to the FMGC 1 and 2, the FDIU and the CFDIU. UTC is provided to the users in the form of an ARINC 429 bus.
Time is encoded to label 125 in BCD format and label 150 in BNR format.
Date is encoded to label 260 in BCD format.
Equipment identification is encoded to label 377 in HEX format (identification 031).
The clock provides UTC to the FMGC 1 and 2, the FDIU and the CFDIU. UTC is provided to the users in the form of an ARINC 429 bus.
Time is encoded to label 125 in BCD format and label 150 in BNR format.
Date is encoded to label 260 in BCD format.
Equipment identification is encoded to label 377 in HEX format (identification 031).
A. Sequence and Rating
Parameter sequence on the output bus is as follows :
Parameter sequence on the output bus is as follows :
(1) UTC in BCD format : label 125.
(2) UTC in BNR format : label 150.
(3) Date in BCD format : label 260.
(4) Equipment identification in HEX format : label 377.
The transmission rate is one parameter every 31.25 ms, the whole period being 125 ms.
The transmission rate is one parameter every 31.25 ms, the whole period being 125 ms.
5. Operation
A. Normal Conditions
- Instruments are powered normally
- Perform test of displays : place ANN LT switch located on panel 25VU in TEST position. Make certain that all displays show 8's (2 seconds on, 1 second off).
B. Failure Configuration
(1) Clock failure
- displays go off.
(2) Failure of electrical power supply - Loss of main electrical power supply (aircraft bus)
- Displays go off
- The chrono pointer stops
- ARINC output disabled
- Time is still counted in memory through the A/C battery supply.
- The pointer resumes its operation
- The correct time is displayed again.
(3) Failure of electrical power supply - Loss of main electrical power supply (aircraft bus)
- Displays go off
- ARINC output disabled
- Time is still counted in memory through the A/C battery supply.
- All pushbuttons are disabled.
- The correct time is displayed again.
(4) Failure of electrical power supply - Loss of aircraft battery power supply
The time keeping function is lost.
The time keeping function is lost.
(5) Failure of electrical power supply - Loss of aircraft battery power supply
The time keeping function is lost, but can be recovered through the GPS channel after the battery power has been restored (switch to GPS mode).
The time keeping function is lost, but can be recovered through the GPS channel after the battery power has been restored (switch to GPS mode).
(6) Failure of electrical power supply - Loss of main and aircraft battery power supplies
The clock does not operate.
The clock does not operate.