TM 1-1520-238-10 4-60 Change 4 4.30 CBHK DATA VALIDATION. NOTE If the fire control computer battery fails, boresight correctors will not be main- tained . Non-volatile parameter storage is accom- plished by means of Electrically-Erase- able Programmable Read-Only Memory (EEPROM) / . The fire control computer (FCC) continually monitors cer- tain critical internal values derived from the Captive Bore- sight Harmonization Kit (CBHK) boresight correctors. These critical values are used in the correction or adjust- ment of line-of-sight and weapons aiming. In the event of any alteration of these internal FCC values, the crew- members will be notified of the affected sight or weapons subsystem by a message in the HAD and FD/LS continu- ous monitoring. The appropriate message in the HAD will be displayed whenever the affected sight or weapon is selected. The FD/LS messages will be announced as part of the contin- uous tests described in paragraph 4.15, Fault Detection/ Location System. The effect on the selected sight or weapon will be that no correction to the line-of-sight or weapon aiming based on the CBHK correctors will be made. The sight or weapon will function normally but with- out apparent boresight correction or alignment. Validate the CBHK boresight correction values for the af- fected subsystem prior to using the subsystem. To check the FCC boresight corrector numbers, proceed as follows: 1. Place the DEK mode select switch to FD/LS / or press CDU FD/LS FAB . En- ter the letter B . The boresight menu page will be displayed as follows: TADS AL–20 VF–21 ED–22 GUN AL–23 VF–24 ED–25 PYLN AL–26 VF–27 ED–28 PNVS AL–29 VF–30 ED–31 The edit column (ED) is located to the right of the align (AL) and verify (VF) columns and is the only column the pilot will reference. The alignment, verification and edit numbers are established by armament personnel using the CBHK during aircraft systems boresight. 2. To check the boresight numbers in the FCC against the boresight numbers on the boresight page in the aircraft logbook, the aircraft must be on the ground with the FCC operational. To check the TADS, GUN, PYLN, or PNVS bore- sight numbers, enter 22, 25, 28 or 31 respective- ly. The selected system boresight edit numbers will be displayed in lieu of the menu page. For example, to check the PNVS boresight num- bers, enter 31. The boresight menu will blank and the PNVS edit page will be displayed as fol- lows: PNVS CORRECTORS -MR- EL +09.3 AZ –15.6 3. If the FCC numbers displayed match the log- book numbers, proceed to another system by entering a B, which recalls the boresight menu, and enter the next appropriate number for the desired system. The PYLN (ED-28) data is dis- played as one pylon number per page across four pages. To move from one pylon to the next sequentially, press the DEK SPACE key / or press CDU SPC KEY and the next pylon in sequence (1-4 repeated) will be dis- played. 4. If the FCC numbers displayed are not the same as the logbook numbers, the pilot must change the values to match the logbook values. The protocol used to access the edit numbers as- signs an integer (1, 2, 3, 4, . . ) to data locations on the page following the rule: left to right, top to bottom. The top left data location is addressed by entering a 1. The next data location to the right is addressed by entering a 2, etc. When a data location is addressed by the appropriate in- teger entry, the flashing cursor will move from the top left corner to the first digit in the data location. For example, using the PNVS page from above, if the elevation (EL) numbers were correct but the azimuth (AZ) numbers were not the same as the logbook values, the pilot would access the azimuth location by entering a 2. The flashing cursor would relocate beneath the 1 in –15.6. 5. Type in the logbook values. If the plus (+) or mi- nus (–) sign is not correct, use the DEK BKSP key / or CDU left arrow key to move the cursor beneath the sign and make the appropriate correction to match the logbook val- ues.