Narrative:

During preflight at ZZZ, standby altimeter indicated approximately -85 ft than published ramp elevation. Allowable operations manual tolerance is -70 ft. After calling tower for the latest altimeter setting, maintenance was advised. Maintenance personnel troubleshot the system and after calling maintenance control determined that a new standby altimeter was required. Since parts were not available at ZZZ, they were shipping in on the next aircraft arriving from ZZZ1. After the new altimeter was installed, passenger were reboarded and we began another preflight. In checking the logbook, the captain noted that no leak check had been performed following replacement of the altimeter. In previous instances, he had seen that a leak check was always performed in conjunction with this type of maintenance. So, he queried the maintenance technician who stated that a leak check was not required. The captain asked to reconfirm this with maintenance control. The individual he spoke to stated that a leak check was, in fact, required. In subsequent phone calls, it was determined that there was a discrepancy between the boeing maintenance manual (which requires a leak check) and the air carrier manual, which states that no leak check is required for air data system components changed using quick disconnects. The captain was xferred to several individuals, attempting to confirm that the air carrier manual took precedence and that the term 'air data system component' included the standby instrument as well as components operated by the air data computer. After talking to several people, an individual at maintenance control confirmed this and we departed the station.

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Original NASA ASRS Text

Title: AN MD80 WAS DISPATCHED IN NON COMPLIANCE WITH A STANDBY ALTIMETER REPLACED BUT NO REQUIRED LOW RANGE LEAKAGE TEST PERFORMED.

Narrative: DURING PREFLT AT ZZZ, STANDBY ALTIMETER INDICATED APPROX -85 FT THAN PUBLISHED RAMP ELEVATION. ALLOWABLE OPS MANUAL TOLERANCE IS -70 FT. AFTER CALLING TWR FOR THE LATEST ALTIMETER SETTING, MAINT WAS ADVISED. MAINT PERSONNEL TROUBLESHOT THE SYS AND AFTER CALLING MAINT CTL DETERMINED THAT A NEW STANDBY ALTIMETER WAS REQUIRED. SINCE PARTS WERE NOT AVAILABLE AT ZZZ, THEY WERE SHIPPING IN ON THE NEXT ACFT ARRIVING FROM ZZZ1. AFTER THE NEW ALTIMETER WAS INSTALLED, PAX WERE REBOARDED AND WE BEGAN ANOTHER PREFLT. IN CHKING THE LOGBOOK, THE CAPT NOTED THAT NO LEAK CHK HAD BEEN PERFORMED FOLLOWING REPLACEMENT OF THE ALTIMETER. IN PREVIOUS INSTANCES, HE HAD SEEN THAT A LEAK CHK WAS ALWAYS PERFORMED IN CONJUNCTION WITH THIS TYPE OF MAINT. SO, HE QUERIED THE MAINT TECHNICIAN WHO STATED THAT A LEAK CHK WAS NOT REQUIRED. THE CAPT ASKED TO RECONFIRM THIS WITH MAINT CTL. THE INDIVIDUAL HE SPOKE TO STATED THAT A LEAK CHK WAS, IN FACT, REQUIRED. IN SUBSEQUENT PHONE CALLS, IT WAS DETERMINED THAT THERE WAS A DISCREPANCY BTWN THE BOEING MAINT MANUAL (WHICH REQUIRES A LEAK CHK) AND THE ACR MANUAL, WHICH STATES THAT NO LEAK CHK IS REQUIRED FOR AIR DATA SYS COMPONENTS CHANGED USING QUICK DISCONNECTS. THE CAPT WAS XFERRED TO SEVERAL INDIVIDUALS, ATTEMPTING TO CONFIRM THAT THE ACR MANUAL TOOK PRECEDENCE AND THAT THE TERM 'AIR DATA SYS COMPONENT' INCLUDED THE STANDBY INST AS WELL AS COMPONENTS OPERATED BY THE AIR DATA COMPUTER. AFTER TALKING TO SEVERAL PEOPLE, AN INDIVIDUAL AT MAINT CTL CONFIRMED THIS AND WE DEPARTED THE STATION.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.