Narrative:

#1 VOR system was weak and there were no parts available. The system was then deferred to MEL which states one may be inoperative provided: 1) system or component is not supplied by an emergency power source, and 2) system or component is not required to accomplish an emergency procedure. My interpretation is that the #1 VOR system is pwred by the standby dc power system which, according to the maintenance manual, provides 28 volts dc to those system required to maintain safe flight. According to air carrier operating manual, it states that a battery is installed to supply emergency dc power to certain critical loads when the basic source is de-energized. Again the standby dc power system is not mentioned. It is very vague when trying to determine exactly what is meant by the terminology of an emergency power source. If this is meant to be a critical issue then the dispatch deviations procedure guide should specifically state that the #1 VOR system cannot be dispatched inoperative and the #2 VOR system can. In reference to this issue, I was not informed of this entire issue until jun/xx/97. At that time I was informed that a new crew boarded the airplane in xyz and stated that the #1 VOR system was deferred incorrectly and it could not be dispatched until it was corrected. It was then repaired and dispatched. The company later disclosed to the FAA that they had made a mistake and the FAA then turned around and said that they would conduct an investigation pertaining to this matter.

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Original NASA ASRS Text

Title: A B747-100 WAS DISPATCHED WITH THE #1 VOR SYS DEFERRED AS INOP IN CONFLICT WITH THE MEL.

Narrative: #1 VOR SYS WAS WEAK AND THERE WERE NO PARTS AVAILABLE. THE SYS WAS THEN DEFERRED TO MEL WHICH STATES ONE MAY BE INOP PROVIDED: 1) SYS OR COMPONENT IS NOT SUPPLIED BY AN EMER PWR SOURCE, AND 2) SYS OR COMPONENT IS NOT REQUIRED TO ACCOMPLISH AN EMER PROC. MY INTERP IS THAT THE #1 VOR SYS IS PWRED BY THE STANDBY DC PWR SYS WHICH, ACCORDING TO THE MAINT MANUAL, PROVIDES 28 VOLTS DC TO THOSE SYS REQUIRED TO MAINTAIN SAFE FLT. ACCORDING TO ACR OPERATING MANUAL, IT STATES THAT A BATTERY IS INSTALLED TO SUPPLY EMER DC PWR TO CERTAIN CRITICAL LOADS WHEN THE BASIC SOURCE IS DE-ENERGIZED. AGAIN THE STANDBY DC PWR SYS IS NOT MENTIONED. IT IS VERY VAGUE WHEN TRYING TO DETERMINE EXACTLY WHAT IS MEANT BY THE TERMINOLOGY OF AN EMER PWR SOURCE. IF THIS IS MEANT TO BE A CRITICAL ISSUE THEN THE DISPATCH DEVS PROC GUIDE SHOULD SPECIFICALLY STATE THAT THE #1 VOR SYS CANNOT BE DISPATCHED INOP AND THE #2 VOR SYS CAN. IN REF TO THIS ISSUE, I WAS NOT INFORMED OF THIS ENTIRE ISSUE UNTIL JUN/XX/97. AT THAT TIME I WAS INFORMED THAT A NEW CREW BOARDED THE AIRPLANE IN XYZ AND STATED THAT THE #1 VOR SYS WAS DEFERRED INCORRECTLY AND IT COULD NOT BE DISPATCHED UNTIL IT WAS CORRECTED. IT WAS THEN REPAIRED AND DISPATCHED. THE COMPANY LATER DISCLOSED TO THE FAA THAT THEY HAD MADE A MISTAKE AND THE FAA THEN TURNED AROUND AND SAID THAT THEY WOULD CONDUCT AN INVESTIGATION PERTAINING TO THIS MATTER.

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.