Narrative:

During review of flight release; preflight duties we discovered the aircraft had a minimum equipment item that deferred the flight-deck-to-ground; service interphone system. We reviewed the MEL and noted that we would have to use hand signals and prior coordination with ground support personnel during engine start and taxi. This flight was scheduled as a quick-turn and maintenance did not plan on any repair of the interphone system.during cockpit preflight duties; the first officer discovered the cockpit oxygen mask interphone system was inoperative. We tested both the cockpit speaker system and headphone system at both seats and discovered all systems were inoperative. We checked the service interphone system and it was also inoperative. I immediately called the company dispatcher and advised him of our situation. He called me back several minutes later and stated that maintenance advised him the MEL was appropriate for our situation and it was airworthy at that point. I disagreed with their assessment. The first officer and I agreed the MEL was not germane to our problem. The dispatcher then suggested we solicit the help of a company sme (subject matter expert). I agreed and was called later by the sme. When the sme called I discussed my situation; he then discussed the matter with maintenance and informed me the MEL was appropriate according to aircraft maintenance. After several minutes passed; a local gateway maintenance supervisor responded and promptly had the interphone amplifier removed and replaced. This resolved our problem. Our issue was the result of no cockpit interphone capability. This issue was not to be confused with no cockpit-to-ground and ground-to-cockpit interphone capability (per the stated MEL). We were unable to satisfy company aircraft operating procedures (test interphone operation of oxygen mask); company and aircraft flight manual emergency procedures (smoke/fumes- oxygen masks on; crew communications established). Ultimately; per far part 121 regulations; we believed we could not operate this flight safely. The flight crew recommends the MEL be edited to address loss of intra-cockpit interphone capability.

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Original NASA ASRS Text

Title: Captain reported that an MEL was applied to an aircraft in error; resulting in the loss of cockpit oxygen mask interphone capability.

Narrative: During review of flight release; preflight duties we discovered the aircraft had a minimum equipment item that deferred the flight-deck-to-ground; service interphone system. We reviewed the MEL and noted that we would have to use hand signals and prior coordination with ground support personnel during engine start and taxi. This flight was scheduled as a quick-turn and Maintenance did not plan on any repair of the interphone system.During cockpit preflight duties; the First Officer discovered the cockpit oxygen mask interphone system was inoperative. We tested both the cockpit speaker system and headphone system at both seats and discovered all systems were inoperative. We checked the service interphone system and it was also inoperative. I immediately called the company dispatcher and advised him of our situation. He called me back several minutes later and stated that Maintenance advised him the MEL was appropriate for our situation and it was airworthy at that point. I disagreed with their assessment. The First Officer and I agreed the MEL was not germane to our problem. The Dispatcher then suggested we solicit the help of a company SME (Subject Matter Expert). I agreed and was called later by the SME. When the SME called I discussed my situation; he then discussed the matter with Maintenance and informed me the MEL was appropriate according to aircraft Maintenance. After several minutes passed; a local gateway Maintenance Supervisor responded and promptly had the interphone amplifier removed and replaced. This resolved our problem. Our issue was the result of no cockpit interphone capability. This issue was not to be confused with no cockpit-to-ground and ground-to-cockpit interphone capability (per the stated MEL). We were unable to satisfy company aircraft operating procedures (test interphone operation of oxygen mask); company and aircraft flight manual emergency procedures (smoke/fumes- oxygen masks on; crew communications established). Ultimately; per FAR part 121 regulations; we believed we could not operate this flight safely. The flight crew recommends the MEL be edited to address loss of intra-cockpit interphone capability.

Data retrieved from NASA's ASRS site 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.