B737-700 Flight Crew reports accepting an aircraft with MEL's to deal with a spurious 'Minimums Minimums' automated callout. On the first landing the callouts occur. Maintenance Control is unsure if the MEL actions were meant to silence the callouts or even if they are anomalous or just part of a software upgrade in newer aircraft.
Synopsis
B737-700 Flight Crew reports accepting an aircraft with MEL's to deal with a spurious 'Minimums Minimums' automated callout. On the first landing the callouts occur. Maintenance Control is unsure if the MEL actions were meant to silence the callouts or even if they are anomalous or just part of a software upgrade in newer aircraft.
Narrative
We received an aircraft at the start of our trip with three MEL's. The MEL's were: 34-20 No 2 Radio Altimeter; 34-12 No 2 Flight Director; and 32-27 PSEU System. The original logbook discrepancy was for a spurious 'Minimums/Minimums' automated callout. The ME'Ls resulted in higher weather minimums for the aircraft. (The A/C was downgraded to CAT I only; no lower than 4000 feet or 3/4 mile visibility.) We flew the aircraft and at touchdown; the 'Minimums/Minimums' callout occurred. After arriving at the gate; the First Officer and I discussed the existing MEL's and felt that we were okay to continue. We thought the intent of the MEL's were to prevent us from being distracted by the spurious callout in a low weather; low altitude situation by setting higher approach minimums. We continued on to our next destination. On the next flight; the First Officer and I further discussed the MEL's. We realized that we didn't know if the deferrals were actually intended to prevent any further callouts form occurring. If that was the intent of Maintenance Control with the MEL's; further maintenance and or deferrals were needed. Upon arrival at our next destination; the callout occurred again. I contacted Maintenance Control and talked with the Contract Mechanic. With the version of software on this new aircraft; the answer was unclear. The Contract Mechanic thought the callout was normal. The Maintenance Controller decided the GPWS system needed to be deactivated to silence the automated callouts. At this point it was still unclear whether we violated any FARs. After doing more research with Maintenance Control; they told me that this automated callout would be standard on all aircraft {tail number} onward. Determine if these automated callouts should or should not occur. Either de-activate them or publish guidance for Flight Crews to use if the callout will be standard on our new aircraft.
Second reporter narrative
Upon arrival; the callout occurred again. We contacted Maintenance Control and also talked with the Contract Maintenance Mechanic. It seemed that there was no general agreement among them as to whether this automated callout was normal. The Mechanic said he thought it was; but Maintenance Control said it wasn't. In the end; it was decided that the GPWS system should also be deactivated and deferred to definitely silence these automated callouts. This was done.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.