B777 flight crew reported a maintenance discrepancy concerning a function button on the mode control...

Narrative:

During the review process of the [maintenance release]; I noted a deferred defect 'flch button light inop.' the MEL stated; 'affected mode indications on both pfd's must operate normally.'I asked local maintenance if they changed the light bulbs. They said no. [I] asked why not; I was told they were concerned if they broke the switch in the process; the flight would cancel; because they lacked the parts to fix this. It was not possible to dispatch with the switch inoperative.just minutes before pushback we received an ACARS message that our [maintenance release] was invalid. A new [maintenance release] was received from [maintenance control]. The updated [maintenance release] changed the defect to 'mode control panel flch switch inoperative.' the MEL stated; 'may be inoperative provided enroute operations do not require its use.' what does this mean? This is a very vague statement. We use flch on every flight. Local maintenance had previously informed me this was not deferrable. I satcom called dispatch and [maintenance control] to discuss this item.both dispatch and [maintenance control] told me that the deferral was legal with no restrictions. With this information and the excellent weather forecast for the flight; I accepted the [maintenance release] even though I was still annoyed; unclear; of the MEL statement.during cruise I reviewed the FM (flight manual); fom (flight operations manual); [international operations manual] and discussed this more with both first officer's. The cabin altitude checklist; used for emergency descent; specifically states flch. However there is V/south (vertical speed) guidance buried in the FM for emergency descents. Obviously flch is preferred due [to] airspeed and altitude protection.I sent an ACARS message to the [chief pilot] asking what the MEL note mean to him. With no answer I satcom called dispatch with a phone patch including the [chief pilot]. I discussed my concerns and requested more information from the B777 fleet at the training center.

Original NASA ASRS Text

Title: B777 flight crew reported a maintenance discrepancy concerning a function button on the Mode Control Panel which had an extinguished light bulb.

Narrative: During the review process of the [Maintenance Release]; I noted a deferred defect 'FLCH button light inop.' The MEL stated; 'Affected mode indications on both PFD's must operate normally.'I asked Local Maintenance if they changed the light bulbs. They said no. [I] asked why not; I was told they were concerned if they broke the switch in the process; the flight would cancel; because they lacked the parts to fix this. It was not possible to Dispatch with the switch inoperative.Just minutes before pushback we received an ACARS message that our [Maintenance Release] was invalid. A new [Maintenance Release] was received from [Maintenance Control]. The updated [Maintenance Release] changed the defect to 'Mode Control Panel FLCH switch inoperative.' The MEL stated; 'May be inoperative provided enroute operations do not require its use.' What does this mean? This is a very vague statement. We use FLCH on every flight. Local Maintenance had previously informed me this was not deferrable. I SATCOM called Dispatch and [Maintenance Control] to discuss this item.Both Dispatch and [Maintenance Control] told me that the deferral was legal with NO restrictions. With this information and the excellent weather forecast for the flight; I accepted the [Maintenance Release] even though I was still annoyed; unclear; of the MEL statement.During cruise I reviewed the FM (Flight Manual); FOM (Flight Operations Manual); [International Operations Manual] and discussed this more with both FO's. The Cabin Altitude checklist; used for emergency descent; specifically states FLCH. However there is V/S (Vertical Speed) guidance buried in the FM for emergency descents. Obviously FLCH is preferred due [to] Airspeed and Altitude protection.I sent an ACARS message to the [Chief Pilot] asking what the MEL note mean to him. With no answer I SATCOM called Dispatch with a phone patch including the [Chief Pilot]. I discussed my concerns and requested more information from the B777 Fleet at the Training Center.

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.

Attributes
ACN	1570802
Time
Date	201808
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	B777 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Parked
Flight Plan	IFR
Component
Aircraft Component	Autoflight System
Person 1
Function	Pilot Not Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine Flight Crew Instrument
Experience	Flight Crew Total 10698 Flight Crew Type 1051
Person 2
Function	First Officer Pilot Flying
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Experience	Flight Crew Total 11553 Flight Crew Type 377
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Maintenance Deviation - Procedural MEL Deviation - Procedural FAR

B777 flight crew reported a maintenance discrepancy concerning a function button on the mode control panel which had an extinguished light bulb.