B777 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Total 10698; Flight Crew Type 1051
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural FAR
General Maintenance Action
Procedure; Aircraft
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.
[Report narrative contained no additional information.]
B777 flight crew reported a maintenance discrepancy concerning a function button on the Mode Control Panel which had an extinguished light bulb.