A B767 Captain refused an aircraft with a failed EGPWS so both the GND PROX FLAP and GND PROX/CONFIG GEAR switches were in the OVRD position rendering EGPWS Modes 1-7 inoperative. The dispatched destination had mountainous terrain and thunderstorms forecast.

Narrative

Aircraft arrived with a logbook discrepancy involving the EGPWS. The cockpit control switches for the system were deselected in the OFF position but the control switches indicated 'OVRD' in the control switch annunciation (both GND PROX FLAP OVRD and GND PROX/CONFIG GEAR OVRD). The discrepancy could not be cleared and MEL 34-46-1 was applied. Forecast weather for the destination airport included rain showers and convective activity. Hazardous rising terrain is a factor to the south of the localizer course. The alternate airfield is designated as a 'Special' airport due to rapidly rising terrain on the departure corridor. Condition A of the MEL advises that all modes (1-7) are considered inoperative. Maintenance Control could not provide the flight crew with information about modes 1-4 which are not explained in the MEL. Procedural guidance for Condition A revealed that the following systems would be unavailable or degraded: weather radar; modes 1-7 and Terrain System (Terrain Clearance Floor; Terrain/Obstacle Awareness Alerting; and Display Functions). The 767 QRH has numerous abnormal/emergency procedures requiring the use of both the GND PROX FLAP OVRD and GND PROX/CONFIG GEAR OVRD switches. Under the provisions of the MEL; these controls could not be legally manipulated by the flight crew if necessary to silence nuisance warnings. Upon careful review of the terrain; weather; and operational guidance provided in the MEL; it was determined that the flight crew did not feel completely safe about the operation and exercised our authority as specified in the FOM. We informed Dispatch of our decision to not accept the aircraft in degraded conditions and also discussed the issue with the Chief Pilot. The flight was re-crewed with Supervisory Pilots and departed approximately 5 hours late. The aircraft arrived with insufficient time to adequately clean; service; and perform required maintenance. On-time departure focus prevented repair of the EGPWS discrepancy and resulted in the application of the MEL; rather than repair/replacement. Improve the Safety Culture- This was clearly a case of economics overriding safety. In my opinion; the flight crew should not be forced to make a decision based on safety that should have already been made by Dispatch. The process of questioning the Captain with: 'Are you refusing the aircraft' and subsequent interrogation by the Chief Pilot creates an atmosphere where safety is compromised.