Commercial Fixed Wing
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Distraction; Confusion; Troubleshooting; Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Ground Equipment Issue; No Specific Anomaly Occurred Unwanted Situation
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Airport; Human Factors
MYR Ground instructed us to taxi from the ramp to Runway 18 via Z; hold short Runway 18.  At the ramp exit; we were positioned exactly on Z but the taxiway signage indicated Taxiway A4.  I stopped the plane; set the brake and told Ground that I thought we were holding short Taxiway Z; but the ground sign said A4.  Ground reported that the taxiway diagrams have been changed Z; but the ground signage still says A4.  We proceeded as directed without further incident. The taxiway diagram does not match the ground signage.  The signs should change at the same time as the taxi diagram or a NOTAM should be issued describing the discrepancy.
Air carrier Captain reported the taxiway diagram at MYR airport does not match the ground signage.