SA-227 AC Metro III
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 90; Flight Crew Total 3700; Flight Crew Type 250
Situational Awareness; Confusion; Communication Breakdown
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Taxiway
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Airport; Chart Or Publication
I was parked at the FBO; off Taxiway L2. I was given taxi instructions 'Taxi to 24L via L2; L; W; hold short of 24L.'  I looked at my NACO airport diagram and misread it. On the bottom of the chart; there is a longitude marking of 81.52W. The 'W' made it appear that Taxiway 'T' was Taxiway 'W'.Instead of making a right turn on Taxiway L; I made a left turn on Taxiway L and was proceeding to what I thought was Taxiway W. Ground asked me if I was heading southwest; and I confirmed that I was. I was then told to turn around on Pad 5 and taxi as previously instructed. There was no threat of an aircraft collision.I believe that having this longitude marking makes it easy to mistake Taxiway 'T' for Taxiway 'W' and should be relocated to another point on the chart. It is the same size and font as the rest of the taxiway labels.
An SA-227 pilot mistook the 'W' in a NACO airport chart longitude marking (81.52W) as a taxiway designator at CLE and taxied southwest bound toward 6R after being cleared to runway 24L via Lima 2; Lima and Whiskey. The actual W taxiway is at the departure end of 24L.