Skywagon 185
Flight Crew Commercial; Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 53; Flight Crew Total 1665; Flight Crew Type 31
Other / Unknown; Training / Qualification
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Overcame Equipment Problem; Flight Crew Returned To Clearance
Aircraft; Human Factors
I was transiting the Bravo airspace and was assigned a specific heading by ATC.  I thought I was flying the assigned heading when ATC asked me for my heading.  I then noticed that I had failed to set the vacuum driven directional gyro using the magnetic compass.  I have flown primarily glass cockpit aircraft for the last 7 years but recently purchased a Cessna 185 which has traditional instruments; and requires that the DG be set manually before flight and periodically during flight.  After realizing the omission; I immediately turned to the appropriate heading and then set the DG using the magnetic compass.
Cessna 185 pilot reported a track heading deviation due to improperly operating the vacuum driven directional gyro.