What was found
PIT - FL 1595 - ON CLIMB-OUT, THE FLT EXPERIENCED AN UNCOMMANDED ROLL TO THE LT. FLT WAS CLEARED TO 6,000 FT AND ENCOUNTERED A BUFFET AT ABOUT 4,500 FT, WHILE CLIMBING STRAIGHT AHEAD AT 230 KTS INDICATED. A/C BEGAN ROLLING SLOWLY LT WITH A CHANNEL AUTOPILOT ENGAGED. A SHUDDER WAS FELT AS A/C CONTINUED TO ROLL TO A 30 DEGREE BANK. CREW DISENGAGED AUTOPILOT AND YAW DAMPER. FULL AILERON AND PARTIAL RUDDER INPUT WAS REQUIRED TO STRAIGHTEN AND LEVEL A/C. FLT RETURNED TO FIELD, WITH NO FURTHER INCIDENT. MX ACCOMP T/S OF AUTOPILOT NR 1 AND NR 2 PER DIRECTION OF USAIR AVIONICS ENGINEERING. REPLACED FLT DATA RECORDER FOR READOUT WHICH INDICATED ROLL WAS CAUSED BY WAKE TURBULENCE. FDR OPS CHK GOOD. (M)