On may-30-84 at Chalkhill, PA a  Lockheed l-188 a scheduled 14 cfr 121 Operation of Zantop Int'l Airlines, inc crashes and kills 4. After departing the Baltimore Washington Arpt, the acft had climbed to fl 220. According to info on the cockpit voice recorder (vcr), the crew experienced gyro problems during the climb. They selected the #1 vertical gyro to drive both approach horizons (attitude indicators), since there was an indication of a malfunction in the #2 vertical gyro sys. About 7 min after leveling at fl 220, the flt was cleared to the dryer vor. Shortly after that, there were indications of confusion in the cockpit which included the statements, "what's happening here," "you got it?" & "no." The acft entered a right descending spiral; the indicated airspeed increased from aprx 205 to 317 kts; then an in-flt breakup occurred. The wreckage was found scattered over an area aprx 2 mi long by 1 mi wide. An exam of the wreckage revealed that the in-flt structural failure had occurred due to overload, then a fire ignited in the right wing after it had failed. The acft was not equipped with an independent standby  attitude indicator.