DCA84IA001

A Boeing VC-137B-BN, USAF #58-6971, operating as air force 2 (AF-2), departed cleveland, OH, at about 1745 EDT on an IFR clearance. After departing cleveland, AF-2 was assigned an alt of 8000 ft MSL by cleveland departure control & was transfered to cleveland ARTCC. On initial contact with cleveland ARTCC, AF-2 was cleared to climb to flt level 230. A Cessna 310J, N3057L, was cruising in the same vicinity on an IFR clearance at 13,000 ft & was also under control of cleveland ARTCC. As AF-2 was climbing thru 12,200 artcc's ATC computer conflict alert function was activated for both acft, alerting the controller of a pending loss of required separation. The controller instructed AF-2 to maintain 12,000 ft. AF-2 acknowledged. However, AF-2 reached aprx 13,000 ft before starting descent & sepn contddecreasing. Rdar data showed a min slant range dist of 1/4 mi WITH600 ft vrt sepn. This constituted and ATC operational error involving less than standard sepn. The acft were in IMC & none of the plts saw the conflicting traffic

A Boeing VC-137B-BW, USAF #58-6971, operating as air force 2 (AF-2), departed cleveland, OH, at about 1745 EDT on an IFR clearance. After departing cleveland, AF-2 was assigned an alt of 8000 ft MSL by cleveland departure control & was transfered to cleveland ARTCC. On initial contact with cleveland ARTCC, AF-2 was cleared to climb to flt level 230. A Cessna 310J, N3057L, was cruising in the same vicinity on an IFR clearance at 13,000 ft & was also under control of cleveland ARTCC. As AF-2 was climbing thru 12,200, artcc's ATC computer conflict alert function was activated for both acft, alerting the controller of a pending loss of required separation. The controller instructed AF-2 to maintain 12,000 ft. AF-2 acknowledged. However, AF-2 reached aprx 13,000 ft before starting descent & sepn contddecreasing. Radar data showed a min slant range dist of 1/4 mi with 600 ft vert sepn. This constituted an ATC operational error involving less than standard sepn. The acft were in IMC & none of the plts saw the conflicting traffic