Air carrier Maintenance personnel expressed concern that the US-3530 crack-detection equipment in use is not sufficiently accurate.

Narrative

This issue is associated with AD 2010-01-05 & AD 2008-03-09. At XA:48; I received an alert for Aircraft X indicating a deferral update had been entered. This was a follow up for reduced inspection interval of engine turbine rear frame cracks discovered by ZZZ1 on Day 0.During my review I discovered that ZZZ Quality Assurance (QA) had accomplished the eddy current inspection on the #2 engine IAW in accordance with the job card. The updated indicated no defects found." I questioned this entry since the cracks had previously been documented by ZZZ1 initially on Day 0 and again during an inspection on Day 55.I notified the ZZZ hangar and Maintenance Control; Person A; of the situation and applied a Maintenance Control lock in the web-based system to prevent the aircraft from returning to service until further research could be accomplished. I explained my concern about cracks being previously reported that were near allowed limits that were now being reported as not found. I also found an inspection accomplishment by ZZZ on Day 87 that also indicated no findings.I later was advised by inspector Person B (not the inspector that accomplished the inspection) that the probe US-3530 used in ZZZ; though approved by manual; is not as sensitive as the APN-92-10FX1/3M probe used by ZZZ1. He also stated that ZZZ is not allocated the APN-92 probe. It was determined by other management personnel that since ZZZ had accomplished the inspection in accordance with the appropriate job card the inspection results were considered acceptable. The aircraft was returned to service and scheduled for revenue flight.Cause: The equipment being used in ZZZ though approved; is not sensitive enough for consistent results of this AD required inspection. The preferred probe as called out in the job card "equipment" section is not being used consistently at stations assigned to accomplish the inspection.Suggestions: Revise the job card to only allow specific probes and assure the required probes are available at each station that accomplishes this task. Require specific findings i.e. current or propagated dimensions of any damage during follow up inspections be included on any update. Not just use statements such as "recheck accomplished;" "inspected and found to be in limits;" etc."