A Lead Mechanic with Inspection Authority (IA) reports their Part 135 Helicopter Repair Station procedures had not been followed. An ELT battery was found past due by eight days and the MEL program was not followed for proper Return to Service of their Eurocopter AS355 that involved their Maintenance Director.

Narrative

Upon reviewing the maintenance records on one of our Part 135 helicopters; it was found the ELT battery was past due by eight days. I informed Operations of this overdue item. The Shop Supervisor directed the Line Service individual to change the battery on the ELT located in the left cargo area. A battery had been pre-ordered and was in the parts department. When the individual could not connect one of the antenna leads; he asked for my assistance. I found the battery pack was the wrong part number for that ELT. I informed Operations that the aircraft would be out of service until a replacement battery pack could be procured and placed a red tag on the pilot's cyclic control. The Maintenance Director called and asked me to complete the records for a return to service. As I was preparing the log entry; MEL entry and weight and balance change; I went out to get the Flight Manual from the aircraft late morning. The Red Tag had been removed and the cargo area was closed. The aircraft had been returned to service. Outcome: Repair station procedures had not been followed. The MEL program for that aircraft was not followed for a proper return to service.