Eurocopter AS 350/355/EC130 - Astar/Twinstar/Ecureuil
Maintenance Inspection Authority
Maintenance Inspector 17; Maintenance Technician 25
Fatigue; Distraction; Communication Breakdown; Situational Awareness; Workload
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Human Factors; Staffing
After completion of a 600-Hour Airframe and Engine Inspection that had the engine removed for a turbine wheel change; the Track and Balance was completed with all test flights accomplished. The aircraft received a Turn-Around Inspection which revealed a shredded piece of a washer on the forward transition deck. While removing components to look for any missing parts; it was discovered [that] the aft section of the short shaft had three bolts holding the forward side of the flex-coupling [that] were not safetied. Further investigation revealed that the bolts/nuts were not torqued. The engine change was signed-off by an Airframe and Powerplant (A/P) Mechanic; an Inspection Authority (IA) and I did the Quality Control (QC) Final. I am in charge of the QC Department and did not personally witness the work performed; but I am ultimately responsible for safety and did not perform my job in ensuring the safety of my men and my flight crews.
Reporter stated their Turn-Around (T/A) Checks are accomplished between flights compared to the First flight of the day pre-flight and after the last flight of the day post flight checks. Part of the Turn-Around Check procedures are to look for external/internal damage; loose equipment; worn rubber and also includes opening the engine cowling compartment; which is the area where the shredded washer was found by one of their mechanics. Everyone was trying to figure out where the washer came from and what could have caused the shredding. He used his inspection mirror and flashlight and looked further inside the cowling area and that was when he noticed the short shaft and flex-coupling bolts and nuts were not properly secured. The short shaft is between the main rotor transmission and engine; encased in a big; thick aluminum housing with only one opening near the air conditioning unit. Seeing the unsecured flex-coupling; he grounded the AS350-B3 Eurocopter because they were not sure what other components may not be secure.Reporter stated there were contributing factors that led to the unsecured short shaft incident involved their maintenance operation. They are a Contract Maintenance Provider; operating under Part 91; under contract to the Department of Defense (DOD) for maintaining law enforcement helicopters. They are not a large operation and everyone knows each other. They have many fixed wing and rotorcraft they work on and one of the human factors they now realize was a contributor; was how often mechanics and inspectors were pulled away from one job to take care of an immediate situation on another aircraft. That's exactly what happened in the short shaft situation. Mechanic told the IA Inspector; who were friends; that he was going to torque the short shaft and flex-coupling bolts to be observed by the Inspector; than safetied with cotter pins and torque sealed with a color coded Inspector's putty that is specific to each Inspector. However; both were pulled away to address other aircraft and neither one followed-up on completing the short shaft and flex-coupling bolt connections. But they did sign-off the Job Card for the engine change.Reporter stated he and their entire crew are devastated about the event; especially since they all understand the mechanics of the Eurocopter and how close they had come to losing that helicopter and the flight crew. If the short shaft had separated from the flex-coupling; the main rotor transmission would be disconnected from the engine section and the Eurocopter would go into autorotation mode. If the flight crew had enough altitude; the Eurocopter and flight crew had a higher survival rate in auto-rotation. But if altitude was low; such as during hovering and the short shaft disconnected; the fatality rate was very high.
A Quality Control Supervisor describes how a shredded washer; found during a Turn-Around Check by a Mechanic on a Eurocopter AS350-B3 helicopter; led to the discovery of three untorqued and unsecured bolts that connect the short shaft and flex-coupling between the main rotor transmission and engine. Maintenance practices at their Contract Maintenance facility were also noted.