Date: 201311
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Aircraft: Jet/Long Ranger/206
Operator: Air Taxi
Operating under: Part 135
Mission: Ambulance
Flight phase: Cruise
Aircraft component: Helicopter Gearbox Drive Shaft
Component problem: Malfunctioning
Reporter organization: Air Taxi
Reporter function: Inspector; Technician
Reporter qualification: Maintenance Inspection Authority; Maintenance Powerplant; Maintenance Airframe
Human factors: Time Pressure; Workload; Distraction; Fatigue; Communication Breakdown
Second reporter function: Technician
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed As Precaution; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Chart Or Publication; Company Policy; Aircraft; Human Factors; Procedure; Manuals
Primary problem: Human Factors

Narrative: The Bell 206L aircraft had been in an FAR 135-Heavy Maintenance facility where it had the transmission replaced. It was released as airworthy and after approximately 50-hours flight time; the flight crew heard an unusual noise and the pilot made a precautionary landing.The Base Mechanic was dispatched to the aircraft where he performed a visual inspection and couldn't find any obvious source of the noise. The pilot and Mechanic flew the aircraft back to base; the noise was not present for the flight back. While the Mechanic was investigating a transmission oil leak back at the [Maintenance] Base; he discovered the bolts attaching the Main Drive Shaft to the transmission were loose.I believe a contributing factor was failure by the installing Mechanic to complete the installation of the fasteners [bolts] before moving to a different step of the job. I believe human factors involved in this incident are fatigue; complacency; and the pressure by Management to maintain a high tempo of production at their Heavy Maintenance facilities.The company's 135-Heavy Maintenance was restructured just over a year ago. The 135-Heavy Maintenance of approximately 118 aircraft had been divided between X number of Heavy Maintenance bases; but now down to four. The scope of work now is more what you would expect at a 145-repair facility; which the company has; but the [remaining] 145-repair facilities can't keep up with company needs. Work at this facility is being performed 14-hours a day using split shifts; and 365 days a year using two crews of four mechanics; each crew working seven days 'on'; seven days 'off' hitches. At this facility; there are only seven mechanics instead of the full crew of eight. Out of the seven mechanics; four are housed in living quarters in the hangar during their hitch. This facility is also used for 'after' hours parts support for 25 of the company's field bases. This facility is located on a regional airport approximately 100 yards from the runway and with a four lane highway approximately 30 yards on the other side and directly on a tarmac for a flight school and business jets. So it is difficult to get proper rest. This along with the increased work load and high production tempo leads to a chronic; low to mid level of constant fatigue.I think a corrective action might be to put in place a Quality Assurance (Q/A) Department whose sole job is to 'Buy Off' on Flight Safety Critical maintenance procedures before the maintenance can even proceed. And also move the living quarters offsite. The current procedure in place is the mechanic performing an install; prints out the install procedures from the Maintenance Manual (M/M) and initials each step. If he has to stop the job for any reason he puts a red mark after the last step he completes. The mechanic that resumes the job whether it is another mechanic or himself has to go back and verify [that] the three steps before the red line have been completed; before he can proceed. The Maintenance Records do not require the initials or signature of another mechanic on a Flight Safety Critical step of a job before proceeding. The suggested practice is to get someone else to look the job over; but is not required to be documented in any way.I was not the installing mechanic; but I initialed one block of an Approved Aircraft Inspection Program (AAIP) Checklist for the Main Drive Shaft area. Since the inspection form block doesn't require a date; I cannot prove I performed a visual inspection of the drive shaft before it was known the aircraft needed the transmission replaced; so I am self disclosing.

Callback: Reporter stated he had previously worked for an airline; but the company he works for now does not actually have an Inspection Department similar to what FAR 121 Operators have. Although they have procedures for Safety Critical components; those procedures do not work. The attaching bolts for the Main Drive Shaft from the Engine Gearbox to the Transmission were found loose where the shaft connects to the transmission; the transmission then drives the Main Rotor Assembly. Currently; the lack of an Inspection Department that actually acts as 'Second Set of Eyes' and has a block to sign-off for the inspection; including an entry date for when the work was accomplished would help. No training is provided to mechanics acting as a 'Second Set of Eyes'. The helicopter with the loose drive shaft bolts had two preflight checks each day by pilots with daily flight checks by Maintenance and still the loose bolts were missed. Since the discovery of the loose bolts; more paperwork has been put in place for mechanics to sign-off; but no real Inspection Department has been created.Reporter stated they work 12-hour shifts; seven days straight. They live and sleep in a small room with bunk beds with fuel fumes. Due to the distance from home that many mechanics drive from and the time to commute on a daily basis to the Maintenance Base; most mechanics elect to just stay on-site. They have two pilots; each doing 12-hour shifts; but their living quarters are off-site. A better facility and more rest would go a long way to improving maintenance.

Second narrative: It has come to my attention that a Bell 206L helicopter; Aircraft X; had reported a loss of torque on hardware pertaining to the K-Flex Main Drive Shaft. I was a participating mechanic on a large scope of work on this aircraft; but to the best of my recollection was not involved in the removal and installation of the Transmission Drive Shaft. I believe Maintenance Procedure Cards with Quality Assurance (Q/A) signature blocks would be better suited for the type and scale of maintenance being performed.


Synopsis: Four Aircraft Maintenance Technician (AMT) reports about working conditions at an FAR 135 repair facility that included fatigue; complacency; the lack of an Inspection Department and the lack of adequate maintenance procedures that eventually led to one of their pilot's performing a precautionary landing of a Bell 206L helicopter.