Date: 201506
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: Jet Ranger All Series Undifferentiated or Other Model
Operator: Air Taxi
Operating under: Part 135
Flight phase: Parked
Aircraft component: Powerplant Fuel Control Unit
Component problem: Malfunctioning
Reporter organization: Air Taxi
Reporter function: Technician
Reporter qualification: Maintenance Airframe; Maintenance Inspection Authority; Maintenance Powerplant
Human factors: Communication Breakdown; Confusion; Situational Awareness
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: General Maintenance Action
Contributing factors: Aircraft; Human Factors; Logbook Entry
Primary problem: Aircraft

Narrative: June 2015; late afternoon; the pilot called me (approximately 80 miles from base) and advised he had a 'FADEC Degraded' light illuminate in-flight. I asked him to power up the aircraft and tell me if there was still a FADEC light. He said there was. I then asked him to move the throttle to idle. He did and told me that the FADEC light went out. Knowing what I know of the FADEC system; I knew that this indicated there were no current faults in the system. I then asked him to do a ground run and call me back when he was done. He called me back and advised that the run-up was fine and that there were no FADEC lights. I asked him to power up the aircraft one more time to double-check that there were no more FADEC lights. He did this and there were no lights. At this point I was not sure what I could do to the aircraft so I advised him to fly it home. This has been an ongoing intermittent problem since May 2015. We have replaced nearly every component in the whole system. An Avionics Technician spent a couple days going through wiring and was unable to find anything wrong. After speaking with my supervisor; (actually a Maintenance Manager); over the incident; he informed me I should have not allowed the aircraft to fly since I had not visually inspected it in accordance with a maintenance manual. He is probably right; I wasn't sure what to look at that I hadn't already. This has been a repeating problem that has been unable to be duplicated in the hangar. The FADEC Manufacturer Technician Representative has been contacted many times & we have followed all his advice. The aircraft would usually be in service for up to 10 days and fly 6 or 7 hours without any trouble. In my opinion; this intermittent problem has moved way beyond the scope of a Field Base Mechanic & the aircraft should have been flown to a Service Center where major disassembly or re-wiring can occur.The bottom line is that I probably should have driven up to the aircraft; looked at it; and made the proper logbook entries (even if the discrepancy could not be duplicated) before I allowed the pilot to fly it home.

Callback: Reporter stated the 'FADEC Degraded' light means the FADEC System was still controlling the Rolls Royce-250 Engine; but had lost some of its functionality. The problem with trying to troubleshoot and isolate the cause for the light illuminating was; the fault only occurs every ten to twelve hours; and only in flight. The FADEC Manufacturer's Technical Representative continued to believe the intermittent fault was caused by a wire chafing somewhere.Reporter stated his company finally sent the helicopter to a Service Center and the FADEC Representative had a large wire bundle harness removed. A Technician laid the removed wire bundle down on a table; inspected each wire and found two wires that had chafed through a small area of wire insulation that had been contacting each other; but not consistently. The wire bundle was replaced and so far; no other faults have occurred.



Synopsis: An Aircraft Maintenance Technician (AMT) was informed by a company pilot that one of their Bell BHT-407 helicopters had a 'FADEC Degraded' light illuminate in flight. The intermittent fault would occur every ten to twelve hours and had been an on-going problem for months that could not be duplicated in the hangar.