Jet/Long Ranger/206
Maintenance Airframe; Maintenance Powerplant
Maintenance Lead Technician 5; Maintenance Technician 38
Communication Breakdown; Situational Awareness
Aircraft Equipment Problem Critical
General Maintenance Action
Human Factors; Manuals; Procedure; Chart Or Publication
Aircraft was on a public relations [demonstration] assignment. Pilot reported slight transmission oil seepage on the transmission deck. Aircraft departed the event; arrived at home base. On inspection; I found that the Magnetic Chip Plug was sheered off at its base. The internal check valve was still in place; preventing further transmission oil seepage. The part that sheered is installed at overhaul with a low torque of 75'- 125' inch-pounds and is not removed at any inspection. It appears to me that it was installed without a torque wrench. It requires a 3/4' socket to install. I had to use an adapter to get my 1/4' inch torque wrench on this socket. This torque is in the Bell Maintenance Overhaul Manuals. But it needs to be highlighted for emphasis because it is such low torque.
Reporter stated he is a Field Mechanic and has found two other helicopters with their Magnetic Chip Detector plug housing sheared-off flush with the Main Gearbox (MGB) transmission housing. The Chip Detector housing is threaded into the MGB; that's why the detector did not fall out. He found the sheared-off part still hanging from the lanyard that was attached to the MGB. Reporter stated their Rolls Royce (R/R) Overhaul and Line Maintenance Manuals (M/M) are all electronic. The Engine Manufacturer (MFG) had revised the reduced torque requirements in their R/R Overhaul Shop Manuals for the Chip Detector plug on the R/R 206L-3; but had not done the same for their 206L-1 model engines. Currently; their Overhaul Shop has been using a letter from the MFG allowing mechanics to deviate from the R/R 206L-1 Overhaul Manual to apply reduced torque when installing the Chip Detector housing.
A Line Mechanic found a Magnetic Chip Detector plug housing sheared-off flush with the Main Gearbox (MGB) transmission housing on a Bell 206L-1 helicopter. He had previously found two other Bell 206L-1 MGBs with the same condition.