Maintenance technician reported discovering the transfer gearbox shroud for a CFM56 engine could be ...

Narrative:

While assembling a ge C2 transfer gearbox; I noticed a possible discrepancy in the way the shroud was installed on adapter of horizontal gearshaft. The manual has a note that reads: with adapter aligned as it fits on the transfer gearbox; the housing shroud must be installed at the 6 o'clock position. My concern is I may have installed the shroud incorrectly on possible 5 gear boxes in the past several months while performing maintenance under check and repair guidelines. If they were installed incorrectly it would not be evident because a gear backlash check is not required which would alert the mechanic to the problem. We do perform a pressure test. The pressure test would not alert mechanic to shroud being installed incorrectly. It is possible to install it in the 12 o'clock position and not know it on a check and repair the gearbox. In question are only check and repair gearboxes.the 6 o'clock position is only identified in the inspection/check figure. Even there it is not clear. Add to note in subtask that reads along with current note: the flat on adapter housing is 6 o'clock position. Also add line to logbook to verify shroud in 6 o'clock position. Add this note after current line 7 which calls to install horizontal adapter gearshaft package in gearbox housing.

Original NASA ASRS Text

Title: Maintenance Technician reported discovering the transfer gearbox shroud for a CFM56 engine could be installed upside down and may have occurred on previous gearbox assemblies.

Narrative: While assembling a GE C2 transfer gearbox; I noticed a possible discrepancy in the way the shroud was installed on adapter of horizontal gearshaft. The manual has a note that reads: With adapter aligned as it fits on the transfer gearbox; the housing shroud must be installed at the 6 o'clock position. My concern is I may have installed the shroud incorrectly on possible 5 gear boxes in the past several months while performing maintenance under check and repair guidelines. If they were installed incorrectly it would not be evident because a gear backlash check is not required which would alert the mechanic to the problem. We do perform a pressure test. The pressure test would not alert mechanic to shroud being installed incorrectly. It is possible to install it in the 12 o'clock position and not know it on a check and repair the gearbox. In question are only check and repair gearboxes.The 6 o'clock position is only identified in the inspection/check figure. Even there it is not clear. Add to note in subtask that reads along with current note: The flat on adapter housing is 6 o'clock position. Also add line to logbook to verify shroud in 6 o'clock position. Add this note after current line 7 which calls to install horizontal adapter gearshaft package in gearbox housing.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1482118
Time
Date	201704
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Parked
Component
Aircraft Component	Accessory Drive Section
Person 1
Function	Technician
Qualification	Maintenance Airframe Maintenance Powerplant
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy

Maintenance technician reported discovering the transfer gearbox shroud for a CFM56 engine could be installed upside down and may have occurred on previous gearbox assemblies.