BLUF: Grease discoloration in the Apache tail rotor gearbox and intermediate gearbox is not sufficient cause for replacing them.
Photo by Capt. Erick Turley
Mechanics, Aviation Maintenance Information Message (MIM) is making an update to the recently released TM 1-1520-Longbow/Apace (16 Mar 23). Several task steps in the TM required mechanics to replace the gearboxes in the table below if there was grease discoloration.
Table: Affected gear boxes
| Nomenclature |
NSN |
Part Number |
| Tail rotor gearbox |
1615-01-254-7793 |
7-311340001-7 |
| Tail rotor gearbox |
1615-01-507-5294 |
7-311340001-9 |
| Intermediate gearbox |
1680-01-530-1625 |
7-311330001-9 |
| Intermediate gearbox |
1680-01-478-7102 |
7-311330001-7 |
| Intermediate gearbox |
1680-01-232-0038 |
7-311330001-5 |
This guidance is no longer applicable. Analysis has revealed that grease discoloration is not a reliable indication of contamination (other indicators such as vibration and temperature are deemed more reliable). As a result, the requirement to replace gearboxes due to grease discoloration in TM 1-1520-LONGBOW/APACHE (16 Mar 23) is discontinued. The TM will be updated at the next change cycle.
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