Apache: Color of Grease Not Cause for Gearbox Replacement

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This guidance is no longer applicable.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.
 
To view the MIM, click HERE. Click on Consolidated Listings, select Aviation as the Record Type, H-64 as System Type and MIM as Message Type. Then click Search. Results are listed in chronological order.