GEARBOX SYSTEMS

NAVAIR 17-15-50.3

TM 38-301-3

T.O. 33-1-37-3

CGTO 33-1-37-3

(MV-22) (CV-22)

GEARBOX SYSTEMS

The MV-22 and CV-22 gearbox systems are comprised of one mid-wing gearbox (MWGB), two prop-

rotor gearboxes (PRGB), two tilt-axis gearboxes and the emergency reservoir system (ELS). These

systems use a fine filtration system of 3 and 40 micron filters, with desiccate filters to remove moisture

from the air. Based on the filtration design, RCM analysis and recommendation from oil analysis experts in

NAVAIR 4.4, JOAP analysis has been determined to be an ineffective preventive maintenance task for the

drive system.

The current filtration consists of a manifold assembly, filter bowl assembly, primary filter element

assembly and secondary filter element assembly. The oil enters the filter assembly from the oil coolers at

an unregulated pressure of 93 to 170 PSIG. Pressure regulated and filtered oil is delivered through the

filter, which acts to remove air and debris scavenged from the PRGB cavities before returning to the

reservoir. This design effectively cleanses the V-22 drive system gearbox lubricants during normal

operations.

Should the drive system lubricants absorb moisture from high humidity atmospheric conditions, water

accumulation is evident when the desiccant filter has discolored and changed from the normal blue color.

Under these conditions only, oil samples shall be taken and analysed for water content. Water limits are

1000 PPM or 0.100 percent. If water content exceeds the allowed limits, (1) the drive system oil shall be

drained and the system re-serviced and (2) the desiccant filter must be changed. Refer to the applicable

V-22 IETMS for more details on these maintenance requirements.