POTENTIAL SOURCES OF WEAR METALS TO AID TROUBLESHOOTING

NAVAIR 17-15-50.3

TM 38-301-3

T.O. 33-1-37-3

CGTO 33-1-37-3

ENGINE:

F118-GE-101 (Cont)

AIRCRAFT:

(U2S)

POTENTIAL SOURCES OF WEAR METALS TO AID TROUBLESHOOTING

1. Main bearings or gearshafts:

a. A sudden increase of Fe may indicate main bearing distress, small amounts of Ag and Ni may

accompany the Fe.

b. A moderate increasing trend of Fe may indicate excessive wear of gears and gearshaft splines.

c. For a confirmed significant Ti reading (8-9 ppm), the numbers 1 and 2, and possibly number 3 bearing

inner races may be turning on the inner race journals.

d. Increasing Cr may indicate the inner race may be spinning on the numbers 4 and 5 bearing journals.

e. An abnormal rise in Fe may indicate a loose No. 3 bearing locking nut; this may be accompanied by rises

in Ti or Ni.

2. Accessory items: Lube and scavenge pump distress may be indicated by increasing trends in Fe and Cu

together. Al may accompany the Fe and Cu.

3. Gearbox:

a. Increasing trends in Fe may indicate gearbox problems. Al and Ag wear metals may accompanying the

increase in Fe.

b. Chrome plating may be used for repair of gearbox bearing journals. Increasing Cr may indicate the

bearing race may be spinning on the journals.

4. Miscellaneous:

a. High Si indicates oil contamination, possibly from the oil servicing cart. The oil servicing cart shall be

checked for contamination and, if contamination is confirmed, shall be drained and flushed. The engine shall be

drained and flushed to remove Si contamination. Post maintenance samples from the engine and oil servicing

cart, if applicable, shall be analyzed by the OAP laboratory to assure all Si contamination has been removed.

b. Indications of Pb are not indicative of a need for further troubleshooting. Pb residue is a result of the tube

forming process.

c. Increases or abnormal levels of Zn or Mo, with no significant accompanying wear metals are not cause for

engine removal. However, when abnormal trends or levels occur for Zn or Mo, the oil cart shall be checked for

contamination.

d. A rise in Ag accompanied by a rise in Zn, Mg, or Cu can be an indication that the engine has been

contaminated with automotive oil (10W30, 10W40, etc.). Ag, Zn, Cu, and Mg should stabilize after the engine has

been drained and flushed. A Ag trend without Mg or Zn, or one which does not stabilize after the drain and flush is

an indication that an engine bearing is deteriorating. Zn levels may remain high after the 10 flight hours of local

operation. This is normal provided there is a general decreasing trend in Zn levels. Automotive oil contamination

will not cause significant damage to oil system components The oil servicing carts should also be inspected for

contamination. Carts found to be contaminated should also be drained and flushed.

A96