POTENTIAL SOURCES OF WEAR METAL 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-100 (Cont)

AIRCRAFT:

(B-2)

1. Historically, high or abnormal wear metal levels have been tracked to engine accessory item failures. Main

engine bearing failures on the F-118 engine are typically caused by spalling which is detected by the quantitative

debris monitor QDM. Bearing failures may occur without any indication reflected in the JOAP analysis. QDM

inspection and JOAP analysis results may be used together to increase the accuracy of the evaluation process for

the F-118 engine.

2. QDM shall be inspected when increases in JOAP wear metal concentrations cause concern or when the OAP

lab requests a special red cap sample. Debris on the QDM may indicate part distress.

POTENTIAL SOURCES OF WEAR METAL TO AID TROUBLESHOOTING

1. Main Bearings or Gearboxes:

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

may accompany the Fe.

A moderate increasing trend of Fe may indicate excessive wear of gears and gear shafts splines.

c. For a confirmed significant titanium Ti readings, 8-9 PPM for emission rotrode, the numbers 1 and 2, and

possibly number 3 bearing inner races may be turning on the inner race journals.

NOTE

If a significant rise in Fe accompanies Ti, this may indicate a loose number 3 locknut.

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

journals.

An abnormal rise in Fe may be accompanied by rises in Ti or Ni.

2. Accessory Items:

a. Lube and scavenge pump distress may be indicated by increasing trends in Fe and copper Cu together.

Al may accompany the Fe and Cu.

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

increase in Fe.

4. Miscellaneous:

a. High silicon Si indicates oil contamination, possibly from the oil servicing cart. The oil servicing cart and

engine shall be checked from contamination and, if contaminatoin is confirmed, both oil servicing cart and engine

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

servicing cart, if applicable shall, be analyzed by the OAP laboratory personnel to ensure all Si contamination has

been removed.

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

tube forming process.

A92