since 1940

Aluminum metal in aircraft oil sample

Small aluminum slivers found in oil filter of Lycoming O-320 H2AD engine.

Aluminum can be identified by immersing a sample in a diluted sodium hydroxide. Aluminum fizzes and dissolves. Sodium Hydroxide is sold at the supermarket under the trade name "Drano" or "Red Devil". Red Devil is preferred since it is 100% sodium hydroxide.

1. Lycoming aircraft engines - Piston pin plug would be typical source of aluminum in the aircraft oil sample.

2. Continental aircraft engine IO520 AE only (only AE) aluminum starter adapter gear.

3. Continental aircraft engine piston pin plugs in Ceramic chrome cylinders.

4. Aluminum granules - piston or cylinder head burning from preignition.

5. Chunks - possibly piston ring land or piston skirt.,

6. All engines - exhaust guide loose in cylinder.

7. Lycoming 540 series inspect the left magneto adapter bearing for failure.

8. Lycoming crankshaft idler gear (P/N LW-13796) shaft and the attaching hardware loose allowing the shaft to rotate, wiggle, and elongate the engine crankshaft hole. 

Any metal found  in an aircraft oil sample doesn't belong there. Ground the aircraft until you determine where and why the metal is present. Only then can you determine the airworthiness of the aircraft.

 

Source of metal slivers found in oil filter pictured above is the  Lycoming piston pin plug. All should look like the one on the left.

 

Exhaust guide boss with guide missing One source of aluminum is the guide working in the guide boss. This often produces large quantities of very small aluminum pieces. If the valve sticks it can pull the guide so that the valve and guide are moving up and down as a unit.

Connecting Rod Bearing Aluminum particles embedded in connecting rod bearing.   The connecting rod bearings act as a fine filter that filters out any debris in the oil and embeds them into the bearing.  Whenever metal bits have circulated in the oil and embedded into the bearings you have two concerns: steel bits that embed into the bearing will score the crankshaft. Next time you overhaul the engine the crankshaft is ruined. Large amounts of metals, such as aluminum embedding into the bearings reduces the running clearance between the bearing and the journal possible resulting in oil film failure and bearing destruction. Whenever metal has passed the oil filter (sometimes you can determine this by checking the propeller governor screen gasket) you need to access it's affect on the bearings. Engine disassembly and replacing the bearings is a good idea.

Copyright 2003 by Sacramento Sky Ranch Inc. All rights reserved.  Prices subject to change without notice. Not responsible for typographical or misprint.
Disclaimer: sacskyranch.com contains abundant information relating to aircraft maintenance. The information provided  is not intended to supercede or supplement the F.A.A. approved  maintenance and/or operator’s manuals. Those F.A.A. approved manuals must be utilized when performing maintenance and/or operating aircraft.