Joseph Kolly, Ph.D., Grease Group Chairman

1. Joseph Kolly, Ph.D., Grease Group Chairman Investigation of Lubricating Grease

2. Role of Lubrication in Accelerated Wear of the Acme Nut • Leading up to the time of the accident, Alaska Airlines used two brands of lubricating grease on its jackscrew assemblies: • Mobilgrease 28 • Aeroshell 33

3. Role of Lubrication in Accelerated Wear of the Acme Nut • Leading up to the time of the accident, • Alaska Airlines used two brands of lubricating grease on its jackscrew assemblies: • Mobilgrease 28 • Aeroshell 33 • Long history of satisfactory performance using Mobilgrease 28.

4. Flight 261 Grease Sample Analysis 1 mm Highly degraded grease sample from accident airplane’s jackscrew. Fresh grease shown for comparison.

5. Flight 261 Grease Sample Analysis Wear particle laden grease. Magnified wear particles. • Particles consistent with sliding wear (normal wear mode). • No evidence of corrosive wear or abrasive wear.

6. Could Switch to Aeroshell 33 Have Resulted in Accelerated Wear? Side by side, comparative testing of the two greases was performed under all pertinent conditions related to jackscrew operations.

7. Test Program Grease Testing Exposure Testing Wear Testing

8. Grease Testing Exposure Testing Wear Testing Performed by: NAVAIR Aerospace Materials Division

9. Standardized Grease Testing Mixtures Mobilgrease 28 Aeroshell 33 • Findings: • Mixing of Aeroshell 33 and Mobilgrease 28 did not significantly deteriorate their properties.

10. Grease Testing Exposure Testing Wear Testing • Performed by: • NAVAIR Aerospace Materials Division • Science Applications International Corporation (SAIC)

11. Exposure Testing Grease Types Contaminants Water De-icing fluid Anti-icing fluid Mobilgrease 28 Aeroshell 33 50/50 blend Aluminum Bronze 75º F 150º F 212º F 24 hours 2 weeks Temperatures Durations

12. Exposure Testing Test Specimen Exposed to grease Exposed to air • Findings: • Aeroshell 33 does not corrode aluminum bronze. • Staining caused by anti-wear additives (not harmful).

13. Grease Testing Exposure Testing Wear Testing • Performed by: • Rensselaer Polytechnic Institute • Battelle Memorial Institute

14. Force Stationary Block Grease Rotating Ring Block–on–Ring

15. Comparison of Block-on-Ring Characteristics to Actual J/S Operation • Materialssame (fabricated from actual parts) • Pressuresimilar (wide range) • Speedsimilar • Motionsimilar (sliding,reciprocating) • Contact Geometrysimilar (finite area)

16. Test Conditions of the Block-on-Ring Experiments • Low, Medium, High, and Very High Average Pressures • Neat greases and mixtures • Water, salt water, and de-icing fluid contamination • Aged grease with wear debris • Sub-freezing temperatures

17. Wear Rate of Aluminum Bronze Pure Greases Wear rate Factor (mm3/N·m) x 106

18. Wear Rate of Aluminum Bronze Pure Greases Severe wear (accident airplane) Wear rate Factor (mm3/N·m) x 106

19. Wear Rate of Aluminum Bronze Pure Greases Contaminated Greases Severe wear (accident airplane) Wear rate Factor (mm3/N·m) x 106

20. Wear Rate of Aluminum Bronze Used Grease Pure Greases Contaminated Greases Severe wear (accident airplane) Wear rate Factor (mm3/N·m) x 106

21. Wear Rate of Aluminum Bronze Used Grease Pure Greases Contaminated Greases –20° F Severe wear (accident airplane) Wear rate Factor (mm3/N·m) x 106

22. Wear Rate of Aluminum Bronze Used Grease Pure Greases Contaminated Greases –20° F Dry Severe wear (accident airplane) Wear rate Factor (mm3/N·m) x 106

23. Conclusions Regarding Severe Wear of Acme Nut • No evidence that the use of Aeroshell 33 would have caused accelerated wear. • The only factor that could explain the severe and accelerated wear is a lack of lubrication.