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

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 Leading up to the time of the accident, Alaska Airlines used two brands of lubricating grease on its jackscrew assemblies: – Mobilgrease 28 –Aeroshell 33

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. 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.

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

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

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

Grease Testing Wear Testing Exposure Testing Test Program

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

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

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

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

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

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

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

1.Materialssame (fabricated from actual parts) 2.Pressuresimilar (wide range) 3.Speedsimilar 4.Motionsimilar (sliding, reciprocating) 5.Contact Geometrysimilar (finite area) 1.Materialssame (fabricated from actual parts) 2.Pressuresimilar (wide range) 3.Speedsimilar 4.Motionsimilar (sliding, reciprocating) 5.Contact Geometrysimilar (finite area) Comparison of Block-on-Ring Characteristics to Actual J/S Operation Comparison of Block-on-Ring Characteristics to Actual J/S Operation

Test Conditions of the Block-on-Ring Experiments 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 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

Pure Greases Wear rate Factor (mm 3 /N·m) x 10 6 Wear Rate of Aluminum Bronze

Pure Greases Wear rate Factor (mm 3 /N·m) x 10 6 Severe wear (accident airplane) Wear Rate of Aluminum Bronze

Pure Greases Wear rate Factor (mm 3 /N·m) x 10 6 Severe wear (accident airplane) Contaminated Greases Wear Rate of Aluminum Bronze

Pure Greases Wear rate Factor (mm 3 /N·m) x 10 6 Severe wear (accident airplane) Contaminated Greases Used Grease Wear Rate of Aluminum Bronze

Pure Greases Wear rate Factor (mm 3 /N·m) x 10 6 Severe wear (accident airplane) Contaminated Greases Used Grease –20° F Wear Rate of Aluminum Bronze

Pure Greases Wear rate Factor (mm 3 /N·m) x 10 6 Severe wear (accident airplane) Contaminated Greases Used Grease –20° FDry Wear Rate of Aluminum Bronze

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. Conclusions Regarding Severe Wear of Acme Nut Conclusions Regarding Severe Wear of Acme Nut