Lu,
Boeing are already looking at the Royco grease, but as to discontinuing the use of Royco 11MS, we maintenance people have our hands tied. We must use the recommended lubricants and are not free to switch on our own authority. Frequent greasing following the generally accepted method of pumping in fresh grease until only fresh grease comes out of the joint ought to flush out any decomposing grease. Also, the greasing interval is now reduced to 1A Check (generally 500-600 hours or about 130 cycles) to ensure constant change of the grease in the joint. An important factor in all this, is that not all operators are affected. There are high time/high cycle aircraft with no sign of trouble and comparatively low time aircraft with severe problems. The difficulty lies in isolating the operating conditions that are common to all those aircraft that exhibit excessive wear on the pin. In the case of worn pins there are definite signs of heat damage, which of course contributes to break down of the grease. Selected operators are flying with a new design in the right gear and the old original pins in the left. All pins are removed for inspection during "C" check, and the results reported back to Seattle. As the database develops, the final fix will become clearer.
There is a theory that operation on certain runways leads to a particular vibration frequency, which in turn causes heating of the pivot pin/bushing. The subsequent break down of the grease then causes corrosion and eventual cracking of the pivot pins. In this case, it makes little difference which grease is used, any type will eventually decompose and result in pin failure.
And to think we've only just fixed the problem of vibrating carbon brakes shaking the gears to pieces. Now this bit of achemy - ain't engineering wonderful?...
**********************************. .Through difficulties to the cinema