Lubricating grease can be defined as a solid to semi fluid product obtained by the dispersion of a gelling agent in a liquid lubricant. Greases are composed of either a mineral, vegetable or synthetic oil thickened with a metallic soap or clay and are used for lubrication of aircraft parts such as

• Moving parts of fuselage
• Hot zones of engine
• Parts in contact with fuel or oil
• Exposed parts for protection
• Wheel Bearings

The technical and performance requirements of greases arising out of these applications are not very much different for various types of aircraft, excluding the products required for any specialised equipment in the system.

Mineral oil thickened with calcium soap (commonly known as lime soap) constituted the first type of lubricating grease produced in commercial quantities. This was followed by sodium soap greases, but as sodium salts are soluble in water these greases tend to get washed out with the ingress of water in the system. This led to the development of water resistant barium and lithium soap types followed by complex thickeners of aluminum and calcium. For high temperature applications non-soap thickeners such as modified clays and other organic compounds like substituted ureas, polymers and pigments are used. For extremely high temperature performance, greases with inorganic fillers such as molybdenum disulphide and graphite were introduced. The base fluids can range from mineral oils, synthetic esters, synthesized hydrocarbons, silicone oils depending on the desired performance to even vegetable oils in cases where resistance to hydrocarbons (fuels and oils) is required. Chemical and oxygen resistant greases are also available for special applications.

For aircraft usage, several types of mineral oil based and synthetic greases are used, the latter offering wide temperature range performance. During recent years the number of greases required for fleet maintenance has been reduced due to the development of multipurpose greases as well as successful rationalisation attempts between greases of western and Russian origin. Some of the commonly used aircraft greases are:

• Aircraft Greases Western
• Aircraft Greases Russian
  
   

AIRCRAFT GREASES RUSSIAN
SPECIFICATION	DESIGNATION	BASE OIL	THICKENER	OPERATING CODE TEMPERATURE
GOST 6267-74	Ciatim 201	Mineral	Lithium	-40°C to +100°C
GOST 8773-73	Ciatim 203	Mineral	Lithium	-50°C to +90°C
GOST 9433-80	Ciatim 221	Synthetic	Calcium complex	-60°C to +150°C
TU 38 101 1051-87	VNII NP-261	Synthetic	Clay	-40°C to +150°C