Fewer Greases = Savings and Safety


To help airlines slash the number of greases they use, an inter-industry committee has finished developing a standard for general purpose airframe greases.

Now the group has begun drafting another specification for aviation wheel-bearing greases.

The standards are the work of SAE Internationals AMS-M Committee on Aerospace Greases – a panel that includes representatives of grease suppliers and aircraft manufacturers. The committee balloted the airframe grease specification three months ago and has since reviewed comments and made final edits. The final draft is now being reviewed by SAE and should be approved early next year, according to committee Chairman Geoff Bishop, of Shell Aviation Ltd. in London.

The standard, which will be assigned a number upon adoption, was based on a spec previously developed by Boeing, BMS3-33. Committee members say it should counteract the proliferation of airframe lubes prescribed for planes and other aircraft – a trend that has resulted in service manuals calling for dozens of products to be used on some commercial planes.

To demonstrate the benefits of the proposed standard, Boeing told the committee it will allow operators to use a single grease on all but nine of the 359 lubrication points on Boeing 737s.

Clearly this will simplify things for maintenance crews, and it should yield a cost savings for airlines by reducing the number of products they need to inventory, Bishop said. There is also a safety issue, because there is less possibility for misapplication if they are dealing with a smaller number of greases.

The proposed specification favors lithium complex formulations over clay greases, reinforcing a shift already underway in the market. Bishop said the committee is encouraged that the standard is already being used by Boeing and Airbus, the two primary manufacturers of commercial aircraft.

The effort to develop standards for aviation greases was launched by the European Lubricating Grease Institute and later turned over to SAE. It gained impetus after the January 2000 crash of an Alaska Airlines flight off the California coast raised concerns that mixing two greases in a lube point could cause lubricant degradation, even if both were approved for that application. The U.S. National Transportation Safety Board ultimately blamed the crash – which killed 88 people – on the airlines failure to apply enough grease to part of a mechanism controlling the planes vertical pitch.

Bishop said the AMS-M Committee hopes it does not take as long to develop the specification for wheel bearing greases, although he added that two years is a likely time-frame. The group already has a good start on a document that would incorporate new test methods, including one for water tolerance. Bishop said it also favors lithium complex formulations.

The committee currently has no representatives from bearing manufacturers and would welcome input from that industry.

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