Aircraft Maintenance Technology

AUG-SEP 2018

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Page 12 of 67 13 Q. How long does grease actually last? Shelf life specifications can differ between aviation greases. Typically, aviation grease shelf life is listed as the “use by” date on the container. The average industry shelf life of aviation greases is about three years, however, ExxonMobil’s Mobilgrease™ 33 and Mobilgrease™ 28 aviation greases offer extended shelf life for up to 10 years. Q. Why can’t you use grease after its expiration date? While it’s dependent on the product’s history, it’s likely an expired grease has degraded. Using a grease past its expiration date also exposes a user to other risks associated with using an unapproved product. The shelf life of grease is really a measure of the useful life of the components in the grease to ensure it is still fit for use. As the product exceeds its shelf life, a decrease in the performance additives that provide wear protection, oxidation stability, and grease structural stability may be observed. As mentioned previously, to maximize shelf life, normal storage temperatures should range from 0 C to 40 C (32 F to 104 F), and containers should be kept indoors in a clean and dry environment. This helps avoid hydrolysis and other environmental factors that may impact the storage life of the product. Q. Why do some greases have a longer shelf life than others? While all aviation greases comply with the same specifications, they do differ in their formulations, chemistry, and performance properties. As a result, the shelf life can vary from one supply to the next. If the grease is not stored properly, it’s also more likely to accelerate deterioration before the expiration date and may no longer be used on an aircraft. Q. Can grease be recertified to extend the shelf life? Is there any risk? Although the FAA can approve recertification, the process involves lengthy and rigorous testing, which is conducted by the grease manufacturer. Applying a recertified grease is risk-free. The FAA would not reapprove or recertify a grease if there was an issue with the product. Coming up in AMT’s October issue, Part 2 will focus largely on grease compatibility, conversions, and contamination. From Testing to Precision Radome Repairs and Overhauls, We're Experts » Guaranteed same day TAT for transmissivity testing using our in-house anechoic chamber » Wide-ranging exchange and loaner inventory » In-house paint booth » Radome boot and installation » In-house tooling and jigging capabilities for full re-rings and overhauls Serving the business jet, regional and commercial aviation industries for two decades. 888.343.4225 EXCHANGE PROGRAM: Beechjet 400 Boeing 737, 757, 767 Bombardier CL601, CL604, CL850, CRJ 100/200, CRJ 700/900, Global Express, XRS, Global 5000, Lear 31, 35, 36, 45 Cessna Citation 525, 525A, 525B, 525C, 550, 560, 560XL, 650, 680/750, Mustang Dassault F20, F50, F200 Embraer E135/145, E175/E190 Gulfstream GII, GIII, GIV, G200 Hawker 800, 800XP, 850XP REPAIRS AND OVERHAULS: Beech King Air 200, 250, 300, 350, C90 Beechcraft Premier 390 Beechjet 400, 400A Boeing 767 Bombardier CRJ, Challenger, Global Cessna 510, 525, 550, 560, 560XL, 650, 750 Embraer 135, 145, 170, 175, 190 Gulfstream II, III, IV, V, 550 Hawker 750, 800, 900, XP Learjet 20 Series, 30 Series, 40, 45, XR, 55, 60 The Radome Authority for Testing, Repairs and Overhauls

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