Remember Me? Advanced Search. Results 1 to 9 of 9. Thread: Useful life of LL. Thread Tools Show Printable Version. Useful life of LL If a plane hasn't flown in several months, is there any concern about flying with fuel that's already in the tank? Aside from the obvious like water or critters in the sump, is there a time when an ounce of avgas burns at an unacceptably lower level of combustibility resulting in an unsafe condition such as dangerously low rate of climb etc.? Fuel in tank is about a year old; last flew in February, has taxi'd a time or two.
Still develops the normal range of max static RPM. I'm not sure about precipitation of solids, but it makes sense that over a long time in a non-hermetically-sealed tank, the lighter fractions will evaporate in preference to the heavier fractions, changing the composition somewhat. Geoffrey Thorpe , Mar 16, Mister Mystery Man , Mar 16, Cap'n Jack , Mar 16, What would be the degradation mechanism in a sealed container? It cannot be selective evaporation because the vapour has nowhere to go.
Once the vapour goes saturated for each gas constituent the evaporation must stop. Would the fuel need stirring up, to be sure? First, there is a large margin of safety in the one-year storage life of avgas. The main concern when storing fuels is oxidation and subsequent formation of gum. Once the fuel starts to form gum, it can cause problems in the entire fuel system. The samples will last even longer if the container is blanketed with nitrogen or stored in a colder climate.
The second point is that the one year shelf life applies to avgas and not auto gas. If a pilot is using auto gas, he should make a serious effort to use all of the fuel supply within six months of purchase. So if avgas is good for one year, how long can you store lubricants? The specifications generally state that the manufacturer must guarantee a product will meet physical property limits for at least three years.
There was a small amount of additive settling after 10 years, but the oil was still on spec. This is not a serious problem if your engine is running with a proper oil temperature and can evaporate the moisture on the first few flights. The mil spec for aviation greases calls for the manufacturer to guarantee that the product meets the limits for at least three years. This is for a product in a sealed container. The problem with grease is that much of it is used from an open-top container, which is generally open to the atmosphere.
Here the product is prone to absorb moisture. This can be a problem because many of the applications for these products do not get to a temperature high enough to boil off the moisture. This can lead to increased rust activity and decreased component life. Therefore, it is important to always smooth out the top surface of the grease to limit the surface area exposed to air. I also have found numerous containers that were not properly covered.
Many of these samples contained an excessive amount of dirt and foreign matter which could decrease component life. Greases should be stored in a dry place with the lids tightly sealed. Ben Visser is an aviation fuels and lubricants expert who spent 33 years with Shell Oil.
He has been a private pilot since General Aviation News reserves the right to delete snarky, offensive or off-topic comments. See our Comment Policy for more details. Avionics sales increased 5. Fixing the aviation industry isn't an easy task. But it needn't be difficult either. Similar to Avgas, there is the risk of gum formation due to oxidation from air. To control this, effect antioxidants — special chemical additives in carefully limited amounts — are used.
However, once all the antioxidant is used up, the fuel starts to degrade. Another factor for consideration when storing Jet fuel is that it does not like catalytic metals such as copper. These, even at parts per billion concentration, can cause the fuel to become unstable when flowing through high temperature sections in an aircraft fuel system. To ensure a long fuel life, brass and other catalytic metal alloys should not be used in Jet fuel storage tanks.
Microbial contamination is another risk with aviation fuel storage. If trace water is present in the storage tank microbes can grow at the fuel-water interface, feeding on the fuel and living in the water. Draining any water present in Jet fuel and Avgas storage tanks is crucial.
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