bdk wrote:
The fuel controls in jet engines are very sensitive to corrosion and having the seals dry out. With many jets you need to run (or at least motor) the engines every 30 days. This also keeps all the roller bearings wet with oil.
On the Mi-24, the "storage" protocol says that the engines need to be run every 30 days. I'd have to pull the books, but the manual is pretty detailed for how to preserve and de-preserve the aircraft and the specific procedure for running the engine and components (there is both a "ground" and a "hover" procedure specified).
Steve, as was said above, jet fuel can cause corrosion. In addition, all fuel has at least some water in it. As such, if you leave it in for a long time, the water will settle out and cause corrosion. Typically, you fill all tanks with light oil and then drain them to put a protective coat of oil on them. This is what I believe the automated system on the MiG does, but in the tried-and-true fashion of the Soviet system - with as little intervention as possible.
It goes back to something that Jon told me when I met him - the Soviets designed everything to be maintained by a farmer. If a farmer couldn't maintainer it, then it was simply setup in such a way that when it was time to work on it, it was removed from the aircraft and sent back to the factory or overhaul facility to be worked on. Thus all the "automation" like what you see with the start sequences on these aircraft. When all you have to do is "flip switch", you can have conscripted maintenance crews keep the aircraft in working order instead of the highly trained (and thus highly dangerous from a possible defection or spy point-of-view) crews that we're used to in "the West".
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