richard.goode(at)russiana
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 Posted: Mon Apr 27, 2009 7:55 am Post subject: More on oil consumption |
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To shed a bit more light on this issue:
- The main reason for high oil consumption on these engines is the use of old dated-technology aluminium in the pistons, which has a very high rate of thermal expansion.
- This means that when cold, the pistons have an extremely lose fit in the bores, and a great deal of oil is lost during start-up (would you expect to see that cloud of smoke from your car when you start-up?).
- Even in the cruise, there is still quite a lot of "slop" at normal operating temperatures, to give the pistons room to expand yet further when the engine gets very hot.
- Another reason is, again, old-technology piston rings. I am no expert in these areas, but I know that oil consumption can be dramatically improved by the use of better rings.
- It might seem obvious, but so many people discuss oil consumption during aerobatics.
- Although the Russians have a very good inverted oil system, it inevitably "breaths" a bit of oil, which is then lost. So no accurate oil consumption of an engine itself can ever be determined through an aerobatic flight.
- The only way to get an accurate oil consumption - by implication the condition of the engine - is to warm it up; fully scavenge all oil out of the engine by running for 20 seconds at a minimum of 60 percent; shut down and check oil level; fly for a minim of 45 minutes - ideally more; land and re-measure.
- The figure of 3 litres (effective 3 quarts) per hour from Vedeneyev is the official maximum acceptable.
- I suspect however that they introduce this simply to cover their backsides in terms of warranty claims. Of course it is ridiculous in that, with a 6 hour endurance in a Sukhoi, you would run of oil long before fuel, if using that much oil!
Richard Goode Aerobatics
Rhodds Farm
Lyonshall
Herefordshire
HR5 3LW
United Kingdom
Tel: +44 (0) 1544 340 120
Fax: +44 (0) 1544 340 129
www.russianaeros.com
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