Some pretty good points all around and a very balanced analysis from Crumpp which i mostly agree with, except the propaganda part (i wouldn't call a simplified school assignment meant for 10 year old children that).
On another note:
Quote:
Originally Posted by kimosabi
They even started mixing small amounts of fuel in the engine oil to get the performance from the engines needed for a scramble from cold starts. Figured that should save them some drops.
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This is not about fuel economy, it's for making the engine easier to start. When the oil is cold it's more viscous and needs more torque for the engine to fire, placing a strain on the starter motors and/or battery supply in case of failed starts and subsequent retries, not to mention having to wait longer until it warms up because otherwise the oil pressure is too much, pipes burst and oil leaks develop.
By mixing fuel the oil can be diluted and that lowers its viscosity, making the engine easier to start. Eventually, the fuel in the oil gradually burns and/or evaporates and things are back to normal.
The way i read the whole thing is that since they couldn't afford fuel for hourly warm-ups to maintain the engines in a "ready to run" condition, they started using the next best alternative method.
Many aircraft (especially the USAF ones and probably most of them) later in the war had oil dilution switches just for that purpose, so the engineers wouldn't have to manually mix fuel into the oil reservoir. If a pilot expected cold weather during his next start-up and take off or if the plane was to be left with the engine off for a longer period of time, the pilot would set the oil dilution switches to on after landing and keep the engine running for a few minutes before shutting down.
This ensured that on the next start-up, oil would be pre-mixed with fuel and the engine would be easier to start.
06-18-2011, 06:17 PM
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