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Things had started to go wrong as we reached our operational height for the mission. When we flew at that height, the engine only just gave enough pull and we constatnly changed propeller pitch and RPM to improve performance.
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At high altitudes, the airplane is essentially in slow flight for most of the envelope. That makes cooling harder and overboost conditions will heat the motor up faster.
If they wanted to use a limited overboost condition, they would be constantly changing rpm between maximum continious and higher limited overboost to cool the motor.
Not the same thing as maintaining constant rpm at the overboost condition to realize the speed gain. In otherwords, when you set the engine to say, 1.35ata @ 2400U/min, you will adjust pitch to maintain a
constant 2400U/min rpm to achieve best performance.
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Ulrich Steinhilper, in his auto-biography (chapter 16) , talks about managing the prop-pitch on the early (E3 and E4 variant) 109s during the Battle of Britain. He states that, in order to achieve max climb rate and airspeed (particularly at higher altitudes) one had to constantly increase and decrease the propeller pitch.
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You must change pitch, rpm, or airspeed. If you increase rpm and airspeed, you must coarsen the pitch to keep rpm steady and airspeed increasing.....
That is how it works.
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With a flat pitch we could increase the rpm of the engine and get more pressure from the supercharger.
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Same as a CSP. Reduce pitch to increase rpm and then coarsen the pitch as the speed increases to take advantage of the new rpm setting.
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With a flat pitch we could increase the rpm of the engine and get more pressure from the supercharger. Then, by changing the piitch to a coarser setting, we could make up some speed.
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Same as it ever was and what I have repeated for several pages....
RPM stays constant....
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Increasing the pitch would engage the supercharger, which would be run for a short period (i.e. a second or less?) to force more air into the cylinders, then the pitch would be dropped back down again to disengage the supercharger and convert the power gained into airspeed, and allowing the engine/ supercharger to rest.
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They overloaded the super by increasing rpm at high altitude, the engine will have a cooling problem in a short time period.
A complete sidetrack as to how they are using the propeller and rpm to gain speed.