Quote:
Originally Posted by Geronimo989
Ok a quite simple and maybe stupid question: Does more RPM always mean more power on the 109, with the risk of breaking the engine when exceeding the limit? Or do you get maximum power when staying in certain RPM range (2500) and you actually LOSE power when you exceeding it?
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Absolutely not... However, power is dependent upon RPM. That is power is a "rate" of work being done.
Use the Prop Pitch control to regulate the
engine load by maintaining a certain RPM. At a high pitch, it's harder for the engine to swing it than at a lower pitch.
All internal combustion engines produce power on what's called a power curve, named because the relationship between torque output and RPM is not linear - it's a curve. Hard to describe but imagine an engine running at idle
may produce an increasing amount of torque at an increase of RPM (with a constant load) up to a
peak.
Then any additional RPM beyond that peak will start reducing the torque output, even though RPM's are increasing. (Side Note: In internal combustion engines, the power and torque numbers are equal at 5252 RPM)
A dynamometer, is used to measure the power parameters of an engine. The dynamometer operator will increase the throttle from idle to max throttle and measure the RPM and torque output.
Using a variable pitch prop [bf109] or fixed pitch prop [tiger moth], the propeller can represent the constant load (assuming you don't change the variable pitch) exerted on the engine, and taking the throttle from idle to max throttle will exercise the engine across it's power curve.
If the propeller is a constant speed propeller (spit) then the propeller will adjust its pitch (adjust its load) automatically to maintain a certain load. Since the engine produces power on a power curve, you can stick the RPM to the peak level and then worry about one less thing. As you increase throttle, the engine RPM will increase until there is enough power to swing that prop at the given setting. A constant speed prop makes it easy to keep the engine at the best RPM for a given situation, such as MAX performance, or MAX economy.
A variable pitch propeller the pilot must adjust the propeller pitch to do the same thing, as an increase in throttle will increase the RPM of the engine, unless the pilot increases the load on the engine.
A fixed pitch prop, the pilot must adjust the RPM's with the throttle.
Usually, aircraft manuals aren't published with detailed power curves, but what they do have is settings for varying scenarios. The CoD manuals have some values published, but I've seen more detailed tables in other game manuals (such as the shockwave A2A Bf109 manual - which you can view online)
Here is a nice web page that discusses power and torque.
http://www.epi-eng.com/piston_engine...and_torque.htm