Prop RPM and Engine Mixture

[Ben_M_K]

Hey there. I just got a yoke with three levers. One for throttle, one for Prop RPM, and one for Engine Mixture. The problem is, I dont really know how to use Prop RPM or Engine Mixture. So I was just wondering, what do they do? And does anyone have any tips on how to use them correctly?

Thanks,

Ben

[Eskimo]

The throttle lever is, obviously, for the throttle.

The Propellor RPM is a lever that is used in planes with CSUs (Constant Speed Units).  In FS tthese are the planes with the blue handle between te throttle and the mixture.  Don't ask me on the technicallities of CSUs but the groundschool section for the complex aircraft lessons has the basics on how to use it.

The mixture controles the ratio of fuel to air that is entering the engine.  Moving it up adds more fuel to the same amount of air, ie. the mixture is 'rich'.  Moving it down decreases the amount of furl mixed with air and the mixture becomes 'lean'.  Moving all the way down to ICO (Idle Cut-off) and there is no fuel getting to the engine so the engine stops.  Not good in the air.

To lean the engine correctly, you move the mixture level back until the eninge starts running roughly, then forward until it runs smooth, then slightly more forward.  This has to be done everytime you have an altitude or speed change.  And, of course, when landing or taking off, use the full rich position.

That's it, the VERY basics of prop RPM and mixture control.  I am good.

[Rocket_Bird]

The throttle pretty much controls your thrust, more throttle, more power!  

The prop RPM typically controls the pitch on your propeller.  Typically, all the way forward gives you a fine (minimum) pitch and all the way back gives you course.  The constant speed as mensioned by Eski controls the RPM by use of a governor at a selected operating RPM.  You adjust this depending on the relative wind on your propeller.  This in turn adjusts the angle of attack on your blade.  I believe making it courser gives you better effeciency at higher velocities.

The Engine mixture, once again, controls the amount of fuel and air.  At higher altitudes, you can lean your mixture a bit and it will help with your effeciency

[logjam]

The higher you are, the less oxygen is available for combustion. You can notice a difference, even in a car or motorcycle, as you climb higher up a mountain, the less efficient the engine becomes. Dare I say this: In the old days, we'd have to stop and re-set the needle jet on our Triumph Speed Twins at about 3000ft and so on if the road took you that high. Fortunately, aircraft engines have a variable mixture setting to equalise the gas/air mixture, so you don't have to climb out and do this.
Start to lean out at 3000ft and watch the cylinder head temperature, as if you have it too lean, the mixture will burn hot. If the mixture is too rich, then the carburettor will choke through lack of oxygen.
The Prop pitch control can be likened to a gear lever on a car. When you are climbing, the pitch needs to be finer and when cruising, you can use a courser setting. The optimum propeller RPM can be found in the Pilot's notes, but the mixture settings have to be determined by the local conditions, ie Barometric pressure(Altimeter) OAT and Humidity. Usually one can tell by the feel. Play with it at a safe height.

[Skligmund]

In reference to your prop control:

Your POH should give you performance charts for best economy and best power at 5,000 ft intervals (at least Piper does).

Example (since I have my Chieftain POH here with me):






These charts show you how to set up your engines for certain cruise performance. I only have the performance chart of 260HP shown, but there are more. By setting your RPM with your propeller control, and your manifold pressure with your throttle control, you will use X amount of fuel and fly Y fast. You can figure out range with these numbers.

If you set your prop lever to anything other than full foward, you will fly slower than not. You will save fuel however. When set at full foward, the props will adjust their angle of attack to hold redline rpm, so they still change angles.

[Ben_M_K]

Thanks guys!!!!!

[Springer6]

This page explains how constant speed props workhttp://www.avweb.com/news/maint/185020-1.html%20 %20 %20 %20