RPM/Manifold pressure doubt

[skkuda]

I was reading a 1 page brief document called "Constant speed propeller operation" and somewhere it says

- When increasing power, increase the rpm first and then the manifold pressure.

- When decreasing power, decrease the manifold pressure first, and then decrease the rpm

So the question is....Wich lever is he talking about when he says rpm or manifold pressure?  Should I Increase power (rpm  first with the throttle lever or with the Propeller pitch lever?) and viceversa Should I decrease power (Manifold pressure with throttle lever or Propeller pitch lever?)

Hope my english were good enough so everyone can understand my confussion.......

Another point.....this document refers to "constant speed propeller" so I can Imagine that this is applicable to my Lancair IV P right!?

[skypilot]

There are 3 levers/controls.

From left to right  Power or the throttle which relates to the manifold pressure and is never used to control the RPM. Get up to some altitude and change to power setting and watch the manifold pressure which a measure of the power, whilst leaving the pitch control alone and you will see the RPM will remain constant (within limits). That is because the mechanics of the constant speed prop are changing the pitch of the prop to maintain a constant RPM.

The next is the propeller pitch control which is used to control the RPM by changing the pitch of the prop blades thus changing the load on the engine and thus the RPM. Again get up to height and change the RPM/prop pitch; the manifold pressure will remain constant (within limits again) but the RPM changes by changing the pitch of the prop blades. There does come a point where the pitch control will have no effect on the RPM when at idle or very low power/manifold pressure

Then there is the mixture control to account for the fuel/air mixture with altitude.

On climb out set your climb power - power down, pitch down.  Increase power - pitch up, power up in that order.

Yes the Lancair is a Constant speed Unit/prop (CSU) aircraft.

[Ross Casey]

Hi Skkuda,

MP lever is commonly called throttle (usually black) & RPM is controlled by propeller lever (usually blue). Yes the Lancair has a "Constant Speed Prop" Sometimes referred to a CSU (Constant Speed Unit).

Hope this helps.

[alan2]

The way I look at the logic is -  To increase or decrease with minimal strees on engine . A fully coarse prop at max revs is a hell of a load on engine and prop , so...as you say here....

When increasing power, increase the rpm first and then the manifold pressure.......can you imagine the power neede to spin up the revs with a coarse pitch prop . If you start fine / small angle it would be more aerodynamic and easier to hit the higher revs

- When decreasing power, decrease the manifold pressure first, and then decrease the rpm........same again, less stress . If you are decreasing the rpm you increasing the prop angle of attack and therefore drag and stress . So why not not take the power off first then alter the prop pitch

[skkuda]

...throttle which relates to the manifold pressure and is never used to control the RPM.

...the propeller pitch control which is used to control the RPM

Thats what I was looking for at first.....

Well..........now I need to Jump in the Lancair a review these concepts.....Thanks to everyone.

When another doubt assaults me I will come back here to ask!