I have moved from the Cessna’s to try a couple of constant speed prop planes (twin engine purchased from the marketplace) I have watched many youtube videos on manifold pressure, the prop angle, how to move the leavers etc. I have the manuals supplied with the purchases that detail how to set the plane for climb, cruise etc. which all makes sense and I can do that.
However, I have failed to find simple information on what should be done if I just want to accelerate or more likely slow down. Do I just move the throttle ? just the prop? both a bit? with prop full forward for landing I assume this is slower, so do I just push the prop forwards as far as it goes, then start pulling the power back to slow down in flight?
Power is related to both MP and RPM; therefore power increase either accelerate or climb and decrease power either decelerate or descend depending on pitch attitude.
You don’t just change RPM to change power, it is much more common to change MP. If you want to slow down simply reduce MP.
Be sure you move the levers in the correct order. Increase RPM before increasing MP and decrease MP before decreasing RPM. In general, stick to the power tables in your pilot handbook.
Snide Spoke,
Generally speaking, think of using Manifold Pressure (MP) to control the amount of power/thrust you want from the engine, while using the prop control to “fine tune” the blade angel/rpm for best efficiency, based on the phase of flight you are in.
As a general rule, you want the prop full forward/max RPM for ground ops & takeoff. With most airplanes you reduce both power (MP) and RPM at 500 to 1000 ft AGL after takeoff. With most airplanes, you “square it off” - meaning you pull power and then manifold pressure back to 25"/2500 RPM for the climb. (But different engines have different procedures - for example, the Beechcraft products have you reduce the RPM to 2500, but leave the throttle/MP at full throttle. Supposedly leaving the power up helps keep the engine cool by keeping fuel flowing at a higher rate on those engines.)
At cruise, you generally set your MP to whatever gives you your desired cruise power - typically 75% on most airplanes (and you have to go to the performance charts for the aircraft to see what the MP setting should be - it varies by aircraft and altitude/temperature - and you can set it lower than 75% to improve range/fuel effeciency,) and set the prop so it is at its most efficient setting for that power setting - typically between 2300 and 2500 RPM for most planes (but again, you need to look at the charts to see what it is for your specific aircraft at that altitude and power setting.) If you just want a ballpark setting for cruise that will work for most airplanes, I’d say 24" MP and 2400 RPM would work out.
You leave it like that until you are on approach, then you want to bring the propeller back to full forward/Max RPM as part of your before landing checklist, so you have max thrust available in the event of a go around.